1 \input texinfo @c -*-Texinfo-*-
2 @c Copyright 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999, 2000,
4 @c Free Software Foundation, Inc.
5 @c UPDATE!! On future updates--
6 @c (1) check for new machine-dep cmdline options in
7 @c md_parse_option definitions in config/tc-*.c
8 @c (2) for platform-specific directives, examine md_pseudo_op
10 @c (3) for object-format specific directives, examine obj_pseudo_op
12 @c (4) portable directives in potable[] in read.c
16 @macro gcctabopt{body}
19 @c defaults, config file may override:
22 @include asconfig.texi
27 @c Configure for the generation of man pages
65 @c common OR combinations of conditions
91 @set abnormal-separator
95 @settitle Using @value{AS}
98 @settitle Using @value{AS} (@value{TARGET})
100 @setchapternewpage odd
105 @c WARE! Some of the machine-dependent sections contain tables of machine
106 @c instructions. Except in multi-column format, these tables look silly.
107 @c Unfortunately, Texinfo doesn't have a general-purpose multi-col format, so
108 @c the multi-col format is faked within @example sections.
110 @c Again unfortunately, the natural size that fits on a page, for these tables,
111 @c is different depending on whether or not smallbook is turned on.
112 @c This matters, because of order: text flow switches columns at each page
115 @c The format faked in this source works reasonably well for smallbook,
116 @c not well for the default large-page format. This manual expects that if you
117 @c turn on @smallbook, you will also uncomment the "@set SMALL" to enable the
118 @c tables in question. You can turn on one without the other at your
119 @c discretion, of course.
122 @c the insn tables look just as silly in info files regardless of smallbook,
123 @c might as well show 'em anyways.
129 * As: (as). The GNU assembler.
130 * Gas: (as). The GNU assembler.
139 This file documents the GNU Assembler "@value{AS}".
141 @c man begin COPYRIGHT
142 Copyright (C) 1991, 92, 93, 94, 95, 96, 97, 98, 99, 2000, 2001, 2002 Free Software Foundation, Inc.
144 Permission is granted to copy, distribute and/or modify this document
145 under the terms of the GNU Free Documentation License, Version 1.1
146 or any later version published by the Free Software Foundation;
147 with no Invariant Sections, with no Front-Cover Texts, and with no
148 Back-Cover Texts. A copy of the license is included in the
149 section entitled ``GNU Free Documentation License''.
154 Permission is granted to process this file through Tex and print the
155 results, provided the printed document carries copying permission
156 notice identical to this one except for the removal of this paragraph
157 (this paragraph not being relevant to the printed manual).
163 @title Using @value{AS}
164 @subtitle The @sc{gnu} Assembler
166 @subtitle for the @value{TARGET} family
169 @subtitle Version @value{VERSION}
172 The Free Software Foundation Inc. thanks The Nice Computer
173 Company of Australia for loaning Dean Elsner to write the
174 first (Vax) version of @command{as} for Project @sc{gnu}.
175 The proprietors, management and staff of TNCCA thank FSF for
176 distracting the boss while they got some work
179 @author Dean Elsner, Jay Fenlason & friends
183 \hfill {\it Using {\tt @value{AS}}}\par
184 \hfill Edited by Cygnus Support\par
186 %"boxit" macro for figures:
187 %Modified from Knuth's ``boxit'' macro from TeXbook (answer to exercise 21.3)
188 \gdef\boxit#1#2{\vbox{\hrule\hbox{\vrule\kern3pt
189 \vbox{\parindent=0pt\parskip=0pt\hsize=#1\kern3pt\strut\hfil
190 #2\hfil\strut\kern3pt}\kern3pt\vrule}\hrule}}%box with visible outline
191 \gdef\ibox#1#2{\hbox to #1{#2\hfil}\kern8pt}% invisible box
194 @vskip 0pt plus 1filll
195 Copyright @copyright{} 1991, 92, 93, 94, 95, 96, 97, 98, 99, 2000, 2001, 2002 Free Software Foundation, Inc.
197 Permission is granted to copy, distribute and/or modify this document
198 under the terms of the GNU Free Documentation License, Version 1.1
199 or any later version published by the Free Software Foundation;
200 with no Invariant Sections, with no Front-Cover Texts, and with no
201 Back-Cover Texts. A copy of the license is included in the
202 section entitled ``GNU Free Documentation License''.
208 @top Using @value{AS}
210 This file is a user guide to the @sc{gnu} assembler @command{@value{AS}} version
213 This version of the file describes @command{@value{AS}} configured to generate
214 code for @value{TARGET} architectures.
217 This document is distributed under the terms of the GNU Free
218 Documentation License. A copy of the license is included in the
219 section entitled ``GNU Free Documentation License''.
222 * Overview:: Overview
223 * Invoking:: Command-Line Options
225 * Sections:: Sections and Relocation
227 * Expressions:: Expressions
228 * Pseudo Ops:: Assembler Directives
229 * Machine Dependencies:: Machine Dependent Features
230 * Reporting Bugs:: Reporting Bugs
231 * Acknowledgements:: Who Did What
232 * GNU Free Documentation License:: GNU Free Documentation License
240 This manual is a user guide to the @sc{gnu} assembler @command{@value{AS}}.
242 This version of the manual describes @command{@value{AS}} configured to generate
243 code for @value{TARGET} architectures.
247 @cindex invocation summary
248 @cindex option summary
249 @cindex summary of options
250 Here is a brief summary of how to invoke @command{@value{AS}}. For details,
251 @pxref{Invoking,,Command-Line Options}.
253 @c man title AS the portable GNU assembler.
257 gcc(1), ld(1), and the Info entries for @file{binutils} and @file{ld}.
261 @c We don't use deffn and friends for the following because they seem
262 @c to be limited to one line for the header.
264 @c man begin SYNOPSIS
265 @value{AS} [@b{-a}[@b{cdhlns}][=@var{file}]] [@b{-D}] [@b{--defsym} @var{sym}=@var{val}]
266 [@b{-f}] [@b{--gstabs}] [@b{--gdwarf2}] [@b{--help}] [@b{-I} @var{dir}]
267 [@b{-J}] [@b{-K}] [@b{-L}]
268 [@b{--listing-lhs-width}=@var{NUM}] [@b{--listing-lhs-width2}=@var{NUM}]
269 [@b{--listing-rhs-width}=@var{NUM}] [@b{--listing-cont-lines}=@var{NUM}]
270 [@b{--keep-locals}] [@b{-o} @var{objfile}] [@b{-R}] [@b{--statistics}] [@b{-v}]
271 [@b{-version}] [@b{--version}] [@b{-W}] [@b{--warn}] [@b{--fatal-warnings}]
272 [@b{-w}] [@b{-x}] [@b{-Z}] [@b{--target-help}] [@var{target-options}]
273 [@b{--}|@var{files} @dots{}]
275 @c Target dependent options are listed below. Keep the list sorted.
276 @c Add an empty line for separation.
278 @c am29k has no machine-dependent assembler options
282 @emph{Target Alpha options:}
284 [@b{-mdebug} | @b{-no-mdebug}]
285 [@b{-relax}] [@b{-g}] [@b{-G@var{size}}]
286 [@b{-F}] [@b{-32addr}]
290 @emph{Target ARC options:}
296 @emph{Target ARM options:}
297 @c Don't document the deprecated options
298 [@b{-mcpu}=@var{processor}[+@var{extension}@dots{}]]
299 [@b{-march}=@var{architecture}[+@var{extension}@dots{}]]
300 [@b{-mfpu}=@var{floating-point-fromat}]
303 [@b{-mapcs-32}|@b{-mapcs-26}|@b{-mapcs-float}|
304 @b{-mapcs-reentrant}]
305 [@b{-mthumb-interwork}] [@b{-moabi}] [@b{-k}]
309 @emph{Target CRIS options:}
310 [@b{--underscore} | @b{--no-underscore}]
312 [@b{--emulation=criself} | @b{--emulation=crisaout}]
313 @c Deprecated -- deliberately not documented.
318 @emph{Target D10V options:}
323 @emph{Target D30V options:}
324 [@b{-O}|@b{-n}|@b{-N}]
327 @c Renesas family chips have no machine-dependent assembler options
330 @c HPPA has no machine-dependent assembler options (yet).
334 @emph{Target i386 options:}
339 @emph{Target i960 options:}
340 @c see md_parse_option in tc-i960.c
341 [@b{-ACA}|@b{-ACA_A}|@b{-ACB}|@b{-ACC}|@b{-AKA}|@b{-AKB}|
343 [@b{-b}] [@b{-no-relax}]
347 @emph{Target IA-64 options:}
348 [@b{-mconstant-gp}|@b{-mauto-pic}]
349 [@b{-milp32}|@b{-milp64}|@b{-mlp64}|@b{-mp64}]
351 [@b{-x}|@b{-xexplicit}] [@b{-xauto}] [@b{-xdebug}]
355 @emph{Target IP2K options:}
356 [@b{-mip2022}|@b{-mip2022ext}]
360 @emph{Target M32R options:}
361 [@b{--m32rx}|@b{--[no-]warn-explicit-parallel-conflicts}|
366 @emph{Target M680X0 options:}
367 [@b{-l}] [@b{-m68000}|@b{-m68010}|@b{-m68020}|@dots{}]
371 @emph{Target M68HC11 options:}
372 [@b{-m68hc11}|@b{-m68hc12}|@b{-m68hcs12}]
373 [@b{-mshort}|@b{-mlong}]
374 [@b{-mshort-double}|@b{-mlong-double}]
375 [@b{--force-long-branchs}] [@b{--short-branchs}]
376 [@b{--strict-direct-mode}] [@b{--print-insn-syntax}]
377 [@b{--print-opcodes}] [@b{--generate-example}]
381 @emph{Target MCORE options:}
382 [@b{-jsri2bsr}] [@b{-sifilter}] [@b{-relax}]
383 [@b{-mcpu=[210|340]}]
387 @emph{Target MIPS options:}
388 [@b{-nocpp}] [@b{-EL}] [@b{-EB}] [@b{-n}] [@b{-O}[@var{optimization level}]]
389 [@b{-g}[@var{debug level}]] [@b{-G} @var{num}] [@b{-KPIC}] [@b{-call_shared}]
390 [@b{-non_shared}] [@b{-xgot}] [@b{--membedded-pic}]
391 [@b{-mabi}=@var{ABI}] [@b{-32}] [@b{-n32}] [@b{-64}] [@b{-mfp32}] [@b{-mgp32}]
392 [@b{-march}=@var{CPU}] [@b{-mtune}=@var{CPU}] [@b{-mips1}] [@b{-mips2}]
393 [@b{-mips3}] [@b{-mips4}] [@b{-mips5}] [@b{-mips32}] [@b{-mips32r2}]
395 [@b{-construct-floats}] [@b{-no-construct-floats}]
396 [@b{-trap}] [@b{-no-break}] [@b{-break}] [@b{-no-trap}]
397 [@b{-mfix7000}] [@b{-mno-fix7000}]
398 [@b{-mips16}] [@b{-no-mips16}]
399 [@b{-mips3d}] [@b{-no-mips3d}]
400 [@b{-mdmx}] [@b{-no-mdmx}]
401 [@b{-mdebug}] [@b{-no-mdebug}]
405 @emph{Target MMIX options:}
406 [@b{--fixed-special-register-names}] [@b{--globalize-symbols}]
407 [@b{--gnu-syntax}] [@b{--relax}] [@b{--no-predefined-symbols}]
408 [@b{--no-expand}] [@b{--no-merge-gregs}] [@b{-x}]
409 [@b{--linker-allocated-gregs}]
413 @emph{Target PDP11 options:}
414 [@b{-mpic}|@b{-mno-pic}] [@b{-mall}] [@b{-mno-extensions}]
415 [@b{-m}@var{extension}|@b{-mno-}@var{extension}]
416 [@b{-m}@var{cpu}] [@b{-m}@var{machine}]
420 @emph{Target picoJava options:}
425 @emph{Target PowerPC options:}
426 [@b{-mpwrx}|@b{-mpwr2}|@b{-mpwr}|@b{-m601}|@b{-mppc}|@b{-mppc32}|@b{-m603}|@b{-m604}|
427 @b{-m403}|@b{-m405}|@b{-mppc64}|@b{-m620}|@b{-mppc64bridge}|@b{-mbooke}|
428 @b{-mbooke32}|@b{-mbooke64}]
429 [@b{-mcom}|@b{-many}|@b{-maltivec}] [@b{-memb}]
430 [@b{-mregnames}|@b{-mno-regnames}]
431 [@b{-mrelocatable}|@b{-mrelocatable-lib}]
432 [@b{-mlittle}|@b{-mlittle-endian}|@b{-mbig}|@b{-mbig-endian}]
433 [@b{-msolaris}|@b{-mno-solaris}]
437 @emph{Target SPARC options:}
438 @c The order here is important. See c-sparc.texi.
439 [@b{-Av6}|@b{-Av7}|@b{-Av8}|@b{-Asparclet}|@b{-Asparclite}
440 @b{-Av8plus}|@b{-Av8plusa}|@b{-Av9}|@b{-Av9a}]
441 [@b{-xarch=v8plus}|@b{-xarch=v8plusa}] [@b{-bump}]
446 @emph{Target TIC54X options:}
447 [@b{-mcpu=54[123589]}|@b{-mcpu=54[56]lp}] [@b{-mfar-mode}|@b{-mf}]
448 [@b{-merrors-to-file} @var{<filename>}|@b{-me} @var{<filename>}]
451 @c Z8000 has no machine-dependent assembler options
455 @emph{Target Xtensa options:}
456 [@b{--[no-]density}] [@b{--[no-]relax}] [@b{--[no-]generics}]
457 [@b{--[no-]text-section-literals}]
458 [@b{--[no-]target-align}] [@b{--[no-]longcalls}]
467 Turn on listings, in any of a variety of ways:
471 omit false conditionals
474 omit debugging directives
477 include high-level source
483 include macro expansions
486 omit forms processing
492 set the name of the listing file
495 You may combine these options; for example, use @samp{-aln} for assembly
496 listing without forms processing. The @samp{=file} option, if used, must be
497 the last one. By itself, @samp{-a} defaults to @samp{-ahls}.
500 Ignored. This option is accepted for script compatibility with calls to
503 @item --defsym @var{sym}=@var{value}
504 Define the symbol @var{sym} to be @var{value} before assembling the input file.
505 @var{value} must be an integer constant. As in C, a leading @samp{0x}
506 indicates a hexadecimal value, and a leading @samp{0} indicates an octal value.
509 ``fast''---skip whitespace and comment preprocessing (assume source is
513 Generate stabs debugging information for each assembler line. This
514 may help debugging assembler code, if the debugger can handle it.
517 Generate DWARF2 debugging information for each assembler line. This
518 may help debugging assembler code, if the debugger can handle it. Note---this
519 option is only supported by some targets, not all of them.
522 Print a summary of the command line options and exit.
525 Print a summary of all target specific options and exit.
528 Add directory @var{dir} to the search list for @code{.include} directives.
531 Don't warn about signed overflow.
534 @ifclear DIFF-TBL-KLUGE
535 This option is accepted but has no effect on the @value{TARGET} family.
537 @ifset DIFF-TBL-KLUGE
538 Issue warnings when difference tables altered for long displacements.
543 Keep (in the symbol table) local symbols. On traditional a.out systems
544 these start with @samp{L}, but different systems have different local
547 @item --listing-lhs-width=@var{number}
548 Set the maximum width, in words, of the output data column for an assembler
549 listing to @var{number}.
551 @item --listing-lhs-width2=@var{number}
552 Set the maximum width, in words, of the output data column for continuation
553 lines in an assembler listing to @var{number}.
555 @item --listing-rhs-width=@var{number}
556 Set the maximum width of an input source line, as displayed in a listing, to
559 @item --listing-cont-lines=@var{number}
560 Set the maximum number of lines printed in a listing for a single line of input
563 @item -o @var{objfile}
564 Name the object-file output from @command{@value{AS}} @var{objfile}.
567 Fold the data section into the text section.
570 Print the maximum space (in bytes) and total time (in seconds) used by
573 @item --strip-local-absolute
574 Remove local absolute symbols from the outgoing symbol table.
578 Print the @command{as} version.
581 Print the @command{as} version and exit.
585 Suppress warning messages.
587 @item --fatal-warnings
588 Treat warnings as errors.
591 Don't suppress warning messages or treat them as errors.
600 Generate an object file even after errors.
602 @item -- | @var{files} @dots{}
603 Standard input, or source files to assemble.
608 The following options are available when @value{AS} is configured for
613 This option selects the core processor variant.
615 Select either big-endian (-EB) or little-endian (-EL) output.
620 The following options are available when @value{AS} is configured for the ARM
624 @item -mcpu=@var{processor}[+@var{extension}@dots{}]
625 Specify which ARM processor variant is the target.
626 @item -march=@var{architecture}[+@var{extension}@dots{}]
627 Specify which ARM architecture variant is used by the target.
628 @item -mfpu=@var{floating-point-format}
629 Select which Floating Point architecture is the target.
631 Enable Thumb only instruction decoding.
632 @item -mapcs-32 | -mapcs-26 | -mapcs-float | -mapcs-reentrant | -moabi
633 Select which procedure calling convention is in use.
635 Select either big-endian (-EB) or little-endian (-EL) output.
636 @item -mthumb-interwork
637 Specify that the code has been generated with interworking between Thumb and
640 Specify that PIC code has been generated.
645 See the info pages for documentation of the CRIS-specific options.
649 The following options are available when @value{AS} is configured for
652 @cindex D10V optimization
653 @cindex optimization, D10V
655 Optimize output by parallelizing instructions.
660 The following options are available when @value{AS} is configured for a D30V
663 @cindex D30V optimization
664 @cindex optimization, D30V
666 Optimize output by parallelizing instructions.
670 Warn when nops are generated.
672 @cindex D30V nops after 32-bit multiply
674 Warn when a nop after a 32-bit multiply instruction is generated.
679 The following options are available when @value{AS} is configured for the
680 Intel 80960 processor.
683 @item -ACA | -ACA_A | -ACB | -ACC | -AKA | -AKB | -AKC | -AMC
684 Specify which variant of the 960 architecture is the target.
687 Add code to collect statistics about branches taken.
690 Do not alter compare-and-branch instructions for long displacements;
697 The following options are available when @value{AS} is configured for the
703 Specifies that the extended IP2022 instructions are allowed.
706 Restores the default behaviour, which restricts the permitted instructions to
707 just the basic IP2022 ones.
713 The following options are available when @value{AS} is configured for the
714 Mitsubishi M32R series.
719 Specify which processor in the M32R family is the target. The default
720 is normally the M32R, but this option changes it to the M32RX.
722 @item --warn-explicit-parallel-conflicts or --Wp
723 Produce warning messages when questionable parallel constructs are
726 @item --no-warn-explicit-parallel-conflicts or --Wnp
727 Do not produce warning messages when questionable parallel constructs are
734 The following options are available when @value{AS} is configured for the
735 Motorola 68000 series.
740 Shorten references to undefined symbols, to one word instead of two.
742 @item -m68000 | -m68008 | -m68010 | -m68020 | -m68030
743 @itemx | -m68040 | -m68060 | -m68302 | -m68331 | -m68332
744 @itemx | -m68333 | -m68340 | -mcpu32 | -m5200
745 Specify what processor in the 68000 family is the target. The default
746 is normally the 68020, but this can be changed at configuration time.
748 @item -m68881 | -m68882 | -mno-68881 | -mno-68882
749 The target machine does (or does not) have a floating-point coprocessor.
750 The default is to assume a coprocessor for 68020, 68030, and cpu32. Although
751 the basic 68000 is not compatible with the 68881, a combination of the
752 two can be specified, since it's possible to do emulation of the
753 coprocessor instructions with the main processor.
755 @item -m68851 | -mno-68851
756 The target machine does (or does not) have a memory-management
757 unit coprocessor. The default is to assume an MMU for 68020 and up.
764 For details about the PDP-11 machine dependent features options,
765 see @ref{PDP-11-Options}.
768 @item -mpic | -mno-pic
769 Generate position-independent (or position-dependent) code. The
770 default is @option{-mpic}.
773 @itemx -mall-extensions
774 Enable all instruction set extensions. This is the default.
776 @item -mno-extensions
777 Disable all instruction set extensions.
779 @item -m@var{extension} | -mno-@var{extension}
780 Enable (or disable) a particular instruction set extension.
783 Enable the instruction set extensions supported by a particular CPU, and
784 disable all other extensions.
786 @item -m@var{machine}
787 Enable the instruction set extensions supported by a particular machine
788 model, and disable all other extensions.
794 The following options are available when @value{AS} is configured for
795 a picoJava processor.
799 @cindex PJ endianness
800 @cindex endianness, PJ
801 @cindex big endian output, PJ
803 Generate ``big endian'' format output.
805 @cindex little endian output, PJ
807 Generate ``little endian'' format output.
813 The following options are available when @value{AS} is configured for the
814 Motorola 68HC11 or 68HC12 series.
818 @item -m68hc11 | -m68hc12 | -m68hcs12
819 Specify what processor is the target. The default is
820 defined by the configuration option when building the assembler.
823 Specify to use the 16-bit integer ABI.
826 Specify to use the 32-bit integer ABI.
829 Specify to use the 32-bit double ABI.
832 Specify to use the 64-bit double ABI.
834 @item --force-long-branchs
835 Relative branches are turned into absolute ones. This concerns
836 conditional branches, unconditional branches and branches to a
839 @item -S | --short-branchs
840 Do not turn relative branchs into absolute ones
841 when the offset is out of range.
843 @item --strict-direct-mode
844 Do not turn the direct addressing mode into extended addressing mode
845 when the instruction does not support direct addressing mode.
847 @item --print-insn-syntax
848 Print the syntax of instruction in case of error.
850 @item --print-opcodes
851 print the list of instructions with syntax and then exit.
853 @item --generate-example
854 print an example of instruction for each possible instruction and then exit.
855 This option is only useful for testing @command{@value{AS}}.
861 The following options are available when @command{@value{AS}} is configured
862 for the SPARC architecture:
865 @item -Av6 | -Av7 | -Av8 | -Asparclet | -Asparclite
866 @itemx -Av8plus | -Av8plusa | -Av9 | -Av9a
867 Explicitly select a variant of the SPARC architecture.
869 @samp{-Av8plus} and @samp{-Av8plusa} select a 32 bit environment.
870 @samp{-Av9} and @samp{-Av9a} select a 64 bit environment.
872 @samp{-Av8plusa} and @samp{-Av9a} enable the SPARC V9 instruction set with
873 UltraSPARC extensions.
875 @item -xarch=v8plus | -xarch=v8plusa
876 For compatibility with the Solaris v9 assembler. These options are
877 equivalent to -Av8plus and -Av8plusa, respectively.
880 Warn when the assembler switches to another architecture.
885 The following options are available when @value{AS} is configured for the 'c54x
890 Enable extended addressing mode. All addresses and relocations will assume
891 extended addressing (usually 23 bits).
892 @item -mcpu=@var{CPU_VERSION}
893 Sets the CPU version being compiled for.
894 @item -merrors-to-file @var{FILENAME}
895 Redirect error output to a file, for broken systems which don't support such
896 behaviour in the shell.
901 The following options are available when @value{AS} is configured for
902 a @sc{mips} processor.
906 This option sets the largest size of an object that can be referenced
907 implicitly with the @code{gp} register. It is only accepted for targets that
908 use ECOFF format, such as a DECstation running Ultrix. The default value is 8.
910 @cindex MIPS endianness
911 @cindex endianness, MIPS
912 @cindex big endian output, MIPS
914 Generate ``big endian'' format output.
916 @cindex little endian output, MIPS
918 Generate ``little endian'' format output.
929 Generate code for a particular @sc{mips} Instruction Set Architecture level.
930 @samp{-mips1} is an alias for @samp{-march=r3000}, @samp{-mips2} is an
931 alias for @samp{-march=r6000}, @samp{-mips3} is an alias for
932 @samp{-march=r4000} and @samp{-mips4} is an alias for @samp{-march=r8000}.
933 @samp{-mips5}, @samp{-mips32}, @samp{-mips32r2}, and @samp{-mips64}
934 correspond to generic
935 @samp{MIPS V}, @samp{MIPS32}, @samp{MIPS32 Release 2}, and
936 @samp{MIPS64} ISA processors,
939 @item -march=@var{CPU}
940 Generate code for a particular @sc{mips} cpu.
942 @item -mtune=@var{cpu}
943 Schedule and tune for a particular @sc{mips} cpu.
947 Cause nops to be inserted if the read of the destination register
948 of an mfhi or mflo instruction occurs in the following two instructions.
952 Cause stabs-style debugging output to go into an ECOFF-style .mdebug
953 section instead of the standard ELF .stabs sections.
957 The register sizes are normally inferred from the ISA and ABI, but these
958 flags force a certain group of registers to be treated as 32 bits wide at
959 all times. @samp{-mgp32} controls the size of general-purpose registers
960 and @samp{-mfp32} controls the size of floating-point registers.
964 Generate code for the MIPS 16 processor. This is equivalent to putting
965 @code{.set mips16} at the start of the assembly file. @samp{-no-mips16}
966 turns off this option.
970 Generate code for the MIPS-3D Application Specific Extension.
971 This tells the assembler to accept MIPS-3D instructions.
972 @samp{-no-mips3d} turns off this option.
976 Generate code for the MDMX Application Specific Extension.
977 This tells the assembler to accept MDMX instructions.
978 @samp{-no-mdmx} turns off this option.
980 @item --construct-floats
981 @itemx --no-construct-floats
982 The @samp{--no-construct-floats} option disables the construction of
983 double width floating point constants by loading the two halves of the
984 value into the two single width floating point registers that make up
985 the double width register. By default @samp{--construct-floats} is
986 selected, allowing construction of these floating point constants.
989 @item --emulation=@var{name}
990 This option causes @command{@value{AS}} to emulate @command{@value{AS}} configured
991 for some other target, in all respects, including output format (choosing
992 between ELF and ECOFF only), handling of pseudo-opcodes which may generate
993 debugging information or store symbol table information, and default
994 endianness. The available configuration names are: @samp{mipsecoff},
995 @samp{mipself}, @samp{mipslecoff}, @samp{mipsbecoff}, @samp{mipslelf},
996 @samp{mipsbelf}. The first two do not alter the default endianness from that
997 of the primary target for which the assembler was configured; the others change
998 the default to little- or big-endian as indicated by the @samp{b} or @samp{l}
999 in the name. Using @samp{-EB} or @samp{-EL} will override the endianness
1000 selection in any case.
1002 This option is currently supported only when the primary target
1003 @command{@value{AS}} is configured for is a @sc{mips} ELF or ECOFF target.
1004 Furthermore, the primary target or others specified with
1005 @samp{--enable-targets=@dots{}} at configuration time must include support for
1006 the other format, if both are to be available. For example, the Irix 5
1007 configuration includes support for both.
1009 Eventually, this option will support more configurations, with more
1010 fine-grained control over the assembler's behavior, and will be supported for
1014 @command{@value{AS}} ignores this option. It is accepted for compatibility with
1021 Control how to deal with multiplication overflow and division by zero.
1022 @samp{--trap} or @samp{--no-break} (which are synonyms) take a trap exception
1023 (and only work for Instruction Set Architecture level 2 and higher);
1024 @samp{--break} or @samp{--no-trap} (also synonyms, and the default) take a
1028 When this option is used, @command{@value{AS}} will issue a warning every
1029 time it generates a nop instruction from a macro.
1034 The following options are available when @value{AS} is configured for
1040 Enable or disable the JSRI to BSR transformation. By default this is enabled.
1041 The command line option @samp{-nojsri2bsr} can be used to disable it.
1045 Enable or disable the silicon filter behaviour. By default this is disabled.
1046 The default can be overridden by the @samp{-sifilter} command line option.
1049 Alter jump instructions for long displacements.
1051 @item -mcpu=[210|340]
1052 Select the cpu type on the target hardware. This controls which instructions
1056 Assemble for a big endian target.
1059 Assemble for a little endian target.
1065 See the info pages for documentation of the MMIX-specific options.
1069 The following options are available when @value{AS} is configured for
1070 an Xtensa processor.
1073 @item --density | --no-density
1074 Enable or disable use of instructions from the Xtensa code density
1075 option. This is enabled by default when the Xtensa processor supports
1076 the code density option.
1078 @item --relax | --no-relax
1079 Enable or disable instruction relaxation. This is enabled by default.
1080 Note: In the current implementation, these options also control whether
1081 assembler optimizations are performed, making these options equivalent
1082 to @option{--generics} and @option{--no-generics}.
1084 @item --generics | --no-generics
1085 Enable or disable all assembler transformations of Xtensa instructions.
1086 The default is @option{--generics};
1087 @option{--no-generics} should be used only in the rare cases when the
1088 instructions must be exactly as specified in the assembly source.
1090 @item --text-section-literals | --no-text-section-literals
1091 With @option{--text-@-section-@-literals}, literal pools are interspersed
1092 in the text section. The default is
1093 @option{--no-@-text-@-section-@-literals}, which places literals in a
1094 separate section in the output file.
1096 @item --target-align | --no-target-align
1097 Enable or disable automatic alignment to reduce branch penalties at the
1098 expense of some code density. The default is @option{--target-@-align}.
1100 @item --longcalls | --no-longcalls
1101 Enable or disable transformation of call instructions to allow calls
1102 across a greater range of addresses. The default is
1103 @option{--no-@-longcalls}.
1110 * Manual:: Structure of this Manual
1111 * GNU Assembler:: The GNU Assembler
1112 * Object Formats:: Object File Formats
1113 * Command Line:: Command Line
1114 * Input Files:: Input Files
1115 * Object:: Output (Object) File
1116 * Errors:: Error and Warning Messages
1120 @section Structure of this Manual
1122 @cindex manual, structure and purpose
1123 This manual is intended to describe what you need to know to use
1124 @sc{gnu} @command{@value{AS}}. We cover the syntax expected in source files, including
1125 notation for symbols, constants, and expressions; the directives that
1126 @command{@value{AS}} understands; and of course how to invoke @command{@value{AS}}.
1129 We also cover special features in the @value{TARGET}
1130 configuration of @command{@value{AS}}, including assembler directives.
1133 This manual also describes some of the machine-dependent features of
1134 various flavors of the assembler.
1137 @cindex machine instructions (not covered)
1138 On the other hand, this manual is @emph{not} intended as an introduction
1139 to programming in assembly language---let alone programming in general!
1140 In a similar vein, we make no attempt to introduce the machine
1141 architecture; we do @emph{not} describe the instruction set, standard
1142 mnemonics, registers or addressing modes that are standard to a
1143 particular architecture.
1145 You may want to consult the manufacturer's
1146 machine architecture manual for this information.
1150 For information on the H8/300 machine instruction set, see @cite{H8/300
1151 Series Programming Manual}. For the H8/300H, see @cite{H8/300H Series
1152 Programming Manual} (Renesas).
1155 For information on the H8/500 machine instruction set, see @cite{H8/500
1156 Series Programming Manual} (Renesas M21T001).
1159 For information on the Renesas (formerly Hitachi) SH machine instruction set,
1160 see @cite{SH-Microcomputer User's Manual} (Renesas).
1163 For information on the Z8000 machine instruction set, see @cite{Z8000 CPU Technical Manual}
1167 @c I think this is premature---doc@cygnus.com, 17jan1991
1169 Throughout this manual, we assume that you are running @dfn{GNU},
1170 the portable operating system from the @dfn{Free Software
1171 Foundation, Inc.}. This restricts our attention to certain kinds of
1172 computer (in particular, the kinds of computers that @sc{gnu} can run on);
1173 once this assumption is granted examples and definitions need less
1176 @command{@value{AS}} is part of a team of programs that turn a high-level
1177 human-readable series of instructions into a low-level
1178 computer-readable series of instructions. Different versions of
1179 @command{@value{AS}} are used for different kinds of computer.
1182 @c There used to be a section "Terminology" here, which defined
1183 @c "contents", "byte", "word", and "long". Defining "word" to any
1184 @c particular size is confusing when the .word directive may generate 16
1185 @c bits on one machine and 32 bits on another; in general, for the user
1186 @c version of this manual, none of these terms seem essential to define.
1187 @c They were used very little even in the former draft of the manual;
1188 @c this draft makes an effort to avoid them (except in names of
1192 @section The GNU Assembler
1194 @c man begin DESCRIPTION
1196 @sc{gnu} @command{as} is really a family of assemblers.
1198 This manual describes @command{@value{AS}}, a member of that family which is
1199 configured for the @value{TARGET} architectures.
1201 If you use (or have used) the @sc{gnu} assembler on one architecture, you
1202 should find a fairly similar environment when you use it on another
1203 architecture. Each version has much in common with the others,
1204 including object file formats, most assembler directives (often called
1205 @dfn{pseudo-ops}) and assembler syntax.@refill
1207 @cindex purpose of @sc{gnu} assembler
1208 @command{@value{AS}} is primarily intended to assemble the output of the
1209 @sc{gnu} C compiler @code{@value{GCC}} for use by the linker
1210 @code{@value{LD}}. Nevertheless, we've tried to make @command{@value{AS}}
1211 assemble correctly everything that other assemblers for the same
1212 machine would assemble.
1214 Any exceptions are documented explicitly (@pxref{Machine Dependencies}).
1217 @c This remark should appear in generic version of manual; assumption
1218 @c here is that generic version sets M680x0.
1219 This doesn't mean @command{@value{AS}} always uses the same syntax as another
1220 assembler for the same architecture; for example, we know of several
1221 incompatible versions of 680x0 assembly language syntax.
1226 Unlike older assemblers, @command{@value{AS}} is designed to assemble a source
1227 program in one pass of the source file. This has a subtle impact on the
1228 @kbd{.org} directive (@pxref{Org,,@code{.org}}).
1230 @node Object Formats
1231 @section Object File Formats
1233 @cindex object file format
1234 The @sc{gnu} assembler can be configured to produce several alternative
1235 object file formats. For the most part, this does not affect how you
1236 write assembly language programs; but directives for debugging symbols
1237 are typically different in different file formats. @xref{Symbol
1238 Attributes,,Symbol Attributes}.
1241 For the @value{TARGET} target, @command{@value{AS}} is configured to produce
1242 @value{OBJ-NAME} format object files.
1244 @c The following should exhaust all configs that set MULTI-OBJ, ideally
1246 On the @value{TARGET}, @command{@value{AS}} can be configured to produce either
1247 @code{a.out} or COFF format object files.
1250 On the @value{TARGET}, @command{@value{AS}} can be configured to produce either
1251 @code{b.out} or COFF format object files.
1254 On the @value{TARGET}, @command{@value{AS}} can be configured to produce either
1255 SOM or ELF format object files.
1260 @section Command Line
1262 @cindex command line conventions
1264 After the program name @command{@value{AS}}, the command line may contain
1265 options and file names. Options may appear in any order, and may be
1266 before, after, or between file names. The order of file names is
1269 @cindex standard input, as input file
1271 @file{--} (two hyphens) by itself names the standard input file
1272 explicitly, as one of the files for @command{@value{AS}} to assemble.
1274 @cindex options, command line
1275 Except for @samp{--} any command line argument that begins with a
1276 hyphen (@samp{-}) is an option. Each option changes the behavior of
1277 @command{@value{AS}}. No option changes the way another option works. An
1278 option is a @samp{-} followed by one or more letters; the case of
1279 the letter is important. All options are optional.
1281 Some options expect exactly one file name to follow them. The file
1282 name may either immediately follow the option's letter (compatible
1283 with older assemblers) or it may be the next command argument (@sc{gnu}
1284 standard). These two command lines are equivalent:
1287 @value{AS} -o my-object-file.o mumble.s
1288 @value{AS} -omy-object-file.o mumble.s
1292 @section Input Files
1295 @cindex source program
1296 @cindex files, input
1297 We use the phrase @dfn{source program}, abbreviated @dfn{source}, to
1298 describe the program input to one run of @command{@value{AS}}. The program may
1299 be in one or more files; how the source is partitioned into files
1300 doesn't change the meaning of the source.
1302 @c I added "con" prefix to "catenation" just to prove I can overcome my
1303 @c APL training... doc@cygnus.com
1304 The source program is a concatenation of the text in all the files, in the
1307 @c man begin DESCRIPTION
1308 Each time you run @command{@value{AS}} it assembles exactly one source
1309 program. The source program is made up of one or more files.
1310 (The standard input is also a file.)
1312 You give @command{@value{AS}} a command line that has zero or more input file
1313 names. The input files are read (from left file name to right). A
1314 command line argument (in any position) that has no special meaning
1315 is taken to be an input file name.
1317 If you give @command{@value{AS}} no file names it attempts to read one input file
1318 from the @command{@value{AS}} standard input, which is normally your terminal. You
1319 may have to type @key{ctl-D} to tell @command{@value{AS}} there is no more program
1322 Use @samp{--} if you need to explicitly name the standard input file
1323 in your command line.
1325 If the source is empty, @command{@value{AS}} produces a small, empty object
1330 @subheading Filenames and Line-numbers
1332 @cindex input file linenumbers
1333 @cindex line numbers, in input files
1334 There are two ways of locating a line in the input file (or files) and
1335 either may be used in reporting error messages. One way refers to a line
1336 number in a physical file; the other refers to a line number in a
1337 ``logical'' file. @xref{Errors, ,Error and Warning Messages}.
1339 @dfn{Physical files} are those files named in the command line given
1340 to @command{@value{AS}}.
1342 @dfn{Logical files} are simply names declared explicitly by assembler
1343 directives; they bear no relation to physical files. Logical file names help
1344 error messages reflect the original source file, when @command{@value{AS}} source
1345 is itself synthesized from other files. @command{@value{AS}} understands the
1346 @samp{#} directives emitted by the @code{@value{GCC}} preprocessor. See also
1347 @ref{File,,@code{.file}}.
1350 @section Output (Object) File
1356 Every time you run @command{@value{AS}} it produces an output file, which is
1357 your assembly language program translated into numbers. This file
1358 is the object file. Its default name is
1366 @code{b.out} when @command{@value{AS}} is configured for the Intel 80960.
1368 You can give it another name by using the @option{-o} option. Conventionally,
1369 object file names end with @file{.o}. The default name is used for historical
1370 reasons: older assemblers were capable of assembling self-contained programs
1371 directly into a runnable program. (For some formats, this isn't currently
1372 possible, but it can be done for the @code{a.out} format.)
1376 The object file is meant for input to the linker @code{@value{LD}}. It contains
1377 assembled program code, information to help @code{@value{LD}} integrate
1378 the assembled program into a runnable file, and (optionally) symbolic
1379 information for the debugger.
1381 @c link above to some info file(s) like the description of a.out.
1382 @c don't forget to describe @sc{gnu} info as well as Unix lossage.
1385 @section Error and Warning Messages
1387 @c man begin DESCRIPTION
1389 @cindex error messages
1390 @cindex warning messages
1391 @cindex messages from assembler
1392 @command{@value{AS}} may write warnings and error messages to the standard error
1393 file (usually your terminal). This should not happen when a compiler
1394 runs @command{@value{AS}} automatically. Warnings report an assumption made so
1395 that @command{@value{AS}} could keep assembling a flawed program; errors report a
1396 grave problem that stops the assembly.
1400 @cindex format of warning messages
1401 Warning messages have the format
1404 file_name:@b{NNN}:Warning Message Text
1408 @cindex line numbers, in warnings/errors
1409 (where @b{NNN} is a line number). If a logical file name has been given
1410 (@pxref{File,,@code{.file}}) it is used for the filename, otherwise the name of
1411 the current input file is used. If a logical line number was given
1413 (@pxref{Line,,@code{.line}})
1417 (@pxref{Line,,@code{.line}})
1420 (@pxref{Ln,,@code{.ln}})
1423 then it is used to calculate the number printed,
1424 otherwise the actual line in the current source file is printed. The
1425 message text is intended to be self explanatory (in the grand Unix
1428 @cindex format of error messages
1429 Error messages have the format
1431 file_name:@b{NNN}:FATAL:Error Message Text
1433 The file name and line number are derived as for warning
1434 messages. The actual message text may be rather less explanatory
1435 because many of them aren't supposed to happen.
1438 @chapter Command-Line Options
1440 @cindex options, all versions of assembler
1441 This chapter describes command-line options available in @emph{all}
1442 versions of the @sc{gnu} assembler; @pxref{Machine Dependencies}, for options specific
1444 to the @value{TARGET} target.
1447 to particular machine architectures.
1450 @c man begin DESCRIPTION
1452 If you are invoking @command{@value{AS}} via the @sc{gnu} C compiler,
1453 you can use the @samp{-Wa} option to pass arguments through to the assembler.
1454 The assembler arguments must be separated from each other (and the @samp{-Wa})
1455 by commas. For example:
1458 gcc -c -g -O -Wa,-alh,-L file.c
1462 This passes two options to the assembler: @samp{-alh} (emit a listing to
1463 standard output with high-level and assembly source) and @samp{-L} (retain
1464 local symbols in the symbol table).
1466 Usually you do not need to use this @samp{-Wa} mechanism, since many compiler
1467 command-line options are automatically passed to the assembler by the compiler.
1468 (You can call the @sc{gnu} compiler driver with the @samp{-v} option to see
1469 precisely what options it passes to each compilation pass, including the
1475 * a:: -a[cdhlns] enable listings
1476 * D:: -D for compatibility
1477 * f:: -f to work faster
1478 * I:: -I for .include search path
1479 @ifclear DIFF-TBL-KLUGE
1480 * K:: -K for compatibility
1482 @ifset DIFF-TBL-KLUGE
1483 * K:: -K for difference tables
1486 * L:: -L to retain local labels
1487 * listing:: --listing-XXX to configure listing output
1488 * M:: -M or --mri to assemble in MRI compatibility mode
1489 * MD:: --MD for dependency tracking
1490 * o:: -o to name the object file
1491 * R:: -R to join data and text sections
1492 * statistics:: --statistics to see statistics about assembly
1493 * traditional-format:: --traditional-format for compatible output
1494 * v:: -v to announce version
1495 * W:: -W, --no-warn, --warn, --fatal-warnings to control warnings
1496 * Z:: -Z to make object file even after errors
1500 @section Enable Listings: @option{-a[cdhlns]}
1509 @cindex listings, enabling
1510 @cindex assembly listings, enabling
1512 These options enable listing output from the assembler. By itself,
1513 @samp{-a} requests high-level, assembly, and symbols listing.
1514 You can use other letters to select specific options for the list:
1515 @samp{-ah} requests a high-level language listing,
1516 @samp{-al} requests an output-program assembly listing, and
1517 @samp{-as} requests a symbol table listing.
1518 High-level listings require that a compiler debugging option like
1519 @samp{-g} be used, and that assembly listings (@samp{-al}) be requested
1522 Use the @samp{-ac} option to omit false conditionals from a listing. Any lines
1523 which are not assembled because of a false @code{.if} (or @code{.ifdef}, or any
1524 other conditional), or a true @code{.if} followed by an @code{.else}, will be
1525 omitted from the listing.
1527 Use the @samp{-ad} option to omit debugging directives from the
1530 Once you have specified one of these options, you can further control
1531 listing output and its appearance using the directives @code{.list},
1532 @code{.nolist}, @code{.psize}, @code{.eject}, @code{.title}, and
1534 The @samp{-an} option turns off all forms processing.
1535 If you do not request listing output with one of the @samp{-a} options, the
1536 listing-control directives have no effect.
1538 The letters after @samp{-a} may be combined into one option,
1539 @emph{e.g.}, @samp{-aln}.
1541 Note if the assembler source is coming from the standard input (eg because it
1542 is being created by @code{@value{GCC}} and the @samp{-pipe} command line switch
1543 is being used) then the listing will not contain any comments or preprocessor
1544 directives. This is because the listing code buffers input source lines from
1545 stdin only after they have been preprocessed by the assembler. This reduces
1546 memory usage and makes the code more efficient.
1549 @section @option{-D}
1552 This option has no effect whatsoever, but it is accepted to make it more
1553 likely that scripts written for other assemblers also work with
1554 @command{@value{AS}}.
1557 @section Work Faster: @option{-f}
1560 @cindex trusted compiler
1561 @cindex faster processing (@option{-f})
1562 @samp{-f} should only be used when assembling programs written by a
1563 (trusted) compiler. @samp{-f} stops the assembler from doing whitespace
1564 and comment preprocessing on
1565 the input file(s) before assembling them. @xref{Preprocessing,
1569 @emph{Warning:} if you use @samp{-f} when the files actually need to be
1570 preprocessed (if they contain comments, for example), @command{@value{AS}} does
1575 @section @code{.include} Search Path: @option{-I} @var{path}
1577 @kindex -I @var{path}
1578 @cindex paths for @code{.include}
1579 @cindex search path for @code{.include}
1580 @cindex @code{include} directive search path
1581 Use this option to add a @var{path} to the list of directories
1582 @command{@value{AS}} searches for files specified in @code{.include}
1583 directives (@pxref{Include,,@code{.include}}). You may use @option{-I} as
1584 many times as necessary to include a variety of paths. The current
1585 working directory is always searched first; after that, @command{@value{AS}}
1586 searches any @samp{-I} directories in the same order as they were
1587 specified (left to right) on the command line.
1590 @section Difference Tables: @option{-K}
1593 @ifclear DIFF-TBL-KLUGE
1594 On the @value{TARGET} family, this option is allowed, but has no effect. It is
1595 permitted for compatibility with the @sc{gnu} assembler on other platforms,
1596 where it can be used to warn when the assembler alters the machine code
1597 generated for @samp{.word} directives in difference tables. The @value{TARGET}
1598 family does not have the addressing limitations that sometimes lead to this
1599 alteration on other platforms.
1602 @ifset DIFF-TBL-KLUGE
1603 @cindex difference tables, warning
1604 @cindex warning for altered difference tables
1605 @command{@value{AS}} sometimes alters the code emitted for directives of the form
1606 @samp{.word @var{sym1}-@var{sym2}}; @pxref{Word,,@code{.word}}.
1607 You can use the @samp{-K} option if you want a warning issued when this
1612 @section Include Local Labels: @option{-L}
1615 @cindex local labels, retaining in output
1616 Labels beginning with @samp{L} (upper case only) are called @dfn{local
1617 labels}. @xref{Symbol Names}. Normally you do not see such labels when
1618 debugging, because they are intended for the use of programs (like
1619 compilers) that compose assembler programs, not for your notice.
1620 Normally both @command{@value{AS}} and @code{@value{LD}} discard such labels, so you do not
1621 normally debug with them.
1623 This option tells @command{@value{AS}} to retain those @samp{L@dots{}} symbols
1624 in the object file. Usually if you do this you also tell the linker
1625 @code{@value{LD}} to preserve symbols whose names begin with @samp{L}.
1627 By default, a local label is any label beginning with @samp{L}, but each
1628 target is allowed to redefine the local label prefix.
1630 On the HPPA local labels begin with @samp{L$}.
1634 @section Configuring listing output: @option{--listing}
1636 The listing feature of the assembler can be enabled via the command line switch
1637 @samp{-a} (@pxref{a}). This feature combines the input source file(s) with a
1638 hex dump of the corresponding locations in the output object file, and displays
1639 them as a listing file. The format of this listing can be controlled by pseudo
1640 ops inside the assembler source (@pxref{List} @pxref{Title} @pxref{Sbttl}
1641 @pxref{Psize} @pxref{Eject}) and also by the following switches:
1644 @item --listing-lhs-width=@samp{number}
1645 @kindex --listing-lhs-width
1646 @cindex Width of first line disassembly output
1647 Sets the maximum width, in words, of the first line of the hex byte dump. This
1648 dump appears on the left hand side of the listing output.
1650 @item --listing-lhs-width2=@samp{number}
1651 @kindex --listing-lhs-width2
1652 @cindex Width of continuation lines of disassembly output
1653 Sets the maximum width, in words, of any further lines of the hex byte dump for
1654 a given input source line. If this value is not specified, it defaults to being
1655 the same as the value specified for @samp{--listing-lhs-width}. If neither
1656 switch is used the default is to one.
1658 @item --listing-rhs-width=@samp{number}
1659 @kindex --listing-rhs-width
1660 @cindex Width of source line output
1661 Sets the maximum width, in characters, of the source line that is displayed
1662 alongside the hex dump. The default value for this parameter is 100. The
1663 source line is displayed on the right hand side of the listing output.
1665 @item --listing-cont-lines=@samp{number}
1666 @kindex --listing-cont-lines
1667 @cindex Maximum number of continuation lines
1668 Sets the maximum number of continuation lines of hex dump that will be
1669 displayed for a given single line of source input. The default value is 4.
1673 @section Assemble in MRI Compatibility Mode: @option{-M}
1676 @cindex MRI compatibility mode
1677 The @option{-M} or @option{--mri} option selects MRI compatibility mode. This
1678 changes the syntax and pseudo-op handling of @command{@value{AS}} to make it
1679 compatible with the @code{ASM68K} or the @code{ASM960} (depending upon the
1680 configured target) assembler from Microtec Research. The exact nature of the
1681 MRI syntax will not be documented here; see the MRI manuals for more
1682 information. Note in particular that the handling of macros and macro
1683 arguments is somewhat different. The purpose of this option is to permit
1684 assembling existing MRI assembler code using @command{@value{AS}}.
1686 The MRI compatibility is not complete. Certain operations of the MRI assembler
1687 depend upon its object file format, and can not be supported using other object
1688 file formats. Supporting these would require enhancing each object file format
1689 individually. These are:
1692 @item global symbols in common section
1694 The m68k MRI assembler supports common sections which are merged by the linker.
1695 Other object file formats do not support this. @command{@value{AS}} handles
1696 common sections by treating them as a single common symbol. It permits local
1697 symbols to be defined within a common section, but it can not support global
1698 symbols, since it has no way to describe them.
1700 @item complex relocations
1702 The MRI assemblers support relocations against a negated section address, and
1703 relocations which combine the start addresses of two or more sections. These
1704 are not support by other object file formats.
1706 @item @code{END} pseudo-op specifying start address
1708 The MRI @code{END} pseudo-op permits the specification of a start address.
1709 This is not supported by other object file formats. The start address may
1710 instead be specified using the @option{-e} option to the linker, or in a linker
1713 @item @code{IDNT}, @code{.ident} and @code{NAME} pseudo-ops
1715 The MRI @code{IDNT}, @code{.ident} and @code{NAME} pseudo-ops assign a module
1716 name to the output file. This is not supported by other object file formats.
1718 @item @code{ORG} pseudo-op
1720 The m68k MRI @code{ORG} pseudo-op begins an absolute section at a given
1721 address. This differs from the usual @command{@value{AS}} @code{.org} pseudo-op,
1722 which changes the location within the current section. Absolute sections are
1723 not supported by other object file formats. The address of a section may be
1724 assigned within a linker script.
1727 There are some other features of the MRI assembler which are not supported by
1728 @command{@value{AS}}, typically either because they are difficult or because they
1729 seem of little consequence. Some of these may be supported in future releases.
1733 @item EBCDIC strings
1735 EBCDIC strings are not supported.
1737 @item packed binary coded decimal
1739 Packed binary coded decimal is not supported. This means that the @code{DC.P}
1740 and @code{DCB.P} pseudo-ops are not supported.
1742 @item @code{FEQU} pseudo-op
1744 The m68k @code{FEQU} pseudo-op is not supported.
1746 @item @code{NOOBJ} pseudo-op
1748 The m68k @code{NOOBJ} pseudo-op is not supported.
1750 @item @code{OPT} branch control options
1752 The m68k @code{OPT} branch control options---@code{B}, @code{BRS}, @code{BRB},
1753 @code{BRL}, and @code{BRW}---are ignored. @command{@value{AS}} automatically
1754 relaxes all branches, whether forward or backward, to an appropriate size, so
1755 these options serve no purpose.
1757 @item @code{OPT} list control options
1759 The following m68k @code{OPT} list control options are ignored: @code{C},
1760 @code{CEX}, @code{CL}, @code{CRE}, @code{E}, @code{G}, @code{I}, @code{M},
1761 @code{MEX}, @code{MC}, @code{MD}, @code{X}.
1763 @item other @code{OPT} options
1765 The following m68k @code{OPT} options are ignored: @code{NEST}, @code{O},
1766 @code{OLD}, @code{OP}, @code{P}, @code{PCO}, @code{PCR}, @code{PCS}, @code{R}.
1768 @item @code{OPT} @code{D} option is default
1770 The m68k @code{OPT} @code{D} option is the default, unlike the MRI assembler.
1771 @code{OPT NOD} may be used to turn it off.
1773 @item @code{XREF} pseudo-op.
1775 The m68k @code{XREF} pseudo-op is ignored.
1777 @item @code{.debug} pseudo-op
1779 The i960 @code{.debug} pseudo-op is not supported.
1781 @item @code{.extended} pseudo-op
1783 The i960 @code{.extended} pseudo-op is not supported.
1785 @item @code{.list} pseudo-op.
1787 The various options of the i960 @code{.list} pseudo-op are not supported.
1789 @item @code{.optimize} pseudo-op
1791 The i960 @code{.optimize} pseudo-op is not supported.
1793 @item @code{.output} pseudo-op
1795 The i960 @code{.output} pseudo-op is not supported.
1797 @item @code{.setreal} pseudo-op
1799 The i960 @code{.setreal} pseudo-op is not supported.
1804 @section Dependency Tracking: @option{--MD}
1807 @cindex dependency tracking
1810 @command{@value{AS}} can generate a dependency file for the file it creates. This
1811 file consists of a single rule suitable for @code{make} describing the
1812 dependencies of the main source file.
1814 The rule is written to the file named in its argument.
1816 This feature is used in the automatic updating of makefiles.
1819 @section Name the Object File: @option{-o}
1822 @cindex naming object file
1823 @cindex object file name
1824 There is always one object file output when you run @command{@value{AS}}. By
1825 default it has the name
1828 @file{a.out} (or @file{b.out}, for Intel 960 targets only).
1842 You use this option (which takes exactly one filename) to give the
1843 object file a different name.
1845 Whatever the object file is called, @command{@value{AS}} overwrites any
1846 existing file of the same name.
1849 @section Join Data and Text Sections: @option{-R}
1852 @cindex data and text sections, joining
1853 @cindex text and data sections, joining
1854 @cindex joining text and data sections
1855 @cindex merging text and data sections
1856 @option{-R} tells @command{@value{AS}} to write the object file as if all
1857 data-section data lives in the text section. This is only done at
1858 the very last moment: your binary data are the same, but data
1859 section parts are relocated differently. The data section part of
1860 your object file is zero bytes long because all its bytes are
1861 appended to the text section. (@xref{Sections,,Sections and Relocation}.)
1863 When you specify @option{-R} it would be possible to generate shorter
1864 address displacements (because we do not have to cross between text and
1865 data section). We refrain from doing this simply for compatibility with
1866 older versions of @command{@value{AS}}. In future, @option{-R} may work this way.
1869 When @command{@value{AS}} is configured for COFF or ELF output,
1870 this option is only useful if you use sections named @samp{.text} and
1875 @option{-R} is not supported for any of the HPPA targets. Using
1876 @option{-R} generates a warning from @command{@value{AS}}.
1880 @section Display Assembly Statistics: @option{--statistics}
1882 @kindex --statistics
1883 @cindex statistics, about assembly
1884 @cindex time, total for assembly
1885 @cindex space used, maximum for assembly
1886 Use @samp{--statistics} to display two statistics about the resources used by
1887 @command{@value{AS}}: the maximum amount of space allocated during the assembly
1888 (in bytes), and the total execution time taken for the assembly (in @sc{cpu}
1891 @node traditional-format
1892 @section Compatible Output: @option{--traditional-format}
1894 @kindex --traditional-format
1895 For some targets, the output of @command{@value{AS}} is different in some ways
1896 from the output of some existing assembler. This switch requests
1897 @command{@value{AS}} to use the traditional format instead.
1899 For example, it disables the exception frame optimizations which
1900 @command{@value{AS}} normally does by default on @code{@value{GCC}} output.
1903 @section Announce Version: @option{-v}
1907 @cindex assembler version
1908 @cindex version of assembler
1909 You can find out what version of as is running by including the
1910 option @samp{-v} (which you can also spell as @samp{-version}) on the
1914 @section Control Warnings: @option{-W}, @option{--warn}, @option{--no-warn}, @option{--fatal-warnings}
1916 @command{@value{AS}} should never give a warning or error message when
1917 assembling compiler output. But programs written by people often
1918 cause @command{@value{AS}} to give a warning that a particular assumption was
1919 made. All such warnings are directed to the standard error file.
1923 @cindex suppressing warnings
1924 @cindex warnings, suppressing
1925 If you use the @option{-W} and @option{--no-warn} options, no warnings are issued.
1926 This only affects the warning messages: it does not change any particular of
1927 how @command{@value{AS}} assembles your file. Errors, which stop the assembly,
1930 @kindex --fatal-warnings
1931 @cindex errors, caused by warnings
1932 @cindex warnings, causing error
1933 If you use the @option{--fatal-warnings} option, @command{@value{AS}} considers
1934 files that generate warnings to be in error.
1937 @cindex warnings, switching on
1938 You can switch these options off again by specifying @option{--warn}, which
1939 causes warnings to be output as usual.
1942 @section Generate Object File in Spite of Errors: @option{-Z}
1943 @cindex object file, after errors
1944 @cindex errors, continuing after
1945 After an error message, @command{@value{AS}} normally produces no output. If for
1946 some reason you are interested in object file output even after
1947 @command{@value{AS}} gives an error message on your program, use the @samp{-Z}
1948 option. If there are any errors, @command{@value{AS}} continues anyways, and
1949 writes an object file after a final warning message of the form @samp{@var{n}
1950 errors, @var{m} warnings, generating bad object file.}
1955 @cindex machine-independent syntax
1956 @cindex syntax, machine-independent
1957 This chapter describes the machine-independent syntax allowed in a
1958 source file. @command{@value{AS}} syntax is similar to what many other
1959 assemblers use; it is inspired by the BSD 4.2
1964 assembler, except that @command{@value{AS}} does not assemble Vax bit-fields.
1968 * Preprocessing:: Preprocessing
1969 * Whitespace:: Whitespace
1970 * Comments:: Comments
1971 * Symbol Intro:: Symbols
1972 * Statements:: Statements
1973 * Constants:: Constants
1977 @section Preprocessing
1979 @cindex preprocessing
1980 The @command{@value{AS}} internal preprocessor:
1982 @cindex whitespace, removed by preprocessor
1984 adjusts and removes extra whitespace. It leaves one space or tab before
1985 the keywords on a line, and turns any other whitespace on the line into
1988 @cindex comments, removed by preprocessor
1990 removes all comments, replacing them with a single space, or an
1991 appropriate number of newlines.
1993 @cindex constants, converted by preprocessor
1995 converts character constants into the appropriate numeric values.
1998 It does not do macro processing, include file handling, or
1999 anything else you may get from your C compiler's preprocessor. You can
2000 do include file processing with the @code{.include} directive
2001 (@pxref{Include,,@code{.include}}). You can use the @sc{gnu} C compiler driver
2002 to get other ``CPP'' style preprocessing by giving the input file a
2003 @samp{.S} suffix. @xref{Overall Options,, Options Controlling the Kind of
2004 Output, gcc.info, Using GNU CC}.
2006 Excess whitespace, comments, and character constants
2007 cannot be used in the portions of the input text that are not
2010 @cindex turning preprocessing on and off
2011 @cindex preprocessing, turning on and off
2014 If the first line of an input file is @code{#NO_APP} or if you use the
2015 @samp{-f} option, whitespace and comments are not removed from the input file.
2016 Within an input file, you can ask for whitespace and comment removal in
2017 specific portions of the by putting a line that says @code{#APP} before the
2018 text that may contain whitespace or comments, and putting a line that says
2019 @code{#NO_APP} after this text. This feature is mainly intend to support
2020 @code{asm} statements in compilers whose output is otherwise free of comments
2027 @dfn{Whitespace} is one or more blanks or tabs, in any order.
2028 Whitespace is used to separate symbols, and to make programs neater for
2029 people to read. Unless within character constants
2030 (@pxref{Characters,,Character Constants}), any whitespace means the same
2031 as exactly one space.
2037 There are two ways of rendering comments to @command{@value{AS}}. In both
2038 cases the comment is equivalent to one space.
2040 Anything from @samp{/*} through the next @samp{*/} is a comment.
2041 This means you may not nest these comments.
2045 The only way to include a newline ('\n') in a comment
2046 is to use this sort of comment.
2049 /* This sort of comment does not nest. */
2052 @cindex line comment character
2053 Anything from the @dfn{line comment} character to the next newline
2054 is considered a comment and is ignored. The line comment character is
2056 @samp{;} for the AMD 29K family;
2059 @samp{;} on the ARC;
2062 @samp{@@} on the ARM;
2065 @samp{;} for the H8/300 family;
2068 @samp{!} for the H8/500 family;
2071 @samp{;} for the HPPA;
2074 @samp{#} on the i386 and x86-64;
2077 @samp{#} on the i960;
2080 @samp{;} for the PDP-11;
2083 @samp{;} for picoJava;
2086 @samp{;} for Motorola PowerPC;
2089 @samp{!} for the Renesas SH;
2092 @samp{!} on the SPARC;
2095 @samp{#} on the ip2k;
2098 @samp{#} on the m32r;
2101 @samp{|} on the 680x0;
2104 @samp{#} on the 68HC11 and 68HC12;
2107 @samp{;} on the M880x0;
2110 @samp{#} on the Vax;
2113 @samp{!} for the Z8000;
2116 @samp{#} on the V850;
2119 @samp{#} for Xtensa systems;
2121 see @ref{Machine Dependencies}. @refill
2122 @c FIXME What about i860?
2125 On some machines there are two different line comment characters. One
2126 character only begins a comment if it is the first non-whitespace character on
2127 a line, while the other always begins a comment.
2131 The V850 assembler also supports a double dash as starting a comment that
2132 extends to the end of the line.
2138 @cindex lines starting with @code{#}
2139 @cindex logical line numbers
2140 To be compatible with past assemblers, lines that begin with @samp{#} have a
2141 special interpretation. Following the @samp{#} should be an absolute
2142 expression (@pxref{Expressions}): the logical line number of the @emph{next}
2143 line. Then a string (@pxref{Strings,, Strings}) is allowed: if present it is a
2144 new logical file name. The rest of the line, if any, should be whitespace.
2146 If the first non-whitespace characters on the line are not numeric,
2147 the line is ignored. (Just like a comment.)
2150 # This is an ordinary comment.
2151 # 42-6 "new_file_name" # New logical file name
2152 # This is logical line # 36.
2154 This feature is deprecated, and may disappear from future versions
2155 of @command{@value{AS}}.
2160 @cindex characters used in symbols
2161 @ifclear SPECIAL-SYMS
2162 A @dfn{symbol} is one or more characters chosen from the set of all
2163 letters (both upper and lower case), digits and the three characters
2169 A @dfn{symbol} is one or more characters chosen from the set of all
2170 letters (both upper and lower case), digits and the three characters
2171 @samp{._$}. (Save that, on the H8/300 only, you may not use @samp{$} in
2177 On most machines, you can also use @code{$} in symbol names; exceptions
2178 are noted in @ref{Machine Dependencies}.
2180 No symbol may begin with a digit. Case is significant.
2181 There is no length limit: all characters are significant. Symbols are
2182 delimited by characters not in that set, or by the beginning of a file
2183 (since the source program must end with a newline, the end of a file is
2184 not a possible symbol delimiter). @xref{Symbols}.
2185 @cindex length of symbols
2190 @cindex statements, structure of
2191 @cindex line separator character
2192 @cindex statement separator character
2194 @ifclear abnormal-separator
2195 A @dfn{statement} ends at a newline character (@samp{\n}) or at a
2196 semicolon (@samp{;}). The newline or semicolon is considered part of
2197 the preceding statement. Newlines and semicolons within character
2198 constants are an exception: they do not end statements.
2200 @ifset abnormal-separator
2202 A @dfn{statement} ends at a newline character (@samp{\n}) or an ``at''
2203 sign (@samp{@@}). The newline or at sign is considered part of the
2204 preceding statement. Newlines and at signs within character constants
2205 are an exception: they do not end statements.
2208 A @dfn{statement} ends at a newline character (@samp{\n}) or an exclamation
2209 point (@samp{!}). The newline or exclamation point is considered part of the
2210 preceding statement. Newlines and exclamation points within character
2211 constants are an exception: they do not end statements.
2214 A @dfn{statement} ends at a newline character (@samp{\n}); or (for the
2215 H8/300) a dollar sign (@samp{$}); or (for the
2218 (@samp{;}). The newline or separator character is considered part of
2219 the preceding statement. Newlines and separators within character
2220 constants are an exception: they do not end statements.
2225 A @dfn{statement} ends at a newline character (@samp{\n}) or line
2226 separator character. (The line separator is usually @samp{;}, unless
2227 this conflicts with the comment character; @pxref{Machine Dependencies}.) The
2228 newline or separator character is considered part of the preceding
2229 statement. Newlines and separators within character constants are an
2230 exception: they do not end statements.
2233 @cindex newline, required at file end
2234 @cindex EOF, newline must precede
2235 It is an error to end any statement with end-of-file: the last
2236 character of any input file should be a newline.@refill
2238 An empty statement is allowed, and may include whitespace. It is ignored.
2240 @cindex instructions and directives
2241 @cindex directives and instructions
2242 @c "key symbol" is not used elsewhere in the document; seems pedantic to
2243 @c @defn{} it in that case, as was done previously... doc@cygnus.com,
2245 A statement begins with zero or more labels, optionally followed by a
2246 key symbol which determines what kind of statement it is. The key
2247 symbol determines the syntax of the rest of the statement. If the
2248 symbol begins with a dot @samp{.} then the statement is an assembler
2249 directive: typically valid for any computer. If the symbol begins with
2250 a letter the statement is an assembly language @dfn{instruction}: it
2251 assembles into a machine language instruction.
2253 Different versions of @command{@value{AS}} for different computers
2254 recognize different instructions. In fact, the same symbol may
2255 represent a different instruction in a different computer's assembly
2259 @cindex @code{:} (label)
2260 @cindex label (@code{:})
2261 A label is a symbol immediately followed by a colon (@code{:}).
2262 Whitespace before a label or after a colon is permitted, but you may not
2263 have whitespace between a label's symbol and its colon. @xref{Labels}.
2266 For HPPA targets, labels need not be immediately followed by a colon, but
2267 the definition of a label must begin in column zero. This also implies that
2268 only one label may be defined on each line.
2272 label: .directive followed by something
2273 another_label: # This is an empty statement.
2274 instruction operand_1, operand_2, @dots{}
2281 A constant is a number, written so that its value is known by
2282 inspection, without knowing any context. Like this:
2285 .byte 74, 0112, 092, 0x4A, 0X4a, 'J, '\J # All the same value.
2286 .ascii "Ring the bell\7" # A string constant.
2287 .octa 0x123456789abcdef0123456789ABCDEF0 # A bignum.
2288 .float 0f-314159265358979323846264338327\
2289 95028841971.693993751E-40 # - pi, a flonum.
2294 * Characters:: Character Constants
2295 * Numbers:: Number Constants
2299 @subsection Character Constants
2301 @cindex character constants
2302 @cindex constants, character
2303 There are two kinds of character constants. A @dfn{character} stands
2304 for one character in one byte and its value may be used in
2305 numeric expressions. String constants (properly called string
2306 @emph{literals}) are potentially many bytes and their values may not be
2307 used in arithmetic expressions.
2311 * Chars:: Characters
2315 @subsubsection Strings
2317 @cindex string constants
2318 @cindex constants, string
2319 A @dfn{string} is written between double-quotes. It may contain
2320 double-quotes or null characters. The way to get special characters
2321 into a string is to @dfn{escape} these characters: precede them with
2322 a backslash @samp{\} character. For example @samp{\\} represents
2323 one backslash: the first @code{\} is an escape which tells
2324 @command{@value{AS}} to interpret the second character literally as a backslash
2325 (which prevents @command{@value{AS}} from recognizing the second @code{\} as an
2326 escape character). The complete list of escapes follows.
2328 @cindex escape codes, character
2329 @cindex character escape codes
2332 @c Mnemonic for ACKnowledge; for ASCII this is octal code 007.
2334 @cindex @code{\b} (backspace character)
2335 @cindex backspace (@code{\b})
2337 Mnemonic for backspace; for ASCII this is octal code 010.
2340 @c Mnemonic for EOText; for ASCII this is octal code 004.
2342 @cindex @code{\f} (formfeed character)
2343 @cindex formfeed (@code{\f})
2345 Mnemonic for FormFeed; for ASCII this is octal code 014.
2347 @cindex @code{\n} (newline character)
2348 @cindex newline (@code{\n})
2350 Mnemonic for newline; for ASCII this is octal code 012.
2353 @c Mnemonic for prefix; for ASCII this is octal code 033, usually known as @code{escape}.
2355 @cindex @code{\r} (carriage return character)
2356 @cindex carriage return (@code{\r})
2358 Mnemonic for carriage-Return; for ASCII this is octal code 015.
2361 @c Mnemonic for space; for ASCII this is octal code 040. Included for compliance with
2362 @c other assemblers.
2364 @cindex @code{\t} (tab)
2365 @cindex tab (@code{\t})
2367 Mnemonic for horizontal Tab; for ASCII this is octal code 011.
2370 @c Mnemonic for Vertical tab; for ASCII this is octal code 013.
2371 @c @item \x @var{digit} @var{digit} @var{digit}
2372 @c A hexadecimal character code. The numeric code is 3 hexadecimal digits.
2374 @cindex @code{\@var{ddd}} (octal character code)
2375 @cindex octal character code (@code{\@var{ddd}})
2376 @item \ @var{digit} @var{digit} @var{digit}
2377 An octal character code. The numeric code is 3 octal digits.
2378 For compatibility with other Unix systems, 8 and 9 are accepted as digits:
2379 for example, @code{\008} has the value 010, and @code{\009} the value 011.
2381 @cindex @code{\@var{xd...}} (hex character code)
2382 @cindex hex character code (@code{\@var{xd...}})
2383 @item \@code{x} @var{hex-digits...}
2384 A hex character code. All trailing hex digits are combined. Either upper or
2385 lower case @code{x} works.
2387 @cindex @code{\\} (@samp{\} character)
2388 @cindex backslash (@code{\\})
2390 Represents one @samp{\} character.
2393 @c Represents one @samp{'} (accent acute) character.
2394 @c This is needed in single character literals
2395 @c (@xref{Characters,,Character Constants}.) to represent
2398 @cindex @code{\"} (doublequote character)
2399 @cindex doublequote (@code{\"})
2401 Represents one @samp{"} character. Needed in strings to represent
2402 this character, because an unescaped @samp{"} would end the string.
2404 @item \ @var{anything-else}
2405 Any other character when escaped by @kbd{\} gives a warning, but
2406 assembles as if the @samp{\} was not present. The idea is that if
2407 you used an escape sequence you clearly didn't want the literal
2408 interpretation of the following character. However @command{@value{AS}} has no
2409 other interpretation, so @command{@value{AS}} knows it is giving you the wrong
2410 code and warns you of the fact.
2413 Which characters are escapable, and what those escapes represent,
2414 varies widely among assemblers. The current set is what we think
2415 the BSD 4.2 assembler recognizes, and is a subset of what most C
2416 compilers recognize. If you are in doubt, do not use an escape
2420 @subsubsection Characters
2422 @cindex single character constant
2423 @cindex character, single
2424 @cindex constant, single character
2425 A single character may be written as a single quote immediately
2426 followed by that character. The same escapes apply to characters as
2427 to strings. So if you want to write the character backslash, you
2428 must write @kbd{'\\} where the first @code{\} escapes the second
2429 @code{\}. As you can see, the quote is an acute accent, not a
2430 grave accent. A newline
2432 @ifclear abnormal-separator
2433 (or semicolon @samp{;})
2435 @ifset abnormal-separator
2437 (or at sign @samp{@@})
2440 (or dollar sign @samp{$}, for the H8/300; or semicolon @samp{;} for the
2441 Renesas SH or H8/500)
2445 immediately following an acute accent is taken as a literal character
2446 and does not count as the end of a statement. The value of a character
2447 constant in a numeric expression is the machine's byte-wide code for
2448 that character. @command{@value{AS}} assumes your character code is ASCII:
2449 @kbd{'A} means 65, @kbd{'B} means 66, and so on. @refill
2452 @subsection Number Constants
2454 @cindex constants, number
2455 @cindex number constants
2456 @command{@value{AS}} distinguishes three kinds of numbers according to how they
2457 are stored in the target machine. @emph{Integers} are numbers that
2458 would fit into an @code{int} in the C language. @emph{Bignums} are
2459 integers, but they are stored in more than 32 bits. @emph{Flonums}
2460 are floating point numbers, described below.
2463 * Integers:: Integers
2468 * Bit Fields:: Bit Fields
2474 @subsubsection Integers
2476 @cindex constants, integer
2478 @cindex binary integers
2479 @cindex integers, binary
2480 A binary integer is @samp{0b} or @samp{0B} followed by zero or more of
2481 the binary digits @samp{01}.
2483 @cindex octal integers
2484 @cindex integers, octal
2485 An octal integer is @samp{0} followed by zero or more of the octal
2486 digits (@samp{01234567}).
2488 @cindex decimal integers
2489 @cindex integers, decimal
2490 A decimal integer starts with a non-zero digit followed by zero or
2491 more digits (@samp{0123456789}).
2493 @cindex hexadecimal integers
2494 @cindex integers, hexadecimal
2495 A hexadecimal integer is @samp{0x} or @samp{0X} followed by one or
2496 more hexadecimal digits chosen from @samp{0123456789abcdefABCDEF}.
2498 Integers have the usual values. To denote a negative integer, use
2499 the prefix operator @samp{-} discussed under expressions
2500 (@pxref{Prefix Ops,,Prefix Operators}).
2503 @subsubsection Bignums
2506 @cindex constants, bignum
2507 A @dfn{bignum} has the same syntax and semantics as an integer
2508 except that the number (or its negative) takes more than 32 bits to
2509 represent in binary. The distinction is made because in some places
2510 integers are permitted while bignums are not.
2513 @subsubsection Flonums
2515 @cindex floating point numbers
2516 @cindex constants, floating point
2518 @cindex precision, floating point
2519 A @dfn{flonum} represents a floating point number. The translation is
2520 indirect: a decimal floating point number from the text is converted by
2521 @command{@value{AS}} to a generic binary floating point number of more than
2522 sufficient precision. This generic floating point number is converted
2523 to a particular computer's floating point format (or formats) by a
2524 portion of @command{@value{AS}} specialized to that computer.
2526 A flonum is written by writing (in order)
2531 (@samp{0} is optional on the HPPA.)
2535 A letter, to tell @command{@value{AS}} the rest of the number is a flonum.
2537 @kbd{e} is recommended. Case is not important.
2539 @c FIXME: verify if flonum syntax really this vague for most cases
2540 (Any otherwise illegal letter works here, but that might be changed. Vax BSD
2541 4.2 assembler seems to allow any of @samp{defghDEFGH}.)
2544 On the H8/300, H8/500,
2546 and AMD 29K architectures, the letter must be
2547 one of the letters @samp{DFPRSX} (in upper or lower case).
2549 On the ARC, the letter must be one of the letters @samp{DFRS}
2550 (in upper or lower case).
2552 On the Intel 960 architecture, the letter must be
2553 one of the letters @samp{DFT} (in upper or lower case).
2555 On the HPPA architecture, the letter must be @samp{E} (upper case only).
2559 One of the letters @samp{DFPRSX} (in upper or lower case).
2562 One of the letters @samp{DFRS} (in upper or lower case).
2565 One of the letters @samp{DFPRSX} (in upper or lower case).
2568 The letter @samp{E} (upper case only).
2571 One of the letters @samp{DFT} (in upper or lower case).
2576 An optional sign: either @samp{+} or @samp{-}.
2579 An optional @dfn{integer part}: zero or more decimal digits.
2582 An optional @dfn{fractional part}: @samp{.} followed by zero
2583 or more decimal digits.
2586 An optional exponent, consisting of:
2590 An @samp{E} or @samp{e}.
2591 @c I can't find a config where "EXP_CHARS" is other than 'eE', but in
2592 @c principle this can perfectly well be different on different targets.
2594 Optional sign: either @samp{+} or @samp{-}.
2596 One or more decimal digits.
2601 At least one of the integer part or the fractional part must be
2602 present. The floating point number has the usual base-10 value.
2604 @command{@value{AS}} does all processing using integers. Flonums are computed
2605 independently of any floating point hardware in the computer running
2606 @command{@value{AS}}.
2610 @c Bit fields are written as a general facility but are also controlled
2611 @c by a conditional-compilation flag---which is as of now (21mar91)
2612 @c turned on only by the i960 config of GAS.
2614 @subsubsection Bit Fields
2617 @cindex constants, bit field
2618 You can also define numeric constants as @dfn{bit fields}.
2619 specify two numbers separated by a colon---
2621 @var{mask}:@var{value}
2624 @command{@value{AS}} applies a bitwise @sc{and} between @var{mask} and
2627 The resulting number is then packed
2629 @c this conditional paren in case bit fields turned on elsewhere than 960
2630 (in host-dependent byte order)
2632 into a field whose width depends on which assembler directive has the
2633 bit-field as its argument. Overflow (a result from the bitwise and
2634 requiring more binary digits to represent) is not an error; instead,
2635 more constants are generated, of the specified width, beginning with the
2636 least significant digits.@refill
2638 The directives @code{.byte}, @code{.hword}, @code{.int}, @code{.long},
2639 @code{.short}, and @code{.word} accept bit-field arguments.
2644 @chapter Sections and Relocation
2649 * Secs Background:: Background
2650 * Ld Sections:: Linker Sections
2651 * As Sections:: Assembler Internal Sections
2652 * Sub-Sections:: Sub-Sections
2656 @node Secs Background
2659 Roughly, a section is a range of addresses, with no gaps; all data
2660 ``in'' those addresses is treated the same for some particular purpose.
2661 For example there may be a ``read only'' section.
2663 @cindex linker, and assembler
2664 @cindex assembler, and linker
2665 The linker @code{@value{LD}} reads many object files (partial programs) and
2666 combines their contents to form a runnable program. When @command{@value{AS}}
2667 emits an object file, the partial program is assumed to start at address 0.
2668 @code{@value{LD}} assigns the final addresses for the partial program, so that
2669 different partial programs do not overlap. This is actually an
2670 oversimplification, but it suffices to explain how @command{@value{AS}} uses
2673 @code{@value{LD}} moves blocks of bytes of your program to their run-time
2674 addresses. These blocks slide to their run-time addresses as rigid
2675 units; their length does not change and neither does the order of bytes
2676 within them. Such a rigid unit is called a @emph{section}. Assigning
2677 run-time addresses to sections is called @dfn{relocation}. It includes
2678 the task of adjusting mentions of object-file addresses so they refer to
2679 the proper run-time addresses.
2681 For the H8/300 and H8/500,
2682 and for the Renesas SH,
2683 @command{@value{AS}} pads sections if needed to
2684 ensure they end on a word (sixteen bit) boundary.
2687 @cindex standard assembler sections
2688 An object file written by @command{@value{AS}} has at least three sections, any
2689 of which may be empty. These are named @dfn{text}, @dfn{data} and
2694 When it generates COFF or ELF output,
2696 @command{@value{AS}} can also generate whatever other named sections you specify
2697 using the @samp{.section} directive (@pxref{Section,,@code{.section}}).
2698 If you do not use any directives that place output in the @samp{.text}
2699 or @samp{.data} sections, these sections still exist, but are empty.
2704 When @command{@value{AS}} generates SOM or ELF output for the HPPA,
2706 @command{@value{AS}} can also generate whatever other named sections you
2707 specify using the @samp{.space} and @samp{.subspace} directives. See
2708 @cite{HP9000 Series 800 Assembly Language Reference Manual}
2709 (HP 92432-90001) for details on the @samp{.space} and @samp{.subspace}
2710 assembler directives.
2713 Additionally, @command{@value{AS}} uses different names for the standard
2714 text, data, and bss sections when generating SOM output. Program text
2715 is placed into the @samp{$CODE$} section, data into @samp{$DATA$}, and
2716 BSS into @samp{$BSS$}.
2720 Within the object file, the text section starts at address @code{0}, the
2721 data section follows, and the bss section follows the data section.
2724 When generating either SOM or ELF output files on the HPPA, the text
2725 section starts at address @code{0}, the data section at address
2726 @code{0x4000000}, and the bss section follows the data section.
2729 To let @code{@value{LD}} know which data changes when the sections are
2730 relocated, and how to change that data, @command{@value{AS}} also writes to the
2731 object file details of the relocation needed. To perform relocation
2732 @code{@value{LD}} must know, each time an address in the object
2736 Where in the object file is the beginning of this reference to
2739 How long (in bytes) is this reference?
2741 Which section does the address refer to? What is the numeric value of
2743 (@var{address}) @minus{} (@var{start-address of section})?
2746 Is the reference to an address ``Program-Counter relative''?
2749 @cindex addresses, format of
2750 @cindex section-relative addressing
2751 In fact, every address @command{@value{AS}} ever uses is expressed as
2753 (@var{section}) + (@var{offset into section})
2756 Further, most expressions @command{@value{AS}} computes have this section-relative
2759 (For some object formats, such as SOM for the HPPA, some expressions are
2760 symbol-relative instead.)
2763 In this manual we use the notation @{@var{secname} @var{N}@} to mean ``offset
2764 @var{N} into section @var{secname}.''
2766 Apart from text, data and bss sections you need to know about the
2767 @dfn{absolute} section. When @code{@value{LD}} mixes partial programs,
2768 addresses in the absolute section remain unchanged. For example, address
2769 @code{@{absolute 0@}} is ``relocated'' to run-time address 0 by
2770 @code{@value{LD}}. Although the linker never arranges two partial programs'
2771 data sections with overlapping addresses after linking, @emph{by definition}
2772 their absolute sections must overlap. Address @code{@{absolute@ 239@}} in one
2773 part of a program is always the same address when the program is running as
2774 address @code{@{absolute@ 239@}} in any other part of the program.
2776 The idea of sections is extended to the @dfn{undefined} section. Any
2777 address whose section is unknown at assembly time is by definition
2778 rendered @{undefined @var{U}@}---where @var{U} is filled in later.
2779 Since numbers are always defined, the only way to generate an undefined
2780 address is to mention an undefined symbol. A reference to a named
2781 common block would be such a symbol: its value is unknown at assembly
2782 time so it has section @emph{undefined}.
2784 By analogy the word @emph{section} is used to describe groups of sections in
2785 the linked program. @code{@value{LD}} puts all partial programs' text
2786 sections in contiguous addresses in the linked program. It is
2787 customary to refer to the @emph{text section} of a program, meaning all
2788 the addresses of all partial programs' text sections. Likewise for
2789 data and bss sections.
2791 Some sections are manipulated by @code{@value{LD}}; others are invented for
2792 use of @command{@value{AS}} and have no meaning except during assembly.
2795 @section Linker Sections
2796 @code{@value{LD}} deals with just four kinds of sections, summarized below.
2801 @cindex named sections
2802 @cindex sections, named
2803 @item named sections
2806 @cindex text section
2807 @cindex data section
2811 These sections hold your program. @command{@value{AS}} and @code{@value{LD}} treat them as
2812 separate but equal sections. Anything you can say of one section is
2815 When the program is running, however, it is
2816 customary for the text section to be unalterable. The
2817 text section is often shared among processes: it contains
2818 instructions, constants and the like. The data section of a running
2819 program is usually alterable: for example, C variables would be stored
2820 in the data section.
2825 This section contains zeroed bytes when your program begins running. It
2826 is used to hold uninitialized variables or common storage. The length of
2827 each partial program's bss section is important, but because it starts
2828 out containing zeroed bytes there is no need to store explicit zero
2829 bytes in the object file. The bss section was invented to eliminate
2830 those explicit zeros from object files.
2832 @cindex absolute section
2833 @item absolute section
2834 Address 0 of this section is always ``relocated'' to runtime address 0.
2835 This is useful if you want to refer to an address that @code{@value{LD}} must
2836 not change when relocating. In this sense we speak of absolute
2837 addresses being ``unrelocatable'': they do not change during relocation.
2839 @cindex undefined section
2840 @item undefined section
2841 This ``section'' is a catch-all for address references to objects not in
2842 the preceding sections.
2843 @c FIXME: ref to some other doc on obj-file formats could go here.
2846 @cindex relocation example
2847 An idealized example of three relocatable sections follows.
2849 The example uses the traditional section names @samp{.text} and @samp{.data}.
2851 Memory addresses are on the horizontal axis.
2855 @c END TEXI2ROFF-KILL
2858 partial program # 1: |ttttt|dddd|00|
2865 partial program # 2: |TTT|DDD|000|
2868 +--+---+-----+--+----+---+-----+~~
2869 linked program: | |TTT|ttttt| |dddd|DDD|00000|
2870 +--+---+-----+--+----+---+-----+~~
2872 addresses: 0 @dots{}
2879 \line{\it Partial program \#1: \hfil}
2880 \line{\ibox{2.5cm}{\tt text}\ibox{2cm}{\tt data}\ibox{1cm}{\tt bss}\hfil}
2881 \line{\boxit{2.5cm}{\tt ttttt}\boxit{2cm}{\tt dddd}\boxit{1cm}{\tt 00}\hfil}
2883 \line{\it Partial program \#2: \hfil}
2884 \line{\ibox{1cm}{\tt text}\ibox{1.5cm}{\tt data}\ibox{1cm}{\tt bss}\hfil}
2885 \line{\boxit{1cm}{\tt TTT}\boxit{1.5cm}{\tt DDDD}\boxit{1cm}{\tt 000}\hfil}
2887 \line{\it linked program: \hfil}
2888 \line{\ibox{.5cm}{}\ibox{1cm}{\tt text}\ibox{2.5cm}{}\ibox{.75cm}{}\ibox{2cm}{\tt data}\ibox{1.5cm}{}\ibox{2cm}{\tt bss}\hfil}
2889 \line{\boxit{.5cm}{}\boxit{1cm}{\tt TTT}\boxit{2.5cm}{\tt
2890 ttttt}\boxit{.75cm}{}\boxit{2cm}{\tt dddd}\boxit{1.5cm}{\tt
2891 DDDD}\boxit{2cm}{\tt 00000}\ \dots\hfil}
2893 \line{\it addresses: \hfil}
2897 @c END TEXI2ROFF-KILL
2900 @section Assembler Internal Sections
2902 @cindex internal assembler sections
2903 @cindex sections in messages, internal
2904 These sections are meant only for the internal use of @command{@value{AS}}. They
2905 have no meaning at run-time. You do not really need to know about these
2906 sections for most purposes; but they can be mentioned in @command{@value{AS}}
2907 warning messages, so it might be helpful to have an idea of their
2908 meanings to @command{@value{AS}}. These sections are used to permit the
2909 value of every expression in your assembly language program to be a
2910 section-relative address.
2913 @cindex assembler internal logic error
2914 @item ASSEMBLER-INTERNAL-LOGIC-ERROR!
2915 An internal assembler logic error has been found. This means there is a
2916 bug in the assembler.
2918 @cindex expr (internal section)
2920 The assembler stores complex expression internally as combinations of
2921 symbols. When it needs to represent an expression as a symbol, it puts
2922 it in the expr section.
2924 @c FIXME item transfer[t] vector preload
2925 @c FIXME item transfer[t] vector postload
2926 @c FIXME item register
2930 @section Sub-Sections
2932 @cindex numbered subsections
2933 @cindex grouping data
2939 fall into two sections: text and data.
2941 You may have separate groups of
2943 data in named sections
2947 data in named sections
2953 that you want to end up near to each other in the object file, even though they
2954 are not contiguous in the assembler source. @command{@value{AS}} allows you to
2955 use @dfn{subsections} for this purpose. Within each section, there can be
2956 numbered subsections with values from 0 to 8192. Objects assembled into the
2957 same subsection go into the object file together with other objects in the same
2958 subsection. For example, a compiler might want to store constants in the text
2959 section, but might not want to have them interspersed with the program being
2960 assembled. In this case, the compiler could issue a @samp{.text 0} before each
2961 section of code being output, and a @samp{.text 1} before each group of
2962 constants being output.
2964 Subsections are optional. If you do not use subsections, everything
2965 goes in subsection number zero.
2968 Each subsection is zero-padded up to a multiple of four bytes.
2969 (Subsections may be padded a different amount on different flavors
2970 of @command{@value{AS}}.)
2974 On the H8/300 and H8/500 platforms, each subsection is zero-padded to a word
2975 boundary (two bytes).
2976 The same is true on the Renesas SH.
2979 @c FIXME section padding (alignment)?
2980 @c Rich Pixley says padding here depends on target obj code format; that
2981 @c doesn't seem particularly useful to say without further elaboration,
2982 @c so for now I say nothing about it. If this is a generic BFD issue,
2983 @c these paragraphs might need to vanish from this manual, and be
2984 @c discussed in BFD chapter of binutils (or some such).
2987 On the AMD 29K family, no particular padding is added to section or
2988 subsection sizes; @value{AS} forces no alignment on this platform.
2992 Subsections appear in your object file in numeric order, lowest numbered
2993 to highest. (All this to be compatible with other people's assemblers.)
2994 The object file contains no representation of subsections; @code{@value{LD}} and
2995 other programs that manipulate object files see no trace of them.
2996 They just see all your text subsections as a text section, and all your
2997 data subsections as a data section.
2999 To specify which subsection you want subsequent statements assembled
3000 into, use a numeric argument to specify it, in a @samp{.text
3001 @var{expression}} or a @samp{.data @var{expression}} statement.
3004 When generating COFF or ELF output, you
3009 can also use an extra subsection
3010 argument with arbitrary named sections: @samp{.section @var{name},
3013 @var{Expression} should be an absolute expression.
3014 (@xref{Expressions}.) If you just say @samp{.text} then @samp{.text 0}
3015 is assumed. Likewise @samp{.data} means @samp{.data 0}. Assembly
3016 begins in @code{text 0}. For instance:
3018 .text 0 # The default subsection is text 0 anyway.
3019 .ascii "This lives in the first text subsection. *"
3021 .ascii "But this lives in the second text subsection."
3023 .ascii "This lives in the data section,"
3024 .ascii "in the first data subsection."
3026 .ascii "This lives in the first text section,"
3027 .ascii "immediately following the asterisk (*)."
3030 Each section has a @dfn{location counter} incremented by one for every byte
3031 assembled into that section. Because subsections are merely a convenience
3032 restricted to @command{@value{AS}} there is no concept of a subsection location
3033 counter. There is no way to directly manipulate a location counter---but the
3034 @code{.align} directive changes it, and any label definition captures its
3035 current value. The location counter of the section where statements are being
3036 assembled is said to be the @dfn{active} location counter.
3039 @section bss Section
3042 @cindex common variable storage
3043 The bss section is used for local common variable storage.
3044 You may allocate address space in the bss section, but you may
3045 not dictate data to load into it before your program executes. When
3046 your program starts running, all the contents of the bss
3047 section are zeroed bytes.
3049 The @code{.lcomm} pseudo-op defines a symbol in the bss section; see
3050 @ref{Lcomm,,@code{.lcomm}}.
3052 The @code{.comm} pseudo-op may be used to declare a common symbol, which is
3053 another form of uninitialized symbol; see @xref{Comm,,@code{.comm}}.
3056 When assembling for a target which supports multiple sections, such as ELF or
3057 COFF, you may switch into the @code{.bss} section and define symbols as usual;
3058 see @ref{Section,,@code{.section}}. You may only assemble zero values into the
3059 section. Typically the section will only contain symbol definitions and
3060 @code{.skip} directives (@pxref{Skip,,@code{.skip}}).
3067 Symbols are a central concept: the programmer uses symbols to name
3068 things, the linker uses symbols to link, and the debugger uses symbols
3072 @cindex debuggers, and symbol order
3073 @emph{Warning:} @command{@value{AS}} does not place symbols in the object file in
3074 the same order they were declared. This may break some debuggers.
3079 * Setting Symbols:: Giving Symbols Other Values
3080 * Symbol Names:: Symbol Names
3081 * Dot:: The Special Dot Symbol
3082 * Symbol Attributes:: Symbol Attributes
3089 A @dfn{label} is written as a symbol immediately followed by a colon
3090 @samp{:}. The symbol then represents the current value of the
3091 active location counter, and is, for example, a suitable instruction
3092 operand. You are warned if you use the same symbol to represent two
3093 different locations: the first definition overrides any other
3097 On the HPPA, the usual form for a label need not be immediately followed by a
3098 colon, but instead must start in column zero. Only one label may be defined on
3099 a single line. To work around this, the HPPA version of @command{@value{AS}} also
3100 provides a special directive @code{.label} for defining labels more flexibly.
3103 @node Setting Symbols
3104 @section Giving Symbols Other Values
3106 @cindex assigning values to symbols
3107 @cindex symbol values, assigning
3108 A symbol can be given an arbitrary value by writing a symbol, followed
3109 by an equals sign @samp{=}, followed by an expression
3110 (@pxref{Expressions}). This is equivalent to using the @code{.set}
3111 directive. @xref{Set,,@code{.set}}.
3114 @section Symbol Names
3116 @cindex symbol names
3117 @cindex names, symbol
3118 @ifclear SPECIAL-SYMS
3119 Symbol names begin with a letter or with one of @samp{._}. On most
3120 machines, you can also use @code{$} in symbol names; exceptions are
3121 noted in @ref{Machine Dependencies}. That character may be followed by any
3122 string of digits, letters, dollar signs (unless otherwise noted in
3123 @ref{Machine Dependencies}), and underscores.
3126 For the AMD 29K family, @samp{?} is also allowed in the
3127 body of a symbol name, though not at its beginning.
3132 Symbol names begin with a letter or with one of @samp{._}. On the
3133 Renesas SH or the H8/500, you can also use @code{$} in symbol names. That
3134 character may be followed by any string of digits, letters, dollar signs (save
3135 on the H8/300), and underscores.
3139 Case of letters is significant: @code{foo} is a different symbol name
3142 Each symbol has exactly one name. Each name in an assembly language program
3143 refers to exactly one symbol. You may use that symbol name any number of times
3146 @subheading Local Symbol Names
3148 @cindex local symbol names
3149 @cindex symbol names, local
3150 @cindex temporary symbol names
3151 @cindex symbol names, temporary
3152 Local symbols help compilers and programmers use names temporarily.
3153 They create symbols which are guaranteed to be unique over the entire scope of
3154 the input source code and which can be referred to by a simple notation.
3155 To define a local symbol, write a label of the form @samp{@b{N}:} (where @b{N}
3156 represents any positive integer). To refer to the most recent previous
3157 definition of that symbol write @samp{@b{N}b}, using the same number as when
3158 you defined the label. To refer to the next definition of a local label, write
3159 @samp{@b{N}f}--- The @samp{b} stands for``backwards'' and the @samp{f} stands
3162 There is no restriction on how you can use these labels, and you can reuse them
3163 too. So that it is possible to repeatedly define the same local label (using
3164 the same number @samp{@b{N}}), although you can only refer to the most recently
3165 defined local label of that number (for a backwards reference) or the next
3166 definition of a specific local label for a forward reference. It is also worth
3167 noting that the first 10 local labels (@samp{@b{0:}}@dots{}@samp{@b{9:}}) are
3168 implemented in a slightly more efficient manner than the others.
3179 Which is the equivalent of:
3182 label_1: branch label_3
3183 label_2: branch label_1
3184 label_3: branch label_4
3185 label_4: branch label_3
3188 Local symbol names are only a notational device. They are immediately
3189 transformed into more conventional symbol names before the assembler uses them.
3190 The symbol names stored in the symbol table, appearing in error messages and
3191 optionally emitted to the object file. The names are constructed using these
3196 All local labels begin with @samp{L}. Normally both @command{@value{AS}} and
3197 @code{@value{LD}} forget symbols that start with @samp{L}. These labels are
3198 used for symbols you are never intended to see. If you use the
3199 @samp{-L} option then @command{@value{AS}} retains these symbols in the
3200 object file. If you also instruct @code{@value{LD}} to retain these symbols,
3201 you may use them in debugging.
3204 This is the number that was used in the local label definition. So if the
3205 label is written @samp{55:} then the number is @samp{55}.
3208 This unusual character is included so you do not accidentally invent a symbol
3209 of the same name. The character has ASCII value of @samp{\002} (control-B).
3211 @item @emph{ordinal number}
3212 This is a serial number to keep the labels distinct. The first definition of
3213 @samp{0:} gets the number @samp{1}. The 15th definition of @samp{0:} gets the
3214 number @samp{15}, and so on. Likewise the first definition of @samp{1:} gets
3215 the number @samp{1} and its 15th defintion gets @samp{15} as well.
3218 So for example, the first @code{1:} is named @code{L1@kbd{C-B}1}, the 44th
3219 @code{3:} is named @code{L3@kbd{C-B}44}.
3221 @subheading Dollar Local Labels
3222 @cindex dollar local symbols
3224 @code{@value{AS}} also supports an even more local form of local labels called
3225 dollar labels. These labels go out of scope (ie they become undefined) as soon
3226 as a non-local label is defined. Thus they remain valid for only a small
3227 region of the input source code. Normal local labels, by contrast, remain in
3228 scope for the entire file, or until they are redefined by another occurrence of
3229 the same local label.
3231 Dollar labels are defined in exactly the same way as ordinary local labels,
3232 except that instead of being terminated by a colon, they are terminated by a
3233 dollar sign. eg @samp{@b{55$}}.
3235 They can also be distinguished from ordinary local labels by their transformed
3236 name which uses ASCII character @samp{\001} (control-A) as the magic character
3237 to distinguish them from ordinary labels. Thus the 5th defintion of @samp{6$}
3238 is named @samp{L6@kbd{C-A}5}.
3241 @section The Special Dot Symbol
3243 @cindex dot (symbol)
3244 @cindex @code{.} (symbol)
3245 @cindex current address
3246 @cindex location counter
3247 The special symbol @samp{.} refers to the current address that
3248 @command{@value{AS}} is assembling into. Thus, the expression @samp{melvin:
3249 .long .} defines @code{melvin} to contain its own address.
3250 Assigning a value to @code{.} is treated the same as a @code{.org}
3251 directive. Thus, the expression @samp{.=.+4} is the same as saying
3252 @ifclear no-space-dir
3261 @node Symbol Attributes
3262 @section Symbol Attributes
3264 @cindex symbol attributes
3265 @cindex attributes, symbol
3266 Every symbol has, as well as its name, the attributes ``Value'' and
3267 ``Type''. Depending on output format, symbols can also have auxiliary
3270 The detailed definitions are in @file{a.out.h}.
3273 If you use a symbol without defining it, @command{@value{AS}} assumes zero for
3274 all these attributes, and probably won't warn you. This makes the
3275 symbol an externally defined symbol, which is generally what you
3279 * Symbol Value:: Value
3280 * Symbol Type:: Type
3283 * a.out Symbols:: Symbol Attributes: @code{a.out}
3287 * a.out Symbols:: Symbol Attributes: @code{a.out}
3290 * a.out Symbols:: Symbol Attributes: @code{a.out}, @code{b.out}
3295 * COFF Symbols:: Symbol Attributes for COFF
3298 * SOM Symbols:: Symbol Attributes for SOM
3305 @cindex value of a symbol
3306 @cindex symbol value
3307 The value of a symbol is (usually) 32 bits. For a symbol which labels a
3308 location in the text, data, bss or absolute sections the value is the
3309 number of addresses from the start of that section to the label.
3310 Naturally for text, data and bss sections the value of a symbol changes
3311 as @code{@value{LD}} changes section base addresses during linking. Absolute
3312 symbols' values do not change during linking: that is why they are
3315 The value of an undefined symbol is treated in a special way. If it is
3316 0 then the symbol is not defined in this assembler source file, and
3317 @code{@value{LD}} tries to determine its value from other files linked into the
3318 same program. You make this kind of symbol simply by mentioning a symbol
3319 name without defining it. A non-zero value represents a @code{.comm}
3320 common declaration. The value is how much common storage to reserve, in
3321 bytes (addresses). The symbol refers to the first address of the
3327 @cindex type of a symbol
3329 The type attribute of a symbol contains relocation (section)
3330 information, any flag settings indicating that a symbol is external, and
3331 (optionally), other information for linkers and debuggers. The exact
3332 format depends on the object-code output format in use.
3337 @c The following avoids a "widow" subsection title. @group would be
3338 @c better if it were available outside examples.
3341 @subsection Symbol Attributes: @code{a.out}, @code{b.out}
3343 @cindex @code{b.out} symbol attributes
3344 @cindex symbol attributes, @code{b.out}
3345 These symbol attributes appear only when @command{@value{AS}} is configured for
3346 one of the Berkeley-descended object output formats---@code{a.out} or
3352 @subsection Symbol Attributes: @code{a.out}
3354 @cindex @code{a.out} symbol attributes
3355 @cindex symbol attributes, @code{a.out}
3361 @subsection Symbol Attributes: @code{a.out}
3363 @cindex @code{a.out} symbol attributes
3364 @cindex symbol attributes, @code{a.out}
3368 * Symbol Desc:: Descriptor
3369 * Symbol Other:: Other
3373 @subsubsection Descriptor
3375 @cindex descriptor, of @code{a.out} symbol
3376 This is an arbitrary 16-bit value. You may establish a symbol's
3377 descriptor value by using a @code{.desc} statement
3378 (@pxref{Desc,,@code{.desc}}). A descriptor value means nothing to
3379 @command{@value{AS}}.
3382 @subsubsection Other
3384 @cindex other attribute, of @code{a.out} symbol
3385 This is an arbitrary 8-bit value. It means nothing to @command{@value{AS}}.
3390 @subsection Symbol Attributes for COFF
3392 @cindex COFF symbol attributes
3393 @cindex symbol attributes, COFF
3395 The COFF format supports a multitude of auxiliary symbol attributes;
3396 like the primary symbol attributes, they are set between @code{.def} and
3397 @code{.endef} directives.
3399 @subsubsection Primary Attributes
3401 @cindex primary attributes, COFF symbols
3402 The symbol name is set with @code{.def}; the value and type,
3403 respectively, with @code{.val} and @code{.type}.
3405 @subsubsection Auxiliary Attributes
3407 @cindex auxiliary attributes, COFF symbols
3408 The @command{@value{AS}} directives @code{.dim}, @code{.line}, @code{.scl},
3409 @code{.size}, and @code{.tag} can generate auxiliary symbol table
3410 information for COFF.
3415 @subsection Symbol Attributes for SOM
3417 @cindex SOM symbol attributes
3418 @cindex symbol attributes, SOM
3420 The SOM format for the HPPA supports a multitude of symbol attributes set with
3421 the @code{.EXPORT} and @code{.IMPORT} directives.
3423 The attributes are described in @cite{HP9000 Series 800 Assembly
3424 Language Reference Manual} (HP 92432-90001) under the @code{IMPORT} and
3425 @code{EXPORT} assembler directive documentation.
3429 @chapter Expressions
3433 @cindex numeric values
3434 An @dfn{expression} specifies an address or numeric value.
3435 Whitespace may precede and/or follow an expression.
3437 The result of an expression must be an absolute number, or else an offset into
3438 a particular section. If an expression is not absolute, and there is not
3439 enough information when @command{@value{AS}} sees the expression to know its
3440 section, a second pass over the source program might be necessary to interpret
3441 the expression---but the second pass is currently not implemented.
3442 @command{@value{AS}} aborts with an error message in this situation.
3445 * Empty Exprs:: Empty Expressions
3446 * Integer Exprs:: Integer Expressions
3450 @section Empty Expressions
3452 @cindex empty expressions
3453 @cindex expressions, empty
3454 An empty expression has no value: it is just whitespace or null.
3455 Wherever an absolute expression is required, you may omit the
3456 expression, and @command{@value{AS}} assumes a value of (absolute) 0. This
3457 is compatible with other assemblers.
3460 @section Integer Expressions
3462 @cindex integer expressions
3463 @cindex expressions, integer
3464 An @dfn{integer expression} is one or more @emph{arguments} delimited
3465 by @emph{operators}.
3468 * Arguments:: Arguments
3469 * Operators:: Operators
3470 * Prefix Ops:: Prefix Operators
3471 * Infix Ops:: Infix Operators
3475 @subsection Arguments
3477 @cindex expression arguments
3478 @cindex arguments in expressions
3479 @cindex operands in expressions
3480 @cindex arithmetic operands
3481 @dfn{Arguments} are symbols, numbers or subexpressions. In other
3482 contexts arguments are sometimes called ``arithmetic operands''. In
3483 this manual, to avoid confusing them with the ``instruction operands'' of
3484 the machine language, we use the term ``argument'' to refer to parts of
3485 expressions only, reserving the word ``operand'' to refer only to machine
3486 instruction operands.
3488 Symbols are evaluated to yield @{@var{section} @var{NNN}@} where
3489 @var{section} is one of text, data, bss, absolute,
3490 or undefined. @var{NNN} is a signed, 2's complement 32 bit
3493 Numbers are usually integers.
3495 A number can be a flonum or bignum. In this case, you are warned
3496 that only the low order 32 bits are used, and @command{@value{AS}} pretends
3497 these 32 bits are an integer. You may write integer-manipulating
3498 instructions that act on exotic constants, compatible with other
3501 @cindex subexpressions
3502 Subexpressions are a left parenthesis @samp{(} followed by an integer
3503 expression, followed by a right parenthesis @samp{)}; or a prefix
3504 operator followed by an argument.
3507 @subsection Operators
3509 @cindex operators, in expressions
3510 @cindex arithmetic functions
3511 @cindex functions, in expressions
3512 @dfn{Operators} are arithmetic functions, like @code{+} or @code{%}. Prefix
3513 operators are followed by an argument. Infix operators appear
3514 between their arguments. Operators may be preceded and/or followed by
3518 @subsection Prefix Operator
3520 @cindex prefix operators
3521 @command{@value{AS}} has the following @dfn{prefix operators}. They each take
3522 one argument, which must be absolute.
3524 @c the tex/end tex stuff surrounding this small table is meant to make
3525 @c it align, on the printed page, with the similar table in the next
3526 @c section (which is inside an enumerate).
3528 \global\advance\leftskip by \itemindent
3533 @dfn{Negation}. Two's complement negation.
3535 @dfn{Complementation}. Bitwise not.
3539 \global\advance\leftskip by -\itemindent
3543 @subsection Infix Operators
3545 @cindex infix operators
3546 @cindex operators, permitted arguments
3547 @dfn{Infix operators} take two arguments, one on either side. Operators
3548 have precedence, but operations with equal precedence are performed left
3549 to right. Apart from @code{+} or @option{-}, both arguments must be
3550 absolute, and the result is absolute.
3553 @cindex operator precedence
3554 @cindex precedence of operators
3561 @dfn{Multiplication}.
3564 @dfn{Division}. Truncation is the same as the C operator @samp{/}
3571 @dfn{Shift Left}. Same as the C operator @samp{<<}.
3575 @dfn{Shift Right}. Same as the C operator @samp{>>}.
3579 Intermediate precedence
3584 @dfn{Bitwise Inclusive Or}.
3590 @dfn{Bitwise Exclusive Or}.
3593 @dfn{Bitwise Or Not}.
3600 @cindex addition, permitted arguments
3601 @cindex plus, permitted arguments
3602 @cindex arguments for addition
3604 @dfn{Addition}. If either argument is absolute, the result has the section of
3605 the other argument. You may not add together arguments from different
3608 @cindex subtraction, permitted arguments
3609 @cindex minus, permitted arguments
3610 @cindex arguments for subtraction
3612 @dfn{Subtraction}. If the right argument is absolute, the
3613 result has the section of the left argument.
3614 If both arguments are in the same section, the result is absolute.
3615 You may not subtract arguments from different sections.
3616 @c FIXME is there still something useful to say about undefined - undefined ?
3618 @cindex comparison expressions
3619 @cindex expressions, comparison
3623 @dfn{Is Not Equal To}
3627 @dfn{Is Greater Than}
3629 @dfn{Is Greater Than Or Equal To}
3631 @dfn{Is Less Than Or Equal To}
3633 The comparison operators can be used as infix operators. A true results has a
3634 value of -1 whereas a false result has a value of 0. Note, these operators
3635 perform signed comparisons.
3638 @item Lowest Precedence
3647 These two logical operations can be used to combine the results of sub
3648 expressions. Note, unlike the comparison operators a true result returns a
3649 value of 1 but a false results does still return 0. Also note that the logical
3650 or operator has a slightly lower precedence than logical and.
3655 In short, it's only meaningful to add or subtract the @emph{offsets} in an
3656 address; you can only have a defined section in one of the two arguments.
3659 @chapter Assembler Directives
3661 @cindex directives, machine independent
3662 @cindex pseudo-ops, machine independent
3663 @cindex machine independent directives
3664 All assembler directives have names that begin with a period (@samp{.}).
3665 The rest of the name is letters, usually in lower case.
3667 This chapter discusses directives that are available regardless of the
3668 target machine configuration for the @sc{gnu} assembler.
3670 Some machine configurations provide additional directives.
3671 @xref{Machine Dependencies}.
3674 @ifset machine-directives
3675 @xref{Machine Dependencies} for additional directives.
3680 * Abort:: @code{.abort}
3682 * ABORT:: @code{.ABORT}
3685 * Align:: @code{.align @var{abs-expr} , @var{abs-expr}}
3686 * Ascii:: @code{.ascii "@var{string}"}@dots{}
3687 * Asciz:: @code{.asciz "@var{string}"}@dots{}
3688 * Balign:: @code{.balign @var{abs-expr} , @var{abs-expr}}
3689 * Byte:: @code{.byte @var{expressions}}
3690 * Comm:: @code{.comm @var{symbol} , @var{length} }
3691 * Data:: @code{.data @var{subsection}}
3693 * Def:: @code{.def @var{name}}
3696 * Desc:: @code{.desc @var{symbol}, @var{abs-expression}}
3702 * Double:: @code{.double @var{flonums}}
3703 * Eject:: @code{.eject}
3704 * Else:: @code{.else}
3705 * Elseif:: @code{.elseif}
3708 * Endef:: @code{.endef}
3711 * Endfunc:: @code{.endfunc}
3712 * Endif:: @code{.endif}
3713 * Equ:: @code{.equ @var{symbol}, @var{expression}}
3714 * Equiv:: @code{.equiv @var{symbol}, @var{expression}}
3716 * Exitm:: @code{.exitm}
3717 * Extern:: @code{.extern}
3718 * Fail:: @code{.fail}
3719 @ifclear no-file-dir
3720 * File:: @code{.file @var{string}}
3723 * Fill:: @code{.fill @var{repeat} , @var{size} , @var{value}}
3724 * Float:: @code{.float @var{flonums}}
3725 * Func:: @code{.func}
3726 * Global:: @code{.global @var{symbol}}, @code{.globl @var{symbol}}
3728 * Hidden:: @code{.hidden @var{names}}
3731 * hword:: @code{.hword @var{expressions}}
3732 * Ident:: @code{.ident}
3733 * If:: @code{.if @var{absolute expression}}
3734 * Incbin:: @code{.incbin "@var{file}"[,@var{skip}[,@var{count}]]}
3735 * Include:: @code{.include "@var{file}"}
3736 * Int:: @code{.int @var{expressions}}
3738 * Internal:: @code{.internal @var{names}}
3741 * Irp:: @code{.irp @var{symbol},@var{values}}@dots{}
3742 * Irpc:: @code{.irpc @var{symbol},@var{values}}@dots{}
3743 * Lcomm:: @code{.lcomm @var{symbol} , @var{length}}
3744 * Lflags:: @code{.lflags}
3745 @ifclear no-line-dir
3746 * Line:: @code{.line @var{line-number}}
3749 * Ln:: @code{.ln @var{line-number}}
3750 * Linkonce:: @code{.linkonce [@var{type}]}
3751 * List:: @code{.list}
3752 * Long:: @code{.long @var{expressions}}
3754 * Lsym:: @code{.lsym @var{symbol}, @var{expression}}
3757 * Macro:: @code{.macro @var{name} @var{args}}@dots{}
3758 * MRI:: @code{.mri @var{val}}
3759 * Nolist:: @code{.nolist}
3760 * Octa:: @code{.octa @var{bignums}}
3761 * Org:: @code{.org @var{new-lc} , @var{fill}}
3762 * P2align:: @code{.p2align @var{abs-expr} , @var{abs-expr}}
3764 * PopSection:: @code{.popsection}
3765 * Previous:: @code{.previous}
3768 * Print:: @code{.print @var{string}}
3770 * Protected:: @code{.protected @var{names}}
3773 * Psize:: @code{.psize @var{lines}, @var{columns}}
3774 * Purgem:: @code{.purgem @var{name}}
3776 * PushSection:: @code{.pushsection @var{name}}
3779 * Quad:: @code{.quad @var{bignums}}
3780 * Rept:: @code{.rept @var{count}}
3781 * Sbttl:: @code{.sbttl "@var{subheading}"}
3783 * Scl:: @code{.scl @var{class}}
3786 * Section:: @code{.section @var{name}}
3789 * Set:: @code{.set @var{symbol}, @var{expression}}
3790 * Short:: @code{.short @var{expressions}}
3791 * Single:: @code{.single @var{flonums}}
3793 * Size:: @code{.size [@var{name} , @var{expression}]}
3796 * Skip:: @code{.skip @var{size} , @var{fill}}
3797 * Sleb128:: @code{.sleb128 @var{expressions}}
3798 * Space:: @code{.space @var{size} , @var{fill}}
3800 * Stab:: @code{.stabd, .stabn, .stabs}
3803 * String:: @code{.string "@var{str}"}
3804 * Struct:: @code{.struct @var{expression}}
3806 * SubSection:: @code{.subsection}
3807 * Symver:: @code{.symver @var{name},@var{name2@@nodename}}
3811 * Tag:: @code{.tag @var{structname}}
3814 * Text:: @code{.text @var{subsection}}
3815 * Title:: @code{.title "@var{heading}"}
3817 * Type:: @code{.type <@var{int} | @var{name} , @var{type description}>}
3820 * Uleb128:: @code{.uleb128 @var{expressions}}
3822 * Val:: @code{.val @var{addr}}
3826 * Version:: @code{.version "@var{string}"}
3827 * VTableEntry:: @code{.vtable_entry @var{table}, @var{offset}}
3828 * VTableInherit:: @code{.vtable_inherit @var{child}, @var{parent}}
3829 * Weak:: @code{.weak @var{names}}
3832 * Word:: @code{.word @var{expressions}}
3833 * Deprecated:: Deprecated Directives
3837 @section @code{.abort}
3839 @cindex @code{abort} directive
3840 @cindex stopping the assembly
3841 This directive stops the assembly immediately. It is for
3842 compatibility with other assemblers. The original idea was that the
3843 assembly language source would be piped into the assembler. If the sender
3844 of the source quit, it could use this directive tells @command{@value{AS}} to
3845 quit also. One day @code{.abort} will not be supported.
3849 @section @code{.ABORT}
3851 @cindex @code{ABORT} directive
3852 When producing COFF output, @command{@value{AS}} accepts this directive as a
3853 synonym for @samp{.abort}.
3856 When producing @code{b.out} output, @command{@value{AS}} accepts this directive,
3862 @section @code{.align @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
3864 @cindex padding the location counter
3865 @cindex @code{align} directive
3866 Pad the location counter (in the current subsection) to a particular storage
3867 boundary. The first expression (which must be absolute) is the alignment
3868 required, as described below.
3870 The second expression (also absolute) gives the fill value to be stored in the
3871 padding bytes. It (and the comma) may be omitted. If it is omitted, the
3872 padding bytes are normally zero. However, on some systems, if the section is
3873 marked as containing code and the fill value is omitted, the space is filled
3874 with no-op instructions.
3876 The third expression is also absolute, and is also optional. If it is present,
3877 it is the maximum number of bytes that should be skipped by this alignment
3878 directive. If doing the alignment would require skipping more bytes than the
3879 specified maximum, then the alignment is not done at all. You can omit the
3880 fill value (the second argument) entirely by simply using two commas after the
3881 required alignment; this can be useful if you want the alignment to be filled
3882 with no-op instructions when appropriate.
3884 The way the required alignment is specified varies from system to system.
3885 For the a29k, hppa, m68k, m88k, w65, sparc, Xtensa, and Renesas SH, and i386 using ELF
3887 the first expression is the
3888 alignment request in bytes. For example @samp{.align 8} advances
3889 the location counter until it is a multiple of 8. If the location counter
3890 is already a multiple of 8, no change is needed.
3892 For other systems, including the i386 using a.out format, and the arm and
3893 strongarm, it is the
3894 number of low-order zero bits the location counter must have after
3895 advancement. For example @samp{.align 3} advances the location
3896 counter until it a multiple of 8. If the location counter is already a
3897 multiple of 8, no change is needed.
3899 This inconsistency is due to the different behaviors of the various
3900 native assemblers for these systems which GAS must emulate.
3901 GAS also provides @code{.balign} and @code{.p2align} directives,
3902 described later, which have a consistent behavior across all
3903 architectures (but are specific to GAS).
3906 @section @code{.ascii "@var{string}"}@dots{}
3908 @cindex @code{ascii} directive
3909 @cindex string literals
3910 @code{.ascii} expects zero or more string literals (@pxref{Strings})
3911 separated by commas. It assembles each string (with no automatic
3912 trailing zero byte) into consecutive addresses.
3915 @section @code{.asciz "@var{string}"}@dots{}
3917 @cindex @code{asciz} directive
3918 @cindex zero-terminated strings
3919 @cindex null-terminated strings
3920 @code{.asciz} is just like @code{.ascii}, but each string is followed by
3921 a zero byte. The ``z'' in @samp{.asciz} stands for ``zero''.
3924 @section @code{.balign[wl] @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
3926 @cindex padding the location counter given number of bytes
3927 @cindex @code{balign} directive
3928 Pad the location counter (in the current subsection) to a particular
3929 storage boundary. The first expression (which must be absolute) is the
3930 alignment request in bytes. For example @samp{.balign 8} advances
3931 the location counter until it is a multiple of 8. If the location counter
3932 is already a multiple of 8, no change is needed.
3934 The second expression (also absolute) gives the fill value to be stored in the
3935 padding bytes. It (and the comma) may be omitted. If it is omitted, the
3936 padding bytes are normally zero. However, on some systems, if the section is
3937 marked as containing code and the fill value is omitted, the space is filled
3938 with no-op instructions.
3940 The third expression is also absolute, and is also optional. If it is present,
3941 it is the maximum number of bytes that should be skipped by this alignment
3942 directive. If doing the alignment would require skipping more bytes than the
3943 specified maximum, then the alignment is not done at all. You can omit the
3944 fill value (the second argument) entirely by simply using two commas after the
3945 required alignment; this can be useful if you want the alignment to be filled
3946 with no-op instructions when appropriate.
3948 @cindex @code{balignw} directive
3949 @cindex @code{balignl} directive
3950 The @code{.balignw} and @code{.balignl} directives are variants of the
3951 @code{.balign} directive. The @code{.balignw} directive treats the fill
3952 pattern as a two byte word value. The @code{.balignl} directives treats the
3953 fill pattern as a four byte longword value. For example, @code{.balignw
3954 4,0x368d} will align to a multiple of 4. If it skips two bytes, they will be
3955 filled in with the value 0x368d (the exact placement of the bytes depends upon
3956 the endianness of the processor). If it skips 1 or 3 bytes, the fill value is
3960 @section @code{.byte @var{expressions}}
3962 @cindex @code{byte} directive
3963 @cindex integers, one byte
3964 @code{.byte} expects zero or more expressions, separated by commas.
3965 Each expression is assembled into the next byte.
3968 @section @code{.comm @var{symbol} , @var{length} }
3970 @cindex @code{comm} directive
3971 @cindex symbol, common
3972 @code{.comm} declares a common symbol named @var{symbol}. When linking, a
3973 common symbol in one object file may be merged with a defined or common symbol
3974 of the same name in another object file. If @code{@value{LD}} does not see a
3975 definition for the symbol--just one or more common symbols--then it will
3976 allocate @var{length} bytes of uninitialized memory. @var{length} must be an
3977 absolute expression. If @code{@value{LD}} sees multiple common symbols with
3978 the same name, and they do not all have the same size, it will allocate space
3979 using the largest size.
3982 When using ELF, the @code{.comm} directive takes an optional third argument.
3983 This is the desired alignment of the symbol, specified as a byte boundary (for
3984 example, an alignment of 16 means that the least significant 4 bits of the
3985 address should be zero). The alignment must be an absolute expression, and it
3986 must be a power of two. If @code{@value{LD}} allocates uninitialized memory
3987 for the common symbol, it will use the alignment when placing the symbol. If
3988 no alignment is specified, @command{@value{AS}} will set the alignment to the
3989 largest power of two less than or equal to the size of the symbol, up to a
3994 The syntax for @code{.comm} differs slightly on the HPPA. The syntax is
3995 @samp{@var{symbol} .comm, @var{length}}; @var{symbol} is optional.
3999 @section @code{.data @var{subsection}}
4001 @cindex @code{data} directive
4002 @code{.data} tells @command{@value{AS}} to assemble the following statements onto the
4003 end of the data subsection numbered @var{subsection} (which is an
4004 absolute expression). If @var{subsection} is omitted, it defaults
4009 @section @code{.def @var{name}}
4011 @cindex @code{def} directive
4012 @cindex COFF symbols, debugging
4013 @cindex debugging COFF symbols
4014 Begin defining debugging information for a symbol @var{name}; the
4015 definition extends until the @code{.endef} directive is encountered.
4018 This directive is only observed when @command{@value{AS}} is configured for COFF
4019 format output; when producing @code{b.out}, @samp{.def} is recognized,
4026 @section @code{.desc @var{symbol}, @var{abs-expression}}
4028 @cindex @code{desc} directive
4029 @cindex COFF symbol descriptor
4030 @cindex symbol descriptor, COFF
4031 This directive sets the descriptor of the symbol (@pxref{Symbol Attributes})
4032 to the low 16 bits of an absolute expression.
4035 The @samp{.desc} directive is not available when @command{@value{AS}} is
4036 configured for COFF output; it is only for @code{a.out} or @code{b.out}
4037 object format. For the sake of compatibility, @command{@value{AS}} accepts
4038 it, but produces no output, when configured for COFF.
4044 @section @code{.dim}
4046 @cindex @code{dim} directive
4047 @cindex COFF auxiliary symbol information
4048 @cindex auxiliary symbol information, COFF
4049 This directive is generated by compilers to include auxiliary debugging
4050 information in the symbol table. It is only permitted inside
4051 @code{.def}/@code{.endef} pairs.
4054 @samp{.dim} is only meaningful when generating COFF format output; when
4055 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
4061 @section @code{.double @var{flonums}}
4063 @cindex @code{double} directive
4064 @cindex floating point numbers (double)
4065 @code{.double} expects zero or more flonums, separated by commas. It
4066 assembles floating point numbers.
4068 The exact kind of floating point numbers emitted depends on how
4069 @command{@value{AS}} is configured. @xref{Machine Dependencies}.
4073 On the @value{TARGET} family @samp{.double} emits 64-bit floating-point numbers
4074 in @sc{ieee} format.
4079 @section @code{.eject}
4081 @cindex @code{eject} directive
4082 @cindex new page, in listings
4083 @cindex page, in listings
4084 @cindex listing control: new page
4085 Force a page break at this point, when generating assembly listings.
4088 @section @code{.else}
4090 @cindex @code{else} directive
4091 @code{.else} is part of the @command{@value{AS}} support for conditional
4092 assembly; @pxref{If,,@code{.if}}. It marks the beginning of a section
4093 of code to be assembled if the condition for the preceding @code{.if}
4097 @section @code{.elseif}
4099 @cindex @code{elseif} directive
4100 @code{.elseif} is part of the @command{@value{AS}} support for conditional
4101 assembly; @pxref{If,,@code{.if}}. It is shorthand for beginning a new
4102 @code{.if} block that would otherwise fill the entire @code{.else} section.
4105 @section @code{.end}
4107 @cindex @code{end} directive
4108 @code{.end} marks the end of the assembly file. @command{@value{AS}} does not
4109 process anything in the file past the @code{.end} directive.
4113 @section @code{.endef}
4115 @cindex @code{endef} directive
4116 This directive flags the end of a symbol definition begun with
4120 @samp{.endef} is only meaningful when generating COFF format output; if
4121 @command{@value{AS}} is configured to generate @code{b.out}, it accepts this
4122 directive but ignores it.
4127 @section @code{.endfunc}
4128 @cindex @code{endfunc} directive
4129 @code{.endfunc} marks the end of a function specified with @code{.func}.
4132 @section @code{.endif}
4134 @cindex @code{endif} directive
4135 @code{.endif} is part of the @command{@value{AS}} support for conditional assembly;
4136 it marks the end of a block of code that is only assembled
4137 conditionally. @xref{If,,@code{.if}}.
4140 @section @code{.equ @var{symbol}, @var{expression}}
4142 @cindex @code{equ} directive
4143 @cindex assigning values to symbols
4144 @cindex symbols, assigning values to
4145 This directive sets the value of @var{symbol} to @var{expression}.
4146 It is synonymous with @samp{.set}; @pxref{Set,,@code{.set}}.
4149 The syntax for @code{equ} on the HPPA is
4150 @samp{@var{symbol} .equ @var{expression}}.
4154 @section @code{.equiv @var{symbol}, @var{expression}}
4155 @cindex @code{equiv} directive
4156 The @code{.equiv} directive is like @code{.equ} and @code{.set}, except that
4157 the assembler will signal an error if @var{symbol} is already defined. Note a
4158 symbol which has been referenced but not actually defined is considered to be
4161 Except for the contents of the error message, this is roughly equivalent to
4170 @section @code{.err}
4171 @cindex @code{err} directive
4172 If @command{@value{AS}} assembles a @code{.err} directive, it will print an error
4173 message and, unless the @option{-Z} option was used, it will not generate an
4174 object file. This can be used to signal error an conditionally compiled code.
4177 @section @code{.exitm}
4178 Exit early from the current macro definition. @xref{Macro}.
4181 @section @code{.extern}
4183 @cindex @code{extern} directive
4184 @code{.extern} is accepted in the source program---for compatibility
4185 with other assemblers---but it is ignored. @command{@value{AS}} treats
4186 all undefined symbols as external.
4189 @section @code{.fail @var{expression}}
4191 @cindex @code{fail} directive
4192 Generates an error or a warning. If the value of the @var{expression} is 500
4193 or more, @command{@value{AS}} will print a warning message. If the value is less
4194 than 500, @command{@value{AS}} will print an error message. The message will
4195 include the value of @var{expression}. This can occasionally be useful inside
4196 complex nested macros or conditional assembly.
4198 @ifclear no-file-dir
4200 @section @code{.file @var{string}}
4202 @cindex @code{file} directive
4203 @cindex logical file name
4204 @cindex file name, logical
4205 @code{.file} tells @command{@value{AS}} that we are about to start a new logical
4206 file. @var{string} is the new file name. In general, the filename is
4207 recognized whether or not it is surrounded by quotes @samp{"}; but if you wish
4208 to specify an empty file name, you must give the quotes--@code{""}. This
4209 statement may go away in future: it is only recognized to be compatible with
4210 old @command{@value{AS}} programs.
4212 In some configurations of @command{@value{AS}}, @code{.file} has already been
4213 removed to avoid conflicts with other assemblers. @xref{Machine Dependencies}.
4218 @section @code{.fill @var{repeat} , @var{size} , @var{value}}
4220 @cindex @code{fill} directive
4221 @cindex writing patterns in memory
4222 @cindex patterns, writing in memory
4223 @var{repeat}, @var{size} and @var{value} are absolute expressions.
4224 This emits @var{repeat} copies of @var{size} bytes. @var{Repeat}
4225 may be zero or more. @var{Size} may be zero or more, but if it is
4226 more than 8, then it is deemed to have the value 8, compatible with
4227 other people's assemblers. The contents of each @var{repeat} bytes
4228 is taken from an 8-byte number. The highest order 4 bytes are
4229 zero. The lowest order 4 bytes are @var{value} rendered in the
4230 byte-order of an integer on the computer @command{@value{AS}} is assembling for.
4231 Each @var{size} bytes in a repetition is taken from the lowest order
4232 @var{size} bytes of this number. Again, this bizarre behavior is
4233 compatible with other people's assemblers.
4235 @var{size} and @var{value} are optional.
4236 If the second comma and @var{value} are absent, @var{value} is
4237 assumed zero. If the first comma and following tokens are absent,
4238 @var{size} is assumed to be 1.
4241 @section @code{.float @var{flonums}}
4243 @cindex floating point numbers (single)
4244 @cindex @code{float} directive
4245 This directive assembles zero or more flonums, separated by commas. It
4246 has the same effect as @code{.single}.
4248 The exact kind of floating point numbers emitted depends on how
4249 @command{@value{AS}} is configured.
4250 @xref{Machine Dependencies}.
4254 On the @value{TARGET} family, @code{.float} emits 32-bit floating point numbers
4255 in @sc{ieee} format.
4260 @section @code{.func @var{name}[,@var{label}]}
4261 @cindex @code{func} directive
4262 @code{.func} emits debugging information to denote function @var{name}, and
4263 is ignored unless the file is assembled with debugging enabled.
4264 Only @samp{--gstabs} is currently supported.
4265 @var{label} is the entry point of the function and if omitted @var{name}
4266 prepended with the @samp{leading char} is used.
4267 @samp{leading char} is usually @code{_} or nothing, depending on the target.
4268 All functions are currently defined to have @code{void} return type.
4269 The function must be terminated with @code{.endfunc}.
4272 @section @code{.global @var{symbol}}, @code{.globl @var{symbol}}
4274 @cindex @code{global} directive
4275 @cindex symbol, making visible to linker
4276 @code{.global} makes the symbol visible to @code{@value{LD}}. If you define
4277 @var{symbol} in your partial program, its value is made available to
4278 other partial programs that are linked with it. Otherwise,
4279 @var{symbol} takes its attributes from a symbol of the same name
4280 from another file linked into the same program.
4282 Both spellings (@samp{.globl} and @samp{.global}) are accepted, for
4283 compatibility with other assemblers.
4286 On the HPPA, @code{.global} is not always enough to make it accessible to other
4287 partial programs. You may need the HPPA-only @code{.EXPORT} directive as well.
4288 @xref{HPPA Directives,, HPPA Assembler Directives}.
4293 @section @code{.hidden @var{names}}
4295 @cindex @code{hidden} directive
4297 This one of the ELF visibility directives. The other two are
4298 @code{.internal} (@pxref{Internal,,@code{.internal}}) and
4299 @code{.protected} (@pxref{Protected,,@code{.protected}}).
4301 This directive overrides the named symbols default visibility (which is set by
4302 their binding: local, global or weak). The directive sets the visibility to
4303 @code{hidden} which means that the symbols are not visible to other components.
4304 Such symbols are always considered to be @code{protected} as well.
4308 @section @code{.hword @var{expressions}}
4310 @cindex @code{hword} directive
4311 @cindex integers, 16-bit
4312 @cindex numbers, 16-bit
4313 @cindex sixteen bit integers
4314 This expects zero or more @var{expressions}, and emits
4315 a 16 bit number for each.
4318 This directive is a synonym for @samp{.short}; depending on the target
4319 architecture, it may also be a synonym for @samp{.word}.
4323 This directive is a synonym for @samp{.short}.
4326 This directive is a synonym for both @samp{.short} and @samp{.word}.
4331 @section @code{.ident}
4333 @cindex @code{ident} directive
4334 This directive is used by some assemblers to place tags in object files.
4335 @command{@value{AS}} simply accepts the directive for source-file
4336 compatibility with such assemblers, but does not actually emit anything
4340 @section @code{.if @var{absolute expression}}
4342 @cindex conditional assembly
4343 @cindex @code{if} directive
4344 @code{.if} marks the beginning of a section of code which is only
4345 considered part of the source program being assembled if the argument
4346 (which must be an @var{absolute expression}) is non-zero. The end of
4347 the conditional section of code must be marked by @code{.endif}
4348 (@pxref{Endif,,@code{.endif}}); optionally, you may include code for the
4349 alternative condition, flagged by @code{.else} (@pxref{Else,,@code{.else}}).
4350 If you have several conditions to check, @code{.elseif} may be used to avoid
4351 nesting blocks if/else within each subsequent @code{.else} block.
4353 The following variants of @code{.if} are also supported:
4355 @cindex @code{ifdef} directive
4356 @item .ifdef @var{symbol}
4357 Assembles the following section of code if the specified @var{symbol}
4358 has been defined. Note a symbol which has been referenced but not yet defined
4359 is considered to be undefined.
4361 @cindex @code{ifc} directive
4362 @item .ifc @var{string1},@var{string2}
4363 Assembles the following section of code if the two strings are the same. The
4364 strings may be optionally quoted with single quotes. If they are not quoted,
4365 the first string stops at the first comma, and the second string stops at the
4366 end of the line. Strings which contain whitespace should be quoted. The
4367 string comparison is case sensitive.
4369 @cindex @code{ifeq} directive
4370 @item .ifeq @var{absolute expression}
4371 Assembles the following section of code if the argument is zero.
4373 @cindex @code{ifeqs} directive
4374 @item .ifeqs @var{string1},@var{string2}
4375 Another form of @code{.ifc}. The strings must be quoted using double quotes.
4377 @cindex @code{ifge} directive
4378 @item .ifge @var{absolute expression}
4379 Assembles the following section of code if the argument is greater than or
4382 @cindex @code{ifgt} directive
4383 @item .ifgt @var{absolute expression}
4384 Assembles the following section of code if the argument is greater than zero.
4386 @cindex @code{ifle} directive
4387 @item .ifle @var{absolute expression}
4388 Assembles the following section of code if the argument is less than or equal
4391 @cindex @code{iflt} directive
4392 @item .iflt @var{absolute expression}
4393 Assembles the following section of code if the argument is less than zero.
4395 @cindex @code{ifnc} directive
4396 @item .ifnc @var{string1},@var{string2}.
4397 Like @code{.ifc}, but the sense of the test is reversed: this assembles the
4398 following section of code if the two strings are not the same.
4400 @cindex @code{ifndef} directive
4401 @cindex @code{ifnotdef} directive
4402 @item .ifndef @var{symbol}
4403 @itemx .ifnotdef @var{symbol}
4404 Assembles the following section of code if the specified @var{symbol}
4405 has not been defined. Both spelling variants are equivalent. Note a symbol
4406 which has been referenced but not yet defined is considered to be undefined.
4408 @cindex @code{ifne} directive
4409 @item .ifne @var{absolute expression}
4410 Assembles the following section of code if the argument is not equal to zero
4411 (in other words, this is equivalent to @code{.if}).
4413 @cindex @code{ifnes} directive
4414 @item .ifnes @var{string1},@var{string2}
4415 Like @code{.ifeqs}, but the sense of the test is reversed: this assembles the
4416 following section of code if the two strings are not the same.
4420 @section @code{.incbin "@var{file}"[,@var{skip}[,@var{count}]]}
4422 @cindex @code{incbin} directive
4423 @cindex binary files, including
4424 The @code{incbin} directive includes @var{file} verbatim at the current
4425 location. You can control the search paths used with the @samp{-I} command-line
4426 option (@pxref{Invoking,,Command-Line Options}). Quotation marks are required
4429 The @var{skip} argument skips a number of bytes from the start of the
4430 @var{file}. The @var{count} argument indicates the maximum number of bytes to
4431 read. Note that the data is not aligned in any way, so it is the user's
4432 responsibility to make sure that proper alignment is provided both before and
4433 after the @code{incbin} directive.
4436 @section @code{.include "@var{file}"}
4438 @cindex @code{include} directive
4439 @cindex supporting files, including
4440 @cindex files, including
4441 This directive provides a way to include supporting files at specified
4442 points in your source program. The code from @var{file} is assembled as
4443 if it followed the point of the @code{.include}; when the end of the
4444 included file is reached, assembly of the original file continues. You
4445 can control the search paths used with the @samp{-I} command-line option
4446 (@pxref{Invoking,,Command-Line Options}). Quotation marks are required
4450 @section @code{.int @var{expressions}}
4452 @cindex @code{int} directive
4453 @cindex integers, 32-bit
4454 Expect zero or more @var{expressions}, of any section, separated by commas.
4455 For each expression, emit a number that, at run time, is the value of that
4456 expression. The byte order and bit size of the number depends on what kind
4457 of target the assembly is for.
4461 On the H8/500 and most forms of the H8/300, @code{.int} emits 16-bit
4462 integers. On the H8/300H and the Renesas SH, however, @code{.int} emits
4469 @section @code{.internal @var{names}}
4471 @cindex @code{internal} directive
4473 This one of the ELF visibility directives. The other two are
4474 @code{.hidden} (@pxref{Hidden,,@code{.hidden}}) and
4475 @code{.protected} (@pxref{Protected,,@code{.protected}}).
4477 This directive overrides the named symbols default visibility (which is set by
4478 their binding: local, global or weak). The directive sets the visibility to
4479 @code{internal} which means that the symbols are considered to be @code{hidden}
4480 (i.e., not visible to other components), and that some extra, processor specific
4481 processing must also be performed upon the symbols as well.
4485 @section @code{.irp @var{symbol},@var{values}}@dots{}
4487 @cindex @code{irp} directive
4488 Evaluate a sequence of statements assigning different values to @var{symbol}.
4489 The sequence of statements starts at the @code{.irp} directive, and is
4490 terminated by an @code{.endr} directive. For each @var{value}, @var{symbol} is
4491 set to @var{value}, and the sequence of statements is assembled. If no
4492 @var{value} is listed, the sequence of statements is assembled once, with
4493 @var{symbol} set to the null string. To refer to @var{symbol} within the
4494 sequence of statements, use @var{\symbol}.
4496 For example, assembling
4504 is equivalent to assembling
4513 @section @code{.irpc @var{symbol},@var{values}}@dots{}
4515 @cindex @code{irpc} directive
4516 Evaluate a sequence of statements assigning different values to @var{symbol}.
4517 The sequence of statements starts at the @code{.irpc} directive, and is
4518 terminated by an @code{.endr} directive. For each character in @var{value},
4519 @var{symbol} is set to the character, and the sequence of statements is
4520 assembled. If no @var{value} is listed, the sequence of statements is
4521 assembled once, with @var{symbol} set to the null string. To refer to
4522 @var{symbol} within the sequence of statements, use @var{\symbol}.
4524 For example, assembling
4532 is equivalent to assembling
4541 @section @code{.lcomm @var{symbol} , @var{length}}
4543 @cindex @code{lcomm} directive
4544 @cindex local common symbols
4545 @cindex symbols, local common
4546 Reserve @var{length} (an absolute expression) bytes for a local common
4547 denoted by @var{symbol}. The section and value of @var{symbol} are
4548 those of the new local common. The addresses are allocated in the bss
4549 section, so that at run-time the bytes start off zeroed. @var{Symbol}
4550 is not declared global (@pxref{Global,,@code{.global}}), so is normally
4551 not visible to @code{@value{LD}}.
4554 Some targets permit a third argument to be used with @code{.lcomm}. This
4555 argument specifies the desired alignment of the symbol in the bss section.
4559 The syntax for @code{.lcomm} differs slightly on the HPPA. The syntax is
4560 @samp{@var{symbol} .lcomm, @var{length}}; @var{symbol} is optional.
4564 @section @code{.lflags}
4566 @cindex @code{lflags} directive (ignored)
4567 @command{@value{AS}} accepts this directive, for compatibility with other
4568 assemblers, but ignores it.
4570 @ifclear no-line-dir
4572 @section @code{.line @var{line-number}}
4574 @cindex @code{line} directive
4578 @section @code{.ln @var{line-number}}
4580 @cindex @code{ln} directive
4582 @cindex logical line number
4584 Change the logical line number. @var{line-number} must be an absolute
4585 expression. The next line has that logical line number. Therefore any other
4586 statements on the current line (after a statement separator character) are
4587 reported as on logical line number @var{line-number} @minus{} 1. One day
4588 @command{@value{AS}} will no longer support this directive: it is recognized only
4589 for compatibility with existing assembler programs.
4593 @emph{Warning:} In the AMD29K configuration of @value{AS}, this command is
4594 not available; use the synonym @code{.ln} in that context.
4599 @ifclear no-line-dir
4600 Even though this is a directive associated with the @code{a.out} or
4601 @code{b.out} object-code formats, @command{@value{AS}} still recognizes it
4602 when producing COFF output, and treats @samp{.line} as though it
4603 were the COFF @samp{.ln} @emph{if} it is found outside a
4604 @code{.def}/@code{.endef} pair.
4606 Inside a @code{.def}, @samp{.line} is, instead, one of the directives
4607 used by compilers to generate auxiliary symbol information for
4612 @section @code{.linkonce [@var{type}]}
4614 @cindex @code{linkonce} directive
4615 @cindex common sections
4616 Mark the current section so that the linker only includes a single copy of it.
4617 This may be used to include the same section in several different object files,
4618 but ensure that the linker will only include it once in the final output file.
4619 The @code{.linkonce} pseudo-op must be used for each instance of the section.
4620 Duplicate sections are detected based on the section name, so it should be
4623 This directive is only supported by a few object file formats; as of this
4624 writing, the only object file format which supports it is the Portable
4625 Executable format used on Windows NT.
4627 The @var{type} argument is optional. If specified, it must be one of the
4628 following strings. For example:
4632 Not all types may be supported on all object file formats.
4636 Silently discard duplicate sections. This is the default.
4639 Warn if there are duplicate sections, but still keep only one copy.
4642 Warn if any of the duplicates have different sizes.
4645 Warn if any of the duplicates do not have exactly the same contents.
4649 @section @code{.ln @var{line-number}}
4651 @cindex @code{ln} directive
4652 @ifclear no-line-dir
4653 @samp{.ln} is a synonym for @samp{.line}.
4656 Tell @command{@value{AS}} to change the logical line number. @var{line-number}
4657 must be an absolute expression. The next line has that logical
4658 line number, so any other statements on the current line (after a
4659 statement separator character @code{;}) are reported as on logical
4660 line number @var{line-number} @minus{} 1.
4663 This directive is accepted, but ignored, when @command{@value{AS}} is
4664 configured for @code{b.out}; its effect is only associated with COFF
4670 @section @code{.mri @var{val}}
4672 @cindex @code{mri} directive
4673 @cindex MRI mode, temporarily
4674 If @var{val} is non-zero, this tells @command{@value{AS}} to enter MRI mode. If
4675 @var{val} is zero, this tells @command{@value{AS}} to exit MRI mode. This change
4676 affects code assembled until the next @code{.mri} directive, or until the end
4677 of the file. @xref{M, MRI mode, MRI mode}.
4680 @section @code{.list}
4682 @cindex @code{list} directive
4683 @cindex listing control, turning on
4684 Control (in conjunction with the @code{.nolist} directive) whether or
4685 not assembly listings are generated. These two directives maintain an
4686 internal counter (which is zero initially). @code{.list} increments the
4687 counter, and @code{.nolist} decrements it. Assembly listings are
4688 generated whenever the counter is greater than zero.
4690 By default, listings are disabled. When you enable them (with the
4691 @samp{-a} command line option; @pxref{Invoking,,Command-Line Options}),
4692 the initial value of the listing counter is one.
4695 @section @code{.long @var{expressions}}
4697 @cindex @code{long} directive
4698 @code{.long} is the same as @samp{.int}, @pxref{Int,,@code{.int}}.
4701 @c no one seems to know what this is for or whether this description is
4702 @c what it really ought to do
4704 @section @code{.lsym @var{symbol}, @var{expression}}
4706 @cindex @code{lsym} directive
4707 @cindex symbol, not referenced in assembly
4708 @code{.lsym} creates a new symbol named @var{symbol}, but does not put it in
4709 the hash table, ensuring it cannot be referenced by name during the
4710 rest of the assembly. This sets the attributes of the symbol to be
4711 the same as the expression value:
4713 @var{other} = @var{descriptor} = 0
4714 @var{type} = @r{(section of @var{expression})}
4715 @var{value} = @var{expression}
4718 The new symbol is not flagged as external.
4722 @section @code{.macro}
4725 The commands @code{.macro} and @code{.endm} allow you to define macros that
4726 generate assembly output. For example, this definition specifies a macro
4727 @code{sum} that puts a sequence of numbers into memory:
4730 .macro sum from=0, to=5
4739 With that definition, @samp{SUM 0,5} is equivalent to this assembly input:
4751 @item .macro @var{macname}
4752 @itemx .macro @var{macname} @var{macargs} @dots{}
4753 @cindex @code{macro} directive
4754 Begin the definition of a macro called @var{macname}. If your macro
4755 definition requires arguments, specify their names after the macro name,
4756 separated by commas or spaces. You can supply a default value for any
4757 macro argument by following the name with @samp{=@var{deflt}}. For
4758 example, these are all valid @code{.macro} statements:
4762 Begin the definition of a macro called @code{comm}, which takes no
4765 @item .macro plus1 p, p1
4766 @itemx .macro plus1 p p1
4767 Either statement begins the definition of a macro called @code{plus1},
4768 which takes two arguments; within the macro definition, write
4769 @samp{\p} or @samp{\p1} to evaluate the arguments.
4771 @item .macro reserve_str p1=0 p2
4772 Begin the definition of a macro called @code{reserve_str}, with two
4773 arguments. The first argument has a default value, but not the second.
4774 After the definition is complete, you can call the macro either as
4775 @samp{reserve_str @var{a},@var{b}} (with @samp{\p1} evaluating to
4776 @var{a} and @samp{\p2} evaluating to @var{b}), or as @samp{reserve_str
4777 ,@var{b}} (with @samp{\p1} evaluating as the default, in this case
4778 @samp{0}, and @samp{\p2} evaluating to @var{b}).
4781 When you call a macro, you can specify the argument values either by
4782 position, or by keyword. For example, @samp{sum 9,17} is equivalent to
4783 @samp{sum to=17, from=9}.
4786 @cindex @code{endm} directive
4787 Mark the end of a macro definition.
4790 @cindex @code{exitm} directive
4791 Exit early from the current macro definition.
4793 @cindex number of macros executed
4794 @cindex macros, count executed
4796 @command{@value{AS}} maintains a counter of how many macros it has
4797 executed in this pseudo-variable; you can copy that number to your
4798 output with @samp{\@@}, but @emph{only within a macro definition}.
4801 @item LOCAL @var{name} [ , @dots{} ]
4802 @emph{Warning: @code{LOCAL} is only available if you select ``alternate
4803 macro syntax'' with @samp{-a} or @samp{--alternate}.} @xref{Alternate,,
4804 Alternate macro syntax}.
4806 Generate a string replacement for each of the @var{name} arguments, and
4807 replace any instances of @var{name} in each macro expansion. The
4808 replacement string is unique in the assembly, and different for each
4809 separate macro expansion. @code{LOCAL} allows you to write macros that
4810 define symbols, without fear of conflict between separate macro expansions.
4815 @section @code{.nolist}
4817 @cindex @code{nolist} directive
4818 @cindex listing control, turning off
4819 Control (in conjunction with the @code{.list} directive) whether or
4820 not assembly listings are generated. These two directives maintain an
4821 internal counter (which is zero initially). @code{.list} increments the
4822 counter, and @code{.nolist} decrements it. Assembly listings are
4823 generated whenever the counter is greater than zero.
4826 @section @code{.octa @var{bignums}}
4828 @c FIXME: double size emitted for "octa" on i960, others? Or warn?
4829 @cindex @code{octa} directive
4830 @cindex integer, 16-byte
4831 @cindex sixteen byte integer
4832 This directive expects zero or more bignums, separated by commas. For each
4833 bignum, it emits a 16-byte integer.
4835 The term ``octa'' comes from contexts in which a ``word'' is two bytes;
4836 hence @emph{octa}-word for 16 bytes.
4839 @section @code{.org @var{new-lc} , @var{fill}}
4841 @cindex @code{org} directive
4842 @cindex location counter, advancing
4843 @cindex advancing location counter
4844 @cindex current address, advancing
4845 Advance the location counter of the current section to
4846 @var{new-lc}. @var{new-lc} is either an absolute expression or an
4847 expression with the same section as the current subsection. That is,
4848 you can't use @code{.org} to cross sections: if @var{new-lc} has the
4849 wrong section, the @code{.org} directive is ignored. To be compatible
4850 with former assemblers, if the section of @var{new-lc} is absolute,
4851 @command{@value{AS}} issues a warning, then pretends the section of @var{new-lc}
4852 is the same as the current subsection.
4854 @code{.org} may only increase the location counter, or leave it
4855 unchanged; you cannot use @code{.org} to move the location counter
4858 @c double negative used below "not undefined" because this is a specific
4859 @c reference to "undefined" (as SEG_UNKNOWN is called in this manual)
4860 @c section. doc@cygnus.com 18feb91
4861 Because @command{@value{AS}} tries to assemble programs in one pass, @var{new-lc}
4862 may not be undefined. If you really detest this restriction we eagerly await
4863 a chance to share your improved assembler.
4865 Beware that the origin is relative to the start of the section, not
4866 to the start of the subsection. This is compatible with other
4867 people's assemblers.
4869 When the location counter (of the current subsection) is advanced, the
4870 intervening bytes are filled with @var{fill} which should be an
4871 absolute expression. If the comma and @var{fill} are omitted,
4872 @var{fill} defaults to zero.
4875 @section @code{.p2align[wl] @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
4877 @cindex padding the location counter given a power of two
4878 @cindex @code{p2align} directive
4879 Pad the location counter (in the current subsection) to a particular
4880 storage boundary. The first expression (which must be absolute) is the
4881 number of low-order zero bits the location counter must have after
4882 advancement. For example @samp{.p2align 3} advances the location
4883 counter until it a multiple of 8. If the location counter is already a
4884 multiple of 8, no change is needed.
4886 The second expression (also absolute) gives the fill value to be stored in the
4887 padding bytes. It (and the comma) may be omitted. If it is omitted, the
4888 padding bytes are normally zero. However, on some systems, if the section is
4889 marked as containing code and the fill value is omitted, the space is filled
4890 with no-op instructions.
4892 The third expression is also absolute, and is also optional. If it is present,
4893 it is the maximum number of bytes that should be skipped by this alignment
4894 directive. If doing the alignment would require skipping more bytes than the
4895 specified maximum, then the alignment is not done at all. You can omit the
4896 fill value (the second argument) entirely by simply using two commas after the
4897 required alignment; this can be useful if you want the alignment to be filled
4898 with no-op instructions when appropriate.
4900 @cindex @code{p2alignw} directive
4901 @cindex @code{p2alignl} directive
4902 The @code{.p2alignw} and @code{.p2alignl} directives are variants of the
4903 @code{.p2align} directive. The @code{.p2alignw} directive treats the fill
4904 pattern as a two byte word value. The @code{.p2alignl} directives treats the
4905 fill pattern as a four byte longword value. For example, @code{.p2alignw
4906 2,0x368d} will align to a multiple of 4. If it skips two bytes, they will be
4907 filled in with the value 0x368d (the exact placement of the bytes depends upon
4908 the endianness of the processor). If it skips 1 or 3 bytes, the fill value is
4913 @section @code{.previous}
4915 @cindex @code{previous} directive
4916 @cindex Section Stack
4917 This is one of the ELF section stack manipulation directives. The others are
4918 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
4919 @code{.pushsection} (@pxref{PushSection}), and @code{.popsection}
4920 (@pxref{PopSection}).
4922 This directive swaps the current section (and subsection) with most recently
4923 referenced section (and subsection) prior to this one. Multiple
4924 @code{.previous} directives in a row will flip between two sections (and their
4927 In terms of the section stack, this directive swaps the current section with
4928 the top section on the section stack.
4933 @section @code{.popsection}
4935 @cindex @code{popsection} directive
4936 @cindex Section Stack
4937 This is one of the ELF section stack manipulation directives. The others are
4938 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
4939 @code{.pushsection} (@pxref{PushSection}), and @code{.previous}
4942 This directive replaces the current section (and subsection) with the top
4943 section (and subsection) on the section stack. This section is popped off the
4948 @section @code{.print @var{string}}
4950 @cindex @code{print} directive
4951 @command{@value{AS}} will print @var{string} on the standard output during
4952 assembly. You must put @var{string} in double quotes.
4956 @section @code{.protected @var{names}}
4958 @cindex @code{protected} directive
4960 This one of the ELF visibility directives. The other two are
4961 @code{.hidden} (@pxref{Hidden}) and @code{.internal} (@pxref{Internal}).
4963 This directive overrides the named symbols default visibility (which is set by
4964 their binding: local, global or weak). The directive sets the visibility to
4965 @code{protected} which means that any references to the symbols from within the
4966 components that defines them must be resolved to the definition in that
4967 component, even if a definition in another component would normally preempt
4972 @section @code{.psize @var{lines} , @var{columns}}
4974 @cindex @code{psize} directive
4975 @cindex listing control: paper size
4976 @cindex paper size, for listings
4977 Use this directive to declare the number of lines---and, optionally, the
4978 number of columns---to use for each page, when generating listings.
4980 If you do not use @code{.psize}, listings use a default line-count
4981 of 60. You may omit the comma and @var{columns} specification; the
4982 default width is 200 columns.
4984 @command{@value{AS}} generates formfeeds whenever the specified number of
4985 lines is exceeded (or whenever you explicitly request one, using
4988 If you specify @var{lines} as @code{0}, no formfeeds are generated save
4989 those explicitly specified with @code{.eject}.
4992 @section @code{.purgem @var{name}}
4994 @cindex @code{purgem} directive
4995 Undefine the macro @var{name}, so that later uses of the string will not be
4996 expanded. @xref{Macro}.
5000 @section @code{.pushsection @var{name} , @var{subsection}}
5002 @cindex @code{pushsection} directive
5003 @cindex Section Stack
5004 This is one of the ELF section stack manipulation directives. The others are
5005 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
5006 @code{.popsection} (@pxref{PopSection}), and @code{.previous}
5009 This directive is a synonym for @code{.section}. It pushes the current section
5010 (and subsection) onto the top of the section stack, and then replaces the
5011 current section and subsection with @code{name} and @code{subsection}.
5015 @section @code{.quad @var{bignums}}
5017 @cindex @code{quad} directive
5018 @code{.quad} expects zero or more bignums, separated by commas. For
5019 each bignum, it emits
5021 an 8-byte integer. If the bignum won't fit in 8 bytes, it prints a
5022 warning message; and just takes the lowest order 8 bytes of the bignum.
5023 @cindex eight-byte integer
5024 @cindex integer, 8-byte
5026 The term ``quad'' comes from contexts in which a ``word'' is two bytes;
5027 hence @emph{quad}-word for 8 bytes.
5030 a 16-byte integer. If the bignum won't fit in 16 bytes, it prints a
5031 warning message; and just takes the lowest order 16 bytes of the bignum.
5032 @cindex sixteen-byte integer
5033 @cindex integer, 16-byte
5037 @section @code{.rept @var{count}}
5039 @cindex @code{rept} directive
5040 Repeat the sequence of lines between the @code{.rept} directive and the next
5041 @code{.endr} directive @var{count} times.
5043 For example, assembling
5051 is equivalent to assembling
5060 @section @code{.sbttl "@var{subheading}"}
5062 @cindex @code{sbttl} directive
5063 @cindex subtitles for listings
5064 @cindex listing control: subtitle
5065 Use @var{subheading} as the title (third line, immediately after the
5066 title line) when generating assembly listings.
5068 This directive affects subsequent pages, as well as the current page if
5069 it appears within ten lines of the top of a page.
5073 @section @code{.scl @var{class}}
5075 @cindex @code{scl} directive
5076 @cindex symbol storage class (COFF)
5077 @cindex COFF symbol storage class
5078 Set the storage-class value for a symbol. This directive may only be
5079 used inside a @code{.def}/@code{.endef} pair. Storage class may flag
5080 whether a symbol is static or external, or it may record further
5081 symbolic debugging information.
5084 The @samp{.scl} directive is primarily associated with COFF output; when
5085 configured to generate @code{b.out} output format, @command{@value{AS}}
5086 accepts this directive but ignores it.
5092 @section @code{.section @var{name}}
5094 @cindex named section
5095 Use the @code{.section} directive to assemble the following code into a section
5098 This directive is only supported for targets that actually support arbitrarily
5099 named sections; on @code{a.out} targets, for example, it is not accepted, even
5100 with a standard @code{a.out} section name.
5104 @c only print the extra heading if both COFF and ELF are set
5105 @subheading COFF Version
5108 @cindex @code{section} directive (COFF version)
5109 For COFF targets, the @code{.section} directive is used in one of the following
5113 .section @var{name}[, "@var{flags}"]
5114 .section @var{name}[, @var{subsegment}]
5117 If the optional argument is quoted, it is taken as flags to use for the
5118 section. Each flag is a single character. The following flags are recognized:
5121 bss section (uninitialized data)
5123 section is not loaded
5133 shared section (meaningful for PE targets)
5135 ignored. (For compatibility with the ELF version)
5138 If no flags are specified, the default flags depend upon the section name. If
5139 the section name is not recognized, the default will be for the section to be
5140 loaded and writable. Note the @code{n} and @code{w} flags remove attributes
5141 from the section, rather than adding them, so if they are used on their own it
5142 will be as if no flags had been specified at all.
5144 If the optional argument to the @code{.section} directive is not quoted, it is
5145 taken as a subsegment number (@pxref{Sub-Sections}).
5150 @c only print the extra heading if both COFF and ELF are set
5151 @subheading ELF Version
5154 @cindex Section Stack
5155 This is one of the ELF section stack manipulation directives. The others are
5156 @code{.subsection} (@pxref{SubSection}), @code{.pushsection}
5157 (@pxref{PushSection}), @code{.popsection} (@pxref{PopSection}), and
5158 @code{.previous} (@pxref{Previous}).
5160 @cindex @code{section} directive (ELF version)
5161 For ELF targets, the @code{.section} directive is used like this:
5164 .section @var{name} [, "@var{flags}"[, @@@var{type}[, @@@var{entsize}]]]
5167 The optional @var{flags} argument is a quoted string which may contain any
5168 combination of the following characters:
5171 section is allocatable
5175 section is executable
5177 section is mergeable
5179 section contains zero terminated strings
5182 The optional @var{type} argument may contain one of the following constants:
5185 section contains data
5187 section does not contain data (i.e., section only occupies space)
5190 Note on targets where the @code{@@} character is the start of a comment (eg
5191 ARM) then another character is used instead. For example the ARM port uses the
5194 If @var{flags} contains @code{M} flag, @var{type} argument must be specified
5195 as well as @var{entsize} argument. Sections with @code{M} flag but not
5196 @code{S} flag must contain fixed size constants, each @var{entsize} octets
5197 long. Sections with both @code{M} and @code{S} must contain zero terminated
5198 strings where each character is @var{entsize} bytes long. The linker may remove
5199 duplicates within sections with the same name, same entity size and same flags.
5201 If no flags are specified, the default flags depend upon the section name. If
5202 the section name is not recognized, the default will be for the section to have
5203 none of the above flags: it will not be allocated in memory, nor writable, nor
5204 executable. The section will contain data.
5206 For ELF targets, the assembler supports another type of @code{.section}
5207 directive for compatibility with the Solaris assembler:
5210 .section "@var{name}"[, @var{flags}...]
5213 Note that the section name is quoted. There may be a sequence of comma
5217 section is allocatable
5221 section is executable
5224 This directive replaces the current section and subsection. The replaced
5225 section and subsection are pushed onto the section stack. See the contents of
5226 the gas testsuite directory @code{gas/testsuite/gas/elf} for some examples of
5227 how this directive and the other section stack directives work.
5232 @section @code{.set @var{symbol}, @var{expression}}
5234 @cindex @code{set} directive
5235 @cindex symbol value, setting
5236 Set the value of @var{symbol} to @var{expression}. This
5237 changes @var{symbol}'s value and type to conform to
5238 @var{expression}. If @var{symbol} was flagged as external, it remains
5239 flagged (@pxref{Symbol Attributes}).
5241 You may @code{.set} a symbol many times in the same assembly.
5243 If you @code{.set} a global symbol, the value stored in the object
5244 file is the last value stored into it.
5247 The syntax for @code{set} on the HPPA is
5248 @samp{@var{symbol} .set @var{expression}}.
5252 @section @code{.short @var{expressions}}
5254 @cindex @code{short} directive
5256 @code{.short} is normally the same as @samp{.word}.
5257 @xref{Word,,@code{.word}}.
5259 In some configurations, however, @code{.short} and @code{.word} generate
5260 numbers of different lengths; @pxref{Machine Dependencies}.
5264 @code{.short} is the same as @samp{.word}. @xref{Word,,@code{.word}}.
5267 This expects zero or more @var{expressions}, and emits
5268 a 16 bit number for each.
5273 @section @code{.single @var{flonums}}
5275 @cindex @code{single} directive
5276 @cindex floating point numbers (single)
5277 This directive assembles zero or more flonums, separated by commas. It
5278 has the same effect as @code{.float}.
5280 The exact kind of floating point numbers emitted depends on how
5281 @command{@value{AS}} is configured. @xref{Machine Dependencies}.
5285 On the @value{TARGET} family, @code{.single} emits 32-bit floating point
5286 numbers in @sc{ieee} format.
5292 @section @code{.size}
5294 This directive is used to set the size associated with a symbol.
5298 @c only print the extra heading if both COFF and ELF are set
5299 @subheading COFF Version
5302 @cindex @code{size} directive (COFF version)
5303 For COFF targets, the @code{.size} directive is only permitted inside
5304 @code{.def}/@code{.endef} pairs. It is used like this:
5307 .size @var{expression}
5311 @samp{.size} is only meaningful when generating COFF format output; when
5312 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
5319 @c only print the extra heading if both COFF and ELF are set
5320 @subheading ELF Version
5323 @cindex @code{size} directive (ELF version)
5324 For ELF targets, the @code{.size} directive is used like this:
5327 .size @var{name} , @var{expression}
5330 This directive sets the size associated with a symbol @var{name}.
5331 The size in bytes is computed from @var{expression} which can make use of label
5332 arithmetic. This directive is typically used to set the size of function
5338 @section @code{.sleb128 @var{expressions}}
5340 @cindex @code{sleb128} directive
5341 @var{sleb128} stands for ``signed little endian base 128.'' This is a
5342 compact, variable length representation of numbers used by the DWARF
5343 symbolic debugging format. @xref{Uleb128,@code{.uleb128}}.
5345 @ifclear no-space-dir
5347 @section @code{.skip @var{size} , @var{fill}}
5349 @cindex @code{skip} directive
5350 @cindex filling memory
5351 This directive emits @var{size} bytes, each of value @var{fill}. Both
5352 @var{size} and @var{fill} are absolute expressions. If the comma and
5353 @var{fill} are omitted, @var{fill} is assumed to be zero. This is the same as
5357 @section @code{.space @var{size} , @var{fill}}
5359 @cindex @code{space} directive
5360 @cindex filling memory
5361 This directive emits @var{size} bytes, each of value @var{fill}. Both
5362 @var{size} and @var{fill} are absolute expressions. If the comma
5363 and @var{fill} are omitted, @var{fill} is assumed to be zero. This is the same
5368 @emph{Warning:} @code{.space} has a completely different meaning for HPPA
5369 targets; use @code{.block} as a substitute. See @cite{HP9000 Series 800
5370 Assembly Language Reference Manual} (HP 92432-90001) for the meaning of the
5371 @code{.space} directive. @xref{HPPA Directives,,HPPA Assembler Directives},
5380 @section @code{.space}
5381 @cindex @code{space} directive
5383 On the AMD 29K, this directive is ignored; it is accepted for
5384 compatibility with other AMD 29K assemblers.
5387 @emph{Warning:} In most versions of the @sc{gnu} assembler, the directive
5388 @code{.space} has the effect of @code{.block} @xref{Machine Dependencies}.
5394 @section @code{.stabd, .stabn, .stabs}
5396 @cindex symbolic debuggers, information for
5397 @cindex @code{stab@var{x}} directives
5398 There are three directives that begin @samp{.stab}.
5399 All emit symbols (@pxref{Symbols}), for use by symbolic debuggers.
5400 The symbols are not entered in the @command{@value{AS}} hash table: they
5401 cannot be referenced elsewhere in the source file.
5402 Up to five fields are required:
5406 This is the symbol's name. It may contain any character except
5407 @samp{\000}, so is more general than ordinary symbol names. Some
5408 debuggers used to code arbitrarily complex structures into symbol names
5412 An absolute expression. The symbol's type is set to the low 8 bits of
5413 this expression. Any bit pattern is permitted, but @code{@value{LD}}
5414 and debuggers choke on silly bit patterns.
5417 An absolute expression. The symbol's ``other'' attribute is set to the
5418 low 8 bits of this expression.
5421 An absolute expression. The symbol's descriptor is set to the low 16
5422 bits of this expression.
5425 An absolute expression which becomes the symbol's value.
5428 If a warning is detected while reading a @code{.stabd}, @code{.stabn},
5429 or @code{.stabs} statement, the symbol has probably already been created;
5430 you get a half-formed symbol in your object file. This is
5431 compatible with earlier assemblers!
5434 @cindex @code{stabd} directive
5435 @item .stabd @var{type} , @var{other} , @var{desc}
5437 The ``name'' of the symbol generated is not even an empty string.
5438 It is a null pointer, for compatibility. Older assemblers used a
5439 null pointer so they didn't waste space in object files with empty
5442 The symbol's value is set to the location counter,
5443 relocatably. When your program is linked, the value of this symbol
5444 is the address of the location counter when the @code{.stabd} was
5447 @cindex @code{stabn} directive
5448 @item .stabn @var{type} , @var{other} , @var{desc} , @var{value}
5449 The name of the symbol is set to the empty string @code{""}.
5451 @cindex @code{stabs} directive
5452 @item .stabs @var{string} , @var{type} , @var{other} , @var{desc} , @var{value}
5453 All five fields are specified.
5459 @section @code{.string} "@var{str}"
5461 @cindex string, copying to object file
5462 @cindex @code{string} directive
5464 Copy the characters in @var{str} to the object file. You may specify more than
5465 one string to copy, separated by commas. Unless otherwise specified for a
5466 particular machine, the assembler marks the end of each string with a 0 byte.
5467 You can use any of the escape sequences described in @ref{Strings,,Strings}.
5470 @section @code{.struct @var{expression}}
5472 @cindex @code{struct} directive
5473 Switch to the absolute section, and set the section offset to @var{expression},
5474 which must be an absolute expression. You might use this as follows:
5483 This would define the symbol @code{field1} to have the value 0, the symbol
5484 @code{field2} to have the value 4, and the symbol @code{field3} to have the
5485 value 8. Assembly would be left in the absolute section, and you would need to
5486 use a @code{.section} directive of some sort to change to some other section
5487 before further assembly.
5491 @section @code{.subsection @var{name}}
5493 @cindex @code{subsection} directive
5494 @cindex Section Stack
5495 This is one of the ELF section stack manipulation directives. The others are
5496 @code{.section} (@pxref{Section}), @code{.pushsection} (@pxref{PushSection}),
5497 @code{.popsection} (@pxref{PopSection}), and @code{.previous}
5500 This directive replaces the current subsection with @code{name}. The current
5501 section is not changed. The replaced subsection is put onto the section stack
5502 in place of the then current top of stack subsection.
5507 @section @code{.symver}
5508 @cindex @code{symver} directive
5509 @cindex symbol versioning
5510 @cindex versions of symbols
5511 Use the @code{.symver} directive to bind symbols to specific version nodes
5512 within a source file. This is only supported on ELF platforms, and is
5513 typically used when assembling files to be linked into a shared library.
5514 There are cases where it may make sense to use this in objects to be bound
5515 into an application itself so as to override a versioned symbol from a
5518 For ELF targets, the @code{.symver} directive can be used like this:
5520 .symver @var{name}, @var{name2@@nodename}
5522 If the symbol @var{name} is defined within the file
5523 being assembled, the @code{.symver} directive effectively creates a symbol
5524 alias with the name @var{name2@@nodename}, and in fact the main reason that we
5525 just don't try and create a regular alias is that the @var{@@} character isn't
5526 permitted in symbol names. The @var{name2} part of the name is the actual name
5527 of the symbol by which it will be externally referenced. The name @var{name}
5528 itself is merely a name of convenience that is used so that it is possible to
5529 have definitions for multiple versions of a function within a single source
5530 file, and so that the compiler can unambiguously know which version of a
5531 function is being mentioned. The @var{nodename} portion of the alias should be
5532 the name of a node specified in the version script supplied to the linker when
5533 building a shared library. If you are attempting to override a versioned
5534 symbol from a shared library, then @var{nodename} should correspond to the
5535 nodename of the symbol you are trying to override.
5537 If the symbol @var{name} is not defined within the file being assembled, all
5538 references to @var{name} will be changed to @var{name2@@nodename}. If no
5539 reference to @var{name} is made, @var{name2@@nodename} will be removed from the
5542 Another usage of the @code{.symver} directive is:
5544 .symver @var{name}, @var{name2@@@@nodename}
5546 In this case, the symbol @var{name} must exist and be defined within
5547 the file being assembled. It is similar to @var{name2@@nodename}. The
5548 difference is @var{name2@@@@nodename} will also be used to resolve
5549 references to @var{name2} by the linker.
5551 The third usage of the @code{.symver} directive is:
5553 .symver @var{name}, @var{name2@@@@@@nodename}
5555 When @var{name} is not defined within the
5556 file being assembled, it is treated as @var{name2@@nodename}. When
5557 @var{name} is defined within the file being assembled, the symbol
5558 name, @var{name}, will be changed to @var{name2@@@@nodename}.
5563 @section @code{.tag @var{structname}}
5565 @cindex COFF structure debugging
5566 @cindex structure debugging, COFF
5567 @cindex @code{tag} directive
5568 This directive is generated by compilers to include auxiliary debugging
5569 information in the symbol table. It is only permitted inside
5570 @code{.def}/@code{.endef} pairs. Tags are used to link structure
5571 definitions in the symbol table with instances of those structures.
5574 @samp{.tag} is only used when generating COFF format output; when
5575 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
5581 @section @code{.text @var{subsection}}
5583 @cindex @code{text} directive
5584 Tells @command{@value{AS}} to assemble the following statements onto the end of
5585 the text subsection numbered @var{subsection}, which is an absolute
5586 expression. If @var{subsection} is omitted, subsection number zero
5590 @section @code{.title "@var{heading}"}
5592 @cindex @code{title} directive
5593 @cindex listing control: title line
5594 Use @var{heading} as the title (second line, immediately after the
5595 source file name and pagenumber) when generating assembly listings.
5597 This directive affects subsequent pages, as well as the current page if
5598 it appears within ten lines of the top of a page.
5602 @section @code{.type}
5604 This directive is used to set the type of a symbol.
5608 @c only print the extra heading if both COFF and ELF are set
5609 @subheading COFF Version
5612 @cindex COFF symbol type
5613 @cindex symbol type, COFF
5614 @cindex @code{type} directive (COFF version)
5615 For COFF targets, this directive is permitted only within
5616 @code{.def}/@code{.endef} pairs. It is used like this:
5622 This records the integer @var{int} as the type attribute of a symbol table
5626 @samp{.type} is associated only with COFF format output; when
5627 @command{@value{AS}} is configured for @code{b.out} output, it accepts this
5628 directive but ignores it.
5634 @c only print the extra heading if both COFF and ELF are set
5635 @subheading ELF Version
5638 @cindex ELF symbol type
5639 @cindex symbol type, ELF
5640 @cindex @code{type} directive (ELF version)
5641 For ELF targets, the @code{.type} directive is used like this:
5644 .type @var{name} , @var{type description}
5647 This sets the type of symbol @var{name} to be either a
5648 function symbol or an object symbol. There are five different syntaxes
5649 supported for the @var{type description} field, in order to provide
5650 compatibility with various other assemblers. The syntaxes supported are:
5653 .type <name>,#function
5654 .type <name>,#object
5656 .type <name>,@@function
5657 .type <name>,@@object
5659 .type <name>,%function
5660 .type <name>,%object
5662 .type <name>,"function"
5663 .type <name>,"object"
5665 .type <name> STT_FUNCTION
5666 .type <name> STT_OBJECT
5672 @section @code{.uleb128 @var{expressions}}
5674 @cindex @code{uleb128} directive
5675 @var{uleb128} stands for ``unsigned little endian base 128.'' This is a
5676 compact, variable length representation of numbers used by the DWARF
5677 symbolic debugging format. @xref{Sleb128,@code{.sleb128}}.
5681 @section @code{.val @var{addr}}
5683 @cindex @code{val} directive
5684 @cindex COFF value attribute
5685 @cindex value attribute, COFF
5686 This directive, permitted only within @code{.def}/@code{.endef} pairs,
5687 records the address @var{addr} as the value attribute of a symbol table
5691 @samp{.val} is used only for COFF output; when @command{@value{AS}} is
5692 configured for @code{b.out}, it accepts this directive but ignores it.
5698 @section @code{.version "@var{string}"}
5700 @cindex @code{version} directive
5701 This directive creates a @code{.note} section and places into it an ELF
5702 formatted note of type NT_VERSION. The note's name is set to @code{string}.
5707 @section @code{.vtable_entry @var{table}, @var{offset}}
5709 @cindex @code{vtable_entry}
5710 This directive finds or creates a symbol @code{table} and creates a
5711 @code{VTABLE_ENTRY} relocation for it with an addend of @code{offset}.
5714 @section @code{.vtable_inherit @var{child}, @var{parent}}
5716 @cindex @code{vtable_inherit}
5717 This directive finds the symbol @code{child} and finds or creates the symbol
5718 @code{parent} and then creates a @code{VTABLE_INHERIT} relocation for the
5719 parent whose addend is the value of the child symbol. As a special case the
5720 parent name of @code{0} is treated as refering the @code{*ABS*} section.
5725 @section @code{.weak @var{names}}
5727 @cindex @code{weak} directive
5728 This directive sets the weak attribute on the comma separated list of symbol
5729 @code{names}. If the symbols do not already exist, they will be created.
5733 @section @code{.word @var{expressions}}
5735 @cindex @code{word} directive
5736 This directive expects zero or more @var{expressions}, of any section,
5737 separated by commas.
5740 For each expression, @command{@value{AS}} emits a 32-bit number.
5743 For each expression, @command{@value{AS}} emits a 16-bit number.
5748 The size of the number emitted, and its byte order,
5749 depend on what target computer the assembly is for.
5752 @c on amd29k, i960, sparc the "special treatment to support compilers" doesn't
5753 @c happen---32-bit addressability, period; no long/short jumps.
5754 @ifset DIFF-TBL-KLUGE
5755 @cindex difference tables altered
5756 @cindex altered difference tables
5758 @emph{Warning: Special Treatment to support Compilers}
5762 Machines with a 32-bit address space, but that do less than 32-bit
5763 addressing, require the following special treatment. If the machine of
5764 interest to you does 32-bit addressing (or doesn't require it;
5765 @pxref{Machine Dependencies}), you can ignore this issue.
5768 In order to assemble compiler output into something that works,
5769 @command{@value{AS}} occasionally does strange things to @samp{.word} directives.
5770 Directives of the form @samp{.word sym1-sym2} are often emitted by
5771 compilers as part of jump tables. Therefore, when @command{@value{AS}} assembles a
5772 directive of the form @samp{.word sym1-sym2}, and the difference between
5773 @code{sym1} and @code{sym2} does not fit in 16 bits, @command{@value{AS}}
5774 creates a @dfn{secondary jump table}, immediately before the next label.
5775 This secondary jump table is preceded by a short-jump to the
5776 first byte after the secondary table. This short-jump prevents the flow
5777 of control from accidentally falling into the new table. Inside the
5778 table is a long-jump to @code{sym2}. The original @samp{.word}
5779 contains @code{sym1} minus the address of the long-jump to
5782 If there were several occurrences of @samp{.word sym1-sym2} before the
5783 secondary jump table, all of them are adjusted. If there was a
5784 @samp{.word sym3-sym4}, that also did not fit in sixteen bits, a
5785 long-jump to @code{sym4} is included in the secondary jump table,
5786 and the @code{.word} directives are adjusted to contain @code{sym3}
5787 minus the address of the long-jump to @code{sym4}; and so on, for as many
5788 entries in the original jump table as necessary.
5791 @emph{This feature may be disabled by compiling @command{@value{AS}} with the
5792 @samp{-DWORKING_DOT_WORD} option.} This feature is likely to confuse
5793 assembly language programmers.
5796 @c end DIFF-TBL-KLUGE
5799 @section Deprecated Directives
5801 @cindex deprecated directives
5802 @cindex obsolescent directives
5803 One day these directives won't work.
5804 They are included for compatibility with older assemblers.
5811 @node Machine Dependencies
5812 @chapter Machine Dependent Features
5814 @cindex machine dependencies
5815 The machine instruction sets are (almost by definition) different on
5816 each machine where @command{@value{AS}} runs. Floating point representations
5817 vary as well, and @command{@value{AS}} often supports a few additional
5818 directives or command-line options for compatibility with other
5819 assemblers on a particular platform. Finally, some versions of
5820 @command{@value{AS}} support special pseudo-instructions for branch
5823 This chapter discusses most of these differences, though it does not
5824 include details on any machine's instruction set. For details on that
5825 subject, see the hardware manufacturer's manual.
5829 * AMD29K-Dependent:: AMD 29K Dependent Features
5832 * Alpha-Dependent:: Alpha Dependent Features
5835 * ARC-Dependent:: ARC Dependent Features
5838 * ARM-Dependent:: ARM Dependent Features
5841 * CRIS-Dependent:: CRIS Dependent Features
5844 * D10V-Dependent:: D10V Dependent Features
5847 * D30V-Dependent:: D30V Dependent Features
5850 * H8/300-Dependent:: Renesas H8/300 Dependent Features
5853 * H8/500-Dependent:: Renesas H8/500 Dependent Features
5856 * HPPA-Dependent:: HPPA Dependent Features
5859 * ESA/390-Dependent:: IBM ESA/390 Dependent Features
5862 * i386-Dependent:: Intel 80386 and AMD x86-64 Dependent Features
5865 * i860-Dependent:: Intel 80860 Dependent Features
5868 * i960-Dependent:: Intel 80960 Dependent Features
5871 * IP2K-Dependent:: IP2K Dependent Features
5874 * M32R-Dependent:: M32R Dependent Features
5877 * M68K-Dependent:: M680x0 Dependent Features
5880 * M68HC11-Dependent:: M68HC11 and 68HC12 Dependent Features
5883 * M88K-Dependent:: M880x0 Dependent Features
5886 * MIPS-Dependent:: MIPS Dependent Features
5889 * MMIX-Dependent:: MMIX Dependent Features
5892 * MSP430-Dependent:: MSP430 Dependent Features
5895 * SH-Dependent:: Renesas SH Dependent Features
5896 * SH64-Dependent:: Renesas SH64 Dependent Features
5899 * PDP-11-Dependent:: PDP-11 Dependent Features
5902 * PJ-Dependent:: picoJava Dependent Features
5905 * PPC-Dependent:: PowerPC Dependent Features
5908 * Sparc-Dependent:: SPARC Dependent Features
5911 * TIC54X-Dependent:: TI TMS320C54x Dependent Features
5914 * V850-Dependent:: V850 Dependent Features
5917 * Xtensa-Dependent:: Xtensa Dependent Features
5920 * Z8000-Dependent:: Z8000 Dependent Features
5923 * Vax-Dependent:: VAX Dependent Features
5930 @c The following major nodes are *sections* in the GENERIC version, *chapters*
5931 @c in single-cpu versions. This is mainly achieved by @lowersections. There is a
5932 @c peculiarity: to preserve cross-references, there must be a node called
5933 @c "Machine Dependencies". Hence the conditional nodenames in each
5934 @c major node below. Node defaulting in makeinfo requires adjacency of
5935 @c node and sectioning commands; hence the repetition of @chapter BLAH
5936 @c in both conditional blocks.
5939 @include c-a29k.texi
5943 @include c-alpha.texi
5955 @include c-cris.texi
5960 @node Machine Dependencies
5961 @chapter Machine Dependent Features
5963 The machine instruction sets are different on each Renesas chip family,
5964 and there are also some syntax differences among the families. This
5965 chapter describes the specific @command{@value{AS}} features for each
5969 * H8/300-Dependent:: Renesas H8/300 Dependent Features
5970 * H8/500-Dependent:: Renesas H8/500 Dependent Features
5971 * SH-Dependent:: Renesas SH Dependent Features
5978 @include c-d10v.texi
5982 @include c-d30v.texi
5986 @include c-h8300.texi
5990 @include c-h8500.texi
5994 @include c-hppa.texi
5998 @include c-i370.texi
6002 @include c-i386.texi
6006 @include c-i860.texi
6010 @include c-i960.texi
6014 @include c-ia64.texi
6018 @include c-ip2k.texi
6022 @include c-m32r.texi
6026 @include c-m68k.texi
6030 @include c-m68hc11.texi
6034 @include c-m88k.texi
6038 @include c-mips.texi
6042 @include c-mmix.texi
6046 @include c-msp430.texi
6050 @include c-ns32k.texi
6054 @include c-pdp11.texi
6067 @include c-sh64.texi
6071 @include c-sparc.texi
6075 @include c-tic54x.texi
6087 @include c-v850.texi
6091 @include c-xtensa.texi
6095 @c reverse effect of @down at top of generic Machine-Dep chapter
6099 @node Reporting Bugs
6100 @chapter Reporting Bugs
6101 @cindex bugs in assembler
6102 @cindex reporting bugs in assembler
6104 Your bug reports play an essential role in making @command{@value{AS}} reliable.
6106 Reporting a bug may help you by bringing a solution to your problem, or it may
6107 not. But in any case the principal function of a bug report is to help the
6108 entire community by making the next version of @command{@value{AS}} work better.
6109 Bug reports are your contribution to the maintenance of @command{@value{AS}}.
6111 In order for a bug report to serve its purpose, you must include the
6112 information that enables us to fix the bug.
6115 * Bug Criteria:: Have you found a bug?
6116 * Bug Reporting:: How to report bugs
6120 @section Have You Found a Bug?
6121 @cindex bug criteria
6123 If you are not sure whether you have found a bug, here are some guidelines:
6126 @cindex fatal signal
6127 @cindex assembler crash
6128 @cindex crash of assembler
6130 If the assembler gets a fatal signal, for any input whatever, that is a
6131 @command{@value{AS}} bug. Reliable assemblers never crash.
6133 @cindex error on valid input
6135 If @command{@value{AS}} produces an error message for valid input, that is a bug.
6137 @cindex invalid input
6139 If @command{@value{AS}} does not produce an error message for invalid input, that
6140 is a bug. However, you should note that your idea of ``invalid input'' might
6141 be our idea of ``an extension'' or ``support for traditional practice''.
6144 If you are an experienced user of assemblers, your suggestions for improvement
6145 of @command{@value{AS}} are welcome in any case.
6149 @section How to Report Bugs
6151 @cindex assembler bugs, reporting
6153 A number of companies and individuals offer support for @sc{gnu} products. If
6154 you obtained @command{@value{AS}} from a support organization, we recommend you
6155 contact that organization first.
6157 You can find contact information for many support companies and
6158 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
6161 In any event, we also recommend that you send bug reports for @command{@value{AS}}
6162 to @samp{bug-binutils@@gnu.org}.
6164 The fundamental principle of reporting bugs usefully is this:
6165 @strong{report all the facts}. If you are not sure whether to state a
6166 fact or leave it out, state it!
6168 Often people omit facts because they think they know what causes the problem
6169 and assume that some details do not matter. Thus, you might assume that the
6170 name of a symbol you use in an example does not matter. Well, probably it does
6171 not, but one cannot be sure. Perhaps the bug is a stray memory reference which
6172 happens to fetch from the location where that name is stored in memory;
6173 perhaps, if the name were different, the contents of that location would fool
6174 the assembler into doing the right thing despite the bug. Play it safe and
6175 give a specific, complete example. That is the easiest thing for you to do,
6176 and the most helpful.
6178 Keep in mind that the purpose of a bug report is to enable us to fix the bug if
6179 it is new to us. Therefore, always write your bug reports on the assumption
6180 that the bug has not been reported previously.
6182 Sometimes people give a few sketchy facts and ask, ``Does this ring a
6183 bell?'' This cannot help us fix a bug, so it is basically useless. We
6184 respond by asking for enough details to enable us to investigate.
6185 You might as well expedite matters by sending them to begin with.
6187 To enable us to fix the bug, you should include all these things:
6191 The version of @command{@value{AS}}. @command{@value{AS}} announces it if you start
6192 it with the @samp{--version} argument.
6194 Without this, we will not know whether there is any point in looking for
6195 the bug in the current version of @command{@value{AS}}.
6198 Any patches you may have applied to the @command{@value{AS}} source.
6201 The type of machine you are using, and the operating system name and
6205 What compiler (and its version) was used to compile @command{@value{AS}}---e.g.
6209 The command arguments you gave the assembler to assemble your example and
6210 observe the bug. To guarantee you will not omit something important, list them
6211 all. A copy of the Makefile (or the output from make) is sufficient.
6213 If we were to try to guess the arguments, we would probably guess wrong
6214 and then we might not encounter the bug.
6217 A complete input file that will reproduce the bug. If the bug is observed when
6218 the assembler is invoked via a compiler, send the assembler source, not the
6219 high level language source. Most compilers will produce the assembler source
6220 when run with the @samp{-S} option. If you are using @code{@value{GCC}}, use
6221 the options @samp{-v --save-temps}; this will save the assembler source in a
6222 file with an extension of @file{.s}, and also show you exactly how
6223 @command{@value{AS}} is being run.
6226 A description of what behavior you observe that you believe is
6227 incorrect. For example, ``It gets a fatal signal.''
6229 Of course, if the bug is that @command{@value{AS}} gets a fatal signal, then we
6230 will certainly notice it. But if the bug is incorrect output, we might not
6231 notice unless it is glaringly wrong. You might as well not give us a chance to
6234 Even if the problem you experience is a fatal signal, you should still say so
6235 explicitly. Suppose something strange is going on, such as, your copy of
6236 @command{@value{AS}} is out of synch, or you have encountered a bug in the C
6237 library on your system. (This has happened!) Your copy might crash and ours
6238 would not. If you told us to expect a crash, then when ours fails to crash, we
6239 would know that the bug was not happening for us. If you had not told us to
6240 expect a crash, then we would not be able to draw any conclusion from our
6244 If you wish to suggest changes to the @command{@value{AS}} source, send us context
6245 diffs, as generated by @code{diff} with the @samp{-u}, @samp{-c}, or @samp{-p}
6246 option. Always send diffs from the old file to the new file. If you even
6247 discuss something in the @command{@value{AS}} source, refer to it by context, not
6250 The line numbers in our development sources will not match those in your
6251 sources. Your line numbers would convey no useful information to us.
6254 Here are some things that are not necessary:
6258 A description of the envelope of the bug.
6260 Often people who encounter a bug spend a lot of time investigating
6261 which changes to the input file will make the bug go away and which
6262 changes will not affect it.
6264 This is often time consuming and not very useful, because the way we
6265 will find the bug is by running a single example under the debugger
6266 with breakpoints, not by pure deduction from a series of examples.
6267 We recommend that you save your time for something else.
6269 Of course, if you can find a simpler example to report @emph{instead}
6270 of the original one, that is a convenience for us. Errors in the
6271 output will be easier to spot, running under the debugger will take
6272 less time, and so on.
6274 However, simplification is not vital; if you do not want to do this,
6275 report the bug anyway and send us the entire test case you used.
6278 A patch for the bug.
6280 A patch for the bug does help us if it is a good one. But do not omit
6281 the necessary information, such as the test case, on the assumption that
6282 a patch is all we need. We might see problems with your patch and decide
6283 to fix the problem another way, or we might not understand it at all.
6285 Sometimes with a program as complicated as @command{@value{AS}} it is very hard to
6286 construct an example that will make the program follow a certain path through
6287 the code. If you do not send us the example, we will not be able to construct
6288 one, so we will not be able to verify that the bug is fixed.
6290 And if we cannot understand what bug you are trying to fix, or why your
6291 patch should be an improvement, we will not install it. A test case will
6292 help us to understand.
6295 A guess about what the bug is or what it depends on.
6297 Such guesses are usually wrong. Even we cannot guess right about such
6298 things without first using the debugger to find the facts.
6301 @node Acknowledgements
6302 @chapter Acknowledgements
6304 If you have contributed to @command{@value{AS}} and your name isn't listed here,
6305 it is not meant as a slight. We just don't know about it. Send mail to the
6306 maintainer, and we'll correct the situation. Currently
6308 the maintainer is Ken Raeburn (email address @code{raeburn@@cygnus.com}).
6310 Dean Elsner wrote the original @sc{gnu} assembler for the VAX.@footnote{Any
6313 Jay Fenlason maintained GAS for a while, adding support for GDB-specific debug
6314 information and the 68k series machines, most of the preprocessing pass, and
6315 extensive changes in @file{messages.c}, @file{input-file.c}, @file{write.c}.
6317 K. Richard Pixley maintained GAS for a while, adding various enhancements and
6318 many bug fixes, including merging support for several processors, breaking GAS
6319 up to handle multiple object file format back ends (including heavy rewrite,
6320 testing, an integration of the coff and b.out back ends), adding configuration
6321 including heavy testing and verification of cross assemblers and file splits
6322 and renaming, converted GAS to strictly ANSI C including full prototypes, added
6323 support for m680[34]0 and cpu32, did considerable work on i960 including a COFF
6324 port (including considerable amounts of reverse engineering), a SPARC opcode
6325 file rewrite, DECstation, rs6000, and hp300hpux host ports, updated ``know''
6326 assertions and made them work, much other reorganization, cleanup, and lint.
6328 Ken Raeburn wrote the high-level BFD interface code to replace most of the code
6329 in format-specific I/O modules.
6331 The original VMS support was contributed by David L. Kashtan. Eric Youngdale
6332 has done much work with it since.
6334 The Intel 80386 machine description was written by Eliot Dresselhaus.
6336 Minh Tran-Le at IntelliCorp contributed some AIX 386 support.
6338 The Motorola 88k machine description was contributed by Devon Bowen of Buffalo
6339 University and Torbjorn Granlund of the Swedish Institute of Computer Science.
6341 Keith Knowles at the Open Software Foundation wrote the original MIPS back end
6342 (@file{tc-mips.c}, @file{tc-mips.h}), and contributed Rose format support
6343 (which hasn't been merged in yet). Ralph Campbell worked with the MIPS code to
6344 support a.out format.
6346 Support for the Zilog Z8k and Renesas H8/300 and H8/500 processors (tc-z8k,
6347 tc-h8300, tc-h8500), and IEEE 695 object file format (obj-ieee), was written by
6348 Steve Chamberlain of Cygnus Support. Steve also modified the COFF back end to
6349 use BFD for some low-level operations, for use with the H8/300 and AMD 29k
6352 John Gilmore built the AMD 29000 support, added @code{.include} support, and
6353 simplified the configuration of which versions accept which directives. He
6354 updated the 68k machine description so that Motorola's opcodes always produced
6355 fixed-size instructions (e.g., @code{jsr}), while synthetic instructions
6356 remained shrinkable (@code{jbsr}). John fixed many bugs, including true tested
6357 cross-compilation support, and one bug in relaxation that took a week and
6358 required the proverbial one-bit fix.
6360 Ian Lance Taylor of Cygnus Support merged the Motorola and MIT syntax for the
6361 68k, completed support for some COFF targets (68k, i386 SVR3, and SCO Unix),
6362 added support for MIPS ECOFF and ELF targets, wrote the initial RS/6000 and
6363 PowerPC assembler, and made a few other minor patches.
6365 Steve Chamberlain made @command{@value{AS}} able to generate listings.
6367 Hewlett-Packard contributed support for the HP9000/300.
6369 Jeff Law wrote GAS and BFD support for the native HPPA object format (SOM)
6370 along with a fairly extensive HPPA testsuite (for both SOM and ELF object
6371 formats). This work was supported by both the Center for Software Science at
6372 the University of Utah and Cygnus Support.
6374 Support for ELF format files has been worked on by Mark Eichin of Cygnus
6375 Support (original, incomplete implementation for SPARC), Pete Hoogenboom and
6376 Jeff Law at the University of Utah (HPPA mainly), Michael Meissner of the Open
6377 Software Foundation (i386 mainly), and Ken Raeburn of Cygnus Support (sparc,
6378 and some initial 64-bit support).
6380 Linas Vepstas added GAS support for the ESA/390 ``IBM 370'' architecture.
6382 Richard Henderson rewrote the Alpha assembler. Klaus Kaempf wrote GAS and BFD
6383 support for openVMS/Alpha.
6385 Timothy Wall, Michael Hayes, and Greg Smart contributed to the various tic*
6388 David Heine, Sterling Augustine, Bob Wilson and John Ruttenberg from Tensilica,
6389 Inc. added support for Xtensa processors.
6391 Several engineers at Cygnus Support have also provided many small bug fixes and
6392 configuration enhancements.
6394 Many others have contributed large or small bugfixes and enhancements. If
6395 you have contributed significant work and are not mentioned on this list, and
6396 want to be, let us know. Some of the history has been lost; we are not
6397 intentionally leaving anyone out.
projects / deliverable / binutils-gdb.git / blob