AS(1) GNU Development Tools AS(1)
NAME
AS - the portable GNU assembler.
SYNOPSIS
as [-a[cdghlns][=file]] [--alternate] [-D]
[--compress-debug-sections] [--nocompress-debug-sections]
[--debug-prefix-map old=new]
[--defsym sym=val] [-f] [-g] [--gstabs]
[--gstabs+] [--gdwarf-2] [--gdwarf-sections]
[--help] [-I dir] [-J]
[-K] [-L] [--listing-lhs-width=NUM]
[--listing-lhs-width2=NUM] [--listing-rhs-width=NUM]
[--listing-cont-lines=NUM] [--keep-locals]
[--no-pad-sections]
[-o objfile] [-R]
[--hash-size=NUM] [--reduce-memory-overheads]
[--statistics]
[-v] [-version] [--version]
[-W] [--warn] [--fatal-warnings] [-w] [-x]
[-Z] [@FILE]
[--sectname-subst] [--size-check=[error|warning]]
[--elf-stt-common=[no|yes]]
[--target-help] [target-options]
[--|files ...]
TARGET
Target AArch64 options:
[-EB|-EL]
[-mabi=ABI]
Target Alpha options:
[-mcpu]
[-mdebug | -no-mdebug]
[-replace | -noreplace]
[-relax] [-g] [-Gsize]
[-F] [-32addr]
Target ARC options:
[-mcpu=cpu]
[-mA6|-mARC600|-mARC601|-mA7|-mARC700|-mEM|-mHS]
[-mcode-density]
[-mrelax]
[-EB|-EL]
Target ARM options:
[-mcpu=processor[+extension...]]
[-march=architecture[+extension...]]
[-mfpu=floating-point-format]
[-mfloat-abi=abi]
[-meabi=ver]
[-mthumb]
[-EB|-EL]
[-mapcs-32|-mapcs-26|-mapcs-float|
-mapcs-reentrant]
[-mthumb-interwork] [-k]
Target Blackfin options:
[-mcpu=processor[-sirevision]]
[-mfdpic]
[-mno-fdpic]
[-mnopic]
Target CRIS options:
[--underscore | --no-underscore]
[--pic] [-N]
[--emulation=criself | --emulation=crisaout]
[--march=v0_v10 | --march=v10 | --march=v32 |
--march=common_v10_v32]
Target D10V options:
[-O]
Target D30V options:
[-O|-n|-N]
Target EPIPHANY options:
[-mepiphany|-mepiphany16]
Target H8/300 options:
[-h-tick-hex]
Target i386 options:
[--32|--x32|--64] [-n]
[-march=CPU[+EXTENSION...]] [-mtune=CPU]
Target i960 options:
[-ACA|-ACA_A|-ACB|-ACC|-AKA|-AKB|
-AKC|-AMC]
[-b] [-no-relax]
Target IA-64 options:
[-mconstant-gp|-mauto-pic]
[-milp32|-milp64|-mlp64|-mp64]
[-mle|mbe]
[-mtune=itanium1|-mtune=itanium2]
[-munwind-check=warning|-munwind-check=error]
[-mhint.b=ok|-mhint.b=warning|-mhint.b=error]
[-x|-xexplicit] [-xauto] [-xdebug]
Target IP2K options:
[-mip2022|-mip2022ext]
Target M32C options:
[-m32c|-m16c] [-relax] [-h-tick-hex]
Target M32R options:
[--m32rx|--[no-]warn-explicit-parallel-conflicts|
--W[n]p]
Target M680X0 options:
[-l] [-m68000|-m68010|-m68020|...]
Target M68HC11 options:
[-m68hc11|-m68hc12|-m68hcs12|-mm9s12x|-mm9s12xg]
[-mshort|-mlong]
[-mshort-double|-mlong-double]
[--force-long-branches] [--short-branches]
[--strict-direct-mode] [--print-insn-syntax]
[--print-opcodes] [--generate-example]
Target MCORE options:
[-jsri2bsr] [-sifilter] [-relax]
[-mcpu=[210|340]]
Target Meta options:
[-mcpu=cpu] [-mfpu=cpu] [-mdsp=cpu] Target MICROBLAZE options:
Target MIPS options:
[-nocpp] [-EL] [-EB] [-O[optimization level]]
[-g[debug level]] [-G num] [-KPIC] [-call_shared]
[-non_shared] [-xgot [-mvxworks-pic]
[-mabi=ABI] [-32] [-n32] [-64] [-mfp32] [-mgp32]
[-mfp64] [-mgp64] [-mfpxx]
[-modd-spreg] [-mno-odd-spreg]
[-march=CPU] [-mtune=CPU] [-mips1] [-mips2]
[-mips3] [-mips4] [-mips5] [-mips32] [-mips32r2]
[-mips32r3] [-mips32r5] [-mips32r6] [-mips64] [-mips64r2]
[-mips64r3] [-mips64r5] [-mips64r6]
[-construct-floats] [-no-construct-floats]
[-mnan=encoding]
[-trap] [-no-break] [-break] [-no-trap]
[-mips16] [-no-mips16]
[-mmicromips] [-mno-micromips]
[-msmartmips] [-mno-smartmips]
[-mips3d] [-no-mips3d]
[-mdmx] [-no-mdmx]
[-mdsp] [-mno-dsp]
[-mdspr2] [-mno-dspr2]
[-mdspr3] [-mno-dspr3]
[-mmsa] [-mno-msa]
[-mxpa] [-mno-xpa]
[-mmt] [-mno-mt]
[-mmcu] [-mno-mcu]
[-minsn32] [-mno-insn32]
[-mfix7000] [-mno-fix7000]
[-mfix-rm7000] [-mno-fix-rm7000]
[-mfix-vr4120] [-mno-fix-vr4120]
[-mfix-vr4130] [-mno-fix-vr4130]
[-mdebug] [-no-mdebug]
[-mpdr] [-mno-pdr]
Target MMIX options:
[--fixed-special-register-names] [--globalize-symbols]
[--gnu-syntax] [--relax] [--no-predefined-symbols]
[--no-expand] [--no-merge-gregs] [-x]
[--linker-allocated-gregs]
Target Nios II options:
[-relax-all] [-relax-section] [-no-relax]
[-EB] [-EL]
Target NDS32 options:
[-EL] [-EB] [-O] [-Os] [-mcpu=cpu]
[-misa=isa] [-mabi=abi] [-mall-ext]
[-m[no-]16-bit] [-m[no-]perf-ext] [-m[no-]perf2-ext]
[-m[no-]string-ext] [-m[no-]dsp-ext] [-m[no-]mac] [-m[no-]div]
[-m[no-]audio-isa-ext] [-m[no-]fpu-sp-ext] [-m[no-]fpu-dp-ext]
[-m[no-]fpu-fma] [-mfpu-freg=FREG] [-mreduced-regs]
[-mfull-regs] [-m[no-]dx-regs] [-mpic] [-mno-relax]
[-mb2bb]
Target PDP11 options:
[-mpic|-mno-pic] [-mall] [-mno-extensions]
[-mextension|-mno-extension]
[-mcpu] [-mmachine]
Target picoJava options:
[-mb|-me]
Target PowerPC options:
[-a32|-a64]
[-mpwrx|-mpwr2|-mpwr|-m601|-mppc|-mppc32|-m603|-m604|-m403|-m405|
-m440|-m464|-m476|-m7400|-m7410|-m7450|-m7455|-m750cl|-mppc64|
-m620|-me500|-e500x2|-me500mc|-me500mc64|-me5500|-me6500|-mppc64bridge|
-mbooke|-mpower4|-mpwr4|-mpower5|-mpwr5|-mpwr5x|-mpower6|-mpwr6|
-mpower7|-mpwr7|-mpower8|-mpwr8|-mpower9|-mpwr9-ma2|
-mcell|-mspe|-mtitan|-me300|-mcom]
[-many] [-maltivec|-mvsx|-mhtm|-mvle]
[-mregnames|-mno-regnames]
[-mrelocatable|-mrelocatable-lib|-K PIC] [-memb]
[-mlittle|-mlittle-endian|-le|-mbig|-mbig-endian|-be]
[-msolaris|-mno-solaris]
[-nops=count]
Target RL78 options:
[-mg10]
[-m32bit-doubles|-m64bit-doubles]
Target RX options:
[-mlittle-endian|-mbig-endian]
[-m32bit-doubles|-m64bit-doubles]
[-muse-conventional-section-names]
[-msmall-data-limit]
[-mpid]
[-mrelax]
[-mint-register=number]
[-mgcc-abi|-mrx-abi]
Target s390 options:
[-m31|-m64] [-mesa|-mzarch] [-march=CPU]
[-mregnames|-mno-regnames]
[-mwarn-areg-zero]
Target SCORE options:
[-EB][-EL][-FIXDD][-NWARN]
[-SCORE5][-SCORE5U][-SCORE7][-SCORE3]
[-march=score7][-march=score3]
[-USE_R1][-KPIC][-O0][-G num][-V]
Target SPARC options:
[-Av6|-Av7|-Av8|-Asparclet|-Asparclite
-Av8plus|-Av8plusa|-Av9|-Av9a]
[-xarch=v8plus|-xarch=v8plusa] [-bump]
[-32|-64]
Target TIC54X options:
[-mcpu=54[123589]|-mcpu=54[56]lp] [-mfar-mode|-mf]
[-merrors-to-file <filename>|-me <filename>]
Target TIC6X options:
[-march=arch] [-mbig-endian|-mlittle-endian]
[-mdsbt|-mno-dsbt] [-mpid=no|-mpid=near|-mpid=far]
[-mpic|-mno-pic]
Target TILE-Gx options:
[-m32|-m64][-EB][-EL]
Target Visium options:
[-mtune=arch]
Target Xtensa options:
[--[no-]text-section-literals] [--[no-]auto-litpools]
[--[no-]absolute-literals]
[--[no-]target-align] [--[no-]longcalls]
[--[no-]transform]
[--rename-section oldname=newname]
[--[no-]trampolines]
Target Z80 options:
[-z80] [-r800]
[ -ignore-undocumented-instructions] [-Wnud]
[ -ignore-unportable-instructions] [-Wnup]
[ -warn-undocumented-instructions] [-Wud]
[ -warn-unportable-instructions] [-Wup]
[ -forbid-undocumented-instructions] [-Fud]
[ -forbid-unportable-instructions] [-Fup]
DESCRIPTION
GNU as is really a family of assemblers. If you use (or have used) the
GNU assembler on one architecture, you should find a fairly similar
environment when you use it on another architecture. Each version has
much in common with the others, including object file formats, most
assembler directives (often called pseudo-ops) and assembler syntax.
as is primarily intended to assemble the output of the GNU C compiler
"gcc" for use by the linker "ld". Nevertheless, we've tried to make as
assemble correctly everything that other assemblers for the same
machine would assemble. Any exceptions are documented explicitly.
This doesn't mean as always uses the same syntax as another assembler
for the same architecture; for example, we know of several incompatible
versions of 680x0 assembly language syntax.
Each time you run as it assembles exactly one source program. The
source program is made up of one or more files. (The standard input is
also a file.)
You give as a command line that has zero or more input file names. The
input files are read (from left file name to right). A command line
argument (in any position) that has no special meaning is taken to be
an input file name.
If you give as no file names it attempts to read one input file from
the as standard input, which is normally your terminal. You may have
to type ctl-D to tell as there is no more program to assemble.
Use -- if you need to explicitly name the standard input file in your
command line.
If the source is empty, as produces a small, empty object file.
as may write warnings and error messages to the standard error file
(usually your terminal). This should not happen when a compiler runs
as automatically. Warnings report an assumption made so that as could
keep assembling a flawed program; errors report a grave problem that
stops the assembly.
If you are invoking as via the GNU C compiler, you can use the -Wa
option to pass arguments through to the assembler. The assembler
arguments must be separated from each other (and the -Wa) by commas.
For example:
gcc -c -g -O -Wa,-alh,-L file.c
This passes two options to the assembler: -alh (emit a listing to
standard output with high-level and assembly source) and -L (retain
local symbols in the symbol table).
Usually you do not need to use this -Wa mechanism, since many compiler
command-line options are automatically passed to the assembler by the
compiler. (You can call the GNU compiler driver with the -v option to
see precisely what options it passes to each compilation pass,
including the assembler.)
OPTIONS
@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.
-a[cdghlmns]
Turn on listings, in any of a variety of ways:
-ac omit false conditionals
-ad omit debugging directives
-ag include general information, like as version and options passed
-ah include high-level source
-al include assembly
-am include macro expansions
-an omit forms processing
-as include symbols
=file
set the name of the listing file
You may combine these options; for example, use -aln for assembly
listing without forms processing. The =file option, if used, must
be the last one. By itself, -a defaults to -ahls.
--alternate
Begin in alternate macro mode.
--compress-debug-sections
Compress DWARF debug sections using zlib with SHF_COMPRESSED from
the ELF ABI. The resulting object file may not be compatible with
older linkers and object file utilities. Note if compression would
make a given section larger then it is not compressed.
--compress-debug-sections=none
--compress-debug-sections=zlib
--compress-debug-sections=zlib-gnu
--compress-debug-sections=zlib-gabi
These options control how DWARF debug sections are compressed.
--compress-debug-sections=none is equivalent to
--nocompress-debug-sections. --compress-debug-sections=zlib and
--compress-debug-sections=zlib-gabi are equivalent to
--compress-debug-sections. --compress-debug-sections=zlib-gnu
compresses DWARF debug sections using zlib. The debug sections are
renamed to begin with .zdebug. Note if compression would make a
given section larger then it is not compressed nor renamed.
--nocompress-debug-sections
Do not compress DWARF debug sections. This is usually the default
for all targets except the x86/x86_64, but a configure time option
can be used to override this.
-D Ignored. This option is accepted for script compatibility with
calls to other assemblers.
--debug-prefix-map old=new
When assembling files in directory old, record debugging
information describing them as in new instead.
--defsym sym=value
Define the symbol sym to be value before assembling the input file.
value must be an integer constant. As in C, a leading 0x indicates
a hexadecimal value, and a leading 0 indicates an octal value. The
value of the symbol can be overridden inside a source file via the
use of a ".set" pseudo-op.
-f "fast"---skip whitespace and comment preprocessing (assume source
is compiler output).
-g
--gen-debug
Generate debugging information for each assembler source line using
whichever debug format is preferred by the target. This currently
means either STABS, ECOFF or DWARF2.
--gstabs
Generate stabs debugging information for each assembler line. This
may help debugging assembler code, if the debugger can handle it.
--gstabs+
Generate stabs debugging information for each assembler line, with
GNU extensions that probably only gdb can handle, and that could
make other debuggers crash or refuse to read your program. This
may help debugging assembler code. Currently the only GNU
extension is the location of the current working directory at
assembling time.
--gdwarf-2
Generate DWARF2 debugging information for each assembler line.
This may help debugging assembler code, if the debugger can handle
it. Note---this option is only supported by some targets, not all
of them.
--gdwarf-sections
Instead of creating a .debug_line section, create a series of
.debug_line.foo sections where foo is the name of the corresponding
code section. For example a code section called .text.func will
have its dwarf line number information placed into a section called
.debug_line.text.func. If the code section is just called .text
then debug line section will still be called just .debug_line
without any suffix.
--size-check=error
--size-check=warning
Issue an error or warning for invalid ELF .size directive.
--elf-stt-common=no
--elf-stt-common=yes
These options control whether the ELF assembler should generate
common symbols with the "STT_COMMON" type. The default can be
controlled by a configure option --enable-elf-stt-common.
--help
Print a summary of the command line options and exit.
--target-help
Print a summary of all target specific options and exit.
-I dir
Add directory dir to the search list for ".include" directives.
-J Don't warn about signed overflow.
-K Issue warnings when difference tables altered for long
displacements.
-L
--keep-locals
Keep (in the symbol table) local symbols. These symbols start with
system-specific local label prefixes, typically .L for ELF systems
or L for traditional a.out systems.
--listing-lhs-width=number
Set the maximum width, in words, of the output data column for an
assembler listing to number.
--listing-lhs-width2=number
Set the maximum width, in words, of the output data column for
continuation lines in an assembler listing to number.
--listing-rhs-width=number
Set the maximum width of an input source line, as displayed in a
listing, to number bytes.
--listing-cont-lines=number
Set the maximum number of lines printed in a listing for a single
line of input to number + 1.
--no-pad-sections
Stop the assembler for padding the ends of output sections to the
alignment of that section. The default is to pad the sections, but
this can waste space which might be needed on targets which have
tight memory constraints.
-o objfile
Name the object-file output from as objfile.
-R Fold the data section into the text section.
--hash-size=number
Set the default size of GAS's hash tables to a prime number close
to number. Increasing this value can reduce the length of time it
takes the assembler to perform its tasks, at the expense of
increasing the assembler's memory requirements. Similarly reducing
this value can reduce the memory requirements at the expense of
speed.
--reduce-memory-overheads
This option reduces GAS's memory requirements, at the expense of
making the assembly processes slower. Currently this switch is a
synonym for --hash-size=4051, but in the future it may have other
effects as well.
--sectname-subst
Honor substitution sequences in section names.
--statistics
Print the maximum space (in bytes) and total time (in seconds) used
by assembly.
--strip-local-absolute
Remove local absolute symbols from the outgoing symbol table.
-v
-version
Print the as version.
--version
Print the as version and exit.
-W
--no-warn
Suppress warning messages.
--fatal-warnings
Treat warnings as errors.
--warn
Don't suppress warning messages or treat them as errors.
-w Ignored.
-x Ignored.
-Z Generate an object file even after errors.
-- | files ...
Standard input, or source files to assemble.
The following options are available when as is configured for the
64-bit mode of the ARM Architecture (AArch64).
-EB This option specifies that the output generated by the assembler
should be marked as being encoded for a big-endian processor.
-EL This option specifies that the output generated by the assembler
should be marked as being encoded for a little-endian processor.
-mabi=abi
Specify which ABI the source code uses. The recognized arguments
are: "ilp32" and "lp64", which decides the generated object file in
ELF32 and ELF64 format respectively. The default is "lp64".
-mcpu=processor[+extension...]
This option specifies the target processor. The assembler will
issue an error message if an attempt is made to assemble an
instruction which will not execute on the target processor. The
following processor names are recognized: "cortex-a35",
"cortex-a53", "cortex-a57", "cortex-a72", "cortex-a73",
"exynos-m1", "qdf24xx", "thunderx", "vulcan", "xgene1" and
"xgene2". The special name "all" may be used to allow the
assembler to accept instructions valid for any supported processor,
including all optional extensions.
In addition to the basic instruction set, the assembler can be told
to accept, or restrict, various extension mnemonics that extend the
processor.
If some implementations of a particular processor can have an
extension, then then those extensions are automatically enabled.
Consequently, you will not normally have to specify any additional
extensions.
-march=architecture[+extension...]
This option specifies the target architecture. The assembler will
issue an error message if an attempt is made to assemble an
instruction which will not execute on the target architecture. The
following architecture names are recognized: "armv8-a", "armv8.1-a"
and "armv8.2-a".
If both -mcpu and -march are specified, the assembler will use the
setting for -mcpu. If neither are specified, the assembler will
default to -mcpu=all.
The architecture option can be extended with the same instruction
set extension options as the -mcpu option. Unlike -mcpu,
extensions are not always enabled by default,
-mverbose-error
This option enables verbose error messages for AArch64 gas. This
option is enabled by default.
-mno-verbose-error
This option disables verbose error messages in AArch64 gas.
The following options are available when as is configured for an Alpha
processor.
-mcpu
This option specifies the target processor. If an attempt is made
to assemble an instruction which will not execute on the target
processor, the assembler may either expand the instruction as a
macro or issue an error message. This option is equivalent to the
".arch" directive.
The following processor names are recognized: 21064, "21064a",
21066, 21068, 21164, "21164a", "21164pc", 21264, "21264a",
"21264b", "ev4", "ev5", "lca45", "ev5", "ev56", "pca56", "ev6",
"ev67", "ev68". The special name "all" may be used to allow the
assembler to accept instructions valid for any Alpha processor.
In order to support existing practice in OSF/1 with respect to
".arch", and existing practice within MILO (the Linux ARC
bootloader), the numbered processor names (e.g. 21064) enable the
processor-specific PALcode instructions, while the "electro-vlasic"
names (e.g. "ev4") do not.
-mdebug
-no-mdebug
Enables or disables the generation of ".mdebug" encapsulation for
stabs directives and procedure descriptors. The default is to
automatically enable ".mdebug" when the first stabs directive is
seen.
-relax
This option forces all relocations to be put into the object file,
instead of saving space and resolving some relocations at assembly
time. Note that this option does not propagate all symbol
arithmetic into the object file, because not all symbol arithmetic
can be represented. However, the option can still be useful in
specific applications.
-replace
-noreplace
Enables or disables the optimization of procedure calls, both at
assemblage and at link time. These options are only available for
VMS targets and "-replace" is the default. See section 1.4.1 of
the OpenVMS Linker Utility Manual.
-g This option is used when the compiler generates debug information.
When gcc is using mips-tfile to generate debug information for
ECOFF, local labels must be passed through to the object file.
Otherwise this option has no effect.
-Gsize
A local common symbol larger than size is placed in ".bss", while
smaller symbols are placed in ".sbss".
-F
-32addr
These options are ignored for backward compatibility.
The following options are available when as is configured for an ARC
processor.
-mcpu=cpu
This option selects the core processor variant.
-EB | -EL
Select either big-endian (-EB) or little-endian (-EL) output.
-mcode-density
Enable Code Density extenssion instructions.
The following options are available when as is configured for the ARM
processor family.
-mcpu=processor[+extension...]
Specify which ARM processor variant is the target.
-march=architecture[+extension...]
Specify which ARM architecture variant is used by the target.
-mfpu=floating-point-format
Select which Floating Point architecture is the target.
-mfloat-abi=abi
Select which floating point ABI is in use.
-mthumb
Enable Thumb only instruction decoding.
-mapcs-32 | -mapcs-26 | -mapcs-float | -mapcs-reentrant
Select which procedure calling convention is in use.
-EB | -EL
Select either big-endian (-EB) or little-endian (-EL) output.
-mthumb-interwork
Specify that the code has been generated with interworking between
Thumb and ARM code in mind.
-mccs
Turns on CodeComposer Studio assembly syntax compatibility mode.
-k Specify that PIC code has been generated.
The following options are available when as is configured for the
Blackfin processor family.
-mcpu=processor[-sirevision]
This option specifies the target processor. The optional
sirevision is not used in assembler. It's here such that GCC can
easily pass down its "-mcpu=" option. The assembler will issue an
error message if an attempt is made to assemble an instruction
which will not execute on the target processor. The following
processor names are recognized: "bf504", "bf506", "bf512", "bf514",
"bf516", "bf518", "bf522", "bf523", "bf524", "bf525", "bf526",
"bf527", "bf531", "bf532", "bf533", "bf534", "bf535" (not
implemented yet), "bf536", "bf537", "bf538", "bf539", "bf542",
"bf542m", "bf544", "bf544m", "bf547", "bf547m", "bf548", "bf548m",
"bf549", "bf549m", "bf561", and "bf592".
-mfdpic
Assemble for the FDPIC ABI.
-mno-fdpic
-mnopic
Disable -mfdpic.
See the info pages for documentation of the CRIS-specific options.
The following options are available when as is configured for a D10V
processor.
-O Optimize output by parallelizing instructions.
The following options are available when as is configured for a D30V
processor.
-O Optimize output by parallelizing instructions.
-n Warn when nops are generated.
-N Warn when a nop after a 32-bit multiply instruction is generated.
The following options are available when as is configured for an
Epiphany processor.
-mepiphany
Specifies that the both 32 and 16 bit instructions are allowed.
This is the default behavior.
-mepiphany16
Restricts the permitted instructions to just the 16 bit set.
The following options are available when as is configured for an H8/300
processor. @chapter H8/300 Dependent Features
Options
The Renesas H8/300 version of "as" has one machine-dependent option:
-h-tick-hex
Support H'00 style hex constants in addition to 0x00 style.
-mach=name
Sets the H8300 machine variant. The following machine names are
recognised: "h8300h", "h8300hn", "h8300s", "h8300sn", "h8300sx" and
"h8300sxn".
The following options are available when as is configured for an i386
processor.
--32 | --x32 | --64
Select the word size, either 32 bits or 64 bits. --32 implies
Intel i386 architecture, while --x32 and --64 imply AMD x86-64
architecture with 32-bit or 64-bit word-size respectively.
These options are only available with the ELF object file format,
and require that the necessary BFD support has been included (on a
32-bit platform you have to add --enable-64-bit-bfd to configure
enable 64-bit usage and use x86-64 as target platform).
-n By default, x86 GAS replaces multiple nop instructions used for
alignment within code sections with multi-byte nop instructions
such as leal 0(%esi,1),%esi. This switch disables the
optimization.
--divide
On SVR4-derived platforms, the character / is treated as a comment
character, which means that it cannot be used in expressions. The
--divide option turns / into a normal character. This does not
disable / at the beginning of a line starting a comment, or affect
using # for starting a comment.
-march=CPU[+EXTENSION...]
This option specifies the target processor. The assembler will
issue an error message if an attempt is made to assemble an
instruction which will not execute on the target processor. The
following processor names are recognized: "i8086", "i186", "i286",
"i386", "i486", "i586", "i686", "pentium", "pentiumpro",
"pentiumii", "pentiumiii", "pentium4", "prescott", "nocona",
"core", "core2", "corei7", "l1om", "k1om", "iamcu", "k6", "k6_2",
"athlon", "opteron", "k8", "amdfam10", "bdver1", "bdver2",
"bdver3", "bdver4", "znver1", "btver1", "btver2", "generic32" and
"generic64".
In addition to the basic instruction set, the assembler can be told
to accept various extension mnemonics. For example,
"-march=i686+sse4+vmx" extends i686 with sse4 and vmx. The
following extensions are currently supported: 8087, 287, 387, 687,
"no87", "no287", "no387", "no687", "mmx", "nommx", "sse", "sse2",
"sse3", "ssse3", "sse4.1", "sse4.2", "sse4", "nosse", "nosse2",
"nosse3", "nossse3", "nosse4.1", "nosse4.2", "nosse4", "avx",
"avx2", "noavx", "noavx2", "adx", "rdseed", "prfchw", "smap",
"mpx", "sha", "rdpid", "prefetchwt1", "clflushopt", "se1", "clwb",
"pcommit", "avx512f", "avx512cd", "avx512er", "avx512pf",
"avx512vl", "avx512bw", "avx512dq", "avx512ifma", "avx512vbmi",
"noavx512f", "noavx512cd", "noavx512er", "noavx512pf",
"noavx512vl", "noavx512bw", "noavx512dq", "noavx512ifma",
"noavx512vbmi", "vmx", "vmfunc", "smx", "xsave", "xsaveopt",
"xsavec", "xsaves", "aes", "pclmul", "fsgsbase", "rdrnd", "f16c",
"bmi2", "fma", "movbe", "ept", "lzcnt", "hle", "rtm", "invpcid",
"clflush", "mwaitx", "clzero", "lwp", "fma4", "xop", "cx16",
"syscall", "rdtscp", "3dnow", "3dnowa", "sse4a", "sse5", "svme",
"abm" and "padlock". Note that rather than extending a basic
instruction set, the extension mnemonics starting with "no" revoke
the respective functionality.
When the ".arch" directive is used with -march, the ".arch"
directive will take precedent.
-mtune=CPU
This option specifies a processor to optimize for. When used in
conjunction with the -march option, only instructions of the
processor specified by the -march option will be generated.
Valid CPU values are identical to the processor list of -march=CPU.
-msse2avx
This option specifies that the assembler should encode SSE
instructions with VEX prefix.
-msse-check=none
-msse-check=warning
-msse-check=error
These options control if the assembler should check SSE
instructions. -msse-check=none will make the assembler not to
check SSE instructions, which is the default. -msse-check=warning
will make the assembler issue a warning for any SSE instruction.
-msse-check=error will make the assembler issue an error for any
SSE instruction.
-mavxscalar=128
-mavxscalar=256
These options control how the assembler should encode scalar AVX
instructions. -mavxscalar=128 will encode scalar AVX instructions
with 128bit vector length, which is the default. -mavxscalar=256
will encode scalar AVX instructions with 256bit vector length.
-mevexlig=128
-mevexlig=256
-mevexlig=512
These options control how the assembler should encode length-
ignored (LIG) EVEX instructions. -mevexlig=128 will encode LIG
EVEX instructions with 128bit vector length, which is the default.
-mevexlig=256 and -mevexlig=512 will encode LIG EVEX instructions
with 256bit and 512bit vector length, respectively.
-mevexwig=0
-mevexwig=1
These options control how the assembler should encode w-ignored
(WIG) EVEX instructions. -mevexwig=0 will encode WIG EVEX
instructions with evex.w = 0, which is the default. -mevexwig=1
will encode WIG EVEX instructions with evex.w = 1.
-mmnemonic=att
-mmnemonic=intel
This option specifies instruction mnemonic for matching
instructions. The ".att_mnemonic" and ".intel_mnemonic" directives
will take precedent.
-msyntax=att
-msyntax=intel
This option specifies instruction syntax when processing
instructions. The ".att_syntax" and ".intel_syntax" directives
will take precedent.
-mnaked-reg
This opetion specifies that registers don't require a % prefix.
The ".att_syntax" and ".intel_syntax" directives will take
precedent.
-madd-bnd-prefix
This option forces the assembler to add BND prefix to all branches,
even if such prefix was not explicitly specified in the source
code.
-mno-shared
On ELF target, the assembler normally optimizes out non-PLT
relocations against defined non-weak global branch targets with
default visibility. The -mshared option tells the assembler to
generate code which may go into a shared library where all non-weak
global branch targets with default visibility can be preempted.
The resulting code is slightly bigger. This option only affects
the handling of branch instructions.
-mbig-obj
On x86-64 PE/COFF target this option forces the use of big object
file format, which allows more than 32768 sections.
-momit-lock-prefix=no
-momit-lock-prefix=yes
These options control how the assembler should encode lock prefix.
This option is intended as a workaround for processors, that fail
on lock prefix. This option can only be safely used with single-
core, single-thread computers -momit-lock-prefix=yes will omit all
lock prefixes. -momit-lock-prefix=no will encode lock prefix as
usual, which is the default.
-mfence-as-lock-add=no
-mfence-as-lock-add=yes
These options control how the assembler should encode lfence,
mfence and sfence. -mfence-as-lock-add=yes will encode lfence,
mfence and sfence as lock addl $0x0, (%rsp) in 64-bit mode and lock
addl $0x0, (%esp) in 32-bit mode. -mfence-as-lock-add=no will
encode lfence, mfence and sfence as usual, which is the default.
-mrelax-relocations=no
-mrelax-relocations=yes
These options control whether the assembler should generate relax
relocations, R_386_GOT32X, in 32-bit mode, or R_X86_64_GOTPCRELX
and R_X86_64_REX_GOTPCRELX, in 64-bit mode.
-mrelax-relocations=yes will generate relax relocations.
-mrelax-relocations=no will not generate relax relocations. The
default can be controlled by a configure option
--enable-x86-relax-relocations.
-malign-branch-boundary=NUM
This option controls how the assembler should align branches with
segment prefixes or NOP. NUM must be a power of 2. It should be 0
or no less than 32. Branches will be aligned within NUM byte
boundary. -malign-branch-boundary=0, which is the default, doesn't
align branches.
-malign-branch=TYPE[+TYPE...]
This option specifies types of branches to align. TYPE is
combination of jcc, which aligns conditional jumps, fused, which
aligns fused conditional jumps, jmp, which aligns unconditional
jumps, call which aligns calls, ret, which aligns rets, indirect,
which aligns indirect jumps and calls. The default is
-malign-branch=jcc+fused+jmp.
-malign-branch-prefix-size=NUM
This option specifies the maximum number of prefixes on an
instruction to align branches. NUM should be between 0 and 5. The
default NUM is 5.
-mbranches-within-32B-boundaries
This option aligns conditional jumps, fused conditional jumps and
unconditional jumps within 32 byte boundary with up to 5 segment
prefixes on an instruction. It is equivalent to
-malign-branch-boundary=32 -malign-branch=jcc+fused+jmp
-malign-branch-prefix-size=5. The default doesn't align branches.
-mevexrcig=rne
-mevexrcig=rd
-mevexrcig=ru
-mevexrcig=rz
These options control how the assembler should encode SAE-only EVEX
instructions. -mevexrcig=rne will encode RC bits of EVEX
instruction with 00, which is the default. -mevexrcig=rd,
-mevexrcig=ru and -mevexrcig=rz will encode SAE-only EVEX
instructions with 01, 10 and 11 RC bits, respectively.
-mamd64
-mintel64
This option specifies that the assembler should accept only AMD64
or Intel64 ISA in 64-bit mode. The default is to accept both.
The following options are available when as is configured for the Intel
80960 processor.
-ACA | -ACA_A | -ACB | -ACC | -AKA | -AKB | -AKC | -AMC
Specify which variant of the 960 architecture is the target.
-b Add code to collect statistics about branches taken.
-no-relax
Do not alter compare-and-branch instructions for long
displacements; error if necessary.
The following options are available when as is configured for the
Ubicom IP2K series.
-mip2022ext
Specifies that the extended IP2022 instructions are allowed.
-mip2022
Restores the default behaviour, which restricts the permitted
instructions to just the basic IP2022 ones.
The following options are available when as is configured for the
Renesas M32C and M16C processors.
-m32c
Assemble M32C instructions.
-m16c
Assemble M16C instructions (the default).
-relax
Enable support for link-time relaxations.
-h-tick-hex
Support H'00 style hex constants in addition to 0x00 style.
The following options are available when as is configured for the
Renesas M32R (formerly Mitsubishi M32R) series.
--m32rx
Specify which processor in the M32R family is the target. The
default is normally the M32R, but this option changes it to the
M32RX.
--warn-explicit-parallel-conflicts or --Wp
Produce warning messages when questionable parallel constructs are
encountered.
--no-warn-explicit-parallel-conflicts or --Wnp
Do not produce warning messages when questionable parallel
constructs are encountered.
The following options are available when as is configured for the
Motorola 68000 series.
-l Shorten references to undefined symbols, to one word instead of
two.
-m68000 | -m68008 | -m68010 | -m68020 | -m68030
| -m68040 | -m68060 | -m68302 | -m68331 | -m68332
| -m68333 | -m68340 | -mcpu32 | -m5200
Specify what processor in the 68000 family is the target. The
default is normally the 68020, but this can be changed at
configuration time.
-m68881 | -m68882 | -mno-68881 | -mno-68882
The target machine does (or does not) have a floating-point
coprocessor. The default is to assume a coprocessor for 68020,
68030, and cpu32. Although the basic 68000 is not compatible with
the 68881, a combination of the two can be specified, since it's
possible to do emulation of the coprocessor instructions with the
main processor.
-m68851 | -mno-68851
The target machine does (or does not) have a memory-management unit
coprocessor. The default is to assume an MMU for 68020 and up.
The following options are available when as is configured for an Altera
Nios II processor.
-relax-section
Replace identified out-of-range branches with PC-relative "jmp"
sequences when possible. The generated code sequences are suitable
for use in position-independent code, but there is a practical
limit on the extended branch range because of the length of the
sequences. This option is the default.
-relax-all
Replace branch instructions not determinable to be in range and all
call instructions with "jmp" and "callr" sequences (respectively).
This option generates absolute relocations against the target
symbols and is not appropriate for position-independent code.
-no-relax
Do not replace any branches or calls.
-EB Generate big-endian output.
-EL Generate little-endian output. This is the default.
-march=architecture
This option specifies the target architecture. The assembler
issues an error message if an attempt is made to assemble an
instruction which will not execute on the target architecture. The
following architecture names are recognized: "r1", "r2". The
default is "r1".
The following options are available when as is configured for a Meta
processor.
"-mcpu=metac11"
Generate code for Meta 1.1.
"-mcpu=metac12"
Generate code for Meta 1.2.
"-mcpu=metac21"
Generate code for Meta 2.1.
"-mfpu=metac21"
Allow code to use FPU hardware of Meta 2.1.
See the info pages for documentation of the MMIX-specific options.
The following options are available when as is configured for a NDS32
processor.
"-O1"
Optimize for performance.
"-Os"
Optimize for space.
"-EL"
Produce little endian data output.
"-EB"
Produce little endian data output.
"-mpic"
Generate PIC.
"-mno-fp-as-gp-relax"
Suppress fp-as-gp relaxation for this file.
"-mb2bb-relax"
Back-to-back branch optimization.
"-mno-all-relax"
Suppress all relaxation for this file.
"-march=<arch name>"
Assemble for architecture <arch name> which could be v3, v3j, v3m,
v3f, v3s, v2, v2j, v2f, v2s.
"-mbaseline=<baseline>"
Assemble for baseline <baseline> which could be v2, v3, v3m.
"-mfpu-freg=FREG"
Specify a FPU configuration.
"0 8 SP / 4 DP registers"
"1 16 SP / 8 DP registers"
"2 32 SP / 16 DP registers"
"3 32 SP / 32 DP registers"
"-mabi=abi"
Specify a abi version <abi> could be v1, v2, v2fp, v2fpp.
"-m[no-]mac"
Enable/Disable Multiply instructions support.
"-m[no-]div"
Enable/Disable Divide instructions support.
"-m[no-]16bit-ext"
Enable/Disable 16-bit extension
"-m[no-]dx-regs"
Enable/Disable d0/d1 registers
"-m[no-]perf-ext"
Enable/Disable Performance extension
"-m[no-]perf2-ext"
Enable/Disable Performance extension 2
"-m[no-]string-ext"
Enable/Disable String extension
"-m[no-]reduced-regs"
Enable/Disable Reduced Register configuration (GPR16) option
"-m[no-]audio-isa-ext"
Enable/Disable AUDIO ISA extension
"-m[no-]fpu-sp-ext"
Enable/Disable FPU SP extension
"-m[no-]fpu-dp-ext"
Enable/Disable FPU DP extension
"-m[no-]fpu-fma"
Enable/Disable FPU fused-multiply-add instructions
"-mall-ext"
Turn on all extensions and instructions support
The following options are available when as is configured for a PowerPC
processor.
-a32
Generate ELF32 or XCOFF32.
-a64
Generate ELF64 or XCOFF64.
-K PIC
Set EF_PPC_RELOCATABLE_LIB in ELF flags.
-mpwrx | -mpwr2
Generate code for POWER/2 (RIOS2).
-mpwr
Generate code for POWER (RIOS1)
-m601
Generate code for PowerPC 601.
-mppc, -mppc32, -m603, -m604
Generate code for PowerPC 603/604.
-m403, -m405
Generate code for PowerPC 403/405.
-m440
Generate code for PowerPC 440. BookE and some 405 instructions.
-m464
Generate code for PowerPC 464.
-m476
Generate code for PowerPC 476.
-m7400, -m7410, -m7450, -m7455
Generate code for PowerPC 7400/7410/7450/7455.
-m750cl
Generate code for PowerPC 750CL.
-m821, -m850, -m860
Generate code for PowerPC 821/850/860.
-mppc64, -m620
Generate code for PowerPC 620/625/630.
-me500, -me500x2
Generate code for Motorola e500 core complex.
-me500mc
Generate code for Freescale e500mc core complex.
-me500mc64
Generate code for Freescale e500mc64 core complex.
-me5500
Generate code for Freescale e5500 core complex.
-me6500
Generate code for Freescale e6500 core complex.
-mspe
Generate code for Motorola SPE instructions.
-mtitan
Generate code for AppliedMicro Titan core complex.
-mppc64bridge
Generate code for PowerPC 64, including bridge insns.
-mbooke
Generate code for 32-bit BookE.
-ma2
Generate code for A2 architecture.
-me300
Generate code for PowerPC e300 family.
-maltivec
Generate code for processors with AltiVec instructions.
-mvle
Generate code for Freescale PowerPC VLE instructions.
-mvsx
Generate code for processors with Vector-Scalar (VSX) instructions.
-mhtm
Generate code for processors with Hardware Transactional Memory
instructions.
-mpower4, -mpwr4
Generate code for Power4 architecture.
-mpower5, -mpwr5, -mpwr5x
Generate code for Power5 architecture.
-mpower6, -mpwr6
Generate code for Power6 architecture.
-mpower7, -mpwr7
Generate code for Power7 architecture.
-mpower8, -mpwr8
Generate code for Power8 architecture.
-mpower9, -mpwr9
Generate code for Power9 architecture.
-mcell
-mcell
Generate code for Cell Broadband Engine architecture.
-mcom
Generate code Power/PowerPC common instructions.
-many
Generate code for any architecture (PWR/PWRX/PPC).
-mregnames
Allow symbolic names for registers.
-mno-regnames
Do not allow symbolic names for registers.
-mrelocatable
Support for GCC's -mrelocatable option.
-mrelocatable-lib
Support for GCC's -mrelocatable-lib option.
-memb
Set PPC_EMB bit in ELF flags.
-mlittle, -mlittle-endian, -le
Generate code for a little endian machine.
-mbig, -mbig-endian, -be
Generate code for a big endian machine.
-msolaris
Generate code for Solaris.
-mno-solaris
Do not generate code for Solaris.
-nops=count
If an alignment directive inserts more than count nops, put a
branch at the beginning to skip execution of the nops.
See the info pages for documentation of the RX-specific options.
The following options are available when as is configured for the s390
processor family.
-m31
-m64
Select the word size, either 31/32 bits or 64 bits.
-mesa
-mzarch
Select the architecture mode, either the Enterprise System
Architecture (esa) or the z/Architecture mode (zarch).
-march=processor
Specify which s390 processor variant is the target, g6, g6, z900,
z990, z9-109, z9-ec, z10, z196, zEC12, or z13 (or arch11), or
arch12.
-mregnames
-mno-regnames
Allow or disallow symbolic names for registers.
-mwarn-areg-zero
Warn whenever the operand for a base or index register has been
specified but evaluates to zero.
The following options are available when as is configured for a
TMS320C6000 processor.
-march=arch
Enable (only) instructions from architecture arch. By default, all
instructions are permitted.
The following values of arch are accepted: "c62x", "c64x", "c64x+",
"c67x", "c67x+", "c674x".
-mdsbt
-mno-dsbt
The -mdsbt option causes the assembler to generate the
"Tag_ABI_DSBT" attribute with a value of 1, indicating that the
code is using DSBT addressing. The -mno-dsbt option, the default,
causes the tag to have a value of 0, indicating that the code does
not use DSBT addressing. The linker will emit a warning if objects
of different type (DSBT and non-DSBT) are linked together.
-mpid=no
-mpid=near
-mpid=far
The -mpid= option causes the assembler to generate the
"Tag_ABI_PID" attribute with a value indicating the form of data
addressing used by the code. -mpid=no, the default, indicates
position-dependent data addressing, -mpid=near indicates position-
independent addressing with GOT accesses using near DP addressing,
and -mpid=far indicates position-independent addressing with GOT
accesses using far DP addressing. The linker will emit a warning
if objects built with different settings of this option are linked
together.
-mpic
-mno-pic
The -mpic option causes the assembler to generate the "Tag_ABI_PIC"
attribute with a value of 1, indicating that the code is using
position-independent code addressing, The "-mno-pic" option, the
default, causes the tag to have a value of 0, indicating position-
dependent code addressing. The linker will emit a warning if
objects of different type (position-dependent and position-
independent) are linked together.
-mbig-endian
-mlittle-endian
Generate code for the specified endianness. The default is little-
endian.
The following options are available when as is configured for a TILE-Gx
processor.
-m32 | -m64
Select the word size, either 32 bits or 64 bits.
-EB | -EL
Select the endianness, either big-endian (-EB) or little-endian
(-EL).
The following option is available when as is configured for a Visium
processor.
-mtune=arch
This option specifies the target architecture. If an attempt is
made to assemble an instruction that will not execute on the target
architecture, the assembler will issue an error message.
The following names are recognized: "mcm24" "mcm" "gr5" "gr6"
The following options are available when as is configured for an Xtensa
processor.
--text-section-literals | --no-text-section-literals
Control the treatment of literal pools. The default is
--no-text-section-literals, which places literals in separate
sections in the output file. This allows the literal pool to be
placed in a data RAM/ROM. With --text-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, where the literals would otherwise be out
of range of the "L32R" instructions in the text section. Literals
are grouped into pools following ".literal_position" directives or
preceding "ENTRY" instructions. These options only affect literals
referenced via PC-relative "L32R" instructions; literals for
absolute mode "L32R" instructions are handled separately.
--auto-litpools | --no-auto-litpools
Control the treatment of literal pools. The default is
--no-auto-litpools, which in the absence of --text-section-literals
places literals in separate sections in the output file. This
allows the literal pool to be placed in a data RAM/ROM. With
--auto-litpools, the literals are interspersed in the text section
in order to keep them as close as possible to their references,
explicit ".literal_position" directives are not required. This may
be necessary for very large functions, where single literal pool at
the beginning of the function may not be reachable by "L32R"
instructions at the end. These options only affect literals
referenced via PC-relative "L32R" instructions; literals for
absolute mode "L32R" instructions are handled separately. When
used together with --text-section-literals, --auto-litpools takes
precedence.
--absolute-literals | --no-absolute-literals
Indicate to the assembler whether "L32R" instructions use absolute
or PC-relative addressing. If the processor includes the absolute
addressing option, the default is to use absolute "L32R"
relocations. Otherwise, only the PC-relative "L32R" relocations
can be used.
--target-align | --no-target-align
Enable or disable automatic alignment to reduce branch penalties at
some expense in code size. This optimization is enabled by
default. Note that the assembler will always align instructions
like "LOOP" that have fixed alignment requirements.
--longcalls | --no-longcalls
Enable or disable transformation of call instructions to allow
calls across a greater range of addresses. This option should be
used when call targets can potentially be out of range. It may
degrade both code size and performance, but the linker can
generally optimize away the unnecessary overhead when a call ends
up within range. The default is --no-longcalls.
--transform | --no-transform
Enable or disable all assembler transformations of Xtensa
instructions, including both relaxation and optimization. The
default is --transform; --no-transform should only be used in the
rare cases when the instructions must be exactly as specified in
the assembly source. Using --no-transform causes out of range
instruction operands to be errors.
--rename-section oldname=newname
Rename the oldname section to newname. This option can be used
multiple times to rename multiple sections.
--trampolines | --no-trampolines
Enable or disable transformation of jump instructions to allow
jumps across a greater range of addresses. This option should be
used when jump targets can potentially be out of range. In the
absence of such jumps this option does not affect code size or
performance. The default is --trampolines.
The following options are available when as is configured for a Z80
family processor.
-z80
Assemble for Z80 processor.
-r800
Assemble for R800 processor.
-ignore-undocumented-instructions
-Wnud
Assemble undocumented Z80 instructions that also work on R800
without warning.
-ignore-unportable-instructions
-Wnup
Assemble all undocumented Z80 instructions without warning.
-warn-undocumented-instructions
-Wud
Issue a warning for undocumented Z80 instructions that also work on
R800.
-warn-unportable-instructions
-Wup
Issue a warning for undocumented Z80 instructions that do not work
on R800.
-forbid-undocumented-instructions
-Fud
Treat all undocumented instructions as errors.
-forbid-unportable-instructions
-Fup
Treat undocumented Z80 instructions that do not work on R800 as
errors.
SEE ALSO
gcc(1), ld(1), and the Info entries for binutils and ld.
COPYRIGHT
Copyright (c) 1991-2016 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 no
Invariant Sections, with no Front-Cover Texts, and with no Back-Cover
Texts. A copy of the license is included in the section entitled "GNU
Free Documentation License".
binutils-2.27 2023-10-09 AS(1)
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