Overview of as, the GNU Assembler
The following documentation serves as a overview to the user guide for the GNU assembler, as.
The following summarizes briefly how to invoke as. For details, see Command-Line Options.
as [ -a[dhlns][=file] ] [ -D
] [ --defsym sym= val ]
[ -f ] [ --help ] [ -I dir ][-J][-K ][-L ]
[ -o objfile ] [ -R ] [ --statistics ] [ -v ]
[ -version ]
[ --version ] [ -W ] [ -w ] [ -x ] [ -Z ]
[ -Av6 | -Av7 | -Av8 | -Asparclite | -Av9 | -Av9a ]
[ -xarch=v8plus | -xarch=v8plusa ] [ -bump ]
[ -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[dhlns]
Turn on listings, in any of a variety of ways:
-ad
omit debugging
ffb
directives
-ah
include high-level
source
-al
include assembly
-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—that is, all listings turned on.
-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).
--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 (in the symbol
table) local symbols, starting with L.
-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.
-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 the Intel 80960 processor.
-ACA | -ACA_A | -ACB | -ACC |
-AKA | -AKB | -AKC | -AMC
Specify which
variant of the 960 architecture is the target. For target variant
-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 configuring as for the Motorola 68000 series.
-l
Shorten references
to undefined symbols, to one word instead of two.
-m68000 | -m68008 | -m68010 |
-m68020 | -m68030 | -m68040 |
-m68302 | -m68331 | -m68332 | -m68333 | -m68340 | -mcpu32
Specify what processor
in the 68000 family is the target. The default is normally the 68020, but
this can be changed at
ffb
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 | -Asparclite
| -Av9 | -Av9a
Explicitly select
a variant of the SPARC architecture.
-xarch=v8plus | -xarch=v8plusa
For compatibility
with the Solaris v9 assembler. These options are equivalent to -Av9
and -Av9a,
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
--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.