AS(1)

NAME
AS - the portable GNU assembler.

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 for use by the linker . 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 (version 2), 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 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

-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.

--gdwarf2
    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.

--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  This option is accepted but has no effect on the TARGET family.

-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
--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 an ARC processor.

-marc[5|6|7|8]
    This option selects the core processor variant.

-EB | -EL
    Select either big-endian (-EB) or little-endian (-EL) output.

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

-m[arm][1|2|3|6|7|8|9][...]
    Specify which ARM processor variant is the target.

-m[arm]v[2|2a|3|3m|4|4t|5|5t]
    Specify which ARM architecture variant is used by the target.

-mthumb | -mall
    Enable or disable Thumb only instruction decoding.

-mfpa10 | -mfpa11 | -mfpe-old | -mno-fpu
    Select which Floating Point architecture is the target.

-mapcs-32 | -mapcs-26 | -mapcs-float | -mapcs-reentrant | -moabi
    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.

-k  Specify that PIC code has been generated.

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 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 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 a picoJava processor.

-mb Generate ``big endian'' format output.

-ml Generate ``little endian'' format output.

The following options are available when as is configured for the Motorola 68HC11 or 68HC12 series.

-m68hc11 | -m68hc12
    Specify what processor is the target. The default is defined by the configuration option when building the assembler.

--force-long-branchs
    Relative branches are turned into absolute ones. This concerns conditional branches, unconditional branches and branches to a sub routine.

-S | --short-branchs
    Do not turn relative branchs into absolute ones when the offset is out of range.

--strict-direct-mode
    Do not turn the direct addressing mode into extended addressing mode when the instruction does not support direct addressing mode.

--print-insn-syntax
    Print the syntax of instruction in case of error.

--print-opcodes
    print the list of instructions with syntax and then exit.

--generate-example
    print an example of instruction for each possible instruction and then exit. This option is only useful for testing as.

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
-mips4
-mips32
    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. -mips5, -mips32, and -mips64 correspond to generic MIPS V, MIPS32, and MIPS64 ISA processors, respectively.

-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. It is exactly equivalent to -mcpu, except that there are more value of cpu understood.

--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.

The following options are available when as is configured for an MCore processor.

-jsri2bsr
-nojsri2bsr
    Enable or disable the JSRI to BSR transformation. By default this is enabled. The command line option -nojsri2bsr can be used to disable it.

-sifilter
-nosifilter
    Enable or disable the silicon filter behaviour. By default this is disabled. The default can be overridden by the -sifilter command line option.

-relax
    Alter jump instructions for long displacements.

-mcpu=[210|340]
    Select the cpu type on the target hardware. This controls which instructions can be assembled.

-EB Assemble for a big endian target.

-EL Assemble for a little endian target.

SEE ALSO
gcc(1), ld(1), and the Info entries for binutils and ld.

COPYRIGHT
Copyright (C) 1991, 92, 93, 94, 95, 96, 97, 98, 99, 2000, 2001 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 1.1 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".