gcc(1) 맨 페이지 - 윈디하나의 솔라나라

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gcc(1)

Name
     gcc - GNU project C and C++ compiler

Synopsis
     gcc [-c|-S|-E] [-std=standard]
         [-g] [-pg] [-Olevel]
         [-Wwarn...] [-Wpedantic]
         [-Idir...] [-Ldir...]
         [-Dmacro[=defn]...] [-Umacro]
         [-foption...] [-mmachine-option...]
         [-o outfile] [@file] infile...

     Only the most useful options are listed here; see below for
     the remainder.  g++ accepts mostly the same options as gcc.

Description
     When you invoke GCC, it normally does preprocessing,
     compilation, assembly and linking.  The "overall options"
     allow you to stop this process at an intermediate stage.
     For example, the -c option says not to run the linker.  Then
     the output consists of object files output by the assembler.

     Other options are passed on to one stage of processing.
     Some options control the preprocessor and others the
     compiler itself.  Yet other options control the assembler
     and linker; most of these are not documented here, since you
     rarely need to use any of them.

     Most of the command-line options that you can use with GCC
     are useful for C programs; when an option is only useful
     with another language (usually C++), the explanation says so
     explicitly.  If the description for a particular option does
     not mention a source language, you can use that option with
     all supported languages.

     The gcc program accepts options and file names as operands.
     Many options have multi-letter names; therefore multiple
     single-letter options may not be grouped: -dv is very
     different from -d -v.

     You can mix options and other arguments.  For the most part,
     the order you use doesn't matter.  Order does matter when
     you use several options of the same kind; for example, if
     you specify -L more than once, the directories are searched
     in the order specified.  Also, the placement of the -l
     option is significant.

     Many options have long names starting with -f or with
     -W---for example, -fmove-loop-invariants, -Wformat and so
     on.  Most of these have both positive and negative forms;
     the negative form of -ffoo is -fno-foo.  This manual
     documents only one of these two forms, whichever one is not
     the default.

Options
  Option Summary
     Here is a summary of all the options, grouped by type.
     Explanations are in the following sections.

     Overall Options
         -c  -S  -E  -o file  -no-canonical-prefixes -pipe
         -pass-exit-codes -x language  -v  -###
         --help[=class[,...]]  --target-help --version -wrapper
         @file -fplugin=file -fplugin-arg-name=arg
         -fdump-ada-spec[-slim] -fada-spec-parent=arg
         -fdump-go-spec=file

     C Language Options
         -ansi  -std=standard  -fgnu89-inline -aux-info filename
         -fallow-parameterless-variadic-functions -fno-asm
         -fno-builtin  -fno-builtin-function -fhosted
         -ffreestanding -fopenmp -fms-extensions
         -fplan9-extensions -trigraphs  -traditional
         -traditional-cpp -fallow-single-precision
         -fcond-mismatch -flax-vector-conversions
         -fsigned-bitfields  -fsigned-char -funsigned-bitfields
         -funsigned-char

     C++ Language Options
         -fabi-version=n  -fno-access-control  -fcheck-new
         -fconstexpr-depth=n  -ffriend-injection
         -fno-elide-constructors -fno-enforce-eh-specs
         -ffor-scope  -fno-for-scope  -fno-gnu-keywords
         -fno-implicit-templates -fno-implicit-inline-templates
         -fno-implement-inlines  -fms-extensions
         -fno-nonansi-builtins  -fnothrow-opt
         -fno-operator-names -fno-optional-diags  -fpermissive
         -fno-pretty-templates -frepo  -fno-rtti  -fstats
         -ftemplate-backtrace-limit=n -ftemplate-depth=n
         -fno-threadsafe-statics -fuse-cxa-atexit  -fno-weak
         -nostdinc++ -fno-default-inline
         -fvisibility-inlines-hidden -fvisibility-ms-compat
         -fext-numeric-literals -Wabi  -Wconversion-null
         -Wctor-dtor-privacy -Wdelete-non-virtual-dtor
         -Wliteral-suffix -Wnarrowing -Wnoexcept
         -Wnon-virtual-dtor  -Wreorder -Weffc++
         -Wstrict-null-sentinel -Wno-non-template-friend
         -Wold-style-cast -Woverloaded-virtual
         -Wno-pmf-conversions -Wsign-promo

     Objective-C and Objective-C++ Language Options
         -fconstant-string-class=class-name -fgnu-runtime
         -fnext-runtime -fno-nil-receivers -fobjc-abi-version=n
         -fobjc-call-cxx-cdtors -fobjc-direct-dispatch
         -fobjc-exceptions -fobjc-gc -fobjc-nilcheck
         -fobjc-std=objc1 -freplace-objc-classes -fzero-link
         -gen-decls -Wassign-intercept -Wno-protocol  -Wselector
         -Wstrict-selector-match -Wundeclared-selector

     Language Independent Options
         -fmessage-length=n
         -fdiagnostics-show-location=[once|every-line]
         -fno-diagnostics-show-option -fno-diagnostics-show-caret

     Warning Options
         -fsyntax-only  -fmax-errors=n  -Wpedantic
         -pedantic-errors -w  -Wextra  -Wall  -Waddress
         -Waggregate-return -Waggressive-loop-optimizations
         -Warray-bounds -Wno-attributes
         -Wno-builtin-macro-redefined -Wc++-compat -Wc++11-compat
         -Wcast-align  -Wcast-qual -Wchar-subscripts -Wclobbered
         -Wcomment -Wconversion  -Wcoverage-mismatch  -Wno-cpp
         -Wno-deprecated -Wno-deprecated-declarations
         -Wdisabled-optimization -Wno-div-by-zero
         -Wdouble-promotion -Wempty-body  -Wenum-compare
         -Wno-endif-labels -Werror  -Werror=* -Wfatal-errors
         -Wfloat-equal  -Wformat  -Wformat=2
         -Wno-format-contains-nul -Wno-format-extra-args
         -Wformat-nonliteral -Wformat-security  -Wformat-y2k
         -Wframe-larger-than=len -Wno-free-nonheap-object
         -Wjump-misses-init -Wignored-qualifiers -Wimplicit
         -Wimplicit-function-declaration  -Wimplicit-int
         -Winit-self  -Winline -Wmaybe-uninitialized
         -Wno-int-to-pointer-cast -Wno-invalid-offsetof
         -Winvalid-pch -Wlarger-than=len
         -Wunsafe-loop-optimizations -Wlogical-op -Wlong-long
         -Wmain -Wmaybe-uninitialized -Wmissing-braces
         -Wmissing-field-initializers -Wmissing-include-dirs
         -Wno-mudflap -Wno-multichar  -Wnonnull  -Wno-overflow
         -Woverlength-strings  -Wpacked  -Wpacked-bitfield-compat
         -Wpadded -Wparentheses  -Wpedantic-ms-format
         -Wno-pedantic-ms-format -Wpointer-arith
         -Wno-pointer-to-int-cast -Wredundant-decls
         -Wno-return-local-addr -Wreturn-type  -Wsequence-point
         -Wshadow -Wsign-compare  -Wsign-conversion
         -Wsizeof-pointer-memaccess -Wstack-protector
         -Wstack-usage=len -Wstrict-aliasing -Wstrict-aliasing=n
         -Wstrict-overflow -Wstrict-overflow=n
         -Wsuggest-attribute=[pure|const|noreturn|format]
         -Wmissing-format-attribute -Wswitch  -Wswitch-default
         -Wswitch-enum -Wsync-nand -Wsystem-headers
         -Wtrampolines  -Wtrigraphs  -Wtype-limits  -Wundef
         -Wuninitialized  -Wunknown-pragmas  -Wno-pragmas
         -Wunsuffixed-float-constants  -Wunused
         -Wunused-function -Wunused-label
         -Wunused-local-typedefs -Wunused-parameter
         -Wno-unused-result -Wunused-value  -Wunused-variable
         -Wunused-but-set-parameter -Wunused-but-set-variable
         -Wuseless-cast -Wvariadic-macros
         -Wvector-operation-performance -Wvla
         -Wvolatile-register-var  -Wwrite-strings
         -Wzero-as-null-pointer-constant

     C and Objective-C-only Warning Options
         -Wbad-function-cast  -Wmissing-declarations
         -Wmissing-parameter-type  -Wmissing-prototypes
         -Wnested-externs -Wold-style-declaration
         -Wold-style-definition -Wstrict-prototypes
         -Wtraditional  -Wtraditional-conversion
         -Wdeclaration-after-statement -Wpointer-sign

     Debugging Options
         -dletters  -dumpspecs  -dumpmachine  -dumpversion
         -fsanitize=style -fdbg-cnt-list -fdbg-cnt=counter-
         value-list -fdisable-ipa-pass_name
         -fdisable-rtl-pass_name -fdisable-rtl-pass-name=range-
         list -fdisable-tree-pass_name -fdisable-tree-pass-
         name=range-list -fdump-noaddr -fdump-unnumbered
         -fdump-unnumbered-links -fdump-translation-unit[-n]
         -fdump-class-hierarchy[-n] -fdump-ipa-all
         -fdump-ipa-cgraph -fdump-ipa-inline -fdump-passes
         -fdump-statistics -fdump-tree-all
         -fdump-tree-original[-n] -fdump-tree-optimized[-n]
         -fdump-tree-cfg -fdump-tree-alias -fdump-tree-ch
         -fdump-tree-ssa[-n] -fdump-tree-pre[-n]
         -fdump-tree-ccp[-n] -fdump-tree-dce[-n]
         -fdump-tree-gimple[-raw] -fdump-tree-mudflap[-n]
         -fdump-tree-dom[-n] -fdump-tree-dse[-n]
         -fdump-tree-phiprop[-n] -fdump-tree-phiopt[-n]
         -fdump-tree-forwprop[-n] -fdump-tree-copyrename[-n]
         -fdump-tree-nrv -fdump-tree-vect -fdump-tree-sink
         -fdump-tree-sra[-n] -fdump-tree-forwprop[-n]
         -fdump-tree-fre[-n] -fdump-tree-vrp[-n]
         -ftree-vectorizer-verbose=n -fdump-tree-storeccp[-n]
         -fdump-final-insns=file -fcompare-debug[=opts]
         -fcompare-debug-second -feliminate-dwarf2-dups
         -fno-eliminate-unused-debug-types
         -feliminate-unused-debug-symbols
         -femit-class-debug-always -fenable-kind-pass
         -fenable-kind-pass=range-list -fdebug-types-section
         -fmem-report-wpa -fmem-report -fpre-ipa-mem-report
         -fpost-ipa-mem-report -fprofile-arcs -fopt-info
         -fopt-info-options[=file] -frandom-seed=string
         -fsched-verbose=n -fsel-sched-verbose
         -fsel-sched-dump-cfg -fsel-sched-pipelining-verbose
         -fstack-usage  -ftest-coverage  -ftime-report
         -fvar-tracking -fvar-tracking-assignments
         -fvar-tracking-assignments-toggle -g  -glevel  -gtoggle
         -gcoff  -gdwarf-version -ggdb  -grecord-gcc-switches
         -gno-record-gcc-switches -gstabs  -gstabs+
         -gstrict-dwarf  -gno-strict-dwarf -gvms  -gxcoff
         -gxcoff+ -fno-merge-debug-strings -fno-dwarf2-cfi-asm
         -fdebug-prefix-map=old=new -femit-struct-debug-baseonly
         -femit-struct-debug-reduced
         -femit-struct-debug-detailed[=spec-list] -p  -pg
         -print-file-name=library  -print-libgcc-file-name
         -print-multi-directory  -print-multi-lib
         -print-multi-os-directory -print-prog-name=program
         -print-search-dirs  -Q -print-sysroot
         -print-sysroot-headers-suffix -save-temps
         -save-temps=cwd -save-temps=obj -time[=file]

     Optimization Options
         -faggressive-loop-optimizations -falign-functions[=n]
         -falign-jumps[=n] -falign-labels[=n] -falign-loops[=n]
         -fassociative-math -fauto-inc-dec -fbranch-probabilities
         -fbranch-target-load-optimize
         -fbranch-target-load-optimize2 -fbtr-bb-exclusive
         -fcaller-saves -fcheck-data-deps
         -fcombine-stack-adjustments -fconserve-stack
         -fcompare-elim -fcprop-registers -fcrossjumping
         -fcse-follow-jumps -fcse-skip-blocks -fcx-fortran-rules
         -fcx-limited-range -fdata-sections -fdce
         -fdelayed-branch -fdelete-null-pointer-checks
         -fdevirtualize -fdse -fearly-inlining -fipa-sra
         -fexpensive-optimizations -ffat-lto-objects -ffast-math
         -ffinite-math-only -ffloat-store
         -fexcess-precision=style -fforward-propagate
         -ffp-contract=style -ffunction-sections -fgcse
         -fgcse-after-reload -fgcse-las -fgcse-lm
         -fgraphite-identity -fgcse-sm -fhoist-adjacent-loads
         -fif-conversion -fif-conversion2 -findirect-inlining
         -finline-functions -finline-functions-called-once
         -finline-limit=n -finline-small-functions -fipa-cp
         -fipa-cp-clone -fipa-pta -fipa-profile -fipa-pure-const
         -fipa-reference -fira-algorithm=algorithm
         -fira-region=region -fira-hoist-pressure
         -fira-loop-pressure -fno-ira-share-save-slots
         -fno-ira-share-spill-slots -fira-verbose=n -fivopts
         -fkeep-inline-functions -fkeep-static-consts
         -floop-block -floop-interchange -floop-strip-mine
         -floop-nest-optimize -floop-parallelize-all -flto
         -flto-compression-level -flto-partition=alg -flto-report
         -fmerge-all-constants -fmerge-constants -fmodulo-sched
         -fmodulo-sched-allow-regmoves -fmove-loop-invariants
         fmudflap -fmudflapir -fmudflapth -fno-branch-count-reg
         -fno-default-inline -fno-defer-pop -fno-function-cse
         -fno-guess-branch-probability -fno-inline
         -fno-math-errno -fno-peephole -fno-peephole2
         -fno-sched-interblock -fno-sched-spec -fno-signed-zeros
         -fno-toplevel-reorder -fno-trapping-math
         -fno-zero-initialized-in-bss -fomit-frame-pointer
         -foptimize-register-move -foptimize-sibling-calls
         -fpartial-inlining -fpeel-loops -fpredictive-commoning
         -fprefetch-loop-arrays -fprofile-report
         -fprofile-correction -fprofile-dir=path
         -fprofile-generate -fprofile-generate=path -fprofile-use
         -fprofile-use=path -fprofile-values -freciprocal-math
         -free -fregmove -frename-registers -freorder-blocks
         -freorder-blocks-and-partition -freorder-functions
         -frerun-cse-after-loop
         -freschedule-modulo-scheduled-loops -frounding-math
         -fsched2-use-superblocks -fsched-pressure
         -fsched-spec-load -fsched-spec-load-dangerous
         -fsched-stalled-insns-dep[=n] -fsched-stalled-insns[=n]
         -fsched-group-heuristic -fsched-critical-path-heuristic
         -fsched-spec-insn-heuristic -fsched-rank-heuristic
         -fsched-last-insn-heuristic -fsched-dep-count-heuristic
         -fschedule-insns -fschedule-insns2 -fsection-anchors
         -fselective-scheduling -fselective-scheduling2
         -fsel-sched-pipelining
         -fsel-sched-pipelining-outer-loops -fshrink-wrap
         -fsignaling-nans -fsingle-precision-constant
         -fsplit-ivs-in-unroller -fsplit-wide-types
         -fstack-protector -fstack-protector-all
         -fstrict-aliasing -fstrict-overflow -fthread-jumps
         -ftracer -ftree-bit-ccp -ftree-builtin-call-dce
         -ftree-ccp -ftree-ch -ftree-coalesce-inline-vars
         -ftree-coalesce-vars -ftree-copy-prop -ftree-copyrename
         -ftree-dce -ftree-dominator-opts -ftree-dse
         -ftree-forwprop -ftree-fre -ftree-loop-if-convert
         -ftree-loop-if-convert-stores -ftree-loop-im
         -ftree-phiprop -ftree-loop-distribution
         -ftree-loop-distribute-patterns -ftree-loop-ivcanon
         -ftree-loop-linear -ftree-loop-optimize
         -ftree-parallelize-loops=n -ftree-pre -ftree-partial-pre
         -ftree-pta -ftree-reassoc -ftree-sink -ftree-slsr
         -ftree-sra -ftree-switch-conversion -ftree-tail-merge
         -ftree-ter -ftree-vect-loop-version -ftree-vectorize
         -ftree-vrp -funit-at-a-time -funroll-all-loops
         -funroll-loops -funsafe-loop-optimizations
         -funsafe-math-optimizations -funswitch-loops
         -fvariable-expansion-in-unroller -fvect-cost-model -fvpt
         -fweb -fwhole-program -fwpa -fuse-ld=linker
         -fuse-linker-plugin --param name=value -O  -O0  -O1  -O2
         -O3  -Os -Ofast -Og

     Preprocessor Options
         -Aquestion=answer -A-question[=answer] -C  -dD  -dI  -dM
         -dN -Dmacro[=defn]  -E  -H -idirafter dir -include file
         -imacros file -iprefix file  -iwithprefix dir
         -iwithprefixbefore dir  -isystem dir -imultilib dir
         -isysroot dir -M  -MM  -MF  -MG  -MP  -MQ  -MT
         -nostdinc -P  -fdebug-cpp -ftrack-macro-expansion
         -fworking-directory -remap -trigraphs  -undef  -Umacro
         -Wp,option -Xpreprocessor option -no-integrated-cpp

     Assembler Option
         -Wa,option  -Xassembler option

     Linker Options
         object-file-name  -llibrary -nostartfiles
         -nodefaultlibs  -nostdlib -pie -rdynamic -s  -static
         -static-libgcc -static-libstdc++ -static-libasan
         -static-libtsan -shared -shared-libgcc  -symbolic -T
         script  -Wl,option  -Xlinker option -u symbol

     Directory Options
         -Bprefix -Idir -iplugindir=dir -iquotedir -Ldir
         -specs=file -I- --sysroot=dir --no-sysroot-suffix

     Machine Dependent Options
         AArch64 Options -mbig-endian  -mlittle-endian
         -mgeneral-regs-only -mcmodel=tiny  -mcmodel=small
         -mcmodel=large -mstrict-align -momit-leaf-frame-pointer
         -mno-omit-leaf-frame-pointer -mtls-dialect=desc
         -mtls-dialect=traditional -march=name  -mcpu=name
         -mtune=name

         Adapteva Epiphany Options -mhalf-reg-file
         -mprefer-short-insn-regs -mbranch-cost=num -mcmove
         -mnops=num -msoft-cmpsf -msplit-lohi -mpost-inc
         -mpost-modify -mstack-offset=num -mround-nearest
         -mlong-calls -mshort-calls -msmall16 -mfp-mode=mode
         -mvect-double -max-vect-align=num -msplit-vecmove-early
         -m1reg-reg

         ARM Options -mapcs-frame  -mno-apcs-frame -mabi=name
         -mapcs-stack-check  -mno-apcs-stack-check -mapcs-float
         -mno-apcs-float -mapcs-reentrant  -mno-apcs-reentrant
         -msched-prolog  -mno-sched-prolog -mlittle-endian
         -mbig-endian  -mwords-little-endian -mfloat-abi=name
         -mfp16-format=name -mthumb-interwork
         -mno-thumb-interwork -mcpu=name  -march=name  -mfpu=name
         -mstructure-size-boundary=n -mabort-on-noreturn
         -mlong-calls  -mno-long-calls -msingle-pic-base
         -mno-single-pic-base -mpic-register=reg
         -mnop-fun-dllimport -mpoke-function-name -mthumb  -marm
         -mtpcs-frame  -mtpcs-leaf-frame
         -mcaller-super-interworking  -mcallee-super-interworking
         -mtp=name -mtls-dialect=dialect -mword-relocations
         -mfix-cortex-m3-ldrd -munaligned-access

         AVR Options -mmcu=mcu -maccumulate-args
         -mbranch-cost=cost -mcall-prologues -mint8
         -mno-interrupts -mrelax -mstrict-X -mtiny-stack
         -Waddr-space-convert

         Blackfin Options -mcpu=cpu[-sirevision] -msim
         -momit-leaf-frame-pointer  -mno-omit-leaf-frame-pointer
         -mspecld-anomaly  -mno-specld-anomaly  -mcsync-anomaly
         -mno-csync-anomaly -mlow-64k -mno-low64k
         -mstack-check-l1  -mid-shared-library
         -mno-id-shared-library  -mshared-library-id=n
         -mleaf-id-shared-library  -mno-leaf-id-shared-library
         -msep-data  -mno-sep-data  -mlong-calls  -mno-long-calls
         -mfast-fp -minline-plt -mmulticore  -mcorea  -mcoreb
         -msdram -micplb

         C6X Options -mbig-endian  -mlittle-endian -march=cpu
         -msim -msdata=sdata-type

         CRIS Options -mcpu=cpu  -march=cpu  -mtune=cpu
         -mmax-stack-frame=n  -melinux-stacksize=n -metrax4
         -metrax100  -mpdebug  -mcc-init  -mno-side-effects
         -mstack-align  -mdata-align  -mconst-align -m32-bit
         -m16-bit  -m8-bit  -mno-prologue-epilogue  -mno-gotplt
         -melf  -maout  -melinux  -mlinux  -sim  -sim2
         -mmul-bug-workaround  -mno-mul-bug-workaround

         CR16 Options -mmac -mcr16cplus -mcr16c -msim -mint32
         -mbit-ops -mdata-model=model

         Darwin Options -all_load  -allowable_client  -arch
         -arch_errors_fatal -arch_only  -bind_at_load  -bundle
         -bundle_loader -client_name  -compatibility_version
         -current_version -dead_strip -dependency-file
         -dylib_file  -dylinker_install_name -dynamic
         -dynamiclib  -exported_symbols_list -filelist
         -flat_namespace  -force_cpusubtype_ALL
         -force_flat_namespace  -headerpad_max_install_names
         -iframework -image_base  -init  -install_name
         -keep_private_externs -multi_module  -multiply_defined
         -multiply_defined_unused -noall_load
         -no_dead_strip_inits_and_terms -nofixprebinding
         -nomultidefs  -noprebind  -noseglinkedit -pagezero_size
         -prebind  -prebind_all_twolevel_modules -private_bundle
         -read_only_relocs  -sectalign -sectobjectsymbols
         -whyload  -seg1addr -sectcreate  -sectobjectsymbols
         -sectorder -segaddr -segs_read_only_addr
         -segs_read_write_addr -seg_addr_table
         -seg_addr_table_filename  -seglinkedit -segprot
         -segs_read_only_addr  -segs_read_write_addr
         -single_module  -static  -sub_library  -sub_umbrella
         -twolevel_namespace  -umbrella  -undefined
         -unexported_symbols_list  -weak_reference_mismatches
         -whatsloaded -F -gused -gfull
         -mmacosx-version-min=version -mkernel -mone-byte-bool

         DEC Alpha Options -mno-fp-regs  -msoft-float -mieee
         -mieee-with-inexact  -mieee-conformant
         -mfp-trap-mode=mode  -mfp-rounding-mode=mode
         -mtrap-precision=mode  -mbuild-constants -mcpu=cpu-type
         -mtune=cpu-type -mbwx  -mmax  -mfix  -mcix -mfloat-vax
         -mfloat-ieee -mexplicit-relocs  -msmall-data
         -mlarge-data -msmall-text  -mlarge-text
         -mmemory-latency=time

         FR30 Options -msmall-model -mno-lsim

         FRV Options -mgpr-32  -mgpr-64  -mfpr-32  -mfpr-64
         -mhard-float  -msoft-float -malloc-cc  -mfixed-cc
         -mdword  -mno-dword -mdouble  -mno-double -mmedia
         -mno-media  -mmuladd  -mno-muladd -mfdpic  -minline-plt
         -mgprel-ro  -multilib-library-pic -mlinked-fp
         -mlong-calls  -malign-labels -mlibrary-pic  -macc-4
         -macc-8 -mpack  -mno-pack  -mno-eflags  -mcond-move
         -mno-cond-move -moptimize-membar -mno-optimize-membar
         -mscc  -mno-scc  -mcond-exec  -mno-cond-exec
         -mvliw-branch  -mno-vliw-branch -mmulti-cond-exec
         -mno-multi-cond-exec  -mnested-cond-exec
         -mno-nested-cond-exec  -mtomcat-stats -mTLS -mtls
         -mcpu=cpu

         GNU/Linux Options -mglibc -muclibc -mbionic -mandroid
         -tno-android-cc -tno-android-ld

         H8/300 Options -mrelax  -mh  -ms  -mn  -mexr -mno-exr
         -mint32  -malign-300

         HPPA Options -march=architecture-type -mbig-switch
         -mdisable-fpregs  -mdisable-indexing
         -mfast-indirect-calls  -mgas  -mgnu-ld   -mhp-ld
         -mfixed-range=register-range -mjump-in-delay
         -mlinker-opt -mlong-calls -mlong-load-store
         -mno-big-switch  -mno-disable-fpregs
         -mno-disable-indexing  -mno-fast-indirect-calls
         -mno-gas -mno-jump-in-delay  -mno-long-load-store
         -mno-portable-runtime  -mno-soft-float -mno-space-regs
         -msoft-float  -mpa-risc-1-0 -mpa-risc-1-1  -mpa-risc-2-0
         -mportable-runtime -mschedule=cpu-type  -mspace-regs
         -msio  -mwsio -munix=unix-std  -nolibdld  -static
         -threads

         i386 and x86-64 Options -mtune=cpu-type  -march=cpu-type
         -mfpmath=unit -masm=dialect  -mno-fancy-math-387
         -mno-fp-ret-in-387  -msoft-float -mno-wide-multiply
         -mrtd  -malign-double -mpreferred-stack-boundary=num
         -mincoming-stack-boundary=num -mcld -mcx16 -msahf
         -mmovbe -mcrc32 -mrecip -mrecip=opt -mvzeroupper
         -mprefer-avx128 -mmmx  -msse  -msse2 -msse3 -mssse3
         -msse4.1 -msse4.2 -msse4 -mavx -mavx2 -maes -mpclmul
         -mfsgsbase -mrdrnd -mf16c -mfma -msse4a -m3dnow -mpopcnt
         -mabm -mbmi -mtbm -mfma4 -mxop -mlzcnt -mbmi2 -mrtm
         -mlwp -mthreads -mno-align-stringops
         -minline-all-stringops -minline-stringops-dynamically
         -mstringop-strategy=alg -mpush-args
         -maccumulate-outgoing-args  -m128bit-long-double
         -m96bit-long-double -mlong-double-64 -mlong-double-80
         -mregparm=num  -msseregparm -mveclibabi=type
         -mvect8-ret-in-mem -mpc32 -mpc64 -mpc80 -mstackrealign
         -momit-leaf-frame-pointer  -mno-red-zone
         -mno-tls-direct-seg-refs -mcmodel=code-model -mabi=name
         -maddress-mode=mode -m32 -m64 -mx32
         -mlarge-data-threshold=num -msse2avx -mfentry
         -m8bit-idiv -mavx256-split-unaligned-load
         -mavx256-split-unaligned-store

         i386 and x86-64 Windows Options -mconsole -mcygwin
         -mno-cygwin -mdll -mnop-fun-dllimport -mthread -municode
         -mwin32 -mwindows -fno-set-stack-executable

         IA-64 Options -mbig-endian  -mlittle-endian  -mgnu-as
         -mgnu-ld  -mno-pic -mvolatile-asm-stop  -mregister-names
         -msdata -mno-sdata -mconstant-gp  -mauto-pic
         -mfused-madd -minline-float-divide-min-latency
         -minline-float-divide-max-throughput
         -mno-inline-float-divide -minline-int-divide-min-latency
         -minline-int-divide-max-throughput
         -mno-inline-int-divide -minline-sqrt-min-latency
         -minline-sqrt-max-throughput -mno-inline-sqrt
         -mdwarf2-asm -mearly-stop-bits -mfixed-range=register-
         range -mtls-size=tls-size -mtune=cpu-type -milp32 -mlp64
         -msched-br-data-spec -msched-ar-data-spec
         -msched-control-spec -msched-br-in-data-spec
         -msched-ar-in-data-spec -msched-in-control-spec
         -msched-spec-ldc -msched-spec-control-ldc
         -msched-prefer-non-data-spec-insns
         -msched-prefer-non-control-spec-insns
         -msched-stop-bits-after-every-cycle
         -msched-count-spec-in-critical-path
         -msel-sched-dont-check-control-spec
         -msched-fp-mem-deps-zero-cost
         -msched-max-memory-insns-hard-limit
         -msched-max-memory-insns=max-insns

         LM32 Options -mbarrel-shift-enabled -mdivide-enabled
         -mmultiply-enabled -msign-extend-enabled -muser-enabled

         M32R/D Options -m32r2 -m32rx -m32r -mdebug -malign-loops
         -mno-align-loops -missue-rate=number
         -mbranch-cost=number -mmodel=code-size-model-type
         -msdata=sdata-type -mno-flush-func -mflush-func=name
         -mno-flush-trap -mflush-trap=number -G num

         M32C Options -mcpu=cpu -msim -memregs=number

         M680x0 Options -march=arch  -mcpu=cpu  -mtune=tune
         -m68000  -m68020  -m68020-40  -m68020-60  -m68030
         -m68040 -m68060  -mcpu32  -m5200  -m5206e  -m528x
         -m5307  -m5407 -mcfv4e  -mbitfield  -mno-bitfield
         -mc68000  -mc68020 -mnobitfield  -mrtd  -mno-rtd  -mdiv
         -mno-div  -mshort -mno-short  -mhard-float  -m68881
         -msoft-float  -mpcrel -malign-int  -mstrict-align
         -msep-data  -mno-sep-data -mshared-library-id=n
         -mid-shared-library  -mno-id-shared-library -mxgot
         -mno-xgot

         MCore Options -mhardlit  -mno-hardlit  -mdiv  -mno-div
         -mrelax-immediates -mno-relax-immediates
         -mwide-bitfields  -mno-wide-bitfields -m4byte-functions
         -mno-4byte-functions  -mcallgraph-data
         -mno-callgraph-data  -mslow-bytes  -mno-slow-bytes
         -mno-lsim -mlittle-endian  -mbig-endian  -m210  -m340
         -mstack-increment

         MeP Options -mabsdiff -mall-opts -maverage -mbased=n
         -mbitops -mc=n -mclip -mconfig=name -mcop -mcop32
         -mcop64 -mivc2 -mdc -mdiv -meb -mel -mio-volatile -ml
         -mleadz -mm -mminmax -mmult -mno-opts -mrepeat -ms
         -msatur -msdram -msim -msimnovec -mtf -mtiny=n

         MicroBlaze Options -msoft-float -mhard-float
         -msmall-divides -mcpu=cpu -mmemcpy -mxl-soft-mul
         -mxl-soft-div -mxl-barrel-shift -mxl-pattern-compare
         -mxl-stack-check -mxl-gp-opt -mno-clearbss
         -mxl-multiply-high -mxl-float-convert -mxl-float-sqrt
         -mbig-endian -mlittle-endian -mxl-reorder
         -mxl-mode-app-model

         MIPS Options -EL  -EB  -march=arch  -mtune=arch -mips1
         -mips2  -mips3  -mips4  -mips32  -mips32r2 -mips64
         -mips64r2 -mips16  -mno-mips16  -mflip-mips16
         -minterlink-mips16  -mno-interlink-mips16 -mabi=abi
         -mabicalls  -mno-abicalls -mshared  -mno-shared  -mplt
         -mno-plt  -mxgot  -mno-xgot -mgp32  -mgp64  -mfp32
         -mfp64  -mhard-float  -msoft-float -mno-float
         -msingle-float  -mdouble-float -mdsp  -mno-dsp  -mdspr2
         -mno-dspr2 -mmcu -mmno-mcu -mfpu=fpu-type -msmartmips
         -mno-smartmips -mpaired-single  -mno-paired-single
         -mdmx  -mno-mdmx -mips3d  -mno-mips3d  -mmt  -mno-mt
         -mllsc  -mno-llsc -mlong64  -mlong32  -msym32
         -mno-sym32 -Gnum  -mlocal-sdata  -mno-local-sdata
         -mextern-sdata  -mno-extern-sdata  -mgpopt  -mno-gopt
         -membedded-data  -mno-embedded-data
         -muninit-const-in-rodata  -mno-uninit-const-in-rodata
         -mcode-readable=setting -msplit-addresses
         -mno-split-addresses -mexplicit-relocs
         -mno-explicit-relocs -mcheck-zero-division
         -mno-check-zero-division -mdivide-traps  -mdivide-breaks
         -mmemcpy  -mno-memcpy  -mlong-calls  -mno-long-calls
         -mmad  -mno-mad  -mfused-madd  -mno-fused-madd  -nocpp
         -mfix-24k -mno-fix-24k -mfix-r4000  -mno-fix-r4000
         -mfix-r4400  -mno-fix-r4400 -mfix-r10000 -mno-fix-r10000
         -mfix-vr4120  -mno-fix-vr4120 -mfix-vr4130
         -mno-fix-vr4130  -mfix-sb1  -mno-fix-sb1
         -mflush-func=func  -mno-flush-func -mbranch-cost=num
         -mbranch-likely  -mno-branch-likely -mfp-exceptions
         -mno-fp-exceptions -mvr4130-align -mno-vr4130-align
         -msynci -mno-synci -mrelax-pic-calls
         -mno-relax-pic-calls -mmcount-ra-address

         MMIX Options -mlibfuncs  -mno-libfuncs  -mepsilon
         -mno-epsilon  -mabi=gnu -mabi=mmixware  -mzero-extend
         -mknuthdiv  -mtoplevel-symbols -melf  -mbranch-predict
         -mno-branch-predict  -mbase-addresses
         -mno-base-addresses  -msingle-exit  -mno-single-exit

         MN10300 Options -mmult-bug  -mno-mult-bug -mno-am33
         -mam33 -mam33-2 -mam34 -mtune=cpu-type
         -mreturn-pointer-on-d0 -mno-crt0  -mrelax -mliw -msetlb

         Moxie Options -meb -mel -mno-crt0

         PDP-11 Options -mfpu  -msoft-float  -mac0  -mno-ac0
         -m40  -m45  -m10 -mbcopy  -mbcopy-builtin  -mint32
         -mno-int16 -mint16  -mno-int32  -mfloat32  -mno-float64
         -mfloat64  -mno-float32  -mabshi  -mno-abshi
         -mbranch-expensive  -mbranch-cheap -munix-asm  -mdec-asm

         picoChip Options -mae=ae_type -mvliw-lookahead=N
         -msymbol-as-address -mno-inefficient-warnings

         PowerPC Options See RS/6000 and PowerPC Options.

         RL78 Options -msim -mmul=none -mmul=g13 -mmul=rl78

         RS/6000 and PowerPC Options -mcpu=cpu-type -mtune=cpu-
         type -mcmodel=code-model -mpowerpc64 -maltivec
         -mno-altivec -mpowerpc-gpopt  -mno-powerpc-gpopt
         -mpowerpc-gfxopt  -mno-powerpc-gfxopt -mmfcrf
         -mno-mfcrf  -mpopcntb  -mno-popcntb -mpopcntd
         -mno-popcntd -mfprnd  -mno-fprnd -mcmpb -mno-cmpb
         -mmfpgpr -mno-mfpgpr -mhard-dfp -mno-hard-dfp -mfull-toc
         -mminimal-toc  -mno-fp-in-toc  -mno-sum-in-toc -m64
         -m32  -mxl-compat  -mno-xl-compat  -mpe -malign-power
         -malign-natural -msoft-float  -mhard-float  -mmultiple
         -mno-multiple -msingle-float -mdouble-float -msimple-fpu
         -mstring  -mno-string  -mupdate  -mno-update
         -mavoid-indexed-addresses  -mno-avoid-indexed-addresses
         -mfused-madd  -mno-fused-madd  -mbit-align
         -mno-bit-align -mstrict-align  -mno-strict-align
         -mrelocatable -mno-relocatable  -mrelocatable-lib
         -mno-relocatable-lib -mtoc  -mno-toc  -mlittle
         -mlittle-endian  -mbig  -mbig-endian -mdynamic-no-pic
         -maltivec -mswdiv  -msingle-pic-base
         -mprioritize-restricted-insns=priority
         -msched-costly-dep=dependence_type
         -minsert-sched-nops=scheme -mcall-sysv  -mcall-netbsd
         -maix-struct-return  -msvr4-struct-return -mabi=abi-type
         -msecure-plt -mbss-plt -mblock-move-inline-limit=num
         -misel -mno-isel -misel=yes  -misel=no -mspe -mno-spe
         -mspe=yes  -mspe=no -mpaired -mgen-cell-microcode
         -mwarn-cell-microcode -mvrsave -mno-vrsave -mmulhw
         -mno-mulhw -mdlmzb -mno-dlmzb -mfloat-gprs=yes
         -mfloat-gprs=no -mfloat-gprs=single -mfloat-gprs=double
         -mprototype  -mno-prototype -msim  -mmvme  -mads
         -myellowknife  -memb  -msdata -msdata=opt  -mvxworks  -G
         num  -pthread -mrecip -mrecip=opt -mno-recip
         -mrecip-precision -mno-recip-precision -mveclibabi=type
         -mfriz -mno-friz -mpointers-to-nested-functions
         -mno-pointers-to-nested-functions -msave-toc-indirect
         -mno-save-toc-indirect

         RX Options -m64bit-doubles  -m32bit-doubles  -fpu
         -nofpu -mcpu= -mbig-endian-data -mlittle-endian-data
         -msmall-data -msim  -mno-sim -mas100-syntax
         -mno-as100-syntax -mrelax -mmax-constant-size=
         -mint-register= -mpid -mno-warn-multiple-fast-interrupts
         -msave-acc-in-interrupts

         S/390 and zSeries Options -mtune=cpu-type  -march=cpu-
         type -mhard-float  -msoft-float  -mhard-dfp
         -mno-hard-dfp -mlong-double-64 -mlong-double-128
         -mbackchain  -mno-backchain -mpacked-stack
         -mno-packed-stack -msmall-exec  -mno-small-exec  -mmvcle
         -mno-mvcle -m64  -m31  -mdebug  -mno-debug  -mesa
         -mzarch -mtpf-trace -mno-tpf-trace  -mfused-madd
         -mno-fused-madd -mwarn-framesize  -mwarn-dynamicstack
         -mstack-size -mstack-guard

         Score Options -meb -mel -mnhwloop -muls -mmac -mscore5
         -mscore5u -mscore7 -mscore7d

         SH Options -m1  -m2  -m2e -m2a-nofpu -m2a-single-only
         -m2a-single -m2a -m3  -m3e -m4-nofpu  -m4-single-only
         -m4-single  -m4 -m4a-nofpu -m4a-single-only -m4a-single
         -m4a -m4al -m5-64media  -m5-64media-nofpu -m5-32media
         -m5-32media-nofpu -m5-compact  -m5-compact-nofpu -mb
         -ml  -mdalign  -mrelax -mbigtable -mfmovd -mhitachi
         -mrenesas -mno-renesas -mnomacsave -mieee -mno-ieee
         -mbitops  -misize  -minline-ic_invalidate -mpadstruct
         -mspace -mprefergot  -musermode -multcost=number
         -mdiv=strategy -mdivsi3_libfunc=name
         -mfixed-range=register-range -mindexed-addressing
         -mgettrcost=number -mpt-fixed -maccumulate-outgoing-args
         -minvalid-symbols -matomic-model=atomic-model
         -mbranch-cost=num -mzdcbranch -mno-zdcbranch -mcbranchdi
         -mcmpeqdi -mfused-madd -mno-fused-madd -mfsca -mno-fsca
         -mfsrra -mno-fsrra -mpretend-cmove -mtas

         Solaris 2 Options -mimpure-text  -mno-impure-text
         -pthreads -pthread

         SPARC Options -mcpu=cpu-type -mtune=cpu-type
         -mcmodel=code-model -mmemory-model=mem-model -m32  -m64
         -mapp-regs  -mno-app-regs -mfaster-structs
         -mno-faster-structs  -mflat  -mno-flat -mfpu  -mno-fpu
         -mhard-float  -msoft-float -mhard-quad-float
         -msoft-quad-float -mstack-bias  -mno-stack-bias
         -munaligned-doubles  -mno-unaligned-doubles -mv8plus
         -mno-v8plus  -mvis  -mno-vis -mvis2  -mno-vis2  -mvis3
         -mno-vis3 -mcbcond -mno-cbcond -mfmaf  -mno-fmaf  -mpopc
         -mno-popc -mfix-at697f

         SPU Options -mwarn-reloc -merror-reloc -msafe-dma
         -munsafe-dma -mbranch-hints -msmall-mem -mlarge-mem
         -mstdmain -mfixed-range=register-range -mea32 -mea64
         -maddress-space-conversion -mno-address-space-conversion
         -mcache-size=cache-size -matomic-updates
         -mno-atomic-updates

         System V Options -Qy  -Qn  -YP,paths  -Ym,dir

         TILE-Gx Options -mcpu=cpu -m32 -m64 -mcmodel=code-model

         TILEPro Options -mcpu=cpu -m32

         V850 Options -mlong-calls  -mno-long-calls  -mep
         -mno-ep -mprolog-function  -mno-prolog-function  -mspace
         -mtda=n  -msda=n  -mzda=n -mapp-regs  -mno-app-regs
         -mdisable-callt  -mno-disable-callt -mv850e2v3 -mv850e2
         -mv850e1 -mv850es -mv850e -mv850 -mv850e3v5 -mloop
         -mrelax -mlong-jumps -msoft-float -mhard-float -mgcc-abi
         -mrh850-abi -mbig-switch

         VAX Options -mg  -mgnu  -munix

         VMS Options -mvms-return-codes -mdebug-main=prefix
         -mmalloc64 -mpointer-size=size

         VxWorks Options -mrtp  -non-static  -Bstatic  -Bdynamic
         -Xbind-lazy  -Xbind-now

         x86-64 Options See i386 and x86-64 Options.

         Xstormy16 Options -msim

         Xtensa Options -mconst16 -mno-const16 -mfused-madd
         -mno-fused-madd -mforce-no-pic -mserialize-volatile
         -mno-serialize-volatile -mtext-section-literals
         -mno-text-section-literals -mtarget-align
         -mno-target-align -mlongcalls  -mno-longcalls

         zSeries Options See S/390 and zSeries Options.

     Code Generation Options
         -fcall-saved-reg  -fcall-used-reg -ffixed-reg
         -fexceptions -fnon-call-exceptions
         -fdelete-dead-exceptions  -funwind-tables
         -fasynchronous-unwind-tables -finhibit-size-directive
         -finstrument-functions
         -finstrument-functions-exclude-function-list=sym,sym,...
         -finstrument-functions-exclude-file-list=file,file,...
         -fno-common  -fno-ident -fpcc-struct-return  -fpic
         -fPIC -fpie -fPIE -fno-jump-tables -frecord-gcc-switches
         -freg-struct-return  -fshort-enums -fshort-double
         -fshort-wchar -fverbose-asm  -fpack-struct[=n]
         -fstack-check -fstack-limit-register=reg
         -fstack-limit-symbol=sym -fno-stack-limit -fsplit-stack
         -fleading-underscore  -ftls-model=model
         -fstack-reuse=reuse_level -ftrapv  -fwrapv
         -fbounds-check -fvisibility -fstrict-volatile-bitfields
         -fsync-libcalls

  Options Controlling the Kind of Output
     Compilation can involve up to four stages: preprocessing,
     compilation proper, assembly and linking, always in that
     order.  GCC is capable of preprocessing and compiling
     several files either into several assembler input files, or
     into one assembler input file; then each assembler input
     file produces an object file, and linking combines all the
     object files (those newly compiled, and those specified as
     input) into an executable file.

     For any given input file, the file name suffix determines
     what kind of compilation is done:

     file.c
         C source code that must be preprocessed.

     file.i
         C source code that should not be preprocessed.

     file.ii
         C++ source code that should not be preprocessed.

     file.m
         Objective-C source code.  Note that you must link with
         the libobjc library to make an Objective-C program work.

     file.mi
         Objective-C source code that should not be preprocessed.

     file.mm
     file.M
         Objective-C++ source code.  Note that you must link with
         the libobjc library to make an Objective-C++ program
         work.  Note that .M refers to a literal capital M.

     file.mii
         Objective-C++ source code that should not be
         preprocessed.

     file.h
         C, C++, Objective-C or Objective-C++ header file to be
         turned into a precompiled header (default), or C, C++
         header file to be turned into an Ada spec (via the
         -fdump-ada-spec switch).

     file.cc
     file.cp
     file.cxx
     file.cpp
     file.CPP
     file.c++
     file.C
         C++ source code that must be preprocessed.  Note that in
         .cxx, the last two letters must both be literally x.
         Likewise, .C refers to a literal capital C.

     file.mm
     file.M
         Objective-C++ source code that must be preprocessed.

     file.mii
         Objective-C++ source code that should not be
         preprocessed.

     file.hh
     file.H
     file.hp
     file.hxx
     file.hpp
     file.HPP
     file.h++
     file.tcc
         C++ header file to be turned into a precompiled header
         or Ada spec.

     file.f
     file.for
     file.ftn
         Fixed form Fortran source code that should not be
         preprocessed.

     file.F
     file.FOR
     file.fpp
     file.FPP
     file.FTN
         Fixed form Fortran source code that must be preprocessed
         (with the traditional preprocessor).

     file.f90
     file.f95
     file.f03
     file.f08
         Free form Fortran source code that should not be
         preprocessed.

     file.F90
     file.F95
     file.F03
     file.F08
         Free form Fortran source code that must be preprocessed
         (with the traditional preprocessor).

     file.go
         Go source code.

     file.ads
         Ada source code file that contains a library unit
         declaration (a declaration of a package, subprogram, or
         generic, or a generic instantiation), or a library unit
         renaming declaration (a package, generic, or subprogram
         renaming declaration).  Such files are also called
         specs.

     file.adb
         Ada source code file containing a library unit body (a
         subprogram or package body).  Such files are also called
         bodies.

     file.s

         Assembler code.

     file.S
     file.sx
         Assembler code that must be preprocessed.

     other
         An object file to be fed straight into linking.  Any
         file name with no recognized suffix is treated this way.

     You can specify the input language explicitly with the -x
     option:

     -x language
         Specify explicitly the language for the following input
         files (rather than letting the compiler choose a default
         based on the file name suffix).  This option applies to
         all following input files until the next -x option.
         Possible values for language are:

                 c  c-header  cpp-output
                 c++  c++-header  c++-cpp-output
                 objective-c  objective-c-header  objective-c-cpp-output
                 objective-c++ objective-c++-header objective-c++-cpp-output
                 assembler  assembler-with-cpp
                 ada
                 f77  f77-cpp-input f95  f95-cpp-input
                 go
                 java

     -x none
         Turn off any specification of a language, so that
         subsequent files are handled according to their file
         name suffixes (as they are if -x has not been used at
         all).

     -pass-exit-codes
         Normally the gcc program exits with the code of 1 if any
         phase of the compiler returns a non-success return code.
         If you specify -pass-exit-codes, the gcc program instead
         returns with the numerically highest error produced by
         any phase returning an error indication.  The C, C++,
         and Fortran front ends return 4 if an internal compiler
         error is encountered.

     If you only want some of the stages of compilation, you can
     use -x (or filename suffixes) to tell gcc where to start,
     and one of the options -c, -S, or -E to say where gcc is to
     stop.  Note that some combinations (for example, -x cpp-
     output -E) instruct gcc to do nothing at all.

     -c  Compile or assemble the source files, but do not link.

         The linking stage simply is not done.  The ultimate
         output is in the form of an object file for each source
         file.

         By default, the object file name for a source file is
         made by replacing the suffix .c, .i, .s, etc., with .o.

         Unrecognized input files, not requiring compilation or
         assembly, are ignored.

     -S  Stop after the stage of compilation proper; do not
         assemble.  The output is in the form of an assembler
         code file for each non-assembler input file specified.

         By default, the assembler file name for a source file is
         made by replacing the suffix .c, .i, etc., with .s.

         Input files that don't require compilation are ignored.

     -E  Stop after the preprocessing stage; do not run the
         compiler proper.  The output is in the form of
         preprocessed source code, which is sent to the standard
         output.

         Input files that don't require preprocessing are
         ignored.

     -o file
         Place output in file file.  This applies to whatever
         sort of output is being produced, whether it be an
         executable file, an object file, an assembler file or
         preprocessed C code.

         If -o is not specified, the default is to put an
         executable file in a.out, the object file for
         source.suffix in source.o, its assembler file in
         source.s, a precompiled header file in
         source.suffix.gch, and all preprocessed C source on
         standard output.

     -v  Print (on standard error output) the commands executed
         to run the stages of compilation.  Also print the
         version number of the compiler driver program and of the
         preprocessor and the compiler proper.

     -###
         Like -v except the commands are not executed and
         arguments are quoted unless they contain only
         alphanumeric characters or "./-_".  This is useful for
         shell scripts to capture the driver-generated command
         lines.

     -pipe
         Use pipes rather than temporary files for communication
         between the various stages of compilation.  This fails
         to work on some systems where the assembler is unable to
         read from a pipe; but the GNU assembler has no trouble.

     --help
         Print (on the standard output) a description of the
         command-line options understood by gcc.  If the -v
         option is also specified then --help is also passed on
         to the various processes invoked by gcc, so that they
         can display the command-line options they accept.  If
         the -Wextra option has also been specified (prior to the
         --help option), then command-line options that have no
         documentation associated with them are also displayed.

     --target-help
         Print (on the standard output) a description of target-
         specific command-line options for each tool.  For some
         targets extra target-specific information may also be
         printed.

     --help={class|[^]qualifier}[,...]
         Print (on the standard output) a description of the
         command-line options understood by the compiler that fit
         into all specified classes and qualifiers.  These are
         the supported classes:

         optimizers
             Display all of the optimization options supported by
             the compiler.

         warnings
             Display all of the options controlling warning
             messages produced by the compiler.

         target
             Display target-specific options.  Unlike the
             --target-help option however, target-specific
             options of the linker and assembler are not
             displayed.  This is because those tools do not
             currently support the extended --help= syntax.

         params
             Display the values recognized by the --param option.

         language
             Display the options supported for language, where
             language is the name of one of the languages
             supported in this version of GCC.

         common

             Display the options that are common to all
             languages.

         These are the supported qualifiers:

         undocumented
             Display only those options that are undocumented.

         joined
             Display options taking an argument that appears
             after an equal sign in the same continuous piece of
             text, such as:  --help=target.

         separate
             Display options taking an argument that appears as a
             separate word following the original option, such
             as: -o output-file.

         Thus for example to display all the undocumented
         target-specific switches supported by the compiler, use:

                 --help=target,undocumented

         The sense of a qualifier can be inverted by prefixing it
         with the ^ character, so for example to display all
         binary warning options (i.e., ones that are either on or
         off and that do not take an argument) that have a
         description, use:

                 --help=warnings,^joined,^undocumented

         The argument to --help= should not consist solely of
         inverted qualifiers.

         Combining several classes is possible, although this
         usually restricts the output so much that there is
         nothing to display.  One case where it does work,
         however, is when one of the classes is target.  For
         example, to display all the target-specific optimization
         options, use:

                 --help=target,optimizers

         The --help= option can be repeated on the command line.
         Each successive use displays its requested class of
         options, skipping those that have already been
         displayed.

         If the -Q option appears on the command line before the
         --help= option, then the descriptive text displayed by
         --help= is changed.  Instead of describing the displayed
         options, an indication is given as to whether the option
         is enabled, disabled or set to a specific value
         (assuming that the compiler knows this at the point
         where the --help= option is used).

         Here is a truncated example from the ARM port of gcc:

                   % gcc -Q -mabi=2 --help=target -c
                   The following options are target specific:
                   -mabi=                       2
                   -mabort-on-noreturn                   [disabled]
                   -mapcs                       [disabled]

         The output is sensitive to the effects of previous
         command-line options, so for example it is possible to
         find out which optimizations are enabled at -O2 by
         using:

                 -Q -O2 --help=optimizers

         Alternatively you can discover which binary
         optimizations are enabled by -O3 by using:

                 gcc -c -Q -O3 --help=optimizers > /tmp/O3-opts
                 gcc -c -Q -O2 --help=optimizers > /tmp/O2-opts
                 diff /tmp/O2-opts /tmp/O3-opts | grep enabled

     -no-canonical-prefixes
         Do not expand any symbolic links, resolve references to
         /../ or /./, or make the path absolute when generating a
         relative prefix.

     --version
         Display the version number and copyrights of the invoked
         GCC.

     -wrapper
         Invoke all subcommands under a wrapper program.  The
         name of the wrapper program and its parameters are
         passed as a comma separated list.

                 gcc -c t.c -wrapper gdb,--args

         This invokes all subprograms of gcc under gdb --args,
         thus the invocation of cc1 is gdb --args cc1 ....

     -fplugin=name.so
         Load the plugin code in file name.so, assumed to be a
         shared object to be dlopen'd by the compiler.  The base
         name of the shared object file is used to identify the
         plugin for the purposes of argument parsing (See
         -fplugin-arg-name-key=value below).  Each plugin should
         define the callback functions specified in the Plugins

         API.

     -fplugin-arg-name-key=value
         Define an argument called key with a value of value for
         the plugin called name.

     -fdump-ada-spec[-slim]
         For C and C++ source and include files, generate
         corresponding Ada specs.

     -fdump-go-spec=file
         For input files in any language, generate corresponding
         Go declarations in file.  This generates Go "const",
         "type", "var", and "func" declarations which may be a
         useful way to start writing a Go interface to code
         written in some other language.

     @file
         Read command-line options from file.  The options read
         are inserted in place of the original @file option.  If
         file does not exist, or cannot be read, then the option
         will be treated literally, and not removed.

         Options in file are separated by whitespace.  A
         whitespace character may be included in an option by
         surrounding the entire option in either single or double
         quotes.  Any character (including a backslash) may be
         included by prefixing the character to be included with
         a backslash.  The file may itself contain additional
         @file options; any such options will be processed
         recursively.

  Compiling C++ Programs
     C++ source files conventionally use one of the suffixes .C,
     .cc, .cpp, .CPP, .c++, .cp, or .cxx; C++ header files often
     use .hh, .hpp, .H, or (for shared template code) .tcc; and
     preprocessed C++ files use the suffix .ii.  GCC recognizes
     files with these names and compiles them as C++ programs
     even if you call the compiler the same way as for compiling
     C programs (usually with the name gcc).

     However, the use of gcc does not add the C++ library.  g++
     is a program that calls GCC and automatically specifies
     linking against the C++ library.  It treats .c, .h and .i
     files as C++ source files instead of C source files unless
     -x is used.  This program is also useful when precompiling a
     C header file with a .h extension for use in C++
     compilations.  On many systems, g++ is also installed with
     the name c++.

     When you compile C++ programs, you may specify many of the
     same command-line options that you use for compiling
     programs in any language; or command-line options meaningful
     for C and related languages; or options that are meaningful
     only for C++ programs.

  Options Controlling C Dialect
     The following options control the dialect of C (or languages
     derived from C, such as C++, Objective-C and Objective-C++)
     that the compiler accepts:

     -ansi
         In C mode, this is equivalent to -std=c90. In C++ mode,
         it is equivalent to -std=c++98.

         This turns off certain features of GCC that are
         incompatible with ISO C90 (when compiling C code), or of
         standard C++ (when compiling C++ code), such as the
         "asm" and "typeof" keywords, and predefined macros such
         as "unix" and "vax" that identify the type of system you
         are using.  It also enables the undesirable and rarely
         used ISO trigraph feature.  For the C compiler, it
         disables recognition of C++ style // comments as well as
         the "inline" keyword.

         The alternate keywords "__asm__", "__extension__",
         "__inline__" and "__typeof__" continue to work despite
         -ansi.  You would not want to use them in an ISO C
         program, of course, but it is useful to put them in
         header files that might be included in compilations done
         with -ansi.  Alternate predefined macros such as
         "__unix__" and "__vax__" are also available, with or
         without -ansi.

         The -ansi option does not cause non-ISO programs to be
         rejected gratuitously.  For that, -Wpedantic is required
         in addition to -ansi.

         The macro "__STRICT_ANSI__" is predefined when the -ansi
         option is used.  Some header files may notice this macro
         and refrain from declaring certain functions or defining
         certain macros that the ISO standard doesn't call for;
         this is to avoid interfering with any programs that
         might use these names for other things.

         Functions that are normally built in but do not have
         semantics defined by ISO C (such as "alloca" and "ffs")
         are not built-in functions when -ansi is used.

     -std=
         Determine the language standard.   This option is
         currently only supported when compiling C or C++.

         The compiler can accept several base standards, such as
         c90 or c++98, and GNU dialects of those standards, such
         as gnu90 or gnu++98.  When a base standard is specified,
         the compiler accepts all programs following that
         standard plus those using GNU extensions that do not
         contradict it.  For example, -std=c90 turns off certain
         features of GCC that are incompatible with ISO C90, such
         as the "asm" and "typeof" keywords, but not other GNU
         extensions that do not have a meaning in ISO C90, such
         as omitting the middle term of a "?:"  expression. On
         the other hand, when a GNU dialect of a standard is
         specified, all features supported by the compiler are
         enabled, even when those features change the meaning of
         the base standard.  As a result, some strict-conforming
         programs may be rejected.  The particular standard is
         used by -Wpedantic to identify which features are GNU
         extensions given that version of the standard. For
         example -std=gnu90 -Wpedantic warns about C++ style //
         comments, while -std=gnu99 -Wpedantic does not.

         A value for this option must be provided; possible
         values are

         c90
         c89
         iso9899:1990
             Support all ISO C90 programs (certain GNU extensions
             that conflict with ISO C90 are disabled). Same as
             -ansi for C code.

         iso9899:199409
             ISO C90 as modified in amendment 1.

         c99
         c9x
         iso9899:1999
         iso9899:199x
             ISO C99.  Note that this standard is not yet fully
             supported; see <http://gcc.gnu.org/c99status.html>
             for more information.  The names c9x and
             iso9899:199x are deprecated.

         c11
         c1x
         iso9899:2011
             ISO C11, the 2011 revision of the ISO C standard.
             Support is incomplete and experimental.  The name
             c1x is deprecated.

         gnu90
         gnu89
             GNU dialect of ISO C90 (including some C99
             features). This is the default for C code.

         gnu99
         gnu9x
             GNU dialect of ISO C99.  When ISO C99 is fully
             implemented in GCC, this will become the default.
             The name gnu9x is deprecated.

         gnu11
         gnu1x
             GNU dialect of ISO C11.  Support is incomplete and
             experimental.  The name gnu1x is deprecated.

         c++98
         c++03
             The 1998 ISO C++ standard plus the 2003 technical
             corrigendum and some additional defect reports. Same
             as -ansi for C++ code.

         gnu++98
         gnu++03
             GNU dialect of -std=c++98.  This is the default for
             C++ code.

         c++11
         c++0x
             The 2011 ISO C++ standard plus amendments.  Support
             for C++11 is still experimental, and may change in
             incompatible ways in future releases.  The name
             c++0x is deprecated.

         gnu++11
         gnu++0x
             GNU dialect of -std=c++11. Support for C++11 is
             still experimental, and may change in incompatible
             ways in future releases.  The name gnu++0x is
             deprecated.

         c++1y
             The next revision of the ISO C++ standard,
             tentatively planned for 2017.  Support is highly
             experimental, and will almost certainly change in
             incompatible ways in future releases.

         gnu++1y
             GNU dialect of -std=c++1y.  Support is highly
             experimental, and will almost certainly change in
             incompatible ways in future releases.

     -fgnu89-inline
         The option -fgnu89-inline tells GCC to use the
         traditional GNU semantics for "inline" functions when in
         C99 mode.
           This option is accepted and ignored by GCC versions

         4.1.3 up to but not including 4.3.  In GCC versions 4.3
         and later it changes the behavior of GCC in C99 mode.
         Using this option is roughly equivalent to adding the
         "gnu_inline" function attribute to all inline functions.

         The option -fno-gnu89-inline explicitly tells GCC to use
         the C99 semantics for "inline" when in C99 or gnu99 mode
         (i.e., it specifies the default behavior).  This option
         was first supported in GCC 4.3.  This option is not
         supported in -std=c90 or -std=gnu90 mode.

         The preprocessor macros "__GNUC_GNU_INLINE__" and
         "__GNUC_STDC_INLINE__" may be used to check which
         semantics are in effect for "inline" functions.

     -aux-info filename
         Output to the given filename prototyped declarations for
         all functions declared and/or defined in a translation
         unit, including those in header files.  This option is
         silently ignored in any language other than C.

         Besides declarations, the file indicates, in comments,
         the origin of each declaration (source file and line),
         whether the declaration was implicit, prototyped or
         unprototyped (I, N for new or O for old, respectively,
         in the first character after the line number and the
         colon), and whether it came from a declaration or a
         definition (C or F, respectively, in the following
         character).  In the case of function definitions, a
         K&R-style list of arguments followed by their
         declarations is also provided, inside comments, after
         the declaration.

     -fallow-parameterless-variadic-functions
         Accept variadic functions without named parameters.

         Although it is possible to define such a function, this
         is not very useful as it is not possible to read the
         arguments.  This is only supported for C as this
         construct is allowed by C++.

     -fno-asm
         Do not recognize "asm", "inline" or "typeof" as a
         keyword, so that code can use these words as
         identifiers.  You can use the keywords "__asm__",
         "__inline__" and "__typeof__" instead.  -ansi implies
         -fno-asm.

         In C++, this switch only affects the "typeof" keyword,
         since "asm" and "inline" are standard keywords.  You may
         want to use the -fno-gnu-keywords flag instead, which
         has the same effect.  In C99 mode (-std=c99 or
         -std=gnu99), this switch only affects the "asm" and
         "typeof" keywords, since "inline" is a standard keyword
         in ISO C99.

     -fno-builtin
     -fno-builtin-function
         Don't recognize built-in functions that do not begin
         with __builtin_ as prefix.

         GCC normally generates special code to handle certain
         built-in functions more efficiently; for instance, calls
         to "alloca" may become single instructions which adjust
         the stack directly, and calls to "memcpy" may become
         inline copy loops.  The resulting code is often both
         smaller and faster, but since the function calls no
         longer appear as such, you cannot set a breakpoint on
         those calls, nor can you change the behavior of the
         functions by linking with a different library.  In
         addition, when a function is recognized as a built-in
         function, GCC may use information about that function to
         warn about problems with calls to that function, or to
         generate more efficient code, even if the resulting code
         still contains calls to that function.  For example,
         warnings are given with -Wformat for bad calls to
         "printf" when "printf" is built in and "strlen" is known
         not to modify global memory.

         With the -fno-builtin-function option only the built-in
         function function is disabled.  function must not begin
         with __builtin_.  If a function is named that is not
         built-in in this version of GCC, this option is ignored.
         There is no corresponding -fbuiltin-function option; if
         you wish to enable built-in functions selectively when
         using -fno-builtin or -ffreestanding, you may define
         macros such as:

                 #define abs(n)          __builtin_abs ((n))
                 #define strcpy(d, s)    __builtin_strcpy ((d), (s))

     -fhosted
         Assert that compilation targets a hosted environment.
         This implies -fbuiltin.  A hosted environment is one in
         which the entire standard library is available, and in
         which "main" has a return type of "int".  Examples are
         nearly everything except a kernel.  This is equivalent
         to -fno-freestanding.

     -ffreestanding
         Assert that compilation targets a freestanding
         environment.  This implies -fno-builtin.  A freestanding
         environment is one in which the standard library may not
         exist, and program startup may not necessarily be at
         "main".  The most obvious example is an OS kernel.  This
         is equivalent to -fno-hosted.

     -fopenmp
         Enable handling of OpenMP directives "#pragma omp" in
         C/C++ and "!$omp" in Fortran.  When -fopenmp is
         specified, the compiler generates parallel code
         according to the OpenMP Application Program Interface
         v3.0 <http://www.openmp.org/>.  This option implies
         -pthread, and thus is only supported on targets that
         have support for -pthread.

     -fgnu-tm
         When the option -fgnu-tm is specified, the compiler
         generates code for the Linux variant of Intel's current
         Transactional Memory ABI specification document
         (Revision 1.1, May 6 2009).  This is an experimental
         feature whose interface may change in future versions of
         GCC, as the official specification changes.  Please note
         that not all architectures are supported for this
         feature.

         For more information on GCC's support for transactional
         memory,

         Note that the transactional memory feature is not
         supported with non-call exceptions
         (-fnon-call-exceptions).

     -fms-extensions
         Accept some non-standard constructs used in Microsoft
         header files.

         In C++ code, this allows member names in structures to
         be similar to previous types declarations.

                 typedef int UOW;
                 struct ABC {
                   UOW UOW;
                 };

         Some cases of unnamed fields in structures and unions
         are only accepted with this option.

     -fplan9-extensions
         Accept some non-standard constructs used in Plan 9 code.

         This enables -fms-extensions, permits passing pointers
         to structures with anonymous fields to functions that
         expect pointers to elements of the type of the field,
         and permits referring to anonymous fields declared using
         a typedef.    This is only supported for C, not C++.

     -trigraphs
         Support ISO C trigraphs.  The -ansi option (and -std
         options for strict ISO C conformance) implies
         -trigraphs.

     -traditional
     -traditional-cpp
         Formerly, these options caused GCC to attempt to emulate
         a pre-standard C compiler.  They are now only supported
         with the -E switch.  The preprocessor continues to
         support a pre-standard mode.  See the GNU CPP manual for
         details.

     -fcond-mismatch
         Allow conditional expressions with mismatched types in
         the second and third arguments.  The value of such an
         expression is void.  This option is not supported for
         C++.

     -flax-vector-conversions
         Allow implicit conversions between vectors with
         differing numbers of elements and/or incompatible
         element types.  This option should not be used for new
         code.

     -funsigned-char
         Let the type "char" be unsigned, like "unsigned char".

         Each kind of machine has a default for what "char"
         should be.  It is either like "unsigned char" by default
         or like "signed char" by default.

         Ideally, a portable program should always use "signed
         char" or "unsigned char" when it depends on the
         signedness of an object.  But many programs have been
         written to use plain "char" and expect it to be signed,
         or expect it to be unsigned, depending on the machines
         they were written for.  This option, and its inverse,
         let you make such a program work with the opposite
         default.

         The type "char" is always a distinct type from each of
         "signed char" or "unsigned char", even though its
         behavior is always just like one of those two.

     -fsigned-char
         Let the type "char" be signed, like "signed char".

         Note that this is equivalent to -fno-unsigned-char,
         which is the negative form of -funsigned-char.
         Likewise, the option -fno-signed-char is equivalent to
         -funsigned-char.

     -fsigned-bitfields
     -funsigned-bitfields
     -fno-signed-bitfields
     -fno-unsigned-bitfields
         These options control whether a bit-field is signed or
         unsigned, when the declaration does not use either
         "signed" or "unsigned".  By default, such a bit-field is
         signed, because this is consistent: the basic integer
         types such as "int" are signed types.

  Options Controlling C++ Dialect
     This section describes the command-line options that are
     only meaningful for C++ programs.  You can also use most of
     the GNU compiler options regardless of what language your
     program is in.  For example, you might compile a file
     "firstClass.C" like this:

             g++ -g -frepo -O -c firstClass.C

     In this example, only -frepo is an option meant only for C++
     programs; you can use the other options with any language
     supported by GCC.

     Here is a list of options that are only for compiling C++
     programs:

     -fabi-version=n
         Use version n of the C++ ABI.  The default is version 2.

         Version 0 refers to the version conforming most closely
         to the C++ ABI specification.  Therefore, the ABI
         obtained using version 0 will change in different
         versions of G++ as ABI bugs are fixed.

         Version 1 is the version of the C++ ABI that first
         appeared in G++ 3.2.

         Version 2 is the version of the C++ ABI that first
         appeared in G++ 3.4.

         Version 3 corrects an error in mangling a constant
         address as a template argument.

         Version 4, which first appeared in G++ 4.5, implements a
         standard mangling for vector types.

         Version 5, which first appeared in G++ 4.6, corrects the
         mangling of attribute const/volatile on function pointer
         types, decltype of a plain decl, and use of a function
         parameter in the declaration of another parameter.

         Version 6, which first appeared in G++ 4.7, corrects the
         promotion behavior of C++11 scoped enums and the
         mangling of template argument packs, const/static_cast,
         prefix ++ and --, and a class scope function used as a
         template argument.

         See also -Wabi.

     -fno-access-control
         Turn off all access checking.  This switch is mainly
         useful for working around bugs in the access control
         code.

     -fcheck-new
         Check that the pointer returned by "operator new" is
         non-null before attempting to modify the storage
         allocated.  This check is normally unnecessary because
         the C++ standard specifies that "operator new" only
         returns 0 if it is declared throw(), in which case the
         compiler always checks the return value even without
         this option.  In all other cases, when "operator new"
         has a non-empty exception specification, memory
         exhaustion is signalled by throwing "std::bad_alloc".
         See also new (nothrow).

     -fconstexpr-depth=n
         Set the maximum nested evaluation depth for C++11
         constexpr functions to n.  A limit is needed to detect
         endless recursion during constant expression evaluation.
         The minimum specified by the standard is 512.

     -fdeduce-init-list
         Enable deduction of a template type parameter as
         "std::initializer_list" from a brace-enclosed
         initializer list, i.e.

                 template <class T> auto forward(T t) -> decltype (realfn (t))
                 {
                   return realfn (t);
                 }

                 void f()
                 {
                   forward({1,2}); // call forward<std::initializer_list<int>>
                 }

         This deduction was implemented as a possible extension
         to the originally proposed semantics for the C++11
         standard, but was not part of the final standard, so it
         is disabled by default.  This option is deprecated, and
         may be removed in a future version of G++.

     -ffriend-injection

         Inject friend functions into the enclosing namespace, so
         that they are visible outside the scope of the class in
         which they are declared.  Friend functions were
         documented to work this way in the old Annotated C++
         Reference Manual, and versions of G++ before 4.1 always
         worked that way.  However, in ISO C++ a friend function
         that is not declared in an enclosing scope can only be
         found using argument dependent lookup.  This option
         causes friends to be injected as they were in earlier
         releases.

         This option is for compatibility, and may be removed in
         a future release of G++.

     -fno-elide-constructors
         The C++ standard allows an implementation to omit
         creating a temporary that is only used to initialize
         another object of the same type.  Specifying this option
         disables that optimization, and forces G++ to call the
         copy constructor in all cases.

     -fno-enforce-eh-specs
         Don't generate code to check for violation of exception
         specifications at run time.  This option violates the
         C++ standard, but may be useful for reducing code size
         in production builds, much like defining NDEBUG.  This
         does not give user code permission to throw exceptions
         in violation of the exception specifications; the
         compiler still optimizes based on the specifications, so
         throwing an unexpected exception results in undefined
         behavior at run time.

     -fextern-tls-init
     -fno-extern-tls-init
         The C++11 and OpenMP standards allow thread_local and
         threadprivate variables to have dynamic (runtime)
         initialization.  To support this, any use of such a
         variable goes through a wrapper function that performs
         any necessary initialization.  When the use and
         definition of the variable are in the same translation
         unit, this overhead can be optimized away, but when the
         use is in a different translation unit there is
         significant overhead even if the variable doesn't
         actually need dynamic initialization.  If the programmer
         can be sure that no use of the variable in a non-
         defining TU needs to trigger dynamic initialization
         (either because the variable is statically initialized,
         or a use of the variable in the defining TU will be
         executed before any uses in another TU), they can avoid
         this overhead with the -fno-extern-tls-init option.

         On targets that support symbol aliases, the default is
         -fextern-tls-init.  On targets that do not support
         symbol aliases, the default is -fno-extern-tls-init.

     -ffor-scope
     -fno-for-scope
         If -ffor-scope is specified, the scope of variables
         declared in a for-init-statement is limited to the for
         loop itself, as specified by the C++ standard.  If
         -fno-for-scope is specified, the scope of variables
         declared in a for-init-statement extends to the end of
         the enclosing scope, as was the case in old versions of
         G++, and other (traditional) implementations of C++.

         If neither flag is given, the default is to follow the
         standard, but to allow and give a warning for old-style
         code that would otherwise be invalid, or have different
         behavior.

     -fno-gnu-keywords
         Do not recognize "typeof" as a keyword, so that code can
         use this word as an identifier.  You can use the keyword
         "__typeof__" instead.  -ansi implies -fno-gnu-keywords.

     -fno-implicit-templates
         Never emit code for non-inline templates that are
         instantiated implicitly (i.e. by use); only emit code
         for explicit instantiations.

     -fno-implicit-inline-templates
         Don't emit code for implicit instantiations of inline
         templates, either.  The default is to handle inlines
         differently so that compiles with and without
         optimization need the same set of explicit
         instantiations.

     -fno-implement-inlines
         To save space, do not emit out-of-line copies of inline
         functions controlled by #pragma implementation.  This
         causes linker errors if these functions are not inlined
         everywhere they are called.

     -fms-extensions
         Disable Wpedantic warnings about constructs used in MFC,
         such as implicit int and getting a pointer to member
         function via non-standard syntax.

     -fno-nonansi-builtins
         Disable built-in declarations of functions that are not
         mandated by ANSI/ISO C.  These include "ffs", "alloca",
         "_exit", "index", "bzero", "conjf", and other related
         functions.

     -fnothrow-opt
         Treat a "throw()" exception specification as if it were
         a "noexcept" specification to reduce or eliminate the
         text size overhead relative to a function with no
         exception specification.  If the function has local
         variables of types with non-trivial destructors, the
         exception specification actually makes the function
         smaller because the EH cleanups for those variables can
         be optimized away.  The semantic effect is that an
         exception thrown out of a function with such an
         exception specification results in a call to "terminate"
         rather than "unexpected".

     -fno-operator-names
         Do not treat the operator name keywords "and", "bitand",
         "bitor", "compl", "not", "or" and "xor" as synonyms as
         keywords.

     -fno-optional-diags
         Disable diagnostics that the standard says a compiler
         does not need to issue.  Currently, the only such
         diagnostic issued by G++ is the one for a name having
         multiple meanings within a class.

     -fpermissive
         Downgrade some diagnostics about nonconformant code from
         errors to warnings.  Thus, using -fpermissive allows
         some nonconforming code to compile.

     -fno-pretty-templates
         When an error message refers to a specialization of a
         function template, the compiler normally prints the
         signature of the template followed by the template
         arguments and any typedefs or typenames in the signature
         (e.g. "void f(T) [with T = int]" rather than "void
         f(int)") so that it's clear which template is involved.
         When an error message refers to a specialization of a
         class template, the compiler omits any template
         arguments that match the default template arguments for
         that template.  If either of these behaviors make it
         harder to understand the error message rather than
         easier, you can use -fno-pretty-templates to disable
         them.

     -frepo
         Enable automatic template instantiation at link time.
         This option also implies -fno-implicit-templates.

     -fno-rtti
         Disable generation of information about every class with
         virtual functions for use by the C++ run-time type
         identification features (dynamic_cast and typeid).  If
         you don't use those parts of the language, you can save
         some space by using this flag.  Note that exception
         handling uses the same information, but G++ generates it
         as needed. The dynamic_cast operator can still be used
         for casts that do not require run-time type information,
         i.e. casts to "void *" or to unambiguous base classes.

     -fstats
         Emit statistics about front-end processing at the end of
         the compilation.  This information is generally only
         useful to the G++ development team.

     -fstrict-enums
         Allow the compiler to optimize using the assumption that
         a value of enumerated type can only be one of the values
         of the enumeration (as defined in the C++ standard;
         basically, a value that can be represented in the
         minimum number of bits needed to represent all the
         enumerators).  This assumption may not be valid if the
         program uses a cast to convert an arbitrary integer
         value to the enumerated type.

     -ftemplate-backtrace-limit=n
         Set the maximum number of template instantiation notes
         for a single warning or error to n.  The default value
         is 10.

     -ftemplate-depth=n
         Set the maximum instantiation depth for template classes
         to n.  A limit on the template instantiation depth is
         needed to detect endless recursions during template
         class instantiation.  ANSI/ISO C++ conforming programs
         must not rely on a maximum depth greater than 17
         (changed to 1024 in C++11).  The default value is 900,
         as the compiler can run out of stack space before
         hitting 1024 in some situations.

     -fno-threadsafe-statics
         Do not emit the extra code to use the routines specified
         in the C++ ABI for thread-safe initialization of local
         statics.  You can use this option to reduce code size
         slightly in code that doesn't need to be thread-safe.

     -fuse-cxa-atexit
         Register destructors for objects with static storage
         duration with the "__cxa_atexit" function rather than
         the "atexit" function.  This option is required for
         fully standards-compliant handling of static
         destructors, but only works if your C library supports
         "__cxa_atexit".

     -fno-use-cxa-get-exception-ptr

         Don't use the "__cxa_get_exception_ptr" runtime routine.
         This causes "std::uncaught_exception" to be incorrect,
         but is necessary if the runtime routine is not
         available.

     -fvisibility-inlines-hidden
         This switch declares that the user does not attempt to
         compare pointers to inline functions or methods where
         the addresses of the two functions are taken in
         different shared objects.

         The effect of this is that GCC may, effectively, mark
         inline methods with "__attribute__ ((visibility
         ("hidden")))" so that they do not appear in the export
         table of a DSO and do not require a PLT indirection when
         used within the DSO.  Enabling this option can have a
         dramatic effect on load and link times of a DSO as it
         massively reduces the size of the dynamic export table
         when the library makes heavy use of templates.

         The behavior of this switch is not quite the same as
         marking the methods as hidden directly, because it does
         not affect static variables local to the function or
         cause the compiler to deduce that the function is
         defined in only one shared object.

         You may mark a method as having a visibility explicitly
         to negate the effect of the switch for that method.  For
         example, if you do want to compare pointers to a
         particular inline method, you might mark it as having
         default visibility.  Marking the enclosing class with
         explicit visibility has no effect.

         Explicitly instantiated inline methods are unaffected by
         this option as their linkage might otherwise cross a
         shared library boundary.

     -fvisibility-ms-compat
         This flag attempts to use visibility settings to make
         GCC's C++ linkage model compatible with that of
         Microsoft Visual Studio.

         The flag makes these changes to GCC's linkage model:

         1.  It sets the default visibility to "hidden", like
             -fvisibility=hidden.

         2.  Types, but not their members, are not hidden by
             default.

         3.  The One Definition Rule is relaxed for types without
             explicit visibility specifications that are defined
             in more than one shared object: those declarations
             are permitted if they are permitted when this option
             is not used.

         In new code it is better to use -fvisibility=hidden and
         export those classes that are intended to be externally
         visible.  Unfortunately it is possible for code to rely,
         perhaps accidentally, on the Visual Studio behavior.

         Among the consequences of these changes are that static
         data members of the same type with the same name but
         defined in different shared objects are different, so
         changing one does not change the other; and that
         pointers to function members defined in different shared
         objects may not compare equal.  When this flag is given,
         it is a violation of the ODR to define types with the
         same name differently.

     -fno-weak
         Do not use weak symbol support, even if it is provided
         by the linker.  By default, G++ uses weak symbols if
         they are available.  This option exists only for
         testing, and should not be used by end-users; it results
         in inferior code and has no benefits.  This option may
         be removed in a future release of G++.

     -nostdinc++
         Do not search for header files in the standard
         directories specific to C++, but do still search the
         other standard directories.  (This option is used when
         building the C++ library.)

     In addition, these optimization, warning, and code
     generation options have meanings only for C++ programs:

     -fno-default-inline
         Do not assume inline for functions defined inside a
         class scope.
           Note that these functions have linkage like inline
         functions; they just aren't inlined by default.

     -Wabi (C, Objective-C, C++ and Objective-C++ only)
         Warn when G++ generates code that is probably not
         compatible with the vendor-neutral C++ ABI.  Although an
         effort has been made to warn about all such cases, there
         are probably some cases that are not warned about, even
         though G++ is generating incompatible code.  There may
         also be cases where warnings are emitted even though the
         code that is generated is compatible.

         You should rewrite your code to avoid these warnings if
         you are concerned about the fact that code generated by

         G++ may not be binary compatible with code generated by
         other compilers.

         The known incompatibilities in -fabi-version=2 (the
         default) include:

         *   A template with a non-type template parameter of
             reference type is mangled incorrectly:

                     extern int N;
                     template <int &> struct S {};
                     void n (S<N>) {2}

             This is fixed in -fabi-version=3.

         *   SIMD vector types declared using "__attribute
             ((vector_size))" are mangled in a non-standard way
             that does not allow for overloading of functions
             taking vectors of different sizes.

             The mangling is changed in -fabi-version=4.

         The known incompatibilities in -fabi-version=1 include:

         *   Incorrect handling of tail-padding for bit-fields.
             G++ may attempt to pack data into the same byte as a
             base class.  For example:

                     struct A { virtual void f(); int f1 : 1; };
                     struct B : public A { int f2 : 1; };

             In this case, G++ places "B::f2" into the same byte
             as "A::f1"; other compilers do not.  You can avoid
             this problem by explicitly padding "A" so that its
             size is a multiple of the byte size on your
             platform; that causes G++ and other compilers to lay
             out "B" identically.

         *   Incorrect handling of tail-padding for virtual
             bases.  G++ does not use tail padding when laying
             out virtual bases.  For example:

                     struct A { virtual void f(); char c1; };
                     struct B { B(); char c2; };
                     struct C : public A, public virtual B {};

             In this case, G++ does not place "B" into the tail-
             padding for "A"; other compilers do.  You can avoid
             this problem by explicitly padding "A" so that its
             size is a multiple of its alignment (ignoring
             virtual base classes); that causes G++ and other
             compilers to lay out "C" identically.

         *   Incorrect handling of bit-fields with declared
             widths greater than that of their underlying types,
             when the bit-fields appear in a union.  For example:

                     union U { int i : 4096; };

             Assuming that an "int" does not have 4096 bits, G++
             makes the union too small by the number of bits in
             an "int".

         *   Empty classes can be placed at incorrect offsets.
             For example:

                     struct A {};

                     struct B {
                       A a;
                       virtual void f ();
                     };

                     struct C : public B, public A {};

             G++ places the "A" base class of "C" at a nonzero
             offset; it should be placed at offset zero.  G++
             mistakenly believes that the "A" data member of "B"
             is already at offset zero.

         *   Names of template functions whose types involve
             "typename" or template template parameters can be
             mangled incorrectly.

                     template <typename Q>
                     void f(typename Q::X) {}

                     template <template <typename> class Q>
                     void f(typename Q<int>::X) {}

             Instantiations of these templates may be mangled
             incorrectly.

         It also warns about psABI-related changes.  The known
         psABI changes at this point include:

         *   For SysV/x86-64, unions with "long double" members
             are passed in memory as specified in psABI.  For
             example:

                     union U {
                       long double ld;
                       int i;
                     };

             "union U" is always passed in memory.

     -Wctor-dtor-privacy (C++ and Objective-C++ only)
         Warn when a class seems unusable because all the
         constructors or destructors in that class are private,
         and it has neither friends nor public static member
         functions.  Also warn if there are no non-private
         methods, and there's at least one private member
         function that isn't a constructor or destructor.

     -Wdelete-non-virtual-dtor (C++ and Objective-C++ only)
         Warn when delete is used to destroy an instance of a
         class that has virtual functions and non-virtual
         destructor. It is unsafe to delete an instance of a
         derived class through a pointer to a base class if the
         base class does not have a virtual destructor.  This
         warning is enabled by -Wall.

     -Wliteral-suffix (C++ and Objective-C++ only)
         Warn when a string or character literal is followed by a
         ud-suffix which does not begin with an underscore.  As a
         conforming extension, GCC treats such suffixes as
         separate preprocessing tokens in order to maintain
         backwards compatibility with code that uses formatting
         macros from "<inttypes.h>".  For example:

                 #define __STDC_FORMAT_MACROS
                 #include <inttypes.h>
                 #include <stdio.h>

                 int main() {
                   int64_t i64 = 123;
                   printf("My int64: %"PRId64"\n", i64);
                 }

         In this case, "PRId64" is treated as a separate
         preprocessing token.

         This warning is enabled by default.

     -Wnarrowing (C++ and Objective-C++ only)
         Warn when a narrowing conversion prohibited by C++11
         occurs within { }, e.g.

                 int i = { 2.2 }; // error: narrowing from double to int

         This flag is included in -Wall and -Wc++11-compat.

         With -std=c++11, -Wno-narrowing suppresses the
         diagnostic required by the standard.  Note that this
         does not affect the meaning of well-formed code;
         narrowing conversions are still considered ill-formed in

         SFINAE context.

     -Wnoexcept (C++ and Objective-C++ only)
         Warn when a noexcept-expression evaluates to false
         because of a call to a function that does not have a
         non-throwing exception specification (i.e. throw() or
         noexcept) but is known by the compiler to never throw an
         exception.

     -Wnon-virtual-dtor (C++ and Objective-C++ only)
         Warn when a class has virtual functions and an
         accessible non-virtual destructor, in which case it is
         possible but unsafe to delete an instance of a derived
         class through a pointer to the base class.  This warning
         is also enabled if -Weffc++ is specified.

     -Wreorder (C++ and Objective-C++ only)
         Warn when the order of member initializers given in the
         code does not match the order in which they must be
         executed.  For instance:

                 struct A {
                   int i;
                   int j;
                   A(): j (0), i (1) { }
                 };

         The compiler rearranges the member initializers for i
         and j to match the declaration order of the members,
         emitting a warning to that effect.  This warning is
         enabled by -Wall.

     -fext-numeric-literals (C++ and Objective-C++ only)
         Accept imaginary, fixed-point, or machine-defined
         literal number suffixes as GNU extensions.  When this
         option is turned off these suffixes are treated as C++11
         user-defined literal numeric suffixes.  This is on by
         default for all pre-C++11 dialects and all GNU dialects:
         -std=c++98, -std=gnu++98, -std=gnu++11, -std=gnu++1y.
         This option is off by default for ISO C++11 onwards
         (-std=c++11, ...).

     The following -W... options are not affected by -Wall.

     -Weffc++ (C++ and Objective-C++ only)
         Warn about violations of the following style guidelines
         from Scott Meyers' Effective C++, Second Edition book:

         *   Item 11:  Define a copy constructor and an
             assignment operator for classes with dynamically-
             allocated memory.

         *   Item 12:  Prefer initialization to assignment in
             constructors.

         *   Item 14:  Make destructors virtual in base classes.

         *   Item 15:  Have "operator=" return a reference to
             *this.

         *   Item 23:  Don't try to return a reference when you
             must return an object.

         Also warn about violations of the following style
         guidelines from Scott Meyers' More Effective C++ book:

         *   Item 6:  Distinguish between prefix and postfix
             forms of increment and decrement operators.

         *   Item 7:  Never overload "&&", "||", or ",".

         When selecting this option, be aware that the standard
         library headers do not obey all of these guidelines; use
         grep -v to filter out those warnings.

     -Wstrict-null-sentinel (C++ and Objective-C++ only)
         Warn about the use of an uncasted "NULL" as sentinel.
         When compiling only with GCC this is a valid sentinel,
         as "NULL" is defined to "__null".  Although it is a null
         pointer constant rather than a null pointer, it is
         guaranteed to be of the same size as a pointer.  But
         this use is not portable across different compilers.

     -Wno-non-template-friend (C++ and Objective-C++ only)
         Disable warnings when non-templatized friend functions
         are declared within a template.  Since the advent of
         explicit template specification support in G++, if the
         name of the friend is an unqualified-id (i.e., friend
         foo(int)), the C++ language specification demands that
         the friend declare or define an ordinary, nontemplate
         function.  (Section 14.5.3).  Before G++ implemented
         explicit specification, unqualified-ids could be
         interpreted as a particular specialization of a
         templatized function.  Because this non-conforming
         behavior is no longer the default behavior for G++,
         -Wnon-template-friend allows the compiler to check
         existing code for potential trouble spots and is on by
         default.  This new compiler behavior can be turned off
         with -Wno-non-template-friend, which keeps the
         conformant compiler code but disables the helpful
         warning.

     -Wold-style-cast (C++ and Objective-C++ only)
         Warn if an old-style (C-style) cast to a non-void type
         is used within a C++ program.  The new-style casts
         (dynamic_cast, static_cast, reinterpret_cast, and
         const_cast) are less vulnerable to unintended effects
         and much easier to search for.

     -Woverloaded-virtual (C++ and Objective-C++ only)
         Warn when a function declaration hides virtual functions
         from a base class.  For example, in:

                 struct A {
                   virtual void f();
                 };

                 struct B: public A {
                   void f(int);
                 };

         the "A" class version of "f" is hidden in "B", and code
         like:

                 B* b;
                 b->f();

         fails to compile.

     -Wno-pmf-conversions (C++ and Objective-C++ only)
         Disable the diagnostic for converting a bound pointer to
         member function to a plain pointer.

     -Wsign-promo (C++ and Objective-C++ only)
         Warn when overload resolution chooses a promotion from
         unsigned or enumerated type to a signed type, over a
         conversion to an unsigned type of the same size.
         Previous versions of G++ tried to preserve unsignedness,
         but the standard mandates the current behavior.

  Options Controlling Objective-C and Objective-C++ Dialects
     (NOTE: This manual does not describe the Objective-C and
     Objective-C++ languages themselves.

     This section describes the command-line options that are
     only meaningful for Objective-C and Objective-C++ programs.
     You can also use most of the language-independent GNU
     compiler options.  For example, you might compile a file
     "some_class.m" like this:

             gcc -g -fgnu-runtime -O -c some_class.m

     In this example, -fgnu-runtime is an option meant only for
     Objective-C and Objective-C++ programs; you can use the
     other options with any language supported by GCC.

     Note that since Objective-C is an extension of the C
     language, Objective-C compilations may also use options
     specific to the C front-end (e.g., -Wtraditional).
     Similarly, Objective-C++ compilations may use C++-specific
     options (e.g., -Wabi).

     Here is a list of options that are only for compiling
     Objective-C and Objective-C++ programs:

     -fconstant-string-class=class-name
         Use class-name as the name of the class to instantiate
         for each literal string specified with the syntax
         "@"..."".  The default class name is "NXConstantString"
         if the GNU runtime is being used, and "NSConstantString"
         if the NeXT runtime is being used (see below).  The
         -fconstant-cfstrings option, if also present, overrides
         the -fconstant-string-class setting and cause "@"...""
         literals to be laid out as constant CoreFoundation
         strings.

     -fgnu-runtime
         Generate object code compatible with the standard GNU
         Objective-C runtime.  This is the default for most types
         of systems.

     -fnext-runtime
         Generate output compatible with the NeXT runtime.  This
         is the default for NeXT-based systems, including Darwin
         and Mac OS X.  The macro "__NEXT_RUNTIME__" is
         predefined if (and only if) this option is used.

     -fno-nil-receivers
         Assume that all Objective-C message dispatches
         ("[receiver message:arg]") in this translation unit
         ensure that the receiver is not "nil".  This allows for
         more efficient entry points in the runtime to be used.
         This option is only available in conjunction with the
         NeXT runtime and ABI version 0 or 1.

     -fobjc-abi-version=n
         Use version n of the Objective-C ABI for the selected
         runtime.  This option is currently supported only for
         the NeXT runtime.  In that case, Version 0 is the
         traditional (32-bit) ABI without support for properties
         and other Objective-C 2.0 additions.  Version 1 is the
         traditional (32-bit) ABI with support for properties and
         other Objective-C 2.0 additions.  Version 2 is the
         modern (64-bit) ABI.  If nothing is specified, the
         default is Version 0 on 32-bit target machines, and
         Version 2 on 64-bit target machines.

     -fobjc-call-cxx-cdtors

         For each Objective-C class, check if any of its instance
         variables is a C++ object with a non-trivial default
         constructor.  If so, synthesize a special "- (id)
         .cxx_construct" instance method which runs non-trivial
         default constructors on any such instance variables, in
         order, and then return "self".  Similarly, check if any
         instance variable is a C++ object with a non-trivial
         destructor, and if so, synthesize a special "- (void)
         .cxx_destruct" method which runs all such default
         destructors, in reverse order.

         The "- (id) .cxx_construct" and "- (void) .cxx_destruct"
         methods thusly generated only operate on instance
         variables declared in the current Objective-C class, and
         not those inherited from superclasses.  It is the
         responsibility of the Objective-C runtime to invoke all
         such methods in an object's inheritance hierarchy.  The
         "- (id) .cxx_construct" methods are invoked by the
         runtime immediately after a new object instance is
         allocated; the "- (void) .cxx_destruct" methods are
         invoked immediately before the runtime deallocates an
         object instance.

         As of this writing, only the NeXT runtime on Mac OS X
         10.4 and later has support for invoking the "- (id)
         .cxx_construct" and "- (void) .cxx_destruct" methods.

     -fobjc-direct-dispatch
         Allow fast jumps to the message dispatcher.  On Darwin
         this is accomplished via the comm page.

     -fobjc-exceptions
         Enable syntactic support for structured exception
         handling in Objective-C, similar to what is offered by
         C++ and Java.  This option is required to use the
         Objective-C keywords @try, @throw, @catch, @finally and
         @synchronized.  This option is available with both the
         GNU runtime and the NeXT runtime (but not available in
         conjunction with the NeXT runtime on Mac OS X 10.2 and
         earlier).

     -fobjc-gc
         Enable garbage collection (GC) in Objective-C and
         Objective-C++ programs.  This option is only available
         with the NeXT runtime; the GNU runtime has a different
         garbage collection implementation that does not require
         special compiler flags.

     -fobjc-nilcheck
         For the NeXT runtime with version 2 of the ABI, check
         for a nil receiver in method invocations before doing
         the actual method call.  This is the default and can be
         disabled using -fno-objc-nilcheck.  Class methods and
         super calls are never checked for nil in this way no
         matter what this flag is set to.  Currently this flag
         does nothing when the GNU runtime, or an older version
         of the NeXT runtime ABI, is used.

     -fobjc-std=objc1
         Conform to the language syntax of Objective-C 1.0, the
         language recognized by GCC 4.0.  This only affects the
         Objective-C additions to the C/C++ language; it does not
         affect conformance to C/C++ standards, which is
         controlled by the separate C/C++ dialect option flags.
         When this option is used with the Objective-C or
         Objective-C++ compiler, any Objective-C syntax that is
         not recognized by GCC 4.0 is rejected.  This is useful
         if you need to make sure that your Objective-C code can
         be compiled with older versions of GCC.

     -freplace-objc-classes
         Emit a special marker instructing ld(1) not to
         statically link in the resulting object file, and allow
         dyld(1) to load it in at run time instead.  This is used
         in conjunction with the Fix-and-Continue debugging mode,
         where the object file in question may be recompiled and
         dynamically reloaded in the course of program execution,
         without the need to restart the program itself.
         Currently, Fix-and-Continue functionality is only
         available in conjunction with the NeXT runtime on Mac OS
         X 10.3 and later.

     -fzero-link
         When compiling for the NeXT runtime, the compiler
         ordinarily replaces calls to "objc_getClass("...")"
         (when the name of the class is known at compile time)
         with static class references that get initialized at
         load time, which improves run-time performance.
         Specifying the -fzero-link flag suppresses this behavior
         and causes calls to "objc_getClass("...")"  to be
         retained.  This is useful in Zero-Link debugging mode,
         since it allows for individual class implementations to
         be modified during program execution.  The GNU runtime
         currently always retains calls to
         "objc_get_class("...")"  regardless of command-line
         options.

     -gen-decls
         Dump interface declarations for all classes seen in the
         source file to a file named sourcename.decl.

     -Wassign-intercept (Objective-C and Objective-C++ only)
         Warn whenever an Objective-C assignment is being
         intercepted by the garbage collector.

     -Wno-protocol (Objective-C and Objective-C++ only)
         If a class is declared to implement a protocol, a
         warning is issued for every method in the protocol that
         is not implemented by the class.  The default behavior
         is to issue a warning for every method not explicitly
         implemented in the class, even if a method
         implementation is inherited from the superclass.  If you
         use the -Wno-protocol option, then methods inherited
         from the superclass are considered to be implemented,
         and no warning is issued for them.

     -Wselector (Objective-C and Objective-C++ only)
         Warn if multiple methods of different types for the same
         selector are found during compilation.  The check is
         performed on the list of methods in the final stage of
         compilation.  Additionally, a check is performed for
         each selector appearing in a "@selector(...)"
         expression, and a corresponding method for that selector
         has been found during compilation.  Because these checks
         scan the method table only at the end of compilation,
         these warnings are not produced if the final stage of
         compilation is not reached, for example because an error
         is found during compilation, or because the
         -fsyntax-only option is being used.

     -Wstrict-selector-match (Objective-C and Objective-C++ only)
         Warn if multiple methods with differing argument and/or
         return types are found for a given selector when
         attempting to send a message using this selector to a
         receiver of type "id" or "Class".  When this flag is off
         (which is the default behavior), the compiler omits such
         warnings if any differences found are confined to types
         that share the same size and alignment.

     -Wundeclared-selector (Objective-C and Objective-C++ only)
         Warn if a "@selector(...)" expression referring to an
         undeclared selector is found.  A selector is considered
         undeclared if no method with that name has been declared
         before the "@selector(...)" expression, either
         explicitly in an @interface or @protocol declaration, or
         implicitly in an @implementation section.  This option
         always performs its checks as soon as a "@selector(...)"
         expression is found, while -Wselector only performs its
         checks in the final stage of compilation.  This also
         enforces the coding style convention that methods and
         selectors must be declared before being used.

     -print-objc-runtime-info
         Generate C header describing the largest structure that
         is passed by value, if any.

  Options to Control Diagnostic Messages Formatting
     Traditionally, diagnostic messages have been formatted
     irrespective of the output device's aspect (e.g. its width,
     ...).  You can use the options described below to control
     the formatting algorithm for diagnostic messages, e.g. how
     many characters per line, how often source location
     information should be reported.  Note that some language
     front ends may not honor these options.

     -fmessage-length=n
         Try to format error messages so that they fit on lines
         of about n characters.  The default is 72 characters for
         g++ and 0 for the rest of the front ends supported by
         GCC.  If n is zero, then no line-wrapping is done; each
         error message appears on a single line.

     -fdiagnostics-show-location=once
         Only meaningful in line-wrapping mode.  Instructs the
         diagnostic messages reporter to emit source location
         information once; that is, in case the message is too
         long to fit on a single physical line and has to be
         wrapped, the source location won't be emitted (as
         prefix) again, over and over, in subsequent continuation
         lines.  This is the default behavior.

     -fdiagnostics-show-location=every-line
         Only meaningful in line-wrapping mode.  Instructs the
         diagnostic messages reporter to emit the same source
         location information (as prefix) for physical lines that
         result from the process of breaking a message which is
         too long to fit on a single line.

     -fno-diagnostics-show-option
         By default, each diagnostic emitted includes text
         indicating the command-line option that directly
         controls the diagnostic (if such an option is known to
         the diagnostic machinery).  Specifying the
         -fno-diagnostics-show-option flag suppresses that
         behavior.

     -fno-diagnostics-show-caret
         By default, each diagnostic emitted includes the
         original source line and a caret `^' indicating the
         column.  This option suppresses this information.

  Options to Request or Suppress Warnings
     Warnings are diagnostic messages that report constructions
     that are not inherently erroneous but that are risky or
     suggest there may have been an error.

     The following language-independent options do not enable
     specific warnings but control the kinds of diagnostics
     produced by GCC.

     -fsyntax-only
         Check the code for syntax errors, but don't do anything
         beyond that.

     -fmax-errors=n
         Limits the maximum number of error messages to n, at
         which point GCC bails out rather than attempting to
         continue processing the source code.  If n is 0 (the
         default), there is no limit on the number of error
         messages produced.  If -Wfatal-errors is also specified,
         then -Wfatal-errors takes precedence over this option.

     -w  Inhibit all warning messages.

     -Werror
         Make all warnings into errors.

     -Werror=
         Make the specified warning into an error.  The specifier
         for a warning is appended; for example -Werror=switch
         turns the warnings controlled by -Wswitch into errors.
         This switch takes a negative form, to be used to negate
         -Werror for specific warnings; for example
         -Wno-error=switch makes -Wswitch warnings not be errors,
         even when -Werror is in effect.

         The warning message for each controllable warning
         includes the option that controls the warning.  That
         option can then be used with -Werror= and -Wno-error= as
         described above.  (Printing of the option in the warning
         message can be disabled using the
         -fno-diagnostics-show-option flag.)

         Note that specifying -Werror=foo automatically implies
         -Wfoo.  However, -Wno-error=foo does not imply anything.

     -Wfatal-errors
         This option causes the compiler to abort compilation on
         the first error occurred rather than trying to keep
         going and printing further error messages.

     You can request many specific warnings with options
     beginning with -W, for example -Wimplicit to request
     warnings on implicit declarations.  Each of these specific
     warning options also has a negative form beginning -Wno- to
     turn off warnings; for example, -Wno-implicit.  This manual
     lists only one of the two forms, whichever is not the
     default.  For further language-specific options also refer
     to C++ Dialect Options and Objective-C and Objective-C++
     Dialect Options.

     When an unrecognized warning option is requested (e.g.,
     -Wunknown-warning), GCC emits a diagnostic stating that the
     option is not recognized.  However, if the -Wno- form is
     used, the behavior is slightly different: no diagnostic is
     produced for -Wno-unknown-warning unless other diagnostics
     are being produced.  This allows the use of new -Wno-
     options with old compilers, but if something goes wrong, the
     compiler warns that an unrecognized option is present.

     -Wpedantic
     -pedantic
         Issue all the warnings demanded by strict ISO C and ISO
         C++; reject all programs that use forbidden extensions,
         and some other programs that do not follow ISO C and ISO
         C++.  For ISO C, follows the version of the ISO C
         standard specified by any -std option used.

         Valid ISO C and ISO C++ programs should compile properly
         with or without this option (though a rare few require
         -ansi or a -std option specifying the required version
         of ISO C).  However, without this option, certain GNU
         extensions and traditional C and C++ features are
         supported as well.  With this option, they are rejected.

         -Wpedantic does not cause warning messages for use of
         the alternate keywords whose names begin and end with
         __.  Pedantic warnings are also disabled in the
         expression that follows "__extension__".  However, only
         system header files should use these escape routes;
         application programs should avoid them.

         Some users try to use -Wpedantic to check programs for
         strict ISO C conformance.  They soon find that it does
         not do quite what they want:  it finds some non-ISO
         practices, but not all---only those for which ISO C
         requires a diagnostic, and some others for which
         diagnostics have been added.

         A feature to report any failure to conform to ISO C
         might be useful in some instances, but would require
         considerable additional work and would be quite
         different from -Wpedantic.  We don't have plans to
         support such a feature in the near future.

         Where the standard specified with -std represents a GNU
         extended dialect of C, such as gnu90 or gnu99, there is
         a corresponding base standard, the version of ISO C on
         which the GNU extended dialect is based.  Warnings from
         -Wpedantic are given where they are required by the base
         standard.  (It does not make sense for such warnings to
         be given only for features not in the specified GNU C
         dialect, since by definition the GNU dialects of C
         include all features the compiler supports with the
         given option, and there would be nothing to warn about.)

     -pedantic-errors
         Like -Wpedantic, except that errors are produced rather
         than warnings.

     -Wall
         This enables all the warnings about constructions that
         some users consider questionable, and that are easy to
         avoid (or modify to prevent the warning), even in
         conjunction with macros.  This also enables some
         language-specific warnings described in C++ Dialect
         Options and Objective-C and Objective-C++ Dialect
         Options.

         -Wall turns on the following warning flags:

         -Waddress -Warray-bounds (only with -O2) -Wc++11-compat
         -Wchar-subscripts -Wenum-compare (in C/ObjC; this is on
         by default in C++) -Wimplicit-int (C and Objective-C
         only) -Wimplicit-function-declaration (C and Objective-C
         only) -Wcomment -Wformat -Wmain (only for C/ObjC and
         unless -ffreestanding) -Wmaybe-uninitialized
         -Wmissing-braces (only for C/ObjC) -Wnonnull
         -Wparentheses -Wpointer-sign -Wreorder -Wreturn-type
         -Wsequence-point -Wsign-compare (only in C++)
         -Wstrict-aliasing -Wstrict-overflow=1 -Wswitch
         -Wtrigraphs -Wuninitialized -Wunknown-pragmas
         -Wunused-function -Wunused-label -Wunused-value
         -Wunused-variable -Wvolatile-register-var

         Note that some warning flags are not implied by -Wall.
         Some of them warn about constructions that users
         generally do not consider questionable, but which
         occasionally you might wish to check for; others warn
         about constructions that are necessary or hard to avoid
         in some cases, and there is no simple way to modify the
         code to suppress the warning. Some of them are enabled
         by -Wextra but many of them must be enabled
         individually.

     -Wextra
         This enables some extra warning flags that are not
         enabled by -Wall. (This option used to be called -W.
         The older name is still supported, but the newer name is
         more descriptive.)

         -Wclobbered -Wempty-body -Wignored-qualifiers
         -Wmissing-field-initializers -Wmissing-parameter-type (C
         only) -Wold-style-declaration (C only) -Woverride-init
         -Wsign-compare -Wtype-limits -Wuninitialized
         -Wunused-parameter (only with -Wunused or -Wall)
         -Wunused-but-set-parameter (only with -Wunused or -Wall)

         The option -Wextra also prints warning messages for the
         following cases:

         *   A pointer is compared against integer zero with <,
             <=, >, or >=.

         *   (C++ only) An enumerator and a non-enumerator both
             appear in a conditional expression.

         *   (C++ only) Ambiguous virtual bases.

         *   (C++ only) Subscripting an array that has been
             declared register.

         *   (C++ only) Taking the address of a variable that has
             been declared register.

         *   (C++ only) A base class is not initialized in a
             derived class's copy constructor.

     -Wchar-subscripts
         Warn if an array subscript has type "char".  This is a
         common cause of error, as programmers often forget that
         this type is signed on some machines.  This warning is
         enabled by -Wall.

     -Wcomment
         Warn whenever a comment-start sequence /* appears in a
         /* comment, or whenever a Backslash-Newline appears in a
         // comment.  This warning is enabled by -Wall.

     -Wno-coverage-mismatch
         Warn if feedback profiles do not match when using the
         -fprofile-use option.  If a source file is changed
         between compiling with -fprofile-gen and with
         -fprofile-use, the files with the profile feedback can
         fail to match the source file and GCC cannot use the
         profile feedback information.  By default, this warning
         is enabled and is treated as an error.
         -Wno-coverage-mismatch can be used to disable the
         warning or -Wno-error=coverage-mismatch can be used to
         disable the error.  Disabling the error for this warning
         can result in poorly optimized code and is useful only
         in the case of very minor changes such as bug fixes to
         an existing code-base.  Completely disabling the warning
         is not recommended.

     -Wno-cpp
         (C, Objective-C, C++, Objective-C++ and Fortran only)

         Suppress warning messages emitted by "#warning"
         directives.

     -Wdouble-promotion (C, C++, Objective-
         C and Objective-C++ only)
         Give a warning when a value of type "float" is
         implicitly promoted to "double".  CPUs with a 32-bit
         "single-precision" floating-point unit implement "float"
         in hardware, but emulate "double" in software.  On such
         a machine, doing computations using "double" values is
         much more expensive because of the overhead required for
         software emulation.

         It is easy to accidentally do computations with "double"
         because floating-point literals are implicitly of type
         "double".  For example, in:

                 float area(float radius)
                 {
                    return 3.14159 * radius * radius;
                 }

         the compiler performs the entire computation with
         "double" because the floating-point literal is a
         "double".

     -Wformat
     -Wformat=n
         Check calls to "printf" and "scanf", etc., to make sure
         that the arguments supplied have types appropriate to
         the format string specified, and that the conversions
         specified in the format string make sense.  This
         includes standard functions, and others specified by
         format attributes, in the "printf", "scanf", "strftime"
         and "strfmon" (an X/Open extension, not in the C
         standard) families (or other target-specific families).
         Which functions are checked without format attributes
         having been specified depends on the standard version
         selected, and such checks of functions without the
         attribute specified are disabled by -ffreestanding or
         -fno-builtin.

         The formats are checked against the format features
         supported by GNU libc version 2.2.  These include all
         ISO C90 and C99 features, as well as features from the
         Single Unix Specification and some BSD and GNU
         extensions.  Other library implementations may not
         support all these features; GCC does not support warning
         about features that go beyond a particular library's
         limitations.  However, if -Wpedantic is used with
         -Wformat, warnings are given about format features not
         in the selected standard version (but not for "strfmon"
         formats, since those are not in any version of the C
         standard).

         -Wformat=1
         -Wformat
             Option -Wformat is equivalent to -Wformat=1, and
             -Wno-format is equivalent to -Wformat=0.  Since
             -Wformat also checks for null format arguments for
             several functions, -Wformat also implies -Wnonnull.
             Some aspects of this level of format checking can be
             disabled by the options: -Wno-format-contains-nul,
             -Wno-format-extra-args, and -Wno-format-zero-length.
             -Wformat is enabled by -Wall.

         -Wno-format-contains-nul
             If -Wformat is specified, do not warn about format
             strings that contain NUL bytes.

         -Wno-format-extra-args
             If -Wformat is specified, do not warn about excess
             arguments to a "printf" or "scanf" format function.
             The C standard specifies that such arguments are
             ignored.

             Where the unused arguments lie between used
             arguments that are specified with $ operand number
             specifications, normally warnings are still given,
             since the implementation could not know what type to
             pass to "va_arg" to skip the unused arguments.
             However, in the case of "scanf" formats, this option
             suppresses the warning if the unused arguments are
             all pointers, since the Single Unix Specification
             says that such unused arguments are allowed.

         -Wno-format-zero-length
             If -Wformat is specified, do not warn about zero-
             length formats.  The C standard specifies that
             zero-length formats are allowed.

         -Wformat=2
             Enable -Wformat plus additional format checks.
             Currently equivalent to -Wformat -Wformat-nonliteral
             -Wformat-security -Wformat-y2k.

         -Wformat-nonliteral
             If -Wformat is specified, also warn if the format
             string is not a string literal and so cannot be
             checked, unless the format function takes its format
             arguments as a "va_list".

         -Wformat-security
             If -Wformat is specified, also warn about uses of
             format functions that represent possible security
             problems.  At present, this warns about calls to
             "printf" and "scanf" functions where the format
             string is not a string literal and there are no
             format arguments, as in "printf (foo);".  This may
             be a security hole if the format string came from
             untrusted input and contains %n.  (This is currently
             a subset of what -Wformat-nonliteral warns about,
             but in future warnings may be added to
             -Wformat-security that are not included in
             -Wformat-nonliteral.)

         -Wformat-y2k
             If -Wformat is specified, also warn about "strftime"
             formats that may yield only a two-digit year.

     -Wnonnull
         Warn about passing a null pointer for arguments marked
         as requiring a non-null value by the "nonnull" function
         attribute.

         -Wnonnull is included in -Wall and -Wformat.  It can be
         disabled with the -Wno-nonnull option.

     -Winit-self (C, C++, Objective-C and Objective-C++ only)
         Warn about uninitialized variables that are initialized
         with themselves.  Note this option can only be used with
         the -Wuninitialized option.

         For example, GCC warns about "i" being uninitialized in
         the following snippet only when -Winit-self has been
         specified:

                 int f()
                 {
                   int i = i;
                   return i;
                 }

         This warning is enabled by -Wall in C++.

     -Wimplicit-int (C and Objective-C only)
         Warn when a declaration does not specify a type.  This
         warning is enabled by -Wall.

     -Wimplicit-function-declaration (C and Objective-C only)
         Give a warning whenever a function is used before being
         declared. In C99 mode (-std=c99 or -std=gnu99), this
         warning is enabled by default and it is made into an
         error by -pedantic-errors. This warning is also enabled
         by -Wall.

     -Wimplicit (C and Objective-C only)
         Same as -Wimplicit-int and
         -Wimplicit-function-declaration.  This warning is
         enabled by -Wall.

     -Wignored-qualifiers (C and C++ only)
         Warn if the return type of a function has a type
         qualifier such as "const".  For ISO C such a type
         qualifier has no effect, since the value returned by a
         function is not an lvalue.  For C++, the warning is only
         emitted for scalar types or "void".  ISO C prohibits
         qualified "void" return types on function definitions,
         so such return types always receive a warning even
         without this option.

         This warning is also enabled by -Wextra.

     -Wmain
         Warn if the type of main is suspicious.  main should be
         a function with external linkage, returning int, taking
         either zero arguments, two, or three arguments of
         appropriate types.  This warning is enabled by default
         in C++ and is enabled by either -Wall or -Wpedantic.

     -Wmissing-braces
         Warn if an aggregate or union initializer is not fully
         bracketed.  In the following example, the initializer
         for a is not fully bracketed, but that for b is fully
         bracketed.  This warning is enabled by -Wall in C.

                 int a[2][2] = { 0, 1, 2, 3 };
                 int b[2][2] = { { 0, 1 }, { 2, 3 } };

         This warning is enabled by -Wall.

only)
     -Wmissing-include-dirs (C, C++, Objective-
         C and Objective-C++
         Warn if a user-supplied include directory does not
         exist.

     -Wparentheses
         Warn if parentheses are omitted in certain contexts,
         such as when there is an assignment in a context where a
         truth value is expected, or when operators are nested
         whose precedence people often get confused about.

         Also warn if a comparison like x<=y<=z appears; this is
         equivalent to (x<=y ? 1 : 0) <= z, which is a different
         interpretation from that of ordinary mathematical
         notation.

         Also warn about constructions where there may be
         confusion to which "if" statement an "else" branch
         belongs.  Here is an example of such a case:

                 {
                   if (a)
                     if (b)
                       foo ();
                   else
                     bar ();
                 }

         In C/C++, every "else" branch belongs to the innermost
         possible "if" statement, which in this example is "if
         (b)".  This is often not what the programmer expected,
         as illustrated in the above example by indentation the
         programmer chose.  When there is the potential for this
         confusion, GCC issues a warning when this flag is
         specified.  To eliminate the warning, add explicit
         braces around the innermost "if" statement so there is
         no way the "else" can belong to the enclosing "if".  The
         resulting code looks like this:

                 {
                   if (a)
                     {
                       if (b)
                         foo ();
                       else
                         bar ();
                     }
                 }

         Also warn for dangerous uses of the GNU extension to
         "?:" with omitted middle operand. When the condition in
         the "?": operator is a boolean expression, the omitted
         value is always 1.  Often programmers expect it to be a
         value computed inside the conditional expression
         instead.

         This warning is enabled by -Wall.

     -Wsequence-point
         Warn about code that may have undefined semantics
         because of violations of sequence point rules in the C
         and C++ standards.

         The C and C++ standards define the order in which
         expressions in a C/C++ program are evaluated in terms of
         sequence points, which represent a partial ordering
         between the execution of parts of the program: those
         executed before the sequence point, and those executed
         after it.  These occur after the evaluation of a full
         expression (one which is not part of a larger
         expression), after the evaluation of the first operand
         of a "&&", "||", "? :" or "," (comma) operator, before a
         function is called (but after the evaluation of its
         arguments and the expression denoting the called
         function), and in certain other places.  Other than as
         expressed by the sequence point rules, the order of
         evaluation of subexpressions of an expression is not
         specified.  All these rules describe only a partial
         order rather than a total order, since, for example, if
         two functions are called within one expression with no
         sequence point between them, the order in which the
         functions are called is not specified.  However, the
         standards committee have ruled that function calls do
         not overlap.

         It is not specified when between sequence points
         modifications to the values of objects take effect.
         Programs whose behavior depends on this have undefined
         behavior; the C and C++ standards specify that "Between
         the previous and next sequence point an object shall
         have its stored value modified at most once by the
         evaluation of an expression.  Furthermore, the prior
         value shall be read only to determine the value to be
         stored.".  If a program breaks these rules, the results
         on any particular implementation are entirely
         unpredictable.

         Examples of code with undefined behavior are "a = a++;",
         "a[n] = b[n++]" and "a[i++] = i;".  Some more
         complicated cases are not diagnosed by this option, and
         it may give an occasional false positive result, but in
         general it has been found fairly effective at detecting
         this sort of problem in programs.

         The standard is worded confusingly, therefore there is
         some debate over the precise meaning of the sequence
         point rules in subtle cases.  Links to discussions of
         the problem, including proposed formal definitions, may
         be found on the GCC readings page, at
         <http://gcc.gnu.org/readings.html>.

         This warning is enabled by -Wall for C and C++.

     -Wno-return-local-addr
         Do not warn about returning a pointer (or in C++, a
         reference) to a variable that goes out of scope after
         the function returns.

     -Wreturn-type
         Warn whenever a function is defined with a return type
         that defaults to "int".  Also warn about any "return"
         statement with no return value in a function whose
         return type is not "void" (falling off the end of the
         function body is considered returning without a value),
         and about a "return" statement with an expression in a
         function whose return type is "void".

         For C++, a function without return type always produces
         a diagnostic message, even when -Wno-return-type is
         specified.  The only exceptions are main and functions
         defined in system headers.

         This warning is enabled by -Wall.

     -Wswitch
         Warn whenever a "switch" statement has an index of
         enumerated type and lacks a "case" for one or more of
         the named codes of that enumeration.  (The presence of a
         "default" label prevents this warning.)  "case" labels
         outside the enumeration range also provoke warnings when
         this option is used (even if there is a "default"
         label).  This warning is enabled by -Wall.

     -Wswitch-default
         Warn whenever a "switch" statement does not have a
         "default" case.

     -Wswitch-enum
         Warn whenever a "switch" statement has an index of
         enumerated type and lacks a "case" for one or more of
         the named codes of that enumeration.  "case" labels
         outside the enumeration range also provoke warnings when
         this option is used.  The only difference between
         -Wswitch and this option is that this option gives a
         warning about an omitted enumeration code even if there
         is a "default" label.

     -Wsync-nand (C and C++ only)
         Warn when "__sync_fetch_and_nand" and
         "__sync_nand_and_fetch" built-in functions are used.
         These functions changed semantics in GCC 4.4.

     -Wtrigraphs
         Warn if any trigraphs are encountered that might change
         the meaning of the program (trigraphs within comments
         are not warned about).  This warning is enabled by
         -Wall.

     -Wunused-but-set-parameter
         Warn whenever a function parameter is assigned to, but
         otherwise unused (aside from its declaration).

         To suppress this warning use the unused attribute.

         This warning is also enabled by -Wunused together with
         -Wextra.

     -Wunused-but-set-variable
         Warn whenever a local variable is assigned to, but
         otherwise unused (aside from its declaration).  This
         warning is enabled by -Wall.

         To suppress this warning use the unused attribute.

         This warning is also enabled by -Wunused, which is
         enabled by -Wall.

     -Wunused-function
         Warn whenever a static function is declared but not
         defined or a non-inline static function is unused.  This
         warning is enabled by -Wall.

     -Wunused-label
         Warn whenever a label is declared but not used.  This
         warning is enabled by -Wall.

         To suppress this warning use the unused attribute.

only)
     -Wunused-local-typedefs (C, Objective-
         C, C++ and Objective-C++
         Warn when a typedef locally defined in a function is not
         used.  This warning is enabled by -Wall.

     -Wunused-parameter
         Warn whenever a function parameter is unused aside from
         its declaration.

         To suppress this warning use the unused attribute.

     -Wno-unused-result
         Do not warn if a caller of a function marked with
         attribute "warn_unused_result" does not use its return
         value. The default is -Wunused-result.

     -Wunused-variable
         Warn whenever a local variable or non-constant static
         variable is unused aside from its declaration.  This
         warning is enabled by -Wall.

         To suppress this warning use the unused attribute.

     -Wunused-value
         Warn whenever a statement computes a result that is
         explicitly not used. To suppress this warning cast the
         unused expression to void. This includes an expression-
         statement or the left-hand side of a comma expression
         that contains no side effects. For example, an
         expression such as x[i,j] causes a warning, while
         x[(void)i,j] does not.

         This warning is enabled by -Wall.

     -Wunused
         All the above -Wunused options combined.

         In order to get a warning about an unused function
         parameter, you must either specify -Wextra -Wunused
         (note that -Wall implies -Wunused), or separately
         specify -Wunused-parameter.

     -Wuninitialized
         Warn if an automatic variable is used without first
         being initialized or if a variable may be clobbered by a
         "setjmp" call. In C++, warn if a non-static reference or
         non-static const member appears in a class without
         constructors.

         If you want to warn about code that uses the
         uninitialized value of the variable in its own
         initializer, use the -Winit-self option.

         These warnings occur for individual uninitialized or
         clobbered elements of structure, union or array
         variables as well as for variables that are
         uninitialized or clobbered as a whole.  They do not
         occur for variables or elements declared "volatile".
         Because these warnings depend on optimization, the exact
         variables or elements for which there are warnings
         depends on the precise optimization options and version
         of GCC used.

         Note that there may be no warning about a variable that
         is used only to compute a value that itself is never
         used, because such computations may be deleted by data
         flow analysis before the warnings are printed.

     -Wmaybe-uninitialized
         For an automatic variable, if there exists a path from
         the function entry to a use of the variable that is
         initialized, but there exist some other paths for which
         the variable is not initialized, the compiler emits a
         warning if it cannot prove the uninitialized paths are
         not executed at run time. These warnings are made
         optional because GCC is not smart enough to see all the
         reasons why the code might be correct in spite of
         appearing to have an error.  Here is one example of how
         this can happen:

                 {
                   int x;
                   switch (y)
                     {
                     case 1: x = 1;
                       break;
                     case 2: x = 4;
                       break;
                     case 3: x = 5;
                     }
                   foo (x);
                 }

         If the value of "y" is always 1, 2 or 3, then "x" is
         always initialized, but GCC doesn't know this. To
         suppress the warning, you need to provide a default case
         with assert(0) or similar code.

         This option also warns when a non-volatile automatic
         variable might be changed by a call to "longjmp".  These
         warnings as well are possible only in optimizing
         compilation.

         The compiler sees only the calls to "setjmp".  It cannot
         know where "longjmp" will be called; in fact, a signal
         handler could call it at any point in the code.  As a
         result, you may get a warning even when there is in fact
         no problem because "longjmp" cannot in fact be called at
         the place that would cause a problem.

         Some spurious warnings can be avoided if you declare all
         the functions you use that never return as "noreturn".

         This warning is enabled by -Wall or -Wextra.

     -Wunknown-pragmas
         Warn when a "#pragma" directive is encountered that is
         not understood by GCC.  If this command-line option is
         used, warnings are even issued for unknown pragmas in
         system header files.  This is not the case if the
         warnings are only enabled by the -Wall command-line
         option.

     -Wno-pragmas
         Do not warn about misuses of pragmas, such as incorrect
         parameters, invalid syntax, or conflicts between
         pragmas.  See also -Wunknown-pragmas.

     -Wstrict-aliasing

         This option is only active when -fstrict-aliasing is
         active.  It warns about code that might break the strict
         aliasing rules that the compiler is using for
         optimization.  The warning does not catch all cases, but
         does attempt to catch the more common pitfalls.  It is
         included in -Wall.  It is equivalent to
         -Wstrict-aliasing=3

     -Wstrict-aliasing=n
         This option is only active when -fstrict-aliasing is
         active.  It warns about code that might break the strict
         aliasing rules that the compiler is using for
         optimization.  Higher levels correspond to higher
         accuracy (fewer false positives).  Higher levels also
         correspond to more effort, similar to the way -O works.
         -Wstrict-aliasing is equivalent to -Wstrict-aliasing=3.

         Level 1: Most aggressive, quick, least accurate.
         Possibly useful when higher levels do not warn but
         -fstrict-aliasing still breaks the code, as it has very
         few false negatives.  However, it has many false
         positives.  Warns for all pointer conversions between
         possibly incompatible types, even if never dereferenced.
         Runs in the front end only.

         Level 2: Aggressive, quick, not too precise.  May still
         have many false positives (not as many as level 1
         though), and few false negatives (but possibly more than
         level 1).  Unlike level 1, it only warns when an address
         is taken.  Warns about incomplete types.  Runs in the
         front end only.

         Level 3 (default for -Wstrict-aliasing):  Should have
         very few false positives and few false negatives.
         Slightly slower than levels 1 or 2 when optimization is
         enabled.  Takes care of the common pun+dereference
         pattern in the front end:  "*(int*)&some_float".  If
         optimization is enabled, it also runs in the back end,
         where it deals with multiple statement cases using
         flow-sensitive points-to information.  Only warns when
         the converted pointer is dereferenced.  Does not warn
         about incomplete types.

     -Wstrict-overflow
     -Wstrict-overflow=n
         This option is only active when -fstrict-overflow is
         active.  It warns about cases where the compiler
         optimizes based on the assumption that signed overflow
         does not occur.  Note that it does not warn about all
         cases where the code might overflow: it only warns about
         cases where the compiler implements some optimization.
         Thus this warning depends on the optimization level.

         An optimization that assumes that signed overflow does
         not occur is perfectly safe if the values of the
         variables involved are such that overflow never does, in
         fact, occur.  Therefore this warning can easily give a
         false positive: a warning about code that is not
         actually a problem.  To help focus on important issues,
         several warning levels are defined.  No warnings are
         issued for the use of undefined signed overflow when
         estimating how many iterations a loop requires, in
         particular when determining whether a loop will be
         executed at all.

         -Wstrict-overflow=1
             Warn about cases that are both questionable and easy
             to avoid.  For example,  with -fstrict-overflow, the
             compiler simplifies "x + 1 > x" to 1.  This level of
             -Wstrict-overflow is enabled by -Wall; higher levels
             are not, and must be explicitly requested.

         -Wstrict-overflow=2
             Also warn about other cases where a comparison is
             simplified to a constant.  For example: "abs (x) >=
             0".  This can only be simplified when
             -fstrict-overflow is in effect, because "abs
             (INT_MIN)" overflows to "INT_MIN", which is less
             than zero.  -Wstrict-overflow (with no level) is the
             same as -Wstrict-overflow=2.

         -Wstrict-overflow=3
             Also warn about other cases where a comparison is
             simplified.  For example: "x + 1 > 1" is simplified
             to "x > 0".

         -Wstrict-overflow=4
             Also warn about other simplifications not covered by
             the above cases.  For example: "(x * 10) / 5" is
             simplified to "x * 2".

         -Wstrict-overflow=5
             Also warn about cases where the compiler reduces the
             magnitude of a constant involved in a comparison.
             For example: "x + 2 > y" is simplified to "x + 1 >=
             y".  This is reported only at the highest warning
             level because this simplification applies to many
             comparisons, so this warning level gives a very
             large number of false positives.

     -Wsuggest-attribute=[pure|const|noreturn|format]
         Warn for cases where adding an attribute may be
         beneficial. The attributes currently supported are
         listed below.
         -Wsuggest-attribute=pure
         -Wsuggest-attribute=const
         -Wsuggest-attribute=noreturn
             Warn about functions that might be candidates for
             attributes "pure", "const" or "noreturn".  The
             compiler only warns for functions visible in other
             compilation units or (in the case of "pure" and
             "const") if it cannot prove that the function
             returns normally. A function returns normally if it
             doesn't contain an infinite loop or return
             abnormally by throwing, calling "abort()" or
             trapping.  This analysis requires option
             -fipa-pure-const, which is enabled by default at -O
             and higher.  Higher optimization levels improve the
             accuracy of the analysis.

         -Wsuggest-attribute=format
         -Wmissing-format-attribute
             Warn about function pointers that might be
             candidates for "format" attributes.  Note these are
             only possible candidates, not absolute ones.  GCC
             guesses that function pointers with "format"
             attributes that are used in assignment,
             initialization, parameter passing or return
             statements should have a corresponding "format"
             attribute in the resulting type.  I.e. the left-hand
             side of the assignment or initialization, the type
             of the parameter variable, or the return type of the
             containing function respectively should also have a
             "format" attribute to avoid the warning.

             GCC also warns about function definitions that might
             be candidates for "format" attributes.  Again, these
             are only possible candidates.  GCC guesses that
             "format" attributes might be appropriate for any
             function that calls a function like "vprintf" or
             "vscanf", but this might not always be the case, and
             some functions for which "format" attributes are
             appropriate may not be detected.

     -Warray-bounds
         This option is only active when -ftree-vrp is active
         (default for -O2 and above). It warns about subscripts
         to arrays that are always out of bounds. This warning is
         enabled by -Wall.

     -Wno-div-by-zero
         Do not warn about compile-time integer division by zero.
         Floating-point division by zero is not warned about, as
         it can be a legitimate way of obtaining infinities and
         NaNs.

     -Wsystem-headers
         Print warning messages for constructs found in system
         header files.  Warnings from system headers are normally
         suppressed, on the assumption that they usually do not
         indicate real problems and would only make the compiler
         output harder to read.  Using this command-line option
         tells GCC to emit warnings from system headers as if
         they occurred in user code.  However, note that using
         -Wall in conjunction with this option does not warn
         about unknown pragmas in system headers---for that,
         -Wunknown-pragmas must also be used.

     -Wtrampolines
          Warn about trampolines generated for pointers to nested functions.

          A trampoline is a small piece of data or code that is created at run
          time on the stack when the address of a nested function is taken, and
          is used to call the nested function indirectly.  For some targets, it
          is made up of data only and thus requires no special treatment.  But,
          for most targets, it is made up of code and thus requires the stack
          to be made executable in order for the program to work properly.

     -Wfloat-equal
         Warn if floating-point values are used in equality
         comparisons.

         The idea behind this is that sometimes it is convenient
         (for the programmer) to consider floating-point values
         as approximations to infinitely precise real numbers.
         If you are doing this, then you need to compute (by
         analyzing the code, or in some other way) the maximum or
         likely maximum error that the computation introduces,
         and allow for it when performing comparisons (and when
         producing output, but that's a different problem).  In
         particular, instead of testing for equality, you should
         check to see whether the two values have ranges that
         overlap; and this is done with the relational operators,
         so equality comparisons are probably mistaken.

     -Wtraditional (C and Objective-C only)
         Warn about certain constructs that behave differently in
         traditional and ISO C.  Also warn about ISO C constructs
         that have no traditional C equivalent, and/or
         problematic constructs that should be avoided.

         *   Macro parameters that appear within string literals
             in the macro body.  In traditional C macro
             replacement takes place within string literals, but
             in ISO C it does not.

         *   In traditional C, some preprocessor directives did
             not exist.  Traditional preprocessors only
             considered a line to be a directive if the #
             appeared in column 1 on the line.  Therefore
             -Wtraditional warns about directives that
             traditional C understands but ignores because the #
             does not appear as the first character on the line.
             It also suggests you hide directives like #pragma
             not understood by traditional C by indenting them.
             Some traditional implementations do not recognize
             #elif, so this option suggests avoiding it
             altogether.

         *   A function-like macro that appears without
             arguments.

         *   The unary plus operator.

         *   The U integer constant suffix, or the F or L
             floating-point constant suffixes.  (Traditional C
             does support the L suffix on integer constants.)
             Note, these suffixes appear in macros defined in the
             system headers of most modern systems, e.g. the
             _MIN/_MAX macros in "<limits.h>".  Use of these
             macros in user code might normally lead to spurious
             warnings, however GCC's integrated preprocessor has
             enough context to avoid warning in these cases.

         *   A function declared external in one block and then
             used after the end of the block.

         *   A "switch" statement has an operand of type "long".

         *   A non-"static" function declaration follows a
             "static" one.  This construct is not accepted by
             some traditional C compilers.

         *   The ISO type of an integer constant has a different
             width or signedness from its traditional type.  This
             warning is only issued if the base of the constant
             is ten.  I.e. hexadecimal or octal values, which
             typically represent bit patterns, are not warned
             about.

         *   Usage of ISO string concatenation is detected.

         *   Initialization of automatic aggregates.

         *   Identifier conflicts with labels.  Traditional C
             lacks a separate namespace for labels.

         *   Initialization of unions.  If the initializer is
             zero, the warning is omitted.  This is done under
             the assumption that the zero initializer in user
             code appears conditioned on e.g. "__STDC__" to avoid
             missing initializer warnings and relies on default
             initialization to zero in the traditional C case.

         *   Conversions by prototypes between
             fixed/floating-point values and vice versa.  The
             absence of these prototypes when compiling with
             traditional C causes serious problems.  This is a
             subset of the possible conversion warnings; for the
             full set use -Wtraditional-conversion.

         *   Use of ISO C style function definitions.  This
             warning intentionally is not issued for prototype
             declarations or variadic functions because these ISO
             C features appear in your code when using
             libiberty's traditional C compatibility macros,
             "PARAMS" and "VPARAMS".  This warning is also
             bypassed for nested functions because that feature
             is already a GCC extension and thus not relevant to
             traditional C compatibility.

     -Wtraditional-conversion (C and Objective-C only)
         Warn if a prototype causes a type conversion that is
         different from what would happen to the same argument in
         the absence of a prototype.  This includes conversions
         of fixed point to floating and vice versa, and
         conversions changing the width or signedness of a
         fixed-point argument except when the same as the default
         promotion.

     -Wdeclaration-after-statement (C and Objective-C only)
         Warn when a declaration is found after a statement in a
         block.  This construct, known from C++, was introduced
         with ISO C99 and is by default allowed in GCC.  It is
         not supported by ISO C90 and was not supported by GCC
         versions before GCC 3.0.

     -Wundef
         Warn if an undefined identifier is evaluated in an #if
         directive.

     -Wno-endif-labels
         Do not warn whenever an #else or an #endif are followed
         by text.

     -Wshadow
         Warn whenever a local variable or type declaration
         shadows another variable, parameter, type, or class
         member (in C++), or whenever a built-in function is
         shadowed. Note that in C++, the compiler warns if a
         local variable shadows an explicit typedef, but not if
         it shadows a struct/class/enum.

     -Wlarger-than=len
         Warn whenever an object of larger than len bytes is
         defined.

     -Wframe-larger-than=len
         Warn if the size of a function frame is larger than len
         bytes.  The computation done to determine the stack
         frame size is approximate and not conservative.  The
         actual requirements may be somewhat greater than len
         even if you do not get a warning.  In addition, any
         space allocated via "alloca", variable-length arrays, or
         related constructs is not included by the compiler when
         determining whether or not to issue a warning.

     -Wno-free-nonheap-object
         Do not warn when attempting to free an object that was
         not allocated on the heap.

     -Wstack-usage=len
         Warn if the stack usage of a function might be larger
         than len bytes.  The computation done to determine the
         stack usage is conservative.  Any space allocated via
         "alloca", variable-length arrays, or related constructs
         is included by the compiler when determining whether or
         not to issue a warning.

         The message is in keeping with the output of
         -fstack-usage.

         *   If the stack usage is fully static but exceeds the
             specified amount, it's:

                       warning: stack usage is 1120 bytes

         *   If the stack usage is (partly) dynamic but bounded,
             it's:

                       warning: stack usage might be 1648 bytes

         *   If the stack usage is (partly) dynamic and not
             bounded, it's:

                       warning: stack usage might be unbounded

     -Wunsafe-loop-optimizations
         Warn if the loop cannot be optimized because the
         compiler cannot assume anything on the bounds of the
         loop indices.  With -funsafe-loop-optimizations warn if
         the compiler makes such assumptions.

     -Wno-pedantic-ms-format (MinGW targets only)
         When used in combination with -Wformat and -pedantic
         without GNU extensions, this option disables the
         warnings about non-ISO "printf" / "scanf" format width
         specifiers "I32", "I64", and "I" used on Windows
         targets, which depend on the MS runtime.

     -Wpointer-arith
         Warn about anything that depends on the "size of" a
         function type or of "void".  GNU C assigns these types a
         size of 1, for convenience in calculations with "void *"
         pointers and pointers to functions.  In C++, warn also
         when an arithmetic operation involves "NULL".  This
         warning is also enabled by -Wpedantic.

     -Wtype-limits
         Warn if a comparison is always true or always false due
         to the limited range of the data type, but do not warn
         for constant expressions.  For example, warn if an
         unsigned variable is compared against zero with < or >=.
         This warning is also enabled by -Wextra.

     -Wbad-function-cast (C and Objective-C only)
         Warn whenever a function call is cast to a non-matching
         type.  For example, warn if "int malloc()" is cast to
         "anything *".

     -Wc++-compat (C and Objective-C only)
         Warn about ISO C constructs that are outside of the
         common subset of ISO C and ISO C++, e.g. request for
         implicit conversion from "void *" to a pointer to
         non-"void" type.

     -Wc++11-compat (C++ and Objective-C++ only)
         Warn about C++ constructs whose meaning differs between
         ISO C++ 1998 and ISO C++ 2011, e.g., identifiers in ISO
         C++ 1998 that are keywords in ISO C++ 2011.  This
         warning turns on -Wnarrowing and is enabled by -Wall.

     -Wcast-qual
         Warn whenever a pointer is cast so as to remove a type
         qualifier from the target type.  For example, warn if a
         "const char *" is cast to an ordinary "char *".

         Also warn when making a cast that introduces a type
         qualifier in an unsafe way.  For example, casting "char
         **" to "const char **" is unsafe, as in this example:

                   /* p is char ** value.  */
                   const char **q = (const char **) p;
                   /* Assignment of readonly string to const char * is OK.  */
                   *q = "string";
                   /* Now char** pointer points to read-only memory.  */
                   **p = `b';

     -Wcast-align
         Warn whenever a pointer is cast such that the required
         alignment of the target is increased.  For example, warn
         if a "char *" is cast to an "int *" on machines where
         integers can only be accessed at two- or four-byte
         boundaries.

     -Wwrite-strings
         When compiling C, give string constants the type "const
         char[length]" so that copying the address of one into a
         non-"const" "char *" pointer produces a warning.  These
         warnings help you find at compile time code that can try
         to write into a string constant, but only if you have
         been very careful about using "const" in declarations
         and prototypes.  Otherwise, it is just a nuisance. This
         is why we did not make -Wall request these warnings.

         When compiling C++, warn about the deprecated conversion
         from string literals to "char *".  This warning is
         enabled by default for C++ programs.

     -Wclobbered
         Warn for variables that might be changed by longjmp or
         vfork.  This warning is also enabled by -Wextra.

     -Wconversion
         Warn for implicit conversions that may alter a value.
         This includes conversions between real and integer, like
         "abs (x)" when "x" is "double"; conversions between
         signed and unsigned, like "unsigned ui = -1"; and
         conversions to smaller types, like "sqrtf (M_PI)". Do
         not warn for explicit casts like "abs ((int) x)" and "ui
         = (unsigned) -1", or if the value is not changed by the
         conversion like in "abs (2.0)".  Warnings about
         conversions between signed and unsigned integers can be
         disabled by using -Wno-sign-conversion.

         For C++, also warn for confusing overload resolution for
         user-defined conversions; and conversions that never use
         a type conversion operator: conversions to "void", the
         same type, a base class or a reference to them. Warnings
         about conversions between signed and unsigned integers
         are disabled by default in C++ unless -Wsign-conversion
         is explicitly enabled.

     -Wno-conversion-null (C++ and Objective-C++ only)
         Do not warn for conversions between "NULL" and non-
         pointer types. -Wconversion-null is enabled by default.

     -Wzero-as-null-pointer-constant (C++ and Objective-C++ only)
         Warn when a literal `0' is used as null pointer
         constant.  This can be useful to facilitate the
         conversion to "nullptr" in C++11.

     -Wuseless-cast (C++ and Objective-C++ only)
         Warn when an expression is casted to its own type.

     -Wempty-body
         Warn if an empty body occurs in an if, else or do while
         statement.  This warning is also enabled by -Wextra.

     -Wenum-compare
         Warn about a comparison between values of different
         enumerated types.  In C++ enumeral mismatches in
         conditional expressions are also diagnosed and the
         warning is enabled by default.  In C this warning is
         enabled by -Wall.

     -Wjump-misses-init (C, Objective-C only)
         Warn if a "goto" statement or a "switch" statement jumps
         forward across the initialization of a variable, or
         jumps backward to a label after the variable has been
         initialized.  This only warns about variables that are
         initialized when they are declared.  This warning is
         only supported for C and Objective-C; in C++ this sort
         of branch is an error in any case.

         -Wjump-misses-init is included in -Wc++-compat.  It can
         be disabled with the -Wno-jump-misses-init option.

     -Wsign-compare
         Warn when a comparison between signed and unsigned
         values could produce an incorrect result when the signed
         value is converted to unsigned.  This warning is also
         enabled by -Wextra; to get the other warnings of -Wextra
         without this warning, use -Wextra -Wno-sign-compare.

     -Wsign-conversion
         Warn for implicit conversions that may change the sign
         of an integer value, like assigning a signed integer
         expression to an unsigned integer variable. An explicit
         cast silences the warning. In C, this option is enabled
         also by -Wconversion.

     -Wsizeof-pointer-memaccess
         Warn for suspicious length parameters to certain string
         and memory built-in functions if the argument uses
         "sizeof".  This warning warns e.g.  about "memset (ptr,
         0, sizeof (ptr));" if "ptr" is not an array, but a
         pointer, and suggests a possible fix, or about "memcpy
         (&foo, ptr, sizeof (&foo));".  This warning is enabled
         by -Wall.

     -Waddress

         Warn about suspicious uses of memory addresses. These
         include using the address of a function in a conditional
         expression, such as "void func(void); if (func)", and
         comparisons against the memory address of a string
         literal, such as "if (x == "abc")".  Such uses typically
         indicate a programmer error: the address of a function
         always evaluates to true, so their use in a conditional
         usually indicate that the programmer forgot the
         parentheses in a function call; and comparisons against
         string literals result in unspecified behavior and are
         not portable in C, so they usually indicate that the
         programmer intended to use "strcmp".  This warning is
         enabled by -Wall.

     -Wlogical-op
         Warn about suspicious uses of logical operators in
         expressions.  This includes using logical operators in
         contexts where a bit-wise operator is likely to be
         expected.

     -Waggregate-return
         Warn if any functions that return structures or unions
         are defined or called.  (In languages where you can
         return an array, this also elicits a warning.)

     -Wno-aggressive-loop-optimizations
         Warn if in a loop with constant number of iterations the
         compiler detects undefined behavior in some statement
         during one or more of the iterations.

     -Wno-attributes
         Do not warn if an unexpected "__attribute__" is used,
         such as unrecognized attributes, function attributes
         applied to variables, etc.  This does not stop errors
         for incorrect use of supported attributes.

     -Wno-builtin-macro-redefined
         Do not warn if certain built-in macros are redefined.
         This suppresses warnings for redefinition of
         "__TIMESTAMP__", "__TIME__", "__DATE__", "__FILE__", and
         "__BASE_FILE__".

     -Wstrict-prototypes (C and Objective-C only)
         Warn if a function is declared or defined without
         specifying the argument types.  (An old-style function
         definition is permitted without a warning if preceded by
         a declaration that specifies the argument types.)

     -Wold-style-declaration (C and Objective-C only)
         Warn for obsolescent usages, according to the C
         Standard, in a declaration. For example, warn if
         storage-class specifiers like "static" are not the first
         things in a declaration.  This warning is also enabled
         by -Wextra.

     -Wold-style-definition (C and Objective-C only)
         Warn if an old-style function definition is used.  A
         warning is given even if there is a previous prototype.

     -Wmissing-parameter-type (C and Objective-C only)
         A function parameter is declared without a type
         specifier in K&R-style functions:

                 void foo(bar) { }

         This warning is also enabled by -Wextra.

     -Wmissing-prototypes (C and Objective-C only)
         Warn if a global function is defined without a previous
         prototype declaration.  This warning is issued even if
         the definition itself provides a prototype.  Use this
         option to detect global functions that do not have a
         matching prototype declaration in a header file.  This
         option is not valid for C++ because all function
         declarations provide prototypes and a non-matching
         declaration will declare an overload rather than
         conflict with an earlier declaration.  Use
         -Wmissing-declarations to detect missing declarations in
         C++.

     -Wmissing-declarations
         Warn if a global function is defined without a previous
         declaration.  Do so even if the definition itself
         provides a prototype.  Use this option to detect global
         functions that are not declared in header files.  In C,
         no warnings are issued for functions with previous non-
         prototype declarations; use -Wmissing-prototype to
         detect missing prototypes.  In C++, no warnings are
         issued for function templates, or for inline functions,
         or for functions in anonymous namespaces.

     -Wmissing-field-initializers
         Warn if a structure's initializer has some fields
         missing.  For example, the following code causes such a
         warning, because "x.h" is implicitly zero:

                 struct s { int f, g, h; };
                 struct s x = { 3, 4 };

         This option does not warn about designated initializers,
         so the following modification does not trigger a
         warning:

                 struct s { int f, g, h; };
                 struct s x = { .f = 3, .g = 4 };

         This warning is included in -Wextra.  To get other
         -Wextra warnings without this one, use -Wextra
         -Wno-missing-field-initializers.

     -Wno-multichar
         Do not warn if a multicharacter constant ('FOOF') is
         used.  Usually they indicate a typo in the user's code,
         as they have implementation-defined values, and should
         not be used in portable code.

     -Wnormalized=<none|id|nfc|nfkc>
         In ISO C and ISO C++, two identifiers are different if
         they are different sequences of characters.  However,
         sometimes when characters outside the basic ASCII
         character set are used, you can have two different
         character sequences that look the same.  To avoid
         confusion, the ISO 10646 standard sets out some
         normalization rules which when applied ensure that two
         sequences that look the same are turned into the same
         sequence.  GCC can warn you if you are using identifiers
         that have not been normalized; this option controls that
         warning.

         There are four levels of warning supported by GCC.  The
         default is -Wnormalized=nfc, which warns about any
         identifier that is not in the ISO 10646 "C" normalized
         form, NFC.  NFC is the recommended form for most uses.

         Unfortunately, there are some characters allowed in
         identifiers by ISO C and ISO C++ that, when turned into
         NFC, are not allowed in identifiers.  That is, there's
         no way to use these symbols in portable ISO C or C++ and
         have all your identifiers in NFC.  -Wnormalized=id
         suppresses the warning for these characters.  It is
         hoped that future versions of the standards involved
         will correct this, which is why this option is not the
         default.

         You can switch the warning off for all characters by
         writing -Wnormalized=none.  You should only do this if
         you are using some other normalization scheme (like
         "D"), because otherwise you can easily create bugs that
         are literally impossible to see.

         Some characters in ISO 10646 have distinct meanings but
         look identical in some fonts or display methodologies,
         especially once formatting has been applied.  For
         instance "\u207F", "SUPERSCRIPT LATIN SMALL LETTER N",
         displays just like a regular "n" that has been placed in
         a superscript.  ISO 10646 defines the NFKC normalization
         scheme to convert all these into a standard form as
         well, and GCC warns if your code is not in NFKC if you
         use -Wnormalized=nfkc.  This warning is comparable to
         warning about every identifier that contains the letter
         O because it might be confused with the digit 0, and so
         is not the default, but may be useful as a local coding
         convention if the programming environment cannot be
         fixed to display these characters distinctly.

     -Wno-deprecated
         Do not warn about usage of deprecated features.

     -Wno-deprecated-declarations
         Do not warn about uses of functions, variables, and
         types marked as deprecated by using the "deprecated"
         attribute.

     -Wno-overflow
         Do not warn about compile-time overflow in constant
         expressions.

     -Woverride-init (C and Objective-C only)
         Warn if an initialized field without side effects is
         overridden when using designated initializers.

         This warning is included in -Wextra.  To get other
         -Wextra warnings without this one, use -Wextra
         -Wno-override-init.

     -Wpacked
         Warn if a structure is given the packed attribute, but
         the packed attribute has no effect on the layout or size
         of the structure.  Such structures may be mis-aligned
         for little benefit.  For instance, in this code, the
         variable "f.x" in "struct bar" is misaligned even though
         "struct bar" does not itself have the packed attribute:

                 struct foo {
                   int x;
                   char a, b, c, d;
                 } __attribute__((packed));
                 struct bar {
                   char z;
                   struct foo f;
                 };

     -Wpacked-bitfield-compat
         The 4.1, 4.2 and 4.3 series of GCC ignore the "packed"
         attribute on bit-fields of type "char".  This has been
         fixed in GCC 4.4 but the change can lead to differences
         in the structure layout.  GCC informs you when the
         offset of such a field has changed in GCC 4.4.  For
         example there is no longer a 4-bit padding between field
         "a" and "b" in this structure:

                 struct foo
                 {
                   char a:4;
                   char b:8;
                 } __attribute__ ((packed));

         This warning is enabled by default.  Use
         -Wno-packed-bitfield-compat to disable this warning.

     -Wpadded
         Warn if padding is included in a structure, either to
         align an element of the structure or to align the whole
         structure.  Sometimes when this happens it is possible
         to rearrange the fields of the structure to reduce the
         padding and so make the structure smaller.

     -Wredundant-decls
         Warn if anything is declared more than once in the same
         scope, even in cases where multiple declaration is valid
         and changes nothing.

     -Wnested-externs (C and Objective-C only)
         Warn if an "extern" declaration is encountered within a
         function.

     -Wno-inherited-variadic-ctor
         Suppress warnings about use of C++11 inheriting
         constructors when the base class inherited from has a C
         variadic constructor; the warning is on by default
         because the ellipsis is not inherited.

     -Winline
         Warn if a function that is declared as inline cannot be
         inlined.  Even with this option, the compiler does not
         warn about failures to inline functions declared in
         system headers.

         The compiler uses a variety of heuristics to determine
         whether or not to inline a function.  For example, the
         compiler takes into account the size of the function
         being inlined and the amount of inlining that has
         already been done in the current function.  Therefore,
         seemingly insignificant changes in the source program
         can cause the warnings produced by -Winline to appear or
         disappear.

     -Wno-invalid-offsetof (C++ and Objective-C++ only)
         Suppress warnings from applying the offsetof macro to a
         non-POD type.  According to the 1998 ISO C++ standard,
         applying offsetof to a non-POD type is undefined.  In
         existing C++ implementations, however, offsetof
         typically gives meaningful results even when applied to
         certain kinds of non-POD types (such as a simple struct
         that fails to be a POD type only by virtue of having a
         constructor).  This flag is for users who are aware that
         they are writing nonportable code and who have
         deliberately chosen to ignore the warning about it.

         The restrictions on offsetof may be relaxed in a future
         version of the C++ standard.

     -Wno-int-to-pointer-cast
         Suppress warnings from casts to pointer type of an
         integer of a different size. In C++, casting to a
         pointer type of smaller size is an error. Wint-to-
         pointer-cast is enabled by default.

     -Wno-pointer-to-int-cast (C and Objective-C only)
         Suppress warnings from casts from a pointer to an
         integer type of a different size.

     -Winvalid-pch
         Warn if a precompiled header is found in the search path
         but can't be used.

     -Wlong-long
         Warn if long long type is used.  This is enabled by
         either -Wpedantic or -Wtraditional in ISO C90 and C++98
         modes.  To inhibit the warning messages, use
         -Wno-long-long.

     -Wvariadic-macros
         Warn if variadic macros are used in pedantic ISO C90
         mode, or the GNU alternate syntax when in pedantic ISO
         C99 mode.  This is default.  To inhibit the warning
         messages, use -Wno-variadic-macros.

     -Wvarargs
         Warn upon questionable usage of the macros used to
         handle variable arguments like va_start.  This is
         default.  To inhibit the warning messages, use
         -Wno-varargs.

     -Wvector-operation-performance
         Warn if vector operation is not implemented via SIMD
         capabilities of the architecture.  Mainly useful for the
         performance tuning.  Vector operation can be implemented
         "piecewise", which means that the scalar operation is
         performed on every vector element; "in parallel", which
         means that the vector operation is implemented using
         scalars of wider type, which normally is more
         performance efficient; and "as a single scalar", which
         means that vector fits into a scalar type.

     -Wno-virtual-move-assign
         Suppress warnings about inheriting from a virtual base
         with a non-trivial C++11 move assignment operator.  This
         is dangerous because if the virtual base is reachable
         along more than one path, it will be moved multiple
         times, which can mean both objects end up in the moved-
         from state.  If the move assignment operator is written
         to avoid moving from a moved-from object, this warning
         can be disabled.

     -Wvla
         Warn if variable length array is used in the code.
         -Wno-vla prevents the -Wpedantic warning of the variable
         length array.

     -Wvolatile-register-var
         Warn if a register variable is declared volatile.  The
         volatile modifier does not inhibit all optimizations
         that may eliminate reads and/or writes to register
         variables.  This warning is enabled by -Wall.

     -Wdisabled-optimization
         Warn if a requested optimization pass is disabled.  This
         warning does not generally indicate that there is
         anything wrong with your code; it merely indicates that
         GCC's optimizers are unable to handle the code
         effectively.  Often, the problem is that your code is
         too big or too complex; GCC refuses to optimize programs
         when the optimization itself is likely to take
         inordinate amounts of time.

     -Wpointer-sign (C and Objective-C only)
         Warn for pointer argument passing or assignment with
         different signedness.  This option is only supported for
         C and Objective-C.  It is implied by -Wall and by
         -Wpedantic, which can be disabled with
         -Wno-pointer-sign.

     -Wstack-protector
         This option is only active when -fstack-protector is
         active.  It warns about functions that are not protected
         against stack smashing.

     -Wno-mudflap
         Suppress warnings about constructs that cannot be
         instrumented by -fmudflap.

     -Woverlength-strings

         Warn about string constants that are longer than the
         "minimum maximum" length specified in the C standard.
         Modern compilers generally allow string constants that
         are much longer than the standard's minimum limit, but
         very portable programs should avoid using longer
         strings.

         The limit applies after string constant concatenation,
         and does not count the trailing NUL.  In C90, the limit
         was 509 characters; in C99, it was raised to 4095.
         C++98 does not specify a normative minimum maximum, so
         we do not diagnose overlength strings in C++.

         This option is implied by -Wpedantic, and can be
         disabled with -Wno-overlength-strings.

     -Wunsuffixed-float-constants (C and Objective-C only)
         Issue a warning for any floating constant that does not
         have a suffix.  When used together with -Wsystem-headers
         it warns about such constants in system header files.
         This can be useful when preparing code to use with the
         "FLOAT_CONST_DECIMAL64" pragma from the decimal
         floating-point extension to C99.

  Options for Debugging Your Program or GCC
     GCC has various special options that are used for debugging
     either your program or GCC:

     -g  Produce debugging information in the operating system's
         native format (stabs, COFF, XCOFF, or DWARF 2).  GDB can
         work with this debugging information.

         On most systems that use stabs format, -g enables use of
         extra debugging information that only GDB can use; this
         extra information makes debugging work better in GDB but
         probably makes other debuggers crash or refuse to read
         the program.  If you want to control for certain whether
         to generate the extra information, use -gstabs+,
         -gstabs, -gxcoff+, -gxcoff, or -gvms (see below).

         GCC allows you to use -g with -O.  The shortcuts taken
         by optimized code may occasionally produce surprising
         results: some variables you declared may not exist at
         all; flow of control may briefly move where you did not
         expect it; some statements may not be executed because
         they compute constant results or their values are
         already at hand; some statements may execute in
         different places because they have been moved out of
         loops.

         Nevertheless it proves possible to debug optimized
         output.  This makes it reasonable to use the optimizer
         for programs that might have bugs.

         The following options are useful when GCC is generated
         with the capability for more than one debugging format.

     -gsplit-dwarf
         Separate as much dwarf debugging information as possible
         into a separate output file with the extension .dwo.
         This option allows the build system to avoid linking
         files with debug information.  To be useful, this option
         requires a debugger capable of reading .dwo files.

     -ggdb
         Produce debugging information for use by GDB.  This
         means to use the most expressive format available (DWARF
         2, stabs, or the native format if neither of those are
         supported), including GDB extensions if at all possible.

     -gpubnames
         Generate dwarf .debug_pubnames and .debug_pubtypes
         sections.

     -gstabs
         Produce debugging information in stabs format (if that
         is supported), without GDB extensions.  This is the
         format used by DBX on most BSD systems.  On MIPS, Alpha
         and System V Release 4 systems this option produces
         stabs debugging output that is not understood by DBX or
         SDB.  On System V Release 4 systems this option requires
         the GNU assembler.

     -feliminate-unused-debug-symbols
         Produce debugging information in stabs format (if that
         is supported), for only symbols that are actually used.

     -femit-class-debug-always
         Instead of emitting debugging information for a C++
         class in only one object file, emit it in all object
         files using the class.  This option should be used only
         with debuggers that are unable to handle the way GCC
         normally emits debugging information for classes because
         using this option increases the size of debugging
         information by as much as a factor of two.

     -fdebug-types-section
         When using DWARF Version 4 or higher, type DIEs can be
         put into their own ".debug_types" section instead of
         making them part of the ".debug_info" section.  It is
         more efficient to put them in a separate comdat sections
         since the linker can then remove duplicates.  But not
         all DWARF consumers support ".debug_types" sections yet
         and on some objects ".debug_types" produces larger
         instead of smaller debugging information.

     -gstabs+
         Produce debugging information in stabs format (if that
         is supported), using GNU extensions understood only by
         the GNU debugger (GDB).  The use of these extensions is
         likely to make other debuggers crash or refuse to read
         the program.

     -gcoff
         Produce debugging information in COFF format (if that is
         supported).  This is the format used by SDB on most
         System V systems prior to System V Release 4.

     -gxcoff
         Produce debugging information in XCOFF format (if that
         is supported).  This is the format used by the DBX
         debugger on IBM RS/6000 systems.

     -gxcoff+
         Produce debugging information in XCOFF format (if that
         is supported), using GNU extensions understood only by
         the GNU debugger (GDB).  The use of these extensions is
         likely to make other debuggers crash or refuse to read
         the program, and may cause assemblers other than the GNU
         assembler (GAS) to fail with an error.

     -gdwarf-version
         Produce debugging information in DWARF format (if that
         is supported).  The value of version may be either 2, 3
         or 4; the default version for most targets is 4.

         Note that with DWARF Version 2, some ports require and
         always use some non-conflicting DWARF 3 extensions in
         the unwind tables.

         Version 4 may require GDB 7.0 and
         -fvar-tracking-assignments for maximum benefit.

     -grecord-gcc-switches
         This switch causes the command-line options used to
         invoke the compiler that may affect code generation to
         be appended to the DW_AT_producer attribute in DWARF
         debugging information.  The options are concatenated
         with spaces separating them from each other and from the
         compiler version.  See also -frecord-gcc-switches for
         another way of storing compiler options into the object
         file.  This is the default.

     -gno-record-gcc-switches
         Disallow appending command-line options to the
         DW_AT_producer attribute in DWARF debugging information.

     -gstrict-dwarf
         Disallow using extensions of later DWARF standard
         version than selected with -gdwarf-version.  On most
         targets using non-conflicting DWARF extensions from
         later standard versions is allowed.

     -gno-strict-dwarf
         Allow using extensions of later DWARF standard version
         than selected with -gdwarf-version.

     -gvms
         Produce debugging information in Alpha/VMS debug format
         (if that is supported).  This is the format used by
         DEBUG on Alpha/VMS systems.

     -glevel
     -ggdblevel
     -gstabslevel
     -gcofflevel
     -gxcofflevel
     -gvmslevel
         Request debugging information and also use level to
         specify how much information.  The default level is 2.

         Level 0 produces no debug information at all.  Thus, -g0
         negates -g.

         Level 1 produces minimal information, enough for making
         backtraces in parts of the program that you don't plan
         to debug.  This includes descriptions of functions and
         external variables, but no information about local
         variables and no line numbers.

         Level 3 includes extra information, such as all the
         macro definitions present in the program.  Some
         debuggers support macro expansion when you use -g3.

         -gdwarf-2 does not accept a concatenated debug level,
         because GCC used to support an option -gdwarf that meant
         to generate debug information in version 1 of the DWARF
         format (which is very different from version 2), and it
         would have been too confusing.  That debug format is
         long obsolete, but the option cannot be changed now.
         Instead use an additional -glevel option to change the
         debug level for DWARF.

     -gtoggle
         Turn off generation of debug info, if leaving out this
         option generates it, or turn it on at level 2 otherwise.
         The position of this argument in the command line does
         not matter; it takes effect after all other options are
         processed, and it does so only once, no matter how many
         times it is given.  This is mainly intended to be used
         with -fcompare-debug.

     -fsanitize=address
         Enable AddressSanitizer, a fast memory error detector.
         Memory access instructions will be instrumented to
         detect out-of-bounds and use-after-free bugs.  See
         <http://code.google.com/p/address-sanitizer/> for more
         details.

     -fsanitize=thread
         Enable ThreadSanitizer, a fast data race detector.
         Memory access instructions will be instrumented to
         detect data race bugs.  See
         <http://code.google.com/p/data-race-test/wiki/ThreadSanitizer>
         for more details.

     -fdump-final-insns[=file]
         Dump the final internal representation (RTL) to file.
         If the optional argument is omitted (or if file is "."),
         the name of the dump file is determined by appending
         ".gkd" to the compilation output file name.

     -fcompare-debug[=opts]
         If no error occurs during compilation, run the compiler
         a second time, adding opts and -fcompare-debug-second to
         the arguments passed to the second compilation.  Dump
         the final internal representation in both compilations,
         and print an error if they differ.

         If the equal sign is omitted, the default -gtoggle is
         used.

         The environment variable GCC_COMPARE_DEBUG, if defined,
         non-empty and nonzero, implicitly enables
         -fcompare-debug.  If GCC_COMPARE_DEBUG is defined to a
         string starting with a dash, then it is used for opts,
         otherwise the default -gtoggle is used.

         -fcompare-debug=, with the equal sign but without opts,
         is equivalent to -fno-compare-debug, which disables the
         dumping of the final representation and the second
         compilation, preventing even GCC_COMPARE_DEBUG from
         taking effect.

         To verify full coverage during -fcompare-debug testing,
         set GCC_COMPARE_DEBUG to say
         -fcompare-debug-not-overridden, which GCC rejects as an
         invalid option in any actual compilation (rather than
         preprocessing, assembly or linking).  To get just a
         warning, setting GCC_COMPARE_DEBUG to
         -w%n-fcompare-debug not overridden will do.

     -fcompare-debug-second
         This option is implicitly passed to the compiler for the
         second compilation requested by -fcompare-debug, along
         with options to silence warnings, and omitting other
         options that would cause side-effect compiler outputs to
         files or to the standard output.  Dump files and
         preserved temporary files are renamed so as to contain
         the ".gk" additional extension during the second
         compilation, to avoid overwriting those generated by the
         first.

         When this option is passed to the compiler driver, it
         causes the first compilation to be skipped, which makes
         it useful for little other than debugging the compiler
         proper.

     -feliminate-dwarf2-dups
         Compress DWARF 2 debugging information by eliminating
         duplicated information about each symbol.  This option
         only makes sense when generating DWARF 2 debugging
         information with -gdwarf-2.

     -femit-struct-debug-baseonly
         Emit debug information for struct-like types only when
         the base name of the compilation source file matches the
         base name of file in which the struct is defined.

         This option substantially reduces the size of debugging
         information, but at significant potential loss in type
         information to the debugger.  See
         -femit-struct-debug-reduced for a less aggressive
         option.  See -femit-struct-debug-detailed for more
         detailed control.

         This option works only with DWARF 2.

     -femit-struct-debug-reduced
         Emit debug information for struct-like types only when
         the base name of the compilation source file matches the
         base name of file in which the type is defined, unless
         the struct is a template or defined in a system header.

         This option significantly reduces the size of debugging
         information, with some potential loss in type
         information to the debugger.  See
         -femit-struct-debug-baseonly for a more aggressive
         option.  See -femit-struct-debug-detailed for more
         detailed control.

         This option works only with DWARF 2.

     -femit-struct-debug-detailed[=spec-list]

         Specify the struct-like types for which the compiler
         generates debug information.  The intent is to reduce
         duplicate struct debug information between different
         object files within the same program.

         This option is a detailed version of
         -femit-struct-debug-reduced and
         -femit-struct-debug-baseonly, which serves for most
         needs.

         A specification has the
         syntax[dir:|ind:][ord:|gen:](any|sys|base|none)

         The optional first word limits the specification to
         structs that are used directly (dir:) or used indirectly
         (ind:).  A struct type is used directly when it is the
         type of a variable, member.  Indirect uses arise through
         pointers to structs.  That is, when use of an incomplete
         struct is valid, the use is indirect.  An example is
         struct one direct; struct two * indirect;.

         The optional second word limits the specification to
         ordinary structs (ord:) or generic structs (gen:).
         Generic structs are a bit complicated to explain.  For
         C++, these are non-explicit specializations of template
         classes, or non-template classes within the above.
         Other programming languages have generics, but
         -femit-struct-debug-detailed does not yet implement
         them.

         The third word specifies the source files for those
         structs for which the compiler should emit debug
         information.  The values none and any have the normal
         meaning.  The value base means that the base of name of
         the file in which the type declaration appears must
         match the base of the name of the main compilation file.
         In practice, this means that when compiling foo.c, debug
         information is generated for types declared in that file
         and foo.h, but not other header files.  The value sys
         means those types satisfying base or declared in system
         or compiler headers.

         You may need to experiment to determine the best
         settings for your application.

         The default is -femit-struct-debug-detailed=all.

         This option works only with DWARF 2.

     -fno-merge-debug-strings
         Direct the linker to not merge together strings in the
         debugging information that are identical in different
         object files.  Merging is not supported by all
         assemblers or linkers.  Merging decreases the size of
         the debug information in the output file at the cost of
         increasing link processing time.  Merging is enabled by
         default.

     -fdebug-prefix-map=old=new
         When compiling files in directory old, record debugging
         information describing them as in new instead.

     -fno-dwarf2-cfi-asm
         Emit DWARF 2 unwind info as compiler generated
         ".eh_frame" section instead of using GAS ".cfi_*"
         directives.

     -p  Generate extra code to write profile information
         suitable for the analysis program prof.  You must use
         this option when compiling the source files you want
         data about, and you must also use it when linking.

     -pg Generate extra code to write profile information
         suitable for the analysis program gprof.  You must use
         this option when compiling the source files you want
         data about, and you must also use it when linking.

     -Q  Makes the compiler print out each function name as it is
         compiled, and print some statistics about each pass when
         it finishes.

     -ftime-report
         Makes the compiler print some statistics about the time
         consumed by each pass when it finishes.

     -fmem-report
         Makes the compiler print some statistics about permanent
         memory allocation when it finishes.

     -fmem-report-wpa
         Makes the compiler print some statistics about permanent
         memory allocation for the WPA phase only.

     -fpre-ipa-mem-report
     -fpost-ipa-mem-report
         Makes the compiler print some statistics about permanent
         memory allocation before or after interprocedural
         optimization.

     -fprofile-report
         Makes the compiler print some statistics about
         consistency of the (estimated) profile and effect of
         individual passes.

     -fstack-usage
         Makes the compiler output stack usage information for
         the program, on a per-function basis.  The filename for
         the dump is made by appending .su to the auxname.
         auxname is generated from the name of the output file,
         if explicitly specified and it is not an executable,
         otherwise it is the basename of the source file.  An
         entry is made up of three fields:

         *   The name of the function.

         *   A number of bytes.

         *   One or more qualifiers: "static", "dynamic",
             "bounded".

         The qualifier "static" means that the function
         manipulates the stack statically: a fixed number of
         bytes are allocated for the frame on function entry and
         released on function exit; no stack adjustments are
         otherwise made in the function.  The second field is
         this fixed number of bytes.

         The qualifier "dynamic" means that the function
         manipulates the stack dynamically: in addition to the
         static allocation described above, stack adjustments are
         made in the body of the function, for example to
         push/pop arguments around function calls.  If the
         qualifier "bounded" is also present, the amount of these
         adjustments is bounded at compile time and the second
         field is an upper bound of the total amount of stack
         used by the function.  If it is not present, the amount
         of these adjustments is not bounded at compile time and
         the second field only represents the bounded part.

     -fprofile-arcs
         Add code so that program flow arcs are instrumented.
         During execution the program records how many times each
         branch and call is executed and how many times it is
         taken or returns.  When the compiled program exits it
         saves this data to a file called auxname.gcda for each
         source file.  The data may be used for profile-directed
         optimizations (-fbranch-probabilities), or for test
         coverage analysis (-ftest-coverage).  Each object file's
         auxname is generated from the name of the output file,
         if explicitly specified and it is not the final
         executable, otherwise it is the basename of the source
         file.  In both cases any suffix is removed (e.g.
         foo.gcda for input file dir/foo.c, or dir/foo.gcda for
         output file specified as -o dir/foo.o).

     --coverage

         This option is used to compile and link code
         instrumented for coverage analysis.  The option is a
         synonym for -fprofile-arcs -ftest-coverage (when
         compiling) and -lgcov (when linking).  See the
         documentation for those options for more details.

         *   Compile the source files with -fprofile-arcs plus
             optimization and code generation options.  For test
             coverage analysis, use the additional
             -ftest-coverage option.  You do not need to profile
             every source file in a program.

         *   Link your object files with -lgcov or -fprofile-arcs
             (the latter implies the former).

         *   Run the program on a representative workload to
             generate the arc profile information.  This may be
             repeated any number of times.  You can run
             concurrent instances of your program, and provided
             that the file system supports locking, the data
             files will be correctly updated.  Also "fork" calls
             are detected and correctly handled (double counting
             will not happen).

         *   For profile-directed optimizations, compile the
             source files again with the same optimization and
             code generation options plus -fbranch-probabilities.

         *   For test coverage analysis, use gcov to produce
             human readable information from the .gcno and .gcda
             files.  Refer to the gcov documentation for further
             information.

         With -fprofile-arcs, for each function of your program
         GCC creates a program flow graph, then finds a spanning
         tree for the graph.  Only arcs that are not on the
         spanning tree have to be instrumented: the compiler adds
         code to count the number of times that these arcs are
         executed.  When an arc is the only exit or only entrance
         to a block, the instrumentation code can be added to the
         block; otherwise, a new basic block must be created to
         hold the instrumentation code.

     -ftest-coverage
         Produce a notes file that the gcov code-coverage utility
         can use to show program coverage.  Each source file's
         note file is called auxname.gcno.  Refer to the
         -fprofile-arcs option above for a description of auxname
         and instructions on how to generate test coverage data.
         Coverage data matches the source files more closely if
         you do not optimize.

     -fdbg-cnt-list
         Print the name and the counter upper bound for all debug
         counters.

     -fdbg-cnt=counter-value-list
         Set the internal debug counter upper bound.  counter-
         value-list is a comma-separated list of name:value pairs
         which sets the upper bound of each debug counter name to
         value.  All debug counters have the initial upper bound
         of "UINT_MAX"; thus "dbg_cnt()" returns true always
         unless the upper bound is set by this option.  For
         example, with -fdbg-cnt=dce:10,tail_call:0,
         "dbg_cnt(dce)" returns true only for first 10
         invocations.

     -fenable-kind-pass
     -fdisable-kind-pass=range-list
         This is a set of options that are used to explicitly
         disable/enable optimization passes.  These options are
         intended for use for debugging GCC.  Compiler users
         should use regular options for enabling/disabling passes
         instead.

         -fdisable-ipa-pass
             Disable IPA pass pass. pass is the pass name.  If
             the same pass is statically invoked in the compiler
             multiple times, the pass name should be appended
             with a sequential number starting from 1.

         -fdisable-rtl-pass
         -fdisable-rtl-pass=range-list
             Disable RTL pass pass.  pass is the pass name.  If
             the same pass is statically invoked in the compiler
             multiple times, the pass name should be appended
             with a sequential number starting from 1.  range-
             list is a comma-separated list of function ranges or
             assembler names.  Each range is a number pair
             separated by a colon.  The range is inclusive in
             both ends.  If the range is trivial, the number pair
             can be simplified as a single number.  If the
             function's call graph node's uid falls within one of
             the specified ranges, the pass is disabled for that
             function.  The uid is shown in the function header
             of a dump file, and the pass names can be dumped by
             using option -fdump-passes.

         -fdisable-tree-pass
         -fdisable-tree-pass=range-list
             Disable tree pass pass.  See -fdisable-rtl for the
             description of option arguments.

         -fenable-ipa-pass

             Enable IPA pass pass.  pass is the pass name.  If
             the same pass is statically invoked in the compiler
             multiple times, the pass name should be appended
             with a sequential number starting from 1.

         -fenable-rtl-pass
         -fenable-rtl-pass=range-list
             Enable RTL pass pass.  See -fdisable-rtl for option
             argument description and examples.

         -fenable-tree-pass
         -fenable-tree-pass=range-list
             Enable tree pass pass.  See -fdisable-rtl for the
             description of option arguments.

         Here are some examples showing uses of these options.

                 # disable ccp1 for all functions
                    -fdisable-tree-ccp1
                 # disable complete unroll for function whose cgraph node uid is 1
                    -fenable-tree-cunroll=1
                 # disable gcse2 for functions at the following ranges [1,1],
                 # [300,400], and [400,1000]
                 # disable gcse2 for functions foo and foo2
                    -fdisable-rtl-gcse2=foo,foo2
                 # disable early inlining
                    -fdisable-tree-einline
                 # disable ipa inlining
                    -fdisable-ipa-inline
                 # enable tree full unroll
                    -fenable-tree-unroll

     -dletters
     -fdump-rtl-pass
     -fdump-rtl-pass=filename
         Says to make debugging dumps during compilation at times
         specified by letters.  This is used for debugging the
         RTL-based passes of the compiler.  The file names for
         most of the dumps are made by appending a pass number
         and a word to the dumpname, and the files are created in
         the directory of the output file. In case of =filename
         option, the dump is output on the given file instead of
         the pass numbered dump files. Note that the pass number
         is computed statically as passes get registered into the
         pass manager.  Thus the numbering is not related to the
         dynamic order of execution of passes.  In particular, a
         pass installed by a plugin could have a number over 200
         even if it executed quite early.  dumpname is generated
         from the name of the output file, if explicitly
         specified and it is not an executable, otherwise it is
         the basename of the source file. These switches may have
         different effects when -E is used for preprocessing.

         Debug dumps can be enabled with a -fdump-rtl switch or
         some -d option letters.  Here are the possible letters
         for use in pass and letters, and their meanings:

         -fdump-rtl-alignments
             Dump after branch alignments have been computed.

         -fdump-rtl-asmcons
             Dump after fixing rtl statements that have
             unsatisfied in/out constraints.

         -fdump-rtl-auto_inc_dec
             Dump after auto-inc-dec discovery.  This pass is
             only run on architectures that have auto inc or auto
             dec instructions.

         -fdump-rtl-barriers
             Dump after cleaning up the barrier instructions.

         -fdump-rtl-bbpart
             Dump after partitioning hot and cold basic blocks.

         -fdump-rtl-bbro
             Dump after block reordering.

         -fdump-rtl-btl1
         -fdump-rtl-btl2
             -fdump-rtl-btl1 and -fdump-rtl-btl2 enable dumping
             after the two branch target load optimization
             passes.

         -fdump-rtl-bypass
             Dump after jump bypassing and control flow
             optimizations.

         -fdump-rtl-combine
             Dump after the RTL instruction combination pass.

         -fdump-rtl-compgotos
             Dump after duplicating the computed gotos.

         -fdump-rtl-ce1
         -fdump-rtl-ce2
         -fdump-rtl-ce3
             -fdump-rtl-ce1, -fdump-rtl-ce2, and -fdump-rtl-ce3
             enable dumping after the three if conversion passes.

         -fdump-rtl-cprop_hardreg
             Dump after hard register copy propagation.

         -fdump-rtl-csa
             Dump after combining stack adjustments.

         -fdump-rtl-cse1
         -fdump-rtl-cse2
             -fdump-rtl-cse1 and -fdump-rtl-cse2 enable dumping
             after the two common subexpression elimination
             passes.

         -fdump-rtl-dce
             Dump after the standalone dead code elimination
             passes.

         -fdump-rtl-dbr
             Dump after delayed branch scheduling.

         -fdump-rtl-dce1
         -fdump-rtl-dce2
             -fdump-rtl-dce1 and -fdump-rtl-dce2 enable dumping
             after the two dead store elimination passes.

         -fdump-rtl-eh
             Dump after finalization of EH handling code.

         -fdump-rtl-eh_ranges
             Dump after conversion of EH handling range regions.

         -fdump-rtl-expand
             Dump after RTL generation.

         -fdump-rtl-fwprop1
         -fdump-rtl-fwprop2
             -fdump-rtl-fwprop1 and -fdump-rtl-fwprop2 enable
             dumping after the two forward propagation passes.

         -fdump-rtl-gcse1
         -fdump-rtl-gcse2
             -fdump-rtl-gcse1 and -fdump-rtl-gcse2 enable dumping
             after global common subexpression elimination.

         -fdump-rtl-init-regs
             Dump after the initialization of the registers.

         -fdump-rtl-initvals
             Dump after the computation of the initial value
             sets.

         -fdump-rtl-into_cfglayout
             Dump after converting to cfglayout mode.

         -fdump-rtl-ira
             Dump after iterated register allocation.

         -fdump-rtl-jump
             Dump after the second jump optimization.

         -fdump-rtl-loop2
             -fdump-rtl-loop2 enables dumping after the rtl loop
             optimization passes.

         -fdump-rtl-mach
             Dump after performing the machine dependent
             reorganization pass, if that pass exists.

         -fdump-rtl-mode_sw
             Dump after removing redundant mode switches.

         -fdump-rtl-rnreg
             Dump after register renumbering.

         -fdump-rtl-outof_cfglayout
             Dump after converting from cfglayout mode.

         -fdump-rtl-peephole2
             Dump after the peephole pass.

         -fdump-rtl-postreload
             Dump after post-reload optimizations.

         -fdump-rtl-pro_and_epilogue
             Dump after generating the function prologues and
             epilogues.

         -fdump-rtl-regmove
             Dump after the register move pass.

         -fdump-rtl-sched1
         -fdump-rtl-sched2
             -fdump-rtl-sched1 and -fdump-rtl-sched2 enable
             dumping after the basic block scheduling passes.

         -fdump-rtl-see
             Dump after sign extension elimination.

         -fdump-rtl-seqabstr
             Dump after common sequence discovery.

         -fdump-rtl-shorten
             Dump after shortening branches.

         -fdump-rtl-sibling
             Dump after sibling call optimizations.

         -fdump-rtl-split1
         -fdump-rtl-split2
         -fdump-rtl-split3
         -fdump-rtl-split4
         -fdump-rtl-split5

             -fdump-rtl-split1, -fdump-rtl-split2,
             -fdump-rtl-split3, -fdump-rtl-split4 and
             -fdump-rtl-split5 enable dumping after five rounds
             of instruction splitting.

         -fdump-rtl-sms
             Dump after modulo scheduling.  This pass is only run
             on some architectures.

         -fdump-rtl-stack
             Dump after conversion from GCC's "flat register
             file" registers to the x87's stack-like registers.
             This pass is only run on x86 variants.

         -fdump-rtl-subreg1
         -fdump-rtl-subreg2
             -fdump-rtl-subreg1 and -fdump-rtl-subreg2 enable
             dumping after the two subreg expansion passes.

         -fdump-rtl-unshare
             Dump after all rtl has been unshared.

         -fdump-rtl-vartrack
             Dump after variable tracking.

         -fdump-rtl-vregs
             Dump after converting virtual registers to hard
             registers.

         -fdump-rtl-web
             Dump after live range splitting.

         -fdump-rtl-regclass
         -fdump-rtl-subregs_of_mode_init
         -fdump-rtl-subregs_of_mode_finish
         -fdump-rtl-dfinit
         -fdump-rtl-dfinish
             These dumps are defined but always produce empty
             files.

         -da
         -fdump-rtl-all
             Produce all the dumps listed above.

         -dA Annotate the assembler output with miscellaneous
             debugging information.

         -dD Dump all macro definitions, at the end of
             preprocessing, in addition to normal output.

         -dH Produce a core dump whenever an error occurs.
         -dp Annotate the assembler output with a comment
             indicating which pattern and alternative is used.
             The length of each instruction is also printed.

         -dP Dump the RTL in the assembler output as a comment
             before each instruction.  Also turns on -dp
             annotation.

         -dx Just generate RTL for a function instead of
             compiling it.  Usually used with -fdump-rtl-expand.

     -fdump-noaddr
         When doing debugging dumps, suppress address output.
         This makes it more feasible to use diff on debugging
         dumps for compiler invocations with different compiler
         binaries and/or different text / bss / data / heap /
         stack / dso start locations.

     -fdump-unnumbered
         When doing debugging dumps, suppress instruction numbers
         and address output.  This makes it more feasible to use
         diff on debugging dumps for compiler invocations with
         different options, in particular with and without -g.

     -fdump-unnumbered-links
         When doing debugging dumps (see -d option above),
         suppress instruction numbers for the links to the
         previous and next instructions in a sequence.

     -fdump-translation-unit (C++ only)
     -fdump-translation-unit-options (C++ only)
         Dump a representation of the tree structure for the
         entire translation unit to a file.  The file name is
         made by appending .tu to the source file name, and the
         file is created in the same directory as the output
         file.  If the -options form is used, options controls
         the details of the dump as described for the -fdump-tree
         options.

     -fdump-class-hierarchy (C++ only)
     -fdump-class-hierarchy-options (C++ only)
         Dump a representation of each class's hierarchy and
         virtual function table layout to a file.  The file name
         is made by appending .class to the source file name, and
         the file is created in the same directory as the output
         file.  If the -options form is used, options controls
         the details of the dump as described for the -fdump-tree
         options.

     -fdump-ipa-switch
         Control the dumping at various stages of inter-
         procedural analysis language tree to a file.  The file
         name is generated by appending a switch specific suffix
         to the source file name, and the file is created in the
         same directory as the output file.  The following dumps
         are possible:

         all Enables all inter-procedural analysis dumps.

         cgraph
             Dumps information about call-graph optimization,
             unused function removal, and inlining decisions.

         inline
             Dump after function inlining.

     -fdump-passes
         Dump the list of optimization passes that are turned on
         and off by the current command-line options.

     -fdump-statistics-option
         Enable and control dumping of pass statistics in a
         separate file.  The file name is generated by appending
         a suffix ending in .statistics to the source file name,
         and the file is created in the same directory as the
         output file.  If the -option form is used, -stats causes
         counters to be summed over the whole compilation unit
         while -details dumps every event as the passes generate
         them.  The default with no option is to sum counters for
         each function compiled.

     -fdump-tree-switch
     -fdump-tree-switch-options
     -fdump-tree-switch-options=filename
         Control the dumping at various stages of processing the
         intermediate language tree to a file.  The file name is
         generated by appending a switch-specific suffix to the
         source file name, and the file is created in the same
         directory as the output file. In case of =filename
         option, the dump is output on the given file instead of
         the auto named dump files.  If the -options form is
         used, options is a list of - separated options which
         control the details of the dump.  Not all options are
         applicable to all dumps; those that are not meaningful
         are ignored.  The following options are available

         address
             Print the address of each node.  Usually this is not
             meaningful as it changes according to the
             environment and source file.  Its primary use is for
             tying up a dump file with a debug environment.

         asmname
             If "DECL_ASSEMBLER_NAME" has been set for a given
             decl, use that in the dump instead of "DECL_NAME".
             Its primary use is ease of use working backward from
             mangled names in the assembly file.

         slim
             When dumping front-end intermediate representations,
             inhibit dumping of members of a scope or body of a
             function merely because that scope has been reached.
             Only dump such items when they are directly
             reachable by some other path.

             When dumping pretty-printed trees, this option
             inhibits dumping the bodies of control structures.

             When dumping RTL, print the RTL in slim (condensed)
             form instead of the default LISP-like
             representation.

         raw Print a raw representation of the tree.  By default,
             trees are pretty-printed into a C-like
             representation.

         details
             Enable more detailed dumps (not honored by every
             dump option). Also include information from the
             optimization passes.

         stats
             Enable dumping various statistics about the pass
             (not honored by every dump option).

         blocks
             Enable showing basic block boundaries (disabled in
             raw dumps).

         graph
             For each of the other indicated dump files
             (-fdump-rtl-pass), dump a representation of the
             control flow graph suitable for viewing with
             GraphViz to file.passid.pass.dot.  Each function in
             the file is pretty-printed as a subgraph, so that
             GraphViz can render them all in a single plot.

             This option currently only works for RTL dumps, and
             the RTL is always dumped in slim form.

         vops
             Enable showing virtual operands for every statement.

         lineno
             Enable showing line numbers for statements.

         uid Enable showing the unique ID ("DECL_UID") for each
             variable.

         verbose
             Enable showing the tree dump for each statement.

         eh  Enable showing the EH region number holding each
             statement.

         scev
             Enable showing scalar evolution analysis details.

         optimized
             Enable showing optimization information (only
             available in certain passes).

         missed
             Enable showing missed optimization information (only
             available in certain passes).

         notes
             Enable other detailed optimization information (only
             available in certain passes).

         =filename
             Instead of an auto named dump file, output into the
             given file name. The file names stdout and stderr
             are treated specially and are considered already
             open standard streams. For example,

                     gcc -O2 -ftree-vectorize -fdump-tree-vect-blocks=foo.dump
                          -fdump-tree-pre=stderr file.c

             outputs vectorizer dump into foo.dump, while the PRE
             dump is output on to stderr. If two conflicting dump
             filenames are given for the same pass, then the
             latter option overrides the earlier one.

         all Turn on all options, except raw, slim, verbose and
             lineno.

         optall
             Turn on all optimization options, i.e., optimized,
             missed, and note.

         The following tree dumps are possible:

         original
             Dump before any tree based optimization, to
             file.original.

         optimized

             Dump after all tree based optimization, to
             file.optimized.

         gimple
             Dump each function before and after the
             gimplification pass to a file.  The file name is
             made by appending .gimple to the source file name.

         cfg Dump the control flow graph of each function to a
             file.  The file name is made by appending .cfg to
             the source file name.

         ch  Dump each function after copying loop headers.  The
             file name is made by appending .ch to the source
             file name.

         ssa Dump SSA related information to a file.  The file
             name is made by appending .ssa to the source file
             name.

         alias
             Dump aliasing information for each function.  The
             file name is made by appending .alias to the source
             file name.

         ccp Dump each function after CCP.  The file name is made
             by appending .ccp to the source file name.

         storeccp
             Dump each function after STORE-CCP.  The file name
             is made by appending .storeccp to the source file
             name.

         pre Dump trees after partial redundancy elimination.
             The file name is made by appending .pre to the
             source file name.

         fre Dump trees after full redundancy elimination.  The
             file name is made by appending .fre to the source
             file name.

         copyprop
             Dump trees after copy propagation.  The file name is
             made by appending .copyprop to the source file name.

         store_copyprop
             Dump trees after store copy-propagation.  The file
             name is made by appending .store_copyprop to the
             source file name.

         dce Dump each function after dead code elimination.  The
             file name is made by appending .dce to the source
             file name.

         mudflap
             Dump each function after adding mudflap
             instrumentation.  The file name is made by appending
             .mudflap to the source file name.

         sra Dump each function after performing scalar
             replacement of aggregates.  The file name is made by
             appending .sra to the source file name.

         sink
             Dump each function after performing code sinking.
             The file name is made by appending .sink to the
             source file name.

         dom Dump each function after applying dominator tree
             optimizations.  The file name is made by appending
             .dom to the source file name.

         dse Dump each function after applying dead store
             elimination.  The file name is made by appending
             .dse to the source file name.

         phiopt
             Dump each function after optimizing PHI nodes into
             straightline code.  The file name is made by
             appending .phiopt to the source file name.

         forwprop
             Dump each function after forward propagating single
             use variables.  The file name is made by appending
             .forwprop to the source file name.

         copyrename
             Dump each function after applying the copy rename
             optimization.  The file name is made by appending
             .copyrename to the source file name.

         nrv Dump each function after applying the named return
             value optimization on generic trees.  The file name
             is made by appending .nrv to the source file name.

         vect
             Dump each function after applying vectorization of
             loops.  The file name is made by appending .vect to
             the source file name.

         slp Dump each function after applying vectorization of
             basic blocks.  The file name is made by appending
             .slp to the source file name.

         vrp Dump each function after Value Range Propagation
             (VRP).  The file name is made by appending .vrp to
             the source file name.

         all Enable all the available tree dumps with the flags
             provided in this option.

     -fopt-info
     -fopt-info-options
     -fopt-info-options=filename
         Controls optimization dumps from various optimization
         passes. If the -options form is used, options is a list
         of - separated options to select the dump details and
         optimizations.  If options is not specified, it defaults
         to all for details and optall for optimization groups.
         If the filename is not specified, it defaults to stderr.
         Note that the output filename will be overwritten in
         case of multiple translation units. If a combined output
         from multiple translation units is desired, stderr
         should be used instead.

         The options can be divided into two groups, 1) options
         describing the verbosity of the dump, and 2) options
         describing which optimizations should be included. The
         options from both the groups can be freely mixed as they
         are non-overlapping. However, in case of any conflicts,
         the latter options override the earlier options on the
         command line. Though multiple -fopt-info options are
         accepted, only one of them can have =filename. If other
         filenames are provided then all but the first one are
         ignored.

         The dump verbosity has the following options

         optimized
             Print information when an optimization is
             successfully applied. It is up to a pass to decide
             which information is relevant. For example, the
             vectorizer passes print the source location of loops
             which got successfully vectorized.

         missed
             Print information about missed optimizations.
             Individual passes control which information to
             include in the output. For example,

                     gcc -O2 -ftree-vectorize -fopt-info-vec-missed

             will print information about missed optimization
             opportunities from vectorization passes on stderr.

         note

             Print verbose information about optimizations, such
             as certain transformations, more detailed messages
             about decisions etc.

         all Print detailed optimization information. This
             includes optimized, missed, and note.

         The second set of options describes a group of
         optimizations and may include one or more of the
         following.

         ipa Enable dumps from all interprocedural optimizations.

         loop
             Enable dumps from all loop optimizations.

         inline
             Enable dumps from all inlining optimizations.

         vec Enable dumps from all vectorization optimizations.

         For example,

                 gcc -O3 -fopt-info-missed=missed.all

         outputs missed optimization report from all the passes
         into missed.all.

         As another example,

                 gcc -O3 -fopt-info-inline-optimized-missed=inline.txt

         will output information about missed optimizations as
         well as optimized locations from all the inlining passes
         into inline.txt.

         If the filename is provided, then the dumps from all the
         applicable optimizations are concatenated into the
         filename.  Otherwise the dump is output onto stderr. If
         options is omitted, it defaults to all-optall, which
         means dump all available optimization info from all the
         passes. In the following example, all optimization info
         is output on to stderr.

                 gcc -O3 -fopt-info

         Note that -fopt-info-vec-missed behaves the same as
         -fopt-info-missed-vec.

         As another example, consider

                 gcc -fopt-info-vec-missed=vec.miss -fopt-info-loop-optimized=loop.opt

         Here the two output filenames vec.miss and loop.opt are
         in conflict since only one output file is allowed. In
         this case, only the first option takes effect and the
         subsequent options are ignored. Thus only the vec.miss
         is produced which cotaints dumps from the vectorizer
         about missed opportunities.

     -ftree-vectorizer-verbose=n
         This option is deprecated and is implemented in terms of
         -fopt-info. Please use -fopt-info-kind form instead,
         where kind is one of the valid opt-info options. It
         prints additional optimization information.  For n=0 no
         diagnostic information is reported.  If n=1 the
         vectorizer reports each loop that got vectorized, and
         the total number of loops that got vectorized.  If n=2
         the vectorizer reports locations which could not be
         vectorized and the reasons for those. For any higher
         verbosity levels all the analysis and transformation
         information from the vectorizer is reported.

         Note that the information output by
         -ftree-vectorizer-verbose option is sent to stderr. If
         the equivalent form -fopt-info-options=filename is used
         then the output is sent into filename instead.

     -frandom-seed=string
         This option provides a seed that GCC uses in place of
         random numbers in generating certain symbol names that
         have to be different in every compiled file.  It is also
         used to place unique stamps in coverage data files and
         the object files that produce them.  You can use the
         -frandom-seed option to produce reproducibly identical
         object files.

         The string should be different for every file you
         compile.

     -fsched-verbose=n
         On targets that use instruction scheduling, this option
         controls the amount of debugging output the scheduler
         prints.  This information is written to standard error,
         unless -fdump-rtl-sched1 or -fdump-rtl-sched2 is
         specified, in which case it is output to the usual dump
         listing file, .sched1 or .sched2 respectively.  However
         for n greater than nine, the output is always printed to
         standard error.

         For n greater than zero, -fsched-verbose outputs the
         same information as -fdump-rtl-sched1 and
         -fdump-rtl-sched2.  For n greater than one, it also
         output basic block probabilities, detailed ready list
         information and unit/insn info.  For n greater than two,
         it includes RTL at abort point, control-flow and regions
         info.  And for n over four, -fsched-verbose also
         includes dependence info.

     -save-temps
     -save-temps=cwd
         Store the usual "temporary" intermediate files
         permanently; place them in the current directory and
         name them based on the source file.  Thus, compiling
         foo.c with -c -save-temps produces files foo.i and
         foo.s, as well as foo.o.  This creates a preprocessed
         foo.i output file even though the compiler now normally
         uses an integrated preprocessor.

         When used in combination with the -x command-line
         option, -save-temps is sensible enough to avoid over
         writing an input source file with the same extension as
         an intermediate file.  The corresponding intermediate
         file may be obtained by renaming the source file before
         using -save-temps.

         If you invoke GCC in parallel, compiling several
         different source files that share a common base name in
         different subdirectories or the same source file
         compiled for multiple output destinations, it is likely
         that the different parallel compilers will interfere
         with each other, and overwrite the temporary files.  For
         instance:

                 gcc -save-temps -o outdir1/foo.o indir1/foo.c&
                 gcc -save-temps -o outdir2/foo.o indir2/foo.c&

         may result in foo.i and foo.o being written to
         simultaneously by both compilers.

     -save-temps=obj
         Store the usual "temporary" intermediate files
         permanently.  If the -o option is used, the temporary
         files are based on the object file.  If the -o option is
         not used, the -save-temps=obj switch behaves like
         -save-temps.

         For example:

                 gcc -save-temps=obj -c foo.c
                 gcc -save-temps=obj -c bar.c -o dir/xbar.o
                 gcc -save-temps=obj foobar.c -o dir2/yfoobar

         creates foo.i, foo.s, dir/xbar.i, dir/xbar.s,
         dir2/yfoobar.i, dir2/yfoobar.s, and dir2/yfoobar.o.

     -time[=file]

         Report the CPU time taken by each subprocess in the
         compilation sequence.  For C source files, this is the
         compiler proper and assembler (plus the linker if
         linking is done).

         Without the specification of an output file, the output
         looks like this:

                 # cc1 0.12 0.01
                 # as 0.00 0.01

         The first number on each line is the "user time", that
         is time spent executing the program itself.  The second
         number is "system time", time spent executing operating
         system routines on behalf of the program.  Both numbers
         are in seconds.

         With the specification of an output file, the output is
         appended to the named file, and it looks like this:

                 0.12 0.01 cc1 <options>
                 0.00 0.01 as <options>

         The "user time" and the "system time" are moved before
         the program name, and the options passed to the program
         are displayed, so that one can later tell what file was
         being compiled, and with which options.

     -fvar-tracking
         Run variable tracking pass.  It computes where variables
         are stored at each position in code.  Better debugging
         information is then generated (if the debugging
         information format supports this information).

         It is enabled by default when compiling with
         optimization (-Os, -O, -O2, ...), debugging information
         (-g) and the debug info format supports it.

     -fvar-tracking-assignments
         Annotate assignments to user variables early in the
         compilation and attempt to carry the annotations over
         throughout the compilation all the way to the end, in an
         attempt to improve debug information while optimizing.
         Use of -gdwarf-4 is recommended along with it.

         It can be enabled even if var-tracking is disabled, in
         which case annotations are created and maintained, but
         discarded at the end.

     -fvar-tracking-assignments-toggle
         Toggle -fvar-tracking-assignments, in the same way that
         -gtoggle toggles -g.

     -print-file-name=library
         Print the full absolute name of the library file library
         that would be used when linking---and don't do anything
         else.  With this option, GCC does not compile or link
         anything; it just prints the file name.

     -print-multi-directory
         Print the directory name corresponding to the multilib
         selected by any other switches present in the command
         line.  This directory is supposed to exist in
         GCC_EXEC_PREFIX.

     -print-multi-lib
         Print the mapping from multilib directory names to
         compiler switches that enable them.  The directory name
         is separated from the switches by ;, and each switch
         starts with an @ instead of the -, without spaces
         between multiple switches.  This is supposed to ease
         shell processing.

     -print-multi-os-directory
         Print the path to OS libraries for the selected
         multilib, relative to some lib subdirectory.  If OS
         libraries are present in the lib subdirectory and no
         multilibs are used, this is usually just ., if OS
         libraries are present in libsuffix sibling directories
         this prints e.g. ../lib64, ../lib or ../lib32, or if OS
         libraries are present in lib/subdir subdirectories it
         prints e.g. amd64, sparcv9 or ev6.

     -print-multiarch
         Print the path to OS libraries for the selected
         multiarch, relative to some lib subdirectory.

     -print-prog-name=program
         Like -print-file-name, but searches for a program such
         as cpp.

     -print-libgcc-file-name
         Same as -print-file-name=libgcc.a.

         This is useful when you use -nostdlib or -nodefaultlibs
         but you do want to link with libgcc.a.  You can do:

                 gcc -nostdlib <files>... `gcc -print-libgcc-file-name`

     -print-search-dirs
         Print the name of the configured installation directory
         and a list of program and library directories gcc
         searches---and don't do anything else.

         This is useful when gcc prints the error message
         installation problem, cannot exec cpp0: No such file or
         directory.  To resolve this you either need to put cpp0
         and the other compiler components where gcc expects to
         find them, or you can set the environment variable
         GCC_EXEC_PREFIX to the directory where you installed
         them.  Don't forget the trailing /.

     -print-sysroot
         Print the target sysroot directory that is used during
         compilation.  This is the target sysroot specified
         either at configure time or using the --sysroot option,
         possibly with an extra suffix that depends on
         compilation options.  If no target sysroot is specified,
         the option prints nothing.

     -print-sysroot-headers-suffix
         Print the suffix added to the target sysroot when
         searching for headers, or give an error if the compiler
         is not configured with such a suffix---and don't do
         anything else.

     -dumpmachine
         Print the compiler's target machine (for example,
         i686-pc-linux-gnu)---and don't do anything else.

     -dumpversion
         Print the compiler version (for example, 3.0)---and
         don't do anything else.

     -dumpspecs
         Print the compiler's built-in specs---and don't do
         anything else.  (This is used when GCC itself is being
         built.)

     -fno-eliminate-unused-debug-types
         Normally, when producing DWARF 2 output, GCC avoids
         producing debug symbol output for types that are nowhere
         used in the source file being compiled.  Sometimes it is
         useful to have GCC emit debugging information for all
         types declared in a compilation unit, regardless of
         whether or not they are actually used in that
         compilation unit, for example if, in the debugger, you
         want to cast a value to a type that is not actually used
         in your program (but is declared).  More often, however,
         this results in a significant amount of wasted space.

  Options That Control Optimization
     These options control various sorts of optimizations.

     Without any optimization option, the compiler's goal is to
     reduce the cost of compilation and to make debugging produce
     the expected results.  Statements are independent: if you
     stop the program with a breakpoint between statements, you
     can then assign a new value to any variable or change the
     program counter to any other statement in the function and
     get exactly the results you expect from the source code.

     Turning on optimization flags makes the compiler attempt to
     improve the performance and/or code size at the expense of
     compilation time and possibly the ability to debug the
     program.

     The compiler performs optimization based on the knowledge it
     has of the program.  Compiling multiple files at once to a
     single output file mode allows the compiler to use
     information gained from all of the files when compiling each
     of them.

     Not all optimizations are controlled directly by a flag.
     Only optimizations that have a flag are listed in this
     section.

     Most optimizations are only enabled if an -O level is set on
     the command line.  Otherwise they are disabled, even if
     individual optimization flags are specified.

     Depending on the target and how GCC was configured, a
     slightly different set of optimizations may be enabled at
     each -O level than those listed here.  You can invoke GCC
     with -Q --help=optimizers to find out the exact set of
     optimizations that are enabled at each level.

     -O
     -O1 Optimize.  Optimizing compilation takes somewhat more
         time, and a lot more memory for a large function.

         With -O, the compiler tries to reduce code size and
         execution time, without performing any optimizations
         that take a great deal of compilation time.

         -O turns on the following optimization flags:

         -fauto-inc-dec -fcompare-elim -fcprop-registers -fdce
         -fdefer-pop -fdelayed-branch -fdse
         -fguess-branch-probability -fif-conversion2
         -fif-conversion -fipa-pure-const -fipa-profile
         -fipa-reference -fmerge-constants -fsplit-wide-types
         -ftree-bit-ccp -ftree-builtin-call-dce -ftree-ccp
         -ftree-ch -ftree-copyrename -ftree-dce
         -ftree-dominator-opts -ftree-dse -ftree-forwprop
         -ftree-fre -ftree-phiprop -ftree-slsr -ftree-sra
         -ftree-pta -ftree-ter -funit-at-a-time

         -O also turns on -fomit-frame-pointer on machines where
         doing so does not interfere with debugging.

     -O2 Optimize even more.  GCC performs nearly all supported
         optimizations that do not involve a space-speed
         tradeoff.  As compared to -O, this option increases both
         compilation time and the performance of the generated
         code.

         -O2 turns on all optimization flags specified by -O.  It
         also turns on the following optimization flags:
         -fthread-jumps -falign-functions  -falign-jumps
         -falign-loops  -falign-labels -fcaller-saves
         -fcrossjumping -fcse-follow-jumps  -fcse-skip-blocks
         -fdelete-null-pointer-checks -fdevirtualize
         -fexpensive-optimizations -fgcse  -fgcse-lm
         -fhoist-adjacent-loads -finline-small-functions
         -findirect-inlining -fipa-sra -foptimize-sibling-calls
         -fpartial-inlining -fpeephole2 -fregmove
         -freorder-blocks  -freorder-functions
         -frerun-cse-after-loop -fsched-interblock  -fsched-spec
         -fschedule-insns  -fschedule-insns2 -fstrict-aliasing
         -fstrict-overflow -ftree-switch-conversion
         -ftree-tail-merge -ftree-pre -ftree-vrp

         Please note the warning under -fgcse about invoking -O2
         on programs that use computed gotos.

     -O3 Optimize yet more.  -O3 turns on all optimizations
         specified by -O2 and also turns on the
         -finline-functions, -funswitch-loops,
         -fpredictive-commoning, -fgcse-after-reload,
         -ftree-vectorize, -fvect-cost-model, -ftree-partial-pre
         and -fipa-cp-clone options.

     -O0 Reduce compilation time and make debugging produce the
         expected results.  This is the default.

     -Os Optimize for size.  -Os enables all -O2 optimizations
         that do not typically increase code size.  It also
         performs further optimizations designed to reduce code
         size.

         -Os disables the following optimization flags:
         -falign-functions  -falign-jumps  -falign-loops
         -falign-labels  -freorder-blocks
         -freorder-blocks-and-partition -fprefetch-loop-arrays
         -ftree-vect-loop-version

     -Ofast
         Disregard strict standards compliance.  -Ofast enables
         all -O3 optimizations.  It also enables optimizations
         that are not valid for all standard-compliant programs.

         It turns on -ffast-math and the Fortran-specific
         -fno-protect-parens and -fstack-arrays.

     -Og Optimize debugging experience.  -Og enables
         optimizations that do not interfere with debugging. It
         should be the optimization level of choice for the
         standard edit-compile-debug cycle, offering a reasonable
         level of optimization while maintaining fast compilation
         and a good debugging experience.

         If you use multiple -O options, with or without level
         numbers, the last such option is the one that is
         effective.

     Options of the form -fflag specify machine-independent
     flags.  Most flags have both positive and negative forms;
     the negative form of -ffoo is -fno-foo.  In the table below,
     only one of the forms is listed---the one you typically use.
     You can figure out the other form by either removing no- or
     adding it.

     The following options control specific optimizations.  They
     are either activated by -O options or are related to ones
     that are.  You can use the following flags in the rare cases
     when "fine-tuning" of optimizations to be performed is
     desired.

     -fno-default-inline
         Do not make member functions inline by default merely
         because they are defined inside the class scope (C++
         only).  Otherwise, when you specify -O, member functions
         defined inside class scope are compiled inline by
         default; i.e., you don't need to add inline in front of
         the member function name.

     -fno-defer-pop
         Always pop the arguments to each function call as soon
         as that function returns.  For machines that must pop
         arguments after a function call, the compiler normally
         lets arguments accumulate on the stack for several
         function calls and pops them all at once.

         Disabled at levels -O, -O2, -O3, -Os.

     -fforward-propagate
         Perform a forward propagation pass on RTL.  The pass
         tries to combine two instructions and checks if the
         result can be simplified.  If loop unrolling is active,
         two passes are performed and the second is scheduled
         after loop unrolling.

         This option is enabled by default at optimization levels
         -O, -O2, -O3, -Os.

     -ffp-contract=style
         -ffp-contract=off disables floating-point expression
         contraction.  -ffp-contract=fast enables floating-point
         expression contraction such as forming of fused
         multiply-add operations if the target has native support
         for them.  -ffp-contract=on enables floating-point
         expression contraction if allowed by the language
         standard.  This is currently not implemented and treated
         equal to -ffp-contract=off.

         The default is -ffp-contract=fast.

     -fomit-frame-pointer
         Don't keep the frame pointer in a register for functions
         that don't need one.  This avoids the instructions to
         save, set up and restore frame pointers; it also makes
         an extra register available in many functions.  It also
         makes debugging impossible on some machines.

         On some machines, such as the VAX, this flag has no
         effect, because the standard calling sequence
         automatically handles the frame pointer and nothing is
         saved by pretending it doesn't exist.  The machine-
         description macro "FRAME_POINTER_REQUIRED" controls
         whether a target machine supports this flag.

         Starting with GCC version 4.6, the default setting (when
         not optimizing for size) for 32-bit GNU/Linux x86 and
         32-bit Darwin x86 targets has been changed to
         -fomit-frame-pointer.  The default can be reverted to
         -fno-omit-frame-pointer by configuring GCC with the
         --enable-frame-pointer configure option.

         Enabled at levels -O, -O2, -O3, -Os.

     -foptimize-sibling-calls
         Optimize sibling and tail recursive calls.

         Enabled at levels -O2, -O3, -Os.

     -fno-inline
         Do not expand any functions inline apart from those
         marked with the "always_inline" attribute.  This is the
         default when not optimizing.

         Single functions can be exempted from inlining by
         marking them with the "noinline" attribute.

     -finline-small-functions
         Integrate functions into their callers when their body
         is smaller than expected function call code (so overall
         size of program gets smaller).  The compiler
         heuristically decides which functions are simple enough
         to be worth integrating in this way.  This inlining
         applies to all functions, even those not declared
         inline.

         Enabled at level -O2.

     -findirect-inlining
         Inline also indirect calls that are discovered to be
         known at compile time thanks to previous inlining.  This
         option has any effect only when inlining itself is
         turned on by the -finline-functions or
         -finline-small-functions options.

         Enabled at level -O2.

     -finline-functions
         Consider all functions for inlining, even if they are
         not declared inline.  The compiler heuristically decides
         which functions are worth integrating in this way.

         If all calls to a given function are integrated, and the
         function is declared "static", then the function is
         normally not output as assembler code in its own right.

         Enabled at level -O3.

     -finline-functions-called-once
         Consider all "static" functions called once for inlining
         into their caller even if they are not marked "inline".
         If a call to a given function is integrated, then the
         function is not output as assembler code in its own
         right.

         Enabled at levels -O1, -O2, -O3 and -Os.

     -fearly-inlining
         Inline functions marked by "always_inline" and functions
         whose body seems smaller than the function call overhead
         early before doing -fprofile-generate instrumentation
         and real inlining pass.  Doing so makes profiling
         significantly cheaper and usually inlining faster on
         programs having large chains of nested wrapper
         functions.

         Enabled by default.

     -fipa-sra
         Perform interprocedural scalar replacement of
         aggregates, removal of unused parameters and replacement
         of parameters passed by reference by parameters passed
         by value.

         Enabled at levels -O2, -O3 and -Os.

     -finline-limit=n
         By default, GCC limits the size of functions that can be
         inlined.  This flag allows coarse control of this limit.
         n is the size of functions that can be inlined in number
         of pseudo instructions.

         Inlining is actually controlled by a number of
         parameters, which may be specified individually by using
         --param name=value.  The -finline-limit=n option sets
         some of these parameters as follows:

         max-inline-insns-single
             is set to n/2.

         max-inline-insns-auto
             is set to n/2.

         See below for a documentation of the individual
         parameters controlling inlining and for the defaults of
         these parameters.

         Note: there may be no value to -finline-limit that
         results in default behavior.

         Note: pseudo instruction represents, in this particular
         context, an abstract measurement of function's size.  In
         no way does it represent a count of assembly
         instructions and as such its exact meaning might change
         from one release to an another.

     -fno-keep-inline-dllexport
         This is a more fine-grained version of
         -fkeep-inline-functions, which applies only to functions
         that are declared using the "dllexport" attribute or
         declspec

     -fkeep-inline-functions
         In C, emit "static" functions that are declared "inline"
         into the object file, even if the function has been
         inlined into all of its callers.  This switch does not
         affect functions using the "extern inline" extension in
         GNU C90.  In C++, emit any and all inline functions into
         the object file.

     -fkeep-static-consts
         Emit variables declared "static const" when optimization
         isn't turned on, even if the variables aren't
         referenced.

         GCC enables this option by default.  If you want to
         force the compiler to check if a variable is referenced,
         regardless of whether or not optimization is turned on,
         use the -fno-keep-static-consts option.

     -fmerge-constants
         Attempt to merge identical constants (string constants
         and floating-point constants) across compilation units.

         This option is the default for optimized compilation if
         the assembler and linker support it.  Use
         -fno-merge-constants to inhibit this behavior.

         Enabled at levels -O, -O2, -O3, -Os.

     -fmerge-all-constants
         Attempt to merge identical constants and identical
         variables.

         This option implies -fmerge-constants.  In addition to
         -fmerge-constants this considers e.g. even constant
         initialized arrays or initialized constant variables
         with integral or floating-point types.  Languages like C
         or C++ require each variable, including multiple
         instances of the same variable in recursive calls, to
         have distinct locations, so using this option results in
         non-conforming behavior.

     -fmodulo-sched
         Perform swing modulo scheduling immediately before the
         first scheduling pass.  This pass looks at innermost
         loops and reorders their instructions by overlapping
         different iterations.

     -fmodulo-sched-allow-regmoves
         Perform more aggressive SMS-based modulo scheduling with
         register moves allowed.  By setting this flag certain
         anti-dependences edges are deleted, which triggers the
         generation of reg-moves based on the life-range
         analysis.  This option is effective only with
         -fmodulo-sched enabled.

     -fno-branch-count-reg
         Do not use "decrement and branch" instructions on a
         count register, but instead generate a sequence of
         instructions that decrement a register, compare it
         against zero, then branch based upon the result.  This
         option is only meaningful on architectures that support
         such instructions, which include x86, PowerPC, IA-64 and
         S/390.

         The default is -fbranch-count-reg.

     -fno-function-cse
         Do not put function addresses in registers; make each
         instruction that calls a constant function contain the
         function's address explicitly.

         This option results in less efficient code, but some
         strange hacks that alter the assembler output may be
         confused by the optimizations performed when this option
         is not used.

         The default is -ffunction-cse

     -fno-zero-initialized-in-bss
         If the target supports a BSS section, GCC by default
         puts variables that are initialized to zero into BSS.
         This can save space in the resulting code.

         This option turns off this behavior because some
         programs explicitly rely on variables going to the data
         section---e.g., so that the resulting executable can
         find the beginning of that section and/or make
         assumptions based on that.

         The default is -fzero-initialized-in-bss.

     -fmudflap -fmudflapth -fmudflapir
         For front-ends that support it (C and C++), instrument
         all risky pointer/array dereferencing operations, some
         standard library string/heap functions, and some other
         associated constructs with range/validity tests.
         Modules so instrumented should be immune to buffer
         overflows, invalid heap use, and some other classes of
         C/C++ programming errors.  The instrumentation relies on
         a separate runtime library (libmudflap), which is linked
         into a program if -fmudflap is given at link time.
         Run-time behavior of the instrumented program is
         controlled by the MUDFLAP_OPTIONS environment variable.
         See "env MUDFLAP_OPTIONS=-help a.out" for its options.

         Use -fmudflapth instead of -fmudflap to compile and to
         link if your program is multi-threaded.  Use
         -fmudflapir, in addition to -fmudflap or -fmudflapth, if
         instrumentation should ignore pointer reads.  This
         produces less instrumentation (and therefore faster
         execution) and still provides some protection against
         outright memory corrupting writes, but allows
         erroneously read data to propagate within a program.

     -fthread-jumps
         Perform optimizations that check to see if a jump
         branches to a location where another comparison subsumed
         by the first is found.  If so, the first branch is
         redirected to either the destination of the second
         branch or a point immediately following it, depending on
         whether the condition is known to be true or false.

         Enabled at levels -O2, -O3, -Os.

     -fsplit-wide-types
         When using a type that occupies multiple registers, such
         as "long long" on a 32-bit system, split the registers
         apart and allocate them independently.  This normally
         generates better code for those types, but may make
         debugging more difficult.

         Enabled at levels -O, -O2, -O3, -Os.

     -fcse-follow-jumps
         In common subexpression elimination (CSE), scan through
         jump instructions when the target of the jump is not
         reached by any other path.  For example, when CSE
         encounters an "if" statement with an "else" clause, CSE
         follows the jump when the condition tested is false.

         Enabled at levels -O2, -O3, -Os.

     -fcse-skip-blocks
         This is similar to -fcse-follow-jumps, but causes CSE to
         follow jumps that conditionally skip over blocks.  When
         CSE encounters a simple "if" statement with no else
         clause, -fcse-skip-blocks causes CSE to follow the jump
         around the body of the "if".

         Enabled at levels -O2, -O3, -Os.

     -frerun-cse-after-loop
         Re-run common subexpression elimination after loop
         optimizations are performed.

         Enabled at levels -O2, -O3, -Os.

     -fgcse
         Perform a global common subexpression elimination pass.
         This pass also performs global constant and copy
         propagation.

         Note: When compiling a program using computed gotos, a
         GCC extension, you may get better run-time performance
         if you disable the global common subexpression
         elimination pass by adding -fno-gcse to the command
         line.

         Enabled at levels -O2, -O3, -Os.

     -fgcse-lm
         When -fgcse-lm is enabled, global common subexpression
         elimination attempts to move loads that are only killed
         by stores into themselves.  This allows a loop
         containing a load/store sequence to be changed to a load
         outside the loop, and a copy/store within the loop.

         Enabled by default when -fgcse is enabled.

     -fgcse-sm
         When -fgcse-sm is enabled, a store motion pass is run
         after global common subexpression elimination.  This
         pass attempts to move stores out of loops.  When used in
         conjunction with -fgcse-lm, loops containing a
         load/store sequence can be changed to a load before the
         loop and a store after the loop.

         Not enabled at any optimization level.

     -fgcse-las
         When -fgcse-las is enabled, the global common
         subexpression elimination pass eliminates redundant
         loads that come after stores to the same memory location
         (both partial and full redundancies).

         Not enabled at any optimization level.

     -fgcse-after-reload
         When -fgcse-after-reload is enabled, a redundant load
         elimination pass is performed after reload.  The purpose
         of this pass is to clean up redundant spilling.

     -faggressive-loop-optimizations
         This option tells the loop optimizer to use language
         constraints to derive bounds for the number of
         iterations of a loop.  This assumes that loop code does
         not invoke undefined behavior by for example causing
         signed integer overflows or out-of-bound array accesses.
         The bounds for the number of iterations of a loop are
         used to guide loop unrolling and peeling and loop exit
         test optimizations.  This option is enabled by default.

     -funsafe-loop-optimizations
         This option tells the loop optimizer to assume that loop
         indices do not overflow, and that loops with nontrivial
         exit condition are not infinite.  This enables a wider
         range of loop optimizations even if the loop optimizer
         itself cannot prove that these assumptions are valid.
         If you use -Wunsafe-loop-optimizations, the compiler
         warns you if it finds this kind of loop.

     -fcrossjumping
         Perform cross-jumping transformation.  This
         transformation unifies equivalent code and saves code
         size.  The resulting code may or may not perform better
         than without cross-jumping.

         Enabled at levels -O2, -O3, -Os.

     -fauto-inc-dec
         Combine increments or decrements of addresses with
         memory accesses.  This pass is always skipped on
         architectures that do not have instructions to support
         this.  Enabled by default at -O and higher on
         architectures that support this.

     -fdce
         Perform dead code elimination (DCE) on RTL.  Enabled by
         default at -O and higher.

     -fdse
         Perform dead store elimination (DSE) on RTL.  Enabled by
         default at -O and higher.

     -fif-conversion
         Attempt to transform conditional jumps into branch-less
         equivalents.  This includes use of conditional moves,
         min, max, set flags and abs instructions, and some
         tricks doable by standard arithmetics.  The use of
         conditional execution on chips where it is available is
         controlled by "if-conversion2".

         Enabled at levels -O, -O2, -O3, -Os.

     -fif-conversion2
         Use conditional execution (where available) to transform
         conditional jumps into branch-less equivalents.

         Enabled at levels -O, -O2, -O3, -Os.

     -fdelete-null-pointer-checks
         Assume that programs cannot safely dereference null
         pointers, and that no code or data element resides
         there.  This enables simple constant folding
         optimizations at all optimization levels.  In addition,
         other optimization passes in GCC use this flag to
         control global dataflow analyses that eliminate useless
         checks for null pointers; these assume that if a pointer
         is checked after it has already been dereferenced, it
         cannot be null.

         Note however that in some environments this assumption
         is not true.  Use -fno-delete-null-pointer-checks to
         disable this optimization for programs that depend on
         that behavior.

         Some targets, especially embedded ones, disable this
         option at all levels.  Otherwise it is enabled at all
         levels: -O0, -O1, -O2, -O3, -Os.  Passes that use the
         information are enabled independently at different
         optimization levels.

     -fdevirtualize
         Attempt to convert calls to virtual functions to direct
         calls.  This is done both within a procedure and
         interprocedurally as part of indirect inlining
         ("-findirect-inlining") and interprocedural constant
         propagation (-fipa-cp).  Enabled at levels -O2, -O3,
         -Os.

     -fexpensive-optimizations
         Perform a number of minor optimizations that are
         relatively expensive.

         Enabled at levels -O2, -O3, -Os.

     -free
         Attempt to remove redundant extension instructions.
         This is especially helpful for the x86-64 architecture,
         which implicitly zero-extends in 64-bit registers after
         writing to their lower 32-bit half.

         Enabled for x86 at levels -O2, -O3.

     -foptimize-register-move
     -fregmove
         Attempt to reassign register numbers in move
         instructions and as operands of other simple
         instructions in order to maximize the amount of register
         tying.  This is especially helpful on machines with
         two-operand instructions.

         Note -fregmove and -foptimize-register-move are the same
         optimization.

         Enabled at levels -O2, -O3, -Os.

     -fira-algorithm=algorithm
         Use the specified coloring algorithm for the integrated
         register allocator.  The algorithm argument can be
         priority, which specifies Chow's priority coloring, or
         CB, which specifies Chaitin-Briggs coloring.  Chaitin-
         Briggs coloring is not implemented for all
         architectures, but for those targets that do support it,
         it is the default because it generates better code.

     -fira-region=region
         Use specified regions for the integrated register
         allocator.  The region argument should be one of the
         following:

         all Use all loops as register allocation regions.  This
             can give the best results for machines with a small
             and/or irregular register set.

         mixed
             Use all loops except for loops with small register
             pressure as the regions.  This value usually gives
             the best results in most cases and for most
             architectures, and is enabled by default when
             compiling with optimization for speed (-O, -O2,
             ...).

         one Use all functions as a single region. This typically
             results in the smallest code size, and is enabled by
             default for -Os or -O0.

     -fira-hoist-pressure
         Use IRA to evaluate register pressure in the code
         hoisting pass for decisions to hoist expressions.  This
         option usually results in smaller code, but it can slow
         the compiler down.

         This option is enabled at level -Os for all targets.

     -fira-loop-pressure
         Use IRA to evaluate register pressure in loops for
         decisions to move loop invariants.  This option usually
         results in generation of faster and smaller code on
         machines with large register files (>= 32 registers),
         but it can slow the compiler down.

         This option is enabled at level -O3 for some targets.

     -fno-ira-share-save-slots
         Disable sharing of stack slots used for saving call-used
         hard registers living through a call.  Each hard
         register gets a separate stack slot, and as a result
         function stack frames are larger.

     -fno-ira-share-spill-slots
         Disable sharing of stack slots allocated for pseudo-
         registers.  Each pseudo-register that does not get a
         hard register gets a separate stack slot, and as a
         result function stack frames are larger.

     -fira-verbose=n
         Control the verbosity of the dump file for the
         integrated register allocator.  The default value is 5.
         If the value n is greater or equal to 10, the dump
         output is sent to stderr using the same format as n
         minus 10.

     -fdelayed-branch
         If supported for the target machine, attempt to reorder
         instructions to exploit instruction slots available
         after delayed branch instructions.

         Enabled at levels -O, -O2, -O3, -Os.

     -fschedule-insns
         If supported for the target machine, attempt to reorder
         instructions to eliminate execution stalls due to
         required data being unavailable.  This helps machines
         that have slow floating point or memory load
         instructions by allowing other instructions to be issued
         until the result of the load or floating-point
         instruction is required.

         Enabled at levels -O2, -O3.

     -fschedule-insns2
         Similar to -fschedule-insns, but requests an additional
         pass of instruction scheduling after register allocation
         has been done.  This is especially useful on machines
         with a relatively small number of registers and where
         memory load instructions take more than one cycle.

         Enabled at levels -O2, -O3, -Os.

     -fno-sched-interblock
         Don't schedule instructions across basic blocks.  This
         is normally enabled by default when scheduling before
         register allocation, i.e.  with -fschedule-insns or at
         -O2 or higher.

     -fno-sched-spec
         Don't allow speculative motion of non-load instructions.
         This is normally enabled by default when scheduling
         before register allocation, i.e.  with -fschedule-insns
         or at -O2 or higher.

     -fsched-pressure
         Enable register pressure sensitive insn scheduling
         before register allocation.  This only makes sense when
         scheduling before register allocation is enabled, i.e.
         with -fschedule-insns or at -O2 or higher.  Usage of
         this option can improve the generated code and decrease
         its size by preventing register pressure increase above
         the number of available hard registers and subsequent
         spills in register allocation.

     -fsched-spec-load
         Allow speculative motion of some load instructions.
         This only makes sense when scheduling before register
         allocation, i.e. with -fschedule-insns or at -O2 or
         higher.

     -fsched-spec-load-dangerous
         Allow speculative motion of more load instructions.
         This only makes sense when scheduling before register
         allocation, i.e. with -fschedule-insns or at -O2 or
         higher.

     -fsched-stalled-insns
     -fsched-stalled-insns=n
         Define how many insns (if any) can be moved prematurely
         from the queue of stalled insns into the ready list
         during the second scheduling pass.
         -fno-sched-stalled-insns means that no insns are moved
         prematurely, -fsched-stalled-insns=0 means there is no
         limit on how many queued insns can be moved prematurely.
         -fsched-stalled-insns without a value is equivalent to
         -fsched-stalled-insns=1.

     -fsched-stalled-insns-dep
     -fsched-stalled-insns-dep=n
         Define how many insn groups (cycles) are examined for a
         dependency on a stalled insn that is a candidate for
         premature removal from the queue of stalled insns.  This
         has an effect only during the second scheduling pass,
         and only if -fsched-stalled-insns is used.
         -fno-sched-stalled-insns-dep is equivalent to
         -fsched-stalled-insns-dep=0.  -fsched-stalled-insns-dep
         without a value is equivalent to
         -fsched-stalled-insns-dep=1.

     -fsched2-use-superblocks
         When scheduling after register allocation, use
         superblock scheduling.  This allows motion across basic
         block boundaries, resulting in faster schedules.  This
         option is experimental, as not all machine descriptions
         used by GCC model the CPU closely enough to avoid
         unreliable results from the algorithm.

         This only makes sense when scheduling after register
         allocation, i.e. with -fschedule-insns2 or at -O2 or
         higher.

     -fsched-group-heuristic
         Enable the group heuristic in the scheduler.  This
         heuristic favors the instruction that belongs to a
         schedule group.  This is enabled by default when
         scheduling is enabled, i.e. with -fschedule-insns or
         -fschedule-insns2 or at -O2 or higher.

     -fsched-critical-path-heuristic
         Enable the critical-path heuristic in the scheduler.
         This heuristic favors instructions on the critical path.
         This is enabled by default when scheduling is enabled,
         i.e. with -fschedule-insns or -fschedule-insns2 or at
         -O2 or higher.

     -fsched-spec-insn-heuristic
         Enable the speculative instruction heuristic in the
         scheduler.  This heuristic favors speculative
         instructions with greater dependency weakness.  This is
         enabled by default when scheduling is enabled, i.e.
         with -fschedule-insns or -fschedule-insns2 or at -O2 or
         higher.

     -fsched-rank-heuristic
         Enable the rank heuristic in the scheduler.  This
         heuristic favors the instruction belonging to a basic
         block with greater size or frequency.  This is enabled
         by default when scheduling is enabled, i.e.  with
         -fschedule-insns or -fschedule-insns2 or at -O2 or
         higher.

     -fsched-last-insn-heuristic
         Enable the last-instruction heuristic in the scheduler.
         This heuristic favors the instruction that is less
         dependent on the last instruction scheduled.  This is
         enabled by default when scheduling is enabled, i.e. with
         -fschedule-insns or -fschedule-insns2 or at -O2 or
         higher.

     -fsched-dep-count-heuristic
         Enable the dependent-count heuristic in the scheduler.
         This heuristic favors the instruction that has more
         instructions depending on it.  This is enabled by
         default when scheduling is enabled, i.e.  with
         -fschedule-insns or -fschedule-insns2 or at -O2 or
         higher.

     -freschedule-modulo-scheduled-loops
         Modulo scheduling is performed before traditional
         scheduling.  If a loop is modulo scheduled, later
         scheduling passes may change its schedule. Use this
         option to control that behavior.

     -fselective-scheduling
         Schedule instructions using selective scheduling
         algorithm.  Selective scheduling runs instead of the
         first scheduler pass.

     -fselective-scheduling2
         Schedule instructions using selective scheduling
         algorithm.  Selective scheduling runs instead of the
         second scheduler pass.

     -fsel-sched-pipelining
         Enable software pipelining of innermost loops during
         selective scheduling.  This option has no effect unless
         one of -fselective-scheduling or -fselective-scheduling2
         is turned on.

     -fsel-sched-pipelining-outer-loops
         When pipelining loops during selective scheduling, also
         pipeline outer loops.  This option has no effect unless
         -fsel-sched-pipelining is turned on.

     -fshrink-wrap
         Emit function prologues only before parts of the
         function that need it, rather than at the top of the
         function.  This flag is enabled by default at -O and
         higher.

     -fcaller-saves
         Enable allocation of values to registers that are
         clobbered by function calls, by emitting extra
         instructions to save and restore the registers around
         such calls.  Such allocation is done only when it seems
         to result in better code.

         This option is always enabled by default on certain
         machines, usually those which have no call-preserved
         registers to use instead.

         Enabled at levels -O2, -O3, -Os.

     -fcombine-stack-adjustments
         Tracks stack adjustments (pushes and pops) and stack
         memory references and then tries to find ways to combine
         them.

         Enabled by default at -O1 and higher.

     -fconserve-stack
         Attempt to minimize stack usage.  The compiler attempts
         to use less stack space, even if that makes the program
         slower.  This option implies setting the large-stack-
         frame parameter to 100 and the large-stack-frame-growth
         parameter to 400.

     -ftree-reassoc

         Perform reassociation on trees.  This flag is enabled by
         default at -O and higher.

     -ftree-pre
         Perform partial redundancy elimination (PRE) on trees.
         This flag is enabled by default at -O2 and -O3.

     -ftree-partial-pre
         Make partial redundancy elimination (PRE) more
         aggressive.  This flag is enabled by default at -O3.

     -ftree-forwprop
         Perform forward propagation on trees.  This flag is
         enabled by default at -O and higher.

     -ftree-fre
         Perform full redundancy elimination (FRE) on trees.  The
         difference between FRE and PRE is that FRE only
         considers expressions that are computed on all paths
         leading to the redundant computation.  This analysis is
         faster than PRE, though it exposes fewer redundancies.
         This flag is enabled by default at -O and higher.

     -ftree-phiprop
         Perform hoisting of loads from conditional pointers on
         trees.  This pass is enabled by default at -O and
         higher.

     -fhoist-adjacent-loads
         Speculatively hoist loads from both branches of an if-
         then-else if the loads are from adjacent locations in
         the same structure and the target architecture has a
         conditional move instruction.  This flag is enabled by
         default at -O2 and higher.

     -ftree-copy-prop
         Perform copy propagation on trees.  This pass eliminates
         unnecessary copy operations.  This flag is enabled by
         default at -O and higher.

     -fipa-pure-const
         Discover which functions are pure or constant.  Enabled
         by default at -O and higher.

     -fipa-reference
         Discover which static variables do not escape the
         compilation unit.  Enabled by default at -O and higher.

     -fipa-pta
         Perform interprocedural pointer analysis and
         interprocedural modification and reference analysis.
         This option can cause excessive memory and compile-time
         usage on large compilation units.  It is not enabled by
         default at any optimization level.

     -fipa-profile
         Perform interprocedural profile propagation.  The
         functions called only from cold functions are marked as
         cold. Also functions executed once (such as "cold",
         "noreturn", static constructors or destructors) are
         identified. Cold functions and loop less parts of
         functions executed once are then optimized for size.
         Enabled by default at -O and higher.

     -fipa-cp
         Perform interprocedural constant propagation.  This
         optimization analyzes the program to determine when
         values passed to functions are constants and then
         optimizes accordingly.  This optimization can
         substantially increase performance if the application
         has constants passed to functions.  This flag is enabled
         by default at -O2, -Os and -O3.

     -fipa-cp-clone
         Perform function cloning to make interprocedural
         constant propagation stronger.  When enabled,
         interprocedural constant propagation performs function
         cloning when externally visible function can be called
         with constant arguments.  Because this optimization can
         create multiple copies of functions, it may
         significantly increase code size (see --param
         ipcp-unit-growth=value).  This flag is enabled by
         default at -O3.

     -ftree-sink
         Perform forward store motion  on trees.  This flag is
         enabled by default at -O and higher.

     -ftree-bit-ccp
         Perform sparse conditional bit constant propagation on
         trees and propagate pointer alignment information.  This
         pass only operates on local scalar variables and is
         enabled by default at -O and higher.  It requires that
         -ftree-ccp is enabled.

     -ftree-ccp
         Perform sparse conditional constant propagation (CCP) on
         trees.  This pass only operates on local scalar
         variables and is enabled by default at -O and higher.

     -ftree-switch-conversion
         Perform conversion of simple initializations in a switch
         to initializations from a scalar array.  This flag is
         enabled by default at -O2 and higher.

     -ftree-tail-merge
         Look for identical code sequences.  When found, replace
         one with a jump to the other.  This optimization is
         known as tail merging or cross jumping.  This flag is
         enabled by default at -O2 and higher.  The compilation
         time in this pass can be limited using max-tail-merge-
         comparisons parameter and max-tail-merge-iterations
         parameter.

     -ftree-dce
         Perform dead code elimination (DCE) on trees.  This flag
         is enabled by default at -O and higher.

     -ftree-builtin-call-dce
         Perform conditional dead code elimination (DCE) for
         calls to built-in functions that may set "errno" but are
         otherwise side-effect free.  This flag is enabled by
         default at -O2 and higher if -Os is not also specified.

     -ftree-dominator-opts
         Perform a variety of simple scalar cleanups
         (constant/copy propagation, redundancy elimination,
         range propagation and expression simplification) based
         on a dominator tree traversal.  This also performs jump
         threading (to reduce jumps to jumps). This flag is
         enabled by default at -O and higher.

     -ftree-dse
         Perform dead store elimination (DSE) on trees.  A dead
         store is a store into a memory location that is later
         overwritten by another store without any intervening
         loads.  In this case the earlier store can be deleted.
         This flag is enabled by default at -O and higher.

     -ftree-ch
         Perform loop header copying on trees.  This is
         beneficial since it increases effectiveness of code
         motion optimizations.  It also saves one jump.  This
         flag is enabled by default at -O and higher.  It is not
         enabled for -Os, since it usually increases code size.

     -ftree-loop-optimize
         Perform loop optimizations on trees.  This flag is
         enabled by default at -O and higher.

     -ftree-loop-linear
         Perform loop interchange transformations on tree.  Same
         as -floop-interchange.  To use this code transformation,
         GCC has to be configured with --with-ppl and
         --with-cloog to enable the Graphite loop transformation
         infrastructure.

     -floop-interchange
         Perform loop interchange transformations on loops.
         Interchanging two nested loops switches the inner and
         outer loops.  For example, given a loop like:

                 DO J = 1, M
                   DO I = 1, N
                     A(J, I) = A(J, I) * C
                   ENDDO
                 ENDDO

         loop interchange transforms the loop as if it were
         written:

                 DO I = 1, N
                   DO J = 1, M
                     A(J, I) = A(J, I) * C
                   ENDDO
                 ENDDO

         which can be beneficial when "N" is larger than the
         caches, because in Fortran, the elements of an array are
         stored in memory contiguously by column, and the
         original loop iterates over rows, potentially creating
         at each access a cache miss.  This optimization applies
         to all the languages supported by GCC and is not limited
         to Fortran.  To use this code transformation, GCC has to
         be configured with --with-ppl and --with-cloog to enable
         the Graphite loop transformation infrastructure.

     -floop-strip-mine
         Perform loop strip mining transformations on loops.
         Strip mining splits a loop into two nested loops.  The
         outer loop has strides equal to the strip size and the
         inner loop has strides of the original loop within a
         strip.  The strip length can be changed using the loop-
         block-tile-size parameter.  For example, given a loop
         like:

                 DO I = 1, N
                   A(I) = A(I) + C
                 ENDDO

         loop strip mining transforms the loop as if it were
         written:

                 DO II = 1, N, 51
                   DO I = II, min (II + 50, N)
                     A(I) = A(I) + C
                   ENDDO
                 ENDDO

         This optimization applies to all the languages supported
         by GCC and is not limited to Fortran.  To use this code
         transformation, GCC has to be configured with --with-ppl
         and --with-cloog to enable the Graphite loop
         transformation infrastructure.

     -floop-block
         Perform loop blocking transformations on loops.
         Blocking strip mines each loop in the loop nest such
         that the memory accesses of the element loops fit inside
         caches.  The strip length can be changed using the
         loop-block-tile-size parameter.  For example, given a
         loop like:

                 DO I = 1, N
                   DO J = 1, M
                     A(J, I) = B(I) + C(J)
                   ENDDO
                 ENDDO

         loop blocking transforms the loop as if it were written:

                 DO II = 1, N, 51
                   DO JJ = 1, M, 51
                     DO I = II, min (II + 50, N)
                       DO J = JJ, min (JJ + 50, M)
                         A(J, I) = B(I) + C(J)
                       ENDDO
                     ENDDO
                   ENDDO
                 ENDDO

         which can be beneficial when "M" is larger than the
         caches, because the innermost loop iterates over a
         smaller amount of data which can be kept in the caches.
         This optimization applies to all the languages supported
         by GCC and is not limited to Fortran.  To use this code
         transformation, GCC has to be configured with --with-ppl
         and --with-cloog to enable the Graphite loop
         transformation infrastructure.

     -fgraphite-identity
         Enable the identity transformation for graphite.  For
         every SCoP we generate the polyhedral representation and
         transform it back to gimple.  Using -fgraphite-identity
         we can check the costs or benefits of the GIMPLE ->
         GRAPHITE -> GIMPLE transformation.  Some minimal
         optimizations are also performed by the code generator
         CLooG, like index splitting and dead code elimination in
         loops.

     -floop-nest-optimize

         Enable the ISL based loop nest optimizer.  This is a
         generic loop nest optimizer based on the Pluto
         optimization algorithms.  It calculates a loop structure
         optimized for data-locality and parallelism.  This
         option is experimental.

     -floop-parallelize-all
         Use the Graphite data dependence analysis to identify
         loops that can be parallelized.  Parallelize all the
         loops that can be analyzed to not contain loop carried
         dependences without checking that it is profitable to
         parallelize the loops.

     -fcheck-data-deps
         Compare the results of several data dependence
         analyzers.  This option is used for debugging the data
         dependence analyzers.

     -ftree-loop-if-convert
         Attempt to transform conditional jumps in the innermost
         loops to branch-less equivalents.  The intent is to
         remove control-flow from the innermost loops in order to
         improve the ability of the vectorization pass to handle
         these loops.  This is enabled by default if
         vectorization is enabled.

     -ftree-loop-if-convert-stores
         Attempt to also if-convert conditional jumps containing
         memory writes.  This transformation can be unsafe for
         multi-threaded programs as it transforms conditional
         memory writes into unconditional memory writes.  For
         example,

                 for (i = 0; i < N; i++)
                   if (cond)
                     A[i] = expr;

         is transformed to

                 for (i = 0; i < N; i++)
                   A[i] = cond ? expr : A[i];

         potentially producing data races.

     -ftree-loop-distribution
         Perform loop distribution.  This flag can improve cache
         performance on big loop bodies and allow further loop
         optimizations, like parallelization or vectorization, to
         take place.  For example, the loop

                 DO I = 1, N
                   A(I) = B(I) + C
                   D(I) = E(I) * F
                 ENDDO

         is transformed to

                 DO I = 1, N
                    A(I) = B(I) + C
                 ENDDO
                 DO I = 1, N
                    D(I) = E(I) * F
                 ENDDO

     -ftree-loop-distribute-patterns
         Perform loop distribution of patterns that can be code
         generated with calls to a library.  This flag is enabled
         by default at -O3.

         This pass distributes the initialization loops and
         generates a call to memset zero.  For example, the loop

                 DO I = 1, N
                   A(I) = 0
                   B(I) = A(I) + I
                 ENDDO

         is transformed to

                 DO I = 1, N
                    A(I) = 0
                 ENDDO
                 DO I = 1, N
                    B(I) = A(I) + I
                 ENDDO

         and the initialization loop is transformed into a call
         to memset zero.

     -ftree-loop-im
         Perform loop invariant motion on trees.  This pass moves
         only invariants that are hard to handle at RTL level
         (function calls, operations that expand to nontrivial
         sequences of insns).  With -funswitch-loops it also
         moves operands of conditions that are invariant out of
         the loop, so that we can use just trivial invariantness
         analysis in loop unswitching.  The pass also includes
         store motion.

     -ftree-loop-ivcanon
         Create a canonical counter for number of iterations in
         loops for which determining number of iterations
         requires complicated analysis.  Later optimizations then
         may determine the number easily.  Useful especially in
         connection with unrolling.

     -fivopts
         Perform induction variable optimizations (strength
         reduction, induction variable merging and induction
         variable elimination) on trees.

     -ftree-parallelize-loops=n
         Parallelize loops, i.e., split their iteration space to
         run in n threads.  This is only possible for loops whose
         iterations are independent and can be arbitrarily
         reordered.  The optimization is only profitable on
         multiprocessor machines, for loops that are CPU-
         intensive, rather than constrained e.g. by memory
         bandwidth.  This option implies -pthread, and thus is
         only supported on targets that have support for
         -pthread.

     -ftree-pta
         Perform function-local points-to analysis on trees.
         This flag is enabled by default at -O and higher.

     -ftree-sra
         Perform scalar replacement of aggregates.  This pass
         replaces structure references with scalars to prevent
         committing structures to memory too early.  This flag is
         enabled by default at -O and higher.

     -ftree-copyrename
         Perform copy renaming on trees.  This pass attempts to
         rename compiler temporaries to other variables at copy
         locations, usually resulting in variable names which
         more closely resemble the original variables.  This flag
         is enabled by default at -O and higher.

     -ftree-coalesce-inlined-vars
         Tell the copyrename pass (see -ftree-copyrename) to
         attempt to combine small user-defined variables too, but
         only if they were inlined from other functions.  It is a
         more limited form of -ftree-coalesce-vars.  This may
         harm debug information of such inlined variables, but it
         will keep variables of the inlined-into function apart
         from each other, such that they are more likely to
         contain the expected values in a debugging session.
         This was the default in GCC versions older than 4.7.

     -ftree-coalesce-vars
         Tell the copyrename pass (see -ftree-copyrename) to
         attempt to combine small user-defined variables too,
         instead of just compiler temporaries.  This may severely
         limit the ability to debug an optimized program compiled
         with -fno-var-tracking-assignments.  In the negated
         form, this flag prevents SSA coalescing of user
         variables, including inlined ones.  This option is
         enabled by default.

     -ftree-ter
         Perform temporary expression replacement during the
         SSA->normal phase.  Single use/single def temporaries
         are replaced at their use location with their defining
         expression.  This results in non-GIMPLE code, but gives
         the expanders much more complex trees to work on
         resulting in better RTL generation.  This is enabled by
         default at -O and higher.

     -ftree-slsr
         Perform straight-line strength reduction on trees.  This
         recognizes related expressions involving multiplications
         and replaces them by less expensive calculations when
         possible.  This is enabled by default at -O and higher.

     -ftree-vectorize
         Perform loop vectorization on trees. This flag is
         enabled by default at -O3.

     -ftree-slp-vectorize
         Perform basic block vectorization on trees. This flag is
         enabled by default at -O3 and when -ftree-vectorize is
         enabled.

     -ftree-vect-loop-version
         Perform loop versioning when doing loop vectorization on
         trees.  When a loop appears to be vectorizable except
         that data alignment or data dependence cannot be
         determined at compile time, then vectorized and non-
         vectorized versions of the loop are generated along with
         run-time checks for alignment or dependence to control
         which version is executed.  This option is enabled by
         default except at level -Os where it is disabled.

     -fvect-cost-model
         Enable cost model for vectorization.  This option is
         enabled by default at -O3.

     -ftree-vrp
         Perform Value Range Propagation on trees.  This is
         similar to the constant propagation pass, but instead of
         values, ranges of values are propagated.  This allows
         the optimizers to remove unnecessary range checks like
         array bound checks and null pointer checks.  This is
         enabled by default at -O2 and higher.  Null pointer
         check elimination is only done if
         -fdelete-null-pointer-checks is enabled.

     -ftracer
         Perform tail duplication to enlarge superblock size.
         This transformation simplifies the control flow of the
         function allowing other optimizations to do a better
         job.

     -funroll-loops
         Unroll loops whose number of iterations can be
         determined at compile time or upon entry to the loop.
         -funroll-loops implies -frerun-cse-after-loop.  This
         option makes code larger, and may or may not make it run
         faster.

     -funroll-all-loops
         Unroll all loops, even if their number of iterations is
         uncertain when the loop is entered.  This usually makes
         programs run more slowly.  -funroll-all-loops implies
         the same options as -funroll-loops,

     -fsplit-ivs-in-unroller
         Enables expression of values of induction variables in
         later iterations of the unrolled loop using the value in
         the first iteration.  This breaks long dependency
         chains, thus improving efficiency of the scheduling
         passes.

         A combination of -fweb and CSE is often sufficient to
         obtain the same effect.  However, that is not reliable
         in cases where the loop body is more complicated than a
         single basic block.  It also does not work at all on
         some architectures due to restrictions in the CSE pass.

         This optimization is enabled by default.

     -fvariable-expansion-in-unroller
         With this option, the compiler creates multiple copies
         of some local variables when unrolling a loop, which can
         result in superior code.

     -fpartial-inlining
         Inline parts of functions.  This option has any effect
         only when inlining itself is turned on by the
         -finline-functions or -finline-small-functions options.

         Enabled at level -O2.

     -fpredictive-commoning
         Perform predictive commoning optimization, i.e., reusing
         computations (especially memory loads and stores)
         performed in previous iterations of loops.

         This option is enabled at level -O3.

     -fprefetch-loop-arrays
         If supported by the target machine, generate
         instructions to prefetch memory to improve the
         performance of loops that access large arrays.

         This option may generate better or worse code; results
         are highly dependent on the structure of loops within
         the source code.

         Disabled at level -Os.

     -fno-peephole
     -fno-peephole2
         Disable any machine-specific peephole optimizations.
         The difference between -fno-peephole and -fno-peephole2
         is in how they are implemented in the compiler; some
         targets use one, some use the other, a few use both.

         -fpeephole is enabled by default.  -fpeephole2 enabled
         at levels -O2, -O3, -Os.

     -fno-guess-branch-probability
         Do not guess branch probabilities using heuristics.

         GCC uses heuristics to guess branch probabilities if
         they are not provided by profiling feedback
         (-fprofile-arcs).  These heuristics are based on the
         control flow graph.  If some branch probabilities are
         specified by __builtin_expect, then the heuristics are
         used to guess branch probabilities for the rest of the
         control flow graph, taking the __builtin_expect info
         into account.  The interactions between the heuristics
         and __builtin_expect can be complex, and in some cases,
         it may be useful to disable the heuristics so that the
         effects of __builtin_expect are easier to understand.

         The default is -fguess-branch-probability at levels -O,
         -O2, -O3, -Os.

     -freorder-blocks
         Reorder basic blocks in the compiled function in order
         to reduce number of taken branches and improve code
         locality.

         Enabled at levels -O2, -O3.

     -freorder-blocks-and-partition
         In addition to reordering basic blocks in the compiled
         function, in order to reduce number of taken branches,
         partitions hot and cold basic blocks into separate
         sections of the assembly and .o files, to improve paging
         and cache locality performance.

         This optimization is automatically turned off in the
         presence of exception handling, for linkonce sections,
         for functions with a user-defined section attribute and
         on any architecture that does not support named
         sections.

     -freorder-functions
         Reorder functions in the object file in order to improve
         code locality.  This is implemented by using special
         subsections ".text.hot" for most frequently executed
         functions and ".text.unlikely" for unlikely executed
         functions.  Reordering is done by the linker so object
         file format must support named sections and linker must
         place them in a reasonable way.

         Also profile feedback must be available to make this
         option effective.  See -fprofile-arcs for details.

         Enabled at levels -O2, -O3, -Os.

     -fstrict-aliasing
         Allow the compiler to assume the strictest aliasing
         rules applicable to the language being compiled.  For C
         (and C++), this activates optimizations based on the
         type of expressions.  In particular, an object of one
         type is assumed never to reside at the same address as
         an object of a different type, unless the types are
         almost the same.  For example, an "unsigned int" can
         alias an "int", but not a "void*" or a "double".  A
         character type may alias any other type.

         Pay special attention to code like this:

                 union a_union {
                   int i;
                   double d;
                 };

                 int f() {
                   union a_union t;
                   t.d = 3.0;
                   return t.i;
                 }

         The practice of reading from a different union member
         than the one most recently written to (called "type-
         punning") is common.  Even with -fstrict-aliasing,
         type-punning is allowed, provided the memory is accessed
         through the union type.  So, the code above works as
         expected.    However, this code might not:

                 int f() {
                   union a_union t;
                   int* ip;
                   t.d = 3.0;
                   ip = &t.i;
                   return *ip;
                 }

         Similarly, access by taking the address, casting the
         resulting pointer and dereferencing the result has
         undefined behavior, even if the cast uses a union type,
         e.g.:

                 int f() {
                   double d = 3.0;
                   return ((union a_union *) &d)->i;
                 }

         The -fstrict-aliasing option is enabled at levels -O2,
         -O3, -Os.

     -fstrict-overflow
         Allow the compiler to assume strict signed overflow
         rules, depending on the language being compiled.  For C
         (and C++) this means that overflow when doing arithmetic
         with signed numbers is undefined, which means that the
         compiler may assume that it does not happen.  This
         permits various optimizations.  For example, the
         compiler assumes that an expression like "i + 10 > i" is
         always true for signed "i".  This assumption is only
         valid if signed overflow is undefined, as the expression
         is false if "i + 10" overflows when using twos
         complement arithmetic.  When this option is in effect
         any attempt to determine whether an operation on signed
         numbers overflows must be written carefully to not
         actually involve overflow.

         This option also allows the compiler to assume strict
         pointer semantics: given a pointer to an object, if
         adding an offset to that pointer does not produce a
         pointer to the same object, the addition is undefined.
         This permits the compiler to conclude that "p + u > p"
         is always true for a pointer "p" and unsigned integer
         "u".  This assumption is only valid because pointer
         wraparound is undefined, as the expression is false if
         "p + u" overflows using twos complement arithmetic.

         See also the -fwrapv option.  Using -fwrapv means that
         integer signed overflow is fully defined: it wraps.
         When -fwrapv is used, there is no difference between
         -fstrict-overflow and -fno-strict-overflow for integers.
         With -fwrapv certain types of overflow are permitted.
         For example, if the compiler gets an overflow when doing
         arithmetic on constants, the overflowed value can still
         be used with -fwrapv, but not otherwise.

         The -fstrict-overflow option is enabled at levels -O2,
         -O3, -Os.

     -falign-functions
     -falign-functions=n
         Align the start of functions to the next power-of-two
         greater than n, skipping up to n bytes.  For instance,
         -falign-functions=32 aligns functions to the next
         32-byte boundary, but -falign-functions=24 aligns to the
         next 32-byte boundary only if this can be done by
         skipping 23 bytes or less.

         -fno-align-functions and -falign-functions=1 are
         equivalent and mean that functions are not aligned.

         Some assemblers only support this flag when n is a power
         of two; in that case, it is rounded up.

         If n is not specified or is zero, use a machine-
         dependent default.

         Enabled at levels -O2, -O3.

     -falign-labels
     -falign-labels=n
         Align all branch targets to a power-of-two boundary,
         skipping up to n bytes like -falign-functions.  This
         option can easily make code slower, because it must
         insert dummy operations for when the branch target is
         reached in the usual flow of the code.

         -fno-align-labels and -falign-labels=1 are equivalent
         and mean that labels are not aligned.

         If -falign-loops or -falign-jumps are applicable and are
         greater than this value, then their values are used
         instead.

         If n is not specified or is zero, use a machine-
         dependent default which is very likely to be 1, meaning
         no alignment.

         Enabled at levels -O2, -O3.

     -falign-loops
     -falign-loops=n

         Align loops to a power-of-two boundary, skipping up to n
         bytes like -falign-functions.  If the loops are executed
         many times, this makes up for any execution of the dummy
         operations.

         -fno-align-loops and -falign-loops=1 are equivalent and
         mean that loops are not aligned.

         If n is not specified or is zero, use a machine-
         dependent default.

         Enabled at levels -O2, -O3.

     -falign-jumps
     -falign-jumps=n
         Align branch targets to a power-of-two boundary, for
         branch targets where the targets can only be reached by
         jumping, skipping up to n bytes like -falign-functions.
         In this case, no dummy operations need be executed.

         -fno-align-jumps and -falign-jumps=1 are equivalent and
         mean that loops are not aligned.

         If n is not specified or is zero, use a machine-
         dependent default.

         Enabled at levels -O2, -O3.

     -funit-at-a-time
         This option is left for compatibility reasons.
         -funit-at-a-time has no effect, while
         -fno-unit-at-a-time implies -fno-toplevel-reorder and
         -fno-section-anchors.

         Enabled by default.

     -fno-toplevel-reorder
         Do not reorder top-level functions, variables, and "asm"
         statements.  Output them in the same order that they
         appear in the input file.  When this option is used,
         unreferenced static variables are not removed.  This
         option is intended to support existing code that relies
         on a particular ordering.  For new code, it is better to
         use attributes.

         Enabled at level -O0.  When disabled explicitly, it also
         implies -fno-section-anchors, which is otherwise enabled
         at -O0 on some targets.

     -fweb
         Constructs webs as commonly used for register allocation
         purposes and assign each web individual pseudo register.

         This allows the register allocation pass to operate on
         pseudos directly, but also strengthens several other
         optimization passes, such as CSE, loop optimizer and
         trivial dead code remover.  It can, however, make
         debugging impossible, since variables no longer stay in
         a "home register".

         Enabled by default with -funroll-loops.

     -fwhole-program
         Assume that the current compilation unit represents the
         whole program being compiled.  All public functions and
         variables with the exception of "main" and those merged
         by attribute "externally_visible" become static
         functions and in effect are optimized more aggressively
         by interprocedural optimizers.

         This option should not be used in combination with
         "-flto".  Instead relying on a linker plugin should
         provide safer and more precise information.

     -flto[=n]
         This option runs the standard link-time optimizer.  When
         invoked with source code, it generates GIMPLE (one of
         GCC's internal representations) and writes it to special
         ELF sections in the object file.  When the object files
         are linked together, all the function bodies are read
         from these ELF sections and instantiated as if they had
         been part of the same translation unit.

         To use the link-time optimizer, -flto needs to be
         specified at compile time and during the final link.
         For example:

                 gcc -c -O2 -flto foo.c
                 gcc -c -O2 -flto bar.c
                 gcc -o myprog -flto -O2 foo.o bar.o

         The first two invocations to GCC save a bytecode
         representation of GIMPLE into special ELF sections
         inside foo.o and bar.o.  The final invocation reads the
         GIMPLE bytecode from foo.o and bar.o, merges the two
         files into a single internal image, and compiles the
         result as usual.  Since both foo.o and bar.o are merged
         into a single image, this causes all the interprocedural
         analyses and optimizations in GCC to work across the two
         files as if they were a single one.  This means, for
         example, that the inliner is able to inline functions in
         bar.o into functions in foo.o and vice-versa.

         Another (simpler) way to enable link-time optimization
         is:

                 gcc -o myprog -flto -O2 foo.c bar.c

         The above generates bytecode for foo.c and bar.c, merges
         them together into a single GIMPLE representation and
         optimizes them as usual to produce myprog.

         The only important thing to keep in mind is that to
         enable link-time optimizations the -flto flag needs to
         be passed to both the compile and the link commands.

         To make whole program optimization effective, it is
         necessary to make certain whole program assumptions.
         The compiler needs to know what functions and variables
         can be accessed by libraries and runtime outside of the
         link-time optimized unit.  When supported by the linker,
         the linker plugin (see -fuse-linker-plugin) passes
         information to the compiler about used and externally
         visible symbols.  When the linker plugin is not
         available, -fwhole-program should be used to allow the
         compiler to make these assumptions, which leads to more
         aggressive optimization decisions.

         Note that when a file is compiled with -flto, the
         generated object file is larger than a regular object
         file because it contains GIMPLE bytecodes and the usual
         final code.  This means that object files with LTO
         information can be linked as normal object files; if
         -flto is not passed to the linker, no interprocedural
         optimizations are applied.

         Additionally, the optimization flags used to compile
         individual files are not necessarily related to those
         used at link time.  For instance,

                 gcc -c -O0 -flto foo.c
                 gcc -c -O0 -flto bar.c
                 gcc -o myprog -flto -O3 foo.o bar.o

         This produces individual object files with unoptimized
         assembler code, but the resulting binary myprog is
         optimized at -O3.  If, instead, the final binary is
         generated without -flto, then myprog is not optimized.

         When producing the final binary with -flto, GCC only
         applies link-time optimizations to those files that
         contain bytecode.  Therefore, you can mix and match
         object files and libraries with GIMPLE bytecodes and
         final object code.  GCC automatically selects which
         files to optimize in LTO mode and which files to link
         without further processing.

         There are some code generation flags preserved by GCC
         when generating bytecodes, as they need to be used
         during the final link stage.  Currently, the following
         options are saved into the GIMPLE bytecode files: -fPIC,
         -fcommon and all the -m target flags.

         At link time, these options are read in and reapplied.
         Note that the current implementation makes no attempt to
         recognize conflicting values for these options.  If
         different files have conflicting option values (e.g.,
         one file is compiled with -fPIC and another isn't), the
         compiler simply uses the last value read from the
         bytecode files.  It is recommended, then, that you
         compile all the files participating in the same link
         with the same options.

         If LTO encounters objects with C linkage declared with
         incompatible types in separate translation units to be
         linked together (undefined behavior according to ISO C99
         6.2.7), a non-fatal diagnostic may be issued.  The
         behavior is still undefined at run time.

         Another feature of LTO is that it is possible to apply
         interprocedural optimizations on files written in
         different languages.  This requires support in the
         language front end.  Currently, the C, C++ and Fortran
         front ends are capable of emitting GIMPLE bytecodes, so
         something like this should work:

                 gcc -c -flto foo.c
                 g++ -c -flto bar.cc
                 gfortran -c -flto baz.f90
                 g++ -o myprog -flto -O3 foo.o bar.o baz.o -lgfortran

         Notice that the final link is done with g++ to get the
         C++ runtime libraries and -lgfortran is added to get the
         Fortran runtime libraries.  In general, when mixing
         languages in LTO mode, you should use the same link
         command options as when mixing languages in a regular
         (non-LTO) compilation; all you need to add is -flto to
         all the compile and link commands.

         If object files containing GIMPLE bytecode are stored in
         a library archive, say libfoo.a, it is possible to
         extract and use them in an LTO link if you are using a
         linker with plugin support.  To enable this feature, use
         the flag -fuse-linker-plugin at link time:

                 gcc -o myprog -O2 -flto -fuse-linker-plugin a.o b.o -lfoo

         With the linker plugin enabled, the linker extracts the
         needed GIMPLE files from libfoo.a and passes them on to
         the running GCC to make them part of the aggregated

         GIMPLE image to be optimized.

         If you are not using a linker with plugin support and/or
         do not enable the linker plugin, then the objects inside
         libfoo.a are extracted and linked as usual, but they do
         not participate in the LTO optimization process.

         Link-time optimizations do not require the presence of
         the whole program to operate.  If the program does not
         require any symbols to be exported, it is possible to
         combine -flto and -fwhole-program to allow the
         interprocedural optimizers to use more aggressive
         assumptions which may lead to improved optimization
         opportunities.  Use of -fwhole-program is not needed
         when linker plugin is active (see -fuse-linker-plugin).

         The current implementation of LTO makes no attempt to
         generate bytecode that is portable between different
         types of hosts.  The bytecode files are versioned and
         there is a strict version check, so bytecode files
         generated in one version of GCC will not work with an
         older/newer version of GCC.

         Link-time optimization does not work well with
         generation of debugging information.  Combining -flto
         with -g is currently experimental and expected to
         produce wrong results.

         If you specify the optional n, the optimization and code
         generation done at link time is executed in parallel
         using n parallel jobs by utilizing an installed make
         program.  The environment variable MAKE may be used to
         override the program used.  The default value for n is
         1.

         You can also specify -flto=jobserver to use GNU make's
         job server mode to determine the number of parallel
         jobs. This is useful when the Makefile calling GCC is
         already executing in parallel.  You must prepend a + to
         the command recipe in the parent Makefile for this to
         work.  This option likely only works if MAKE is GNU
         make.

         This option is disabled by default.

     -flto-partition=alg
         Specify the partitioning algorithm used by the link-time
         optimizer.  The value is either "1to1" to specify a
         partitioning mirroring the original source files or
         "balanced" to specify partitioning into equally sized
         chunks (whenever possible) or "max" to create new
         partition for every symbol where possible.  Specifying
         "none" as an algorithm disables partitioning and
         streaming completely. The default value is "balanced".
         While "1to1" can be used as an workaround for various
         code ordering issues, the "max" partitioning is intended
         for internal testing only.

     -flto-compression-level=n
         This option specifies the level of compression used for
         intermediate language written to LTO object files, and
         is only meaningful in conjunction with LTO mode (-flto).
         Valid values are 0 (no compression) to 9 (maximum
         compression).  Values outside this range are clamped to
         either 0 or 9.  If the option is not given, a default
         balanced compression setting is used.

     -flto-report
         Prints a report with internal details on the workings of
         the link-time optimizer.  The contents of this report
         vary from version to version.  It is meant to be useful
         to GCC developers when processing object files in LTO
         mode (via -flto).

         Disabled by default.

     -fuse-linker-plugin
         Enables the use of a linker plugin during link-time
         optimization.  This option relies on plugin support in
         the linker, which is available in gold or in GNU ld 2.21
         or newer.

         This option enables the extraction of object files with
         GIMPLE bytecode out of library archives. This improves
         the quality of optimization by exposing more code to the
         link-time optimizer.  This information specifies what
         symbols can be accessed externally (by non-LTO object or
         during dynamic linking).  Resulting code quality
         improvements on binaries (and shared libraries that use
         hidden visibility) are similar to "-fwhole-program".
         See -flto for a description of the effect of this flag
         and how to use it.

         This option is enabled by default when LTO support in
         GCC is enabled and GCC was configured for use with a
         linker supporting plugins (GNU ld 2.21 or newer or
         gold).

     -ffat-lto-objects
         Fat LTO objects are object files that contain both the
         intermediate language and the object code. This makes
         them usable for both LTO linking and normal linking.
         This option is effective only when compiling with -flto
         and is ignored at link time.
         -fno-fat-lto-objects improves compilation time over
         plain LTO, but requires the complete toolchain to be
         aware of LTO. It requires a linker with linker plugin
         support for basic functionality.  Additionally, nm, ar
         and ranlib need to support linker plugins to allow a
         full-featured build environment (capable of building
         static libraries etc).  GCC provides the gcc-ar, gcc-nm,
         gcc-ranlib wrappers to pass the right options to these
         tools. With non fat LTO makefiles need to be modified to
         use them.

         The default is -ffat-lto-objects but this default is
         intended to change in future releases when linker plugin
         enabled environments become more common.

     -fcompare-elim
         After register allocation and post-register allocation
         instruction splitting, identify arithmetic instructions
         that compute processor flags similar to a comparison
         operation based on that arithmetic.  If possible,
         eliminate the explicit comparison operation.

         This pass only applies to certain targets that cannot
         explicitly represent the comparison operation before
         register allocation is complete.

         Enabled at levels -O, -O2, -O3, -Os.

     -fuse-ld=bfd
         Use the bfd linker instead of the default linker.

     -fuse-ld=gold
         Use the gold linker instead of the default linker.

     -fcprop-registers
         After register allocation and post-register allocation
         instruction splitting, perform a copy-propagation pass
         to try to reduce scheduling dependencies and
         occasionally eliminate the copy.

         Enabled at levels -O, -O2, -O3, -Os.

     -fprofile-correction
         Profiles collected using an instrumented binary for
         multi-threaded programs may be inconsistent due to
         missed counter updates. When this option is specified,
         GCC uses heuristics to correct or smooth out such
         inconsistencies. By default, GCC emits an error message
         when an inconsistent profile is detected.

     -fprofile-dir=path
         Set the directory to search for the profile data files
         in to path.  This option affects only the profile data
         generated by -fprofile-generate, -ftest-coverage,
         -fprofile-arcs and used by -fprofile-use and
         -fbranch-probabilities and its related options.  Both
         absolute and relative paths can be used.  By default,
         GCC uses the current directory as path, thus the profile
         data file appears in the same directory as the object
         file.

     -fprofile-generate
     -fprofile-generate=path
         Enable options usually used for instrumenting
         application to produce profile useful for later
         recompilation with profile feedback based optimization.
         You must use -fprofile-generate both when compiling and
         when linking your program.

         The following options are enabled: "-fprofile-arcs",
         "-fprofile-values", "-fvpt".

         If path is specified, GCC looks at the path to find the
         profile feedback data files. See -fprofile-dir.

     -fprofile-use
     -fprofile-use=path
         Enable profile feedback directed optimizations, and
         optimizations generally profitable only with profile
         feedback available.

         The following options are enabled:
         "-fbranch-probabilities", "-fvpt", "-funroll-loops",
         "-fpeel-loops", "-ftracer", "-ftree-vectorize",
         "ftree-loop-distribute-patterns"

         By default, GCC emits an error message if the feedback
         profiles do not match the source code.  This error can
         be turned into a warning by using -Wcoverage-mismatch.
         Note this may result in poorly optimized code.

         If path is specified, GCC looks at the path to find the
         profile feedback data files. See -fprofile-dir.

     The following options control compiler behavior regarding
     floating-point arithmetic.  These options trade off between
     speed and correctness.  All must be specifically enabled.

     -ffloat-store
         Do not store floating-point variables in registers, and
         inhibit other options that might change whether a
         floating-point value is taken from a register or memory.

         This option prevents undesirable excess precision on
         machines such as the 68000 where the floating registers
         (of the 68881) keep more precision than a "double" is
         supposed to have.  Similarly for the x86 architecture.
         For most programs, the excess precision does only good,
         but a few programs rely on the precise definition of
         IEEE floating point.  Use -ffloat-store for such
         programs, after modifying them to store all pertinent
         intermediate computations into variables.

     -fexcess-precision=style
         This option allows further control over excess precision
         on machines where floating-point registers have more
         precision than the IEEE "float" and "double" types and
         the processor does not support operations rounding to
         those types.  By default, -fexcess-precision=fast is in
         effect; this means that operations are carried out in
         the precision of the registers and that it is
         unpredictable when rounding to the types specified in
         the source code takes place.  When compiling C, if
         -fexcess-precision=standard is specified then excess
         precision follows the rules specified in ISO C99; in
         particular, both casts and assignments cause values to
         be rounded to their semantic types (whereas
         -ffloat-store only affects assignments).  This option is
         enabled by default for C if a strict conformance option
         such as -std=c99 is used.

         -fexcess-precision=standard is not implemented for
         languages other than C, and has no effect if
         -funsafe-math-optimizations or -ffast-math is specified.
         On the x86, it also has no effect if -mfpmath=sse or
         -mfpmath=sse+387 is specified; in the former case, IEEE
         semantics apply without excess precision, and in the
         latter, rounding is unpredictable.

     -ffast-math
         Sets -fno-math-errno, -funsafe-math-optimizations,
         -ffinite-math-only, -fno-rounding-math,
         -fno-signaling-nans and -fcx-limited-range.

         This option causes the preprocessor macro
         "__FAST_MATH__" to be defined.

         This option is not turned on by any -O option besides
         -Ofast since it can result in incorrect output for
         programs that depend on an exact implementation of IEEE
         or ISO rules/specifications for math functions. It may,
         however, yield faster code for programs that do not
         require the guarantees of these specifications.

     -fno-math-errno
         Do not set "errno" after calling math functions that are
         executed with a single instruction, e.g., "sqrt".  A
         program that relies on IEEE exceptions for math error
         handling may want to use this flag for speed while
         maintaining IEEE arithmetic compatibility.

         This option is not turned on by any -O option since it
         can result in incorrect output for programs that depend
         on an exact implementation of IEEE or ISO
         rules/specifications for math functions. It may,
         however, yield faster code for programs that do not
         require the guarantees of these specifications.

         The default is -fmath-errno.

         On Darwin systems, the math library never sets "errno".
         There is therefore no reason for the compiler to
         consider the possibility that it might, and
         -fno-math-errno is the default.

     -funsafe-math-optimizations
         Allow optimizations for floating-point arithmetic that
         (a) assume that arguments and results are valid and (b)
         may violate IEEE or ANSI standards.  When used at link-
         time, it may include libraries or startup files that
         change the default FPU control word or other similar
         optimizations.

         This option is not turned on by any -O option since it
         can result in incorrect output for programs that depend
         on an exact implementation of IEEE or ISO
         rules/specifications for math functions. It may,
         however, yield faster code for programs that do not
         require the guarantees of these specifications.  Enables
         -fno-signed-zeros, -fno-trapping-math,
         -fassociative-math and -freciprocal-math.

         The default is -fno-unsafe-math-optimizations.

     -fassociative-math
         Allow re-association of operands in series of floating-
         point operations.  This violates the ISO C and C++
         language standard by possibly changing computation
         result.  NOTE: re-ordering may change the sign of zero
         as well as ignore NaNs and inhibit or create underflow
         or overflow (and thus cannot be used on code that relies
         on rounding behavior like "(x + 2**52) - 2**52".  May
         also reorder floating-point comparisons and thus may not
         be used when ordered comparisons are required.  This
         option requires that both -fno-signed-zeros and
         -fno-trapping-math be in effect.  Moreover, it doesn't
         make much sense with -frounding-math. For Fortran the
         option is automatically enabled when both
         -fno-signed-zeros and -fno-trapping-math are in effect.

         The default is -fno-associative-math.

     -freciprocal-math
         Allow the reciprocal of a value to be used instead of
         dividing by the value if this enables optimizations.
         For example "x / y" can be replaced with "x * (1/y)",
         which is useful if "(1/y)" is subject to common
         subexpression elimination.  Note that this loses
         precision and increases the number of flops operating on
         the value.

         The default is -fno-reciprocal-math.

     -ffinite-math-only
         Allow optimizations for floating-point arithmetic that
         assume that arguments and results are not NaNs or
         +-Infs.

         This option is not turned on by any -O option since it
         can result in incorrect output for programs that depend
         on an exact implementation of IEEE or ISO
         rules/specifications for math functions. It may,
         however, yield faster code for programs that do not
         require the guarantees of these specifications.

         The default is -fno-finite-math-only.

     -fno-signed-zeros
         Allow optimizations for floating-point arithmetic that
         ignore the signedness of zero.  IEEE arithmetic
         specifies the behavior of distinct +0.0 and -0.0 values,
         which then prohibits simplification of expressions such
         as x+0.0 or 0.0*x (even with -ffinite-math-only).  This
         option implies that the sign of a zero result isn't
         significant.

         The default is -fsigned-zeros.

     -fno-trapping-math
         Compile code assuming that floating-point operations
         cannot generate user-visible traps.  These traps include
         division by zero, overflow, underflow, inexact result
         and invalid operation.  This option requires that
         -fno-signaling-nans be in effect.  Setting this option
         may allow faster code if one relies on "non-stop" IEEE
         arithmetic, for example.

         This option should never be turned on by any -O option
         since it can result in incorrect output for programs
         that depend on an exact implementation of IEEE or ISO
         rules/specifications for math functions.

         The default is -ftrapping-math.

     -frounding-math
         Disable transformations and optimizations that assume
         default floating-point rounding behavior.  This is
         round-to-zero for all floating point to integer
         conversions, and round-to-nearest for all other
         arithmetic truncations.  This option should be specified
         for programs that change the FP rounding mode
         dynamically, or that may be executed with a non-default
         rounding mode.  This option disables constant folding of
         floating-point expressions at compile time (which may be
         affected by rounding mode) and arithmetic
         transformations that are unsafe in the presence of
         sign-dependent rounding modes.

         The default is -fno-rounding-math.

         This option is experimental and does not currently
         guarantee to disable all GCC optimizations that are
         affected by rounding mode.  Future versions of GCC may
         provide finer control of this setting using C99's
         "FENV_ACCESS" pragma.  This command-line option will be
         used to specify the default state for "FENV_ACCESS".

     -fsignaling-nans
         Compile code assuming that IEEE signaling NaNs may
         generate user-visible traps during floating-point
         operations.  Setting this option disables optimizations
         that may change the number of exceptions visible with
         signaling NaNs.  This option implies -ftrapping-math.

         This option causes the preprocessor macro
         "__SUPPORT_SNAN__" to be defined.

         The default is -fno-signaling-nans.

         This option is experimental and does not currently
         guarantee to disable all GCC optimizations that affect
         signaling NaN behavior.

     -fsingle-precision-constant
         Treat floating-point constants as single precision
         instead of implicitly converting them to double-
         precision constants.

     -fcx-limited-range
         When enabled, this option states that a range reduction
         step is not needed when performing complex division.
         Also, there is no checking whether the result of a
         complex multiplication or division is "NaN + I*NaN",
         with an attempt to rescue the situation in that case.
         The default is -fno-cx-limited-range, but is enabled by
         -ffast-math.

         This option controls the default setting of the ISO C99
         "CX_LIMITED_RANGE" pragma.  Nevertheless, the option
         applies to all languages.

     -fcx-fortran-rules
         Complex multiplication and division follow Fortran
         rules.  Range reduction is done as part of complex
         division, but there is no checking whether the result of
         a complex multiplication or division is "NaN + I*NaN",
         with an attempt to rescue the situation in that case.

         The default is -fno-cx-fortran-rules.

     The following options control optimizations that may improve
     performance, but are not enabled by any -O options.  This
     section includes experimental options that may produce
     broken code.

     -fbranch-probabilities
         After running a program compiled with -fprofile-arcs,
         you can compile it a second time using
         -fbranch-probabilities, to improve optimizations based
         on the number of times each branch was taken.  When a
         program compiled with -fprofile-arcs exits, it saves arc
         execution counts to a file called sourcename.gcda for
         each source file.  The information in this data file is
         very dependent on the structure of the generated code,
         so you must use the same source code and the same
         optimization options for both compilations.

         With -fbranch-probabilities, GCC puts a REG_BR_PROB note
         on each JUMP_INSN and CALL_INSN.  These can be used to
         improve optimization.  Currently, they are only used in
         one place: in reorg.c, instead of guessing which path a
         branch is most likely to take, the REG_BR_PROB values
         are used to exactly determine which path is taken more
         often.

     -fprofile-values
         If combined with -fprofile-arcs, it adds code so that
         some data about values of expressions in the program is
         gathered.

         With -fbranch-probabilities, it reads back the data
         gathered from profiling values of expressions for usage
         in optimizations.

         Enabled with -fprofile-generate and -fprofile-use.

     -fvpt
         If combined with -fprofile-arcs, this option instructs
         the compiler to add code to gather information about
         values of expressions.

         With -fbranch-probabilities, it reads back the data
         gathered and actually performs the optimizations based
         on them.  Currently the optimizations include
         specialization of division operations using the
         knowledge about the value of the denominator.

     -frename-registers
         Attempt to avoid false dependencies in scheduled code by
         making use of registers left over after register
         allocation.  This optimization most benefits processors
         with lots of registers.  Depending on the debug
         information format adopted by the target, however, it
         can make debugging impossible, since variables no longer
         stay in a "home register".

         Enabled by default with -funroll-loops and -fpeel-loops.

     -ftracer
         Perform tail duplication to enlarge superblock size.
         This transformation simplifies the control flow of the
         function allowing other optimizations to do a better
         job.

         Enabled with -fprofile-use.

     -funroll-loops
         Unroll loops whose number of iterations can be
         determined at compile time or upon entry to the loop.
         -funroll-loops implies -frerun-cse-after-loop, -fweb and
         -frename-registers.  It also turns on complete loop
         peeling (i.e. complete removal of loops with a small
         constant number of iterations).  This option makes code
         larger, and may or may not make it run faster.

         Enabled with -fprofile-use.

     -funroll-all-loops
         Unroll all loops, even if their number of iterations is
         uncertain when the loop is entered.  This usually makes
         programs run more slowly.  -funroll-all-loops implies
         the same options as -funroll-loops.

     -fpeel-loops
         Peels loops for which there is enough information that
         they do not roll much (from profile feedback).  It also
         turns on complete loop peeling (i.e. complete removal of
         loops with small constant number of iterations).

         Enabled with -fprofile-use.

     -fmove-loop-invariants
         Enables the loop invariant motion pass in the RTL loop
         optimizer.  Enabled at level -O1

     -funswitch-loops
         Move branches with loop invariant conditions out of the
         loop, with duplicates of the loop on both branches
         (modified according to result of the condition).

     -ffunction-sections
     -fdata-sections
         Place each function or data item into its own section in
         the output file if the target supports arbitrary
         sections.  The name of the function or the name of the
         data item determines the section's name in the output
         file.

         Use these options on systems where the linker can
         perform optimizations to improve locality of reference
         in the instruction space.  Most systems using the ELF
         object format and SPARC processors running Solaris 2
         have linkers with such optimizations.  AIX may have
         these optimizations in the future.

         Only use these options when there are significant
         benefits from doing so.  When you specify these options,
         the assembler and linker create larger object and
         executable files and are also slower.  You cannot use
         "gprof" on all systems if you specify this option, and
         you may have problems with debugging if you specify both
         this option and -g.

     -fbranch-target-load-optimize
         Perform branch target register load optimization before
         prologue / epilogue threading.  The use of target
         registers can typically be exposed only during reload,
         thus hoisting loads out of loops and doing inter-block
         scheduling needs a separate optimization pass.

     -fbranch-target-load-optimize2
         Perform branch target register load optimization after
         prologue / epilogue threading.

     -fbtr-bb-exclusive
         When performing branch target register load
         optimization, don't reuse branch target registers within
         any basic block.

     -fstack-protector
         Emit extra code to check for buffer overflows, such as
         stack smashing attacks.  This is done by adding a guard
         variable to functions with vulnerable objects.  This
         includes functions that call "alloca", and functions
         with buffers larger than 8 bytes.  The guards are
         initialized when a function is entered and then checked
         when the function exits.  If a guard check fails, an
         error message is printed and the program exits.

     -fstack-protector-all
         Like -fstack-protector except that all functions are
         protected.

     -fsection-anchors
         Try to reduce the number of symbolic address
         calculations by using shared "anchor" symbols to address
         nearby objects.  This transformation can help to reduce
         the number of GOT entries and GOT accesses on some
         targets.

         For example, the implementation of the following
         function "foo":

                 static int a, b, c;
                 int foo (void) { return a + b + c; }

         usually calculates the addresses of all three variables,
         but if you compile it with -fsection-anchors, it
         accesses the variables from a common anchor point
         instead.  The effect is similar to the following
         pseudocode (which isn't valid C):

                 int foo (void)
                 {
                   register int *xr = &x;
                   return xr[&a - &x] + xr[&b - &x] + xr[&c - &x];
                 }

         Not all targets support this option.

     --param name=value
         In some places, GCC uses various constants to control
         the amount of optimization that is done.  For example,
         GCC does not inline functions that contain more than a
         certain number of instructions.  You can control some of
         these constants on the command line using the --param
         option.

         The names of specific parameters, and the meaning of the
         values, are tied to the internals of the compiler, and
         are subject to change without notice in future releases.

         In each case, the value is an integer.  The allowable
         choices for name are:

         predictable-branch-outcome
             When branch is predicted to be taken with
             probability lower than this threshold (in percent),
             then it is considered well predictable. The default
             is 10.

         max-crossjump-edges
             The maximum number of incoming edges to consider for
             cross-jumping.  The algorithm used by -fcrossjumping
             is O(N^2) in the number of edges incoming to each
             block.  Increasing values mean more aggressive
             optimization, making the compilation time increase
             with probably small improvement in executable size.

         min-crossjump-insns
             The minimum number of instructions that must be
             matched at the end of two blocks before cross-
             jumping is performed on them.  This value is ignored
             in the case where all instructions in the block
             being cross-jumped from are matched.  The default
             value is 5.

         max-grow-copy-bb-insns
             The maximum code size expansion factor when copying
             basic blocks instead of jumping.  The expansion is
             relative to a jump instruction.  The default value
             is 8.

         max-goto-duplication-insns
             The maximum number of instructions to duplicate to a
             block that jumps to a computed goto.  To avoid
             O(N^2) behavior in a number of passes, GCC factors
             computed gotos early in the compilation process, and
             unfactors them as late as possible.  Only computed
             jumps at the end of a basic blocks with no more than
             max-goto-duplication-insns are unfactored.  The
             default value is 8.

         max-delay-slot-insn-search
             The maximum number of instructions to consider when
             looking for an instruction to fill a delay slot.  If
             more than this arbitrary number of instructions are
             searched, the time savings from filling the delay
             slot are minimal, so stop searching.  Increasing
             values mean more aggressive optimization, making the
             compilation time increase with probably small
             improvement in execution time.

         max-delay-slot-live-search

             When trying to fill delay slots, the maximum number
             of instructions to consider when searching for a
             block with valid live register information.
             Increasing this arbitrarily chosen value means more
             aggressive optimization, increasing the compilation
             time.  This parameter should be removed when the
             delay slot code is rewritten to maintain the
             control-flow graph.

         max-gcse-memory
             The approximate maximum amount of memory that can be
             allocated in order to perform the global common
             subexpression elimination optimization.  If more
             memory than specified is required, the optimization
             is not done.

         max-gcse-insertion-ratio
             If the ratio of expression insertions to deletions
             is larger than this value for any expression, then
             RTL PRE inserts or removes the expression and thus
             leaves partially redundant computations in the
             instruction stream.  The default value is 20.

         max-pending-list-length
             The maximum number of pending dependencies
             scheduling allows before flushing the current state
             and starting over.  Large functions with few
             branches or calls can create excessively large lists
             which needlessly consume memory and resources.

         max-modulo-backtrack-attempts
             The maximum number of backtrack attempts the
             scheduler should make when modulo scheduling a loop.
             Larger values can exponentially increase compilation
             time.

         max-inline-insns-single
             Several parameters control the tree inliner used in
             GCC.  This number sets the maximum number of
             instructions (counted in GCC's internal
             representation) in a single function that the tree
             inliner considers for inlining.  This only affects
             functions declared inline and methods implemented in
             a class declaration (C++).  The default value is
             400.

         max-inline-insns-auto
             When you use -finline-functions (included in -O3), a
             lot of functions that would otherwise not be
             considered for inlining by the compiler are
             investigated.  To those functions, a different (more
             restrictive) limit compared to functions declared
             inline can be applied.  The default value is 40.

         inline-min-speedup
             When estimated performance improvement of caller +
             callee runtime exceeds this threshold (in precent),
             the function can be inlined regardless the limit on
             --param max-inline-insns-single and --param max-
             inline-insns-auto.

         large-function-insns
             The limit specifying really large functions.  For
             functions larger than this limit after inlining,
             inlining is constrained by --param large-function-
             growth.  This parameter is useful primarily to avoid
             extreme compilation time caused by non-linear
             algorithms used by the back end.  The default value
             is 2700.

         large-function-growth
             Specifies maximal growth of large function caused by
             inlining in percents.  The default value is 100
             which limits large function growth to 2.0 times the
             original size.

         large-unit-insns
             The limit specifying large translation unit.  Growth
             caused by inlining of units larger than this limit
             is limited by --param inline-unit-growth.  For small
             units this might be too tight.  For example,
             consider a unit consisting of function A that is
             inline and B that just calls A three times.  If B is
             small relative to A, the growth of unit is 300\% and
             yet such inlining is very sane.  For very large
             units consisting of small inlineable functions,
             however, the overall unit growth limit is needed to
             avoid exponential explosion of code size.  Thus for
             smaller units, the size is increased to --param
             large-unit-insns before applying --param inline-
             unit-growth.  The default is 10000.

         inline-unit-growth
             Specifies maximal overall growth of the compilation
             unit caused by inlining.  The default value is 30
             which limits unit growth to 1.3 times the original
             size.

         ipcp-unit-growth
             Specifies maximal overall growth of the compilation
             unit caused by interprocedural constant propagation.
             The default value is 10 which limits unit growth to
             1.1 times the original size.

         large-stack-frame
             The limit specifying large stack frames.  While
             inlining the algorithm is trying to not grow past
             this limit too much.  The default value is 256
             bytes.

         large-stack-frame-growth
             Specifies maximal growth of large stack frames
             caused by inlining in percents.  The default value
             is 1000 which limits large stack frame growth to 11
             times the original size.

         max-inline-insns-recursive
         max-inline-insns-recursive-auto
             Specifies the maximum number of instructions an
             out-of-line copy of a self-recursive inline function
             can grow into by performing recursive inlining.

             For functions declared inline, --param max-inline-
             insns-recursive is taken into account.  For
             functions not declared inline, recursive inlining
             happens only when -finline-functions (included in
             -O3) is enabled and --param max-inline-insns-
             recursive-auto is used.  The default value is 450.

         max-inline-recursive-depth
         max-inline-recursive-depth-auto
             Specifies the maximum recursion depth used for
             recursive inlining.

             For functions declared inline, --param max-inline-
             recursive-depth is taken into account.  For
             functions not declared inline, recursive inlining
             happens only when -finline-functions (included in
             -O3) is enabled and --param max-inline-recursive-
             depth-auto is used.  The default value is 8.

         min-inline-recursive-probability
             Recursive inlining is profitable only for function
             having deep recursion in average and can hurt for
             function having little recursion depth by increasing
             the prologue size or complexity of function body to
             other optimizers.

             When profile feedback is available (see
             -fprofile-generate) the actual recursion depth can
             be guessed from probability that function recurses
             via a given call expression.  This parameter limits
             inlining only to call expressions whose probability
             exceeds the given threshold (in percents).  The
             default value is 10.

         early-inlining-insns
             Specify growth that the early inliner can make.  In
             effect it increases the amount of inlining for code
             having a large abstraction penalty.  The default
             value is 10.

         max-early-inliner-iterations
         max-early-inliner-iterations
             Limit of iterations of the early inliner.  This
             basically bounds the number of nested indirect calls
             the early inliner can resolve.  Deeper chains are
             still handled by late inlining.

         comdat-sharing-probability
         comdat-sharing-probability
             Probability (in percent) that C++ inline function
             with comdat visibility are shared across multiple
             compilation units.  The default value is 20.

         min-vect-loop-bound
             The minimum number of iterations under which loops
             are not vectorized when -ftree-vectorize is used.
             The number of iterations after vectorization needs
             to be greater than the value specified by this
             option to allow vectorization.  The default value is
             0.

         gcse-cost-distance-ratio
             Scaling factor in calculation of maximum distance an
             expression can be moved by GCSE optimizations.  This
             is currently supported only in the code hoisting
             pass.  The bigger the ratio, the more aggressive
             code hoisting is with simple expressions, i.e., the
             expressions that have cost less than gcse-
             unrestricted-cost.  Specifying 0 disables hoisting
             of simple expressions.  The default value is 10.

         gcse-unrestricted-cost
             Cost, roughly measured as the cost of a single
             typical machine instruction, at which GCSE
             optimizations do not constrain the distance an
             expression can travel.  This is currently supported
             only in the code hoisting pass.  The lesser the
             cost, the more aggressive code hoisting is.
             Specifying 0 allows all expressions to travel
             unrestricted distances.  The default value is 3.

         max-hoist-depth
             The depth of search in the dominator tree for
             expressions to hoist.  This is used to avoid
             quadratic behavior in hoisting algorithm.  The value
             of 0 does not limit on the search, but may slow down
             compilation of huge functions.  The default value is
             30.

         max-tail-merge-comparisons
             The maximum amount of similar bbs to compare a bb
             with.  This is used to avoid quadratic behavior in
             tree tail merging.  The default value is 10.

         max-tail-merge-iterations
             The maximum amount of iterations of the pass over
             the function.  This is used to limit compilation
             time in tree tail merging.  The default value is 2.

         max-unrolled-insns
             The maximum number of instructions that a loop may
             have to be unrolled.  If a loop is unrolled, this
             parameter also determines how many times the loop
             code is unrolled.

         max-average-unrolled-insns
             The maximum number of instructions biased by
             probabilities of their execution that a loop may
             have to be unrolled.  If a loop is unrolled, this
             parameter also determines how many times the loop
             code is unrolled.

         max-unroll-times
             The maximum number of unrollings of a single loop.

         max-peeled-insns
             The maximum number of instructions that a loop may
             have to be peeled.  If a loop is peeled, this
             parameter also determines how many times the loop
             code is peeled.

         max-peel-times
             The maximum number of peelings of a single loop.

         max-peel-branches
             The maximum number of branches on the hot path
             through the peeled sequence.

         max-completely-peeled-insns
             The maximum number of insns of a completely peeled
             loop.

         max-completely-peel-times
             The maximum number of iterations of a loop to be
             suitable for complete peeling.

         max-completely-peel-loop-nest-depth
             The maximum depth of a loop nest suitable for
             complete peeling.

         max-unswitch-insns
             The maximum number of insns of an unswitched loop.

         max-unswitch-level
             The maximum number of branches unswitched in a
             single loop.

         lim-expensive
             The minimum cost of an expensive expression in the
             loop invariant motion.

         iv-consider-all-candidates-bound
             Bound on number of candidates for induction
             variables, below which all candidates are considered
             for each use in induction variable optimizations.
             If there are more candidates than this, only the
             most relevant ones are considered to avoid quadratic
             time complexity.

         iv-max-considered-uses
             The induction variable optimizations give up on
             loops that contain more induction variable uses.

         iv-always-prune-cand-set-bound
             If the number of candidates in the set is smaller
             than this value, always try to remove unnecessary
             ivs from the set when adding a new one.

         scev-max-expr-size
             Bound on size of expressions used in the scalar
             evolutions analyzer.  Large expressions slow the
             analyzer.

         scev-max-expr-complexity
             Bound on the complexity of the expressions in the
             scalar evolutions analyzer.  Complex expressions
             slow the analyzer.

         omega-max-vars
             The maximum number of variables in an Omega
             constraint system.  The default value is 128.

         omega-max-geqs
             The maximum number of inequalities in an Omega
             constraint system.  The default value is 256.

         omega-max-eqs
             The maximum number of equalities in an Omega
             constraint system.  The default value is 128.

         omega-max-wild-cards
             The maximum number of wildcard variables that the
             Omega solver is able to insert.  The default value
             is 18.

         omega-hash-table-size
             The size of the hash table in the Omega solver.  The
             default value is 550.

         omega-max-keys
             The maximal number of keys used by the Omega solver.
             The default value is 500.

         omega-eliminate-redundant-constraints
             When set to 1, use expensive methods to eliminate
             all redundant constraints.  The default value is 0.

         vect-max-version-for-alignment-checks
             The maximum number of run-time checks that can be
             performed when doing loop versioning for alignment
             in the vectorizer.  See option
             -ftree-vect-loop-version for more information.

         vect-max-version-for-alias-checks
             The maximum number of run-time checks that can be
             performed when doing loop versioning for alias in
             the vectorizer.  See option -ftree-vect-loop-version
             for more information.

         max-iterations-to-track
             The maximum number of iterations of a loop the
             brute-force algorithm for analysis of the number of
             iterations of the loop tries to evaluate.

         hot-bb-count-ws-permille
             A basic block profile count is considered hot if it
             contributes to the given permillage (i.e. 0...1000)
             of the entire profiled execution.

         hot-bb-frequency-fraction
             Select fraction of the entry block frequency of
             executions of basic block in function given basic
             block needs to have to be considered hot.

         max-predicted-iterations
             The maximum number of loop iterations we predict
             statically.  This is useful in cases where a
             function contains a single loop with known bound and
             another loop with unknown bound.  The known number
             of iterations is predicted correctly, while the
             unknown number of iterations average to roughly 10.
             This means that the loop without bounds appears
             artificially cold relative to the other one.

         align-threshold
             Select fraction of the maximal frequency of
             executions of a basic block in a function to align
             the basic block.

         align-loop-iterations
             A loop expected to iterate at least the selected
             number of iterations is aligned.

         tracer-dynamic-coverage
         tracer-dynamic-coverage-feedback
             This value is used to limit superblock formation
             once the given percentage of executed instructions
             is covered.  This limits unnecessary code size
             expansion.

             The tracer-dynamic-coverage-feedback is used only
             when profile feedback is available.  The real
             profiles (as opposed to statically estimated ones)
             are much less balanced allowing the threshold to be
             larger value.

         tracer-max-code-growth
             Stop tail duplication once code growth has reached
             given percentage.  This is a rather artificial
             limit, as most of the duplicates are eliminated
             later in cross jumping, so it may be set to much
             higher values than is the desired code growth.

         tracer-min-branch-ratio
             Stop reverse growth when the reverse probability of
             best edge is less than this threshold (in percent).

         tracer-min-branch-ratio
         tracer-min-branch-ratio-feedback
             Stop forward growth if the best edge has probability
             lower than this threshold.

             Similarly to tracer-dynamic-coverage two values are
             present, one for compilation for profile feedback
             and one for compilation without.  The value for
             compilation with profile feedback needs to be more
             conservative (higher) in order to make tracer
             effective.

         max-cse-path-length
             The maximum number of basic blocks on path that CSE
             considers.  The default is 10.

         max-cse-insns

             The maximum number of instructions CSE processes
             before flushing.  The default is 1000.

         ggc-min-expand
             GCC uses a garbage collector to manage its own
             memory allocation.  This parameter specifies the
             minimum percentage by which the garbage collector's
             heap should be allowed to expand between
             collections.  Tuning this may improve compilation
             speed; it has no effect on code generation.

             The default is 30% + 70% * (RAM/1GB) with an upper
             bound of 100% when RAM >= 1GB.  If "getrlimit" is
             available, the notion of "RAM" is the smallest of
             actual RAM and "RLIMIT_DATA" or "RLIMIT_AS".  If GCC
             is not able to calculate RAM on a particular
             platform, the lower bound of 30% is used.  Setting
             this parameter and ggc-min-heapsize to zero causes a
             full collection to occur at every opportunity.  This
             is extremely slow, but can be useful for debugging.

         ggc-min-heapsize
             Minimum size of the garbage collector's heap before
             it begins bothering to collect garbage.  The first
             collection occurs after the heap expands by ggc-
             min-expand% beyond ggc-min-heapsize.  Again, tuning
             this may improve compilation speed, and has no
             effect on code generation.

             The default is the smaller of RAM/8, RLIMIT_RSS, or
             a limit that tries to ensure that RLIMIT_DATA or
             RLIMIT_AS are not exceeded, but with a lower bound
             of 4096 (four megabytes) and an upper bound of
             131072 (128 megabytes).  If GCC is not able to
             calculate RAM on a particular platform, the lower
             bound is used.  Setting this parameter very large
             effectively disables garbage collection.  Setting
             this parameter and ggc-min-expand to zero causes a
             full collection to occur at every opportunity.

         max-reload-search-insns
             The maximum number of instruction reload should look
             backward for equivalent register.  Increasing values
             mean more aggressive optimization, making the
             compilation time increase with probably slightly
             better performance.  The default value is 100.

         max-cselib-memory-locations
             The maximum number of memory locations cselib should
             take into account.  Increasing values mean more
             aggressive optimization, making the compilation time
             increase with probably slightly better performance.

             The default value is 500.

         reorder-blocks-duplicate
         reorder-blocks-duplicate-feedback
             Used by the basic block reordering pass to decide
             whether to use unconditional branch or duplicate the
             code on its destination.  Code is duplicated when
             its estimated size is smaller than this value
             multiplied by the estimated size of unconditional
             jump in the hot spots of the program.

             The reorder-block-duplicate-feedback is used only
             when profile feedback is available.  It may be set
             to higher values than reorder-block-duplicate since
             information about the hot spots is more accurate.

         max-sched-ready-insns
             The maximum number of instructions ready to be
             issued the scheduler should consider at any given
             time during the first scheduling pass.  Increasing
             values mean more thorough searches, making the
             compilation time increase with probably little
             benefit.  The default value is 100.

         max-sched-region-blocks
             The maximum number of blocks in a region to be
             considered for interblock scheduling.  The default
             value is 10.

         max-pipeline-region-blocks
             The maximum number of blocks in a region to be
             considered for pipelining in the selective
             scheduler.  The default value is 15.

         max-sched-region-insns
             The maximum number of insns in a region to be
             considered for interblock scheduling.  The default
             value is 100.

         max-pipeline-region-insns
             The maximum number of insns in a region to be
             considered for pipelining in the selective
             scheduler.  The default value is 200.

         min-spec-prob
             The minimum probability (in percents) of reaching a
             source block for interblock speculative scheduling.
             The default value is 40.

         max-sched-extend-regions-iters
             The maximum number of iterations through CFG to
             extend regions.  A value of 0 (the default) disables
             region extensions.

         max-sched-insn-conflict-delay
             The maximum conflict delay for an insn to be
             considered for speculative motion.  The default
             value is 3.

         sched-spec-prob-cutoff
             The minimal probability of speculation success (in
             percents), so that speculative insns are scheduled.
             The default value is 40.

         sched-spec-state-edge-prob-cutoff
             The minimum probability an edge must have for the
             scheduler to save its state across it.  The default
             value is 10.

         sched-mem-true-dep-cost
             Minimal distance (in CPU cycles) between store and
             load targeting same memory locations.  The default
             value is 1.

         selsched-max-lookahead
             The maximum size of the lookahead window of
             selective scheduling.  It is a depth of search for
             available instructions.  The default value is 50.

         selsched-max-sched-times
             The maximum number of times that an instruction is
             scheduled during selective scheduling.  This is the
             limit on the number of iterations through which the
             instruction may be pipelined.  The default value is
             2.

         selsched-max-insns-to-rename
             The maximum number of best instructions in the ready
             list that are considered for renaming in the
             selective scheduler.  The default value is 2.

         sms-min-sc
             The minimum value of stage count that swing modulo
             scheduler generates.  The default value is 2.

         max-last-value-rtl
             The maximum size measured as number of RTLs that can
             be recorded in an expression in combiner for a
             pseudo register as last known value of that
             register.  The default is 10000.

         integer-share-limit
             Small integer constants can use a shared data
             structure, reducing the compiler's memory usage and
             increasing its speed.  This sets the maximum value
             of a shared integer constant.  The default value is
             256.

         ssp-buffer-size
             The minimum size of buffers (i.e. arrays) that
             receive stack smashing protection when
             -fstack-protection is used.

         max-jump-thread-duplication-stmts
             Maximum number of statements allowed in a block that
             needs to be duplicated when threading jumps.

         max-fields-for-field-sensitive
             Maximum number of fields in a structure treated in a
             field sensitive manner during pointer analysis.  The
             default is zero for -O0 and -O1, and 100 for -Os,
             -O2, and -O3.

         prefetch-latency
             Estimate on average number of instructions that are
             executed before prefetch finishes.  The distance
             prefetched ahead is proportional to this constant.
             Increasing this number may also lead to less streams
             being prefetched (see simultaneous-prefetches).

         simultaneous-prefetches
             Maximum number of prefetches that can run at the
             same time.

         l1-cache-line-size
             The size of cache line in L1 cache, in bytes.

         l1-cache-size
             The size of L1 cache, in kilobytes.

         l2-cache-size
             The size of L2 cache, in kilobytes.

         min-insn-to-prefetch-ratio
             The minimum ratio between the number of instructions
             and the number of prefetches to enable prefetching
             in a loop.

         prefetch-min-insn-to-mem-ratio
             The minimum ratio between the number of instructions
             and the number of memory references to enable
             prefetching in a loop.

         use-canonical-types
             Whether the compiler should use the "canonical" type
             system.  By default, this should always be 1, which
             uses a more efficient internal mechanism for
             comparing types in C++ and Objective-C++.  However,
             if bugs in the canonical type system are causing
             compilation failures, set this value to 0 to disable
             canonical types.

         switch-conversion-max-branch-ratio
             Switch initialization conversion refuses to create
             arrays that are bigger than switch-conversion-max-
             branch-ratio times the number of branches in the
             switch.

         max-partial-antic-length
             Maximum length of the partial antic set computed
             during the tree partial redundancy elimination
             optimization (-ftree-pre) when optimizing at -O3 and
             above.  For some sorts of source code the enhanced
             partial redundancy elimination optimization can run
             away, consuming all of the memory available on the
             host machine.  This parameter sets a limit on the
             length of the sets that are computed, which prevents
             the runaway behavior.  Setting a value of 0 for this
             parameter allows an unlimited set length.

         sccvn-max-scc-size
             Maximum size of a strongly connected component (SCC)
             during SCCVN processing.  If this limit is hit,
             SCCVN processing for the whole function is not done
             and optimizations depending on it are disabled.  The
             default maximum SCC size is 10000.

         sccvn-max-alias-queries-per-access
             Maximum number of alias-oracle queries we perform
             when looking for redundancies for loads and stores.
             If this limit is hit the search is aborted and the
             load or store is not considered redundant.  The
             number of queries is algorithmically limited to the
             number of stores on all paths from the load to the
             function entry.  The default maxmimum number of
             queries is 1000.

         ira-max-loops-num
             IRA uses regional register allocation by default.
             If a function contains more loops than the number
             given by this parameter, only at most the given
             number of the most frequently-executed loops form
             regions for regional register allocation.  The
             default value of the parameter is 100.

         ira-max-conflict-table-size
             Although IRA uses a sophisticated algorithm to
             compress the conflict table, the table can still
             require excessive amounts of memory for huge
             functions.  If the conflict table for a function
             could be more than the size in MB given by this
             parameter, the register allocator instead uses a
             faster, simpler, and lower-quality algorithm that
             does not require building a pseudo-register conflict
             table. The default value of the parameter is 2000.

         ira-loop-reserved-regs
             IRA can be used to evaluate more accurate register
             pressure in loops for decisions to move loop
             invariants (see -O3).  The number of available
             registers reserved for some other purposes is given
             by this parameter.  The default value of the
             parameter is 2, which is the minimal number of
             registers needed by typical instructions.  This
             value is the best found from numerous experiments.

         loop-invariant-max-bbs-in-loop
             Loop invariant motion can be very expensive, both in
             compilation time and in amount of needed compile-
             time memory, with very large loops.  Loops with more
             basic blocks than this parameter won't have loop
             invariant motion optimization performed on them.
             The default value of the parameter is 1000 for -O1
             and 10000 for -O2 and above.

         loop-max-datarefs-for-datadeps
             Building data dapendencies is expensive for very
             large loops.  This parameter limits the number of
             data references in loops that are considered for
             data dependence analysis.  These large loops are no
             handled by the optimizations using loop data
             dependencies.  The default value is 1000.

         max-vartrack-size
             Sets a maximum number of hash table slots to use
             during variable tracking dataflow analysis of any
             function.  If this limit is exceeded with variable
             tracking at assignments enabled, analysis for that
             function is retried without it, after removing all
             debug insns from the function.  If the limit is
             exceeded even without debug insns, var tracking
             analysis is completely disabled for the function.
             Setting the parameter to zero makes it unlimited.

         max-vartrack-expr-depth
             Sets a maximum number of recursion levels when
             attempting to map variable names or debug
             temporaries to value expressions.  This trades
             compilation time for more complete debug
             information.  If this is set too low, value
             expressions that are available and could be
             represented in debug information may end up not
             being used; setting this higher may enable the
             compiler to find more complex debug expressions, but
             compile time and memory use may grow.  The default
             is 12.

         min-nondebug-insn-uid
             Use uids starting at this parameter for nondebug
             insns.  The range below the parameter is reserved
             exclusively for debug insns created by
             -fvar-tracking-assignments, but debug insns may get
             (non-overlapping) uids above it if the reserved
             range is exhausted.

         ipa-sra-ptr-growth-factor
             IPA-SRA replaces a pointer to an aggregate with one
             or more new parameters only when their cumulative
             size is less or equal to ipa-sra-ptr-growth-factor
             times the size of the original pointer parameter.

         tm-max-aggregate-size
             When making copies of thread-local variables in a
             transaction, this parameter specifies the size in
             bytes after which variables are saved with the
             logging functions as opposed to save/restore code
             sequence pairs.  This option only applies when using
             -fgnu-tm.

         graphite-max-nb-scop-params
             To avoid exponential effects in the Graphite loop
             transforms, the number of parameters in a Static
             Control Part (SCoP) is bounded.  The default value
             is 10 parameters.  A variable whose value is unknown
             at compilation time and defined outside a SCoP is a
             parameter of the SCoP.

         graphite-max-bbs-per-function
             To avoid exponential effects in the detection of
             SCoPs, the size of the functions analyzed by
             Graphite is bounded.  The default value is 100 basic
             blocks.

         loop-block-tile-size
             Loop blocking or strip mining transforms, enabled
             with -floop-block or -floop-strip-mine, strip mine
             each loop in the loop nest by a given number of
             iterations.  The strip length can be changed using
             the loop-block-tile-size parameter.  The default
             value is 51 iterations.

         ipa-cp-value-list-size

             IPA-CP attempts to track all possible values and
             types passed to a function's parameter in order to
             propagate them and perform devirtualization.  ipa-
             cp-value-list-size is the maximum number of values
             and types it stores per one formal parameter of a
             function.

         lto-partitions
             Specify desired number of partitions produced during
             WHOPR compilation.  The number of partitions should
             exceed the number of CPUs used for compilation.  The
             default value is 32.

         lto-minpartition
             Size of minimal partition for WHOPR (in estimated
             instructions).  This prevents expenses of splitting
             very small programs into too many partitions.

         cxx-max-namespaces-for-diagnostic-help
             The maximum number of namespaces to consult for
             suggestions when C++ name lookup fails for an
             identifier.  The default is 1000.

         sink-frequency-threshold
             The maximum relative execution frequency (in
             percents) of the target block relative to a
             statement's original block to allow statement
             sinking of a statement.  Larger numbers result in
             more aggressive statement sinking.  The default
             value is 75.  A small positive adjustment is applied
             for statements with memory operands as those are
             even more profitable so sink.

         max-stores-to-sink
             The maximum number of conditional stores paires that
             can be sunk.  Set to 0 if either vectorization
             (-ftree-vectorize) or if-conversion
             (-ftree-loop-if-convert) is disabled.  The default
             is 2.

         allow-load-data-races
             Allow optimizers to introduce new data races on
             loads.  Set to 1 to allow, otherwise to 0.  This
             option is enabled by default unless implicitly set
             by the -fmemory-model= option.

         allow-store-data-races
             Allow optimizers to introduce new data races on
             stores.  Set to 1 to allow, otherwise to 0.  This
             option is enabled by default unless implicitly set
             by the -fmemory-model= option.

         allow-packed-load-data-races
             Allow optimizers to introduce new data races on
             packed data loads.  Set to 1 to allow, otherwise to
             0.  This option is enabled by default unless
             implicitly set by the -fmemory-model= option.

         allow-packed-store-data-races
             Allow optimizers to introduce new data races on
             packed data stores.  Set to 1 to allow, otherwise to
             0.  This option is enabled by default unless
             implicitly set by the -fmemory-model= option.

         case-values-threshold
             The smallest number of different values for which it
             is best to use a jump-table instead of a tree of
             conditional branches.  If the value is 0, use the
             default for the machine.  The default is 0.

         tree-reassoc-width
             Set the maximum number of instructions executed in
             parallel in reassociated tree. This parameter
             overrides target dependent heuristics used by
             default if has non zero value.

         sched-pressure-algorithm
             Choose between the two available implementations of
             -fsched-pressure.  Algorithm 1 is the original
             implementation and is the more likely to prevent
             instructions from being reordered.  Algorithm 2 was
             designed to be a compromise between the relatively
             conservative approach taken by algorithm 1 and the
             rather aggressive approach taken by the default
             scheduler.  It relies more heavily on having a
             regular register file and accurate register pressure
             classes.  See haifa-sched.c in the GCC sources for
             more details.

             The default choice depends on the target.

         max-slsr-cand-scan
             Set the maximum number of existing candidates that
             will be considered when seeking a basis for a new
             straight-line strength reduction candidate.

  Options Controlling the Preprocessor
     These options control the C preprocessor, which is run on
     each C source file before actual compilation.

     If you use the -E option, nothing is done except
     preprocessing.  Some of these options make sense only
     together with -E because they cause the preprocessor output
     to be unsuitable for actual compilation.
     -Wp,option
         You can use -Wp,option to bypass the compiler driver and
         pass option directly through to the preprocessor.  If
         option contains commas, it is split into multiple
         options at the commas.  However, many options are
         modified, translated or interpreted by the compiler
         driver before being passed to the preprocessor, and -Wp
         forcibly bypasses this phase.  The preprocessor's direct
         interface is undocumented and subject to change, so
         whenever possible you should avoid using -Wp and let the
         driver handle the options instead.

     -Xpreprocessor option
         Pass option as an option to the preprocessor.  You can
         use this to supply system-specific preprocessor options
         that GCC does not recognize.

         If you want to pass an option that takes an argument,
         you must use -Xpreprocessor twice, once for the option
         and once for the argument.

     -no-integrated-cpp
         Perform preprocessing as a separate pass before
         compilation.  By default, GCC performs preprocessing as
         an integrated part of input tokenization and parsing.
         If this option is provided, the appropriate language
         front end (cc1, cc1plus, or cc1obj for C, C++, and
         Objective-C, respectively) is instead invoked twice,
         once for preprocessing only and once for actual
         compilation of the preprocessed input.  This option may
         be useful in conjunction with the -B or -wrapper options
         to specify an alternate preprocessor or perform
         additional processing of the program source between
         normal preprocessing and compilation.

     -D name
         Predefine name as a macro, with definition 1.

     -D name=definition
         The contents of definition are tokenized and processed
         as if they appeared during translation phase three in a
         #define directive.  In particular, the definition will
         be truncated by embedded newline characters.

         If you are invoking the preprocessor from a shell or
         shell-like program you may need to use the shell's
         quoting syntax to protect characters such as spaces that
         have a meaning in the shell syntax.

         If you wish to define a function-like macro on the
         command line, write its argument list with surrounding
         parentheses before the equals sign (if any).

         Parentheses are meaningful to most shells, so you will
         need to quote the option.  With sh and csh,
         -D'name(args...)=definition' works.

         -D and -U options are processed in the order they are
         given on the command line.  All -imacros file and
         -include file options are processed after all -D and -U
         options.

     -U name
         Cancel any previous definition of name, either built in
         or provided with a -D option.

     -undef
         Do not predefine any system-specific or GCC-specific
         macros.  The standard predefined macros remain defined.

     -I dir
         Add the directory dir to the list of directories to be
         searched for header files.  Directories named by -I are
         searched before the standard system include directories.
         If the directory dir is a standard system include
         directory, the option is ignored to ensure that the
         default search order for system directories and the
         special treatment of system headers are not defeated .
         If dir begins with "=", then the "=" will be replaced by
         the sysroot prefix; see --sysroot and -isysroot.

     -o file
         Write output to file.  This is the same as specifying
         file as the second non-option argument to cpp.  gcc has
         a different interpretation of a second non-option
         argument, so you must use -o to specify the output file.

     -Wall
         Turns on all optional warnings which are desirable for
         normal code.  At present this is -Wcomment, -Wtrigraphs,
         -Wmultichar and a warning about integer promotion
         causing a change of sign in "#if" expressions.  Note
         that many of the preprocessor's warnings are on by
         default and have no options to control them.

     -Wcomment
     -Wcomments
         Warn whenever a comment-start sequence /* appears in a
         /* comment, or whenever a backslash-newline appears in a
         // comment.  (Both forms have the same effect.)

     -Wtrigraphs
         Most trigraphs in comments cannot affect the meaning of
         the program.  However, a trigraph that would form an
         escaped newline (??/ at the end of a line) can, by
         changing where the comment begins or ends.  Therefore,
         only trigraphs that would form escaped newlines produce
         warnings inside a comment.

         This option is implied by -Wall.  If -Wall is not given,
         this option is still enabled unless trigraphs are
         enabled.  To get trigraph conversion without warnings,
         but get the other -Wall warnings, use -trigraphs -Wall
         -Wno-trigraphs.

     -Wtraditional
         Warn about certain constructs that behave differently in
         traditional and ISO C.  Also warn about ISO C constructs
         that have no traditional C equivalent, and problematic
         constructs which should be avoided.

     -Wundef
         Warn whenever an identifier which is not a macro is
         encountered in an #if directive, outside of defined.
         Such identifiers are replaced with zero.

     -Wunused-macros
         Warn about macros defined in the main file that are
         unused.  A macro is used if it is expanded or tested for
         existence at least once.  The preprocessor will also
         warn if the macro has not been used at the time it is
         redefined or undefined.

         Built-in macros, macros defined on the command line, and
         macros defined in include files are not warned about.

         Note: If a macro is actually used, but only used in
         skipped conditional blocks, then CPP will report it as
         unused.  To avoid the warning in such a case, you might
         improve the scope of the macro's definition by, for
         example, moving it into the first skipped block.
         Alternatively, you could provide a dummy use with
         something like:

                 #if defined the_macro_causing_the_warning
                 #endif

     -Wendif-labels
         Warn whenever an #else or an #endif are followed by
         text.  This usually happens in code of the form

                 #if FOO
                 ...
                 #else FOO
                 ...
                 #endif FOO

         The second and third "FOO" should be in comments, but
         often are not in older programs.  This warning is on by
         default.

     -Werror
         Make all warnings into hard errors.  Source code which
         triggers warnings will be rejected.

     -Wsystem-headers
         Issue warnings for code in system headers.  These are
         normally unhelpful in finding bugs in your own code,
         therefore suppressed.  If you are responsible for the
         system library, you may want to see them.

     -w  Suppress all warnings, including those which GNU CPP
         issues by default.

     -pedantic
         Issue all the mandatory diagnostics listed in the C
         standard.  Some of them are left out by default, since
         they trigger frequently on harmless code.

     -pedantic-errors
         Issue all the mandatory diagnostics, and make all
         mandatory diagnostics into errors.  This includes
         mandatory diagnostics that GCC issues without -pedantic
         but treats as warnings.

     -M  Instead of outputting the result of preprocessing,
         output a rule suitable for make describing the
         dependencies of the main source file.  The preprocessor
         outputs one make rule containing the object file name
         for that source file, a colon, and the names of all the
         included files, including those coming from -include or
         -imacros command line options.

         Unless specified explicitly (with -MT or -MQ), the
         object file name consists of the name of the source file
         with any suffix replaced with object file suffix and
         with any leading directory parts removed.  If there are
         many included files then the rule is split into several
         lines using \-newline.  The rule has no commands.

         This option does not suppress the preprocessor's debug
         output, such as -dM.  To avoid mixing such debug output
         with the dependency rules you should explicitly specify
         the dependency output file with -MF, or use an
         environment variable like DEPENDENCIES_OUTPUT.  Debug
         output will still be sent to the regular output stream
         as normal.

         Passing -M to the driver implies -E, and suppresses
         warnings with an implicit -w.

     -MM Like -M but do not mention header files that are found
         in system header directories, nor header files that are
         included, directly or indirectly, from such a header.

         This implies that the choice of angle brackets or double
         quotes in an #include directive does not in itself
         determine whether that header will appear in -MM
         dependency output.  This is a slight change in semantics
         from GCC versions 3.0 and earlier.

     -MF file
         When used with -M or -MM, specifies a file to write the
         dependencies to.  If no -MF switch is given the
         preprocessor sends the rules to the same place it would
         have sent preprocessed output.

         When used with the driver options -MD or -MMD, -MF
         overrides the default dependency output file.

     -MG In conjunction with an option such as -M requesting
         dependency generation, -MG assumes missing header files
         are generated files and adds them to the dependency list
         without raising an error.  The dependency filename is
         taken directly from the "#include" directive without
         prepending any path.  -MG also suppresses preprocessed
         output, as a missing header file renders this useless.

         This feature is used in automatic updating of makefiles.

     -MP This option instructs CPP to add a phony target for each
         dependency other than the main file, causing each to
         depend on nothing.  These dummy rules work around errors
         make gives if you remove header files without updating
         the Makefile to match.

         This is typical output:

                 test.o: test.c test.h

                 test.h:

     -MT target
         Change the target of the rule emitted by dependency
         generation.  By default CPP takes the name of the main
         input file, deletes any directory components and any
         file suffix such as .c, and appends the platform's usual
         object suffix.  The result is the target.

         An -MT option will set the target to be exactly the
         string you specify.  If you want multiple targets, you
         can specify them as a single argument to -MT, or use
         multiple -MT options.

         For example, -MT `$(objpfx)foo.o' might give

                 $(objpfx)foo.o: foo.c

     -MQ target
         Same as -MT, but it quotes any characters which are
         special to Make.  -MQ `$(objpfx)foo.o' gives

                 $$(objpfx)foo.o: foo.c

         The default target is automatically quoted, as if it
         were given with -MQ.

     -MD -MD is equivalent to -M -MF file, except that -E is not
         implied.  The driver determines file based on whether an
         -o option is given.  If it is, the driver uses its
         argument but with a suffix of .d, otherwise it takes the
         name of the input file, removes any directory components
         and suffix, and applies a .d suffix.

         If -MD is used in conjunction with -E, any -o switch is
         understood to specify the dependency output file, but if
         used without -E, each -o is understood to specify a
         target object file.

         Since -E is not implied, -MD can be used to generate a
         dependency output file as a side-effect of the
         compilation process.

     -MMD
         Like -MD except mention only user header files, not
         system header files.

     -fpch-deps
         When using precompiled headers, this flag will cause the
         dependency-output flags to also list the files from the
         precompiled header's dependencies.  If not specified
         only the precompiled header would be listed and not the
         files that were used to create it because those files
         are not consulted when a precompiled header is used.

     -fpch-preprocess
         This option allows use of a precompiled header together
         with -E.  It inserts a special "#pragma", "#pragma GCC
         pch_preprocess "filename"" in the output to mark the
         place where the precompiled header was found, and its
         filename.  When -fpreprocessed is in use, GCC recognizes
         this "#pragma" and loads the PCH.

         This option is off by default, because the resulting
         preprocessed output is only really suitable as input to
         GCC.  It is switched on by -save-temps.

         You should not write this "#pragma" in your own code,
         but it is safe to edit the filename if the PCH file is
         available in a different location.  The filename may be
         absolute or it may be relative to GCC's current
         directory.

     -x c
     -x c++
     -x objective-c
     -x assembler-with-cpp
         Specify the source language: C, C++, Objective-C, or
         assembly.  This has nothing to do with standards
         conformance or extensions; it merely selects which base
         syntax to expect.  If you give none of these options,
         cpp will deduce the language from the extension of the
         source file:  .c, .cc, .m, or .S.  Some other common
         extensions for C++ and assembly are also recognized.  If
         cpp does not recognize the extension, it will treat the
         file as C; this is the most generic mode.

         Note: Previous versions of cpp accepted a -lang option
         which selected both the language and the standards
         conformance level.  This option has been removed,
         because it conflicts with the -l option.

     -std=standard
     -ansi
         Specify the standard to which the code should conform.
         Currently CPP knows about C and C++ standards; others
         may be added in the future.

         standard may be one of:

         "c90"
         "c89"
         "iso9899:1990"
             The ISO C standard from 1990.  c90 is the customary
             shorthand for this version of the standard.

             The -ansi option is equivalent to -std=c90.

         "iso9899:199409"
             The 1990 C standard, as amended in 1994.

         "iso9899:1999"
         "c99"
         "iso9899:199x"
         "c9x"

             The revised ISO C standard, published in December
             1999.  Before publication, this was known as C9X.

         "iso9899:2011"
         "c11"
         "c1x"
             The revised ISO C standard, published in December
             2011.  Before publication, this was known as C1X.

         "gnu90"
         "gnu89"
             The 1990 C standard plus GNU extensions.  This is
             the default.

         "gnu99"
         "gnu9x"
             The 1999 C standard plus GNU extensions.

         "gnu11"
         "gnu1x"
             The 2011 C standard plus GNU extensions.

         "c++98"
             The 1998 ISO C++ standard plus amendments.

         "gnu++98"
             The same as -std=c++98 plus GNU extensions.  This is
             the default for C++ code.

     -I- Split the include path.  Any directories specified with
         -I options before -I- are searched only for headers
         requested with "#include "file""; they are not searched
         for "#include <file>".  If additional directories are
         specified with -I options after the -I-, those
         directories are searched for all #include directives.

         In addition, -I- inhibits the use of the directory of
         the current file directory as the first search directory
         for "#include "file"".  This option has been deprecated.

     -nostdinc
         Do not search the standard system directories for header
         files.  Only the directories you have specified with -I
         options (and the directory of the current file, if
         appropriate) are searched.

     -nostdinc++
         Do not search for header files in the C++-specific
         standard directories, but do still search the other
         standard directories.  (This option is used when
         building the C++ library.)

     -include file
         Process file as if "#include "file"" appeared as the
         first line of the primary source file.  However, the
         first directory searched for file is the preprocessor's
         working directory instead of the directory containing
         the main source file.  If not found there, it is
         searched for in the remainder of the "#include "...""
         search chain as normal.

         If multiple -include options are given, the files are
         included in the order they appear on the command line.

     -imacros file
         Exactly like -include, except that any output produced
         by scanning file is thrown away.  Macros it defines
         remain defined.  This allows you to acquire all the
         macros from a header without also processing its
         declarations.

         All files specified by -imacros are processed before all
         files specified by -include.

     -idirafter dir
         Search dir for header files, but do it after all
         directories specified with -I and the standard system
         directories have been exhausted.  dir is treated as a
         system include directory.  If dir begins with "=", then
         the "=" will be replaced by the sysroot prefix; see
         --sysroot and -isysroot.

     -iprefix prefix
         Specify prefix as the prefix for subsequent -iwithprefix
         options.  If the prefix represents a directory, you
         should include the final /.

     -iwithprefix dir
     -iwithprefixbefore dir
         Append dir to the prefix specified previously with
         -iprefix, and add the resulting directory to the include
         search path.  -iwithprefixbefore puts it in the same
         place -I would; -iwithprefix puts it where -idirafter
         would.

     -isysroot dir
         This option is like the --sysroot option, but applies
         only to header files (except for Darwin targets, where
         it applies to both header files and libraries).  See the
         --sysroot option for more information.

     -imultilib dir
         Use dir as a subdirectory of the directory containing
         target-specific C++ headers.

     -isystem dir
         Search dir for header files, after all directories
         specified by -I but before the standard system
         directories.  Mark it as a system directory, so that it
         gets the same special treatment as is applied to the
         standard system directories.  If dir begins with "=",
         then the "=" will be replaced by the sysroot prefix; see
         --sysroot and -isysroot.

     -iquote dir
         Search dir only for header files requested with
         "#include "file""; they are not searched for
         "#include <file>", before all directories specified by
         -I and before the standard system directories.  If dir
         begins with "=", then the "=" will be replaced by the
         sysroot prefix; see --sysroot and -isysroot.

     -fdirectives-only
         When preprocessing, handle directives, but do not expand
         macros.

         The option's behavior depends on the -E and
         -fpreprocessed options.

         With -E, preprocessing is limited to the handling of
         directives such as "#define", "#ifdef", and "#error".
         Other preprocessor operations, such as macro expansion
         and trigraph conversion are not performed.  In addition,
         the -dD option is implicitly enabled.

         With -fpreprocessed, predefinition of command line and
         most builtin macros is disabled.  Macros such as
         "__LINE__", which are contextually dependent, are
         handled normally.  This enables compilation of files
         previously preprocessed with "-E -fdirectives-only".

         With both -E and -fpreprocessed, the rules for
         -fpreprocessed take precedence.  This enables full
         preprocessing of files previously preprocessed with "-E
         -fdirectives-only".

     -fdollars-in-identifiers
         Accept $ in identifiers.

     -fextended-identifiers
         Accept universal character names in identifiers.  This
         option is experimental; in a future version of GCC, it
         will be enabled by default for C99 and C++.

     -fno-canonical-system-headers
         When preprocessing, do not shorten system header paths
         with canonicalization.

     -fpreprocessed
         Indicate to the preprocessor that the input file has
         already been preprocessed.  This suppresses things like
         macro expansion, trigraph conversion, escaped newline
         splicing, and processing of most directives.  The
         preprocessor still recognizes and removes comments, so
         that you can pass a file preprocessed with -C to the
         compiler without problems.  In this mode the integrated
         preprocessor is little more than a tokenizer for the
         front ends.

         -fpreprocessed is implicit if the input file has one of
         the extensions .i, .ii or .mi.  These are the extensions
         that GCC uses for preprocessed files created by
         -save-temps.

     -ftabstop=width
         Set the distance between tab stops.  This helps the
         preprocessor report correct column numbers in warnings
         or errors, even if tabs appear on the line.  If the
         value is less than 1 or greater than 100, the option is
         ignored.  The default is 8.

     -fdebug-cpp
         This option is only useful for debugging GCC.  When used
         with -E, dumps debugging information about location
         maps.  Every token in the output is preceded by the dump
         of the map its location belongs to.  The dump of the map
         holding the location of a token would be:

                 {"P":F</file/path>;"F":F</includer/path>;"L":<line_num>;"C":<col_num>;"S":<system_header_p>;"M":<map_address>;"E":<macro_expansion_p>,"loc":<location>}

         When used without -E, this option has no effect.

     -ftrack-macro-expansion[=level]
         Track locations of tokens across macro expansions. This
         allows the compiler to emit diagnostic about the current
         macro expansion stack when a compilation error occurs in
         a macro expansion. Using this option makes the
         preprocessor and the compiler consume more memory. The
         level parameter can be used to choose the level of
         precision of token location tracking thus decreasing the
         memory consumption if necessary. Value 0 of level de-
         activates this option just as if no
         -ftrack-macro-expansion was present on the command line.
         Value 1 tracks tokens locations in a degraded mode for
         the sake of minimal memory overhead. In this mode all
         tokens resulting from the expansion of an argument of a
         function-like macro have the same location. Value 2
         tracks tokens locations completely. This value is the
         most memory hungry.  When this option is given no
         argument, the default parameter value is 2.

         Note that -ftrack-macro-expansion=2 is activated by
         default.

     -fexec-charset=charset
         Set the execution character set, used for string and
         character constants.  The default is UTF-8.  charset can
         be any encoding supported by the system's "iconv"
         library routine.

     -fwide-exec-charset=charset
         Set the wide execution character set, used for wide
         string and character constants.  The default is UTF-32
         or UTF-16, whichever corresponds to the width of
         "wchar_t".  As with -fexec-charset, charset can be any
         encoding supported by the system's "iconv" library
         routine; however, you will have problems with encodings
         that do not fit exactly in "wchar_t".

     -finput-charset=charset
         Set the input character set, used for translation from
         the character set of the input file to the source
         character set used by GCC.  If the locale does not
         specify, or GCC cannot get this information from the
         locale, the default is UTF-8.  This can be overridden by
         either the locale or this command line option.
         Currently the command line option takes precedence if
         there's a conflict.  charset can be any encoding
         supported by the system's "iconv" library routine.

     -fworking-directory
         Enable generation of linemarkers in the preprocessor
         output that will let the compiler know the current
         working directory at the time of preprocessing.  When
         this option is enabled, the preprocessor will emit,
         after the initial linemarker, a second linemarker with
         the current working directory followed by two slashes.
         GCC will use this directory, when it's present in the
         preprocessed input, as the directory emitted as the
         current working directory in some debugging information
         formats.  This option is implicitly enabled if debugging
         information is enabled, but this can be inhibited with
         the negated form -fno-working-directory.  If the -P flag
         is present in the command line, this option has no
         effect, since no "#line" directives are emitted
         whatsoever.

     -fno-show-column
         Do not print column numbers in diagnostics.  This may be
         necessary if diagnostics are being scanned by a program
         that does not understand the column numbers, such as
         dejagnu.

     -A predicate=answer
         Make an assertion with the predicate predicate and
         answer answer.  This form is preferred to the older form
         -A predicate(answer), which is still supported, because
         it does not use shell special characters.

     -A -predicate=answer
         Cancel an assertion with the predicate predicate and
         answer answer.

     -dCHARS
         CHARS is a sequence of one or more of the following
         characters, and must not be preceded by a space.  Other
         characters are interpreted by the compiler proper, or
         reserved for future versions of GCC, and so are silently
         ignored.  If you specify characters whose behavior
         conflicts, the result is undefined.

         M   Instead of the normal output, generate a list of
             #define directives for all the macros defined during
             the execution of the preprocessor, including
             predefined macros.  This gives you a way of finding
             out what is predefined in your version of the
             preprocessor.  Assuming you have no file foo.h, the
             command

                     touch foo.h; cpp -dM foo.h

             will show all the predefined macros.

             If you use -dM without the -E option, -dM is
             interpreted as a synonym for -fdump-rtl-mach.

         D   Like M except in two respects: it does not include
             the predefined macros, and it outputs both the
             #define directives and the result of preprocessing.
             Both kinds of output go to the standard output file.

         N   Like D, but emit only the macro names, not their
             expansions.

         I   Output #include directives in addition to the result
             of preprocessing.

         U   Like D except that only macros that are expanded, or
             whose definedness is tested in preprocessor
             directives, are output; the output is delayed until
             the use or test of the macro; and #undef directives
             are also output for macros tested but undefined at
             the time.

     -P  Inhibit generation of linemarkers in the output from the

         preprocessor.  This might be useful when running the
         preprocessor on something that is not C code, and will
         be sent to a program which might be confused by the
         linemarkers.

     -C  Do not discard comments.  All comments are passed
         through to the output file, except for comments in
         processed directives, which are deleted along with the
         directive.

         You should be prepared for side effects when using -C;
         it causes the preprocessor to treat comments as tokens
         in their own right.  For example, comments appearing at
         the start of what would be a directive line have the
         effect of turning that line into an ordinary source
         line, since the first token on the line is no longer a
         #.

     -CC Do not discard comments, including during macro
         expansion.  This is like -C, except that comments
         contained within macros are also passed through to the
         output file where the macro is expanded.

         In addition to the side-effects of the -C option, the
         -CC option causes all C++-style comments inside a macro
         to be converted to C-style comments.  This is to prevent
         later use of that macro from inadvertently commenting
         out the remainder of the source line.

         The -CC option is generally used to support lint
         comments.

     -traditional-cpp
         Try to imitate the behavior of old-fashioned C
         preprocessors, as opposed to ISO C preprocessors.

     -trigraphs
         Process trigraph sequences.  These are three-character
         sequences, all starting with ??, that are defined by ISO
         C to stand for single characters.  For example, ??/
         stands for \, so `??/n' is a character constant for a
         newline.  By default, GCC ignores trigraphs, but in
         standard-conforming modes it converts them.  See the
         -std and -ansi options.

         The nine trigraphs and their replacements are

                 Trigraph:       ??(  ??)  ??<  ??>  ??=  ??/  ??'  ??!  ??-
                 Replacement:      [    ]    {    }    #   \    ^    |    ~

     -remap
         Enable special code to work around file systems which
         only permit very short file names, such as MS-DOS.

     --help
     --target-help
         Print text describing all the command line options
         instead of preprocessing anything.

     -v  Verbose mode.  Print out GNU CPP's version number at the
         beginning of execution, and report the final form of the
         include path.

     -H  Print the name of each header file used, in addition to
         other normal activities.  Each name is indented to show
         how deep in the #include stack it is.  Precompiled
         header files are also printed, even if they are found to
         be invalid; an invalid precompiled header file is
         printed with ...x and a valid one with ...! .

     -version
     --version
         Print out GNU CPP's version number.  With one dash,
         proceed to preprocess as normal.  With two dashes, exit
         immediately.

  Passing Options to the Assembler
     You can pass options to the assembler.

     -Wa,option
         Pass option as an option to the assembler.  If option
         contains commas, it is split into multiple options at
         the commas.

     -Xassembler option
         Pass option as an option to the assembler.  You can use
         this to supply system-specific assembler options that
         GCC does not recognize.

         If you want to pass an option that takes an argument,
         you must use -Xassembler twice, once for the option and
         once for the argument.

  Options for Linking
     These options come into play when the compiler links object
     files into an executable output file.  They are meaningless
     if the compiler is not doing a link step.

     object-file-name
         A file name that does not end in a special recognized
         suffix is considered to name an object file or library.
         (Object files are distinguished from libraries by the
         linker according to the file contents.)  If linking is
         done, these object files are used as input to the
         linker.

     -c
     -S
     -E  If any of these options is used, then the linker is not
         run, and object file names should not be used as
         arguments.

     -llibrary
     -l library
         Search the library named library when linking.  (The
         second alternative with the library as a separate
         argument is only for POSIX compliance and is not
         recommended.)

         It makes a difference where in the command you write
         this option; the linker searches and processes libraries
         and object files in the order they are specified.  Thus,
         foo.o -lz bar.o searches library z after file foo.o but
         before bar.o.  If bar.o refers to functions in z, those
         functions may not be loaded.

         The linker searches a standard list of directories for
         the library, which is actually a file named
         liblibrary.a.  The linker then uses this file as if it
         had been specified precisely by name.

         The directories searched include several standard system
         directories plus any that you specify with -L.

         Normally the files found this way are library
         files---archive files whose members are object files.
         The linker handles an archive file by scanning through
         it for members which define symbols that have so far
         been referenced but not defined.  But if the file that
         is found is an ordinary object file, it is linked in the
         usual fashion.  The only difference between using an -l
         option and specifying a file name is that -l surrounds
         library with lib and .a and searches several
         directories.

     -lobjc
         You need this special case of the -l option in order to
         link an Objective-C or Objective-C++ program.

     -nostartfiles
         Do not use the standard system startup files when
         linking.  The standard system libraries are used
         normally, unless -nostdlib or -nodefaultlibs is used.

     -nodefaultlibs
         Do not use the standard system libraries when linking.

         Only the libraries you specify are passed to the linker,
         and options specifying linkage of the system libraries,
         such as "-static-libgcc" or "-shared-libgcc", are
         ignored. The standard startup files are used normally,
         unless -nostartfiles is used.

         The compiler may generate calls to "memcmp", "memset",
         "memcpy" and "memmove".  These entries are usually
         resolved by entries in libc.  These entry points should
         be supplied through some other mechanism when this
         option is specified.

     -nostdlib
         Do not use the standard system startup files or
         libraries when linking.  No startup files and only the
         libraries you specify are passed to the linker, and
         options specifying linkage of the system libraries, such
         as "-static-libgcc" or "-shared-libgcc", are ignored.

         The compiler may generate calls to "memcmp", "memset",
         "memcpy" and "memmove".  These entries are usually
         resolved by entries in libc.  These entry points should
         be supplied through some other mechanism when this
         option is specified.

         One of the standard libraries bypassed by -nostdlib and
         -nodefaultlibs is libgcc.a, a library of internal
         subroutines which GCC uses to overcome shortcomings of
         particular machines, or special needs for some
         languages.

         In most cases, you need libgcc.a even when you want to
         avoid other standard libraries.  In other words, when
         you specify -nostdlib or -nodefaultlibs you should
         usually specify -lgcc as well.  This ensures that you
         have no unresolved references to internal GCC library
         subroutines.  (An example of such an internal subroutine
         is __main, used to ensure C++ constructors are called.)

     -pie
         Produce a position independent executable on targets
         that support it.  For predictable results, you must also
         specify the same set of options used for compilation
         (-fpie, -fPIE, or model suboptions) when you specify
         this linker option.

     -rdynamic
         Pass the flag -export-dynamic to the ELF linker, on
         targets that support it. This instructs the linker to
         add all symbols, not only used ones, to the dynamic
         symbol table. This option is needed for some uses of
         "dlopen" or to allow obtaining backtraces from within a
         program.

     -s  Remove all symbol table and relocation information from
         the executable.

     -static
         On systems that support dynamic linking, this prevents
         linking with the shared libraries.  On other systems,
         this option has no effect.

     -shared
         Produce a shared object which can then be linked with
         other objects to form an executable.  Not all systems
         support this option.  For predictable results, you must
         also specify the same set of options used for
         compilation (-fpic, -fPIC, or model suboptions) when you
         specify this linker option.[1]

     -shared-libgcc
     -static-libgcc
         On systems that provide libgcc as a shared library,
         these options force the use of either the shared or
         static version, respectively.  If no shared version of
         libgcc was built when the compiler was configured, these
         options have no effect.

         There are several situations in which an application
         should use the shared libgcc instead of the static
         version.  The most common of these is when the
         application wishes to throw and catch exceptions across
         different shared libraries.  In that case, each of the
         libraries as well as the application itself should use
         the shared libgcc.

         Therefore, the G++ and GCJ drivers automatically add
         -shared-libgcc whenever you build a shared library or a
         main executable, because C++ and Java programs typically
         use exceptions, so this is the right thing to do.

         If, instead, you use the GCC driver to create shared
         libraries, you may find that they are not always linked
         with the shared libgcc.  If GCC finds, at its
         configuration time, that you have a non-GNU linker or a
         GNU linker that does not support option --eh-frame-hdr,
         it links the shared version of libgcc into shared
         libraries by default.  Otherwise, it takes advantage of
         the linker and optimizes away the linking with the
         shared version of libgcc, linking with the static
         version of libgcc by default.  This allows exceptions to
         propagate through such shared libraries, without
         incurring relocation costs at library load time.

         However, if a library or main executable is supposed to
         throw or catch exceptions, you must link it using the
         G++ or GCJ driver, as appropriate for the languages used
         in the program, or using the option -shared-libgcc, such
         that it is linked with the shared libgcc.

     -static-libasan
         When the -fsanitize=address option is used to link a
         program, the GCC driver automatically links against
         libasan.  If libasan is available as a shared library,
         and the -static option is not used, then this links
         against the shared version of libasan.  The
         -static-libasan option directs the GCC driver to link
         libasan statically, without necessarily linking other
         libraries statically.

     -static-libtsan
         When the -fsanitize=thread option is used to link a
         program, the GCC driver automatically links against
         libtsan.  If libtsan is available as a shared library,
         and the -static option is not used, then this links
         against the shared version of libtsan.  The
         -static-libtsan option directs the GCC driver to link
         libtsan statically, without necessarily linking other
         libraries statically.

     -static-libstdc++
         When the g++ program is used to link a C++ program, it
         normally automatically links against libstdc++.  If
         libstdc++ is available as a shared library, and the
         -static option is not used, then this links against the
         shared version of libstdc++.  That is normally fine.
         However, it is sometimes useful to freeze the version of
         libstdc++ used by the program without going all the way
         to a fully static link.  The -static-libstdc++ option
         directs the g++ driver to link libstdc++ statically,
         without necessarily linking other libraries statically.

     -symbolic
         Bind references to global symbols when building a shared
         object.  Warn about any unresolved references (unless
         overridden by the link editor option -Xlinker -z
         -Xlinker defs).  Only a few systems support this option.

     -T script
         Use script as the linker script.  This option is
         supported by most systems using the GNU linker.  On some
         targets, such as bare-board targets without an operating
         system, the -T option may be required when linking to
         avoid references to undefined symbols.

     -Xlinker option

         Pass option as an option to the linker.  You can use
         this to supply system-specific linker options that GCC
         does not recognize.

         If you want to pass an option that takes a separate
         argument, you must use -Xlinker twice, once for the
         option and once for the argument.  For example, to pass
         -assert definitions, you must write -Xlinker -assert
         -Xlinker definitions.  It does not work to write
         -Xlinker "-assert definitions", because this passes the
         entire string as a single argument, which is not what
         the linker expects.

         When using the GNU linker, it is usually more convenient
         to pass arguments to linker options using the
         option=value syntax than as separate arguments.  For
         example, you can specify -Xlinker -Map=output.map rather
         than -Xlinker -Map -Xlinker output.map.  Other linkers
         may not support this syntax for command-line options.

     -Wl,option
         Pass option as an option to the linker.  If option
         contains commas, it is split into multiple options at
         the commas.  You can use this syntax to pass an argument
         to the option.  For example, -Wl,-Map,output.map passes
         -Map output.map to the linker.  When using the GNU
         linker, you can also get the same effect with
         -Wl,-Map=output.map.

     -u symbol
         Pretend the symbol symbol is undefined, to force linking
         of library modules to define it.  You can use -u
         multiple times with different symbols to force loading
         of additional library modules.

  Options for Directory Search
     These options specify directories to search for header
     files, for libraries and for parts of the compiler:

     -Idir
         Add the directory dir to the head of the list of
         directories to be searched for header files.  This can
         be used to override a system header file, substituting
         your own version, since these directories are searched
         before the system header file directories.  However, you
         should not use this option to add directories that
         contain vendor-supplied system header files (use
         -isystem for that).  If you use more than one -I option,
         the directories are scanned in left-to-right order; the
         standard system directories come after.

         If a standard system include directory, or a directory
         specified with -isystem, is also specified with -I, the
         -I option is ignored.  The directory is still searched
         but as a system directory at its normal position in the
         system include chain.  This is to ensure that GCC's
         procedure to fix buggy system headers and the ordering
         for the "include_next" directive are not inadvertently
         changed.  If you really need to change the search order
         for system directories, use the -nostdinc and/or
         -isystem options.

     -iplugindir=dir
         Set the directory to search for plugins that are passed
         by -fplugin=name instead of -fplugin=path/name.so.  This
         option is not meant to be used by the user, but only
         passed by the driver.

     -iquotedir
         Add the directory dir to the head of the list of
         directories to be searched for header files only for the
         case of #include "file"; they are not searched for
         #include <file>, otherwise just like -I.

     -Ldir
         Add directory dir to the list of directories to be
         searched for -l.

     -Bprefix
         This option specifies where to find the executables,
         libraries, include files, and data files of the compiler
         itself.

         The compiler driver program runs one or more of the
         subprograms cpp, cc1, as and ld.  It tries prefix as a
         prefix for each program it tries to run, both with and
         without machine/version/.

         For each subprogram to be run, the compiler driver first
         tries the -B prefix, if any.  If that name is not found,
         or if -B is not specified, the driver tries two standard
         prefixes, /usr/lib/gcc/ and /usr/local/lib/gcc/.  If
         neither of those results in a file name that is found,
         the unmodified program name is searched for using the
         directories specified in your PATH environment variable.

         The compiler checks to see if the path provided by the
         -B refers to a directory, and if necessary it adds a
         directory separator character at the end of the path.

         -B prefixes that effectively specify directory names
         also apply to libraries in the linker, because the
         compiler translates these options into -L options for
         the linker.  They also apply to includes files in the
         preprocessor, because the compiler translates these
         options into -isystem options for the preprocessor.  In
         this case, the compiler appends include to the prefix.

         The runtime support file libgcc.a can also be searched
         for using the -B prefix, if needed.  If it is not found
         there, the two standard prefixes above are tried, and
         that is all.  The file is left out of the link if it is
         not found by those means.

         Another way to specify a prefix much like the -B prefix
         is to use the environment variable GCC_EXEC_PREFIX.

         As a special kludge, if the path provided by -B is
         [dir/]stageN/, where N is a number in the range 0 to 9,
         then it is replaced by [dir/]include.  This is to help
         with boot-strapping the compiler.

     -specs=file
         Process file after the compiler reads in the standard
         specs file, in order to override the defaults which the
         gcc driver program uses when determining what switches
         to pass to cc1, cc1plus, as, ld, etc.  More than one
         -specs=file can be specified on the command line, and
         they are processed in order, from left to right.

     --sysroot=dir
         Use dir as the logical root directory for headers and
         libraries.  For example, if the compiler normally
         searches for headers in /usr/include and libraries in
         /usr/lib, it instead searches dir/usr/include and
         dir/usr/lib.

         If you use both this option and the -isysroot option,
         then the --sysroot option applies to libraries, but the
         -isysroot option applies to header files.

         The GNU linker (beginning with version 2.16) has the
         necessary support for this option.  If your linker does
         not support this option, the header file aspect of
         --sysroot still works, but the library aspect does not.

     --no-sysroot-suffix
         For some targets, a suffix is added to the root
         directory specified with --sysroot, depending on the
         other options used, so that headers may for example be
         found in dir/suffix/usr/include instead of
         dir/usr/include.  This option disables the addition of
         such a suffix.

     -I- This option has been deprecated.  Please use -iquote
         instead for -I directories before the -I- and remove the
         -I-.  Any directories you specify with -I options before
         the -I- option are searched only for the case of
         #include "file"; they are not searched for #include
         <file>.

         If additional directories are specified with -I options
         after the -I-, these directories are searched for all
         #include directives.  (Ordinarily all -I directories are
         used this way.)

         In addition, the -I- option inhibits the use of the
         current directory (where the current input file came
         from) as the first search directory for #include "file".
         There is no way to override this effect of -I-.  With
         -I. you can specify searching the directory that is
         current when the compiler is invoked.  That is not
         exactly the same as what the preprocessor does by
         default, but it is often satisfactory.

         -I- does not inhibit the use of the standard system
         directories for header files.  Thus, -I- and -nostdinc
         are independent.

  Specifying Target Machine and Compiler Version
     The usual way to run GCC is to run the executable called
     gcc, or machine-gcc when cross-compiling, or
     machine-gcc-version to run a version other than the one that
     was installed last.

  Hardware Models and Configurations
     Each target machine types can have its own special options,
     starting with -m, to choose among various hardware models or
     configurations---for example, 68010 vs 68020, floating
     coprocessor or none.  A single installed version of the
     compiler can compile for any model or configuration,
     according to the options specified.

     Some configurations of the compiler also support additional
     special options, usually for compatibility with other
     compilers on the same platform.

     AArch64 Options

     These options are defined for AArch64 implementations:

     -mbig-endian
         Generate big-endian code.  This is the default when GCC
         is configured for an aarch64_be-*-* target.

     -mgeneral-regs-only
         Generate code which uses only the general registers.

     -mlittle-endian
         Generate little-endian code.  This is the default when
         GCC is configured for an aarch64-*-* but not an
         aarch64_be-*-* target.

     -mcmodel=tiny
         Generate code for the tiny code model.  The program and
         its statically defined symbols must be within 1GB of
         each other.  Pointers are 64 bits.  Programs can be
         statically or dynamically linked.  This model is not
         fully implemented and mostly treated as small.

     -mcmodel=small
         Generate code for the small code model.  The program and
         its statically defined symbols must be within 4GB of
         each other.  Pointers are 64 bits.  Programs can be
         statically or dynamically linked.  This is the default
         code model.

     -mcmodel=large
         Generate code for the large code model.  This makes no
         assumptions about addresses and sizes of sections.
         Pointers are 64 bits.  Programs can be statically linked
         only.

     -mstrict-align
         Do not assume that unaligned memory references will be
         handled by the system.

     -momit-leaf-frame-pointer
     -mno-omit-leaf-frame-pointer
         Omit or keep the frame pointer in leaf functions.  The
         former behaviour is the default.

     -mtls-dialect=desc
         Use TLS descriptors as the thread-local storage
         mechanism for dynamic accesses of TLS variables.  This
         is the default.

     -mtls-dialect=traditional
         Use traditional TLS as the thread-local storage
         mechanism for dynamic accesses of TLS variables.

     -march=name
         Specify the name of the target architecture, optionally
         suffixed by one or more feature modifiers.  This option
         has the form -march=arch{+[no]feature}*, where the only
         value for arch is armv8-a.  The possible values for
         feature are documented in the sub-section below.

         Where conflicting feature modifiers are specified, the
         right-most feature is used.

         GCC uses this name to determine what kind of
         instructions it can emit when generating assembly code.
         This option can be used in conjunction with or instead
         of the -mcpu= option.

     -mcpu=name
         Specify the name of the target processor, optionally
         suffixed by one or more feature modifiers.  This option
         has the form -mcpu=cpu{+[no]feature}*, where the
         possible values for cpu are generic, large.  The
         possible values for feature are documented in the sub-
         section below.

         Where conflicting feature modifiers are specified, the
         right-most feature is used.

         GCC uses this name to determine what kind of
         instructions it can emit when generating assembly code.

     -mtune=name
         Specify the name of the processor to tune the
         performance for.  The code will be tuned as if the
         target processor were of the type specified in this
         option, but still using instructions compatible with the
         target processor specified by a -mcpu= option.  This
         option cannot be suffixed by feature modifiers.

     -march and -mcpu feature modifiers

     Feature modifiers used with -march and -mcpu can be one the
     following:

     crypto
         Enable Crypto extension.  This implies Advanced SIMD is
         enabled.

     fp  Enable floating-point instructions.

     simd
         Enable Advanced SIMD instructions.  This implies
         floating-point instructions are enabled.  This is the
         default for all current possible values for options
         -march and -mcpu=.

     Adapteva Epiphany Options

     These -m options are defined for Adapteva Epiphany:

     -mhalf-reg-file
         Don't allocate any register in the range "r32"..."r63".
         That allows code to run on hardware variants that lack
         these registers.

     -mprefer-short-insn-regs
         Preferrentially allocate registers that allow short
         instruction generation.  This can result in increased
         instruction count, so this may either reduce or increase
         overall code size.

     -mbranch-cost=num
         Set the cost of branches to roughly num "simple"
         instructions.  This cost is only a heuristic and is not
         guaranteed to produce consistent results across
         releases.

     -mcmove
         Enable the generation of conditional moves.

     -mnops=num
         Emit num NOPs before every other generated instruction.

     -mno-soft-cmpsf
         For single-precision floating-point comparisons, emit an
         "fsub" instruction and test the flags.  This is faster
         than a software comparison, but can get incorrect
         results in the presence of NaNs, or when two different
         small numbers are compared such that their difference is
         calculated as zero.  The default is -msoft-cmpsf, which
         uses slower, but IEEE-compliant, software comparisons.

     -mstack-offset=num
         Set the offset between the top of the stack and the
         stack pointer.  E.g., a value of 8 means that the eight
         bytes in the range "sp+0...sp+7" can be used by leaf
         functions without stack allocation.  Values other than 8
         or 16 are untested and unlikely to work.  Note also that
         this option changes the ABI; compiling a program with a
         different stack offset than the libraries have been
         compiled with generally does not work.  This option can
         be useful if you want to evaluate if a different stack
         offset would give you better code, but to actually use a
         different stack offset to build working programs, it is
         recommended to configure the toolchain with the
         appropriate --with-stack-offset=num option.

     -mno-round-nearest
         Make the scheduler assume that the rounding mode has
         been set to truncating.  The default is -mround-nearest.

     -mlong-calls
         If not otherwise specified by an attribute, assume all
         calls might be beyond the offset range of the "b" / "bl"
         instructions, and therefore load the function address
         into a register before performing a (otherwise direct)
         call.  This is the default.

     -mshort-calls
         If not otherwise specified by an attribute, assume all
         direct calls are in the range of the "b" / "bl"
         instructions, so use these instructions for direct
         calls.  The default is -mlong-calls.

     -msmall16
         Assume addresses can be loaded as 16-bit unsigned
         values.  This does not apply to function addresses for
         which -mlong-calls semantics are in effect.

     -mfp-mode=mode
         Set the prevailing mode of the floating-point unit.
         This determines the floating-point mode that is provided
         and expected at function call and return time.  Making
         this mode match the mode you predominantly need at
         function start can make your programs smaller and faster
         by avoiding unnecessary mode switches.

         mode can be set to one the following values:

         caller
             Any mode at function entry is valid, and retained or
             restored when the function returns, and when it
             calls other functions.  This mode is useful for
             compiling libraries or other compilation units you
             might want to incorporate into different programs
             with different prevailing FPU modes, and the
             convenience of being able to use a single object
             file outweighs the size and speed overhead for any
             extra mode switching that might be needed, compared
             with what would be needed with a more specific
             choice of prevailing FPU mode.

         truncate
             This is the mode used for floating-point
             calculations with truncating (i.e. round towards
             zero) rounding mode.  That includes conversion from
             floating point to integer.

         round-nearest
             This is the mode used for floating-point
             calculations with round-to-nearest-or-even rounding
             mode.

         int This is the mode used to perform integer
             calculations in the FPU, e.g.  integer multiply, or
             integer multiply-and-accumulate.

         The default is -mfp-mode=caller

     -mnosplit-lohi
     -mno-postinc
     -mno-postmodify
         Code generation tweaks that disable, respectively,
         splitting of 32-bit loads, generation of post-increment
         addresses, and generation of post-modify addresses.  The
         defaults are msplit-lohi, -mpost-inc, and -mpost-modify.

     -mnovect-double
         Change the preferred SIMD mode to SImode.  The default
         is -mvect-double, which uses DImode as preferred SIMD
         mode.

     -max-vect-align=num
         The maximum alignment for SIMD vector mode types.  num
         may be 4 or 8.  The default is 8.  Note that this is an
         ABI change, even though many library function interfaces
         are unaffected if they don't use SIMD vector modes in
         places that affect size and/or alignment of relevant
         types.

     -msplit-vecmove-early
         Split vector moves into single word moves before reload.
         In theory this can give better register allocation, but
         so far the reverse seems to be generally the case.

     -m1reg-reg
         Specify a register to hold the constant -1, which makes
         loading small negative constants and certain bitmasks
         faster.  Allowable values for reg are r43 and r63, which
         specify use of that register as a fixed register, and
         none, which means that no register is used for this
         purpose.  The default is -m1reg-none.

     ARM Options

     These -m options are defined for Advanced RISC Machines
     (ARM) architectures:

     -mabi=name
         Generate code for the specified ABI.  Permissible values
         are: apcs-gnu, atpcs, aapcs, aapcs-linux and iwmmxt.

     -mapcs-frame
         Generate a stack frame that is compliant with the ARM
         Procedure Call Standard for all functions, even if this
         is not strictly necessary for correct execution of the
         code.  Specifying -fomit-frame-pointer with this option
         causes the stack frames not to be generated for leaf
         functions.  The default is -mno-apcs-frame.

     -mapcs
         This is a synonym for -mapcs-frame.

     -mthumb-interwork
         Generate code that supports calling between the ARM and
         Thumb instruction sets.  Without this option, on pre-v5
         architectures, the two instruction sets cannot be
         reliably used inside one program.  The default is
         -mno-thumb-interwork, since slightly larger code is
         generated when -mthumb-interwork is specified.  In AAPCS
         configurations this option is meaningless.

     -mno-sched-prolog
         Prevent the reordering of instructions in the function
         prologue, or the merging of those instruction with the
         instructions in the function's body.  This means that
         all functions start with a recognizable set of
         instructions (or in fact one of a choice from a small
         set of different function prologues), and this
         information can be used to locate the start of functions
         inside an executable piece of code.  The default is
         -msched-prolog.

     -mfloat-abi=name
         Specifies which floating-point ABI to use.  Permissible
         values are: soft, softfp and hard.

         Specifying soft causes GCC to generate output containing
         library calls for floating-point operations.  softfp
         allows the generation of code using hardware floating-
         point instructions, but still uses the soft-float
         calling conventions.  hard allows generation of
         floating-point instructions and uses FPU-specific
         calling conventions.

         The default depends on the specific target
         configuration.  Note that the hard-float and soft-float
         ABIs are not link-compatible; you must compile your
         entire program with the same ABI, and link with a
         compatible set of libraries.

     -mlittle-endian
         Generate code for a processor running in little-endian
         mode.  This is the default for all standard
         configurations.

     -mbig-endian
         Generate code for a processor running in big-endian
         mode; the default is to compile code for a little-endian
         processor.

     -mwords-little-endian
         This option only applies when generating code for big-
         endian processors.  Generate code for a little-endian
         word order but a big-endian byte order.  That is, a byte
         order of the form 32107654.  Note: this option should
         only be used if you require compatibility with code for
         big-endian ARM processors generated by versions of the
         compiler prior to 2.8.  This option is now deprecated.

     -mcpu=name
         This specifies the name of the target ARM processor.
         GCC uses this name to determine what kind of
         instructions it can emit when generating assembly code.
         Permissible names are: arm2, arm250, arm3, arm6, arm60,
         arm600, arm610, arm620, arm7, arm7m, arm7d, arm7dm,
         arm7di, arm7dmi, arm70, arm700, arm700i, arm710,
         arm710c, arm7100, arm720, arm7500, arm7500fe, arm7tdmi,
         arm7tdmi-s, arm710t, arm720t, arm740t, strongarm,
         strongarm110, strongarm1100, strongarm1110, arm8,
         arm810, arm9, arm9e, arm920, arm920t, arm922t,
         arm946e-s, arm966e-s, arm968e-s, arm926ej-s, arm940t,
         arm9tdmi, arm10tdmi, arm1020t, arm1026ej-s, arm10e,
         arm1020e, arm1022e, arm1136j-s, arm1136jf-s, mpcore,
         mpcorenovfp, arm1156t2-s, arm1156t2f-s, arm1176jz-s,
         arm1176jzf-s, cortex-a5, cortex-a7, cortex-a8,
         cortex-a9, cortex-a15, cortex-r4, cortex-r4f, cortex-r5,
         cortex-m4, cortex-m3, cortex-m1, cortex-m0,
         cortex-m0plus, marvell-pj4, xscale, iwmmxt, iwmmxt2,
         ep9312, fa526, fa626, fa606te, fa626te, fmp626, fa726te.

         -mcpu=generic-arch is also permissible, and is
         equivalent to -march=arch -mtune=generic-arch.  See
         -mtune for more information.

         -mcpu=native causes the compiler to auto-detect the CPU
         of the build computer.  At present, this feature is only
         supported on Linux, and not all architectures are
         recognized.  If the auto-detect is unsuccessful the
         option has no effect.

     -mtune=name
         This option is very similar to the -mcpu= option, except
         that instead of specifying the actual target processor
         type, and hence restricting which instructions can be
         used, it specifies that GCC should tune the performance
         of the code as if the target were of the type specified
         in this option, but still choosing the instructions it
         generates based on the CPU specified by a -mcpu= option.
         For some ARM implementations better performance can be
         obtained by using this option.

         -mtune=generic-arch specifies that GCC should tune the
         performance for a blend of processors within
         architecture arch.  The aim is to generate code that run
         well on the current most popular processors, balancing
         between optimizations that benefit some CPUs in the
         range, and avoiding performance pitfalls of other CPUs.
         The effects of this option may change in future GCC
         versions as CPU models come and go.

         -mtune=native causes the compiler to auto-detect the CPU
         of the build computer.  At present, this feature is only
         supported on Linux, and not all architectures are
         recognized.  If the auto-detect is unsuccessful the
         option has no effect.

     -march=name
         This specifies the name of the target ARM architecture.
         GCC uses this name to determine what kind of
         instructions it can emit when generating assembly code.
         This option can be used in conjunction with or instead
         of the -mcpu= option.  Permissible names are: armv2,
         armv2a, armv3, armv3m, armv4, armv4t, armv5, armv5t,
         armv5e, armv5te, armv6, armv6j, armv6t2, armv6z,
         armv6zk, armv6-m, armv7, armv7-a, armv7-r, armv7-m,
         armv8-a, iwmmxt, iwmmxt2, ep9312.

         -march=native causes the compiler to auto-detect the
         architecture of the build computer.  At present, this
         feature is only supported on Linux, and not all
         architectures are recognized.  If the auto-detect is
         unsuccessful the option has no effect.

     -mfpu=name
         This specifies what floating-point hardware (or hardware
         emulation) is available on the target.  Permissible
         names are: vfp, vfpv3, vfpv3-fp16, vfpv3-d16,
         vfpv3-d16-fp16, vfpv3xd, vfpv3xd-fp16, neon, neon-fp16,
         vfpv4, vfpv4-d16, fpv4-sp-d16, neon-vfpv4, fp-armv8,
         neon-fp-armv8, and crypto-neon-fp-armv8.

         If -msoft-float is specified this specifies the format
         of floating-point values.

         If the selected floating-point hardware includes the
         NEON extension (e.g. -mfpu=neon), note that floating-
         point operations are not generated by GCC's auto-
         vectorization pass unless -funsafe-math-optimizations is
         also specified.  This is because NEON hardware does not
         fully implement the IEEE 754 standard for floating-point
         arithmetic (in particular denormal values are treated as
         zero), so the use of NEON instructions may lead to a
         loss of precision.

     -mfp16-format=name
         Specify the format of the "__fp16" half-precision
         floating-point type.  Permissible names are none, ieee,
         and alternative; the default is none, in which case the
         "__fp16" type is not defined.

     -mstructure-size-boundary=n
         The sizes of all structures and unions are rounded up to
         a multiple of the number of bits set by this option.
         Permissible values are 8, 32 and 64.  The default value
         varies for different toolchains.  For the COFF targeted
         toolchain the default value is 8.  A value of 64 is only
         allowed if the underlying ABI supports it.

         Specifying a larger number can produce faster, more
         efficient code, but can also increase the size of the
         program.  Different values are potentially incompatible.
         Code compiled with one value cannot necessarily expect
         to work with code or libraries compiled with another
         value, if they exchange information using structures or
         unions.

     -mabort-on-noreturn
         Generate a call to the function "abort" at the end of a
         "noreturn" function.  It is executed if the function
         tries to return.

     -mlong-calls
     -mno-long-calls
         Tells the compiler to perform function calls by first
         loading the address of the function into a register and
         then performing a subroutine call on this register.
         This switch is needed if the target function lies
         outside of the 64-megabyte addressing range of the
         offset-based version of subroutine call instruction.

         Even if this switch is enabled, not all function calls
         are turned into long calls.  The heuristic is that
         static functions, functions that have the short-call
         attribute, functions that are inside the scope of a
         #pragma no_long_calls directive, and functions whose
         definitions have already been compiled within the
         current compilation unit are not turned into long calls.
         The exceptions to this rule are that weak function
         definitions, functions with the long-call attribute or
         the section attribute, and functions that are within the
         scope of a #pragma long_calls directive are always
         turned into long calls.

         This feature is not enabled by default.  Specifying
         -mno-long-calls restores the default behavior, as does
         placing the function calls within the scope of a #pragma
         long_calls_off directive.  Note these switches have no
         effect on how the compiler generates code to handle
         function calls via function pointers.

     -msingle-pic-base
         Treat the register used for PIC addressing as read-only,
         rather than loading it in the prologue for each
         function.  The runtime system is responsible for
         initializing this register with an appropriate value
         before execution begins.

     -mpic-register=reg
         Specify the register to be used for PIC addressing.  The
         default is R10 unless stack-checking is enabled, when R9
         is used.

     -mpoke-function-name
         Write the name of each function into the text section,
         directly preceding the function prologue.  The generated
         code is similar to this:

                      t0
                          .ascii "arm_poke_function_name", 0
                          .align
                      t1
                          .word 0xff000000 + (t1 - t0)
                      arm_poke_function_name
                          mov     ip, sp
                          stmfd   sp!, {fp, ip, lr, pc}
                          sub     fp, ip, #4

         When performing a stack backtrace, code can inspect the
         value of "pc" stored at "fp + 0".  If the trace function
         then looks at location "pc - 12" and the top 8 bits are
         set, then we know that there is a function name embedded
         immediately preceding this location and has length
         "((pc[-3]) & 0xff000000)".

     -mthumb
     -marm
         Select between generating code that executes in ARM and
         Thumb states.  The default for most configurations is to
         generate code that executes in ARM state, but the
         default can be changed by configuring GCC with the
         --with-mode=state configure option.

     -mtpcs-frame
         Generate a stack frame that is compliant with the Thumb
         Procedure Call Standard for all non-leaf functions.  (A
         leaf function is one that does not call any other
         functions.)  The default is -mno-tpcs-frame.

     -mtpcs-leaf-frame
         Generate a stack frame that is compliant with the Thumb
         Procedure Call Standard for all leaf functions.  (A leaf
         function is one that does not call any other functions.)

         The default is -mno-apcs-leaf-frame.

     -mcallee-super-interworking
         Gives all externally visible functions in the file being
         compiled an ARM instruction set header which switches to
         Thumb mode before executing the rest of the function.
         This allows these functions to be called from non-
         interworking code.  This option is not valid in AAPCS
         configurations because interworking is enabled by
         default.

     -mcaller-super-interworking
         Allows calls via function pointers (including virtual
         functions) to execute correctly regardless of whether
         the target code has been compiled for interworking or
         not.  There is a small overhead in the cost of executing
         a function pointer if this option is enabled.  This
         option is not valid in AAPCS configurations because
         interworking is enabled by default.

     -mtp=name
         Specify the access model for the thread local storage
         pointer.  The valid models are soft, which generates
         calls to "__aeabi_read_tp", cp15, which fetches the
         thread pointer from "cp15" directly (supported in the
         arm6k architecture), and auto, which uses the best
         available method for the selected processor.  The
         default setting is auto.

     -mtls-dialect=dialect
         Specify the dialect to use for accessing thread local
         storage.  Two dialects are supported---gnu and gnu2.
         The gnu dialect selects the original GNU scheme for
         supporting local and global dynamic TLS models.  The
         gnu2 dialect selects the GNU descriptor scheme, which
         provides better performance for shared libraries.  The
         GNU descriptor scheme is compatible with the original
         scheme, but does require new assembler, linker and
         library support.  Initial and local exec TLS models are
         unaffected by this option and always use the original
         scheme.

     -mword-relocations
         Only generate absolute relocations on word-sized values
         (i.e. R_ARM_ABS32).  This is enabled by default on
         targets (uClinux, SymbianOS) where the runtime loader
         imposes this restriction, and when -fpic or -fPIC is
         specified.

     -mfix-cortex-m3-ldrd
         Some Cortex-M3 cores can cause data corruption when
         "ldrd" instructions with overlapping destination and
         base registers are used.  This option avoids generating
         these instructions.  This option is enabled by default
         when -mcpu=cortex-m3 is specified.

     -munaligned-access
     -mno-unaligned-access
         Enables (or disables) reading and writing of 16- and 32-
         bit values from addresses that are not 16- or 32- bit
         aligned.  By default unaligned access is disabled for
         all pre-ARMv6 and all ARMv6-M architectures, and enabled
         for all other architectures.  If unaligned access is not
         enabled then words in packed data structures will be
         accessed a byte at a time.

         The ARM attribute "Tag_CPU_unaligned_access" will be set
         in the generated object file to either true or false,
         depending upon the setting of this option.  If unaligned
         access is enabled then the preprocessor symbol
         "__ARM_FEATURE_UNALIGNED" will also be defined.

     AVR Options

     These options are defined for AVR implementations:

     -mmcu=mcu
         Specify Atmel AVR instruction set architectures (ISA) or
         MCU type.

         The default for this option is@tie{}"avr2".

         GCC supports the following AVR devices and ISAs:

         "avr2"
             "Classic" devices with up to 8@tie{}KiB of program
             memory.  mcu@tie{}= "attiny22", "attiny26",
             "at90c8534", "at90s2313", "at90s2323", "at90s2333",
             "at90s2343", "at90s4414", "at90s4433", "at90s4434",
             "at90s8515", "at90s8535".

         "avr25"
             "Classic" devices with up to 8@tie{}KiB of program
             memory and with the "MOVW" instruction.  mcu@tie{}=
             "ata5272", "ata6289", "attiny13", "attiny13a",
             "attiny2313", "attiny2313a", "attiny24",
             "attiny24a", "attiny25", "attiny261", "attiny261a",
             "attiny43u", "attiny4313", "attiny44", "attiny44a",
             "attiny45", "attiny461", "attiny461a", "attiny48",
             "attiny84", "attiny84a", "attiny85", "attiny861",
             "attiny861a", "attiny87", "attiny88", "at86rf401".

         "avr3"
             "Classic" devices with 16@tie{}KiB up to 64@tie{}KiB
             of  program memory.  mcu@tie{}= "at43usb355",
             "at76c711".

         "avr31"
             "Classic" devices with 128@tie{}KiB of program
             memory.  mcu@tie{}= "atmega103", "at43usb320".

         "avr35"
             "Classic" devices with 16@tie{}KiB up to 64@tie{}KiB
             of program memory and with the "MOVW" instruction.
             mcu@tie{}= "ata5505", "atmega16u2", "atmega32u2",
             "atmega8u2", "attiny1634", "attiny167",
             "at90usb162", "at90usb82".

         "avr4"
             "Enhanced" devices with up to 8@tie{}KiB of program
             memory.  mcu@tie{}= "ata6285", "ata6286",
             "atmega48", "atmega48a", "atmega48p", "atmega48pa",
             "atmega8", "atmega8a", "atmega8hva", "atmega8515",
             "atmega8535", "atmega88", "atmega88a", "atmega88p",
             "atmega88pa", "at90pwm1", "at90pwm2", "at90pwm2b",
             "at90pwm3", "at90pwm3b", "at90pwm81".

         "avr5"
             "Enhanced" devices with 16@tie{}KiB up to
             64@tie{}KiB of program memory.  mcu@tie{}=
             "ata5790", "ata5790n", "ata5795", "atmega16",
             "atmega16a", "atmega16hva", "atmega16hva2",
             "atmega16hvb", "atmega16hvbrevb", "atmega16m1",
             "atmega16u4", "atmega161", "atmega162", "atmega163",
             "atmega164a", "atmega164p", "atmega164pa",
             "atmega165", "atmega165a", "atmega165p",
             "atmega165pa", "atmega168", "atmega168a",
             "atmega168p", "atmega168pa", "atmega169",
             "atmega169a", "atmega169p", "atmega169pa",
             "atmega26hvg", "atmega32", "atmega32a",
             "atmega32c1", "atmega32hvb", "atmega32hvbrevb",
             "atmega32m1", "atmega32u4", "atmega32u6",
             "atmega323", "atmega324a", "atmega324p",
             "atmega324pa", "atmega325", "atmega325a",
             "atmega325p", "atmega3250", "atmega3250a",
             "atmega3250p", "atmega3250pa", "atmega328",
             "atmega328p", "atmega329", "atmega329a",
             "atmega329p", "atmega329pa", "atmega3290",
             "atmega3290a", "atmega3290p", "atmega3290pa",
             "atmega406", "atmega48hvf", "atmega64", "atmega64a",
             "atmega64c1", "atmega64hve", "atmega64m1",
             "atmega64rfa2", "atmega64rfr2", "atmega640",
             "atmega644", "atmega644a", "atmega644p",
             "atmega644pa", "atmega645", "atmega645a",
             "atmega645p", "atmega6450", "atmega6450a",
             "atmega6450p", "atmega649", "atmega649a",
             "atmega649p", "atmega6490", "atmega6490a",
             "atmega6490p", "at90can32", "at90can64",
             "at90pwm161", "at90pwm216", "at90pwm316",
             "at90scr100", "at90usb646", "at90usb647", "at94k",
             "m3000".

         "avr51"
             "Enhanced" devices with 128@tie{}KiB of program
             memory.  mcu@tie{}= "atmega128", "atmega128a",
             "atmega128rfa1", "atmega1280", "atmega1281",
             "atmega1284", "atmega1284p", "at90can128",
             "at90usb1286", "at90usb1287".

         "avr6"
             "Enhanced" devices with 3-byte PC, i.e. with more
             than 128@tie{}KiB of program memory.  mcu@tie{}=
             "atmega2560", "atmega2561".

         "avrxmega2"
             "XMEGA" devices with more than 8@tie{}KiB and up to
             64@tie{}KiB of program memory.  mcu@tie{}=
             "atmxt112sl", "atmxt224", "atmxt224e", "atmxt336s",
             "atxmega16a4", "atxmega16a4u", "atxmega16c4",
             "atxmega16d4", "atxmega16x1", "atxmega32a4",
             "atxmega32a4u", "atxmega32c4", "atxmega32d4",
             "atxmega32e5", "atxmega32x1".

         "avrxmega4"
             "XMEGA" devices with more than 64@tie{}KiB and up to
             128@tie{}KiB of program memory.  mcu@tie{}=
             "atxmega64a3", "atxmega64a3u", "atxmega64a4u",
             "atxmega64b1", "atxmega64b3", "atxmega64c3",
             "atxmega64d3", "atxmega64d4".

         "avrxmega5"
             "XMEGA" devices with more than 64@tie{}KiB and up to
             128@tie{}KiB of program memory and more than
             64@tie{}KiB of RAM.  mcu@tie{}= "atxmega64a1",
             "atxmega64a1u".

         "avrxmega6"
             "XMEGA" devices with more than 128@tie{}KiB of
             program memory.  mcu@tie{}= "atmxt540s",
             "atmxt540sreva", "atxmega128a3", "atxmega128a3u",
             "atxmega128b1", "atxmega128b3", "atxmega128c3",
             "atxmega128d3", "atxmega128d4", "atxmega192a3",
             "atxmega192a3u", "atxmega192c3", "atxmega192d3",
             "atxmega256a3", "atxmega256a3b", "atxmega256a3bu",
             "atxmega256a3u", "atxmega256c3", "atxmega256d3",
             "atxmega384c3", "atxmega384d3".

         "avrxmega7"

             "XMEGA" devices with more than 128@tie{}KiB of
             program memory and more than 64@tie{}KiB of RAM.
             mcu@tie{}= "atxmega128a1", "atxmega128a1u",
             "atxmega128a4u".

         "avr1"
             This ISA is implemented by the minimal AVR core and
             supported for assembler only.  mcu@tie{}=
             "attiny11", "attiny12", "attiny15", "attiny28",
             "at90s1200".

     -maccumulate-args
         Accumulate outgoing function arguments and
         acquire/release the needed stack space for outgoing
         function arguments once in function prologue/epilogue.
         Without this option, outgoing arguments are pushed
         before calling a function and popped afterwards.

         Popping the arguments after the function call can be
         expensive on AVR so that accumulating the stack space
         might lead to smaller executables because arguments need
         not to be removed from the stack after such a function
         call.

         This option can lead to reduced code size for functions
         that perform several calls to functions that get their
         arguments on the stack like calls to printf-like
         functions.

     -mbranch-cost=cost
         Set the branch costs for conditional branch instructions
         to cost.  Reasonable values for cost are small, non-
         negative integers. The default branch cost is 0.

     -mcall-prologues
         Functions prologues/epilogues are expanded as calls to
         appropriate subroutines.  Code size is smaller.

     -mint8
         Assume "int" to be 8-bit integer.  This affects the
         sizes of all types: a "char" is 1 byte, an "int" is 1
         byte, a "long" is 2 bytes, and "long long" is 4 bytes.
         Please note that this option does not conform to the C
         standards, but it results in smaller code size.

     -mno-interrupts
         Generated code is not compatible with hardware
         interrupts.  Code size is smaller.

     -mrelax
         Try to replace "CALL" resp. "JMP" instruction by the
         shorter "RCALL" resp. "RJMP" instruction if applicable.

         Setting "-mrelax" just adds the "--relax" option to the
         linker command line when the linker is called.

         Jump relaxing is performed by the linker because jump
         offsets are not known before code is located. Therefore,
         the assembler code generated by the compiler is the
         same, but the instructions in the executable may differ
         from instructions in the assembler code.

         Relaxing must be turned on if linker stubs are needed,
         see the section on "EIND" and linker stubs below.

     -msp8
         Treat the stack pointer register as an 8-bit register,
         i.e. assume the high byte of the stack pointer is zero.
         In general, you don't need to set this option by hand.

         This option is used internally by the compiler to select
         and build multilibs for architectures "avr2" and
         "avr25".  These architectures mix devices with and
         without "SPH".  For any setting other than "-mmcu=avr2"
         or "-mmcu=avr25" the compiler driver will add or remove
         this option from the compiler proper's command line,
         because the compiler then knows if the device or
         architecture has an 8-bit stack pointer and thus no
         "SPH" register or not.

     -mstrict-X
         Use address register "X" in a way proposed by the
         hardware.  This means that "X" is only used in indirect,
         post-increment or pre-decrement addressing.

         Without this option, the "X" register may be used in the
         same way as "Y" or "Z" which then is emulated by
         additional instructions. For example, loading a value
         with "X+const" addressing with a small non-negative
         "const < 64" to a register Rn is performed as

                 adiw r26, const   ; X += const
                 ld   <Rn>, X        ; <Rn> = *X
                 sbiw r26, const   ; X -= const

     -mtiny-stack
         Only change the lower 8@tie{}bits of the stack pointer.

     -Waddr-space-convert
         Warn about conversions between address spaces in the
         case where the resulting address space is not contained
         in the incoming address space.

     "EIND" and Devices with more than 128 Ki Bytes of Flash

     Pointers in the implementation are 16@tie{}bits wide.  The
     address of a function or label is represented as word
     address so that indirect jumps and calls can target any code
     address in the range of 64@tie{}Ki words.

     In order to facilitate indirect jump on devices with more
     than 128@tie{}Ki bytes of program memory space, there is a
     special function register called "EIND" that serves as most
     significant part of the target address when "EICALL" or
     "EIJMP" instructions are used.

     Indirect jumps and calls on these devices are handled as
     follows by the compiler and are subject to some limitations:

     *   The compiler never sets "EIND".

     *   The compiler uses "EIND" implicitely in "EICALL"/"EIJMP"
         instructions or might read "EIND" directly in order to
         emulate an indirect call/jump by means of a "RET"
         instruction.

     *   The compiler assumes that "EIND" never changes during
         the startup code or during the application. In
         particular, "EIND" is not saved/restored in function or
         interrupt service routine prologue/epilogue.

     *   For indirect calls to functions and computed goto, the
         linker generates stubs. Stubs are jump pads sometimes
         also called trampolines. Thus, the indirect call/jump
         jumps to such a stub.  The stub contains a direct jump
         to the desired address.

     *   Linker relaxation must be turned on so that the linker
         will generate the stubs correctly an all situaltion. See
         the compiler option "-mrelax" and the linler option
         "--relax".  There are corner cases where the linker is
         supposed to generate stubs but aborts without relaxation
         and without a helpful error message.

     *   The default linker script is arranged for code with
         "EIND = 0".  If code is supposed to work for a setup
         with "EIND != 0", a custom linker script has to be used
         in order to place the sections whose name start with
         ".trampolines" into the segment where "EIND" points to.

     *   The startup code from libgcc never sets "EIND".  Notice
         that startup code is a blend of code from libgcc and
         AVR-LibC.  For the impact of AVR-LibC on "EIND", see the
         AVR-LibC user manual
         ("http://nongnu.org/avr-libc/user-manual/").

     *   It is legitimate for user-specific startup code to set

         up "EIND" early, for example by means of initialization
         code located in section ".init3". Such code runs prior
         to general startup code that initializes RAM and calls
         constructors, but after the bit of startup code from
         AVR-LibC that sets "EIND" to the segment where the
         vector table is located.

                 #include <avr/io.h>

                 static void
                 __attribute__((section(".init3"),naked,used,no_instrument_function))
                 init3_set_eind (void)
                 {
                   __asm volatile ("ldi r24,pm_hh8(__trampolines_start)\n\t"
                                   "out %i0,r24" :: "n" (&EIND) : "r24","memory");
                 }

         The "__trampolines_start" symbol is defined in the
         linker script.

     *   Stubs are generated automatically by the linker if the
         following two conditions are met:

        modifier>
         -<The address of a label is taken by means of the "gs"
             (short for generate stubs) like so:

                     LDI r24, lo8(gs(<func>))
                     LDI r25, hi8(gs(<func>))

         -<The final location of that label is in a code segment>
             outside the segment where the stubs are located.

     *   The compiler emits such "gs" modifiers for code labels
         in the following situations:

         -<Taking address of a function or code label.>
         -<Computed goto.>
         -<If prologue-
             save function is used, see -mcall-prologues>
             command-line option.

        dispatch>
         -<Switch/case dispatch tables. If you do not want such
             tables you can specify the -fno-jump-tables
             command-line option.

        startup/shutdown.>
         -<C and C++ constructors/destructors called during
         -<If the tools hit a "gs()" modifier explained above.>
     *   Jumping to non-symbolic addresses like so is not
         supported:

                 int main (void)
                 {
                     /* Call function at word address 0x2 */
                     return ((int(*)(void)) 0x2)();
                 }

         Instead, a stub has to be set up, i.e. the function has
         to be called through a symbol ("func_4" in the example):

                 int main (void)
                 {
                     extern int func_4 (void);

                     /* Call function at byte address 0x4 */
                     return func_4();
                 }

         and the application be linked with
         "-Wl,--defsym,func_4=0x4".  Alternatively, "func_4" can
         be defined in the linker script.

     Handling of the "RAMPD", "RAMPX", "RAMPY" and "RAMPZ"
     Special Function Registers

     Some AVR devices support memories larger than the
     64@tie{}KiB range that can be accessed with 16-bit pointers.
     To access memory locations outside this 64@tie{}KiB range,
     the contentent of a "RAMP" register is used as high part of
     the address:  The "X", "Y", "Z" address register is
     concatenated with the "RAMPX", "RAMPY", "RAMPZ" special
     function register, respectively, to get a wide address.
     Similarly, "RAMPD" is used together with direct addressing.

     *   The startup code initializes the "RAMP" special function
         registers with zero.

     *   If a AVR Named Address Spaces,named address space other
         than generic or "__flash" is used, then "RAMPZ" is set
         as needed before the operation.

     *   If the device supports RAM larger than 64@tie{KiB} and
         the compiler needs to change "RAMPZ" to accomplish an
         operation, "RAMPZ" is reset to zero after the operation.

     *   If the device comes with a specific "RAMP" register, the
         ISR prologue/epilogue saves/restores that SFR and
         initializes it with zero in case the ISR code might
         (implicitly) use it.

     *   RAM larger than 64@tie{KiB} is not supported by GCC for
         AVR targets.  If you use inline assembler to read from
         locations outside the 16-bit address range and change
         one of the "RAMP" registers, you must reset it to zero
         after the access.

     AVR Built-in Macros

     GCC defines several built-in macros so that the user code
     can test for the presence or absence of features.  Almost
     any of the following built-in macros are deduced from device
     capabilities and thus triggered by the "-mmcu=" command-line
     option.

     For even more AVR-specific built-in macros see AVR Named
     Address Spaces and AVR Built-in Functions.

     "__AVR_ARCH__"
         Build-in macro that resolves to a decimal number that
         identifies the architecture and depends on the
         "-mmcu=mcu" option.  Possible values are:

         2, 25, 3, 31, 35, 4, 5, 51, 6, 102, 104, 105, 106, 107

         for mcu="avr2", "avr25", "avr3", "avr31", "avr35",
         "avr4", "avr5", "avr51", "avr6", "avrxmega2",
         "avrxmega4", "avrxmega5", "avrxmega6", "avrxmega7",
         respectively.  If mcu specifies a device, this built-in
         macro is set accordingly. For example, with
         "-mmcu=atmega8" the macro will be defined to 4.

     "__AVR_Device__"
         Setting "-mmcu=device" defines this built-in macro which
         reflects the device's name. For example, "-mmcu=atmega8"
         defines the built-in macro "__AVR_ATmega8__",
         "-mmcu=attiny261a" defines "__AVR_ATtiny261A__", etc.

         The built-in macros' names follow the scheme
         "__AVR_Device__" where Device is the device name as from
         the AVR user manual. The difference between Device in
         the built-in macro and device in "-mmcu=device" is that
         the latter is always lowercase.

         If device is not a device but only a core architecture
         like "avr51", this macro will not be defined.

     "__AVR_XMEGA__"
         The device / architecture belongs to the XMEGA family of
         devices.

     "__AVR_HAVE_ELPM__"
         The device has the the "ELPM" instruction.

     "__AVR_HAVE_ELPMX__"
         The device has the "ELPM Rn,Z" and "ELPM Rn,Z+"
         instructions.

     "__AVR_HAVE_MOVW__"
         The device has the "MOVW" instruction to perform 16-bit
         register-register moves.

     "__AVR_HAVE_LPMX__"
         The device has the "LPM Rn,Z" and "LPM Rn,Z+"
         instructions.

     "__AVR_HAVE_MUL__"
         The device has a hardware multiplier.

     "__AVR_HAVE_JMP_CALL__"
         The device has the "JMP" and "CALL" instructions.  This
         is the case for devices with at least 16@tie{}KiB of
         program memory.

     "__AVR_HAVE_EIJMP_EICALL__"
     "__AVR_3_BYTE_PC__"
         The device has the "EIJMP" and "EICALL" instructions.
         This is the case for devices with more than 128@tie{}KiB
         of program memory.  This also means that the program
         counter (PC) is 3@tie{}bytes wide.

     "__AVR_2_BYTE_PC__"
         The program counter (PC) is 2@tie{}bytes wide. This is
         the case for devices with up to 128@tie{}KiB of program
         memory.

     "__AVR_HAVE_8BIT_SP__"
     "__AVR_HAVE_16BIT_SP__"
         The stack pointer (SP) register is treated as 8-bit
         respectively 16-bit register by the compiler.  The
         definition of these macros is affected by
         "-mtiny-stack".

     "__AVR_HAVE_SPH__"
     "__AVR_SP8__"
         The device has the SPH (high part of stack pointer)
         special function register or has an 8-bit stack pointer,
         respectively.  The definition of these macros is
         affected by "-mmcu=" and in the cases of "-mmcu=avr2"
         and "-mmcu=avr25" also by "-msp8".

     "__AVR_HAVE_RAMPD__"
     "__AVR_HAVE_RAMPX__"
     "__AVR_HAVE_RAMPY__"
     "__AVR_HAVE_RAMPZ__"
         The device has the "RAMPD", "RAMPX", "RAMPY", "RAMPZ"
         special function register, respectively.

     "__NO_INTERRUPTS__"
         This macro reflects the "-mno-interrupts" command line
         option.

     "__AVR_ERRATA_SKIP__"
     "__AVR_ERRATA_SKIP_JMP_CALL__"
         Some AVR devices (AT90S8515, ATmega103) must not skip
         32-bit instructions because of a hardware erratum.  Skip
         instructions are "SBRS", "SBRC", "SBIS", "SBIC" and
         "CPSE".  The second macro is only defined if
         "__AVR_HAVE_JMP_CALL__" is also set.

     "__AVR_SFR_OFFSET__=offset"
         Instructions that can address I/O special function
         registers directly like "IN", "OUT", "SBI", etc. may use
         a different address as if addressed by an instruction to
         access RAM like "LD" or "STS". This offset depends on
         the device architecture and has to be subtracted from
         the RAM address in order to get the respective
         I/O@tie{}address.

     "__WITH_AVRLIBC__"
         The compiler is configured to be used together with
         AVR-Libc.  See the "--with-avrlibc" configure option.

     Blackfin Options

     -mcpu=cpu[-sirevision]
         Specifies the name of the target Blackfin processor.
         Currently, cpu can be one of bf512, bf514, bf516, bf518,
         bf522, bf523, bf524, bf525, bf526, bf527, bf531, bf532,
         bf533, bf534, bf536, bf537, bf538, bf539, bf542, bf544,
         bf547, bf548, bf549, bf542m, bf544m, bf547m, bf548m,
         bf549m, bf561, bf592.

         The optional sirevision specifies the silicon revision
         of the target Blackfin processor.  Any workarounds
         available for the targeted silicon revision are enabled.
         If sirevision is none, no workarounds are enabled.  If
         sirevision is any, all workarounds for the targeted
         processor are enabled.  The "__SILICON_REVISION__" macro
         is defined to two hexadecimal digits representing the
         major and minor numbers in the silicon revision.  If
         sirevision is none, the "__SILICON_REVISION__" is not
         defined.  If sirevision is any, the
         "__SILICON_REVISION__" is defined to be 0xffff.  If this
         optional sirevision is not used, GCC assumes the latest
         known silicon revision of the targeted Blackfin
         processor.

         GCC defines a preprocessor macro for the specified cpu.
         For the bfin-elf toolchain, this option causes the
         hardware BSP provided by libgloss to be linked in if
         -msim is not given.

         Without this option, bf532 is used as the processor by
         default.

         Note that support for bf561 is incomplete.  For bf561,
         only the preprocessor macro is defined.

     -msim
         Specifies that the program will be run on the simulator.
         This causes the simulator BSP provided by libgloss to be
         linked in.  This option has effect only for bfin-elf
         toolchain.  Certain other options, such as
         -mid-shared-library and -mfdpic, imply -msim.

     -momit-leaf-frame-pointer
         Don't keep the frame pointer in a register for leaf
         functions.  This avoids the instructions to save, set up
         and restore frame pointers and makes an extra register
         available in leaf functions.  The option
         -fomit-frame-pointer removes the frame pointer for all
         functions, which might make debugging harder.

     -mspecld-anomaly
         When enabled, the compiler ensures that the generated
         code does not contain speculative loads after jump
         instructions. If this option is used,
         "__WORKAROUND_SPECULATIVE_LOADS" is defined.

     -mno-specld-anomaly
         Don't generate extra code to prevent speculative loads
         from occurring.

     -mcsync-anomaly
         When enabled, the compiler ensures that the generated
         code does not contain CSYNC or SSYNC instructions too
         soon after conditional branches.  If this option is
         used, "__WORKAROUND_SPECULATIVE_SYNCS" is defined.

     -mno-csync-anomaly
         Don't generate extra code to prevent CSYNC or SSYNC
         instructions from occurring too soon after a conditional
         branch.

     -mlow-64k
         When enabled, the compiler is free to take advantage of
         the knowledge that the entire program fits into the low
         64k of memory.

     -mno-low-64k
         Assume that the program is arbitrarily large.  This is
         the default.

     -mstack-check-l1
         Do stack checking using information placed into L1
         scratchpad memory by the uClinux kernel.

     -mid-shared-library
         Generate code that supports shared libraries via the
         library ID method.  This allows for execute in place and
         shared libraries in an environment without virtual
         memory management.  This option implies -fPIC.  With a
         bfin-elf target, this option implies -msim.

     -mno-id-shared-library
         Generate code that doesn't assume ID-based shared
         libraries are being used.  This is the default.

     -mleaf-id-shared-library
         Generate code that supports shared libraries via the
         library ID method, but assumes that this library or
         executable won't link against any other ID shared
         libraries.  That allows the compiler to use faster code
         for jumps and calls.

     -mno-leaf-id-shared-library
         Do not assume that the code being compiled won't link
         against any ID shared libraries.  Slower code is
         generated for jump and call insns.

     -mshared-library-id=n
         Specifies the identification number of the ID-based
         shared library being compiled.  Specifying a value of 0
         generates more compact code; specifying other values
         forces the allocation of that number to the current
         library but is no more space- or time-efficient than
         omitting this option.

     -msep-data
         Generate code that allows the data segment to be located
         in a different area of memory from the text segment.
         This allows for execute in place in an environment
         without virtual memory management by eliminating
         relocations against the text section.

     -mno-sep-data
         Generate code that assumes that the data segment follows
         the text segment.  This is the default.

     -mlong-calls
     -mno-long-calls
         Tells the compiler to perform function calls by first
         loading the address of the function into a register and
         then performing a subroutine call on this register.
         This switch is needed if the target function lies
         outside of the 24-bit addressing range of the offset-
         based version of subroutine call instruction.

         This feature is not enabled by default.  Specifying
         -mno-long-calls restores the default behavior.  Note
         these switches have no effect on how the compiler
         generates code to handle function calls via function
         pointers.

     -mfast-fp
         Link with the fast floating-point library. This library
         relaxes some of the IEEE floating-point standard's rules
         for checking inputs against Not-a-Number (NAN), in the
         interest of performance.

     -minline-plt
         Enable inlining of PLT entries in function calls to
         functions that are not known to bind locally.  It has no
         effect without -mfdpic.

     -mmulticore
         Build a standalone application for multicore Blackfin
         processors. This option causes proper start files and
         link scripts supporting multicore to be used, and
         defines the macro "__BFIN_MULTICORE". It can only be
         used with -mcpu=bf561[-sirevision].

         This option can be used with -mcorea or -mcoreb, which
         selects the one-application-per-core programming model.
         Without -mcorea or -mcoreb, the
         single-application/dual-core programming model is used.
         In this model, the main function of Core B should be
         named as "coreb_main".

         If this option is not used, the single-core application
         programming model is used.

     -mcorea
         Build a standalone application for Core A of BF561 when
         using the one-application-per-core programming model.
         Proper start files and link scripts are used to support
         Core A, and the macro "__BFIN_COREA" is defined.  This
         option can only be used in conjunction with -mmulticore.

     -mcoreb
         Build a standalone application for Core B of BF561 when
         using the one-application-per-core programming model.
         Proper start files and link scripts are used to support
         Core B, and the macro "__BFIN_COREB" is defined. When
         this option is used, "coreb_main" should be used instead
         of "main". This option can only be used in conjunction
         with -mmulticore.

     -msdram
         Build a standalone application for SDRAM. Proper start
         files and link scripts are used to put the application
         into SDRAM, and the macro "__BFIN_SDRAM" is defined.
         The loader should initialize SDRAM before loading the
         application.

     -micplb
         Assume that ICPLBs are enabled at run time.  This has an
         effect on certain anomaly workarounds.  For Linux
         targets, the default is to assume ICPLBs are enabled;
         for standalone applications the default is off.

     C6X Options

     -march=name
         This specifies the name of the target architecture.  GCC
         uses this name to determine what kind of instructions it
         can emit when generating assembly code.  Permissible
         names are: c62x, c64x, c64x+, c67x, c67x+, c674x.

     -mbig-endian
         Generate code for a big-endian target.

     -mlittle-endian
         Generate code for a little-endian target.  This is the
         default.

     -msim
         Choose startup files and linker script suitable for the
         simulator.

     -msdata=default
         Put small global and static data in the .neardata
         section, which is pointed to by register "B14".  Put
         small uninitialized global and static data in the .bss
         section, which is adjacent to the .neardata section.
         Put small read-only data into the .rodata section.  The
         corresponding sections used for large pieces of data are
         .fardata, .far and .const.

     -msdata=all
         Put all data, not just small objects, into the sections
         reserved for small data, and use addressing relative to
         the "B14" register to access them.

     -msdata=none
         Make no use of the sections reserved for small data, and
         use absolute addresses to access all data.  Put all
         initialized global and static data in the .fardata
         section, and all uninitialized data in the .far section.
         Put all constant data into the .const section.

     CRIS Options

     These options are defined specifically for the CRIS ports.

     -march=architecture-type
     -mcpu=architecture-type
         Generate code for the specified architecture.  The
         choices for architecture-type are v3, v8 and v10 for
         respectively ETRAX 4, ETRAX 100, and ETRAX 100 LX.
         Default is v0 except for cris-axis-linux-gnu, where the
         default is v10.

     -mtune=architecture-type
         Tune to architecture-type everything applicable about
         the generated code, except for the ABI and the set of
         available instructions.  The choices for architecture-
         type are the same as for -march=architecture-type.

     -mmax-stack-frame=n
         Warn when the stack frame of a function exceeds n bytes.

     -metrax4
     -metrax100
         The options -metrax4 and -metrax100 are synonyms for
         -march=v3 and -march=v8 respectively.

     -mmul-bug-workaround
     -mno-mul-bug-workaround
         Work around a bug in the "muls" and "mulu" instructions
         for CPU models where it applies.  This option is active
         by default.

     -mpdebug
         Enable CRIS-specific verbose debug-related information
         in the assembly code.  This option also has the effect
         of turning off the #NO_APP formatted-code indicator to
         the assembler at the beginning of the assembly file.

     -mcc-init
         Do not use condition-code results from previous
         instruction; always emit compare and test instructions
         before use of condition codes.

     -mno-side-effects
         Do not emit instructions with side effects in addressing
         modes other than post-increment.

     -mstack-align
     -mno-stack-align
     -mdata-align
     -mno-data-align
     -mconst-align
     -mno-const-align
         These options (no- options) arrange (eliminate
         arrangements) for the stack frame, individual data and
         constants to be aligned for the maximum single data
         access size for the chosen CPU model.  The default is to
         arrange for 32-bit alignment.  ABI details such as
         structure layout are not affected by these options.

     -m32-bit
     -m16-bit
     -m8-bit
         Similar to the stack- data- and const-align options
         above, these options arrange for stack frame, writable
         data and constants to all be 32-bit, 16-bit or 8-bit
         aligned.  The default is 32-bit alignment.

     -mno-prologue-epilogue
     -mprologue-epilogue
         With -mno-prologue-epilogue, the normal function
         prologue and epilogue which set up the stack frame are
         omitted and no return instructions or return sequences
         are generated in the code.  Use this option only
         together with visual inspection of the compiled code: no
         warnings or errors are generated when call-saved
         registers must be saved, or storage for local variables
         needs to be allocated.

     -mno-gotplt
     -mgotplt
         With -fpic and -fPIC, don't generate (do generate)
         instruction sequences that load addresses for functions
         from the PLT part of the GOT rather than (traditional on
         other architectures) calls to the PLT.  The default is
         -mgotplt.

     -melf
         Legacy no-op option only recognized with the cris-axis-
         elf and cris-axis-linux-gnu targets.

     -mlinux
         Legacy no-op option only recognized with the cris-axis-
         linux-gnu target.

     -sim
         This option, recognized for the cris-axis-elf, arranges
         to link with input-output functions from a simulator
         library.  Code, initialized data and zero-initialized
         data are allocated consecutively.

     -sim2
         Like -sim, but pass linker options to locate initialized
         data at 0x40000000 and zero-initialized data at
         0x80000000.

     CR16 Options

     These options are defined specifically for the CR16 ports.

     -mmac
         Enable the use of multiply-accumulate instructions.
         Disabled by default.

     -mcr16cplus
     -mcr16c
         Generate code for CR16C or CR16C+ architecture. CR16C+
         architecture is default.

     -msim
         Links the library libsim.a which is in compatible with
         simulator. Applicable to ELF compiler only.

     -mint32
         Choose integer type as 32-bit wide.

     -mbit-ops
         Generates "sbit"/"cbit" instructions for bit
         manipulations.

     -mdata-model=model
         Choose a data model. The choices for model are near, far
         or medium. medium is default.  However, far is not valid
         with -mcr16c, as the CR16C architecture does not support
         the far data model.

     Darwin Options

     These options are defined for all architectures running the
     Darwin operating system.

     FSF GCC on Darwin does not create "fat" object files; it
     creates an object file for the single architecture that GCC
     was built to target.  Apple's GCC on Darwin does create
     "fat" files if multiple -arch options are used; it does so
     by running the compiler or linker multiple times and joining
     the results together with lipo.

     The subtype of the file created (like ppc7400 or ppc970 or
     i686) is determined by the flags that specify the ISA that
     GCC is targeting, like -mcpu or -march.  The
     -force_cpusubtype_ALL option can be used to override this.

     The Darwin tools vary in their behavior when presented with
     an ISA mismatch.  The assembler, as, only permits
     instructions to be used that are valid for the subtype of
     the file it is generating, so you cannot put 64-bit
     instructions in a ppc750 object file.  The linker for shared
     libraries, /usr/bin/libtool, fails and prints an error if
     asked to create a shared library with a less restrictive
     subtype than its input files (for instance, trying to put a
     ppc970 object file in a ppc7400 library).  The linker for
     executables, ld, quietly gives the executable the most
     restrictive subtype of any of its input files.

     -Fdir
         Add the framework directory dir to the head of the list
         of directories to be searched for header files.  These
         directories are interleaved with those specified by -I
         options and are scanned in a left-to-right order.

         A framework directory is a directory with frameworks in
         it.  A framework is a directory with a Headers and/or
         PrivateHeaders directory contained directly in it that
         ends in .framework.  The name of a framework is the name
         of this directory excluding the .framework.  Headers
         associated with the framework are found in one of those
         two directories, with Headers being searched first.  A
         subframework is a framework directory that is in a
         framework's Frameworks directory.  Includes of
         subframework headers can only appear in a header of a
         framework that contains the subframework, or in a
         sibling subframework header.  Two subframeworks are
         siblings if they occur in the same framework.  A
         subframework should not have the same name as a
         framework; a warning is issued if this is violated.
         Currently a subframework cannot have subframeworks; in
         the future, the mechanism may be extended to support
         this.  The standard frameworks can be found in
         /System/Library/Frameworks and /Library/Frameworks.  An
         example include looks like "#include
         <Framework/header.h>", where Framework denotes the name
         of the framework and header.h is found in the
         PrivateHeaders or Headers directory.

     -iframeworkdir
         Like -F except the directory is a treated as a system
         directory.  The main difference between this -iframework
         and -F is that with -iframework the compiler does not
         warn about constructs contained within header files
         found via dir.  This option is valid only for the C
         family of languages.

     -gused
         Emit debugging information for symbols that are used.

         For stabs debugging format, this enables
         -feliminate-unused-debug-symbols.  This is by default
         ON.

     -gfull
         Emit debugging information for all symbols and types.

     -mmacosx-version-min=version
         The earliest version of MacOS X that this executable
         will run on is version.  Typical values of version
         include 10.1, 10.2, and 10.3.9.

         If the compiler was built to use the system's headers by
         default, then the default for this option is the system
         version on which the compiler is running, otherwise the
         default is to make choices that are compatible with as
         many systems and code bases as possible.

     -mkernel
         Enable kernel development mode.  The -mkernel option
         sets -static, -fno-common, -fno-cxa-atexit,
         -fno-exceptions, -fno-non-call-exceptions, -fapple-kext,
         -fno-weak and -fno-rtti where applicable.  This mode
         also sets -mno-altivec, -msoft-float, -fno-builtin and
         -mlong-branch for PowerPC targets.

     -mone-byte-bool
         Override the defaults for bool so that sizeof(bool)==1.
         By default sizeof(bool) is 4 when compiling for
         Darwin/PowerPC and 1 when compiling for Darwin/x86, so
         this option has no effect on x86.

         Warning: The -mone-byte-bool switch causes GCC to
         generate code that is not binary compatible with code
         generated without that switch.  Using this switch may
         require recompiling all other modules in a program,
         including system libraries.  Use this switch to conform
         to a non-default data model.

     -mfix-and-continue
     -ffix-and-continue
     -findirect-data
         Generate code suitable for fast turnaround development,
         such as to allow GDB to dynamically load ".o" files into
         already-running programs.  -findirect-data and
         -ffix-and-continue are provided for backwards
         compatibility.

     -all_load
         Loads all members of static archive libraries.  See man
         ld(1) for more information.

     -arch_errors_fatal
         Cause the errors having to do with files that have the
         wrong architecture to be fatal.

     -bind_at_load
         Causes the output file to be marked such that the
         dynamic linker will bind all undefined references when
         the file is loaded or launched.

     -bundle
         Produce a Mach-o bundle format file.  See man ld(1) for
         more information.

     -bundle_loader executable
         This option specifies the executable that will load the
         build output file being linked.  See man ld(1) for more
         information.

     -dynamiclib
         When passed this option, GCC produces a dynamic library
         instead of an executable when linking, using the Darwin
         libtool command.

     -force_cpusubtype_ALL
         This causes GCC's output file to have the ALL subtype,
         instead of one controlled by the -mcpu or -march option.

     -allowable_client  client_name
     -client_name
     -compatibility_version
     -current_version
     -dead_strip
     -dependency-file
     -dylib_file
     -dylinker_install_name
     -dynamic
     -exported_symbols_list
     -filelist
     -flat_namespace
     -force_flat_namespace
     -headerpad_max_install_names
     -image_base
     -init
     -install_name
     -keep_private_externs
     -multi_module
     -multiply_defined
     -multiply_defined_unused
     -noall_load
     -no_dead_strip_inits_and_terms
     -nofixprebinding
     -nomultidefs
     -noprebind
     -noseglinkedit
     -pagezero_size
     -prebind
     -prebind_all_twolevel_modules
     -private_bundle
     -read_only_relocs
     -sectalign
     -sectobjectsymbols
     -whyload
     -seg1addr
     -sectcreate
     -sectobjectsymbols
     -sectorder
     -segaddr
     -segs_read_only_addr
     -segs_read_write_addr
     -seg_addr_table
     -seg_addr_table_filename
     -seglinkedit
     -segprot
     -segs_read_only_addr
     -segs_read_write_addr
     -single_module
     -static
     -sub_library
     -sub_umbrella
     -twolevel_namespace
     -umbrella
     -undefined
     -unexported_symbols_list
     -weak_reference_mismatches
     -whatsloaded
         These options are passed to the Darwin linker.  The
         Darwin linker man page describes them in detail.

     DEC Alpha Options

     These -m options are defined for the DEC Alpha
     implementations:

     -mno-soft-float
     -msoft-float
         Use (do not use) the hardware floating-point
         instructions for floating-point operations.  When
         -msoft-float is specified, functions in libgcc.a are
         used to perform floating-point operations.  Unless they
         are replaced by routines that emulate the floating-point
         operations, or compiled in such a way as to call such
         emulations routines, these routines issue floating-point
         operations.   If you are compiling for an Alpha without
         floating-point operations, you must ensure that the
         library is built so as not to call them.

         Note that Alpha implementations without floating-point
         operations are required to have floating-point
         registers.

     -mfp-reg
     -mno-fp-regs
         Generate code that uses (does not use) the floating-
         point register set.  -mno-fp-regs implies -msoft-float.
         If the floating-point register set is not used,
         floating-point operands are passed in integer registers
         as if they were integers and floating-point results are
         passed in $0 instead of $f0.  This is a non-standard
         calling sequence, so any function with a floating-point
         argument or return value called by code compiled with
         -mno-fp-regs must also be compiled with that option.

         A typical use of this option is building a kernel that
         does not use, and hence need not save and restore, any
         floating-point registers.

     -mieee
         The Alpha architecture implements floating-point
         hardware optimized for maximum performance.  It is
         mostly compliant with the IEEE floating-point standard.
         However, for full compliance, software assistance is
         required.  This option generates code fully IEEE-
         compliant code except that the inexact-flag is not
         maintained (see below).  If this option is turned on,
         the preprocessor macro "_IEEE_FP" is defined during
         compilation.  The resulting code is less efficient but
         is able to correctly support denormalized numbers and
         exceptional IEEE values such as not-a-number and
         plus/minus infinity.  Other Alpha compilers call this
         option -ieee_with_no_inexact.

     -mieee-with-inexact
         This is like -mieee except the generated code also
         maintains the IEEE inexact-flag.  Turning on this option
         causes the generated code to implement fully-compliant
         IEEE math.  In addition to "_IEEE_FP", "_IEEE_FP_EXACT"
         is defined as a preprocessor macro.  On some Alpha
         implementations the resulting code may execute
         significantly slower than the code generated by default.
         Since there is very little code that depends on the
         inexact-flag, you should normally not specify this
         option.  Other Alpha compilers call this option
         -ieee_with_inexact.

     -mfp-trap-mode=trap-mode
         This option controls what floating-point related traps
         are enabled.  Other Alpha compilers call this option
         -fptm trap-mode.  The trap mode can be set to one of
         four values:

         n   This is the default (normal) setting.  The only
             traps that are enabled are the ones that cannot be
             disabled in software (e.g., division by zero trap).

         u   In addition to the traps enabled by n, underflow
             traps are enabled as well.

         su  Like u, but the instructions are marked to be safe
             for software completion (see Alpha architecture
             manual for details).

         sui Like su, but inexact traps are enabled as well.

     -mfp-rounding-mode=rounding-mode
         Selects the IEEE rounding mode.  Other Alpha compilers
         call this option -fprm rounding-mode.  The rounding-mode
         can be one of:

         n   Normal IEEE rounding mode.  Floating-point numbers
             are rounded towards the nearest machine number or
             towards the even machine number in case of a tie.

         m   Round towards minus infinity.

         c   Chopped rounding mode.  Floating-point numbers are
             rounded towards zero.

         d   Dynamic rounding mode.  A field in the floating-
             point control register (fpcr, see Alpha architecture
             reference manual) controls the rounding mode in
             effect.  The C library initializes this register for
             rounding towards plus infinity.  Thus, unless your
             program modifies the fpcr, d corresponds to round
             towards plus infinity.

     -mtrap-precision=trap-precision
         In the Alpha architecture, floating-point traps are
         imprecise.  This means without software assistance it is
         impossible to recover from a floating trap and program
         execution normally needs to be terminated.  GCC can
         generate code that can assist operating system trap
         handlers in determining the exact location that caused a
         floating-point trap.  Depending on the requirements of
         an application, different levels of precisions can be
         selected:

         p   Program precision.  This option is the default and
             means a trap handler can only identify which program
             caused a floating-point exception.

         f   Function precision.  The trap handler can determine
             the function that caused a floating-point exception.

         i   Instruction precision.  The trap handler can
             determine the exact instruction that caused a
             floating-point exception.

         Other Alpha compilers provide the equivalent options
         called -scope_safe and -resumption_safe.

     -mieee-conformant
         This option marks the generated code as IEEE conformant.
         You must not use this option unless you also specify
         -mtrap-precision=i and either -mfp-trap-mode=su or
         -mfp-trap-mode=sui.  Its only effect is to emit the line
         .eflag 48 in the function prologue of the generated
         assembly file.

     -mbuild-constants
         Normally GCC examines a 32- or 64-bit integer constant
         to see if it can construct it from smaller constants in
         two or three instructions.  If it cannot, it outputs the
         constant as a literal and generates code to load it from
         the data segment at run time.

         Use this option to require GCC to construct all integer
         constants using code, even if it takes more instructions
         (the maximum is six).

         You typically use this option to build a shared library
         dynamic loader.  Itself a shared library, it must
         relocate itself in memory before it can find the
         variables and constants in its own data segment.

     -mbwx
     -mno-bwx
     -mcix
     -mno-cix
     -mfix
     -mno-fix
     -mmax
     -mno-max
         Indicate whether GCC should generate code to use the
         optional BWX, CIX, FIX and MAX instruction sets.  The
         default is to use the instruction sets supported by the
         CPU type specified via -mcpu= option or that of the CPU
         on which GCC was built if none is specified.

     -mfloat-vax
     -mfloat-ieee

         Generate code that uses (does not use) VAX F and G
         floating-point arithmetic instead of IEEE single and
         double precision.

     -mexplicit-relocs
     -mno-explicit-relocs
         Older Alpha assemblers provided no way to generate
         symbol relocations except via assembler macros.  Use of
         these macros does not allow optimal instruction
         scheduling.  GNU binutils as of version 2.12 supports a
         new syntax that allows the compiler to explicitly mark
         which relocations should apply to which instructions.
         This option is mostly useful for debugging, as GCC
         detects the capabilities of the assembler when it is
         built and sets the default accordingly.

     -msmall-data
     -mlarge-data
         When -mexplicit-relocs is in effect, static data is
         accessed via gp-relative relocations.  When -msmall-data
         is used, objects 8 bytes long or smaller are placed in a
         small data area (the ".sdata" and ".sbss" sections) and
         are accessed via 16-bit relocations off of the $gp
         register.  This limits the size of the small data area
         to 64KB, but allows the variables to be directly
         accessed via a single instruction.

         The default is -mlarge-data.  With this option the data
         area is limited to just below 2GB.  Programs that
         require more than 2GB of data must use "malloc" or
         "mmap" to allocate the data in the heap instead of in
         the program's data segment.

         When generating code for shared libraries, -fpic implies
         -msmall-data and -fPIC implies -mlarge-data.

     -msmall-text
     -mlarge-text
         When -msmall-text is used, the compiler assumes that the
         code of the entire program (or shared library) fits in
         4MB, and is thus reachable with a branch instruction.
         When -msmall-data is used, the compiler can assume that
         all local symbols share the same $gp value, and thus
         reduce the number of instructions required for a
         function call from 4 to 1.

         The default is -mlarge-text.

     -mcpu=cpu_type
         Set the instruction set and instruction scheduling
         parameters for machine type cpu_type.  You can specify
         either the EV style name or the corresponding chip
         number.  GCC supports scheduling parameters for the EV4,
         EV5 and EV6 family of processors and chooses the default
         values for the instruction set from the processor you
         specify.  If you do not specify a processor type, GCC
         defaults to the processor on which the compiler was
         built.

         Supported values for cpu_type are

         ev4
         ev45
         21064
             Schedules as an EV4 and has no instruction set
             extensions.

         ev5
         21164
             Schedules as an EV5 and has no instruction set
             extensions.

         ev56
         21164a
             Schedules as an EV5 and supports the BWX extension.

         pca56
         21164pc
         21164PC
             Schedules as an EV5 and supports the BWX and MAX
             extensions.

         ev6
         21264
             Schedules as an EV6 and supports the BWX, FIX, and
             MAX extensions.

         ev67
         21264a
             Schedules as an EV6 and supports the BWX, CIX, FIX,
             and MAX extensions.

         Native toolchains also support the value native, which
         selects the best architecture option for the host
         processor.  -mcpu=native has no effect if GCC does not
         recognize the processor.

     -mtune=cpu_type
         Set only the instruction scheduling parameters for
         machine type cpu_type.  The instruction set is not
         changed.

         Native toolchains also support the value native, which
         selects the best architecture option for the host
         processor.  -mtune=native has no effect if GCC does not
         recognize the processor.

     -mmemory-latency=time
         Sets the latency the scheduler should assume for typical
         memory references as seen by the application.  This
         number is highly dependent on the memory access patterns
         used by the application and the size of the external
         cache on the machine.

         Valid options for time are

         number
             A decimal number representing clock cycles.

         L1
         L2
         L3
         main
             The compiler contains estimates of the number of
             clock cycles for "typical" EV4 & EV5 hardware for
             the Level 1, 2 & 3 caches (also called Dcache,
             Scache, and Bcache), as well as to main memory.
             Note that L3 is only valid for EV5.

     FR30 Options

     These options are defined specifically for the FR30 port.

     -msmall-model
         Use the small address space model.  This can produce
         smaller code, but it does assume that all symbolic
         values and addresses fit into a 20-bit range.

     -mno-lsim
         Assume that runtime support has been provided and so
         there is no need to include the simulator library
         (libsim.a) on the linker command line.

     FRV Options

     -mgpr-32
         Only use the first 32 general-purpose registers.

     -mgpr-64
         Use all 64 general-purpose registers.

     -mfpr-32
         Use only the first 32 floating-point registers.

     -mfpr-64
         Use all 64 floating-point registers.

     -mhard-float
         Use hardware instructions for floating-point operations.

     -msoft-float
         Use library routines for floating-point operations.

     -malloc-cc
         Dynamically allocate condition code registers.

     -mfixed-cc
         Do not try to dynamically allocate condition code
         registers, only use "icc0" and "fcc0".

     -mdword
         Change ABI to use double word insns.

     -mno-dword
         Do not use double word instructions.

     -mdouble
         Use floating-point double instructions.

     -mno-double
         Do not use floating-point double instructions.

     -mmedia
         Use media instructions.

     -mno-media
         Do not use media instructions.

     -mmuladd
         Use multiply and add/subtract instructions.

     -mno-muladd
         Do not use multiply and add/subtract instructions.

     -mfdpic
         Select the FDPIC ABI, which uses function descriptors to
         represent pointers to functions.  Without any
         PIC/PIE-related options, it implies -fPIE.  With -fpic
         or -fpie, it assumes GOT entries and small data are
         within a 12-bit range from the GOT base address; with
         -fPIC or -fPIE, GOT offsets are computed with 32 bits.
         With a bfin-elf target, this option implies -msim.

     -minline-plt
         Enable inlining of PLT entries in function calls to
         functions that are not known to bind locally.  It has no
         effect without -mfdpic.  It's enabled by default if
         optimizing for speed and compiling for shared libraries
         (i.e., -fPIC or -fpic), or when an optimization option
         such as -O3 or above is present in the command line.

     -mTLS
         Assume a large TLS segment when generating thread-local
         code.

     -mtls
         Do not assume a large TLS segment when generating
         thread-local code.

     -mgprel-ro
         Enable the use of "GPREL" relocations in the FDPIC ABI
         for data that is known to be in read-only sections.
         It's enabled by default, except for -fpic or -fpie: even
         though it may help make the global offset table smaller,
         it trades 1 instruction for 4.  With -fPIC or -fPIE, it
         trades 3 instructions for 4, one of which may be shared
         by multiple symbols, and it avoids the need for a GOT
         entry for the referenced symbol, so it's more likely to
         be a win.  If it is not, -mno-gprel-ro can be used to
         disable it.

     -multilib-library-pic
         Link with the (library, not FD) pic libraries.  It's
         implied by -mlibrary-pic, as well as by -fPIC and -fpic
         without -mfdpic.  You should never have to use it
         explicitly.

     -mlinked-fp
         Follow the EABI requirement of always creating a frame
         pointer whenever a stack frame is allocated.  This
         option is enabled by default and can be disabled with
         -mno-linked-fp.

     -mlong-calls
         Use indirect addressing to call functions outside the
         current compilation unit.  This allows the functions to
         be placed anywhere within the 32-bit address space.

     -malign-labels
         Try to align labels to an 8-byte boundary by inserting
         NOPs into the previous packet.  This option only has an
         effect when VLIW packing is enabled.  It doesn't create
         new packets; it merely adds NOPs to existing ones.

     -mlibrary-pic
         Generate position-independent EABI code.

     -macc-4
         Use only the first four media accumulator registers.

     -macc-8

         Use all eight media accumulator registers.

     -mpack
         Pack VLIW instructions.

     -mno-pack
         Do not pack VLIW instructions.

     -mno-eflags
         Do not mark ABI switches in e_flags.

     -mcond-move
         Enable the use of conditional-move instructions
         (default).

         This switch is mainly for debugging the compiler and
         will likely be removed in a future version.

     -mno-cond-move
         Disable the use of conditional-move instructions.

         This switch is mainly for debugging the compiler and
         will likely be removed in a future version.

     -mscc
         Enable the use of conditional set instructions
         (default).

         This switch is mainly for debugging the compiler and
         will likely be removed in a future version.

     -mno-scc
         Disable the use of conditional set instructions.

         This switch is mainly for debugging the compiler and
         will likely be removed in a future version.

     -mcond-exec
         Enable the use of conditional execution (default).

         This switch is mainly for debugging the compiler and
         will likely be removed in a future version.

     -mno-cond-exec
         Disable the use of conditional execution.

         This switch is mainly for debugging the compiler and
         will likely be removed in a future version.

     -mvliw-branch
         Run a pass to pack branches into VLIW instructions
         (default).

         This switch is mainly for debugging the compiler and
         will likely be removed in a future version.

     -mno-vliw-branch
         Do not run a pass to pack branches into VLIW
         instructions.

         This switch is mainly for debugging the compiler and
         will likely be removed in a future version.

     -mmulti-cond-exec
         Enable optimization of "&&" and "||" in conditional
         execution (default).

         This switch is mainly for debugging the compiler and
         will likely be removed in a future version.

     -mno-multi-cond-exec
         Disable optimization of "&&" and "||" in conditional
         execution.

         This switch is mainly for debugging the compiler and
         will likely be removed in a future version.

     -mnested-cond-exec
         Enable nested conditional execution optimizations
         (default).

         This switch is mainly for debugging the compiler and
         will likely be removed in a future version.

     -mno-nested-cond-exec
         Disable nested conditional execution optimizations.

         This switch is mainly for debugging the compiler and
         will likely be removed in a future version.

     -moptimize-membar
         This switch removes redundant "membar" instructions from
         the compiler-generated code.  It is enabled by default.

     -mno-optimize-membar
         This switch disables the automatic removal of redundant
         "membar" instructions from the generated code.

     -mtomcat-stats
         Cause gas to print out tomcat statistics.

     -mcpu=cpu
         Select the processor type for which to generate code.
         Possible values are frv, fr550, tomcat, fr500, fr450,
         fr405, fr400, fr300 and simple.

     GNU/Linux Options

     These -m options are defined for GNU/Linux targets:

     -mglibc
         Use the GNU C library.  This is the default except on
         *-*-linux-*uclibc* and *-*-linux-*android* targets.

     -muclibc
         Use uClibc C library.  This is the default on
         *-*-linux-*uclibc* targets.

     -mbionic
         Use Bionic C library.  This is the default on
         *-*-linux-*android* targets.

     -mandroid
         Compile code compatible with Android platform.  This is
         the default on *-*-linux-*android* targets.

         When compiling, this option enables -mbionic, -fPIC,
         -fno-exceptions and -fno-rtti by default.  When linking,
         this option makes the GCC driver pass Android-specific
         options to the linker.  Finally, this option causes the
         preprocessor macro "__ANDROID__" to be defined.

     -tno-android-cc
         Disable compilation effects of -mandroid, i.e., do not
         enable -mbionic, -fPIC, -fno-exceptions and -fno-rtti by
         default.

     -tno-android-ld
         Disable linking effects of -mandroid, i.e., pass
         standard Linux linking options to the linker.

     H8/300 Options

     These -m options are defined for the H8/300 implementations:

     -mrelax
         Shorten some address references at link time, when
         possible; uses the linker option -relax.

     -mh Generate code for the H8/300H.

     -ms Generate code for the H8S.

     -mn Generate code for the H8S and H8/300H in the normal
         mode.  This switch must be used either with -mh or -ms.

     -ms2600
         Generate code for the H8S/2600.  This switch must be
         used with -ms.

     -mexr
         Extended registers are stored on stack before execution
         of function with monitor attribute. Default option is
         -mexr.  This option is valid only for H8S targets.

     -mno-exr
         Extended registers are not stored on stack before
         execution of function with monitor attribute. Default
         option is -mno-exr. This option is valid only for H8S
         targets.

     -mint32
         Make "int" data 32 bits by default.

     -malign-300
         On the H8/300H and H8S, use the same alignment rules as
         for the H8/300.  The default for the H8/300H and H8S is
         to align longs and floats on 4-byte boundaries.
         -malign-300 causes them to be aligned on 2-byte
         boundaries.  This option has no effect on the H8/300.

     HPPA Options

     These -m options are defined for the HPPA family of
     computers:

     -march=architecture-type
         Generate code for the specified architecture.  The
         choices for architecture-type are 1.0 for PA 1.0, 1.1
         for PA 1.1, and 2.0 for PA 2.0 processors.  Refer to
         /usr/lib/sched.models on an HP-UX system to determine
         the proper architecture option for your machine.  Code
         compiled for lower numbered architectures runs on higher
         numbered architectures, but not the other way around.

     -mpa-risc-1-0
     -mpa-risc-1-1
     -mpa-risc-2-0
         Synonyms for -march=1.0, -march=1.1, and -march=2.0
         respectively.

     -mbig-switch
         Generate code suitable for big switch tables.  Use this
         option only if the assembler/linker complain about out-
         of-range branches within a switch table.

     -mjump-in-delay
         Fill delay slots of function calls with unconditional
         jump instructions by modifying the return pointer for
         the function call to be the target of the conditional
         jump.

     -mdisable-fpregs
         Prevent floating-point registers from being used in any
         manner.  This is necessary for compiling kernels that
         perform lazy context switching of floating-point
         registers.  If you use this option and attempt to
         perform floating-point operations, the compiler aborts.

     -mdisable-indexing
         Prevent the compiler from using indexing address modes.
         This avoids some rather obscure problems when compiling
         MIG generated code under MACH.

     -mno-space-regs
         Generate code that assumes the target has no space
         registers.  This allows GCC to generate faster indirect
         calls and use unscaled index address modes.

         Such code is suitable for level 0 PA systems and
         kernels.

     -mfast-indirect-calls
         Generate code that assumes calls never cross space
         boundaries.  This allows GCC to emit code that performs
         faster indirect calls.

         This option does not work in the presence of shared
         libraries or nested functions.

     -mfixed-range=register-range
         Generate code treating the given register range as fixed
         registers.  A fixed register is one that the register
         allocator cannot use.  This is useful when compiling
         kernel code.  A register range is specified as two
         registers separated by a dash.  Multiple register ranges
         can be specified separated by a comma.

     -mlong-load-store
         Generate 3-instruction load and store sequences as
         sometimes required by the HP-UX 10 linker.  This is
         equivalent to the +k option to the HP compilers.

     -mportable-runtime
         Use the portable calling conventions proposed by HP for
         ELF systems.

     -mgas
         Enable the use of assembler directives only GAS
         understands.

     -mschedule=cpu-type

         Schedule code according to the constraints for the
         machine type cpu-type.  The choices for cpu-type are 700
         7100, 7100LC, 7200, 7300 and 8000.  Refer to
         /usr/lib/sched.models on an HP-UX system to determine
         the proper scheduling option for your machine.  The
         default scheduling is 8000.

     -mlinker-opt
         Enable the optimization pass in the HP-UX linker.  Note
         this makes symbolic debugging impossible.  It also
         triggers a bug in the HP-UX 8 and HP-UX 9 linkers in
         which they give bogus error messages when linking some
         programs.

     -msoft-float
         Generate output containing library calls for floating
         point.  Warning: the requisite libraries are not
         available for all HPPA targets.  Normally the facilities
         of the machine's usual C compiler are used, but this
         cannot be done directly in cross-compilation.  You must
         make your own arrangements to provide suitable library
         functions for cross-compilation.

         -msoft-float changes the calling convention in the
         output file; therefore, it is only useful if you compile
         all of a program with this option.  In particular, you
         need to compile libgcc.a, the library that comes with
         GCC, with -msoft-float in order for this to work.

     -msio
         Generate the predefine, "_SIO", for server IO.  The
         default is -mwsio.  This generates the predefines,
         "__hp9000s700", "__hp9000s700__" and "_WSIO", for
         workstation IO.  These options are available under HP-UX
         and HI-UX.

     -mgnu-ld
         Use options specific to GNU ld.  This passes -shared to
         ld when building a shared library.  It is the default
         when GCC is configured, explicitly or implicitly, with
         the GNU linker.  This option does not affect which ld is
         called; it only changes what parameters are passed to
         that ld.  The ld that is called is determined by the
         --with-ld configure option, GCC's program search path,
         and finally by the user's PATH.  The linker used by GCC
         can be printed using which `gcc -print-prog-name=ld`.
         This option is only available on the 64-bit HP-UX GCC,
         i.e. configured with hppa*64*-*-hpux*.

     -mhp-ld
         Use options specific to HP ld.  This passes -b to ld
         when building a shared library and passes +Accept

         TypeMismatch to ld on all links.  It is the default when
         GCC is configured, explicitly or implicitly, with the HP
         linker.  This option does not affect which ld is called;
         it only changes what parameters are passed to that ld.
         The ld that is called is determined by the --with-ld
         configure option, GCC's program search path, and finally
         by the user's PATH.  The linker used by GCC can be
         printed using which `gcc -print-prog-name=ld`.  This
         option is only available on the 64-bit HP-UX GCC, i.e.
         configured with hppa*64*-*-hpux*.

     -mlong-calls
         Generate code that uses long call sequences.  This
         ensures that a call is always able to reach linker
         generated stubs.  The default is to generate long calls
         only when the distance from the call site to the
         beginning of the function or translation unit, as the
         case may be, exceeds a predefined limit set by the
         branch type being used.  The limits for normal calls are
         7,600,000 and 240,000 bytes, respectively for the PA 2.0
         and PA 1.X architectures.  Sibcalls are always limited
         at 240,000 bytes.

         Distances are measured from the beginning of functions
         when using the -ffunction-sections option, or when using
         the -mgas and -mno-portable-runtime options together
         under HP-UX with the SOM linker.

         It is normally not desirable to use this option as it
         degrades performance.  However, it may be useful in
         large applications, particularly when partial linking is
         used to build the application.

         The types of long calls used depends on the capabilities
         of the assembler and linker, and the type of code being
         generated.  The impact on systems that support long
         absolute calls, and long pic symbol-difference or pc-
         relative calls should be relatively small.  However, an
         indirect call is used on 32-bit ELF systems in pic code
         and it is quite long.

     -munix=unix-std
         Generate compiler predefines and select a startfile for
         the specified UNIX standard.  The choices for unix-std
         are 93, 95 and 98.  93 is supported on all HP-UX
         versions.  95 is available on HP-UX 10.10 and later.  98
         is available on HP-UX 11.11 and later.  The default
         values are 93 for HP-UX 10.00, 95 for HP-UX 10.10 though
         to 11.00, and 98 for HP-UX 11.11 and later.

         -munix=93 provides the same predefines as GCC 3.3 and
         3.4.  -munix=95 provides additional predefines for
         "XOPEN_UNIX" and "_XOPEN_SOURCE_EXTENDED", and the
         startfile unix95.o.  -munix=98 provides additional
         predefines for "_XOPEN_UNIX", "_XOPEN_SOURCE_EXTENDED",
         "_INCLUDE__STDC_A1_SOURCE" and
         "_INCLUDE_XOPEN_SOURCE_500", and the startfile unix98.o.

         It is important to note that this option changes the
         interfaces for various library routines.  It also
         affects the operational behavior of the C library.
         Thus, extreme care is needed in using this option.

         Library code that is intended to operate with more than
         one UNIX standard must test, set and restore the
         variable __xpg4_extended_mask as appropriate.  Most GNU
         software doesn't provide this capability.

     -nolibdld
         Suppress the generation of link options to search
         libdld.sl when the -static option is specified on HP-UX
         10 and later.

     -static
         The HP-UX implementation of setlocale in libc has a
         dependency on libdld.sl.  There isn't an archive version
         of libdld.sl.  Thus, when the -static option is
         specified, special link options are needed to resolve
         this dependency.

         On HP-UX 10 and later, the GCC driver adds the necessary
         options to link with libdld.sl when the -static option
         is specified.  This causes the resulting binary to be
         dynamic.  On the 64-bit port, the linkers generate
         dynamic binaries by default in any case.  The -nolibdld
         option can be used to prevent the GCC driver from adding
         these link options.

     -threads
         Add support for multithreading with the dce thread
         library under HP-UX.  This option sets flags for both
         the preprocessor and linker.

     Intel 386 and AMD x86-64 Options

     These -m options are defined for the i386 and x86-64 family
     of computers:

     -march=cpu-type
         Generate instructions for the machine type cpu-type.  In
         contrast to -mtune=cpu-type, which merely tunes the
         generated code for the specified cpu-type, -march=cpu-
         type allows GCC to generate code that may not run at all
         on processors other than the one indicated.  Specifying
         -march=cpu-type implies -mtune=cpu-type.

         The choices for cpu-type are:

         native
             This selects the CPU to generate code for at
             compilation time by determining the processor type
             of the compiling machine.  Using -march=native
             enables all instruction subsets supported by the
             local machine (hence the result might not run on
             different machines).  Using -mtune=native produces
             code optimized for the local machine under the
             constraints of the selected instruction set.

         i386
             Original Intel i386 CPU.

         i486
             Intel i486 CPU.  (No scheduling is implemented for
             this chip.)

         i586
         pentium
             Intel Pentium CPU with no MMX support.

         pentium-mmx
             Intel Pentium MMX CPU, based on Pentium core with
             MMX instruction set support.

         pentiumpro
             Intel Pentium Pro CPU.

         i686
             When used with -march, the Pentium Pro instruction
             set is used, so the code runs on all i686 family
             chips.  When used with -mtune, it has the same
             meaning as generic.

         pentium2
             Intel Pentium II CPU, based on Pentium Pro core with
             MMX instruction set support.

         pentium3
         pentium3m
             Intel Pentium III CPU, based on Pentium Pro core
             with MMX and SSE instruction set support.

         pentium-m
             Intel Pentium M; low-power version of Intel Pentium
             III CPU with MMX, SSE and SSE2 instruction set
             support.  Used by Centrino notebooks.

         pentium4
         pentium4m
             Intel Pentium 4 CPU with MMX, SSE and SSE2
             instruction set support.

         prescott
             Improved version of Intel Pentium 4 CPU with MMX,
             SSE, SSE2 and SSE3 instruction set support.

         nocona
             Improved version of Intel Pentium 4 CPU with 64-bit
             extensions, MMX, SSE, SSE2 and SSE3 instruction set
             support.

         core2
             Intel Core 2 CPU with 64-bit extensions, MMX, SSE,
             SSE2, SSE3 and SSSE3 instruction set support.

         corei7
             Intel Core i7 CPU with 64-bit extensions, MMX, SSE,
             SSE2, SSE3, SSSE3, SSE4.1 and SSE4.2 instruction set
             support.

         corei7-avx
             Intel Core i7 CPU with 64-bit extensions, MMX, SSE,
             SSE2, SSE3, SSSE3, SSE4.1, SSE4.2, AVX, AES and
             PCLMUL instruction set support.

         core-avx-i
             Intel Core CPU with 64-bit extensions, MMX, SSE,
             SSE2, SSE3, SSSE3, SSE4.1, SSE4.2, AVX, AES, PCLMUL,
             FSGSBASE, RDRND and F16C instruction set support.

         core-avx2
             Intel Core CPU with 64-bit extensions, MOVBE, MMX,
             SSE, SSE2, SSE3, SSSE3, SSE4.1, SSE4.2, AVX, AVX2,
             AES, PCLMUL, FSGSBASE, RDRND, FMA, BMI, BMI2 and
             F16C instruction set support.

         atom
             Intel Atom CPU with 64-bit extensions, MOVBE, MMX,
             SSE, SSE2, SSE3 and SSSE3 instruction set support.

         k6  AMD K6 CPU with MMX instruction set support.

         k6-2
         k6-3
             Improved versions of AMD K6 CPU with MMX and 3DNow!
             instruction set support.

         athlon
         athlon-tbird

             AMD Athlon CPU with MMX, 3dNOW!, enhanced 3DNow! and
             SSE prefetch instructions support.

         athlon-4
         athlon-xp
         athlon-mp
             Improved AMD Athlon CPU with MMX, 3DNow!, enhanced
             3DNow! and full SSE instruction set support.

         k8
         opteron
         athlon64
         athlon-fx
             Processors based on the AMD K8 core with x86-64
             instruction set support, including the AMD Opteron,
             Athlon 64, and Athlon 64 FX processors.  (This
             supersets MMX, SSE, SSE2, 3DNow!, enhanced 3DNow!
             and 64-bit instruction set extensions.)

         k8-sse3
         opteron-sse3
         athlon64-sse3
             Improved versions of AMD K8 cores with SSE3
             instruction set support.

         amdfam10
         barcelona
             CPUs based on AMD Family 10h cores with x86-64
             instruction set support.  (This supersets MMX, SSE,
             SSE2, SSE3, SSE4A, 3DNow!, enhanced 3DNow!, ABM and
             64-bit instruction set extensions.)

         bdver1
             CPUs based on AMD Family 15h cores with x86-64
             instruction set support.  (This supersets FMA4, AVX,
             XOP, LWP, AES, PCL_MUL, CX16, MMX, SSE, SSE2, SSE3,
             SSE4A, SSSE3, SSE4.1, SSE4.2, ABM and 64-bit
             instruction set extensions.)

         bdver2
             AMD Family 15h core based CPUs with x86-64
             instruction set support.  (This supersets BMI, TBM,
             F16C, FMA, AVX, XOP, LWP, AES, PCL_MUL, CX16, MMX,
             SSE, SSE2, SSE3, SSE4A, SSSE3, SSE4.1, SSE4.2, ABM
             and 64-bit instruction set extensions.)

         bdver3
             AMD Family 15h core based CPUs with x86-64
             instruction set support.  (This supersets BMI, TBM,
             F16C, FMA, AVX, XOP, LWP, AES, PCL_MUL, CX16, MMX,
             SSE, SSE2, SSE3, SSE4A, SSSE3, SSE4.1, SSE4.2, ABM
             and 64-bit instruction set extensions.

         btver1
             CPUs based on AMD Family 14h cores with x86-64
             instruction set support.  (This supersets MMX, SSE,
             SSE2, SSE3, SSSE3, SSE4A, CX16, ABM and 64-bit
             instruction set extensions.)

         btver2
             CPUs based on AMD Family 16h cores with x86-64
             instruction set support. This includes MOVBE, F16C,
             BMI, AVX, PCL_MUL, AES, SSE4.2, SSE4.1, CX16, ABM,
             SSE4A, SSSE3, SSE3, SSE2, SSE, MMX and 64-bit
             instruction set extensions.

         winchip-c6
             IDT WinChip C6 CPU, dealt in same way as i486 with
             additional MMX instruction set support.

         winchip2
             IDT WinChip 2 CPU, dealt in same way as i486 with
             additional MMX and 3DNow!  instruction set support.

         c3  VIA C3 CPU with MMX and 3DNow! instruction set
             support.  (No scheduling is implemented for this
             chip.)

         c3-2
             VIA C3-2 (Nehemiah/C5XL) CPU with MMX and SSE
             instruction set support.  (No scheduling is
             implemented for this chip.)

         geode
             AMD Geode embedded processor with MMX and 3DNow!
             instruction set support.

     -mtune=cpu-type
         Tune to cpu-type everything applicable about the
         generated code, except for the ABI and the set of
         available instructions. While picking a specific cpu-
         type schedules things appropriately for that particular
         chip, the compiler does not generate any code that
         cannot run on the default machine type unless you use a
         -march=cpu-type option.  For example, if GCC is
         configured for i686-pc-linux-gnu then -mtune=pentium4
         generates code that is tuned for Pentium 4 but still
         runs on i686 machines.

         The choices for cpu-type are the same as for -march.  In
         addition, -mtune supports an extra choice for cpu-type:

         generic
             Produce code optimized for the most common
             IA32/AMD64/EM64T processors.  If you know the CPU on
             which your code will run, then you should use the
             corresponding -mtune or -march option instead of
             -mtune=generic.  But, if you do not know exactly
             what CPU users of your application will have, then
             you should use this option.

             As new processors are deployed in the marketplace,
             the behavior of this option will change.  Therefore,
             if you upgrade to a newer version of GCC, code
             generation controlled by this option will change to
             reflect the processors that are most common at the
             time that version of GCC is released.

             There is no -march=generic option because -march
             indicates the instruction set the compiler can use,
             and there is no generic instruction set applicable
             to all processors.  In contrast, -mtune indicates
             the processor (or, in this case, collection of
             processors) for which the code is optimized.

     -mcpu=cpu-type
         A deprecated synonym for -mtune.

     -mfpmath=unit
         Generate floating-point arithmetic for selected unit
         unit.  The choices for unit are:

         387 Use the standard 387 floating-point coprocessor
             present on the majority of chips and emulated
             otherwise.  Code compiled with this option runs
             almost everywhere.  The temporary results are
             computed in 80-bit precision instead of the
             precision specified by the type, resulting in
             slightly different results compared to most of other
             chips.  See -ffloat-store for more detailed
             description.

             This is the default choice for i386 compiler.

         sse Use scalar floating-point instructions present in
             the SSE instruction set.  This instruction set is
             supported by Pentium III and newer chips, and in the
             AMD line by Athlon-4, Athlon XP and Athlon MP chips.
             The earlier version of the SSE instruction set
             supports only single-precision arithmetic, thus the
             double and extended-precision arithmetic are still
             done using 387.  A later version, present only in
             Pentium 4 and AMD x86-64 chips, supports double-
             precision arithmetic too.

             For the i386 compiler, you must use -march=cpu-type,
             -msse or -msse2 switches to enable SSE extensions
             and make this option effective.  For the x86-64
             compiler, these extensions are enabled by default.

             The resulting code should be considerably faster in
             the majority of cases and avoid the numerical
             instability problems of 387 code, but may break some
             existing code that expects temporaries to be 80
             bits.

             This is the default choice for the x86-64 compiler.

         sse,387
         sse+387
         both
             Attempt to utilize both instruction sets at once.
             This effectively doubles the amount of available
             registers, and on chips with separate execution
             units for 387 and SSE the execution resources too.
             Use this option with care, as it is still
             experimental, because the GCC register allocator
             does not model separate functional units well,
             resulting in unstable performance.

     -masm=dialect
         Output assembly instructions using selected dialect.
         Supported choices are intel or att (the default).
         Darwin does not support intel.

     -mieee-fp
     -mno-ieee-fp
         Control whether or not the compiler uses IEEE floating-
         point comparisons.  These correctly handle the case
         where the result of a comparison is unordered.

     -msoft-float
         Generate output containing library calls for floating
         point.

         Warning: the requisite libraries are not part of GCC.
         Normally the facilities of the machine's usual C
         compiler are used, but this can't be done directly in
         cross-compilation.  You must make your own arrangements
         to provide suitable library functions for cross-
         compilation.

         On machines where a function returns floating-point
         results in the 80387 register stack, some floating-point
         opcodes may be emitted even if -msoft-float is used.

     -mno-fp-ret-in-387
         Do not use the FPU registers for return values of
         functions.

         The usual calling convention has functions return values
         of types "float" and "double" in an FPU register, even
         if there is no FPU.  The idea is that the operating
         system should emulate an FPU.

         The option -mno-fp-ret-in-387 causes such values to be
         returned in ordinary CPU registers instead.

     -mno-fancy-math-387
         Some 387 emulators do not support the "sin", "cos" and
         "sqrt" instructions for the 387.  Specify this option to
         avoid generating those instructions.  This option is the
         default on FreeBSD, OpenBSD and NetBSD.  This option is
         overridden when -march indicates that the target CPU
         always has an FPU and so the instruction does not need
         emulation.  These instructions are not generated unless
         you also use the -funsafe-math-optimizations switch.

     -malign-double
     -mno-align-double
         Control whether GCC aligns "double", "long double", and
         "long long" variables on a two-word boundary or a one-
         word boundary.  Aligning "double" variables on a two-
         word boundary produces code that runs somewhat faster on
         a Pentium at the expense of more memory.

         On x86-64, -malign-double is enabled by default.

         Warning: if you use the -malign-double switch,
         structures containing the above types are aligned
         differently than the published application binary
         interface specifications for the 386 and are not binary
         compatible with structures in code compiled without that
         switch.

     -m96bit-long-double
     -m128bit-long-double
         These switches control the size of "long double" type.
         The i386 application binary interface specifies the size
         to be 96 bits, so -m96bit-long-double is the default in
         32-bit mode.

         Modern architectures (Pentium and newer) prefer "long
         double" to be aligned to an 8- or 16-byte boundary.  In
         arrays or structures conforming to the ABI, this is not
         possible.  So specifying -m128bit-long-double aligns
         "long double" to a 16-byte boundary by padding the "long
         double" with an additional 32-bit zero.

         In the x86-64 compiler, -m128bit-long-double is the
         default choice as its ABI specifies that "long double"
         is aligned on 16-byte boundary.

         Notice that neither of these options enable any extra
         precision over the x87 standard of 80 bits for a "long
         double".

         Warning: if you override the default value for your
         target ABI, this changes the size of structures and
         arrays containing "long double" variables, as well as
         modifying the function calling convention for functions
         taking "long double".  Hence they are not binary-
         compatible with code compiled without that switch.

     -mlong-double-64
     -mlong-double-80
         These switches control the size of "long double" type. A
         size of 64 bits makes the "long double" type equivalent
         to the "double" type. This is the default for Bionic C
         library.

         Warning: if you override the default value for your
         target ABI, this changes the size of structures and
         arrays containing "long double" variables, as well as
         modifying the function calling convention for functions
         taking "long double".  Hence they are not binary-
         compatible with code compiled without that switch.

     -mlarge-data-threshold=threshold
         When -mcmodel=medium is specified, data objects larger
         than threshold are placed in the large data section.
         This value must be the same across all objects linked
         into the binary, and defaults to 65535.

     -mrtd
         Use a different function-calling convention, in which
         functions that take a fixed number of arguments return
         with the "ret num" instruction, which pops their
         arguments while returning.  This saves one instruction
         in the caller since there is no need to pop the
         arguments there.

         You can specify that an individual function is called
         with this calling sequence with the function attribute
         stdcall.  You can also override the -mrtd option by
         using the function attribute cdecl.

         Warning: this calling convention is incompatible with
         the one normally used on Unix, so you cannot use it if
         you need to call libraries compiled with the Unix
         compiler.

         Also, you must provide function prototypes for all
         functions that take variable numbers of arguments
         (including "printf"); otherwise incorrect code is
         generated for calls to those functions.

         In addition, seriously incorrect code results if you
         call a function with too many arguments.  (Normally,
         extra arguments are harmlessly ignored.)

     -mregparm=num
         Control how many registers are used to pass integer
         arguments.  By default, no registers are used to pass
         arguments, and at most 3 registers can be used.  You can
         control this behavior for a specific function by using
         the function attribute regparm.

         Warning: if you use this switch, and num is nonzero,
         then you must build all modules with the same value,
         including any libraries.  This includes the system
         libraries and startup modules.

     -msseregparm
         Use SSE register passing conventions for float and
         double arguments and return values.  You can control
         this behavior for a specific function by using the
         function attribute sseregparm.

         Warning: if you use this switch then you must build all
         modules with the same value, including any libraries.
         This includes the system libraries and startup modules.

     -mvect8-ret-in-mem
         Return 8-byte vectors in memory instead of MMX
         registers.  This is the default on Solaris@tie{}8 and 9
         and VxWorks to match the ABI of the Sun Studio compilers
         until version 12.  Later compiler versions (starting
         with Studio 12 Update@tie{}1) follow the ABI used by
         other x86 targets, which is the default on
         Solaris@tie{}10 and later.  Only use this option if you
         need to remain compatible with existing code produced by
         those previous compiler versions or older versions of
         GCC.

     -mpc32
     -mpc64
     -mpc80
         Set 80387 floating-point precision to 32, 64 or 80 bits.
         When -mpc32 is specified, the significands of results of
         floating-point operations are rounded to 24 bits (single
         precision); -mpc64 rounds the significands of results of
         floating-point operations to 53 bits (double precision)
         and -mpc80 rounds the significands of results of
         floating-point operations to 64 bits (extended double
         precision), which is the default.  When this option is
         used, floating-point operations in higher precisions are
         not available to the programmer without setting the FPU
         control word explicitly.

         Setting the rounding of floating-point operations to
         less than the default 80 bits can speed some programs by
         2% or more.  Note that some mathematical libraries
         assume that extended-precision (80-bit) floating-point
         operations are enabled by default; routines in such
         libraries could suffer significant loss of accuracy,
         typically through so-called "catastrophic cancellation",
         when this option is used to set the precision to less
         than extended precision.

     -mstackrealign
         Realign the stack at entry.  On the Intel x86, the
         -mstackrealign option generates an alternate prologue
         and epilogue that realigns the run-time stack if
         necessary.  This supports mixing legacy codes that keep
         4-byte stack alignment with modern codes that keep
         16-byte stack alignment for SSE compatibility.  See also
         the attribute "force_align_arg_pointer", applicable to
         individual functions.

     -mpreferred-stack-boundary=num
         Attempt to keep the stack boundary aligned to a 2 raised
         to num byte boundary.  If -mpreferred-stack-boundary is
         not specified, the default is 4 (16 bytes or 128 bits).

         Warning: When generating code for the x86-64
         architecture with SSE extensions disabled,
         -mpreferred-stack-boundary=3 can be used to keep the
         stack boundary aligned to 8 byte boundary.  Since x86-64
         ABI require 16 byte stack alignment, this is ABI
         incompatible and intended to be used in controlled
         environment where stack space is important limitation.
         This option will lead to wrong code when functions
         compiled with 16 byte stack alignment (such as functions
         from a standard library) are called with misaligned
         stack.  In this case, SSE instructions may lead to
         misaligned memory access traps.  In addition, variable
         arguments will be handled incorrectly for 16 byte
         aligned objects (including x87 long double and
         __int128), leading to wrong results.  You must build all
         modules with -mpreferred-stack-boundary=3, including any
         libraries.  This includes the system libraries and
         startup modules.

     -mincoming-stack-boundary=num
         Assume the incoming stack is aligned to a 2 raised to
         num byte boundary.  If -mincoming-stack-boundary is not
         specified, the one specified by
         -mpreferred-stack-boundary is used.

         On Pentium and Pentium Pro, "double" and "long double"
         values should be aligned to an 8-byte boundary (see
         -malign-double) or suffer significant run time
         performance penalties.  On Pentium III, the Streaming
         SIMD Extension (SSE) data type "__m128" may not work
         properly if it is not 16-byte aligned.

         To ensure proper alignment of this values on the stack,
         the stack boundary must be as aligned as that required
         by any value stored on the stack.  Further, every
         function must be generated such that it keeps the stack
         aligned.  Thus calling a function compiled with a higher
         preferred stack boundary from a function compiled with a
         lower preferred stack boundary most likely misaligns the
         stack.  It is recommended that libraries that use
         callbacks always use the default setting.

         This extra alignment does consume extra stack space, and
         generally increases code size.  Code that is sensitive
         to stack space usage, such as embedded systems and
         operating system kernels, may want to reduce the
         preferred alignment to -mpreferred-stack-boundary=2.

     -mmmx
     -mno-mmx
     -msse
     -mno-sse
     -msse2
     -mno-sse2
     -msse3
     -mno-sse3
     -mssse3
     -mno-ssse3
     -msse4.1
     -mno-sse4.1
     -msse4.2
     -mno-sse4.2
     -msse4
     -mno-sse4
     -mavx
     -mno-avx
     -mavx2
     -mno-avx2
     -maes
     -mno-aes
     -mpclmul
     -mno-pclmul
     -mfsgsbase
     -mno-fsgsbase
     -mrdrnd
     -mno-rdrnd
     -mf16c
     -mno-f16c
     -mfma
     -mno-fma
     -msse4a
     -mno-sse4a
     -mfma4
     -mno-fma4
     -mxop
     -mno-xop
     -mlwp
     -mno-lwp
     -m3dnow
     -mno-3dnow
     -mpopcnt
     -mno-popcnt
     -mabm
     -mno-abm
     -mbmi
     -mbmi2
     -mno-bmi
     -mno-bmi2
     -mlzcnt
     -mno-lzcnt
     -mrtm
     -mtbm
     -mno-tbm
         These switches enable or disable the use of instructions
         in the MMX, SSE, SSE2, SSE3, SSSE3, SSE4.1, AVX, AVX2,
         AES, PCLMUL, FSGSBASE, RDRND, F16C, FMA, SSE4A, FMA4,
         XOP, LWP, ABM, BMI, BMI2, LZCNT, RTM or 3DNow!  extended
         instruction sets.  These extensions are also available
         as built-in functions: see X86 Built-in Functions, for
         details of the functions enabled and disabled by these
         switches.

         To generate SSE/SSE2 instructions automatically from
         floating-point code (as opposed to 387 instructions),
         see -mfpmath=sse.

         GCC depresses SSEx instructions when -mavx is used.
         Instead, it generates new AVX instructions or AVX
         equivalence for all SSEx instructions when needed.

         These options enable GCC to use these extended
         instructions in generated code, even without
         -mfpmath=sse.  Applications that perform run-time CPU
         detection must compile separate files for each supported
         architecture, using the appropriate flags.  In
         particular, the file containing the CPU detection code
         should be compiled without these options.

     -mcld

         This option instructs GCC to emit a "cld" instruction in
         the prologue of functions that use string instructions.
         String instructions depend on the DF flag to select
         between autoincrement or autodecrement mode.  While the
         ABI specifies the DF flag to be cleared on function
         entry, some operating systems violate this specification
         by not clearing the DF flag in their exception
         dispatchers.  The exception handler can be invoked with
         the DF flag set, which leads to wrong direction mode
         when string instructions are used.  This option can be
         enabled by default on 32-bit x86 targets by configuring
         GCC with the --enable-cld configure option.  Generation
         of "cld" instructions can be suppressed with the
         -mno-cld compiler option in this case.

     -mvzeroupper
         This option instructs GCC to emit a "vzeroupper"
         instruction before a transfer of control flow out of the
         function to minimize the AVX to SSE transition penalty
         as well as remove unnecessary "zeroupper" intrinsics.

     -mprefer-avx128
         This option instructs GCC to use 128-bit AVX
         instructions instead of 256-bit AVX instructions in the
         auto-vectorizer.

     -mcx16
         This option enables GCC to generate "CMPXCHG16B"
         instructions.  "CMPXCHG16B" allows for atomic operations
         on 128-bit double quadword (or oword) data types. This
         is useful for high-resolution counters that can be
         updated by multiple processors (or cores).  This
         instruction is generated as part of atomic built-in
         functions: see __sync Builtins or __atomic Builtins for
         details.

     -msahf
         This option enables generation of "SAHF" instructions in
         64-bit code.  Early Intel Pentium 4 CPUs with Intel 64
         support, prior to the introduction of Pentium 4 G1 step
         in December 2005, lacked the "LAHF" and "SAHF"
         instructions which were supported by AMD64.  These are
         load and store instructions, respectively, for certain
         status flags.  In 64-bit mode, the "SAHF" instruction is
         used to optimize "fmod", "drem", and "remainder" built-
         in functions; see Other Builtins for details.

     -mmovbe
         This option enables use of the "movbe" instruction to
         implement "__builtin_bswap32" and "__builtin_bswap64".

     -mcrc32

         This option enables built-in functions
         "__builtin_ia32_crc32qi", "__builtin_ia32_crc32hi",
         "__builtin_ia32_crc32si" and "__builtin_ia32_crc32di" to
         generate the "crc32" machine instruction.

     -mrecip
         This option enables use of "RCPSS" and "RSQRTSS"
         instructions (and their vectorized variants "RCPPS" and
         "RSQRTPS") with an additional Newton-Raphson step to
         increase precision instead of "DIVSS" and "SQRTSS" (and
         their vectorized variants) for single-precision
         floating-point arguments.  These instructions are
         generated only when -funsafe-math-optimizations is
         enabled together with -finite-math-only and
         -fno-trapping-math.  Note that while the throughput of
         the sequence is higher than the throughput of the non-
         reciprocal instruction, the precision of the sequence
         can be decreased by up to 2 ulp (i.e. the inverse of 1.0
         equals 0.99999994).

         Note that GCC implements "1.0f/sqrtf(x)" in terms of
         "RSQRTSS" (or "RSQRTPS") already with -ffast-math (or
         the above option combination), and doesn't need -mrecip.

         Also note that GCC emits the above sequence with
         additional Newton-Raphson step for vectorized single-
         float division and vectorized "sqrtf(x)" already with
         -ffast-math (or the above option combination), and
         doesn't need -mrecip.

     -mrecip=opt
         This option controls which reciprocal estimate
         instructions may be used.  opt is a comma-separated list
         of options, which may be preceded by a ! to invert the
         option:

         all Enable all estimate instructions.

         default
             Enable the default instructions, equivalent to
             -mrecip.

         none
             Disable all estimate instructions, equivalent to
             -mno-recip.

         div Enable the approximation for scalar division.

         vec-div
             Enable the approximation for vectorized division.

         sqrt

             Enable the approximation for scalar square root.

         vec-sqrt
             Enable the approximation for vectorized square root.

         So, for example, -mrecip=all,!sqrt enables all of the
         reciprocal approximations, except for square root.

     -mveclibabi=type
         Specifies the ABI type to use for vectorizing intrinsics
         using an external library.  Supported values for type
         are svml for the Intel short vector math library and
         acml for the AMD math core library.  To use this option,
         both -ftree-vectorize and -funsafe-math-optimizations
         have to be enabled, and an SVML or ACML ABI-compatible
         library must be specified at link time.

         GCC currently emits calls to "vmldExp2", "vmldLn2",
         "vmldLog102", "vmldLog102", "vmldPow2", "vmldTanh2",
         "vmldTan2", "vmldAtan2", "vmldAtanh2", "vmldCbrt2",
         "vmldSinh2", "vmldSin2", "vmldAsinh2", "vmldAsin2",
         "vmldCosh2", "vmldCos2", "vmldAcosh2", "vmldAcos2",
         "vmlsExp4", "vmlsLn4", "vmlsLog104", "vmlsLog104",
         "vmlsPow4", "vmlsTanh4", "vmlsTan4", "vmlsAtan4",
         "vmlsAtanh4", "vmlsCbrt4", "vmlsSinh4", "vmlsSin4",
         "vmlsAsinh4", "vmlsAsin4", "vmlsCosh4", "vmlsCos4",
         "vmlsAcosh4" and "vmlsAcos4" for corresponding function
         type when -mveclibabi=svml is used, and "__vrd2_sin",
         "__vrd2_cos", "__vrd2_exp", "__vrd2_log", "__vrd2_log2",
         "__vrd2_log10", "__vrs4_sinf", "__vrs4_cosf",
         "__vrs4_expf", "__vrs4_logf", "__vrs4_log2f",
         "__vrs4_log10f" and "__vrs4_powf" for the corresponding
         function type when -mveclibabi=acml is used.

     -mabi=name
         Generate code for the specified calling convention.
         Permissible values are sysv for the ABI used on
         GNU/Linux and other systems, and ms for the Microsoft
         ABI.  The default is to use the Microsoft ABI when
         targeting Microsoft Windows and the SysV ABI on all
         other systems.  You can control this behavior for a
         specific function by using the function attribute
         ms_abi/sysv_abi.

     -mtls-dialect=type
         Generate code to access thread-local storage using the
         gnu or gnu2 conventions.  gnu is the conservative
         default; gnu2 is more efficient, but it may add compile-
         and run-time requirements that cannot be satisfied on
         all systems.

     -mpush-args
     -mno-push-args
         Use PUSH operations to store outgoing parameters.  This
         method is shorter and usually equally fast as method
         using SUB/MOV operations and is enabled by default.  In
         some cases disabling it may improve performance because
         of improved scheduling and reduced dependencies.

     -maccumulate-outgoing-args
         If enabled, the maximum amount of space required for
         outgoing arguments is computed in the function prologue.
         This is faster on most modern CPUs because of reduced
         dependencies, improved scheduling and reduced stack
         usage when the preferred stack boundary is not equal to
         2.  The drawback is a notable increase in code size.
         This switch implies -mno-push-args.

     -mthreads
         Support thread-safe exception handling on MinGW.
         Programs that rely on thread-safe exception handling
         must compile and link all code with the -mthreads
         option.  When compiling, -mthreads defines "-D_MT"; when
         linking, it links in a special thread helper library
         -lmingwthrd which cleans up per-thread exception-
         handling data.

     -mno-align-stringops
         Do not align the destination of inlined string
         operations.  This switch reduces code size and improves
         performance in case the destination is already aligned,
         but GCC doesn't know about it.

     -minline-all-stringops
         By default GCC inlines string operations only when the
         destination is known to be aligned to least a 4-byte
         boundary. This enables more inlining and increases code
         size, but may improve performance of code that depends
         on fast "memcpy", "strlen", and "memset" for short
         lengths.

     -minline-stringops-dynamically
         For string operations of unknown size, use run-time
         checks with inline code for small blocks and a library
         call for large blocks.

     -mstringop-strategy=alg
         Override the internal decision heuristic for the
         particular algorithm to use for inlining string
         operations.  The allowed values for alg are:

         rep_byte
         rep_4byte
         rep_8byte

             Expand using i386 "rep" prefix of the specified
             size.

         byte_loop
         loop
         unrolled_loop
             Expand into an inline loop.

         libcall
             Always use a library call.

     -momit-leaf-frame-pointer
         Don't keep the frame pointer in a register for leaf
         functions.  This avoids the instructions to save, set
         up, and restore frame pointers and makes an extra
         register available in leaf functions.  The option
         -fomit-leaf-frame-pointer removes the frame pointer for
         leaf functions, which might make debugging harder.

     -mtls-direct-seg-refs
     -mno-tls-direct-seg-refs
         Controls whether TLS variables may be accessed with
         offsets from the TLS segment register (%gs for 32-bit,
         %fs for 64-bit), or whether the thread base pointer must
         be added.  Whether or not this is valid depends on the
         operating system, and whether it maps the segment to
         cover the entire TLS area.

         For systems that use the GNU C Library, the default is
         on.

     -msse2avx
     -mno-sse2avx
         Specify that the assembler should encode SSE
         instructions with VEX prefix.  The option -mavx turns
         this on by default.

     -mfentry
     -mno-fentry
         If profiling is active (-pg), put the profiling counter
         call before the prologue.  Note: On x86 architectures
         the attribute "ms_hook_prologue" isn't possible at the
         moment for -mfentry and -pg.

     -m8bit-idiv
     -mno-8bit-idiv
         On some processors, like Intel Atom, 8-bit unsigned
         integer divide is much faster than 32-bit/64-bit integer
         divide.  This option generates a run-time check.  If
         both dividend and divisor are within range of 0 to 255,
         8-bit unsigned integer divide is used instead of
         32-bit/64-bit integer divide.

     -mavx256-split-unaligned-load
     -mavx256-split-unaligned-store
         Split 32-byte AVX unaligned load and store.

     These -m switches are supported in addition to the above on
     x86-64 processors in 64-bit environments.

     -m32
     -m64
     -mx32
         Generate code for a 32-bit or 64-bit environment.  The
         -m32 option sets "int", "long", and pointer types to 32
         bits, and generates code that runs on any i386 system.

         The -m64 option sets "int" to 32 bits and "long" and
         pointer types to 64 bits, and generates code for the
         x86-64 architecture.  For Darwin only the -m64 option
         also turns off the -fno-pic and -mdynamic-no-pic
         options.

         The -mx32 option sets "int", "long", and pointer types
         to 32 bits, and generates code for the x86-64
         architecture.

     -mno-red-zone
         Do not use a so-called "red zone" for x86-64 code.  The
         red zone is mandated by the x86-64 ABI; it is a 128-byte
         area beyond the location of the stack pointer that is
         not modified by signal or interrupt handlers and
         therefore can be used for temporary data without
         adjusting the stack pointer.  The flag -mno-red-zone
         disables this red zone.

     -mcmodel=small
         Generate code for the small code model: the program and
         its symbols must be linked in the lower 2 GB of the
         address space.  Pointers are 64 bits.  Programs can be
         statically or dynamically linked.  This is the default
         code model.

     -mcmodel=kernel
         Generate code for the kernel code model.  The kernel
         runs in the negative 2 GB of the address space.  This
         model has to be used for Linux kernel code.

     -mcmodel=medium
         Generate code for the medium model: the program is
         linked in the lower 2 GB of the address space.  Small
         symbols are also placed there.  Symbols with sizes
         larger than -mlarge-data-threshold are put into large
         data or BSS sections and can be located above 2GB.
         Programs can be statically or dynamically linked.

     -mcmodel=large
         Generate code for the large model.  This model makes no
         assumptions about addresses and sizes of sections.

     -maddress-mode=long
         Generate code for long address mode.  This is only
         supported for 64-bit and x32 environments.  It is the
         default address mode for 64-bit environments.

     -maddress-mode=short
         Generate code for short address mode.  This is only
         supported for 32-bit and x32 environments.  It is the
         default address mode for 32-bit and x32 environments.

     i386 and x86-64 Windows Options

     These additional options are available for Microsoft Windows
     targets:

     -mconsole
         This option specifies that a console application is to
         be generated, by instructing the linker to set the PE
         header subsystem type required for console applications.
         This option is available for Cygwin and MinGW targets
         and is enabled by default on those targets.

     -mdll
         This option is available for Cygwin and MinGW targets.
         It specifies that a DLL---a dynamic link library---is to
         be generated, enabling the selection of the required
         runtime startup object and entry point.

     -mnop-fun-dllimport
         This option is available for Cygwin and MinGW targets.
         It specifies that the "dllimport" attribute should be
         ignored.

     -mthread
         This option is available for MinGW targets. It specifies
         that MinGW-specific thread support is to be used.

     -municode
         This option is available for MinGW-w64 targets.  It
         causes the "UNICODE" preprocessor macro to be
         predefined, and chooses Unicode-capable runtime startup
         code.

     -mwin32
         This option is available for Cygwin and MinGW targets.
         It specifies that the typical Microsoft Windows
         predefined macros are to be set in the pre-processor,
         but does not influence the choice of runtime
         library/startup code.

     -mwindows
         This option is available for Cygwin and MinGW targets.
         It specifies that a GUI application is to be generated
         by instructing the linker to set the PE header subsystem
         type appropriately.

     -fno-set-stack-executable
         This option is available for MinGW targets. It specifies
         that the executable flag for the stack used by nested
         functions isn't set. This is necessary for binaries
         running in kernel mode of Microsoft Windows, as there
         the User32 API, which is used to set executable
         privileges, isn't available.

     -fwritable-relocated-rdata
         This option is available for MinGW and Cygwin targets.
         It specifies that relocated-data in read-only section is
         put into .data section.  This is a necessary for older
         runtimes not supporting modification of .rdata sections
         for pseudo-relocation.

     -mpe-aligned-commons
         This option is available for Cygwin and MinGW targets.
         It specifies that the GNU extension to the PE file
         format that permits the correct alignment of COMMON
         variables should be used when generating code.  It is
         enabled by default if GCC detects that the target
         assembler found during configuration supports the
         feature.

     See also under i386 and x86-64 Options for standard options.

     IA-64 Options

     These are the -m options defined for the Intel IA-64
     architecture.

     -mbig-endian
         Generate code for a big-endian target.  This is the
         default for HP-UX.

     -mlittle-endian
         Generate code for a little-endian target.  This is the
         default for AIX5 and GNU/Linux.

     -mgnu-as
     -mno-gnu-as
         Generate (or don't) code for the GNU assembler.  This is
         the default.

     -mgnu-ld
     -mno-gnu-ld
         Generate (or don't) code for the GNU linker.  This is
         the default.

     -mno-pic
         Generate code that does not use a global pointer
         register.  The result is not position independent code,
         and violates the IA-64 ABI.

     -mvolatile-asm-stop
     -mno-volatile-asm-stop
         Generate (or don't) a stop bit immediately before and
         after volatile asm statements.

     -mregister-names
     -mno-register-names
         Generate (or don't) in, loc, and out register names for
         the stacked registers.  This may make assembler output
         more readable.

     -mno-sdata
     -msdata
         Disable (or enable) optimizations that use the small
         data section.  This may be useful for working around
         optimizer bugs.

     -mconstant-gp
         Generate code that uses a single constant global pointer
         value.  This is useful when compiling kernel code.

     -mauto-pic
         Generate code that is self-relocatable.  This implies
         -mconstant-gp.  This is useful when compiling firmware
         code.

     -minline-float-divide-min-latency
         Generate code for inline divides of floating-point
         values using the minimum latency algorithm.

     -minline-float-divide-max-throughput
         Generate code for inline divides of floating-point
         values using the maximum throughput algorithm.

     -mno-inline-float-divide
         Do not generate inline code for divides of floating-
         point values.

     -minline-int-divide-min-latency
         Generate code for inline divides of integer values using
         the minimum latency algorithm.

     -minline-int-divide-max-throughput
         Generate code for inline divides of integer values using
         the maximum throughput algorithm.

     -mno-inline-int-divide
         Do not generate inline code for divides of integer
         values.

     -minline-sqrt-min-latency
         Generate code for inline square roots using the minimum
         latency algorithm.

     -minline-sqrt-max-throughput
         Generate code for inline square roots using the maximum
         throughput algorithm.

     -mno-inline-sqrt
         Do not generate inline code for "sqrt".

     -mfused-madd
     -mno-fused-madd
         Do (don't) generate code that uses the fused
         multiply/add or multiply/subtract instructions.  The
         default is to use these instructions.

     -mno-dwarf2-asm
     -mdwarf2-asm
         Don't (or do) generate assembler code for the DWARF 2
         line number debugging info.  This may be useful when not
         using the GNU assembler.

     -mearly-stop-bits
     -mno-early-stop-bits
         Allow stop bits to be placed earlier than immediately
         preceding the instruction that triggered the stop bit.
         This can improve instruction scheduling, but does not
         always do so.

     -mfixed-range=register-range
         Generate code treating the given register range as fixed
         registers.  A fixed register is one that the register
         allocator cannot use.  This is useful when compiling
         kernel code.  A register range is specified as two
         registers separated by a dash.  Multiple register ranges
         can be specified separated by a comma.

     -mtls-size=tls-size
         Specify bit size of immediate TLS offsets.  Valid values
         are 14, 22, and 64.

     -mtune=cpu-type
         Tune the instruction scheduling for a particular CPU,

         Valid values are itanium, itanium1, merced, itanium2,
         and mckinley.

     -milp32
     -mlp64
         Generate code for a 32-bit or 64-bit environment.  The
         32-bit environment sets int, long and pointer to 32
         bits.  The 64-bit environment sets int to 32 bits and
         long and pointer to 64 bits.  These are HP-UX specific
         flags.

     -mno-sched-br-data-spec
     -msched-br-data-spec
         (Dis/En)able data speculative scheduling before reload.
         This results in generation of "ld.a" instructions and
         the corresponding check instructions ("ld.c" / "chk.a").
         The default is `disable'.

     -msched-ar-data-spec
     -mno-sched-ar-data-spec
         (En/Dis)able data speculative scheduling after reload.
         This results in generation of "ld.a" instructions and
         the corresponding check instructions ("ld.c" / "chk.a").
         The default is `enable'.

     -mno-sched-control-spec
     -msched-control-spec
         (Dis/En)able control speculative scheduling.  This
         feature is available only during region scheduling (i.e.
         before reload).  This results in generation of the
         "ld.s" instructions and the corresponding check
         instructions "chk.s".  The default is `disable'.

     -msched-br-in-data-spec
     -mno-sched-br-in-data-spec
         (En/Dis)able speculative scheduling of the instructions
         that are dependent on the data speculative loads before
         reload.  This is effective only with
         -msched-br-data-spec enabled.  The default is `enable'.

     -msched-ar-in-data-spec
     -mno-sched-ar-in-data-spec
         (En/Dis)able speculative scheduling of the instructions
         that are dependent on the data speculative loads after
         reload.  This is effective only with
         -msched-ar-data-spec enabled.  The default is `enable'.

     -msched-in-control-spec
     -mno-sched-in-control-spec
         (En/Dis)able speculative scheduling of the instructions
         that are dependent on the control speculative loads.
         This is effective only with -msched-control-spec
         enabled.  The default is `enable'.

     -mno-sched-prefer-non-data-spec-insns
     -msched-prefer-non-data-spec-insns
         If enabled, data-speculative instructions are chosen for
         schedule only if there are no other choices at the
         moment.  This makes the use of the data speculation much
         more conservative.  The default is `disable'.

     -mno-sched-prefer-non-control-spec-insns
     -msched-prefer-non-control-spec-insns
         If enabled, control-speculative instructions are chosen
         for schedule only if there are no other choices at the
         moment.  This makes the use of the control speculation
         much more conservative.  The default is `disable'.

     -mno-sched-count-spec-in-critical-path
     -msched-count-spec-in-critical-path
         If enabled, speculative dependencies are considered
         during computation of the instructions priorities.  This
         makes the use of the speculation a bit more
         conservative.  The default is `disable'.

     -msched-spec-ldc
         Use a simple data speculation check.  This option is on
         by default.

     -msched-control-spec-ldc
         Use a simple check for control speculation.  This option
         is on by default.

     -msched-stop-bits-after-every-cycle
         Place a stop bit after every cycle when scheduling.
         This option is on by default.

     -msched-fp-mem-deps-zero-cost
         Assume that floating-point stores and loads are not
         likely to cause a conflict when placed into the same
         instruction group.  This option is disabled by default.

     -msel-sched-dont-check-control-spec
         Generate checks for control speculation in selective
         scheduling.  This flag is disabled by default.

     -msched-max-memory-insns=max-insns
         Limit on the number of memory insns per instruction
         group, giving lower priority to subsequent memory insns
         attempting to schedule in the same instruction group.
         Frequently useful to prevent cache bank conflicts.  The
         default value is 1.

     -msched-max-memory-insns-hard-limit

         Makes the limit specified by msched-max-memory-insns a
         hard limit, disallowing more than that number in an
         instruction group.  Otherwise, the limit is "soft",
         meaning that non-memory operations are preferred when
         the limit is reached, but memory operations may still be
         scheduled.

     LM32 Options

     These -m options are defined for the LatticeMico32
     architecture:

     -mbarrel-shift-enabled
         Enable barrel-shift instructions.

     -mdivide-enabled
         Enable divide and modulus instructions.

     -mmultiply-enabled
         Enable multiply instructions.

     -msign-extend-enabled
         Enable sign extend instructions.

     -muser-enabled
         Enable user-defined instructions.

     M32C Options

     -mcpu=name
         Select the CPU for which code is generated.  name may be
         one of r8c for the R8C/Tiny series, m16c for the M16C
         (up to /60) series, m32cm for the M16C/80 series, or
         m32c for the M32C/80 series.

     -msim
         Specifies that the program will be run on the simulator.
         This causes an alternate runtime library to be linked in
         which supports, for example, file I/O.  You must not use
         this option when generating programs that will run on
         real hardware; you must provide your own runtime library
         for whatever I/O functions are needed.

     -memregs=number
         Specifies the number of memory-based pseudo-registers
         GCC uses during code generation.  These pseudo-registers
         are used like real registers, so there is a tradeoff
         between GCC's ability to fit the code into available
         registers, and the performance penalty of using memory
         instead of registers.  Note that all modules in a
         program must be compiled with the same value for this
         option.  Because of that, you must not use this option
         with GCC's default runtime libraries.

     M32R/D Options

     These -m options are defined for Renesas M32R/D
     architectures:

     -m32r2
         Generate code for the M32R/2.

     -m32rx
         Generate code for the M32R/X.

     -m32r
         Generate code for the M32R.  This is the default.

     -mmodel=small
         Assume all objects live in the lower 16MB of memory (so
         that their addresses can be loaded with the "ld24"
         instruction), and assume all subroutines are reachable
         with the "bl" instruction.  This is the default.

         The addressability of a particular object can be set
         with the "model" attribute.

     -mmodel=medium
         Assume objects may be anywhere in the 32-bit address
         space (the compiler generates "seth/add3" instructions
         to load their addresses), and assume all subroutines are
         reachable with the "bl" instruction.

     -mmodel=large
         Assume objects may be anywhere in the 32-bit address
         space (the compiler generates "seth/add3" instructions
         to load their addresses), and assume subroutines may not
         be reachable with the "bl" instruction (the compiler
         generates the much slower "seth/add3/jl" instruction
         sequence).

     -msdata=none
         Disable use of the small data area.  Variables are put
         into one of .data, .bss, or .rodata (unless the
         "section" attribute has been specified).  This is the
         default.

         The small data area consists of sections .sdata and
         .sbss.  Objects may be explicitly put in the small data
         area with the "section" attribute using one of these
         sections.

     -msdata=sdata
         Put small global and static data in the small data area,
         but do not generate special code to reference them.

     -msdata=use
         Put small global and static data in the small data area,
         and generate special instructions to reference them.

     -G num
         Put global and static objects less than or equal to num
         bytes into the small data or BSS sections instead of the
         normal data or BSS sections.  The default value of num
         is 8.  The -msdata option must be set to one of sdata or
         use for this option to have any effect.

         All modules should be compiled with the same -G num
         value.  Compiling with different values of num may or
         may not work; if it doesn't the linker gives an error
         message---incorrect code is not generated.

     -mdebug
         Makes the M32R-specific code in the compiler display
         some statistics that might help in debugging programs.

     -malign-loops
         Align all loops to a 32-byte boundary.

     -mno-align-loops
         Do not enforce a 32-byte alignment for loops.  This is
         the default.

     -missue-rate=number
         Issue number instructions per cycle.  number can only be
         1 or 2.

     -mbranch-cost=number
         number can only be 1 or 2.  If it is 1 then branches are
         preferred over conditional code, if it is 2, then the
         opposite applies.

     -mflush-trap=number
         Specifies the trap number to use to flush the cache.
         The default is 12.  Valid numbers are between 0 and 15
         inclusive.

     -mno-flush-trap
         Specifies that the cache cannot be flushed by using a
         trap.

     -mflush-func=name
         Specifies the name of the operating system function to
         call to flush the cache.  The default is _flush_cache,
         but a function call is only used if a trap is not
         available.

     -mno-flush-func
         Indicates that there is no OS function for flushing the
         cache.

     M680x0 Options

     These are the -m options defined for M680x0 and ColdFire
     processors.  The default settings depend on which
     architecture was selected when the compiler was configured;
     the defaults for the most common choices are given below.

     -march=arch
         Generate code for a specific M680x0 or ColdFire
         instruction set architecture.  Permissible values of
         arch for M680x0 architectures are: 68000, 68010, 68020,
         68030, 68040, 68060 and cpu32.  ColdFire architectures
         are selected according to Freescale's ISA classification
         and the permissible values are: isaa, isaaplus, isab and
         isac.

         GCC defines a macro __mcfarch__ whenever it is
         generating code for a ColdFire target.  The arch in this
         macro is one of the -march arguments given above.

         When used together, -march and -mtune select code that
         runs on a family of similar processors but that is
         optimized for a particular microarchitecture.

     -mcpu=cpu
         Generate code for a specific M680x0 or ColdFire
         processor.  The M680x0 cpus are: 68000, 68010, 68020,
         68030, 68040, 68060, 68302, 68332 and cpu32.  The
         ColdFire cpus are given by the table below, which also
         classifies the CPUs into families:

         Family : -mcpu arguments
        51qm
         51 : 51 51ac 51ag 51cn 51em 51je 51jf 51jg 51jm 51mm 51qe
         5206 : 5202 5204 5206
         5206e : 5206e
         5208 : 5207 5208
         5211a : 5210a 5211a
         5213 : 5211 5212 5213
         5216 : 5214 5216
         52235 : 52230 52231 52232 52233 52234 52235
         5225 : 5224 5225
         52259 : 52252 52254 52255 52256 52258 52259
         5235 : 5232 5233 5234 5235 523x
         5249 : 5249
         5250 : 5250
         5271 : 5270 5271
         5272 : 5272
         5275 : 5274 5275
         5282 : 5280 5281 5282 528x
         53017 : 53011 53012 53013 53014 53015 53016 53017
         5307 : 5307
         5329 : 5327 5328 5329 532x
         5373 : 5372 5373 537x
         5407 : 5407
        5484 5485
         5475 : 5470 5471 5472 5473 5474 5475 547x 5480 5481 5482 5483

         -mcpu=cpu overrides -march=arch if arch is compatible
         with cpu.  Other combinations of -mcpu and -march are
         rejected.

         GCC defines the macro __mcf_cpu_cpu when ColdFire target
         cpu is selected.  It also defines __mcf_family_family,
         where the value of family is given by the table above.

     -mtune=tune
         Tune the code for a particular microarchitecture within
         the constraints set by -march and -mcpu.  The M680x0
         microarchitectures are: 68000, 68010, 68020, 68030,
         68040, 68060 and cpu32.  The ColdFire microarchitectures
         are: cfv1, cfv2, cfv3, cfv4 and cfv4e.

         You can also use -mtune=68020-40 for code that needs to
         run relatively well on 68020, 68030 and 68040 targets.
         -mtune=68020-60 is similar but includes 68060 targets as
         well.  These two options select the same tuning
         decisions as -m68020-40 and -m68020-60 respectively.

         GCC defines the macros __mcarch and __mcarch__ when
         tuning for 680x0 architecture arch.  It also defines
         mcarch unless either -ansi or a non-GNU -std option is
         used.  If GCC is tuning for a range of architectures, as
         selected by -mtune=68020-40 or -mtune=68020-60, it
         defines the macros for every architecture in the range.

         GCC also defines the macro __muarch__ when tuning for
         ColdFire microarchitecture uarch, where uarch is one of
         the arguments given above.

     -m68000
     -mc68000
         Generate output for a 68000.  This is the default when
         the compiler is configured for 68000-based systems.  It
         is equivalent to -march=68000.

         Use this option for microcontrollers with a 68000 or
         EC000 core, including the 68008, 68302, 68306, 68307,
         68322, 68328 and 68356.

     -m68010
         Generate output for a 68010.  This is the default when
         the compiler is configured for 68010-based systems.  It
         is equivalent to -march=68010.

     -m68020
     -mc68020
         Generate output for a 68020.  This is the default when
         the compiler is configured for 68020-based systems.  It
         is equivalent to -march=68020.

     -m68030
         Generate output for a 68030.  This is the default when
         the compiler is configured for 68030-based systems.  It
         is equivalent to -march=68030.

     -m68040
         Generate output for a 68040.  This is the default when
         the compiler is configured for 68040-based systems.  It
         is equivalent to -march=68040.

         This option inhibits the use of 68881/68882 instructions
         that have to be emulated by software on the 68040.  Use
         this option if your 68040 does not have code to emulate
         those instructions.

     -m68060
         Generate output for a 68060.  This is the default when
         the compiler is configured for 68060-based systems.  It
         is equivalent to -march=68060.

         This option inhibits the use of 68020 and 68881/68882
         instructions that have to be emulated by software on the
         68060.  Use this option if your 68060 does not have code
         to emulate those instructions.

     -mcpu32
         Generate output for a CPU32.  This is the default when
         the compiler is configured for CPU32-based systems.  It
         is equivalent to -march=cpu32.

         Use this option for microcontrollers with a CPU32 or
         CPU32+ core, including the 68330, 68331, 68332, 68333,
         68334, 68336, 68340, 68341, 68349 and 68360.

     -m5200
         Generate output for a 520X ColdFire CPU.  This is the
         default when the compiler is configured for 520X-based
         systems.  It is equivalent to -mcpu=5206, and is now
         deprecated in favor of that option.

         Use this option for microcontroller with a 5200 core,
         including the MCF5202, MCF5203, MCF5204 and MCF5206.

     -m5206e
         Generate output for a 5206e ColdFire CPU.  The option is
         now deprecated in favor of the equivalent -mcpu=5206e.

     -m528x
         Generate output for a member of the ColdFire 528X
         family.  The option is now deprecated in favor of the
         equivalent -mcpu=528x.

     -m5307
         Generate output for a ColdFire 5307 CPU.  The option is
         now deprecated in favor of the equivalent -mcpu=5307.

     -m5407
         Generate output for a ColdFire 5407 CPU.  The option is
         now deprecated in favor of the equivalent -mcpu=5407.

     -mcfv4e
         Generate output for a ColdFire V4e family CPU (e.g.
         547x/548x).  This includes use of hardware floating-
         point instructions.  The option is equivalent to
         -mcpu=547x, and is now deprecated in favor of that
         option.

     -m68020-40
         Generate output for a 68040, without using any of the
         new instructions.  This results in code that can run
         relatively efficiently on either a 68020/68881 or a
         68030 or a 68040.  The generated code does use the 68881
         instructions that are emulated on the 68040.

         The option is equivalent to -march=68020
         -mtune=68020-40.

     -m68020-60
         Generate output for a 68060, without using any of the
         new instructions.  This results in code that can run
         relatively efficiently on either a 68020/68881 or a
         68030 or a 68040.  The generated code does use the 68881
         instructions that are emulated on the 68060.

         The option is equivalent to -march=68020
         -mtune=68020-60.

     -mhard-float
     -m68881
         Generate floating-point instructions.  This is the
         default for 68020 and above, and for ColdFire devices
         that have an FPU.  It defines the macro __HAVE_68881__
         on M680x0 targets and __mcffpu__ on ColdFire targets.

     -msoft-float
         Do not generate floating-point instructions; use library
         calls instead.  This is the default for 68000, 68010,
         and 68832 targets.  It is also the default for ColdFire
         devices that have no FPU.

     -mdiv
     -mno-div
         Generate (do not generate) ColdFire hardware divide and
         remainder instructions.  If -march is used without
         -mcpu, the default is "on" for ColdFire architectures
         and "off" for M680x0 architectures.  Otherwise, the
         default is taken from the target CPU (either the default
         CPU, or the one specified by -mcpu).  For example, the
         default is "off" for -mcpu=5206 and "on" for
         -mcpu=5206e.

         GCC defines the macro __mcfhwdiv__ when this option is
         enabled.

     -mshort
         Consider type "int" to be 16 bits wide, like "short
         int".  Additionally, parameters passed on the stack are
         also aligned to a 16-bit boundary even on targets whose
         API mandates promotion to 32-bit.

     -mno-short
         Do not consider type "int" to be 16 bits wide.  This is
         the default.

     -mnobitfield
     -mno-bitfield
         Do not use the bit-field instructions.  The -m68000,
         -mcpu32 and -m5200 options imply -mnobitfield.

     -mbitfield
         Do use the bit-field instructions.  The -m68020 option
         implies -mbitfield.  This is the default if you use a
         configuration designed for a 68020.

     -mrtd
         Use a different function-calling convention, in which
         functions that take a fixed number of arguments return
         with the "rtd" instruction, which pops their arguments
         while returning.  This saves one instruction in the
         caller since there is no need to pop the arguments
         there.

         This calling convention is incompatible with the one
         normally used on Unix, so you cannot use it if you need
         to call libraries compiled with the Unix compiler.

         Also, you must provide function prototypes for all
         functions that take variable numbers of arguments
         (including "printf"); otherwise incorrect code is
         generated for calls to those functions.

         In addition, seriously incorrect code results if you
         call a function with too many arguments.  (Normally,
         extra arguments are harmlessly ignored.)

         The "rtd" instruction is supported by the 68010, 68020,
         68030, 68040, 68060 and CPU32 processors, but not by the
         68000 or 5200.

     -mno-rtd
         Do not use the calling conventions selected by -mrtd.
         This is the default.

     -malign-int
     -mno-align-int
         Control whether GCC aligns "int", "long", "long long",
         "float", "double", and "long double" variables on a
         32-bit boundary (-malign-int) or a 16-bit boundary
         (-mno-align-int).  Aligning variables on 32-bit
         boundaries produces code that runs somewhat faster on
         processors with 32-bit busses at the expense of more
         memory.

         Warning: if you use the -malign-int switch, GCC aligns
         structures containing the above types differently than
         most published application binary interface
         specifications for the m68k.

     -mpcrel
         Use the pc-relative addressing mode of the 68000
         directly, instead of using a global offset table.  At
         present, this option implies -fpic, allowing at most a
         16-bit offset for pc-relative addressing.  -fPIC is not
         presently supported with -mpcrel, though this could be
         supported for 68020 and higher processors.

     -mno-strict-align
     -mstrict-align
         Do not (do) assume that unaligned memory references are
         handled by the system.

     -msep-data
         Generate code that allows the data segment to be located
         in a different area of memory from the text segment.
         This allows for execute-in-place in an environment
         without virtual memory management.  This option implies
         -fPIC.

     -mno-sep-data
         Generate code that assumes that the data segment follows
         the text segment.  This is the default.

     -mid-shared-library
         Generate code that supports shared libraries via the
         library ID method.  This allows for execute-in-place and
         shared libraries in an environment without virtual
         memory management.  This option implies -fPIC.

     -mno-id-shared-library
         Generate code that doesn't assume ID-based shared
         libraries are being used.  This is the default.

     -mshared-library-id=n
         Specifies the identification number of the ID-based
         shared library being compiled.  Specifying a value of 0
         generates more compact code; specifying other values
         forces the allocation of that number to the current
         library, but is no more space- or time-efficient than
         omitting this option.

     -mxgot
     -mno-xgot
         When generating position-independent code for ColdFire,
         generate code that works if the GOT has more than 8192
         entries.  This code is larger and slower than code
         generated without this option.  On M680x0 processors,
         this option is not needed; -fPIC suffices.

         GCC normally uses a single instruction to load values
         from the GOT.  While this is relatively efficient, it
         only works if the GOT is smaller than about 64k.
         Anything larger causes the linker to report an error
         such as:

                 relocation truncated to fit: R_68K_GOT16O foobar

         If this happens, you should recompile your code with
         -mxgot.  It should then work with very large GOTs.
         However, code generated with -mxgot is less efficient,
         since it takes 4 instructions to fetch the value of a
         global symbol.

         Note that some linkers, including newer versions of the
         GNU linker, can create multiple GOTs and sort GOT
         entries.  If you have such a linker, you should only
         need to use -mxgot when compiling a single object file
         that accesses more than 8192 GOT entries.  Very few do.

         These options have no effect unless GCC is generating
         position-independent code.

     MCore Options

     These are the -m options defined for the Motorola M*Core
     processors.

     -mhardlit
     -mno-hardlit
         Inline constants into the code stream if it can be done
         in two instructions or less.

     -mdiv
     -mno-div
         Use the divide instruction.  (Enabled by default).

     -mrelax-immediate
     -mno-relax-immediate
         Allow arbitrary-sized immediates in bit operations.

     -mwide-bitfields
     -mno-wide-bitfields
         Always treat bit-fields as "int"-sized.

     -m4byte-functions
     -mno-4byte-functions
         Force all functions to be aligned to a 4-byte boundary.

     -mcallgraph-data
     -mno-callgraph-data
         Emit callgraph information.

     -mslow-bytes
     -mno-slow-bytes
         Prefer word access when reading byte quantities.

     -mlittle-endian
     -mbig-endian
         Generate code for a little-endian target.

     -m210
     -m340
         Generate code for the 210 processor.

     -mno-lsim
         Assume that runtime support has been provided and so
         omit the simulator library (libsim.a) from the linker
         command line.

     -mstack-increment=size
         Set the maximum amount for a single stack increment
         operation.  Large values can increase the speed of
         programs that contain functions that need a large amount
         of stack space, but they can also trigger a segmentation
         fault if the stack is extended too much.  The default
         value is 0x1000.

     MeP Options

     -mabsdiff
         Enables the "abs" instruction, which is the absolute
         difference between two registers.

     -mall-opts
         Enables all the optional instructions---average,
         multiply, divide, bit operations, leading zero, absolute
         difference, min/max, clip, and saturation.

     -maverage
         Enables the "ave" instruction, which computes the
         average of two registers.

     -mbased=n
         Variables of size n bytes or smaller are placed in the
         ".based" section by default.  Based variables use the
         $tp register as a base register, and there is a 128-byte
         limit to the ".based" section.

     -mbitops
         Enables the bit operation instructions---bit test
         ("btstm"), set ("bsetm"), clear ("bclrm"), invert
         ("bnotm"), and test-and-set ("tas").

     -mc=name
         Selects which section constant data is placed in.  name
         may be "tiny", "near", or "far".

     -mclip
         Enables the "clip" instruction.  Note that "-mclip" is
         not useful unless you also provide "-mminmax".

     -mconfig=name
         Selects one of the built-in core configurations.  Each
         MeP chip has one or more modules in it; each module has
         a core CPU and a variety of coprocessors, optional
         instructions, and peripherals.  The "MeP-Integrator"
         tool, not part of GCC, provides these configurations
         through this option; using this option is the same as
         using all the corresponding command-line options.  The
         default configuration is "default".

     -mcop
         Enables the coprocessor instructions.  By default, this
         is a 32-bit coprocessor.  Note that the coprocessor is
         normally enabled via the "-mconfig=" option.

     -mcop32
         Enables the 32-bit coprocessor's instructions.

     -mcop64
         Enables the 64-bit coprocessor's instructions.

     -mivc2
         Enables IVC2 scheduling.  IVC2 is a 64-bit VLIW
         coprocessor.

     -mdc
         Causes constant variables to be placed in the ".near"
         section.

     -mdiv
         Enables the "div" and "divu" instructions.

     -meb
         Generate big-endian code.

     -mel
         Generate little-endian code.

     -mio-volatile
         Tells the compiler that any variable marked with the
         "io" attribute is to be considered volatile.

     -ml Causes variables to be assigned to the ".far" section by
         default.

     -mleadz
         Enables the "leadz" (leading zero) instruction.

     -mm Causes variables to be assigned to the ".near" section
         by default.

     -mminmax
         Enables the "min" and "max" instructions.

     -mmult
         Enables the multiplication and multiply-accumulate
         instructions.

     -mno-opts
         Disables all the optional instructions enabled by
         "-mall-opts".

     -mrepeat
         Enables the "repeat" and "erepeat" instructions, used
         for low-overhead looping.

     -ms Causes all variables to default to the ".tiny" section.

         Note that there is a 65536-byte limit to this section.
         Accesses to these variables use the %gp base register.

     -msatur
         Enables the saturation instructions.  Note that the
         compiler does not currently generate these itself, but
         this option is included for compatibility with other
         tools, like "as".

     -msdram
         Link the SDRAM-based runtime instead of the default
         ROM-based runtime.

     -msim
         Link the simulator runtime libraries.

     -msimnovec
         Link the simulator runtime libraries, excluding built-in
         support for reset and exception vectors and tables.

     -mtf
         Causes all functions to default to the ".far" section.
         Without this option, functions default to the ".near"
         section.

     -mtiny=n
         Variables that are n bytes or smaller are allocated to
         the ".tiny" section.  These variables use the $gp base
         register.  The default for this option is 4, but note
         that there's a 65536-byte limit to the ".tiny" section.

     MicroBlaze Options

     -msoft-float
         Use software emulation for floating point (default).

     -mhard-float
         Use hardware floating-point instructions.

     -mmemcpy
         Do not optimize block moves, use "memcpy".

     -mno-clearbss
         This option is deprecated.  Use
         -fno-zero-initialized-in-bss instead.

     -mcpu=cpu-type
         Use features of, and schedule code for, the given CPU.
         Supported values are in the format vX.YY.Z, where X is a
         major version, YY is the minor version, and Z is
         compatibility code.  Example values are v3.00.a,
         v4.00.b, v5.00.a, v5.00.b, v5.00.b, v6.00.a.

     -mxl-soft-mul
         Use software multiply emulation (default).

     -mxl-soft-div
         Use software emulation for divides (default).

     -mxl-barrel-shift
         Use the hardware barrel shifter.

     -mxl-pattern-compare
         Use pattern compare instructions.

     -msmall-divides
         Use table lookup optimization for small signed integer
         divisions.

     -mxl-stack-check
         This option is deprecated.  Use -fstack-check instead.

     -mxl-gp-opt
         Use GP-relative ".sdata"/".sbss" sections.

     -mxl-multiply-high
         Use multiply high instructions for high part of 32x32
         multiply.

     -mxl-float-convert
         Use hardware floating-point conversion instructions.

     -mxl-float-sqrt
         Use hardware floating-point square root instruction.

     -mbig-endian
         Generate code for a big-endian target.

     -mlittle-endian
         Generate code for a little-endian target.

     -mxl-reorder
         Use reorder instructions (swap and byte reversed
         load/store).

     -mxl-mode-app-model
         Select application model app-model.  Valid models are

         executable
             normal executable (default), uses startup code
             crt0.o.

         xmdstub
             for use with Xilinx Microprocessor Debugger (XMD)
             based software intrusive debug agent called xmdstub.

             This uses startup file crt1.o and sets the start
             address of the program to 0x800.

         bootstrap
             for applications that are loaded using a bootloader.
             This model uses startup file crt2.o which does not
             contain a processor reset vector handler. This is
             suitable for transferring control on a processor
             reset to the bootloader rather than the application.

         novectors
             for applications that do not require any of the
             MicroBlaze vectors. This option may be useful for
             applications running within a monitoring
             application. This model uses crt3.o as a startup
             file.

         Option -xl-mode-app-model is a deprecated alias for
         -mxl-mode-app-model.

     MIPS Options

     -EB Generate big-endian code.

     -EL Generate little-endian code.  This is the default for
         mips*el-*-* configurations.

     -march=arch
         Generate code that runs on arch, which can be the name
         of a generic MIPS ISA, or the name of a particular
         processor.  The ISA names are:  mips1, mips2, mips3,
         mips4, mips32, mips32r2, mips64 and mips64r2.  The
         processor names are:  4kc, 4km, 4kp, 4ksc, 4kec, 4kem,
         4kep, 4ksd, 5kc, 5kf, 20kc, 24kc, 24kf2_1, 24kf1_1,
         24kec, 24kef2_1, 24kef1_1, 34kc, 34kf2_1, 34kf1_1, 34kn,
         74kc, 74kf2_1, 74kf1_1, 74kf3_2, 1004kc, 1004kf2_1,
         1004kf1_1, loongson2e, loongson2f, loongson3a, m4k,
         octeon, octeon+, octeon2, orion, r2000, r3000, r3900,
         r4000, r4400, r4600, r4650, r4700, r6000, r8000, rm7000,
         rm9000, r10000, r12000, r14000, r16000, sb1, sr71000,
         vr4100, vr4111, vr4120, vr4130, vr4300, vr5000, vr5400,
         vr5500, xlr and xlp.  The special value from-abi selects
         the most compatible architecture for the selected ABI
         (that is, mips1 for 32-bit ABIs and mips3 for 64-bit
         ABIs).

         The native Linux/GNU toolchain also supports the value
         native, which selects the best architecture option for
         the host processor.  -march=native has no effect if GCC
         does not recognize the processor.

         In processor names, a final 000 can be abbreviated as k
         (for example, -march=r2k).  Prefixes are optional, and
         vr may be written r.

         Names of the form nf2_1 refer to processors with FPUs
         clocked at half the rate of the core, names of the form
         nf1_1 refer to processors with FPUs clocked at the same
         rate as the core, and names of the form nf3_2 refer to
         processors with FPUs clocked a ratio of 3:2 with respect
         to the core.  For compatibility reasons, nf is accepted
         as a synonym for nf2_1 while nx and bfx are accepted as
         synonyms for nf1_1.

         GCC defines two macros based on the value of this
         option.  The first is _MIPS_ARCH, which gives the name
         of target architecture, as a string.  The second has the
         form _MIPS_ARCH_foo, where foo is the capitalized value
         of _MIPS_ARCH.  For example, -march=r2000 sets
         _MIPS_ARCH to "r2000" and defines the macro
         _MIPS_ARCH_R2000.

         Note that the _MIPS_ARCH macro uses the processor names
         given above.  In other words, it has the full prefix and
         does not abbreviate 000 as k.  In the case of from-abi,
         the macro names the resolved architecture (either
         "mips1" or "mips3").  It names the default architecture
         when no -march option is given.

     -mtune=arch
         Optimize for arch.  Among other things, this option
         controls the way instructions are scheduled, and the
         perceived cost of arithmetic operations.  The list of
         arch values is the same as for -march.

         When this option is not used, GCC optimizes for the
         processor specified by -march.  By using -march and
         -mtune together, it is possible to generate code that
         runs on a family of processors, but optimize the code
         for one particular member of that family.

         -mtune defines the macros _MIPS_TUNE and _MIPS_TUNE_foo,
         which work in the same way as the -march ones described
         above.

     -mips1
         Equivalent to -march=mips1.

     -mips2
         Equivalent to -march=mips2.

     -mips3
         Equivalent to -march=mips3.

     -mips4
         Equivalent to -march=mips4.

     -mips32
         Equivalent to -march=mips32.

     -mips32r2
         Equivalent to -march=mips32r2.

     -mips64
         Equivalent to -march=mips64.

     -mips64r2
         Equivalent to -march=mips64r2.

     -mips16
     -mno-mips16
         Generate (do not generate) MIPS16 code.  If GCC is
         targeting a MIPS32 or MIPS64 architecture, it makes use
         of the MIPS16e ASE.

         MIPS16 code generation can also be controlled on a per-
         function basis by means of "mips16" and "nomips16"
         attributes.

     -mflip-mips16
         Generate MIPS16 code on alternating functions.  This
         option is provided for regression testing of mixed
         MIPS16/non-MIPS16 code generation, and is not intended
         for ordinary use in compiling user code.

     -minterlink-mips16
     -mno-interlink-mips16
         Require (do not require) that non-MIPS16 code be link-
         compatible with MIPS16 code.

         For example, non-MIPS16 code cannot jump directly to
         MIPS16 code; it must either use a call or an indirect
         jump.  -minterlink-mips16 therefore disables direct
         jumps unless GCC knows that the target of the jump is
         not MIPS16.

     -mabi=32
     -mabi=o64
     -mabi=n32
     -mabi=64
     -mabi=eabi
         Generate code for the given ABI.

         Note that the EABI has a 32-bit and a 64-bit variant.
         GCC normally generates 64-bit code when you select a
         64-bit architecture, but you can use -mgp32 to get
         32-bit code instead.

         For information about the O64 ABI, see
         <http://gcc.gnu.org/projects/mipso64-abi.html>.

         GCC supports a variant of the o32 ABI in which
         floating-point registers are 64 rather than 32 bits
         wide.  You can select this combination with -mabi=32
         -mfp64.  This ABI relies on the "mthc1" and "mfhc1"
         instructions and is therefore only supported for
         MIPS32R2 processors.

         The register assignments for arguments and return values
         remain the same, but each scalar value is passed in a
         single 64-bit register rather than a pair of 32-bit
         registers.  For example, scalar floating-point values
         are returned in $f0 only, not a $f0/$f1 pair.  The set
         of call-saved registers also remains the same, but all
         64 bits are saved.

     -mabicalls
     -mno-abicalls
         Generate (do not generate) code that is suitable for
         SVR4-style dynamic objects.  -mabicalls is the default
         for SVR4-based systems.

     -mshared
     -mno-shared
         Generate (do not generate) code that is fully position-
         independent, and that can therefore be linked into
         shared libraries.  This option only affects -mabicalls.

         All -mabicalls code has traditionally been position-
         independent, regardless of options like -fPIC and -fpic.
         However, as an extension, the GNU toolchain allows
         executables to use absolute accesses for locally-binding
         symbols.  It can also use shorter GP initialization
         sequences and generate direct calls to locally-defined
         functions.  This mode is selected by -mno-shared.

         -mno-shared depends on binutils 2.16 or higher and
         generates objects that can only be linked by the GNU
         linker.  However, the option does not affect the ABI of
         the final executable; it only affects the ABI of
         relocatable objects.  Using -mno-shared generally makes
         executables both smaller and quicker.

         -mshared is the default.

     -mplt
     -mno-plt
         Assume (do not assume) that the static and dynamic
         linkers support PLTs and copy relocations.  This option
         only affects -mno-shared -mabicalls.  For the n64 ABI,
         this option has no effect without -msym32.

         You can make -mplt the default by configuring GCC with
         --with-mips-plt.  The default is -mno-plt otherwise.

     -mxgot
     -mno-xgot
         Lift (do not lift) the usual restrictions on the size of
         the global offset table.

         GCC normally uses a single instruction to load values
         from the GOT.  While this is relatively efficient, it
         only works if the GOT is smaller than about 64k.
         Anything larger causes the linker to report an error
         such as:

                 relocation truncated to fit: R_MIPS_GOT16 foobar

         If this happens, you should recompile your code with
         -mxgot.  This works with very large GOTs, although the
         code is also less efficient, since it takes three
         instructions to fetch the value of a global symbol.

         Note that some linkers can create multiple GOTs.  If you
         have such a linker, you should only need to use -mxgot
         when a single object file accesses more than 64k's worth
         of GOT entries.  Very few do.

         These options have no effect unless GCC is generating
         position independent code.

     -mgp32
         Assume that general-purpose registers are 32 bits wide.

     -mgp64
         Assume that general-purpose registers are 64 bits wide.

     -mfp32
         Assume that floating-point registers are 32 bits wide.

     -mfp64
         Assume that floating-point registers are 64 bits wide.

     -mhard-float
         Use floating-point coprocessor instructions.

     -msoft-float
         Do not use floating-point coprocessor instructions.
         Implement floating-point calculations using library
         calls instead.

     -mno-float
         Equivalent to -msoft-float, but additionally asserts
         that the program being compiled does not perform any
         floating-point operations.  This option is presently
         supported only by some bare-metal MIPS configurations,
         where it may select a special set of libraries that lack
         all floating-point support (including, for example, the
         floating-point "printf" formats). If code compiled with
         "-mno-float" accidentally contains floating-point
         operations, it is likely to suffer a link-time or run-
         time failure.

     -msingle-float
         Assume that the floating-point coprocessor only supports
         single-precision operations.

     -mdouble-float
         Assume that the floating-point coprocessor supports
         double-precision operations.  This is the default.

     -mllsc
     -mno-llsc
         Use (do not use) ll, sc, and sync instructions to
         implement atomic memory built-in functions.  When
         neither option is specified, GCC uses the instructions
         if the target architecture supports them.

         -mllsc is useful if the runtime environment can emulate
         the instructions and -mno-llsc can be useful when
         compiling for nonstandard ISAs.  You can make either
         option the default by configuring GCC with --with-llsc
         and --without-llsc respectively.  --with-llsc is the
         default for some configurations; see the installation
         documentation for details.

     -mdsp
     -mno-dsp
         Use (do not use) revision 1 of the MIPS DSP ASE.
           This option defines the preprocessor macro __mips_dsp.
         It also defines __mips_dsp_rev to 1.

     -mdspr2
     -mno-dspr2
         Use (do not use) revision 2 of the MIPS DSP ASE.
           This option defines the preprocessor macros __mips_dsp
         and __mips_dspr2.  It also defines __mips_dsp_rev to 2.

     -msmartmips
     -mno-smartmips
         Use (do not use) the MIPS SmartMIPS ASE.

     -mpaired-single
     -mno-paired-single
         Use (do not use) paired-single floating-point
         instructions.
           This option requires hardware floating-point support
         to be enabled.

     -mdmx
     -mno-mdmx
         Use (do not use) MIPS Digital Media Extension
         instructions.  This option can only be used when
         generating 64-bit code and requires hardware floating-
         point support to be enabled.

     -mips3d
     -mno-mips3d
         Use (do not use) the MIPS-3D ASE. The option -mips3d
         implies -mpaired-single.

     -mmt
     -mno-mt
         Use (do not use) MT Multithreading instructions.

     -mmcu
     -mno-mcu
         Use (do not use) the MIPS MCU ASE instructions.

     -mlong64
         Force "long" types to be 64 bits wide.  See -mlong32 for
         an explanation of the default and the way that the
         pointer size is determined.

     -mlong32
         Force "long", "int", and pointer types to be 32 bits
         wide.

         The default size of "int"s, "long"s and pointers depends
         on the ABI.  All the supported ABIs use 32-bit "int"s.
         The n64 ABI uses 64-bit "long"s, as does the 64-bit
         EABI; the others use 32-bit "long"s.  Pointers are the
         same size as "long"s, or the same size as integer
         registers, whichever is smaller.

     -msym32
     -mno-sym32
         Assume (do not assume) that all symbols have 32-bit
         values, regardless of the selected ABI.  This option is
         useful in combination with -mabi=64 and -mno-abicalls
         because it allows GCC to generate shorter and faster
         references to symbolic addresses.

     -G num
         Put definitions of externally-visible data in a small
         data section if that data is no bigger than num bytes.
         GCC can then generate more efficient accesses to the
         data; see -mgpopt for details.

         The default -G option depends on the configuration.

     -mlocal-sdata
     -mno-local-sdata
         Extend (do not extend) the -G behavior to local data
         too, such as to static variables in C.  -mlocal-sdata is
         the default for all configurations.

         If the linker complains that an application is using too
         much small data, you might want to try rebuilding the
         less performance-critical parts with -mno-local-sdata.
         You might also want to build large libraries with
         -mno-local-sdata, so that the libraries leave more room
         for the main program.

     -mextern-sdata
     -mno-extern-sdata
         Assume (do not assume) that externally-defined data is
         in a small data section if the size of that data is
         within the -G limit.  -mextern-sdata is the default for
         all configurations.

         If you compile a module Mod with -mextern-sdata -G num
         -mgpopt, and Mod references a variable Var that is no
         bigger than num bytes, you must make sure that Var is
         placed in a small data section.  If Var is defined by
         another module, you must either compile that module with
         a high-enough -G setting or attach a "section" attribute
         to Var's definition.  If Var is common, you must link
         the application with a high-enough -G setting.

         The easiest way of satisfying these restrictions is to
         compile and link every module with the same -G option.
         However, you may wish to build a library that supports
         several different small data limits.  You can do this by
         compiling the library with the highest supported -G
         setting and additionally using -mno-extern-sdata to stop
         the library from making assumptions about externally-
         defined data.

     -mgpopt
     -mno-gpopt
         Use (do not use) GP-relative accesses for symbols that
         are known to be in a small data section; see -G,
         -mlocal-sdata and -mextern-sdata.  -mgpopt is the
         default for all configurations.

         -mno-gpopt is useful for cases where the $gp register
         might not hold the value of "_gp".  For example, if the
         code is part of a library that might be used in a boot
         monitor, programs that call boot monitor routines pass
         an unknown value in $gp.  (In such situations, the boot
         monitor itself is usually compiled with -G0.)

         -mno-gpopt implies -mno-local-sdata and
         -mno-extern-sdata.

     -membedded-data
     -mno-embedded-data
         Allocate variables to the read-only data section first
         if possible, then next in the small data section if
         possible, otherwise in data.  This gives slightly slower
         code than the default, but reduces the amount of RAM
         required when executing, and thus may be preferred for
         some embedded systems.

     -muninit-const-in-rodata
     -mno-uninit-const-in-rodata
         Put uninitialized "const" variables in the read-only
         data section.  This option is only meaningful in
         conjunction with -membedded-data.

     -mcode-readable=setting
         Specify whether GCC may generate code that reads from
         executable sections.  There are three possible settings:

         -mcode-readable=yes
             Instructions may freely access executable sections.
             This is the default setting.

         -mcode-readable=pcrel
             MIPS16 PC-relative load instructions can access
             executable sections, but other instructions must not
             do so.  This option is useful on 4KSc and 4KSd
             processors when the code TLBs have the Read Inhibit
             bit set.  It is also useful on processors that can
             be configured to have a dual instruction/data SRAM
             interface and that, like the M4K, automatically
             redirect PC-relative loads to the instruction RAM.

         -mcode-readable=no
             Instructions must not access executable sections.
             This option can be useful on targets that are
             configured to have a dual instruction/data SRAM
             interface but that (unlike the M4K) do not
             automatically redirect PC-relative loads to the
             instruction RAM.

     -msplit-addresses
     -mno-split-addresses

         Enable (disable) use of the "%hi()" and "%lo()"
         assembler relocation operators.  This option has been
         superseded by -mexplicit-relocs but is retained for
         backwards compatibility.

     -mexplicit-relocs
     -mno-explicit-relocs
         Use (do not use) assembler relocation operators when
         dealing with symbolic addresses.  The alternative,
         selected by -mno-explicit-relocs, is to use assembler
         macros instead.

         -mexplicit-relocs is the default if GCC was configured
         to use an assembler that supports relocation operators.

     -mcheck-zero-division
     -mno-check-zero-division
         Trap (do not trap) on integer division by zero.

         The default is -mcheck-zero-division.

     -mdivide-traps
     -mdivide-breaks
         MIPS systems check for division by zero by generating
         either a conditional trap or a break instruction.  Using
         traps results in smaller code, but is only supported on
         MIPS II and later.  Also, some versions of the Linux
         kernel have a bug that prevents trap from generating the
         proper signal ("SIGFPE").  Use -mdivide-traps to allow
         conditional traps on architectures that support them and
         -mdivide-breaks to force the use of breaks.

         The default is usually -mdivide-traps, but this can be
         overridden at configure time using --with-divide=breaks.
         Divide-by-zero checks can be completely disabled using
         -mno-check-zero-division.

     -mmemcpy
     -mno-memcpy
         Force (do not force) the use of "memcpy()" for non-
         trivial block moves.  The default is -mno-memcpy, which
         allows GCC to inline most constant-sized copies.

     -mlong-calls
     -mno-long-calls
         Disable (do not disable) use of the "jal" instruction.
         Calling functions using "jal" is more efficient but
         requires the caller and callee to be in the same 256
         megabyte segment.

         This option has no effect on abicalls code.  The default
         is -mno-long-calls.

     -mmad
     -mno-mad
         Enable (disable) use of the "mad", "madu" and "mul"
         instructions, as provided by the R4650 ISA.

     -mfused-madd
     -mno-fused-madd
         Enable (disable) use of the floating-point multiply-
         accumulate instructions, when they are available.  The
         default is -mfused-madd.

         On the R8000 CPU when multiply-accumulate instructions
         are used, the intermediate product is calculated to
         infinite precision and is not subject to the FCSR Flush
         to Zero bit.  This may be undesirable in some
         circumstances.  On other processors the result is
         numerically identical to the equivalent computation
         using separate multiply, add, subtract and negate
         instructions.

     -nocpp
         Tell the MIPS assembler to not run its preprocessor over
         user assembler files (with a .s suffix) when assembling
         them.

     -mfix-24k
     -mno-fix-24k
         Work around the 24K E48 (lost data on stores during
         refill) errata.  The workarounds are implemented by the
         assembler rather than by GCC.

     -mfix-r4000
     -mno-fix-r4000
         Work around certain R4000 CPU errata:

         -   A double-word or a variable shift may give an
             incorrect result if executed immediately after
             starting an integer division.

         -   A double-word or a variable shift may give an
             incorrect result if executed while an integer
             multiplication is in progress.

         -   An integer division may give an incorrect result if
             started in a delay slot of a taken branch or a jump.

     -mfix-r4400
     -mno-fix-r4400
         Work around certain R4400 CPU errata:

         -   A double-word or a variable shift may give an
             incorrect result if executed immediately after
             starting an integer division.

     -mfix-r10000
     -mno-fix-r10000
         Work around certain R10000 errata:

         -   "ll"/"sc" sequences may not behave atomically on
             revisions prior to 3.0.  They may deadlock on
             revisions 2.6 and earlier.

         This option can only be used if the target architecture
         supports branch-likely instructions.  -mfix-r10000 is
         the default when -march=r10000 is used; -mno-fix-r10000
         is the default otherwise.

     -mfix-vr4120
     -mno-fix-vr4120
         Work around certain VR4120 errata:

         -   "dmultu" does not always produce the correct result.

         -   "div" and "ddiv" do not always produce the correct
             result if one of the operands is negative.

         The workarounds for the division errata rely on special
         functions in libgcc.a.  At present, these functions are
         only provided by the "mips64vr*-elf" configurations.

         Other VR4120 errata require a NOP to be inserted between
         certain pairs of instructions.  These errata are handled
         by the assembler, not by GCC itself.

     -mfix-vr4130
         Work around the VR4130 "mflo"/"mfhi" errata.  The
         workarounds are implemented by the assembler rather than
         by GCC, although GCC avoids using "mflo" and "mfhi" if
         the VR4130 "macc", "macchi", "dmacc" and "dmacchi"
         instructions are available instead.

     -mfix-sb1
     -mno-fix-sb1
         Work around certain SB-1 CPU core errata.  (This flag
         currently works around the SB-1 revision 2 "F1" and "F2"
         floating-point errata.)

     -mr10k-cache-barrier=setting
         Specify whether GCC should insert cache barriers to
         avoid the side-effects of speculation on R10K
         processors.

         In common with many processors, the R10K tries to
         predict the outcome of a conditional branch and
         speculatively executes instructions from the "taken"
         branch.  It later aborts these instructions if the
         predicted outcome is wrong.  However, on the R10K, even
         aborted instructions can have side effects.

         This problem only affects kernel stores and, depending
         on the system, kernel loads.  As an example, a
         speculatively-executed store may load the target memory
         into cache and mark the cache line as dirty, even if the
         store itself is later aborted.  If a DMA operation
         writes to the same area of memory before the "dirty"
         line is flushed, the cached data overwrites the DMA-ed
         data.  See the R10K processor manual for a full
         description, including other potential problems.

         One workaround is to insert cache barrier instructions
         before every memory access that might be speculatively
         executed and that might have side effects even if
         aborted.  -mr10k-cache-barrier=setting controls GCC's
         implementation of this workaround.  It assumes that
         aborted accesses to any byte in the following regions
         does not have side effects:

         1.  the memory occupied by the current function's stack
             frame;

         2.  the memory occupied by an incoming stack argument;

         3.  the memory occupied by an object with a link-time-
             constant address.

         It is the kernel's responsibility to ensure that
         speculative accesses to these regions are indeed safe.

         If the input program contains a function declaration
         such as:

                 void foo (void);

         then the implementation of "foo" must allow "j foo" and
         "jal foo" to be executed speculatively.  GCC honors this
         restriction for functions it compiles itself.  It
         expects non-GCC functions (such as hand-written assembly
         code) to do the same.

         The option has three forms:

         -mr10k-cache-barrier=load-store
             Insert a cache barrier before a load or store that
             might be speculatively executed and that might have
             side effects even if aborted.

         -mr10k-cache-barrier=store
             Insert a cache barrier before a store that might be
             speculatively executed and that might have side
             effects even if aborted.

         -mr10k-cache-barrier=none
             Disable the insertion of cache barriers.  This is
             the default setting.

     -mflush-func=func
     -mno-flush-func
         Specifies the function to call to flush the I and D
         caches, or to not call any such function.  If called,
         the function must take the same arguments as the common
         "_flush_func()", that is, the address of the memory
         range for which the cache is being flushed, the size of
         the memory range, and the number 3 (to flush both
         caches).  The default depends on the target GCC was
         configured for, but commonly is either _flush_func or
         __cpu_flush.

     mbranch-cost=num
         Set the cost of branches to roughly num "simple"
         instructions.  This cost is only a heuristic and is not
         guaranteed to produce consistent results across
         releases.  A zero cost redundantly selects the default,
         which is based on the -mtune setting.

     -mbranch-likely
     -mno-branch-likely
         Enable or disable use of Branch Likely instructions,
         regardless of the default for the selected architecture.
         By default, Branch Likely instructions may be generated
         if they are supported by the selected architecture.  An
         exception is for the MIPS32 and MIPS64 architectures and
         processors that implement those architectures; for
         those, Branch Likely instructions are not be generated
         by default because the MIPS32 and MIPS64 architectures
         specifically deprecate their use.

     -mfp-exceptions
     -mno-fp-exceptions
         Specifies whether FP exceptions are enabled.  This
         affects how FP instructions are scheduled for some
         processors.  The default is that FP exceptions are
         enabled.

         For instance, on the SB-1, if FP exceptions are
         disabled, and we are emitting 64-bit code, then we can
         use both FP pipes.  Otherwise, we can only use one FP
         pipe.

     -mvr4130-align
     -mno-vr4130-align
         The VR4130 pipeline is two-way superscalar, but can only
         issue two instructions together if the first one is
         8-byte aligned.  When this option is enabled, GCC aligns
         pairs of instructions that it thinks should execute in
         parallel.

         This option only has an effect when optimizing for the
         VR4130.  It normally makes code faster, but at the
         expense of making it bigger.  It is enabled by default
         at optimization level -O3.

     -msynci
     -mno-synci
         Enable (disable) generation of "synci" instructions on
         architectures that support it.  The "synci" instructions
         (if enabled) are generated when
         "__builtin___clear_cache()" is compiled.

         This option defaults to "-mno-synci", but the default
         can be overridden by configuring with "--with-synci".

         When compiling code for single processor systems, it is
         generally safe to use "synci".  However, on many multi-
         core (SMP) systems, it does not invalidate the
         instruction caches on all cores and may lead to
         undefined behavior.

     -mrelax-pic-calls
     -mno-relax-pic-calls
         Try to turn PIC calls that are normally dispatched via
         register $25 into direct calls.  This is only possible
         if the linker can resolve the destination at link-time
         and if the destination is within range for a direct
         call.

         -mrelax-pic-calls is the default if GCC was configured
         to use an assembler and a linker that support the
         ".reloc" assembly directive and "-mexplicit-relocs" is
         in effect.  With "-mno-explicit-relocs", this
         optimization can be performed by the assembler and the
         linker alone without help from the compiler.

     -mmcount-ra-address
     -mno-mcount-ra-address
         Emit (do not emit) code that allows "_mcount" to modify
         the calling function's return address.  When enabled,
         this option extends the usual "_mcount" interface with a
         new ra-address parameter, which has type "intptr_t *"
         and is passed in register $12.  "_mcount" can then
         modify the return address by doing both of the
         following:

         *   Returning the new address in register $31.

         *   Storing the new address in "*ra-address", if ra-
             address is nonnull.

         The default is -mno-mcount-ra-address.

     MMIX Options

     These options are defined for the MMIX:

     -mlibfuncs
     -mno-libfuncs
         Specify that intrinsic library functions are being
         compiled, passing all values in registers, no matter the
         size.

     -mepsilon
     -mno-epsilon
         Generate floating-point comparison instructions that
         compare with respect to the "rE" epsilon register.

     -mabi=mmixware
     -mabi=gnu
         Generate code that passes function parameters and return
         values that (in the called function) are seen as
         registers $0 and up, as opposed to the GNU ABI which
         uses global registers $231 and up.

     -mzero-extend
     -mno-zero-extend
         When reading data from memory in sizes shorter than 64
         bits, use (do not use) zero-extending load instructions
         by default, rather than sign-extending ones.

     -mknuthdiv
     -mno-knuthdiv
         Make the result of a division yielding a remainder have
         the same sign as the divisor.  With the default,
         -mno-knuthdiv, the sign of the remainder follows the
         sign of the dividend.  Both methods are arithmetically
         valid, the latter being almost exclusively used.

     -mtoplevel-symbols
     -mno-toplevel-symbols
         Prepend (do not prepend) a : to all global symbols, so
         the assembly code can be used with the "PREFIX" assembly
         directive.

     -melf

         Generate an executable in the ELF format, rather than
         the default mmo format used by the mmix simulator.

     -mbranch-predict
     -mno-branch-predict
         Use (do not use) the probable-branch instructions, when
         static branch prediction indicates a probable branch.

     -mbase-addresses
     -mno-base-addresses
         Generate (do not generate) code that uses base
         addresses.  Using a base address automatically generates
         a request (handled by the assembler and the linker) for
         a constant to be set up in a global register.  The
         register is used for one or more base address requests
         within the range 0 to 255 from the value held in the
         register.  The generally leads to short and fast code,
         but the number of different data items that can be
         addressed is limited.  This means that a program that
         uses lots of static data may require
         -mno-base-addresses.

     -msingle-exit
     -mno-single-exit
         Force (do not force) generated code to have a single
         exit point in each function.

     MN10300 Options

     These -m options are defined for Matsushita MN10300
     architectures:

     -mmult-bug
         Generate code to avoid bugs in the multiply instructions
         for the MN10300 processors.  This is the default.

     -mno-mult-bug
         Do not generate code to avoid bugs in the multiply
         instructions for the MN10300 processors.

     -mam33
         Generate code using features specific to the AM33
         processor.

     -mno-am33
         Do not generate code using features specific to the AM33
         processor.  This is the default.

     -mam33-2
         Generate code using features specific to the AM33/2.0
         processor.

     -mam34
         Generate code using features specific to the AM34
         processor.

     -mtune=cpu-type
         Use the timing characteristics of the indicated CPU type
         when scheduling instructions.  This does not change the
         targeted processor type.  The CPU type must be one of
         mn10300, am33, am33-2 or am34.

     -mreturn-pointer-on-d0
         When generating a function that returns a pointer,
         return the pointer in both "a0" and "d0".  Otherwise,
         the pointer is returned only in "a0", and attempts to
         call such functions without a prototype result in
         errors.  Note that this option is on by default; use
         -mno-return-pointer-on-d0 to disable it.

     -mno-crt0
         Do not link in the C run-time initialization object
         file.

     -mrelax
         Indicate to the linker that it should perform a
         relaxation optimization pass to shorten branches, calls
         and absolute memory addresses.  This option only has an
         effect when used on the command line for the final link
         step.

         This option makes symbolic debugging impossible.

     -mliw
         Allow the compiler to generate Long Instruction Word
         instructions if the target is the AM33 or later.  This
         is the default.  This option defines the preprocessor
         macro __LIW__.

     -mnoliw
         Do not allow the compiler to generate Long Instruction
         Word instructions.  This option defines the preprocessor
         macro __NO_LIW__.

     -msetlb
         Allow the compiler to generate the SETLB and Lcc
         instructions if the target is the AM33 or later.  This
         is the default.  This option defines the preprocessor
         macro __SETLB__.

     -mnosetlb
         Do not allow the compiler to generate SETLB or Lcc
         instructions.  This option defines the preprocessor
         macro __NO_SETLB__.

     Moxie Options

     -meb
         Generate big-endian code.  This is the default for
         moxie-*-* configurations.

     -mel
         Generate little-endian code.

     -mno-crt0
         Do not link in the C run-time initialization object
         file.

     PDP-11 Options

     These options are defined for the PDP-11:

     -mfpu
         Use hardware FPP floating point.  This is the default.
         (FIS floating point on the PDP-11/40 is not supported.)

     -msoft-float
         Do not use hardware floating point.

     -mac0
         Return floating-point results in ac0 (fr0 in Unix
         assembler syntax).

     -mno-ac0
         Return floating-point results in memory.  This is the
         default.

     -m40
         Generate code for a PDP-11/40.

     -m45
         Generate code for a PDP-11/45.  This is the default.

     -m10
         Generate code for a PDP-11/10.

     -mbcopy-builtin
         Use inline "movmemhi" patterns for copying memory.  This
         is the default.

     -mbcopy
         Do not use inline "movmemhi" patterns for copying
         memory.

     -mint16
     -mno-int32
         Use 16-bit "int".  This is the default.

     -mint32
     -mno-int16
         Use 32-bit "int".

     -mfloat64
     -mno-float32
         Use 64-bit "float".  This is the default.

     -mfloat32
     -mno-float64
         Use 32-bit "float".

     -mabshi
         Use "abshi2" pattern.  This is the default.

     -mno-abshi
         Do not use "abshi2" pattern.

     -mbranch-expensive
         Pretend that branches are expensive.  This is for
         experimenting with code generation only.

     -mbranch-cheap
         Do not pretend that branches are expensive.  This is the
         default.

     -munix-asm
         Use Unix assembler syntax.  This is the default when
         configured for pdp11-*-bsd.

     -mdec-asm
         Use DEC assembler syntax.  This is the default when
         configured for any PDP-11 target other than pdp11-*-bsd.

     picoChip Options

     These -m options are defined for picoChip implementations:

     -mae=ae_type
         Set the instruction set, register set, and instruction
         scheduling parameters for array element type ae_type.
         Supported values for ae_type are ANY, MUL, and MAC.

         -mae=ANY selects a completely generic AE type.  Code
         generated with this option runs on any of the other AE
         types.  The code is not as efficient as it would be if
         compiled for a specific AE type, and some types of
         operation (e.g., multiplication) do not work properly on
         all types of AE.

         -mae=MUL selects a MUL AE type.  This is the most useful
         AE type for compiled code, and is the default.
         -mae=MAC selects a DSP-style MAC AE.  Code compiled with
         this option may suffer from poor performance of byte
         (char) manipulation, since the DSP AE does not provide
         hardware support for byte load/stores.

     -msymbol-as-address
         Enable the compiler to directly use a symbol name as an
         address in a load/store instruction, without first
         loading it into a register.  Typically, the use of this
         option generates larger programs, which run faster than
         when the option isn't used.  However, the results vary
         from program to program, so it is left as a user option,
         rather than being permanently enabled.

     -mno-inefficient-warnings
         Disables warnings about the generation of inefficient
         code.  These warnings can be generated, for example,
         when compiling code that performs byte-level memory
         operations on the MAC AE type.  The MAC AE has no
         hardware support for byte-level memory operations, so
         all byte load/stores must be synthesized from word
         load/store operations.  This is inefficient and a
         warning is generated to indicate that you should rewrite
         the code to avoid byte operations, or to target an AE
         type that has the necessary hardware support.  This
         option disables these warnings.

     PowerPC Options

     These are listed under

     RL78 Options

     -msim
         Links in additional target libraries to support
         operation within a simulator.

     -mmul=none
     -mmul=g13
     -mmul=rl78
         Specifies the type of hardware multiplication support to
         be used.  The default is "none", which uses software
         multiplication functions.  The "g13" option is for the
         hardware multiply/divide peripheral only on the RL78/G13
         targets.  The "rl78" option is for the standard hardware
         multiplication defined in the RL78 software manual.

     IBM RS/6000 and PowerPC Options

     These -m options are defined for the IBM RS/6000 and
     PowerPC:
     -mpowerpc-gpopt
     -mno-powerpc-gpopt
     -mpowerpc-gfxopt
     -mno-powerpc-gfxopt
     -mpowerpc64
     -mno-powerpc64
     -mmfcrf
     -mno-mfcrf
     -mpopcntb
     -mno-popcntb
     -mpopcntd
     -mno-popcntd
     -mfprnd
     -mno-fprnd
     -mcmpb
     -mno-cmpb
     -mmfpgpr
     -mno-mfpgpr
     -mhard-dfp
     -mno-hard-dfp
         You use these options to specify which instructions are
         available on the processor you are using.  The default
         value of these options is determined when configuring
         GCC.  Specifying the -mcpu=cpu_type overrides the
         specification of these options.  We recommend you use
         the -mcpu=cpu_type option rather than the options listed
         above.

         Specifying -mpowerpc-gpopt allows GCC to use the
         optional PowerPC architecture instructions in the
         General Purpose group, including floating-point square
         root.  Specifying -mpowerpc-gfxopt allows GCC to use the
         optional PowerPC architecture instructions in the
         Graphics group, including floating-point select.

         The -mmfcrf option allows GCC to generate the move from
         condition register field instruction implemented on the
         POWER4 processor and other processors that support the
         PowerPC V2.01 architecture.  The -mpopcntb option allows
         GCC to generate the popcount and double-precision FP
         reciprocal estimate instruction implemented on the
         POWER5 processor and other processors that support the
         PowerPC V2.02 architecture.  The -mpopcntd option allows
         GCC to generate the popcount instruction implemented on
         the POWER7 processor and other processors that support
         the PowerPC V2.06 architecture.  The -mfprnd option
         allows GCC to generate the FP round to integer
         instructions implemented on the POWER5+ processor and
         other processors that support the PowerPC V2.03
         architecture.  The -mcmpb option allows GCC to generate
         the compare bytes instruction implemented on the POWER6
         processor and other processors that support the PowerPC

         V2.05 architecture.  The -mmfpgpr option allows GCC to
         generate the FP move to/from general-purpose register
         instructions implemented on the POWER6X processor and
         other processors that support the extended PowerPC V2.05
         architecture.  The -mhard-dfp option allows GCC to
         generate the decimal floating-point instructions
         implemented on some POWER processors.

         The -mpowerpc64 option allows GCC to generate the
         additional 64-bit instructions that are found in the
         full PowerPC64 architecture and to treat GPRs as 64-bit,
         doubleword quantities.  GCC defaults to -mno-powerpc64.

     -mcpu=cpu_type
         Set architecture type, register usage, and instruction
         scheduling parameters for machine type cpu_type.
         Supported values for cpu_type are 401, 403, 405, 405fp,
         440, 440fp, 464, 464fp, 476, 476fp, 505, 601, 602, 603,
         603e, 604, 604e, 620, 630, 740, 7400, 7450, 750, 801,
         821, 823, 860, 970, 8540, a2, e300c2, e300c3, e500mc,
         e500mc64, e5500, e6500, ec603e, G3, G4, G5, titan,
         power3, power4, power5, power5+, power6, power6x,
         power7, power8, powerpc, powerpc64, and rs64.

         -mcpu=powerpc, and -mcpu=powerpc64 specify pure 32-bit
         PowerPC and 64-bit PowerPC architecture machine types,
         with an appropriate, generic processor model assumed for
         scheduling purposes.

         The other options specify a specific processor.  Code
         generated under those options runs best on that
         processor, and may not run at all on others.

         The -mcpu options automatically enable or disable the
         following options:

         -maltivec  -mfprnd  -mhard-float  -mmfcrf  -mmultiple
         -mpopcntb -mpopcntd  -mpowerpc64 -mpowerpc-gpopt
         -mpowerpc-gfxopt  -msingle-float -mdouble-float
         -msimple-fpu -mstring  -mmulhw  -mdlmzb  -mmfpgpr -mvsx

         The particular options set for any particular CPU varies
         between compiler versions, depending on what setting
         seems to produce optimal code for that CPU; it doesn't
         necessarily reflect the actual hardware's capabilities.
         If you wish to set an individual option to a particular
         value, you may specify it after the -mcpu option, like
         -mcpu=970 -mno-altivec.

         On AIX, the -maltivec and -mpowerpc64 options are not
         enabled or disabled by the -mcpu option at present
         because AIX does not have full support for these
         options.  You may still enable or disable them
         individually if you're sure it'll work in your
         environment.

     -mtune=cpu_type
         Set the instruction scheduling parameters for machine
         type cpu_type, but do not set the architecture type or
         register usage, as -mcpu=cpu_type does.  The same values
         for cpu_type are used for -mtune as for -mcpu.  If both
         are specified, the code generated uses the architecture
         and registers set by -mcpu, but the scheduling
         parameters set by -mtune.

     -mcmodel=small
         Generate PowerPC64 code for the small model: The TOC is
         limited to 64k.

     -mcmodel=medium
         Generate PowerPC64 code for the medium model: The TOC
         and other static data may be up to a total of 4G in
         size.

     -mcmodel=large
         Generate PowerPC64 code for the large model: The TOC may
         be up to 4G in size.  Other data and code is only
         limited by the 64-bit address space.

     -maltivec
     -mno-altivec
         Generate code that uses (does not use) AltiVec
         instructions, and also enable the use of built-in
         functions that allow more direct access to the AltiVec
         instruction set.  You may also need to set -mabi=altivec
         to adjust the current ABI with AltiVec ABI enhancements.

     -mvrsave
     -mno-vrsave
         Generate VRSAVE instructions when generating AltiVec
         code.

     -mgen-cell-microcode
         Generate Cell microcode instructions.

     -mwarn-cell-microcode
         Warn when a Cell microcode instruction is emitted.  An
         example of a Cell microcode instruction is a variable
         shift.

     -msecure-plt
         Generate code that allows ld and ld.so to build
         executables and shared libraries with non-executable
         ".plt" and ".got" sections.  This is a PowerPC 32-bit

         SYSV ABI option.

     -mbss-plt
         Generate code that uses a BSS ".plt" section that ld.so
         fills in, and requires ".plt" and ".got" sections that
         are both writable and executable.  This is a PowerPC
         32-bit SYSV ABI option.

     -misel
     -mno-isel
         This switch enables or disables the generation of ISEL
         instructions.

     -misel=yes/no
         This switch has been deprecated.  Use -misel and
         -mno-isel instead.

     -mspe
     -mno-spe
         This switch enables or disables the generation of SPE
         simd instructions.

     -mpaired
     -mno-paired
         This switch enables or disables the generation of PAIRED
         simd instructions.

     -mspe=yes/no
         This option has been deprecated.  Use -mspe and -mno-spe
         instead.

     -mvsx
     -mno-vsx
         Generate code that uses (does not use) vector/scalar
         (VSX) instructions, and also enable the use of built-in
         functions that allow more direct access to the VSX
         instruction set.

     -mfloat-gprs=yes/single/double/no
     -mfloat-gprs
         This switch enables or disables the generation of
         floating-point operations on the general-purpose
         registers for architectures that support it.

         The argument yes or single enables the use of single-
         precision floating-point operations.

         The argument double enables the use of single and
         double-precision floating-point operations.

         The argument no disables floating-point operations on
         the general-purpose registers.

         This option is currently only available on the MPC854x.

     -m32
     -m64
         Generate code for 32-bit or 64-bit environments of
         Darwin and SVR4 targets (including GNU/Linux).  The
         32-bit environment sets int, long and pointer to 32 bits
         and generates code that runs on any PowerPC variant.
         The 64-bit environment sets int to 32 bits and long and
         pointer to 64 bits, and generates code for PowerPC64, as
         for -mpowerpc64.

     -mfull-toc
     -mno-fp-in-toc
     -mno-sum-in-toc
     -mminimal-toc
         Modify generation of the TOC (Table Of Contents), which
         is created for every executable file.  The -mfull-toc
         option is selected by default.  In that case, GCC
         allocates at least one TOC entry for each unique non-
         automatic variable reference in your program.  GCC also
         places floating-point constants in the TOC.  However,
         only 16,384 entries are available in the TOC.

         If you receive a linker error message that saying you
         have overflowed the available TOC space, you can reduce
         the amount of TOC space used with the -mno-fp-in-toc and
         -mno-sum-in-toc options.  -mno-fp-in-toc prevents GCC
         from putting floating-point constants in the TOC and
         -mno-sum-in-toc forces GCC to generate code to calculate
         the sum of an address and a constant at run time instead
         of putting that sum into the TOC.  You may specify one
         or both of these options.  Each causes GCC to produce
         very slightly slower and larger code at the expense of
         conserving TOC space.

         If you still run out of space in the TOC even when you
         specify both of these options, specify -mminimal-toc
         instead.  This option causes GCC to make only one TOC
         entry for every file.  When you specify this option, GCC
         produces code that is slower and larger but which uses
         extremely little TOC space.  You may wish to use this
         option only on files that contain less frequently-
         executed code.

     -maix64
     -maix32
         Enable 64-bit AIX ABI and calling convention: 64-bit
         pointers, 64-bit "long" type, and the infrastructure
         needed to support them.  Specifying -maix64 implies
         -mpowerpc64, while -maix32 disables the 64-bit ABI and
         implies -mno-powerpc64.  GCC defaults to -maix32.

     -mxl-compat
     -mno-xl-compat
         Produce code that conforms more closely to IBM XL
         compiler semantics when using AIX-compatible ABI.  Pass
         floating-point arguments to prototyped functions beyond
         the register save area (RSA) on the stack in addition to
         argument FPRs.  Do not assume that most significant
         double in 128-bit long double value is properly rounded
         when comparing values and converting to double.  Use XL
         symbol names for long double support routines.

         The AIX calling convention was extended but not
         initially documented to handle an obscure K&R C case of
         calling a function that takes the address of its
         arguments with fewer arguments than declared.  IBM XL
         compilers access floating-point arguments that do not
         fit in the RSA from the stack when a subroutine is
         compiled without optimization.  Because always storing
         floating-point arguments on the stack is inefficient and
         rarely needed, this option is not enabled by default and
         only is necessary when calling subroutines compiled by
         IBM XL compilers without optimization.

     -mpe
         Support IBM RS/6000 SP Parallel Environment (PE).  Link
         an application written to use message passing with
         special startup code to enable the application to run.
         The system must have PE installed in the standard
         location (/usr/lpp/ppe.poe/), or the specs file must be
         overridden with the -specs= option to specify the
         appropriate directory location.  The Parallel
         Environment does not support threads, so the -mpe option
         and the -pthread option are incompatible.

     -malign-natural
     -malign-power
         On AIX, 32-bit Darwin, and 64-bit PowerPC GNU/Linux, the
         option -malign-natural overrides the ABI-defined
         alignment of larger types, such as floating-point
         doubles, on their natural size-based boundary.  The
         option -malign-power instructs GCC to follow the ABI-
         specified alignment rules.  GCC defaults to the standard
         alignment defined in the ABI.

         On 64-bit Darwin, natural alignment is the default, and
         -malign-power is not supported.

     -msoft-float
     -mhard-float
         Generate code that does not use (uses) the floating-
         point register set.  Software floating-point emulation
         is provided if you use the -msoft-float option, and pass
         the option to GCC when linking.

     -msingle-float
     -mdouble-float
         Generate code for single- or double-precision floating-
         point operations.  -mdouble-float implies
         -msingle-float.

     -msimple-fpu
         Do not generate "sqrt" and "div" instructions for
         hardware floating-point unit.

     -mfpu=name
         Specify type of floating-point unit.  Valid values for
         name are sp_lite (equivalent to -msingle-float
         -msimple-fpu), dp_lite (equivalent to -mdouble-float
         -msimple-fpu), sp_full (equivalent to -msingle-float),
         and dp_full (equivalent to -mdouble-float).

     -mxilinx-fpu
         Perform optimizations for the floating-point unit on
         Xilinx PPC 405/440.

     -mmultiple
     -mno-multiple
         Generate code that uses (does not use) the load multiple
         word instructions and the store multiple word
         instructions.  These instructions are generated by
         default on POWER systems, and not generated on PowerPC
         systems.  Do not use -mmultiple on little-endian PowerPC
         systems, since those instructions do not work when the
         processor is in little-endian mode.  The exceptions are
         PPC740 and PPC750 which permit these instructions in
         little-endian mode.

     -mstring
     -mno-string
         Generate code that uses (does not use) the load string
         instructions and the store string word instructions to
         save multiple registers and do small block moves.  These
         instructions are generated by default on POWER systems,
         and not generated on PowerPC systems.  Do not use
         -mstring on little-endian PowerPC systems, since those
         instructions do not work when the processor is in
         little-endian mode.  The exceptions are PPC740 and
         PPC750 which permit these instructions in little-endian
         mode.

     -mupdate
     -mno-update
         Generate code that uses (does not use) the load or store
         instructions that update the base register to the
         address of the calculated memory location.  These
         instructions are generated by default.  If you use
         -mno-update, there is a small window between the time
         that the stack pointer is updated and the address of the
         previous frame is stored, which means code that walks
         the stack frame across interrupts or signals may get
         corrupted data.

     -mavoid-indexed-addresses
     -mno-avoid-indexed-addresses
         Generate code that tries to avoid (not avoid) the use of
         indexed load or store instructions. These instructions
         can incur a performance penalty on Power6 processors in
         certain situations, such as when stepping through large
         arrays that cross a 16M boundary.  This option is
         enabled by default when targeting Power6 and disabled
         otherwise.

     -mfused-madd
     -mno-fused-madd
         Generate code that uses (does not use) the floating-
         point multiply and accumulate instructions.  These
         instructions are generated by default if hardware
         floating point is used.  The machine-dependent
         -mfused-madd option is now mapped to the machine-
         independent -ffp-contract=fast option, and
         -mno-fused-madd is mapped to -ffp-contract=off.

     -mmulhw
     -mno-mulhw
         Generate code that uses (does not use) the half-word
         multiply and multiply-accumulate instructions on the IBM
         405, 440, 464 and 476 processors.  These instructions
         are generated by default when targeting those
         processors.

     -mdlmzb
     -mno-dlmzb
         Generate code that uses (does not use) the string-search
         dlmzb instruction on the IBM 405, 440, 464 and 476
         processors.  This instruction is generated by default
         when targeting those processors.

     -mno-bit-align
     -mbit-align
         On System V.4 and embedded PowerPC systems do not (do)
         force structures and unions that contain bit-fields to
         be aligned to the base type of the bit-field.

         For example, by default a structure containing nothing
         but 8 "unsigned" bit-fields of length 1 is aligned to a
         4-byte boundary and has a size of 4 bytes.  By using
         -mno-bit-align, the structure is aligned to a 1-byte
         boundary and is 1 byte in size.

     -mno-strict-align
     -mstrict-align
         On System V.4 and embedded PowerPC systems do not (do)
         assume that unaligned memory references are handled by
         the system.

     -mrelocatable
     -mno-relocatable
         Generate code that allows (does not allow) a static
         executable to be relocated to a different address at run
         time.  A simple embedded PowerPC system loader should
         relocate the entire contents of ".got2" and 4-byte
         locations listed in the ".fixup" section, a table of
         32-bit addresses generated by this option.  For this to
         work, all objects linked together must be compiled with
         -mrelocatable or -mrelocatable-lib.  -mrelocatable code
         aligns the stack to an 8-byte boundary.

     -mrelocatable-lib
     -mno-relocatable-lib
         Like -mrelocatable, -mrelocatable-lib generates a
         ".fixup" section to allow static executables to be
         relocated at run time, but -mrelocatable-lib does not
         use the smaller stack alignment of -mrelocatable.
         Objects compiled with -mrelocatable-lib may be linked
         with objects compiled with any combination of the
         -mrelocatable options.

     -mno-toc
     -mtoc
         On System V.4 and embedded PowerPC systems do not (do)
         assume that register 2 contains a pointer to a global
         area pointing to the addresses used in the program.

     -mlittle
     -mlittle-endian
         On System V.4 and embedded PowerPC systems compile code
         for the processor in little-endian mode.  The
         -mlittle-endian option is the same as -mlittle.

     -mbig
     -mbig-endian
         On System V.4 and embedded PowerPC systems compile code
         for the processor in big-endian mode.  The -mbig-endian
         option is the same as -mbig.

     -mdynamic-no-pic
         On Darwin and Mac OS X systems, compile code so that it
         is not relocatable, but that its external references are
         relocatable.  The resulting code is suitable for
         applications, but not shared libraries.

     -msingle-pic-base
         Treat the register used for PIC addressing as read-only,
         rather than loading it in the prologue for each
         function.  The runtime system is responsible for
         initializing this register with an appropriate value
         before execution begins.

     -mprioritize-restricted-insns=priority
         This option controls the priority that is assigned to
         dispatch-slot restricted instructions during the second
         scheduling pass.  The argument priority takes the value
         0, 1, or 2 to assign no, highest, or second-highest
         (respectively) priority to dispatch-slot restricted
         instructions.

     -msched-costly-dep=dependence_type
         This option controls which dependences are considered
         costly by the target during instruction scheduling.  The
         argument dependence_type takes one of the following
         values:

         no  No dependence is costly.

         all All dependences are costly.

         true_store_to_load
             A true dependence from store to load is costly.

         store_to_load
             Any dependence from store to load is costly.

         number
             Any dependence for which the latency is greater than
             or equal to number is costly.

     -minsert-sched-nops=scheme
         This option controls which NOP insertion scheme is used
         during the second scheduling pass.  The argument scheme
         takes one of the following values:

         no  Don't insert NOPs.

         pad Pad with NOPs any dispatch group that has vacant
             issue slots, according to the scheduler's grouping.

         regroup_exact
             Insert NOPs to force costly dependent insns into
             separate groups.  Insert exactly as many NOPs as
             needed to force an insn to a new group, according to
             the estimated processor grouping.

         number
             Insert NOPs to force costly dependent insns into
             separate groups.  Insert number NOPs to force an
             insn to a new group.

     -mcall-sysv
         On System V.4 and embedded PowerPC systems compile code
         using calling conventions that adhere to the March 1995
         draft of the System V Application Binary Interface,
         PowerPC processor supplement.  This is the default
         unless you configured GCC using powerpc-*-eabiaix.

     -mcall-sysv-eabi
     -mcall-eabi
         Specify both -mcall-sysv and -meabi options.

     -mcall-sysv-noeabi
         Specify both -mcall-sysv and -mno-eabi options.

     -mcall-aixdesc
         On System V.4 and embedded PowerPC systems compile code
         for the AIX operating system.

     -mcall-linux
         On System V.4 and embedded PowerPC systems compile code
         for the Linux-based GNU system.

     -mcall-freebsd
         On System V.4 and embedded PowerPC systems compile code
         for the FreeBSD operating system.

     -mcall-netbsd
         On System V.4 and embedded PowerPC systems compile code
         for the NetBSD operating system.

     -mcall-openbsd
         On System V.4 and embedded PowerPC systems compile code
         for the OpenBSD operating system.

     -maix-struct-return
         Return all structures in memory (as specified by the AIX
         ABI).

     -msvr4-struct-return
         Return structures smaller than 8 bytes in registers (as
         specified by the SVR4 ABI).

     -mabi=abi-type
         Extend the current ABI with a particular extension, or
         remove such extension.  Valid values are altivec, no-
         altivec, spe, no-spe, ibmlongdouble, ieeelongdouble.

     -mabi=spe
         Extend the current ABI with SPE ABI extensions.  This
         does not change the default ABI, instead it adds the SPE
         ABI extensions to the current ABI.

     -mabi=no-spe
         Disable Book-E SPE ABI extensions for the current ABI.

     -mabi=ibmlongdouble
         Change the current ABI to use IBM extended-precision
         long double.  This is a PowerPC 32-bit SYSV ABI option.

     -mabi=ieeelongdouble
         Change the current ABI to use IEEE extended-precision
         long double.  This is a PowerPC 32-bit Linux ABI option.

     -mprototype
     -mno-prototype
         On System V.4 and embedded PowerPC systems assume that
         all calls to variable argument functions are properly
         prototyped.  Otherwise, the compiler must insert an
         instruction before every non-prototyped call to set or
         clear bit 6 of the condition code register (CR) to
         indicate whether floating-point values are passed in the
         floating-point registers in case the function takes
         variable arguments.  With -mprototype, only calls to
         prototyped variable argument functions set or clear the
         bit.

     -msim
         On embedded PowerPC systems, assume that the startup
         module is called sim-crt0.o and that the standard C
         libraries are libsim.a and libc.a.  This is the default
         for powerpc-*-eabisim configurations.

     -mmvme
         On embedded PowerPC systems, assume that the startup
         module is called crt0.o and the standard C libraries are
         libmvme.a and libc.a.

     -mads
         On embedded PowerPC systems, assume that the startup
         module is called crt0.o and the standard C libraries are
         libads.a and libc.a.

     -myellowknife
         On embedded PowerPC systems, assume that the startup
         module is called crt0.o and the standard C libraries are
         libyk.a and libc.a.

     -mvxworks
         On System V.4 and embedded PowerPC systems, specify that
         you are compiling for a VxWorks system.

     -memb
         On embedded PowerPC systems, set the PPC_EMB bit in the
         ELF flags header to indicate that eabi extended
         relocations are used.

     -meabi
     -mno-eabi
         On System V.4 and embedded PowerPC systems do (do not)
         adhere to the Embedded Applications Binary Interface
         (EABI), which is a set of modifications to the System
         V.4 specifications.  Selecting -meabi means that the
         stack is aligned to an 8-byte boundary, a function
         "__eabi" is called from "main" to set up the EABI
         environment, and the -msdata option can use both "r2"
         and "r13" to point to two separate small data areas.
         Selecting -mno-eabi means that the stack is aligned to a
         16-byte boundary, no EABI initialization function is
         called from "main", and the -msdata option only uses
         "r13" to point to a single small data area.  The -meabi
         option is on by default if you configured GCC using one
         of the powerpc*-*-eabi* options.

     -msdata=eabi
         On System V.4 and embedded PowerPC systems, put small
         initialized "const" global and static data in the
         .sdata2 section, which is pointed to by register "r2".
         Put small initialized non-"const" global and static data
         in the .sdata section, which is pointed to by register
         "r13".  Put small uninitialized global and static data
         in the .sbss section, which is adjacent to the .sdata
         section.  The -msdata=eabi option is incompatible with
         the -mrelocatable option.  The -msdata=eabi option also
         sets the -memb option.

     -msdata=sysv
         On System V.4 and embedded PowerPC systems, put small
         global and static data in the .sdata section, which is
         pointed to by register "r13".  Put small uninitialized
         global and static data in the .sbss section, which is
         adjacent to the .sdata section.  The -msdata=sysv option
         is incompatible with the -mrelocatable option.

     -msdata=default
     -msdata
         On System V.4 and embedded PowerPC systems, if -meabi is
         used, compile code the same as -msdata=eabi, otherwise
         compile code the same as -msdata=sysv.

     -msdata=data
         On System V.4 and embedded PowerPC systems, put small
         global data in the .sdata section.  Put small
         uninitialized global data in the .sbss section.  Do not
         use register "r13" to address small data however.  This
         is the default behavior unless other -msdata options are
         used.

     -msdata=none
     -mno-sdata
         On embedded PowerPC systems, put all initialized global
         and static data in the .data section, and all
         uninitialized data in the .bss section.

     -mblock-move-inline-limit=num
         Inline all block moves (such as calls to "memcpy" or
         structure copies) less than or equal to num bytes.  The
         minimum value for num is 32 bytes on 32-bit targets and
         64 bytes on 64-bit targets.  The default value is
         target-specific.

     -G num
         On embedded PowerPC systems, put global and static items
         less than or equal to num bytes into the small data or
         BSS sections instead of the normal data or BSS section.
         By default, num is 8.  The -G num switch is also passed
         to the linker.  All modules should be compiled with the
         same -G num value.

     -mregnames
     -mno-regnames
         On System V.4 and embedded PowerPC systems do (do not)
         emit register names in the assembly language output
         using symbolic forms.

     -mlongcall
     -mno-longcall
         By default assume that all calls are far away so that a
         longer and more expensive calling sequence is required.
         This is required for calls farther than 32 megabytes
         (33,554,432 bytes) from the current location.  A short
         call is generated if the compiler knows the call cannot
         be that far away.  This setting can be overridden by the
         "shortcall" function attribute, or by "#pragma
         longcall(0)".

         Some linkers are capable of detecting out-of-range calls
         and generating glue code on the fly.  On these systems,
         long calls are unnecessary and generate slower code.  As
         of this writing, the AIX linker can do this, as can the
         GNU linker for PowerPC/64.  It is planned to add this
         feature to the GNU linker for 32-bit PowerPC systems as
         well.

         On Darwin/PPC systems, "#pragma longcall" generates
         "jbsr callee, L42", plus a branch island (glue code).
         The two target addresses represent the callee and the
         branch island.  The Darwin/PPC linker prefers the first
         address and generates a "bl callee" if the PPC "bl"
         instruction reaches the callee directly; otherwise, the
         linker generates "bl L42" to call the branch island.
         The branch island is appended to the body of the calling
         function; it computes the full 32-bit address of the
         callee and jumps to it.

         On Mach-O (Darwin) systems, this option directs the
         compiler emit to the glue for every direct call, and the
         Darwin linker decides whether to use or discard it.

         In the future, GCC may ignore all longcall
         specifications when the linker is known to generate
         glue.

     -mtls-markers
     -mno-tls-markers
         Mark (do not mark) calls to "__tls_get_addr" with a
         relocation specifying the function argument.  The
         relocation allows the linker to reliably associate
         function call with argument setup instructions for TLS
         optimization, which in turn allows GCC to better
         schedule the sequence.

     -pthread
         Adds support for multithreading with the pthreads
         library.  This option sets flags for both the
         preprocessor and linker.

     -mrecip
     -mno-recip
         This option enables use of the reciprocal estimate and
         reciprocal square root estimate instructions with
         additional Newton-Raphson steps to increase precision
         instead of doing a divide or square root and divide for
         floating-point arguments.  You should use the
         -ffast-math option when using -mrecip (or at least
         -funsafe-math-optimizations, -finite-math-only,
         -freciprocal-math and -fno-trapping-math).  Note that
         while the throughput of the sequence is generally higher
         than the throughput of the non-reciprocal instruction,
         the precision of the sequence can be decreased by up to
         2 ulp (i.e. the inverse of 1.0 equals 0.99999994) for
         reciprocal square roots.

     -mrecip=opt

         This option controls which reciprocal estimate
         instructions may be used.  opt is a comma-separated list
         of options, which may be preceded by a "!" to invert the
         option:  "all": enable all estimate instructions,
         "default": enable the default instructions, equivalent
         to -mrecip, "none": disable all estimate instructions,
         equivalent to -mno-recip; "div": enable the reciprocal
         approximation instructions for both single and double
         precision; "divf": enable the single-precision
         reciprocal approximation instructions; "divd": enable
         the double-precision reciprocal approximation
         instructions; "rsqrt": enable the reciprocal square root
         approximation instructions for both single and double
         precision; "rsqrtf": enable the single-precision
         reciprocal square root approximation instructions;
         "rsqrtd": enable the double-precision reciprocal square
         root approximation instructions;

         So, for example, -mrecip=all,!rsqrtd enables all of the
         reciprocal estimate instructions, except for the
         "FRSQRTE", "XSRSQRTEDP", and "XVRSQRTEDP" instructions
         which handle the double-precision reciprocal square root
         calculations.

     -mrecip-precision
     -mno-recip-precision
         Assume (do not assume) that the reciprocal estimate
         instructions provide higher-precision estimates than is
         mandated by the PowerPC ABI.  Selecting -mcpu=power6,
         -mcpu=power7 or -mcpu=power8 automatically selects
         -mrecip-precision.  The double-precision square root
         estimate instructions are not generated by default on
         low-precision machines, since they do not provide an
         estimate that converges after three steps.

     -mveclibabi=type
         Specifies the ABI type to use for vectorizing intrinsics
         using an external library.  The only type supported at
         present is "mass", which specifies to use IBM's
         Mathematical Acceleration Subsystem (MASS) libraries for
         vectorizing intrinsics using external libraries.  GCC
         currently emits calls to "acosd2", "acosf4", "acoshd2",
         "acoshf4", "asind2", "asinf4", "asinhd2", "asinhf4",
         "atan2d2", "atan2f4", "atand2", "atanf4", "atanhd2",
         "atanhf4", "cbrtd2", "cbrtf4", "cosd2", "cosf4",
         "coshd2", "coshf4", "erfcd2", "erfcf4", "erfd2",
         "erff4", "exp2d2", "exp2f4", "expd2", "expf4",
         "expm1d2", "expm1f4", "hypotd2", "hypotf4", "lgammad2",
         "lgammaf4", "log10d2", "log10f4", "log1pd2", "log1pf4",
         "log2d2", "log2f4", "logd2", "logf4", "powd2", "powf4",
         "sind2", "sinf4", "sinhd2", "sinhf4", "sqrtd2",
         "sqrtf4", "tand2", "tanf4", "tanhd2", and "tanhf4" when
         generating code for power7.  Both -ftree-vectorize and
         -funsafe-math-optimizations must also be enabled.  The
         MASS libraries must be specified at link time.

     -mfriz
     -mno-friz
         Generate (do not generate) the "friz" instruction when
         the -funsafe-math-optimizations option is used to
         optimize rounding of floating-point values to 64-bit
         integer and back to floating point.  The "friz"
         instruction does not return the same value if the
         floating-point number is too large to fit in an integer.

     -mpointers-to-nested-functions
     -mno-pointers-to-nested-functions
         Generate (do not generate) code to load up the static
         chain register (r11) when calling through a pointer on
         AIX and 64-bit Linux systems where a function pointer
         points to a 3-word descriptor giving the function
         address, TOC value to be loaded in register r2, and
         static chain value to be loaded in register r11.  The
         -mpointers-to-nested-functions is on by default.  You
         cannot call through pointers to nested functions or
         pointers to functions compiled in other languages that
         use the static chain if you use the
         -mno-pointers-to-nested-functions.

     -msave-toc-indirect
     -mno-save-toc-indirect
         Generate (do not generate) code to save the TOC value in
         the reserved stack location in the function prologue if
         the function calls through a pointer on AIX and 64-bit
         Linux systems.  If the TOC value is not saved in the
         prologue, it is saved just before the call through the
         pointer.  The -mno-save-toc-indirect option is the
         default.

     RX Options

     These command-line options are defined for RX targets:

     -m64bit-doubles
     -m32bit-doubles
         Make the "double" data type be 64 bits (-m64bit-doubles)
         or 32 bits (-m32bit-doubles) in size.  The default is
         -m32bit-doubles.  Note RX floating-point hardware only
         works on 32-bit values, which is why the default is
         -m32bit-doubles.

     -fpu
     -nofpu
         Enables (-fpu) or disables (-nofpu) the use of RX
         floating-point hardware.  The default is enabled for the
         RX600 series and disabled for the RX200 series.

         Floating-point instructions are only generated for
         32-bit floating-point values, however, so the FPU
         hardware is not used for doubles if the -m64bit-doubles
         option is used.

         Note If the -fpu option is enabled then
         -funsafe-math-optimizations is also enabled
         automatically.  This is because the RX FPU instructions
         are themselves unsafe.

     -mcpu=name
         Selects the type of RX CPU to be targeted.  Currently
         three types are supported, the generic RX600 and RX200
         series hardware and the specific RX610 CPU.  The default
         is RX600.

         The only difference between RX600 and RX610 is that the
         RX610 does not support the "MVTIPL" instruction.

         The RX200 series does not have a hardware floating-point
         unit and so -nofpu is enabled by default when this type
         is selected.

     -mbig-endian-data
     -mlittle-endian-data
         Store data (but not code) in the big-endian format.  The
         default is -mlittle-endian-data, i.e. to store data in
         the little-endian format.

     -msmall-data-limit=N
         Specifies the maximum size in bytes of global and static
         variables which can be placed into the small data area.
         Using the small data area can lead to smaller and faster
         code, but the size of area is limited and it is up to
         the programmer to ensure that the area does not
         overflow.  Also when the small data area is used one of
         the RX's registers (usually "r13") is reserved for use
         pointing to this area, so it is no longer available for
         use by the compiler.  This could result in slower and/or
         larger code if variables are pushed onto the stack
         instead of being held in this register.

         Note, common variables (variables that have not been
         initialized) and constants are not placed into the small
         data area as they are assigned to other sections in the
         output executable.

         The default value is zero, which disables this feature.
         Note, this feature is not enabled by default with higher
         optimization levels (-O2 etc) because of the potentially
         detrimental effects of reserving a register.  It is up
         to the programmer to experiment and discover whether
         this feature is of benefit to their program.  See the
         description of the -mpid option for a description of how
         the actual register to hold the small data area pointer
         is chosen.

     -msim
     -mno-sim
         Use the simulator runtime.  The default is to use the
         libgloss board-specific runtime.

     -mas100-syntax
     -mno-as100-syntax
         When generating assembler output use a syntax that is
         compatible with Renesas's AS100 assembler.  This syntax
         can also be handled by the GAS assembler, but it has
         some restrictions so it is not generated by default.

     -mmax-constant-size=N
         Specifies the maximum size, in bytes, of a constant that
         can be used as an operand in a RX instruction.  Although
         the RX instruction set does allow constants of up to 4
         bytes in length to be used in instructions, a longer
         value equates to a longer instruction.  Thus in some
         circumstances it can be beneficial to restrict the size
         of constants that are used in instructions.  Constants
         that are too big are instead placed into a constant pool
         and referenced via register indirection.

         The value N can be between 0 and 4.  A value of 0 (the
         default) or 4 means that constants of any size are
         allowed.

     -mrelax
         Enable linker relaxation.  Linker relaxation is a
         process whereby the linker attempts to reduce the size
         of a program by finding shorter versions of various
         instructions.  Disabled by default.

     -mint-register=N
         Specify the number of registers to reserve for fast
         interrupt handler functions.  The value N can be between
         0 and 4.  A value of 1 means that register "r13" is
         reserved for the exclusive use of fast interrupt
         handlers.  A value of 2 reserves "r13" and "r12".  A
         value of 3 reserves "r13", "r12" and "r11", and a value
         of 4 reserves "r13" through "r10".  A value of 0, the
         default, does not reserve any registers.

     -msave-acc-in-interrupts

         Specifies that interrupt handler functions should
         preserve the accumulator register.  This is only
         necessary if normal code might use the accumulator
         register, for example because it performs 64-bit
         multiplications.  The default is to ignore the
         accumulator as this makes the interrupt handlers faster.

     -mpid
     -mno-pid
         Enables the generation of position independent data.
         When enabled any access to constant data is done via an
         offset from a base address held in a register.  This
         allows the location of constant data to be determined at
         run time without requiring the executable to be
         relocated, which is a benefit to embedded applications
         with tight memory constraints.  Data that can be
         modified is not affected by this option.

         Note, using this feature reserves a register, usually
         "r13", for the constant data base address.  This can
         result in slower and/or larger code, especially in
         complicated functions.

         The actual register chosen to hold the constant data
         base address depends upon whether the -msmall-data-limit
         and/or the -mint-register command-line options are
         enabled.  Starting with register "r13" and proceeding
         downwards, registers are allocated first to satisfy the
         requirements of -mint-register, then -mpid and finally
         -msmall-data-limit.  Thus it is possible for the small
         data area register to be "r8" if both -mint-register=4
         and -mpid are specified on the command line.

         By default this feature is not enabled.  The default can
         be restored via the -mno-pid command-line option.

     -mno-warn-multiple-fast-interrupts
     -mwarn-multiple-fast-interrupts
         Prevents GCC from issuing a warning message if it finds
         more than one fast interrupt handler when it is
         compiling a file.  The default is to issue a warning for
         each extra fast interrupt handler found, as the RX only
         supports one such interrupt.

     Note: The generic GCC command-line option -ffixed-reg has
     special significance to the RX port when used with the
     "interrupt" function attribute.  This attribute indicates a
     function intended to process fast interrupts.  GCC ensures
     that it only uses the registers "r10", "r11", "r12" and/or
     "r13" and only provided that the normal use of the
     corresponding registers have been restricted via the
     -ffixed-reg or -mint-register command-line options.

     S/390 and zSeries Options

     These are the -m options defined for the S/390 and zSeries
     architecture.

     -mhard-float
     -msoft-float
         Use (do not use) the hardware floating-point
         instructions and registers for floating-point
         operations.  When -msoft-float is specified, functions
         in libgcc.a are used to perform floating-point
         operations.  When -mhard-float is specified, the
         compiler generates IEEE floating-point instructions.
         This is the default.

     -mhard-dfp
     -mno-hard-dfp
         Use (do not use) the hardware decimal-floating-point
         instructions for decimal-floating-point operations.
         When -mno-hard-dfp is specified, functions in libgcc.a
         are used to perform decimal-floating-point operations.
         When -mhard-dfp is specified, the compiler generates
         decimal-floating-point hardware instructions.  This is
         the default for -march=z9-ec or higher.

     -mlong-double-64
     -mlong-double-128
         These switches control the size of "long double" type. A
         size of 64 bits makes the "long double" type equivalent
         to the "double" type. This is the default.

     -mbackchain
     -mno-backchain
         Store (do not store) the address of the caller's frame
         as backchain pointer into the callee's stack frame.  A
         backchain may be needed to allow debugging using tools
         that do not understand DWARF 2 call frame information.
         When -mno-packed-stack is in effect, the backchain
         pointer is stored at the bottom of the stack frame; when
         -mpacked-stack is in effect, the backchain is placed
         into the topmost word of the 96/160 byte register save
         area.

         In general, code compiled with -mbackchain is call-
         compatible with code compiled with -mmo-backchain;
         however, use of the backchain for debugging purposes
         usually requires that the whole binary is built with
         -mbackchain.  Note that the combination of -mbackchain,
         -mpacked-stack and -mhard-float is not supported.  In
         order to build a linux kernel use -msoft-float.

         The default is to not maintain the backchain.

     -mpacked-stack
     -mno-packed-stack
         Use (do not use) the packed stack layout.  When
         -mno-packed-stack is specified, the compiler uses the
         all fields of the 96/160 byte register save area only
         for their default purpose; unused fields still take up
         stack space.  When -mpacked-stack is specified, register
         save slots are densely packed at the top of the register
         save area; unused space is reused for other purposes,
         allowing for more efficient use of the available stack
         space.  However, when -mbackchain is also in effect, the
         topmost word of the save area is always used to store
         the backchain, and the return address register is always
         saved two words below the backchain.

         As long as the stack frame backchain is not used, code
         generated with -mpacked-stack is call-compatible with
         code generated with -mno-packed-stack.  Note that some
         non-FSF releases of GCC 2.95 for S/390 or zSeries
         generated code that uses the stack frame backchain at
         run time, not just for debugging purposes.  Such code is
         not call-compatible with code compiled with
         -mpacked-stack.  Also, note that the combination of
         -mbackchain, -mpacked-stack and -mhard-float is not
         supported.  In order to build a linux kernel use
         -msoft-float.

         The default is to not use the packed stack layout.

     -msmall-exec
     -mno-small-exec
         Generate (or do not generate) code using the "bras"
         instruction to do subroutine calls.  This only works
         reliably if the total executable size does not exceed
         64k.  The default is to use the "basr" instruction
         instead, which does not have this limitation.

     -m64
     -m31
         When -m31 is specified, generate code compliant to the
         GNU/Linux for S/390 ABI.  When -m64 is specified,
         generate code compliant to the GNU/Linux for zSeries
         ABI.  This allows GCC in particular to generate 64-bit
         instructions.  For the s390 targets, the default is
         -m31, while the s390x targets default to -m64.

     -mzarch
     -mesa
         When -mzarch is specified, generate code using the
         instructions available on z/Architecture.  When -mesa is
         specified, generate code using the instructions
         available on ESA/390.  Note that -mesa is not possible
         with -m64.  When generating code compliant to the
         GNU/Linux for S/390 ABI, the default is -mesa.  When
         generating code compliant to the GNU/Linux for zSeries
         ABI, the default is -mzarch.

     -mmvcle
     -mno-mvcle
         Generate (or do not generate) code using the "mvcle"
         instruction to perform block moves.  When -mno-mvcle is
         specified, use a "mvc" loop instead.  This is the
         default unless optimizing for size.

     -mdebug
     -mno-debug
         Print (or do not print) additional debug information
         when compiling.  The default is to not print debug
         information.

     -march=cpu-type
         Generate code that runs on cpu-type, which is the name
         of a system representing a certain processor type.
         Possible values for cpu-type are g5, g6, z900, z990,
         z9-109, z9-ec and z10.  When generating code using the
         instructions available on z/Architecture, the default is
         -march=z900.  Otherwise, the default is -march=g5.

     -mtune=cpu-type
         Tune to cpu-type everything applicable about the
         generated code, except for the ABI and the set of
         available instructions.  The list of cpu-type values is
         the same as for -march.  The default is the value used
         for -march.

     -mtpf-trace
     -mno-tpf-trace
         Generate code that adds (does not add) in TPF OS
         specific branches to trace routines in the operating
         system.  This option is off by default, even when
         compiling for the TPF OS.

     -mfused-madd
     -mno-fused-madd
         Generate code that uses (does not use) the floating-
         point multiply and accumulate instructions.  These
         instructions are generated by default if hardware
         floating point is used.

     -mwarn-framesize=framesize
         Emit a warning if the current function exceeds the given
         frame size.  Because this is a compile-time check it
         doesn't need to be a real problem when the program runs.
         It is intended to identify functions that most probably
         cause a stack overflow.  It is useful to be used in an
         environment with limited stack size e.g. the linux
         kernel.

     -mwarn-dynamicstack
         Emit a warning if the function calls "alloca" or uses
         dynamically-sized arrays.  This is generally a bad idea
         with a limited stack size.

     -mstack-guard=stack-guard
     -mstack-size=stack-size
         If these options are provided the S/390 back end emits
         additional instructions in the function prologue that
         trigger a trap if the stack size is stack-guard bytes
         above the stack-size (remember that the stack on S/390
         grows downward).  If the stack-guard option is omitted
         the smallest power of 2 larger than the frame size of
         the compiled function is chosen.  These options are
         intended to be used to help debugging stack overflow
         problems.  The additionally emitted code causes only
         little overhead and hence can also be used in
         production-like systems without greater performance
         degradation.  The given values have to be exact powers
         of 2 and stack-size has to be greater than stack-guard
         without exceeding 64k.  In order to be efficient the
         extra code makes the assumption that the stack starts at
         an address aligned to the value given by stack-size.
         The stack-guard option can only be used in conjunction
         with stack-size.

     Score Options

     These options are defined for Score implementations:

     -meb
         Compile code for big-endian mode.  This is the default.

     -mel
         Compile code for little-endian mode.

     -mnhwloop
         Disable generation of "bcnz" instructions.

     -muls
         Enable generation of unaligned load and store
         instructions.

     -mmac
         Enable the use of multiply-accumulate instructions.
         Disabled by default.

     -mscore5

         Specify the SCORE5 as the target architecture.

     -mscore5u
         Specify the SCORE5U of the target architecture.

     -mscore7
         Specify the SCORE7 as the target architecture. This is
         the default.

     -mscore7d
         Specify the SCORE7D as the target architecture.

     SH Options

     These -m options are defined for the SH implementations:

     -m1 Generate code for the SH1.

     -m2 Generate code for the SH2.

     -m2e
         Generate code for the SH2e.

     -m2a-nofpu
         Generate code for the SH2a without FPU, or for a
         SH2a-FPU in such a way that the floating-point unit is
         not used.

     -m2a-single-only
         Generate code for the SH2a-FPU, in such a way that no
         double-precision floating-point operations are used.

     -m2a-single
         Generate code for the SH2a-FPU assuming the floating-
         point unit is in single-precision mode by default.

     -m2a
         Generate code for the SH2a-FPU assuming the floating-
         point unit is in double-precision mode by default.

     -m3 Generate code for the SH3.

     -m3e
         Generate code for the SH3e.

     -m4-nofpu
         Generate code for the SH4 without a floating-point unit.

     -m4-single-only
         Generate code for the SH4 with a floating-point unit
         that only supports single-precision arithmetic.

     -m4-single
         Generate code for the SH4 assuming the floating-point
         unit is in single-precision mode by default.

     -m4 Generate code for the SH4.

     -m4a-nofpu
         Generate code for the SH4al-dsp, or for a SH4a in such a
         way that the floating-point unit is not used.

     -m4a-single-only
         Generate code for the SH4a, in such a way that no
         double-precision floating-point operations are used.

     -m4a-single
         Generate code for the SH4a assuming the floating-point
         unit is in single-precision mode by default.

     -m4a
         Generate code for the SH4a.

     -m4al
         Same as -m4a-nofpu, except that it implicitly passes
         -dsp to the assembler.  GCC doesn't generate any DSP
         instructions at the moment.

     -mb Compile code for the processor in big-endian mode.

     -ml Compile code for the processor in little-endian mode.

     -mdalign
         Align doubles at 64-bit boundaries.  Note that this
         changes the calling conventions, and thus some functions
         from the standard C library do not work unless you
         recompile it first with -mdalign.

     -mrelax
         Shorten some address references at link time, when
         possible; uses the linker option -relax.

     -mbigtable
         Use 32-bit offsets in "switch" tables.  The default is
         to use 16-bit offsets.

     -mbitops
         Enable the use of bit manipulation instructions on SH2A.

     -mfmovd
         Enable the use of the instruction "fmovd".  Check
         -mdalign for alignment constraints.

     -mhitachi

         Comply with the calling conventions defined by Renesas.

     -mrenesas
         Comply with the calling conventions defined by Renesas.

     -mno-renesas
         Comply with the calling conventions defined for GCC
         before the Renesas conventions were available.  This
         option is the default for all targets of the SH
         toolchain.

     -mnomacsave
         Mark the "MAC" register as call-clobbered, even if
         -mhitachi is given.

     -mieee
     -mno-ieee
         Control the IEEE compliance of floating-point
         comparisons, which affects the handling of cases where
         the result of a comparison is unordered.  By default
         -mieee is implicitly enabled.  If -ffinite-math-only is
         enabled -mno-ieee is implicitly set, which results in
         faster floating-point greater-equal and less-equal
         comparisons.  The implcit settings can be overridden by
         specifying either -mieee or -mno-ieee.

     -minline-ic_invalidate
         Inline code to invalidate instruction cache entries
         after setting up nested function trampolines.  This
         option has no effect if -musermode is in effect and the
         selected code generation option (e.g. -m4) does not
         allow the use of the "icbi" instruction.  If the
         selected code generation option does not allow the use
         of the "icbi" instruction, and -musermode is not in
         effect, the inlined code manipulates the instruction
         cache address array directly with an associative write.
         This not only requires privileged mode at run time, but
         it also fails if the cache line had been mapped via the
         TLB and has become unmapped.

     -misize
         Dump instruction size and location in the assembly code.

     -mpadstruct
         This option is deprecated.  It pads structures to
         multiple of 4 bytes, which is incompatible with the SH
         ABI.

     -matomic-model=model
         Sets the model of atomic operations and additional
         parameters as a comma separated list.  For details on
         the atomic built-in functions see __atomic Builtins.

         The following models and parameters are supported:

         none
             Disable compiler generated atomic sequences and emit
             library calls for atomic operations.  This is the
             default if the target is not "sh-*-linux*".

         soft-gusa
             Generate GNU/Linux compatible gUSA software atomic
             sequences for the atomic built-in functions.  The
             generated atomic sequences require additional
             support from the interrupt/exception handling code
             of the system and are only suitable for SH3* and
             SH4* single-core systems.  This option is enabled by
             default when the target is "sh-*-linux*" and SH3* or
             SH4*.  When the target is SH4A, this option will
             also partially utilize the hardware atomic
             instructions "movli.l" and "movco.l" to create more
             efficient code, unless strict is specified.

         soft-tcb
             Generate software atomic sequences that use a
             variable in the thread control block.  This is a
             variation of the gUSA sequences which can also be
             used on SH1* and SH2* targets.  The generated atomic
             sequences require additional support from the
             interrupt/exception handling code of the system and
             are only suitable for single-core systems.  When
             using this model, the gbr-offset= parameter has to
             be specified as well.

         soft-imask
             Generate software atomic sequences that temporarily
             disable interrupts by setting "SR.IMASK = 1111".
             This model works only when the program runs in
             privileged mode and is only suitable for single-core
             systems.  Additional support from the
             interrupt/exception handling code of the system is
             not required.  This model is enabled by default when
             the target is "sh-*-linux*" and SH1* or SH2*.

         hard-llcs
             Generate hardware atomic sequences using the
             "movli.l" and "movco.l" instructions only.  This is
             only available on SH4A and is suitable for multi-
             core systems.  Since the hardware instructions
             support only 32 bit atomic variables access to 8 or
             16 bit variables is emulated with 32 bit accesses.
             Code compiled with this option will also be
             compatible with other software atomic model
             interrupt/exception handling systems if executed on
             an SH4A system.  Additional support from the
             interrupt/exception handling code of the system is
             not required for this model.

         gbr-offset=
             This parameter specifies the offset in bytes of the
             variable in the thread control block structure that
             should be used by the generated atomic sequences
             when the soft-tcb model has been selected.  For
             other models this parameter is ignored.  The
             specified value must be an integer multiple of four
             and in the range 0-1020.

         strict
             This parameter prevents mixed usage of multiple
             atomic models, even though they would be compatible,
             and will make the compiler generate atomic sequences
             of the specified model only.

     -mtas
         Generate the "tas.b" opcode for "__atomic_test_and_set".
         Notice that depending on the particular hardware and
         software configuration this can degrade overall
         performance due to the operand cache line flushes that
         are implied by the "tas.b" instruction.  On multi-core
         SH4A processors the "tas.b" instruction must be used
         with caution since it can result in data corruption for
         certain cache configurations.

     -mspace
         Optimize for space instead of speed.  Implied by -Os.

     -mprefergot
         When generating position-independent code, emit function
         calls using the Global Offset Table instead of the
         Procedure Linkage Table.

     -musermode
         Don't generate privileged mode only code.  This option
         implies -mno-inline-ic_invalidate if the inlined code
         would not work in user mode.  This is the default when
         the target is "sh-*-linux*".

     -multcost=number
         Set the cost to assume for a multiply insn.

     -mdiv=strategy
         Set the division strategy to be used for integer
         division operations.  For SHmedia strategy can be one
         of:

         fp  Performs the operation in floating point.  This has
             a very high latency, but needs only a few
             instructions, so it might be a good choice if your
             code has enough easily-exploitable ILP to allow the
             compiler to schedule the floating-point instructions
             together with other instructions.  Division by zero
             causes a floating-point exception.

         inv Uses integer operations to calculate the inverse of
             the divisor, and then multiplies the dividend with
             the inverse.  This strategy allows CSE and hoisting
             of the inverse calculation.  Division by zero
             calculates an unspecified result, but does not trap.

         inv:minlat
             A variant of inv where, if no CSE or hoisting
             opportunities have been found, or if the entire
             operation has been hoisted to the same place, the
             last stages of the inverse calculation are
             intertwined with the final multiply to reduce the
             overall latency, at the expense of using a few more
             instructions, and thus offering fewer scheduling
             opportunities with other code.

         call
             Calls a library function that usually implements the
             inv:minlat strategy.  This gives high code density
             for "m5-*media-nofpu" compilations.

         call2
             Uses a different entry point of the same library
             function, where it assumes that a pointer to a
             lookup table has already been set up, which exposes
             the pointer load to CSE and code hoisting
             optimizations.

         inv:call
         inv:call2
         inv:fp
             Use the inv algorithm for initial code generation,
             but if the code stays unoptimized, revert to the
             call, call2, or fp strategies, respectively.  Note
             that the potentially-trapping side effect of
             division by zero is carried by a separate
             instruction, so it is possible that all the integer
             instructions are hoisted out, but the marker for the
             side effect stays where it is.  A recombination to
             floating-point operations or a call is not possible
             in that case.

         inv20u
         inv20l
             Variants of the inv:minlat strategy.  In the case
             that the inverse calculation is not separated from
             the multiply, they speed up division where the
             dividend fits into 20 bits (plus sign where
             applicable) by inserting a test to skip a number of
             operations in this case; this test slows down the
             case of larger dividends.  inv20u assumes the case
             of a such a small dividend to be unlikely, and
             inv20l assumes it to be likely.

         For targets other than SHmedia strategy can be one of:

         call-div1
             Calls a library function that uses the single-step
             division instruction "div1" to perform the
             operation.  Division by zero calculates an
             unspecified result and does not trap.  This is the
             default except for SH4, SH2A and SHcompact.

         call-fp
             Calls a library function that performs the operation
             in double precision floating point.  Division by
             zero causes a floating-point exception.  This is the
             default for SHcompact with FPU.  Specifying this for
             targets that do not have a double precision FPU will
             default to "call-div1".

         call-table
             Calls a library function that uses a lookup table
             for small divisors and the "div1" instruction with
             case distinction for larger divisors.  Division by
             zero calculates an unspecified result and does not
             trap.  This is the default for SH4.  Specifying this
             for targets that do not have dynamic shift
             instructions will default to "call-div1".

         When a division strategy has not been specified the
         default strategy will be selected based on the current
         target.  For SH2A the default strategy is to use the
         "divs" and "divu" instructions instead of library
         function calls.

     -maccumulate-outgoing-args
         Reserve space once for outgoing arguments in the
         function prologue rather than around each call.
         Generally beneficial for performance and size.  Also
         needed for unwinding to avoid changing the stack frame
         around conditional code.

     -mdivsi3_libfunc=name
         Set the name of the library function used for 32-bit
         signed division to name.  This only affects the name
         used in the call and inv:call division strategies, and
         the compiler still expects the same sets of
         input/output/clobbered registers as if this option were
         not present.

     -mfixed-range=register-range
         Generate code treating the given register range as fixed
         registers.  A fixed register is one that the register
         allocator can not use.  This is useful when compiling
         kernel code.  A register range is specified as two
         registers separated by a dash.  Multiple register ranges
         can be specified separated by a comma.

     -mindexed-addressing
         Enable the use of the indexed addressing mode for
         SHmedia32/SHcompact.  This is only safe if the hardware
         and/or OS implement 32-bit wrap-around semantics for the
         indexed addressing mode.  The architecture allows the
         implementation of processors with 64-bit MMU, which the
         OS could use to get 32-bit addressing, but since no
         current hardware implementation supports this or any
         other way to make the indexed addressing mode safe to
         use in the 32-bit ABI, the default is
         -mno-indexed-addressing.

     -mgettrcost=number
         Set the cost assumed for the "gettr" instruction to
         number.  The default is 2 if -mpt-fixed is in effect,
         100 otherwise.

     -mpt-fixed
         Assume "pt*" instructions won't trap.  This generally
         generates better-scheduled code, but is unsafe on
         current hardware.  The current architecture definition
         says that "ptabs" and "ptrel" trap when the target anded
         with 3 is 3.  This has the unintentional effect of
         making it unsafe to schedule these instructions before a
         branch, or hoist them out of a loop.  For example,
         "__do_global_ctors", a part of libgcc that runs
         constructors at program startup, calls functions in a
         list which is delimited by -1.  With the -mpt-fixed
         option, the "ptabs" is done before testing against -1.
         That means that all the constructors run a bit more
         quickly, but when the loop comes to the end of the list,
         the program crashes because "ptabs" loads -1 into a
         target register.

         Since this option is unsafe for any hardware
         implementing the current architecture specification, the
         default is -mno-pt-fixed.  Unless specified explicitly
         with -mgettrcost, -mno-pt-fixed also implies
         -mgettrcost=100; this deters register allocation from
         using target registers for storing ordinary integers.

     -minvalid-symbols
         Assume symbols might be invalid.  Ordinary function
         symbols generated by the compiler are always valid to
         load with "movi"/"shori"/"ptabs" or
         "movi"/"shori"/"ptrel", but with assembler and/or linker
         tricks it is possible to generate symbols that cause
         "ptabs" or "ptrel" to trap.  This option is only
         meaningful when -mno-pt-fixed is in effect.  It prevents
         cross-basic-block CSE, hoisting and most scheduling of
         symbol loads.  The default is -mno-invalid-symbols.

     -mbranch-cost=num
         Assume num to be the cost for a branch instruction.
         Higher numbers make the compiler try to generate more
         branch-free code if possible. If not specified the value
         is selected depending on the processor type that is
         being compiled for.

     -mzdcbranch
     -mno-zdcbranch
         Assume (do not assume) that zero displacement
         conditional branch instructions "bt" and "bf" are fast.
         If -mzdcbranch is specified, the compiler will try to
         prefer zero displacement branch code sequences.  This is
         enabled by default when generating code for SH4 and
         SH4A.  It can be explicitly disabled by specifying
         -mno-zdcbranch.

     -mcbranchdi
         Enable the "cbranchdi4" instruction pattern.

     -mcmpeqdi
         Emit the "cmpeqdi_t" instruction pattern even when
         -mcbranchdi is in effect.

     -mfused-madd
     -mno-fused-madd
         Generate code that uses (does not use) the floating-
         point multiply and accumulate instructions.  These
         instructions are generated by default if hardware
         floating point is used.  The machine-dependent
         -mfused-madd option is now mapped to the machine-
         independent -ffp-contract=fast option, and
         -mno-fused-madd is mapped to -ffp-contract=off.

     -mfsca
     -mno-fsca
         Allow or disallow the compiler to emit the "fsca"
         instruction for sine and cosine approximations.  The
         option "-mfsca" must be used in combination with
         "-funsafe-math-optimizations".  It is enabled by default
         when generating code for SH4A.  Using "-mno-fsca"
         disables sine and cosine approximations even if
         "-funsafe-math-optimizations" is in effect.

     -mfsrra
     -mno-fsrra
         Allow or disallow the compiler to emit the "fsrra"
         instruction for reciprocal square root approximations.
         The option "-mfsrra" must be used in combination with
         "-funsafe-math-optimizations" and "-ffinite-math-only".
         It is enabled by default when generating code for SH4A.
         Using "-mno-fsrra" disables reciprocal square root
         approximations even if "-funsafe-math-optimizations" and
         "-ffinite-math-only" are in effect.

     -mpretend-cmove
         Prefer zero-displacement conditional branches for
         conditional move instruction patterns.  This can result
         in faster code on the SH4 processor.

     Solaris 2 Options

     These -m options are supported on Solaris 2:

     -mimpure-text
         -mimpure-text, used in addition to -shared, tells the
         compiler to not pass -z text to the linker when linking
         a shared object.  Using this option, you can link
         position-dependent code into a shared object.

         -mimpure-text suppresses the "relocations remain against
         allocatable but non-writable sections" linker error
         message.  However, the necessary relocations trigger
         copy-on-write, and the shared object is not actually
         shared across processes.  Instead of using
         -mimpure-text, you should compile all source code with
         -fpic or -fPIC.

     These switches are supported in addition to the above on
     Solaris 2:

     -pthreads
         Add support for multithreading using the POSIX threads
         library.  This option sets flags for both the
         preprocessor and linker.  This option does not affect
         the thread safety of object code produced  by the
         compiler or that of libraries supplied with it.

     -pthread
         This is a synonym for -pthreads.

     SPARC Options

     These -m options are supported on the SPARC:

     -mno-app-regs
     -mapp-regs
         Specify -mapp-regs to generate output using the global
         registers 2 through 4, which the SPARC SVR4 ABI reserves
         for applications.  This is the default.

         To be fully SVR4 ABI-compliant at the cost of some
         performance loss, specify -mno-app-regs.  You should
         compile libraries and system software with this option.

     -mflat
     -mno-flat
         With -mflat, the compiler does not generate save/restore
         instructions and uses a "flat" or single register window
         model.  This model is compatible with the regular
         register window model.  The local registers and the
         input registers (0--5) are still treated as "call-saved"
         registers and are saved on the stack as needed.

         With -mno-flat (the default), the compiler generates
         save/restore instructions (except for leaf functions).
         This is the normal operating mode.

     -mfpu
     -mhard-float
         Generate output containing floating-point instructions.
         This is the default.

     -mno-fpu
     -msoft-float
         Generate output containing library calls for floating
         point.  Warning: the requisite libraries are not
         available for all SPARC targets.  Normally the
         facilities of the machine's usual C compiler are used,
         but this cannot be done directly in cross-compilation.
         You must make your own arrangements to provide suitable
         library functions for cross-compilation.  The embedded
         targets sparc-*-aout and sparclite-*-* do provide
         software floating-point support.

         -msoft-float changes the calling convention in the
         output file; therefore, it is only useful if you compile
         all of a program with this option.  In particular, you
         need to compile libgcc.a, the library that comes with
         GCC, with -msoft-float in order for this to work.

     -mhard-quad-float
         Generate output containing quad-word (long double)
         floating-point instructions.

     -msoft-quad-float
         Generate output containing library calls for quad-word
         (long double) floating-point instructions.  The
         functions called are those specified in the SPARC ABI.
         This is the default.

         As of this writing, there are no SPARC implementations
         that have hardware support for the quad-word floating-
         point instructions.  They all invoke a trap handler for
         one of these instructions, and then the trap handler
         emulates the effect of the instruction.  Because of the
         trap handler overhead, this is much slower than calling
         the ABI library routines.  Thus the -msoft-quad-float
         option is the default.

     -mno-unaligned-doubles
     -munaligned-doubles
         Assume that doubles have 8-byte alignment.  This is the
         default.

         With -munaligned-doubles, GCC assumes that doubles have
         8-byte alignment only if they are contained in another
         type, or if they have an absolute address.  Otherwise,
         it assumes they have 4-byte alignment.  Specifying this
         option avoids some rare compatibility problems with code
         generated by other compilers.  It is not the default
         because it results in a performance loss, especially for
         floating-point code.

     -mno-faster-structs
     -mfaster-structs
         With -mfaster-structs, the compiler assumes that
         structures should have 8-byte alignment.  This enables
         the use of pairs of "ldd" and "std" instructions for
         copies in structure assignment, in place of twice as
         many "ld" and "st" pairs.  However, the use of this
         changed alignment directly violates the SPARC ABI.
         Thus, it's intended only for use on targets where the
         developer acknowledges that their resulting code is not
         directly in line with the rules of the ABI.

     -mcpu=cpu_type
         Set the instruction set, register set, and instruction
         scheduling parameters for machine type cpu_type.
         Supported values for cpu_type are v7, cypress, v8,
         supersparc, hypersparc, leon, sparclite, f930, f934,
         sparclite86x, sparclet, tsc701, v9, ultrasparc,
         ultrasparc3, niagara, niagara2, niagara3, and niagara4.

         Native Solaris and GNU/Linux toolchains also support the
         value native, which selects the best architecture option
         for the host processor.  -mcpu=native has no effect if

         GCC does not recognize the processor.

         Default instruction scheduling parameters are used for
         values that select an architecture and not an
         implementation.  These are v7, v8, sparclite, sparclet,
         v9.

         Here is a list of each supported architecture and their
         supported implementations.

         v7  cypress

         v8  supersparc, hypersparc, leon

         sparclite
             f930, f934, sparclite86x

         sparclet
             tsc701

         v9  ultrasparc, ultrasparc3, niagara, niagara2,
             niagara3, niagara4

         By default (unless configured otherwise), GCC generates
         code for the V7 variant of the SPARC architecture.  With
         -mcpu=cypress, the compiler additionally optimizes it
         for the Cypress CY7C602 chip, as used in the
         SPARCStation/SPARCServer 3xx series.  This is also
         appropriate for the older SPARCStation 1, 2, IPX etc.

         With -mcpu=v8, GCC generates code for the V8 variant of
         the SPARC architecture.  The only difference from V7
         code is that the compiler emits the integer multiply and
         integer divide instructions which exist in SPARC-V8 but
         not in SPARC-V7.  With -mcpu=supersparc, the compiler
         additionally optimizes it for the SuperSPARC chip, as
         used in the SPARCStation 10, 1000 and 2000 series.

         With -mcpu=sparclite, GCC generates code for the
         SPARClite variant of the SPARC architecture.  This adds
         the integer multiply, integer divide step and scan
         ("ffs") instructions which exist in SPARClite but not in
         SPARC-V7.  With -mcpu=f930, the compiler additionally
         optimizes it for the Fujitsu MB86930 chip, which is the
         original SPARClite, with no FPU.  With -mcpu=f934, the
         compiler additionally optimizes it for the Fujitsu
         MB86934 chip, which is the more recent SPARClite with
         FPU.

         With -mcpu=sparclet, GCC generates code for the SPARClet
         variant of the SPARC architecture.  This adds the
         integer multiply, multiply/accumulate, integer divide
         step and scan ("ffs") instructions which exist in
         SPARClet but not in SPARC-V7.  With -mcpu=tsc701, the
         compiler additionally optimizes it for the TEMIC
         SPARClet chip.

         With -mcpu=v9, GCC generates code for the V9 variant of
         the SPARC architecture.  This adds 64-bit integer and
         floating-point move instructions, 3 additional
         floating-point condition code registers and conditional
         move instructions.  With -mcpu=ultrasparc, the compiler
         additionally optimizes it for the Sun UltraSPARC
         I/II/IIi chips.  With -mcpu=ultrasparc3, the compiler
         additionally optimizes it for the Sun UltraSPARC
         III/III+/IIIi/IIIi+/IV/IV+ chips.  With -mcpu=niagara,
         the compiler additionally optimizes it for Sun
         UltraSPARC T1 chips.  With -mcpu=niagara2, the compiler
         additionally optimizes it for Sun UltraSPARC T2 chips.
         With -mcpu=niagara3, the compiler additionally optimizes
         it for Sun UltraSPARC T3 chips.  With -mcpu=niagara4,
         the compiler additionally optimizes it for Sun
         UltraSPARC T4 chips.

     -mtune=cpu_type
         Set the instruction scheduling parameters for machine
         type cpu_type, but do not set the instruction set or
         register set that the option -mcpu=cpu_type does.

         The same values for -mcpu=cpu_type can be used for
         -mtune=cpu_type, but the only useful values are those
         that select a particular CPU implementation.  Those are
         cypress, supersparc, hypersparc, leon, f930, f934,
         sparclite86x, tsc701, ultrasparc, ultrasparc3, niagara,
         niagara2, niagara3 and niagara4.  With native Solaris
         and GNU/Linux toolchains, native can also be used.

     -mv8plus
     -mno-v8plus
         With -mv8plus, GCC generates code for the SPARC-V8+ ABI.
         The difference from the V8 ABI is that the global and
         out registers are considered 64 bits wide.  This is
         enabled by default on Solaris in 32-bit mode for all
         SPARC-V9 processors.

     -mvis
     -mno-vis
         With -mvis, GCC generates code that takes advantage of
         the UltraSPARC Visual Instruction Set extensions.  The
         default is -mno-vis.

     -mvis2
     -mno-vis2
         With -mvis2, GCC generates code that takes advantage of
         version 2.0 of the UltraSPARC Visual Instruction Set
         extensions.  The default is -mvis2 when targeting a cpu
         that supports such instructions, such as UltraSPARC-III
         and later.  Setting -mvis2 also sets -mvis.

     -mvis3
     -mno-vis3
         With -mvis3, GCC generates code that takes advantage of
         version 3.0 of the UltraSPARC Visual Instruction Set
         extensions.  The default is -mvis3 when targeting a cpu
         that supports such instructions, such as niagara-3 and
         later.  Setting -mvis3 also sets -mvis2 and -mvis.

     -mcbcond
     -mno-cbcond
         With -mcbcond, GCC generates code that takes advantage
         of compare-and-branch instructions, as defined in the
         Sparc Architecture 2011.  The default is -mcbcond when
         targeting a cpu that supports such instructions, such as
         niagara-4 and later.

     -mpopc
     -mno-popc
         With -mpopc, GCC generates code that takes advantage of
         the UltraSPARC population count instruction.  The
         default is -mpopc when targeting a cpu that supports
         such instructions, such as Niagara-2 and later.

     -mfmaf
     -mno-fmaf
         With -mfmaf, GCC generates code that takes advantage of
         the UltraSPARC Fused Multiply-Add Floating-point
         extensions.  The default is -mfmaf when targeting a cpu
         that supports such instructions, such as Niagara-3 and
         later.

     -mfix-at697f
         Enable the documented workaround for the single erratum
         of the Atmel AT697F processor (which corresponds to
         erratum #13 of the AT697E processor).

     These -m options are supported in addition to the above on
     SPARC-V9 processors in 64-bit environments:

     -m32
     -m64
         Generate code for a 32-bit or 64-bit environment.  The
         32-bit environment sets int, long and pointer to 32
         bits.  The 64-bit environment sets int to 32 bits and
         long and pointer to 64 bits.

     -mcmodel=which

         Set the code model to one of

         medlow
             The Medium/Low code model: 64-bit addresses,
             programs must be linked in the low 32 bits of
             memory.  Programs can be statically or dynamically
             linked.

         medmid
             The Medium/Middle code model: 64-bit addresses,
             programs must be linked in the low 44 bits of
             memory, the text and data segments must be less than
             2GB in size and the data segment must be located
             within 2GB of the text segment.

         medany
             The Medium/Anywhere code model: 64-bit addresses,
             programs may be linked anywhere in memory, the text
             and data segments must be less than 2GB in size and
             the data segment must be located within 2GB of the
             text segment.

         embmedany
             The Medium/Anywhere code model for embedded systems:
             64-bit addresses, the text and data segments must be
             less than 2GB in size, both starting anywhere in
             memory (determined at link time).  The global
             register %g4 points to the base of the data segment.
             Programs are statically linked and PIC is not
             supported.

     -mmemory-model=mem-model
         Set the memory model in force on the processor to one of

         default
             The default memory model for the processor and
             operating system.

         rmo Relaxed Memory Order

         pso Partial Store Order

         tso Total Store Order

         sc  Sequential Consistency

         These memory models are formally defined in Appendix D
         of the Sparc V9 architecture manual, as set in the
         processor's "PSTATE.MM" field.

     -mstack-bias
     -mno-stack-bias

         With -mstack-bias, GCC assumes that the stack pointer,
         and frame pointer if present, are offset by -2047 which
         must be added back when making stack frame references.
         This is the default in 64-bit mode.  Otherwise, assume
         no such offset is present.

     SPU Options

     These -m options are supported on the SPU:

     -mwarn-reloc
     -merror-reloc
         The loader for SPU does not handle dynamic relocations.
         By default, GCC gives an error when it generates code
         that requires a dynamic relocation.  -mno-error-reloc
         disables the error, -mwarn-reloc generates a warning
         instead.

     -msafe-dma
     -munsafe-dma
         Instructions that initiate or test completion of DMA
         must not be reordered with respect to loads and stores
         of the memory that is being accessed.  With -munsafe-dma
         you must use the "volatile" keyword to protect memory
         accesses, but that can lead to inefficient code in
         places where the memory is known to not change.  Rather
         than mark the memory as volatile, you can use -msafe-dma
         to tell the compiler to treat the DMA instructions as
         potentially affecting all memory.

     -mbranch-hints
         By default, GCC generates a branch hint instruction to
         avoid pipeline stalls for always-taken or probably-taken
         branches.  A hint is not generated closer than 8
         instructions away from its branch.  There is little
         reason to disable them, except for debugging purposes,
         or to make an object a little bit smaller.

     -msmall-mem
     -mlarge-mem
         By default, GCC generates code assuming that addresses
         are never larger than 18 bits.  With -mlarge-mem code is
         generated that assumes a full 32-bit address.

     -mstdmain
         By default, GCC links against startup code that assumes
         the SPU-style main function interface (which has an
         unconventional parameter list).  With -mstdmain, GCC
         links your program against startup code that assumes a
         C99-style interface to "main", including a local copy of
         "argv" strings.

     -mfixed-range=register-range
         Generate code treating the given register range as fixed
         registers.  A fixed register is one that the register
         allocator cannot use.  This is useful when compiling
         kernel code.  A register range is specified as two
         registers separated by a dash.  Multiple register ranges
         can be specified separated by a comma.

     -mea32
     -mea64
         Compile code assuming that pointers to the PPU address
         space accessed via the "__ea" named address space
         qualifier are either 32 or 64 bits wide.  The default is
         32 bits.  As this is an ABI-changing option, all object
         code in an executable must be compiled with the same
         setting.

     -maddress-space-conversion
     -mno-address-space-conversion
         Allow/disallow treating the "__ea" address space as
         superset of the generic address space.  This enables
         explicit type casts between "__ea" and generic pointer
         as well as implicit conversions of generic pointers to
         "__ea" pointers.  The default is to allow address space
         pointer conversions.

     -mcache-size=cache-size
         This option controls the version of libgcc that the
         compiler links to an executable and selects a software-
         managed cache for accessing variables in the "__ea"
         address space with a particular cache size.  Possible
         options for cache-size are 8, 16, 32, 64 and 128.  The
         default cache size is 64KB.

     -matomic-updates
     -mno-atomic-updates
         This option controls the version of libgcc that the
         compiler links to an executable and selects whether
         atomic updates to the software-managed cache of PPU-side
         variables are used.  If you use atomic updates, changes
         to a PPU variable from SPU code using the "__ea" named
         address space qualifier do not interfere with changes to
         other PPU variables residing in the same cache line from
         PPU code.  If you do not use atomic updates, such
         interference may occur; however, writing back cache
         lines is more efficient.  The default behavior is to use
         atomic updates.

     -mdual-nops
     -mdual-nops=n
         By default, GCC inserts nops to increase dual issue when
         it expects it to increase performance.  n can be a value
         from 0 to 10.  A smaller n inserts fewer nops.  10 is
         the default, 0 is the same as -mno-dual-nops.  Disabled
         with -Os.

     -mhint-max-nops=n
         Maximum number of nops to insert for a branch hint.  A
         branch hint must be at least 8 instructions away from
         the branch it is affecting.  GCC inserts up to n nops to
         enforce this, otherwise it does not generate the branch
         hint.

     -mhint-max-distance=n
         The encoding of the branch hint instruction limits the
         hint to be within 256 instructions of the branch it is
         affecting.  By default, GCC makes sure it is within 125.

     -msafe-hints
         Work around a hardware bug that causes the SPU to stall
         indefinitely.  By default, GCC inserts the "hbrp"
         instruction to make sure this stall won't happen.

     Options for System V

     These additional options are available on System V Release 4
     for compatibility with other compilers on those systems:

     -G  Create a shared object.  It is recommended that
         -symbolic or -shared be used instead.

     -Qy Identify the versions of each tool used by the compiler,
         in a ".ident" assembler directive in the output.

     -Qn Refrain from adding ".ident" directives to the output
         file (this is the default).

     -YP,dirs
         Search the directories dirs, and no others, for
         libraries specified with -l.

     -Ym,dir
         Look in the directory dir to find the M4 preprocessor.
         The assembler uses this option.

     TILE-Gx Options

     These -m options are supported on the TILE-Gx:

     -mcmodel=small
         Generate code for the small model.  The distance for
         direct calls is limited to 500M in either direction.
         PC-relative addresses are 32 bits.  Absolute addresses
         support the full address range.

     -mcmodel=large
         Generate code for the large model.  There is no
         limitation on call distance, pc-relative addresses, or
         absolute addresses.

     -mcpu=name
         Selects the type of CPU to be targeted.  Currently the
         only supported type is tilegx.

     -m32
     -m64
         Generate code for a 32-bit or 64-bit environment.  The
         32-bit environment sets int, long, and pointer to 32
         bits.  The 64-bit environment sets int to 32 bits and
         long and pointer to 64 bits.

     TILEPro Options

     These -m options are supported on the TILEPro:

     -mcpu=name
         Selects the type of CPU to be targeted.  Currently the
         only supported type is tilepro.

     -m32
         Generate code for a 32-bit environment, which sets int,
         long, and pointer to 32 bits.  This is the only
         supported behavior so the flag is essentially ignored.

     V850 Options

     These -m options are defined for V850 implementations:

     -mlong-calls
     -mno-long-calls
         Treat all calls as being far away (near).  If calls are
         assumed to be far away, the compiler always loads the
         function's address into a register, and calls indirect
         through the pointer.

     -mno-ep
     -mep
         Do not optimize (do optimize) basic blocks that use the
         same index pointer 4 or more times to copy pointer into
         the "ep" register, and use the shorter "sld" and "sst"
         instructions.  The -mep option is on by default if you
         optimize.

     -mno-prolog-function
     -mprolog-function
         Do not use (do use) external functions to save and
         restore registers at the prologue and epilogue of a
         function.  The external functions are slower, but use
         less code space if more than one function saves the same
         number of registers.  The -mprolog-function option is on
         by default if you optimize.

     -mspace
         Try to make the code as small as possible.  At present,
         this just turns on the -mep and -mprolog-function
         options.

     -mtda=n
         Put static or global variables whose size is n bytes or
         less into the tiny data area that register "ep" points
         to.  The tiny data area can hold up to 256 bytes in
         total (128 bytes for byte references).

     -msda=n
         Put static or global variables whose size is n bytes or
         less into the small data area that register "gp" points
         to.  The small data area can hold up to 64 kilobytes.

     -mzda=n
         Put static or global variables whose size is n bytes or
         less into the first 32 kilobytes of memory.

     -mv850
         Specify that the target processor is the V850.

     -mv850e3v5
         Specify that the target processor is the V850E3V5.  The
         preprocessor constant __v850e3v5__ is defined if this
         option is used.

     -mv850e2v4
         Specify that the target processor is the V850E3V5.  This
         is an alias for the -mv850e3v5 option.

     -mv850e2v3
         Specify that the target processor is the V850E2V3.  The
         preprocessor constant __v850e2v3__ is defined if this
         option is used.

     -mv850e2
         Specify that the target processor is the V850E2.  The
         preprocessor constant __v850e2__ is defined if this
         option is used.

     -mv850e1
         Specify that the target processor is the V850E1.  The
         preprocessor constants __v850e1__ and __v850e__ are
         defined if this option is used.

     -mv850es
         Specify that the target processor is the V850ES.  This
         is an alias for the -mv850e1 option.

     -mv850e
         Specify that the target processor is the V850E.  The
         preprocessor constant __v850e__ is defined if this
         option is used.

         If neither -mv850 nor -mv850e nor -mv850e1 nor -mv850e2
         nor -mv850e2v3 nor -mv850e3v5 are defined then a default
         target processor is chosen and the relevant __v850*__
         preprocessor constant is defined.

         The preprocessor constants __v850 and __v851__ are
         always defined, regardless of which processor variant is
         the target.

     -mdisable-callt
     -mno-disable-callt
         This option suppresses generation of the "CALLT"
         instruction for the v850e, v850e1, v850e2, v850e2v3 and
         v850e3v5 flavors of the v850 architecture.

         This option is enabled by default when the RH850 ABI is
         in use (see -mrh850-abi), and disabled by default when
         the GCC ABI is in use.  If "CALLT" instructions are
         being generated then the C preprocessor symbol
         "__V850_CALLT__" will be defined.

     -mrelax
     -mno-relax
         Pass on (or do not pass on) the -mrelax command line
         option to the assembler.

     -mlong-jumps
     -mno-long-jumps
         Disable (or re-enable) the generation of PC-relative
         jump instructions.

     -msoft-float
     -mhard-float
         Disable (or re-enable) the generation of hardware
         floating point instructions.  This option is only
         significant when the target architecture is V850E2V3 or
         higher.  If hardware floating point instructions are
         being generated then the C preprocessor symbol
         "__FPU_OK__" will be defined, otherwise the symbol
         "__NO_FPU__" will be defined.

     -mloop
         Enables the use of the e3v5 LOOP instruction.  The use
         of this instruction is not enabled by default when the
         e3v5 architecture is selected because its use is still
         experimental.

     -mrh850-abi
     -mghs
         Enables support for the RH850 version of the V850 ABI.
         This is the default.  With this version of the ABI the
         following rules apply:

         *   Integer sized structures and unions are returned via
             a memory pointer rather than a register.

         *   Large structures and unions (more than 8 bytes in
             size) are passed by value.

         *   Functions are aligned to 16-bit boundaries.

         *   The -m8byte-align command line option is supported.

         *   The -mdisable-callt command line option is enabled
             by default.  The -mno-disable-callt command line
             option is not supported.

         When this version of the ABI is enabled the C
         preprocessor symbol "__V850_RH850_ABI__" is defined.

     -mgcc-abi
         Enables support for the old GCC version of the V850 ABI.
         With this version of the ABI the following rules apply:

         *   Integer sized structures and unions are returned in
             register "r10".

         *   Large structures and unions (more than 8 bytes in
             size) are passed by reference.

         *   Functions are aligned to 32-bit boundaries, unless
             optimizing for size.

         *   The -m8byte-align command line option is not
             supported.

         *   The -mdisable-callt command line option is supported
             but not enabled by default.

         When this version of the ABI is enabled the C
         preprocessor symbol "__V850_GCC_ABI__" is defined.

     -m8byte-align
     -mno-8byte-align
         Enables support for "doubles" and "long long" types to
         be aligned on 8-byte boundaries.  The default is to
         restrict the alignment of all objects to at most
         4-bytes.  When -m8byte-align is in effect the C
         preprocessor symbol "__V850_8BYTE_ALIGN__" will be
         defined.

     -mbig-switch
         Generate code suitable for big switch tables.  Use this
         option only if the assembler/linker complain about out
         of range branches within a switch table.

     -mapp-regs
         This option causes r2 and r5 to be used in the code
         generated by the compiler.  This setting is the default.

     -mno-app-regs
         This option causes r2 and r5 to be treated as fixed
         registers.

     VAX Options

     These -m options are defined for the VAX:

     -munix
         Do not output certain jump instructions ("aobleq" and so
         on) that the Unix assembler for the VAX cannot handle
         across long ranges.

     -mgnu
         Do output those jump instructions, on the assumption
         that the GNU assembler is being used.

     -mg Output code for G-format floating-point numbers instead
         of D-format.

     VMS Options

     These -m options are defined for the VMS implementations:

     -mvms-return-codes
         Return VMS condition codes from "main". The default is
         to return POSIX-style condition (e.g. error) codes.

     -mdebug-main=prefix
         Flag the first routine whose name starts with prefix as
         the main routine for the debugger.

     -mmalloc64
         Default to 64-bit memory allocation routines.

     -mpointer-size=size
         Set the default size of pointers. Possible options for
         size are 32 or short for 32 bit pointers, 64 or long for
         64 bit pointers, and no for supporting only 32 bit
         pointers.  The later option disables "pragma
         pointer_size".

     VxWorks Options

     The options in this section are defined for all VxWorks
     targets.  Options specific to the target hardware are listed
     with the other options for that target.

     -mrtp
         GCC can generate code for both VxWorks kernels and real
         time processes (RTPs).  This option switches from the
         former to the latter.  It also defines the preprocessor
         macro "__RTP__".

     -non-static
         Link an RTP executable against shared libraries rather
         than static libraries.  The options -static and -shared
         can also be used for RTPs; -static is the default.

     -Bstatic
     -Bdynamic
         These options are passed down to the linker.  They are
         defined for compatibility with Diab.

     -Xbind-lazy
         Enable lazy binding of function calls.  This option is
         equivalent to -Wl,-z,now and is defined for
         compatibility with Diab.

     -Xbind-now
         Disable lazy binding of function calls.  This option is
         the default and is defined for compatibility with Diab.

     x86-64 Options

     These are listed under

     Xstormy16 Options

     These options are defined for Xstormy16:

     -msim
         Choose startup files and linker script suitable for the
         simulator.

     Xtensa Options

     These options are supported for Xtensa targets:
     -mconst16
     -mno-const16
         Enable or disable use of "CONST16" instructions for
         loading constant values.  The "CONST16" instruction is
         currently not a standard option from Tensilica.  When
         enabled, "CONST16" instructions are always used in place
         of the standard "L32R" instructions.  The use of
         "CONST16" is enabled by default only if the "L32R"
         instruction is not available.

     -mfused-madd
     -mno-fused-madd
         Enable or disable use of fused multiply/add and
         multiply/subtract instructions in the floating-point
         option.  This has no effect if the floating-point option
         is not also enabled.  Disabling fused multiply/add and
         multiply/subtract instructions forces the compiler to
         use separate instructions for the multiply and
         add/subtract operations.  This may be desirable in some
         cases where strict IEEE 754-compliant results are
         required: the fused multiply add/subtract instructions
         do not round the intermediate result, thereby producing
         results with more bits of precision than specified by
         the IEEE standard.  Disabling fused multiply
         add/subtract instructions also ensures that the program
         output is not sensitive to the compiler's ability to
         combine multiply and add/subtract operations.

     -mserialize-volatile
     -mno-serialize-volatile
         When this option is enabled, GCC inserts "MEMW"
         instructions before "volatile" memory references to
         guarantee sequential consistency.  The default is
         -mserialize-volatile.  Use -mno-serialize-volatile to
         omit the "MEMW" instructions.

     -mforce-no-pic
         For targets, like GNU/Linux, where all user-mode Xtensa
         code must be position-independent code (PIC), this
         option disables PIC for compiling kernel code.

     -mtext-section-literals
     -mno-text-section-literals
         Control the treatment of literal pools.  The default is
         -mno-text-section-literals, which places literals in a
         separate section in the output file.  This allows the
         literal pool to be placed in a data RAM/ROM, and it also
         allows the linker to combine literal pools from separate
         object files to remove redundant literals and improve
         code size.  With -mtext-section-literals, the literals
         are interspersed in the text section in order to keep
         them as close as possible to their references.  This may
         be necessary for large assembly files.

     -mtarget-align
     -mno-target-align
         When this option is enabled, GCC instructs the assembler
         to automatically align instructions to reduce branch
         penalties at the expense of some code density.  The
         assembler attempts to widen density instructions to
         align branch targets and the instructions following call
         instructions.  If there are not enough preceding safe
         density instructions to align a target, no widening is
         performed.  The default is -mtarget-align.  These
         options do not affect the treatment of auto-aligned
         instructions like "LOOP", which the assembler always
         aligns, either by widening density instructions or by
         inserting NOP instructions.

     -mlongcalls
     -mno-longcalls
         When this option is enabled, GCC instructs the assembler
         to translate direct calls to indirect calls unless it
         can determine that the target of a direct call is in the
         range allowed by the call instruction.  This translation
         typically occurs for calls to functions in other source
         files.  Specifically, the assembler translates a direct
         "CALL" instruction into an "L32R" followed by a "CALLX"
         instruction.  The default is -mno-longcalls.  This
         option should be used in programs where the call target
         can potentially be out of range.  This option is
         implemented in the assembler, not the compiler, so the
         assembly code generated by GCC still shows direct call
         instructions---look at the disassembled object code to
         see the actual instructions.  Note that the assembler
         uses an indirect call for every cross-file call, not
         just those that really are out of range.

     zSeries Options

     These are listed under

  Options for Code Generation Conventions
     These machine-independent options control the interface
     conventions used in code generation.

     Most of them have both positive and negative forms; the
     negative form of -ffoo is -fno-foo.  In the table below,
     only one of the forms is listed---the one that is not the
     default.  You can figure out the other form by either
     removing no- or adding it.

     -fbounds-check
         For front ends that support it, generate additional code
         to check that indices used to access arrays are within
         the declared range.  This is currently only supported by
         the Java and Fortran front ends, where this option
         defaults to true and false respectively.

     -fstack-reuse=reuse-level
         This option controls stack space reuse for user declared
         local/auto variables and compiler generated temporaries.
         reuse_level can be all, named_vars, or none. all enables
         stack reuse for all local variables and temporaries,
         named_vars enables the reuse only for user defined local
         variables with names, and none disables stack reuse
         completely. The default value is all. The option is
         needed when the program extends the lifetime of a scoped
         local variable or a compiler generated temporary beyond
         the end point defined by the language.  When a lifetime
         of a variable ends, and if the variable lives in memory,
         the optimizing compiler has the freedom to reuse its
         stack space with other temporaries or scoped local
         variables whose live range does not overlap with it.
         Legacy code extending local lifetime will likely to
         break with the stack reuse optimization.

         For example,

                    int *p;
                    {
                      int local1;

                      p = &local1;
                      local1 = 10;
                      ....
                    }
                    {
                       int local2;
                       local2 = 20;
                       ...
                    }

                    if (*p == 10)  // out of scope use of local1
                      {

                      }

         Another example:

                    struct A
                    {
                        A(int k) : i(k), j(k) { }
                        int i;
                        int j;
                    };

                    A *ap;

                    void foo(const A& ar)
                    {
                       ap = &ar;
                    }

                    void bar()
                    {
                       foo(A(10)); // temp object's lifetime ends when foo returns

                       {
                         A a(20);
                         ....
                       }
                       ap->i+= 10;  // ap references out of scope temp whose space
                                    // is reused with a. What is the value of ap->i?
                    }

         The lifetime of a compiler generated temporary is well
         defined by the C++ standard. When a lifetime of a
         temporary ends, and if the temporary lives in memory,
         the optimizing compiler has the freedom to reuse its
         stack space with other temporaries or scoped local
         variables whose live range does not overlap with it.
         However some of the legacy code relies on the behavior
         of older compilers in which temporaries' stack space is
         not reused, the aggressive stack reuse can lead to
         runtime errors. This option is used to control the
         temporary stack reuse optimization.

     -ftrapv
         This option generates traps for signed overflow on
         addition, subtraction, multiplication operations.

     -fwrapv
         This option instructs the compiler to assume that signed
         arithmetic overflow of addition, subtraction and
         multiplication wraps around using twos-complement
         representation.  This flag enables some optimizations
         and disables others.  This option is enabled by default
         for the Java front end, as required by the Java language
         specification.

     -fexceptions
         Enable exception handling.  Generates extra code needed
         to propagate exceptions.  For some targets, this implies
         GCC generates frame unwind information for all
         functions, which can produce significant data size
         overhead, although it does not affect execution.  If you
         do not specify this option, GCC enables it by default
         for languages like C++ that normally require exception
         handling, and disables it for languages like C that do
         not normally require it.  However, you may need to
         enable this option when compiling C code that needs to
         interoperate properly with exception handlers written in
         C++.  You may also wish to disable this option if you
         are compiling older C++ programs that don't use
         exception handling.

     -fnon-call-exceptions
         Generate code that allows trapping instructions to throw
         exceptions.  Note that this requires platform-specific
         runtime support that does not exist everywhere.
         Moreover, it only allows trapping instructions to throw
         exceptions, i.e. memory references or floating-point
         instructions.  It does not allow exceptions to be thrown
         from arbitrary signal handlers such as "SIGALRM".

     -fdelete-dead-exceptions
         Consider that instructions that may throw exceptions but
         don't otherwise contribute to the execution of the
         program can be optimized away.  This option is enabled
         by default for the Ada front end, as permitted by the
         Ada language specification.  Optimization passes that
         cause dead exceptions to be removed are enabled
         independently at different optimization levels.

     -funwind-tables
         Similar to -fexceptions, except that it just generates
         any needed static data, but does not affect the
         generated code in any other way.  You normally do not
         need to enable this option; instead, a language
         processor that needs this handling enables it on your
         behalf.

     -fasynchronous-unwind-tables
         Generate unwind table in DWARF 2 format, if supported by
         target machine.  The table is exact at each instruction
         boundary, so it can be used for stack unwinding from
         asynchronous events (such as debugger or garbage
         collector).

     -fpcc-struct-return
         Return "short" "struct" and "union" values in memory
         like longer ones, rather than in registers.  This
         convention is less efficient, but it has the advantage
         of allowing intercallability between GCC-compiled files
         and files compiled with other compilers, particularly
         the Portable C Compiler (pcc).

         The precise convention for returning structures in
         memory depends on the target configuration macros.

         Short structures and unions are those whose size and
         alignment match that of some integer type.

         Warning: code compiled with the -fpcc-struct-return
         switch is not binary compatible with code compiled with
         the -freg-struct-return switch.  Use it to conform to a
         non-default application binary interface.

     -freg-struct-return
         Return "struct" and "union" values in registers when
         possible.  This is more efficient for small structures
         than -fpcc-struct-return.

         If you specify neither -fpcc-struct-return nor
         -freg-struct-return, GCC defaults to whichever
         convention is standard for the target.  If there is no
         standard convention, GCC defaults to
         -fpcc-struct-return, except on targets where GCC is the
         principal compiler.  In those cases, we can choose the
         standard, and we chose the more efficient register
         return alternative.

         Warning: code compiled with the -freg-struct-return
         switch is not binary compatible with code compiled with
         the -fpcc-struct-return switch.  Use it to conform to a
         non-default application binary interface.

     -fshort-enums
         Allocate to an "enum" type only as many bytes as it
         needs for the declared range of possible values.
         Specifically, the "enum" type is equivalent to the
         smallest integer type that has enough room.

         Warning: the -fshort-enums switch causes GCC to generate
         code that is not binary compatible with code generated
         without that switch.  Use it to conform to a non-default
         application binary interface.

     -fshort-double
         Use the same size for "double" as for "float".

         Warning: the -fshort-double switch causes GCC to
         generate code that is not binary compatible with code
         generated without that switch.  Use it to conform to a
         non-default application binary interface.

     -fshort-wchar
         Override the underlying type for wchar_t to be short
         unsigned int instead of the default for the target.
         This option is useful for building programs to run under
         WINE.

         Warning: the -fshort-wchar switch causes GCC to generate
         code that is not binary compatible with code generated
         without that switch.  Use it to conform to a non-default
         application binary interface.

     -fno-common
         In C code, controls the placement of uninitialized
         global variables.  Unix C compilers have traditionally
         permitted multiple definitions of such variables in
         different compilation units by placing the variables in
         a common block.  This is the behavior specified by
         -fcommon, and is the default for GCC on most targets.
         On the other hand, this behavior is not required by ISO
         C, and on some targets may carry a speed or code size
         penalty on variable references.  The -fno-common option
         specifies that the compiler should place uninitialized
         global variables in the data section of the object file,
         rather than generating them as common blocks.  This has
         the effect that if the same variable is declared
         (without "extern") in two different compilations, you
         get a multiple-definition error when you link them.  In
         this case, you must compile with -fcommon instead.
         Compiling with -fno-common is useful on targets for
         which it provides better performance, or if you wish to
         verify that the program will work on other systems that
         always treat uninitialized variable declarations this
         way.

     -fno-ident
         Ignore the #ident directive.

     -finhibit-size-directive
         Don't output a ".size" assembler directive, or anything
         else that would cause trouble if the function is split
         in the middle, and the two halves are placed at
         locations far apart in memory.  This option is used when
         compiling crtstuff.c; you should not need to use it for
         anything else.

     -fverbose-asm
         Put extra commentary information in the generated
         assembly code to make it more readable.  This option is
         generally only of use to those who actually need to read
         the generated assembly code (perhaps while debugging the
         compiler itself).

         -fno-verbose-asm, the default, causes the extra
         information to be omitted and is useful when comparing
         two assembler files.

     -frecord-gcc-switches
         This switch causes the command line used to invoke the
         compiler to be recorded into the object file that is
         being created.  This switch is only implemented on some
         targets and the exact format of the recording is target
         and binary file format dependent, but it usually takes
         the form of a section containing ASCII text.  This
         switch is related to the -fverbose-asm switch, but that
         switch only records information in the assembler output
         file as comments, so it never reaches the object file.
         See also -grecord-gcc-switches for another way of
         storing compiler options into the object file.

     -fpic
         Generate position-independent code (PIC) suitable for
         use in a shared library, if supported for the target
         machine.  Such code accesses all constant addresses
         through a global offset table (GOT).  The dynamic loader
         resolves the GOT entries when the program starts (the
         dynamic loader is not part of GCC; it is part of the
         operating system).  If the GOT size for the linked
         executable exceeds a machine-specific maximum size, you
         get an error message from the linker indicating that
         -fpic does not work; in that case, recompile with -fPIC
         instead.  (These maximums are 8k on the SPARC and 32k on
         the m68k and RS/6000.  The 386 has no such limit.)

         Position-independent code requires special support, and
         therefore works only on certain machines.  For the 386,
         GCC supports PIC for System V but not for the Sun 386i.
         Code generated for the IBM RS/6000 is always position-
         independent.

         When this flag is set, the macros "__pic__" and
         "__PIC__" are defined to 1.

     -fPIC
         If supported for the target machine, emit position-
         independent code, suitable for dynamic linking and
         avoiding any limit on the size of the global offset
         table.  This option makes a difference on the m68k,
         PowerPC and SPARC.

         Position-independent code requires special support, and
         therefore works only on certain machines.

         When this flag is set, the macros "__pic__" and
         "__PIC__" are defined to 2.

     -fpie
     -fPIE
         These options are similar to -fpic and -fPIC, but
         generated position independent code can be only linked
         into executables.  Usually these options are used when
         -pie GCC option is used during linking.

         -fpie and -fPIE both define the macros "__pie__" and
         "__PIE__".  The macros have the value 1 for -fpie and 2
         for -fPIE.

     -fno-jump-tables
         Do not use jump tables for switch statements even where
         it would be more efficient than other code generation
         strategies.  This option is of use in conjunction with
         -fpic or -fPIC for building code that forms part of a
         dynamic linker and cannot reference the address of a
         jump table.  On some targets, jump tables do not require
         a GOT and this option is not needed.

     -ffixed-reg
         Treat the register named reg as a fixed register;
         generated code should never refer to it (except perhaps
         as a stack pointer, frame pointer or in some other fixed
         role).

         reg must be the name of a register.  The register names
         accepted are machine-specific and are defined in the
         "REGISTER_NAMES" macro in the machine description macro
         file.

         This flag does not have a negative form, because it
         specifies a three-way choice.

     -fcall-used-reg
         Treat the register named reg as an allocable register
         that is clobbered by function calls.  It may be
         allocated for temporaries or variables that do not live
         across a call.  Functions compiled this way do not save
         and restore the register reg.

         It is an error to use this flag with the frame pointer
         or stack pointer.  Use of this flag for other registers
         that have fixed pervasive roles in the machine's
         execution model produces disastrous results.

         This flag does not have a negative form, because it
         specifies a three-way choice.

     -fcall-saved-reg
         Treat the register named reg as an allocable register
         saved by functions.  It may be allocated even for
         temporaries or variables that live across a call.
         Functions compiled this way save and restore the
         register reg if they use it.

         It is an error to use this flag with the frame pointer
         or stack pointer.  Use of this flag for other registers
         that have fixed pervasive roles in the machine's
         execution model produces disastrous results.

         A different sort of disaster results from the use of
         this flag for a register in which function values may be
         returned.

         This flag does not have a negative form, because it
         specifies a three-way choice.

     -fpack-struct[=n]
         Without a value specified, pack all structure members
         together without holes.  When a value is specified
         (which must be a small power of two), pack structure
         members according to this value, representing the
         maximum alignment (that is, objects with default
         alignment requirements larger than this are output
         potentially unaligned at the next fitting location.

         Warning: the -fpack-struct switch causes GCC to generate
         code that is not binary compatible with code generated
         without that switch.  Additionally, it makes the code
         suboptimal.  Use it to conform to a non-default
         application binary interface.

     -finstrument-functions
         Generate instrumentation calls for entry and exit to
         functions.  Just after function entry and just before
         function exit, the following profiling functions are
         called with the address of the current function and its
         call site.  (On some platforms,
         "__builtin_return_address" does not work beyond the
         current function, so the call site information may not
         be available to the profiling functions otherwise.)

                 void __cyg_profile_func_enter (void *this_fn,
                                          void *call_site);
                 void __cyg_profile_func_exit  (void *this_fn,
                                          void *call_site);

         The first argument is the address of the start of the
         current function, which may be looked up exactly in the
         symbol table.

         This instrumentation is also done for functions expanded
         inline in other functions.  The profiling calls indicate
         where, conceptually, the inline function is entered and
         exited.  This means that addressable versions of such
         functions must be available.  If all your uses of a
         function are expanded inline, this may mean an
         additional expansion of code size.  If you use extern
         inline in your C code, an addressable version of such
         functions must be provided.  (This is normally the case
         anyway, but if you get lucky and the optimizer always
         expands the functions inline, you might have gotten away
         without providing static copies.)

         A function may be given the attribute
         "no_instrument_function", in which case this
         instrumentation is not done.  This can be used, for
         example, for the profiling functions listed above,
         high-priority interrupt routines, and any functions from
         which the profiling functions cannot safely be called
         (perhaps signal handlers, if the profiling routines
         generate output or allocate memory).

     -finstrument-functions-exclude-file-list=file,file,...
         Set the list of functions that are excluded from
         instrumentation (see the description of
         "-finstrument-functions").  If the file that contains a
         function definition matches with one of file, then that
         function is not instrumented.  The match is done on
         substrings:  if the file parameter is a substring of the
         file name, it is considered to be a match.

         For example:

                 -finstrument-functions-exclude-file-list=/bits/stl,include/sys

         excludes any inline function defined in files whose
         pathnames contain "/bits/stl" or "include/sys".

         If, for some reason, you want to include letter `,' in
         one of sym, write `,'. For example,
         "-finstrument-functions-exclude-file-list=',,tmp'" (note
         the single quote surrounding the option).

     -finstrument-functions-exclude-function-list=sym,sym,...
         This is similar to
         "-finstrument-functions-exclude-file-list", but this
         option sets the list of function names to be excluded
         from instrumentation.  The function name to be matched
         is its user-visible name, such as "vector<int>
         blah(const vector<int> &)", not the internal mangled
         name (e.g., "_Z4blahRSt6vectorIiSaIiEE").  The match is
         done on substrings: if the sym parameter is a substring
         of the function name, it is considered to be a match.
         For C99 and C++ extended identifiers, the function name
         must be given in UTF-8, not using universal character
         names.

     -fstack-check
         Generate code to verify that you do not go beyond the
         boundary of the stack.  You should specify this flag if
         you are running in an environment with multiple threads,
         but you only rarely need to specify it in a single-
         threaded environment since stack overflow is
         automatically detected on nearly all systems if there is
         only one stack.

         Note that this switch does not actually cause checking
         to be done; the operating system or the language runtime
         must do that.  The switch causes generation of code to
         ensure that they see the stack being extended.

         You can additionally specify a string parameter: "no"
         means no checking, "generic" means force the use of
         old-style checking, "specific" means use the best
         checking method and is equivalent to bare -fstack-check.

         Old-style checking is a generic mechanism that requires
         no specific target support in the compiler but comes
         with the following drawbacks:

         1.  Modified allocation strategy for large objects: they
             are always allocated dynamically if their size
             exceeds a fixed threshold.

         2.  Fixed limit on the size of the static frame of
             functions: when it is topped by a particular
             function, stack checking is not reliable and a
             warning is issued by the compiler.

         3.  Inefficiency: because of both the modified
             allocation strategy and the generic implementation,
             code performance is hampered.

         Note that old-style stack checking is also the fallback
         method for "specific" if no target support has been
         added in the compiler.

     -fstack-limit-register=reg
     -fstack-limit-symbol=sym
     -fno-stack-limit
         Generate code to ensure that the stack does not grow
         beyond a certain value, either the value of a register
         or the address of a symbol.  If a larger stack is
         required, a signal is raised at run time.  For most
         targets, the signal is raised before the stack overruns
         the boundary, so it is possible to catch the signal
         without taking special precautions.

         For instance, if the stack starts at absolute address
         0x80000000 and grows downwards, you can use the flags
         -fstack-limit-symbol=__stack_limit and
         -Wl,--defsym,__stack_limit=0x7ffe0000 to enforce a stack
         limit of 128KB.  Note that this may only work with the
         GNU linker.

     -fsplit-stack
         Generate code to automatically split the stack before it
         overflows.  The resulting program has a discontiguous
         stack which can only overflow if the program is unable
         to allocate any more memory.  This is most useful when
         running threaded programs, as it is no longer necessary
         to calculate a good stack size to use for each thread.
         This is currently only implemented for the i386 and
         x86_64 back ends running GNU/Linux.

         When code compiled with -fsplit-stack calls code
         compiled without -fsplit-stack, there may not be much
         stack space available for the latter code to run.  If
         compiling all code, including library code, with
         -fsplit-stack is not an option, then the linker can fix
         up these calls so that the code compiled without
         -fsplit-stack always has a large stack.  Support for
         this is implemented in the gold linker in GNU binutils
         release 2.21 and later.

     -fleading-underscore
         This option and its counterpart,
         -fno-leading-underscore, forcibly change the way C
         symbols are represented in the object file.  One use is
         to help link with legacy assembly code.

         Warning: the -fleading-underscore switch causes GCC to
         generate code that is not binary compatible with code
         generated without that switch.  Use it to conform to a
         non-default application binary interface.  Not all
         targets provide complete support for this switch.

     -ftls-model=model
         Alter the thread-local storage model to be used.  The
         model argument should be one of "global-dynamic",
         "local-dynamic", "initial-exec" or "local-exec".

         The default without -fpic is "initial-exec"; with -fpic
         the default is "global-dynamic".

     -fvisibility=default|internal|hidden|protected
         Set the default ELF image symbol visibility to the
         specified option---all symbols are marked with this
         unless overridden within the code.  Using this feature
         can very substantially improve linking and load times of
         shared object libraries, produce more optimized code,
         provide near-perfect API export and prevent symbol
         clashes.  It is strongly recommended that you use this
         in any shared objects you distribute.

         Despite the nomenclature, "default" always means public;
         i.e., available to be linked against from outside the
         shared object.  "protected" and "internal" are pretty
         useless in real-world usage so the only other commonly
         used option is "hidden".  The default if -fvisibility
         isn't specified is "default", i.e., make every symbol
         public---this causes the same behavior as previous
         versions of GCC.

         A good explanation of the benefits offered by ensuring
         ELF symbols have the correct visibility is given by "How
         To Write Shared Libraries" by Ulrich Drepper (which can
         be found at
         <http://people.redhat.com/~drepper/>)---however a
         superior solution made possible by this option to
         marking things hidden when the default is public is to
         make the default hidden and mark things public.  This is
         the norm with DLLs on Windows and with
         -fvisibility=hidden and "__attribute__
         ((visibility("default")))" instead of
         "__declspec(dllexport)" you get almost identical
         semantics with identical syntax.  This is a great boon
         to those working with cross-platform projects.

         For those adding visibility support to existing code,
         you may find #pragma GCC visibility of use.  This works
         by you enclosing the declarations you wish to set
         visibility for with (for example) #pragma GCC visibility
         push(hidden) and #pragma GCC visibility pop.  Bear in
         mind that symbol visibility should be viewed as part of
         the API interface contract and thus all new code should
         always specify visibility when it is not the default;
         i.e., declarations only for use within the local DSO
         should always be marked explicitly as hidden as so to
         avoid PLT indirection overheads---making this abundantly
         clear also aids readability and self-documentation of
         the code.  Note that due to ISO C++ specification
         requirements, "operator new" and "operator delete" must
         always be of default visibility.

         Be aware that headers from outside your project, in
         particular system headers and headers from any other
         library you use, may not be expecting to be compiled
         with visibility other than the default.  You may need to
         explicitly say #pragma GCC visibility push(default)
         before including any such headers.

         extern declarations are not affected by -fvisibility, so
         a lot of code can be recompiled with -fvisibility=hidden
         with no modifications.  However, this means that calls
         to "extern" functions with no explicit visibility use
         the PLT, so it is more effective to use "__attribute
         ((visibility))" and/or "#pragma GCC visibility" to tell
         the compiler which "extern" declarations should be
         treated as hidden.

         Note that -fvisibility does affect C++ vague linkage
         entities. This means that, for instance, an exception
         class that is be thrown between DSOs must be explicitly
         marked with default visibility so that the type_info
         nodes are unified between the DSOs.

         An overview of these techniques, their benefits and how
         to use them is at <http://gcc.gnu.org/wiki/Visibility>.

     -fstrict-volatile-bitfields
         This option should be used if accesses to volatile bit-
         fields (or other structure fields, although the compiler
         usually honors those types anyway) should use a single
         access of the width of the field's type, aligned to a
         natural alignment if possible.  For example, targets
         with memory-mapped peripheral registers might require
         all such accesses to be 16 bits wide; with this flag you
         can declare all peripheral bit-fields as "unsigned
         short" (assuming short is 16 bits on these targets) to
         force GCC to use 16-bit accesses instead of, perhaps, a
         more efficient 32-bit access.

         If this option is disabled, the compiler uses the most
         efficient instruction.  In the previous example, that
         might be a 32-bit load instruction, even though that
         accesses bytes that do not contain any portion of the
         bit-field, or memory-mapped registers unrelated to the
         one being updated.

         If the target requires strict alignment, and honoring
         the field type would require violating this alignment, a
         warning is issued.  If the field has "packed" attribute,
         the access is done without honoring the field type.  If
         the field doesn't have "packed" attribute, the access is
         done honoring the field type.  In both cases, GCC
         assumes that the user knows something about the target
         hardware that it is unaware of.

         The default value of this option is determined by the
         application binary interface for the target processor.

     -fsync-libcalls
         This option controls whether any out-of-line instance of
         the "__sync" family of functions may be used to
         implement the C++11 "__atomic" family of functions.

         The default value of this option is enabled, thus the
         only useful form of the option is -fno-sync-libcalls.
         This option is used in the implementation of the
         libatomic runtime library.

Environment
     This section describes several environment variables that
     affect how GCC operates.  Some of them work by specifying
     directories or prefixes to use when searching for various
     kinds of files.  Some are used to specify other aspects of
     the compilation environment.

     Note that you can also specify places to search using
     options such as -B, -I and -L.  These take precedence over
     places specified using environment variables, which in turn
     take precedence over those specified by the configuration of
     GCC.

     LANG
     LC_CTYPE
     LC_MESSAGES
     LC_ALL
         These environment variables control the way that GCC
         uses localization information which allows GCC to work
         with different national conventions.  GCC inspects the
         locale categories LC_CTYPE and LC_MESSAGES if it has
         been configured to do so.  These locale categories can
         be set to any value supported by your installation.  A
         typical value is en_GB.UTF-8 for English in the United
         Kingdom encoded in UTF-8.

         The LC_CTYPE environment variable specifies character
         classification.  GCC uses it to determine the character
         boundaries in a string; this is needed for some
         multibyte encodings that contain quote and escape
         characters that are otherwise interpreted as a string
         end or escape.

         The LC_MESSAGES environment variable specifies the
         language to use in diagnostic messages.

         If the LC_ALL environment variable is set, it overrides
         the value of LC_CTYPE and LC_MESSAGES; otherwise,
         LC_CTYPE and LC_MESSAGES default to the value of the
         LANG environment variable.  If none of these variables
         are set, GCC defaults to traditional C English behavior.

     TMPDIR
         If TMPDIR is set, it specifies the directory to use for
         temporary files.  GCC uses temporary files to hold the
         output of one stage of compilation which is to be used
         as input to the next stage: for example, the output of
         the preprocessor, which is the input to the compiler
         proper.

     GCC_COMPARE_DEBUG
         Setting GCC_COMPARE_DEBUG is nearly equivalent to
         passing -fcompare-debug to the compiler driver.  See the
         documentation of this option for more details.

     GCC_EXEC_PREFIX
         If GCC_EXEC_PREFIX is set, it specifies a prefix to use
         in the names of the subprograms executed by the
         compiler.  No slash is added when this prefix is
         combined with the name of a subprogram, but you can
         specify a prefix that ends with a slash if you wish.

         If GCC_EXEC_PREFIX is not set, GCC attempts to figure
         out an appropriate prefix to use based on the pathname
         it is invoked with.

         If GCC cannot find the subprogram using the specified
         prefix, it tries looking in the usual places for the
         subprogram.

         The default value of GCC_EXEC_PREFIX is prefix/lib/gcc/
         where prefix is the prefix to the installed compiler. In
         many cases prefix is the value of "prefix" when you ran
         the configure script.

         Other prefixes specified with -B take precedence over
         this prefix.

         This prefix is also used for finding files such as
         crt0.o that are used for linking.

         In addition, the prefix is used in an unusual way in
         finding the directories to search for header files.  For
         each of the standard directories whose name normally
         begins with /usr/local/lib/gcc (more precisely, with the
         value of GCC_INCLUDE_DIR), GCC tries replacing that
         beginning with the specified prefix to produce an
         alternate directory name.  Thus, with -Bfoo/, GCC
         searches foo/bar just before it searches the standard
         directory /usr/local/lib/bar.  If a standard directory
         begins with the configured prefix then the value of
         prefix is replaced by GCC_EXEC_PREFIX when looking for
         header files.

     COMPILER_PATH
         The value of COMPILER_PATH is a colon-separated list of
         directories, much like PATH.  GCC tries the directories
         thus specified when searching for subprograms, if it
         can't find the subprograms using GCC_EXEC_PREFIX.

     LIBRARY_PATH
         The value of LIBRARY_PATH is a colon-separated list of
         directories, much like PATH.  When configured as a
         native compiler, GCC tries the directories thus
         specified when searching for special linker files, if it
         can't find them using GCC_EXEC_PREFIX.  Linking using
         GCC also uses these directories when searching for
         ordinary libraries for the -l option (but directories
         specified with -L come first).

     LANG
         This variable is used to pass locale information to the
         compiler.  One way in which this information is used is
         to determine the character set to be used when character
         literals, string literals and comments are parsed in C
         and C++.  When the compiler is configured to allow
         multibyte characters, the following values for LANG are
         recognized:

         C-JIS
             Recognize JIS characters.

         C-SJIS
             Recognize SJIS characters.

         C-EUCJP
             Recognize EUCJP characters.

         If LANG is not defined, or if it has some other value,
         then the compiler uses "mblen" and "mbtowc" as defined
         by the default locale to recognize and translate
         multibyte characters.

     Some additional environment variables affect the behavior of
     the preprocessor.

     CPATH
     C_INCLUDE_PATH
     CPLUS_INCLUDE_PATH
     OBJC_INCLUDE_PATH
         Each variable's value is a list of directories separated
         by a special character, much like PATH, in which to look
         for header files.  The special character,
         "PATH_SEPARATOR", is target-dependent and determined at
         GCC build time.  For Microsoft Windows-based targets it
         is a semicolon, and for almost all other targets it is a
         colon.

         CPATH specifies a list of directories to be searched as
         if specified with -I, but after any paths given with -I
         options on the command line.  This environment variable
         is used regardless of which language is being
         preprocessed.

         The remaining environment variables apply only when
         preprocessing the particular language indicated.  Each
         specifies a list of directories to be searched as if
         specified with -isystem, but after any paths given with
         -isystem options on the command line.

         In all these variables, an empty element instructs the
         compiler to search its current working directory.  Empty
         elements can appear at the beginning or end of a path.
         For instance, if the value of CPATH is
         ":/special/include", that has the same effect as
         -I. -I/special/include.

     DEPENDENCIES_OUTPUT
         If this variable is set, its value specifies how to
         output dependencies for Make based on the non-system
         header files processed by the compiler.  System header
         files are ignored in the dependency output.

         The value of DEPENDENCIES_OUTPUT can be just a file
         name, in which case the Make rules are written to that
         file, guessing the target name from the source file
         name.  Or the value can have the form file target, in
         which case the rules are written to file file using
         target as the target name.

         In other words, this environment variable is equivalent
         to combining the options -MM and -MF, with an optional
         -MT switch too.

     SUNPRO_DEPENDENCIES
         This variable is the same as DEPENDENCIES_OUTPUT (see
         above), except that system header files are not ignored,
         so it implies -M rather than -MM.  However, the
         dependence on the main input file is omitted.

Bugs
     For instructions on reporting bugs, see
     <http://gcc.gnu.org/bugs.html>.

Footnotes
     1.  On some systems, gcc -shared needs to build
         supplementary stub code for constructors to work.  On
         multi-libbed systems, gcc -shared must select the
         correct support libraries to link against.  Failing to
         supply the correct flags may lead to subtle defects.
         Supplying them in cases where they are not necessary is
         innocuous.

Attributes
     See attributes(5) for descriptions of the following
     attributes:

     box; cbp-1 | cbp-1 l | l .  ATTRIBUTE TYPE ATTRIBUTE VALUE =
     Availability   developer/gcc-4/gcc-c-48 =
     Stability Uncommitted

See Also
     gpl(7), gfdl(7), fsf-funding(7), cpp(1), gcov(1), as(1),
     ld(1), gdb(1), adb(1), dbx(1), sdb(1) and the Info entries
     for gcc, cpp, as, ld, binutils and gdb.

Author
     See the Info entry for gcc, or
     <http://gcc.gnu.org/onlinedocs/gcc/Contributors.html>, for
     contributors to GCC.

Copyright
     Copyright (c) 1988-2013 Free Software Foundation, Inc.

     Permission is granted to copy, distribute and/or modify this
     document under the terms of the GNU Free Documentation
     License, Version 1.3 or any later version published by the
     Free Software Foundation; with the Invariant Sections being
     "GNU General Public License" and "Funding Free Software",
     the Front-Cover texts being (a) (see below), and with the
     Back-Cover Texts being (b) (see below).  A copy of the
     license is included in the gfdl(7) man page.

     (a) The FSF's Front-Cover Text is:

          A GNU Manual

     (b) The FSF's Back-Cover Text is:

          You have freedom to copy and modify this GNU Manual, like GNU
          software.  Copies published by the Free Software Foundation raise
          funds for GNU development.

Notes
     This software was built from source available at
     https://java.net/projects/solaris-userland.  The original
     community source was downloaded from
     http://ftp.gnu.org/gnu/gcc/gcc-4.8.2/gcc-4.8.2.tar.gz

     Further information about this software can be found on the
     open source community website at http://gcc.gnu.org/.
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