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The Free Software Foundation Inc. thanks The Nice Computer Company of Australia for loaning Dean Elsner to write the first (Vax) version of as for Project GNU. The proprietors, management and staff of TNCCA thank FSF for distracting the boss while they got some work done.

Permission is granted to make and distribute verbatim copies of this manual provided the copyright notice and this permission notice are preserved on all copies.

Permission is granted to copy and distribute modified versions of this manual under the conditions for verbatim copying, provided that the entire resulting derived work is distributed under the terms of a permission notice identical to this one.

Permission is granted to copy and distribute translations of this manual into another language, under the above conditions for modified versions.

Overview

This manual is a user guide to the GNU assembler as.

Here is a brief summary of how to invoke as. For details, see section Command-Line Options.

as [ -a[cdhlns][=file] ] [ -D ]  [ --defsym sym=val ]
 [ -f ] [ --gstabs ] [ --help ] [ -I dir ] [ -J ] [ -K ] [ -L ]
 [ --keep-locals ] [ -o objfile ] [ -R ] [ --statistics ] [ -v ]
 [ -version ] [ --version ] [ -W ] [ -w ] [ -x ] [ -Z ]
 [ -mbig-endian | -mlittle-endian ]
 [ -m[arm]1 | -m[arm]2 | -m[arm]250 | -m[arm]3 | -m[arm]6 | -m[arm]7[t][[d]m[i]] ]
 [ -m[arm]v2 | -m[arm]v2a | -m[arm]v3 | -m[arm]v3m | -m[arm]v4 | -m[arm]v4t ]
 [ -mthumb | -mall ]
 [ -mfpa10 | -mfpa11 | -mfpe-old | -mno-fpu ]
 [ -EB | -EL ]
 [ -mapcs-32 | -mapcs-26 ]
 [ -O ]
 [ -Av6 | -Av7 | -Av8 | -Asparclet | -Asparclite
   -Av8plus | -Av8plusa | -Av9 | -Av9a ]
 [ -xarch=v8plus | -xarch=v8plusa ] [ -bump ] [ -32 | -64 ]
 [ -ACA | -ACA_A | -ACB | -ACC | -AKA | -AKB | -AKC | -AMC ]
 [ -b ] [ -no-relax ]
 [ -l ] [ -m68000 | -m68010 | -m68020 | ... ]
 [ -nocpp ] [ -EL ] [ -EB ] [ -G num ] [ -mcpu=CPU ]
 [ -mips1 ] [ -mips2 ] [ -mips3 ] [ -m4650 ] [ -no-m4650 ]
 [ --trap ] [ --break ]
 [ --emulation=name ]
 [ -- | files ... ]

-a[cdhlmns]

Turn on listings, in any of a variety of ways:

-ac: omit false conditionals
-ad: omit debugging directives
-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'.

-D

Ignored. This option is accepted for script compatibility with calls to other assemblers.

--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.

-f

"fast"---skip whitespace and comment preprocessing (assume source is compiler output).

--gstabs

Generate stabs debugging information for each assembler line. This may help debugging assembler code, if the debugger can handle it.

--help

Print a summary of the command line 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. On traditional a.out systems these start with `L', but different systems have different local label prefixes.

-o objfile

Name the object-file output from as objfile.

-R

Fold the data section into the text section.

--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

Suppress warning messages.

-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 an ARC processor.

-mbig-endian: Generate "big endian" format output.
-mlittle-endian: Generate "little endian" format output.

The following options are available when as is configured for the ARM processor family.

-m[arm]1 | -m[arm]2 | -m[arm]250 | -m[arm]3 | -m[arm]6 | -m[arm]7[t][[d]m] | -m[arm]v2 | -m[arm]v2a | -m[arm]v3 | -m[arm]v3m | -m[arm]v4 | -m[arm]v4t: Specify which variant of the ARM architecture is the target.
-mthumb | -mall: Enable or disable Thumb only instruction decoding.
-mfpa10 | -mfpa11 | -mfpe-old | -mno-fpu: Select which Floating Point architcture is the target.
-mapcs-32 | -mapcs-26: Select which procedure calling convention is in use.
-EB | -EL: Select either big-endian (-EB) or little-endian (-EL) output.

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 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 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 the SPARC architecture:

-Av6 | -Av7 | -Av8 | -Asparclet | -Asparclite
-Av8plus | -Av8plusa | -Av9 | -Av9a: Explicitly select a variant of the SPARC architecture. `-Av8plus' and `-Av8plusa' select a 32 bit environment. `-Av9' and `-Av9a' select a 64 bit environment. `-Av8plusa' and `-Av9a' enable the SPARC V9 instruction set with UltraSPARC extensions.
-xarch=v8plus | -xarch=v8plusa: For compatibility with the Solaris v9 assembler. These options are equivalent to -Av8plus and -Av8plusa, respectively.
-bump: Warn when the assembler switches to another architecture.

The following options are available when as is configured for a MIPS processor.

-G num: This option sets the largest size of an object that can be referenced implicitly with the gp register. It is only accepted for targets that use ECOFF format, such as a DECstation running Ultrix. The default value is 8.
-EB: Generate "big endian" format output.
-EL: Generate "little endian" format output.
-mips1
-mips2
-mips3: Generate code for a particular MIPS Instruction Set Architecture level. `-mips1' corresponds to the R2000 and R3000 processors, `-mips2' to the R6000 processor, and `-mips3' to the R4000 processor.
-m4650
-no-m4650: Generate code for the MIPS R4650 chip. This tells the assembler to accept the `mad' and `madu' instruction, and to not schedule `nop' instructions around accesses to the `HI' and `LO' registers. `-no-m4650' turns off this option.
-mcpu=CPU: Generate code for a particular MIPS cpu. This has little effect on the assembler, but it is passed by gcc.
--emulation=name: This option causes as to emulate as configured for some other target, in all respects, including output format (choosing between ELF and ECOFF only), handling of pseudo-opcodes which may generate debugging information or store symbol table information, and default endianness. The available configuration names are: `mipsecoff', `mipself', `mipslecoff', `mipsbecoff', `mipslelf', `mipsbelf'. The first two do not alter the default endianness from that of the primary target for which the assembler was configured; the others change the default to little- or big-endian as indicated by the `b' or `l' in the name. Using `-EB' or `-EL' will override the endianness selection in any case. This option is currently supported only when the primary target as is configured for is a MIPS ELF or ECOFF target. Furthermore, the primary target or others specified with `--enable-targets=...' at configuration time must include support for the other format, if both are to be available. For example, the Irix 5 configuration includes support for both. Eventually, this option will support more configurations, with more fine-grained control over the assembler's behavior, and will be supported for more processors.
-nocpp: as ignores this option. It is accepted for compatibility with the native tools.
--trap
--no-trap
--break
--no-break: Control how to deal with multiplication overflow and division by zero. `--trap' or `--no-break' (which are synonyms) take a trap exception (and only work for Instruction Set Architecture level 2 and higher); `--break' or `--no-trap' (also synonyms, and the default) take a break exception.

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