1 \input texinfo @c -*-Texinfo-*-
2 @c Copyright 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999, 2000,
3 @c 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012
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:
24 @include asconfig.texi
29 @c common OR combinations of conditions
55 @set abnormal-separator
59 @settitle Using @value{AS}
62 @settitle Using @value{AS} (@value{TARGET})
64 @setchapternewpage odd
69 @c WARE! Some of the machine-dependent sections contain tables of machine
70 @c instructions. Except in multi-column format, these tables look silly.
71 @c Unfortunately, Texinfo doesn't have a general-purpose multi-col format, so
72 @c the multi-col format is faked within @example sections.
74 @c Again unfortunately, the natural size that fits on a page, for these tables,
75 @c is different depending on whether or not smallbook is turned on.
76 @c This matters, because of order: text flow switches columns at each page
79 @c The format faked in this source works reasonably well for smallbook,
80 @c not well for the default large-page format. This manual expects that if you
81 @c turn on @smallbook, you will also uncomment the "@set SMALL" to enable the
82 @c tables in question. You can turn on one without the other at your
83 @c discretion, of course.
86 @c the insn tables look just as silly in info files regardless of smallbook,
87 @c might as well show 'em anyways.
91 @dircategory Software development
93 * As: (as). The GNU assembler.
94 * Gas: (as). The GNU assembler.
102 This file documents the GNU Assembler "@value{AS}".
104 @c man begin COPYRIGHT
105 Copyright @copyright{} 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999,
106 2000, 2001, 2002, 2006, 2007, 2008, 2009, 2010, 2011 Free Software Foundation,
109 Permission is granted to copy, distribute and/or modify this document
110 under the terms of the GNU Free Documentation License, Version 1.3
111 or any later version published by the Free Software Foundation;
112 with no Invariant Sections, with no Front-Cover Texts, and with no
113 Back-Cover Texts. A copy of the license is included in the
114 section entitled ``GNU Free Documentation License''.
120 @title Using @value{AS}
121 @subtitle The @sc{gnu} Assembler
123 @subtitle for the @value{TARGET} family
125 @ifset VERSION_PACKAGE
127 @subtitle @value{VERSION_PACKAGE}
130 @subtitle Version @value{VERSION}
133 The Free Software Foundation Inc.@: thanks The Nice Computer
134 Company of Australia for loaning Dean Elsner to write the
135 first (Vax) version of @command{as} for Project @sc{gnu}.
136 The proprietors, management and staff of TNCCA thank FSF for
137 distracting the boss while they got some work
140 @author Dean Elsner, Jay Fenlason & friends
144 \hfill {\it Using {\tt @value{AS}}}\par
145 \hfill Edited by Cygnus Support\par
147 %"boxit" macro for figures:
148 %Modified from Knuth's ``boxit'' macro from TeXbook (answer to exercise 21.3)
149 \gdef\boxit#1#2{\vbox{\hrule\hbox{\vrule\kern3pt
150 \vbox{\parindent=0pt\parskip=0pt\hsize=#1\kern3pt\strut\hfil
151 #2\hfil\strut\kern3pt}\kern3pt\vrule}\hrule}}%box with visible outline
152 \gdef\ibox#1#2{\hbox to #1{#2\hfil}\kern8pt}% invisible box
155 @vskip 0pt plus 1filll
156 Copyright @copyright{} 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999,
157 2000, 2001, 2002, 2006, 2007, 2008, 2009, 2010, 2011 Free Software Foundation,
160 Permission is granted to copy, distribute and/or modify this document
161 under the terms of the GNU Free Documentation License, Version 1.3
162 or any later version published by the Free Software Foundation;
163 with no Invariant Sections, with no Front-Cover Texts, and with no
164 Back-Cover Texts. A copy of the license is included in the
165 section entitled ``GNU Free Documentation License''.
172 @top Using @value{AS}
174 This file is a user guide to the @sc{gnu} assembler @command{@value{AS}}
175 @ifset VERSION_PACKAGE
176 @value{VERSION_PACKAGE}
178 version @value{VERSION}.
180 This version of the file describes @command{@value{AS}} configured to generate
181 code for @value{TARGET} architectures.
184 This document is distributed under the terms of the GNU Free
185 Documentation License. A copy of the license is included in the
186 section entitled ``GNU Free Documentation License''.
189 * Overview:: Overview
190 * Invoking:: Command-Line Options
192 * Sections:: Sections and Relocation
194 * Expressions:: Expressions
195 * Pseudo Ops:: Assembler Directives
197 * Object Attributes:: Object Attributes
199 * Machine Dependencies:: Machine Dependent Features
200 * Reporting Bugs:: Reporting Bugs
201 * Acknowledgements:: Who Did What
202 * GNU Free Documentation License:: GNU Free Documentation License
203 * AS Index:: AS Index
210 This manual is a user guide to the @sc{gnu} assembler @command{@value{AS}}.
212 This version of the manual describes @command{@value{AS}} configured to generate
213 code for @value{TARGET} architectures.
217 @cindex invocation summary
218 @cindex option summary
219 @cindex summary of options
220 Here is a brief summary of how to invoke @command{@value{AS}}. For details,
221 see @ref{Invoking,,Command-Line Options}.
223 @c man title AS the portable GNU assembler.
227 gcc(1), ld(1), and the Info entries for @file{binutils} and @file{ld}.
231 @c We don't use deffn and friends for the following because they seem
232 @c to be limited to one line for the header.
234 @c man begin SYNOPSIS
235 @value{AS} [@b{-a}[@b{cdghlns}][=@var{file}]] [@b{--alternate}] [@b{-D}]
236 [@b{--compress-debug-sections}] [@b{--nocompress-debug-sections}]
237 [@b{--debug-prefix-map} @var{old}=@var{new}]
238 [@b{--defsym} @var{sym}=@var{val}] [@b{-f}] [@b{-g}] [@b{--gstabs}]
239 [@b{--gstabs+}] [@b{--gdwarf-2}] [@b{--help}] [@b{-I} @var{dir}] [@b{-J}]
240 [@b{-K}] [@b{-L}] [@b{--listing-lhs-width}=@var{NUM}]
241 [@b{--listing-lhs-width2}=@var{NUM}] [@b{--listing-rhs-width}=@var{NUM}]
242 [@b{--listing-cont-lines}=@var{NUM}] [@b{--keep-locals}] [@b{-o}
243 @var{objfile}] [@b{-R}] [@b{--reduce-memory-overheads}] [@b{--statistics}]
244 [@b{-v}] [@b{-version}] [@b{--version}] [@b{-W}] [@b{--warn}]
245 [@b{--fatal-warnings}] [@b{-w}] [@b{-x}] [@b{-Z}] [@b{@@@var{FILE}}]
246 [@b{--size-check=[error|warning]}]
247 [@b{--target-help}] [@var{target-options}]
248 [@b{--}|@var{files} @dots{}]
250 @c Target dependent options are listed below. Keep the list sorted.
251 @c Add an empty line for separation.
254 @emph{Target Alpha options:}
256 [@b{-mdebug} | @b{-no-mdebug}]
257 [@b{-replace} | @b{-noreplace}]
258 [@b{-relax}] [@b{-g}] [@b{-G@var{size}}]
259 [@b{-F}] [@b{-32addr}]
263 @emph{Target ARC options:}
269 @emph{Target ARM options:}
270 @c Don't document the deprecated options
271 [@b{-mcpu}=@var{processor}[+@var{extension}@dots{}]]
272 [@b{-march}=@var{architecture}[+@var{extension}@dots{}]]
273 [@b{-mfpu}=@var{floating-point-format}]
274 [@b{-mfloat-abi}=@var{abi}]
275 [@b{-meabi}=@var{ver}]
278 [@b{-mapcs-32}|@b{-mapcs-26}|@b{-mapcs-float}|
279 @b{-mapcs-reentrant}]
280 [@b{-mthumb-interwork}] [@b{-k}]
284 @emph{Target Blackfin options:}
285 [@b{-mcpu}=@var{processor}[-@var{sirevision}]]
292 @emph{Target CRIS options:}
293 [@b{--underscore} | @b{--no-underscore}]
295 [@b{--emulation=criself} | @b{--emulation=crisaout}]
296 [@b{--march=v0_v10} | @b{--march=v10} | @b{--march=v32} | @b{--march=common_v10_v32}]
297 @c Deprecated -- deliberately not documented.
302 @emph{Target D10V options:}
307 @emph{Target D30V options:}
308 [@b{-O}|@b{-n}|@b{-N}]
312 @emph{Target EPIPHANY options:}
313 [@b{-mepiphany}|@b{-mepiphany16}]
317 @emph{Target H8/300 options:}
321 @c HPPA has no machine-dependent assembler options (yet).
325 @emph{Target i386 options:}
326 [@b{--32}|@b{--n32}|@b{--64}] [@b{-n}]
327 [@b{-march}=@var{CPU}[+@var{EXTENSION}@dots{}]] [@b{-mtune}=@var{CPU}]
331 @emph{Target i960 options:}
332 @c see md_parse_option in tc-i960.c
333 [@b{-ACA}|@b{-ACA_A}|@b{-ACB}|@b{-ACC}|@b{-AKA}|@b{-AKB}|
335 [@b{-b}] [@b{-no-relax}]
339 @emph{Target IA-64 options:}
340 [@b{-mconstant-gp}|@b{-mauto-pic}]
341 [@b{-milp32}|@b{-milp64}|@b{-mlp64}|@b{-mp64}]
343 [@b{-mtune=itanium1}|@b{-mtune=itanium2}]
344 [@b{-munwind-check=warning}|@b{-munwind-check=error}]
345 [@b{-mhint.b=ok}|@b{-mhint.b=warning}|@b{-mhint.b=error}]
346 [@b{-x}|@b{-xexplicit}] [@b{-xauto}] [@b{-xdebug}]
350 @emph{Target IP2K options:}
351 [@b{-mip2022}|@b{-mip2022ext}]
355 @emph{Target M32C options:}
356 [@b{-m32c}|@b{-m16c}] [-relax] [-h-tick-hex]
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}|@b{-mm9s12x}|@b{-mm9s12xg}]
373 [@b{-mshort}|@b{-mlong}]
374 [@b{-mshort-double}|@b{-mlong-double}]
375 [@b{--force-long-branches}] [@b{--short-branches}]
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]}]
386 @emph{Target MICROBLAZE options:}
387 @c MicroBlaze has no machine-dependent assembler options.
391 @emph{Target MIPS options:}
392 [@b{-nocpp}] [@b{-EL}] [@b{-EB}] [@b{-O}[@var{optimization level}]]
393 [@b{-g}[@var{debug level}]] [@b{-G} @var{num}] [@b{-KPIC}] [@b{-call_shared}]
394 [@b{-non_shared}] [@b{-xgot} [@b{-mvxworks-pic}]
395 [@b{-mabi}=@var{ABI}] [@b{-32}] [@b{-n32}] [@b{-64}] [@b{-mfp32}] [@b{-mgp32}]
396 [@b{-march}=@var{CPU}] [@b{-mtune}=@var{CPU}] [@b{-mips1}] [@b{-mips2}]
397 [@b{-mips3}] [@b{-mips4}] [@b{-mips5}] [@b{-mips32}] [@b{-mips32r2}]
398 [@b{-mips64}] [@b{-mips64r2}]
399 [@b{-construct-floats}] [@b{-no-construct-floats}]
400 [@b{-trap}] [@b{-no-break}] [@b{-break}] [@b{-no-trap}]
401 [@b{-mips16}] [@b{-no-mips16}]
402 [@b{-mmicromips}] [@b{-mno-micromips}]
403 [@b{-msmartmips}] [@b{-mno-smartmips}]
404 [@b{-mips3d}] [@b{-no-mips3d}]
405 [@b{-mdmx}] [@b{-no-mdmx}]
406 [@b{-mdsp}] [@b{-mno-dsp}]
407 [@b{-mdspr2}] [@b{-mno-dspr2}]
408 [@b{-mmt}] [@b{-mno-mt}]
409 [@b{-mmcu}] [@b{-mno-mcu}]
410 [@b{-mfix7000}] [@b{-mno-fix7000}]
411 [@b{-mfix-vr4120}] [@b{-mno-fix-vr4120}]
412 [@b{-mfix-vr4130}] [@b{-mno-fix-vr4130}]
413 [@b{-mdebug}] [@b{-no-mdebug}]
414 [@b{-mpdr}] [@b{-mno-pdr}]
418 @emph{Target MMIX options:}
419 [@b{--fixed-special-register-names}] [@b{--globalize-symbols}]
420 [@b{--gnu-syntax}] [@b{--relax}] [@b{--no-predefined-symbols}]
421 [@b{--no-expand}] [@b{--no-merge-gregs}] [@b{-x}]
422 [@b{--linker-allocated-gregs}]
426 @emph{Target PDP11 options:}
427 [@b{-mpic}|@b{-mno-pic}] [@b{-mall}] [@b{-mno-extensions}]
428 [@b{-m}@var{extension}|@b{-mno-}@var{extension}]
429 [@b{-m}@var{cpu}] [@b{-m}@var{machine}]
433 @emph{Target picoJava options:}
438 @emph{Target PowerPC options:}
440 [@b{-mpwrx}|@b{-mpwr2}|@b{-mpwr}|@b{-m601}|@b{-mppc}|@b{-mppc32}|@b{-m603}|@b{-m604}|@b{-m403}|@b{-m405}|
441 @b{-m440}|@b{-m464}|@b{-m476}|@b{-m7400}|@b{-m7410}|@b{-m7450}|@b{-m7455}|@b{-m750cl}|@b{-mppc64}|
442 @b{-m620}|@b{-me500}|@b{-e500x2}|@b{-me500mc}|@b{-me500mc64}|@b{-me5500}|@b{-me6500}|@b{-mppc64bridge}|
443 @b{-mbooke}|@b{-mpower4}|@b{-mpr4}|@b{-mpower5}|@b{-mpwr5}|@b{-mpwr5x}|@b{-mpower6}|@b{-mpwr6}|
444 @b{-mpower7}|@b{-mpw7}|@b{-ma2}|@b{-mcell}|@b{-mspe}|@b{-mtitan}|@b{-me300}|@b{-mcom}]
445 [@b{-many}] [@b{-maltivec}|@b{-mvsx}]
446 [@b{-mregnames}|@b{-mno-regnames}]
447 [@b{-mrelocatable}|@b{-mrelocatable-lib}|@b{-K PIC}] [@b{-memb}]
448 [@b{-mlittle}|@b{-mlittle-endian}|@b{-le}|@b{-mbig}|@b{-mbig-endian}|@b{-be}]
449 [@b{-msolaris}|@b{-mno-solaris}]
450 [@b{-nops=@var{count}}]
454 @emph{Target RX options:}
455 [@b{-mlittle-endian}|@b{-mbig-endian}]
456 [@b{-m32bit-ints}|@b{-m16bit-ints}]
457 [@b{-m32bit-doubles}|@b{-m64bit-doubles}]
461 @emph{Target s390 options:}
462 [@b{-m31}|@b{-m64}] [@b{-mesa}|@b{-mzarch}] [@b{-march}=@var{CPU}]
463 [@b{-mregnames}|@b{-mno-regnames}]
464 [@b{-mwarn-areg-zero}]
468 @emph{Target SCORE options:}
469 [@b{-EB}][@b{-EL}][@b{-FIXDD}][@b{-NWARN}]
470 [@b{-SCORE5}][@b{-SCORE5U}][@b{-SCORE7}][@b{-SCORE3}]
471 [@b{-march=score7}][@b{-march=score3}]
472 [@b{-USE_R1}][@b{-KPIC}][@b{-O0}][@b{-G} @var{num}][@b{-V}]
476 @emph{Target SPARC options:}
477 @c The order here is important. See c-sparc.texi.
478 [@b{-Av6}|@b{-Av7}|@b{-Av8}|@b{-Asparclet}|@b{-Asparclite}
479 @b{-Av8plus}|@b{-Av8plusa}|@b{-Av9}|@b{-Av9a}]
480 [@b{-xarch=v8plus}|@b{-xarch=v8plusa}] [@b{-bump}]
485 @emph{Target TIC54X options:}
486 [@b{-mcpu=54[123589]}|@b{-mcpu=54[56]lp}] [@b{-mfar-mode}|@b{-mf}]
487 [@b{-merrors-to-file} @var{<filename>}|@b{-me} @var{<filename>}]
492 @emph{Target TIC6X options:}
493 [@b{-march=@var{arch}}] [@b{-mbig-endian}|@b{-mlittle-endian}]
494 [@b{-mdsbt}|@b{-mno-dsbt}] [@b{-mpid=no}|@b{-mpid=near}|@b{-mpid=far}]
495 [@b{-mpic}|@b{-mno-pic}]
499 @emph{Target TILE-Gx options:}
500 [@b{-m32}|@b{-m64}][@b{-EB}][@b{-EL}]
503 @c TILEPro has no machine-dependent assembler options
508 @emph{Target Xtensa options:}
509 [@b{--[no-]text-section-literals}] [@b{--[no-]absolute-literals}]
510 [@b{--[no-]target-align}] [@b{--[no-]longcalls}]
511 [@b{--[no-]transform}]
512 [@b{--rename-section} @var{oldname}=@var{newname}]
517 @emph{Target Z80 options:}
518 [@b{-z80}] [@b{-r800}]
519 [@b{ -ignore-undocumented-instructions}] [@b{-Wnud}]
520 [@b{ -ignore-unportable-instructions}] [@b{-Wnup}]
521 [@b{ -warn-undocumented-instructions}] [@b{-Wud}]
522 [@b{ -warn-unportable-instructions}] [@b{-Wup}]
523 [@b{ -forbid-undocumented-instructions}] [@b{-Fud}]
524 [@b{ -forbid-unportable-instructions}] [@b{-Fup}]
528 @c Z8000 has no machine-dependent assembler options
537 @include at-file.texi
540 Turn on listings, in any of a variety of ways:
544 omit false conditionals
547 omit debugging directives
550 include general information, like @value{AS} version and options passed
553 include high-level source
559 include macro expansions
562 omit forms processing
568 set the name of the listing file
571 You may combine these options; for example, use @samp{-aln} for assembly
572 listing without forms processing. The @samp{=file} option, if used, must be
573 the last one. By itself, @samp{-a} defaults to @samp{-ahls}.
576 Begin in alternate macro mode.
578 @xref{Altmacro,,@code{.altmacro}}.
581 @item --compress-debug-sections
582 Compress DWARF debug sections using zlib. The debug sections are renamed
583 to begin with @samp{.zdebug}, and the resulting object file may not be
584 compatible with older linkers and object file utilities.
586 @item --nocompress-debug-sections
587 Do not compress DWARF debug sections. This is the default.
590 Ignored. This option is accepted for script compatibility with calls to
593 @item --debug-prefix-map @var{old}=@var{new}
594 When assembling files in directory @file{@var{old}}, record debugging
595 information describing them as in @file{@var{new}} instead.
597 @item --defsym @var{sym}=@var{value}
598 Define the symbol @var{sym} to be @var{value} before assembling the input file.
599 @var{value} must be an integer constant. As in C, a leading @samp{0x}
600 indicates a hexadecimal value, and a leading @samp{0} indicates an octal
601 value. The value of the symbol can be overridden inside a source file via the
602 use of a @code{.set} pseudo-op.
605 ``fast''---skip whitespace and comment preprocessing (assume source is
610 Generate debugging information for each assembler source line using whichever
611 debug format is preferred by the target. This currently means either STABS,
615 Generate stabs debugging information for each assembler line. This
616 may help debugging assembler code, if the debugger can handle it.
619 Generate stabs debugging information for each assembler line, with GNU
620 extensions that probably only gdb can handle, and that could make other
621 debuggers crash or refuse to read your program. This
622 may help debugging assembler code. Currently the only GNU extension is
623 the location of the current working directory at assembling time.
626 Generate DWARF2 debugging information for each assembler line. This
627 may help debugging assembler code, if the debugger can handle it. Note---this
628 option is only supported by some targets, not all of them.
630 @item --size-check=error
631 @itemx --size-check=warning
632 Issue an error or warning for invalid ELF .size directive.
635 Print a summary of the command line options and exit.
638 Print a summary of all target specific options and exit.
641 Add directory @var{dir} to the search list for @code{.include} directives.
644 Don't warn about signed overflow.
647 @ifclear DIFF-TBL-KLUGE
648 This option is accepted but has no effect on the @value{TARGET} family.
650 @ifset DIFF-TBL-KLUGE
651 Issue warnings when difference tables altered for long displacements.
656 Keep (in the symbol table) local symbols. These symbols start with
657 system-specific local label prefixes, typically @samp{.L} for ELF systems
658 or @samp{L} for traditional a.out systems.
663 @item --listing-lhs-width=@var{number}
664 Set the maximum width, in words, of the output data column for an assembler
665 listing to @var{number}.
667 @item --listing-lhs-width2=@var{number}
668 Set the maximum width, in words, of the output data column for continuation
669 lines in an assembler listing to @var{number}.
671 @item --listing-rhs-width=@var{number}
672 Set the maximum width of an input source line, as displayed in a listing, to
675 @item --listing-cont-lines=@var{number}
676 Set the maximum number of lines printed in a listing for a single line of input
679 @item -o @var{objfile}
680 Name the object-file output from @command{@value{AS}} @var{objfile}.
683 Fold the data section into the text section.
685 @kindex --hash-size=@var{number}
686 Set the default size of GAS's hash tables to a prime number close to
687 @var{number}. Increasing this value can reduce the length of time it takes the
688 assembler to perform its tasks, at the expense of increasing the assembler's
689 memory requirements. Similarly reducing this value can reduce the memory
690 requirements at the expense of speed.
692 @item --reduce-memory-overheads
693 This option reduces GAS's memory requirements, at the expense of making the
694 assembly processes slower. Currently this switch is a synonym for
695 @samp{--hash-size=4051}, but in the future it may have other effects as well.
698 Print the maximum space (in bytes) and total time (in seconds) used by
701 @item --strip-local-absolute
702 Remove local absolute symbols from the outgoing symbol table.
706 Print the @command{as} version.
709 Print the @command{as} version and exit.
713 Suppress warning messages.
715 @item --fatal-warnings
716 Treat warnings as errors.
719 Don't suppress warning messages or treat them as errors.
728 Generate an object file even after errors.
730 @item -- | @var{files} @dots{}
731 Standard input, or source files to assemble.
739 @xref{Alpha Options}, for the options available when @value{AS} is configured
740 for an Alpha processor.
745 The following options are available when @value{AS} is configured for an Alpha
749 @include c-alpha.texi
750 @c ended inside the included file
757 The following options are available when @value{AS} is configured for
762 This option selects the core processor variant.
764 Select either big-endian (-EB) or little-endian (-EL) output.
769 The following options are available when @value{AS} is configured for the ARM
773 @item -mcpu=@var{processor}[+@var{extension}@dots{}]
774 Specify which ARM processor variant is the target.
775 @item -march=@var{architecture}[+@var{extension}@dots{}]
776 Specify which ARM architecture variant is used by the target.
777 @item -mfpu=@var{floating-point-format}
778 Select which Floating Point architecture is the target.
779 @item -mfloat-abi=@var{abi}
780 Select which floating point ABI is in use.
782 Enable Thumb only instruction decoding.
783 @item -mapcs-32 | -mapcs-26 | -mapcs-float | -mapcs-reentrant
784 Select which procedure calling convention is in use.
786 Select either big-endian (-EB) or little-endian (-EL) output.
787 @item -mthumb-interwork
788 Specify that the code has been generated with interworking between Thumb and
791 Specify that PIC code has been generated.
799 @xref{Blackfin Options}, for the options available when @value{AS} is
800 configured for the Blackfin processor family.
805 The following options are available when @value{AS} is configured for
806 the Blackfin processor family.
810 @c ended inside the included file
817 See the info pages for documentation of the CRIS-specific options.
821 The following options are available when @value{AS} is configured for
824 @cindex D10V optimization
825 @cindex optimization, D10V
827 Optimize output by parallelizing instructions.
832 The following options are available when @value{AS} is configured for a D30V
835 @cindex D30V optimization
836 @cindex optimization, D30V
838 Optimize output by parallelizing instructions.
842 Warn when nops are generated.
844 @cindex D30V nops after 32-bit multiply
846 Warn when a nop after a 32-bit multiply instruction is generated.
852 The following options are available when @value{AS} is configured for the
853 Adapteva EPIPHANY series.
856 @xref{Epiphany Options}, for the options available when @value{AS} is
857 configured for an Epiphany processor.
862 The following options are available when @value{AS} is configured for
863 an Epiphany processor.
866 @include c-epiphany.texi
867 @c ended inside the included file
875 @xref{i386-Options}, for the options available when @value{AS} is
876 configured for an i386 processor.
881 The following options are available when @value{AS} is configured for
886 @c ended inside the included file
893 The following options are available when @value{AS} is configured for the
894 Intel 80960 processor.
897 @item -ACA | -ACA_A | -ACB | -ACC | -AKA | -AKB | -AKC | -AMC
898 Specify which variant of the 960 architecture is the target.
901 Add code to collect statistics about branches taken.
904 Do not alter compare-and-branch instructions for long displacements;
911 The following options are available when @value{AS} is configured for the
917 Specifies that the extended IP2022 instructions are allowed.
920 Restores the default behaviour, which restricts the permitted instructions to
921 just the basic IP2022 ones.
927 The following options are available when @value{AS} is configured for the
928 Renesas M32C and M16C processors.
933 Assemble M32C instructions.
936 Assemble M16C instructions (the default).
939 Enable support for link-time relaxations.
942 Support H'00 style hex constants in addition to 0x00 style.
948 The following options are available when @value{AS} is configured for the
949 Renesas M32R (formerly Mitsubishi M32R) series.
954 Specify which processor in the M32R family is the target. The default
955 is normally the M32R, but this option changes it to the M32RX.
957 @item --warn-explicit-parallel-conflicts or --Wp
958 Produce warning messages when questionable parallel constructs are
961 @item --no-warn-explicit-parallel-conflicts or --Wnp
962 Do not produce warning messages when questionable parallel constructs are
969 The following options are available when @value{AS} is configured for the
970 Motorola 68000 series.
975 Shorten references to undefined symbols, to one word instead of two.
977 @item -m68000 | -m68008 | -m68010 | -m68020 | -m68030
978 @itemx | -m68040 | -m68060 | -m68302 | -m68331 | -m68332
979 @itemx | -m68333 | -m68340 | -mcpu32 | -m5200
980 Specify what processor in the 68000 family is the target. The default
981 is normally the 68020, but this can be changed at configuration time.
983 @item -m68881 | -m68882 | -mno-68881 | -mno-68882
984 The target machine does (or does not) have a floating-point coprocessor.
985 The default is to assume a coprocessor for 68020, 68030, and cpu32. Although
986 the basic 68000 is not compatible with the 68881, a combination of the
987 two can be specified, since it's possible to do emulation of the
988 coprocessor instructions with the main processor.
990 @item -m68851 | -mno-68851
991 The target machine does (or does not) have a memory-management
992 unit coprocessor. The default is to assume an MMU for 68020 and up.
999 For details about the PDP-11 machine dependent features options,
1000 see @ref{PDP-11-Options}.
1003 @item -mpic | -mno-pic
1004 Generate position-independent (or position-dependent) code. The
1005 default is @option{-mpic}.
1008 @itemx -mall-extensions
1009 Enable all instruction set extensions. This is the default.
1011 @item -mno-extensions
1012 Disable all instruction set extensions.
1014 @item -m@var{extension} | -mno-@var{extension}
1015 Enable (or disable) a particular instruction set extension.
1018 Enable the instruction set extensions supported by a particular CPU, and
1019 disable all other extensions.
1021 @item -m@var{machine}
1022 Enable the instruction set extensions supported by a particular machine
1023 model, and disable all other extensions.
1029 The following options are available when @value{AS} is configured for
1030 a picoJava processor.
1034 @cindex PJ endianness
1035 @cindex endianness, PJ
1036 @cindex big endian output, PJ
1038 Generate ``big endian'' format output.
1040 @cindex little endian output, PJ
1042 Generate ``little endian'' format output.
1048 The following options are available when @value{AS} is configured for the
1049 Motorola 68HC11 or 68HC12 series.
1053 @item -m68hc11 | -m68hc12 | -m68hcs12 | -mm9s12x | -mm9s12xg
1054 Specify what processor is the target. The default is
1055 defined by the configuration option when building the assembler.
1057 @item --xgate-ramoffset
1058 Instruct the linker to offset RAM addresses from S12X address space into
1059 XGATE address space.
1062 Specify to use the 16-bit integer ABI.
1065 Specify to use the 32-bit integer ABI.
1067 @item -mshort-double
1068 Specify to use the 32-bit double ABI.
1071 Specify to use the 64-bit double ABI.
1073 @item --force-long-branches
1074 Relative branches are turned into absolute ones. This concerns
1075 conditional branches, unconditional branches and branches to a
1078 @item -S | --short-branches
1079 Do not turn relative branches into absolute ones
1080 when the offset is out of range.
1082 @item --strict-direct-mode
1083 Do not turn the direct addressing mode into extended addressing mode
1084 when the instruction does not support direct addressing mode.
1086 @item --print-insn-syntax
1087 Print the syntax of instruction in case of error.
1089 @item --print-opcodes
1090 Print the list of instructions with syntax and then exit.
1092 @item --generate-example
1093 Print an example of instruction for each possible instruction and then exit.
1094 This option is only useful for testing @command{@value{AS}}.
1100 The following options are available when @command{@value{AS}} is configured
1101 for the SPARC architecture:
1104 @item -Av6 | -Av7 | -Av8 | -Asparclet | -Asparclite
1105 @itemx -Av8plus | -Av8plusa | -Av9 | -Av9a
1106 Explicitly select a variant of the SPARC architecture.
1108 @samp{-Av8plus} and @samp{-Av8plusa} select a 32 bit environment.
1109 @samp{-Av9} and @samp{-Av9a} select a 64 bit environment.
1111 @samp{-Av8plusa} and @samp{-Av9a} enable the SPARC V9 instruction set with
1112 UltraSPARC extensions.
1114 @item -xarch=v8plus | -xarch=v8plusa
1115 For compatibility with the Solaris v9 assembler. These options are
1116 equivalent to -Av8plus and -Av8plusa, respectively.
1119 Warn when the assembler switches to another architecture.
1124 The following options are available when @value{AS} is configured for the 'c54x
1129 Enable extended addressing mode. All addresses and relocations will assume
1130 extended addressing (usually 23 bits).
1131 @item -mcpu=@var{CPU_VERSION}
1132 Sets the CPU version being compiled for.
1133 @item -merrors-to-file @var{FILENAME}
1134 Redirect error output to a file, for broken systems which don't support such
1135 behaviour in the shell.
1140 The following options are available when @value{AS} is configured for
1141 a @sc{mips} processor.
1145 This option sets the largest size of an object that can be referenced
1146 implicitly with the @code{gp} register. It is only accepted for targets that
1147 use ECOFF format, such as a DECstation running Ultrix. The default value is 8.
1149 @cindex MIPS endianness
1150 @cindex endianness, MIPS
1151 @cindex big endian output, MIPS
1153 Generate ``big endian'' format output.
1155 @cindex little endian output, MIPS
1157 Generate ``little endian'' format output.
1169 Generate code for a particular @sc{mips} Instruction Set Architecture level.
1170 @samp{-mips1} is an alias for @samp{-march=r3000}, @samp{-mips2} is an
1171 alias for @samp{-march=r6000}, @samp{-mips3} is an alias for
1172 @samp{-march=r4000} and @samp{-mips4} is an alias for @samp{-march=r8000}.
1173 @samp{-mips5}, @samp{-mips32}, @samp{-mips32r2}, @samp{-mips64}, and
1175 correspond to generic
1176 @samp{MIPS V}, @samp{MIPS32}, @samp{MIPS32 Release 2}, @samp{MIPS64},
1177 and @samp{MIPS64 Release 2}
1178 ISA processors, respectively.
1180 @item -march=@var{CPU}
1181 Generate code for a particular @sc{mips} cpu.
1183 @item -mtune=@var{cpu}
1184 Schedule and tune for a particular @sc{mips} cpu.
1188 Cause nops to be inserted if the read of the destination register
1189 of an mfhi or mflo instruction occurs in the following two instructions.
1193 Cause stabs-style debugging output to go into an ECOFF-style .mdebug
1194 section instead of the standard ELF .stabs sections.
1198 Control generation of @code{.pdr} sections.
1202 The register sizes are normally inferred from the ISA and ABI, but these
1203 flags force a certain group of registers to be treated as 32 bits wide at
1204 all times. @samp{-mgp32} controls the size of general-purpose registers
1205 and @samp{-mfp32} controls the size of floating-point registers.
1209 Generate code for the MIPS 16 processor. This is equivalent to putting
1210 @code{.set mips16} at the start of the assembly file. @samp{-no-mips16}
1211 turns off this option.
1214 @itemx -mno-micromips
1215 Generate code for the microMIPS processor. This is equivalent to putting
1216 @code{.set micromips} at the start of the assembly file. @samp{-mno-micromips}
1217 turns off this option. This is equivalent to putting @code{.set nomicromips}
1218 at the start of the assembly file.
1221 @itemx -mno-smartmips
1222 Enables the SmartMIPS extension to the MIPS32 instruction set. This is
1223 equivalent to putting @code{.set smartmips} at the start of the assembly file.
1224 @samp{-mno-smartmips} turns off this option.
1228 Generate code for the MIPS-3D Application Specific Extension.
1229 This tells the assembler to accept MIPS-3D instructions.
1230 @samp{-no-mips3d} turns off this option.
1234 Generate code for the MDMX Application Specific Extension.
1235 This tells the assembler to accept MDMX instructions.
1236 @samp{-no-mdmx} turns off this option.
1240 Generate code for the DSP Release 1 Application Specific Extension.
1241 This tells the assembler to accept DSP Release 1 instructions.
1242 @samp{-mno-dsp} turns off this option.
1246 Generate code for the DSP Release 2 Application Specific Extension.
1247 This option implies -mdsp.
1248 This tells the assembler to accept DSP Release 2 instructions.
1249 @samp{-mno-dspr2} turns off this option.
1253 Generate code for the MT Application Specific Extension.
1254 This tells the assembler to accept MT instructions.
1255 @samp{-mno-mt} turns off this option.
1259 Generate code for the MCU Application Specific Extension.
1260 This tells the assembler to accept MCU instructions.
1261 @samp{-mno-mcu} turns off this option.
1263 @item --construct-floats
1264 @itemx --no-construct-floats
1265 The @samp{--no-construct-floats} option disables the construction of
1266 double width floating point constants by loading the two halves of the
1267 value into the two single width floating point registers that make up
1268 the double width register. By default @samp{--construct-floats} is
1269 selected, allowing construction of these floating point constants.
1272 @item --emulation=@var{name}
1273 This option causes @command{@value{AS}} to emulate @command{@value{AS}} configured
1274 for some other target, in all respects, including output format (choosing
1275 between ELF and ECOFF only), handling of pseudo-opcodes which may generate
1276 debugging information or store symbol table information, and default
1277 endianness. The available configuration names are: @samp{mipsecoff},
1278 @samp{mipself}, @samp{mipslecoff}, @samp{mipsbecoff}, @samp{mipslelf},
1279 @samp{mipsbelf}. The first two do not alter the default endianness from that
1280 of the primary target for which the assembler was configured; the others change
1281 the default to little- or big-endian as indicated by the @samp{b} or @samp{l}
1282 in the name. Using @samp{-EB} or @samp{-EL} will override the endianness
1283 selection in any case.
1285 This option is currently supported only when the primary target
1286 @command{@value{AS}} is configured for is a @sc{mips} ELF or ECOFF target.
1287 Furthermore, the primary target or others specified with
1288 @samp{--enable-targets=@dots{}} at configuration time must include support for
1289 the other format, if both are to be available. For example, the Irix 5
1290 configuration includes support for both.
1292 Eventually, this option will support more configurations, with more
1293 fine-grained control over the assembler's behavior, and will be supported for
1297 @command{@value{AS}} ignores this option. It is accepted for compatibility with
1304 Control how to deal with multiplication overflow and division by zero.
1305 @samp{--trap} or @samp{--no-break} (which are synonyms) take a trap exception
1306 (and only work for Instruction Set Architecture level 2 and higher);
1307 @samp{--break} or @samp{--no-trap} (also synonyms, and the default) take a
1311 When this option is used, @command{@value{AS}} will issue a warning every
1312 time it generates a nop instruction from a macro.
1317 The following options are available when @value{AS} is configured for
1323 Enable or disable the JSRI to BSR transformation. By default this is enabled.
1324 The command line option @samp{-nojsri2bsr} can be used to disable it.
1328 Enable or disable the silicon filter behaviour. By default this is disabled.
1329 The default can be overridden by the @samp{-sifilter} command line option.
1332 Alter jump instructions for long displacements.
1334 @item -mcpu=[210|340]
1335 Select the cpu type on the target hardware. This controls which instructions
1339 Assemble for a big endian target.
1342 Assemble for a little endian target.
1348 See the info pages for documentation of the MMIX-specific options.
1355 @xref{PowerPC-Opts}, for the options available when @value{AS} is configured
1356 for a PowerPC processor.
1360 @c man begin OPTIONS
1361 The following options are available when @value{AS} is configured for a
1364 @c man begin INCLUDE
1366 @c ended inside the included file
1371 @c man begin OPTIONS
1373 See the info pages for documentation of the RX-specific options.
1377 The following options are available when @value{AS} is configured for the s390
1383 Select the word size, either 31/32 bits or 64 bits.
1386 Select the architecture mode, either the Enterprise System
1387 Architecture (esa) or the z/Architecture mode (zarch).
1388 @item -march=@var{processor}
1389 Specify which s390 processor variant is the target, @samp{g6}, @samp{g6},
1390 @samp{z900}, @samp{z990}, @samp{z9-109}, @samp{z9-ec}, or @samp{z10}.
1392 @itemx -mno-regnames
1393 Allow or disallow symbolic names for registers.
1394 @item -mwarn-areg-zero
1395 Warn whenever the operand for a base or index register has been specified
1396 but evaluates to zero.
1404 @xref{TIC6X Options}, for the options available when @value{AS} is configured
1405 for a TMS320C6000 processor.
1409 @c man begin OPTIONS
1410 The following options are available when @value{AS} is configured for a
1411 TMS320C6000 processor.
1413 @c man begin INCLUDE
1414 @include c-tic6x.texi
1415 @c ended inside the included file
1423 @xref{TILE-Gx Options}, for the options available when @value{AS} is configured
1424 for a TILE-Gx processor.
1428 @c man begin OPTIONS
1429 The following options are available when @value{AS} is configured for a TILE-Gx
1432 @c man begin INCLUDE
1433 @include c-tilegx.texi
1434 @c ended inside the included file
1442 @xref{Xtensa Options}, for the options available when @value{AS} is configured
1443 for an Xtensa processor.
1447 @c man begin OPTIONS
1448 The following options are available when @value{AS} is configured for an
1451 @c man begin INCLUDE
1452 @include c-xtensa.texi
1453 @c ended inside the included file
1458 @c man begin OPTIONS
1461 The following options are available when @value{AS} is configured for
1462 a Z80 family processor.
1465 Assemble for Z80 processor.
1467 Assemble for R800 processor.
1468 @item -ignore-undocumented-instructions
1470 Assemble undocumented Z80 instructions that also work on R800 without warning.
1471 @item -ignore-unportable-instructions
1473 Assemble all undocumented Z80 instructions without warning.
1474 @item -warn-undocumented-instructions
1476 Issue a warning for undocumented Z80 instructions that also work on R800.
1477 @item -warn-unportable-instructions
1479 Issue a warning for undocumented Z80 instructions that do not work on R800.
1480 @item -forbid-undocumented-instructions
1482 Treat all undocumented instructions as errors.
1483 @item -forbid-unportable-instructions
1485 Treat undocumented Z80 instructions that do not work on R800 as errors.
1492 * Manual:: Structure of this Manual
1493 * GNU Assembler:: The GNU Assembler
1494 * Object Formats:: Object File Formats
1495 * Command Line:: Command Line
1496 * Input Files:: Input Files
1497 * Object:: Output (Object) File
1498 * Errors:: Error and Warning Messages
1502 @section Structure of this Manual
1504 @cindex manual, structure and purpose
1505 This manual is intended to describe what you need to know to use
1506 @sc{gnu} @command{@value{AS}}. We cover the syntax expected in source files, including
1507 notation for symbols, constants, and expressions; the directives that
1508 @command{@value{AS}} understands; and of course how to invoke @command{@value{AS}}.
1511 We also cover special features in the @value{TARGET}
1512 configuration of @command{@value{AS}}, including assembler directives.
1515 This manual also describes some of the machine-dependent features of
1516 various flavors of the assembler.
1519 @cindex machine instructions (not covered)
1520 On the other hand, this manual is @emph{not} intended as an introduction
1521 to programming in assembly language---let alone programming in general!
1522 In a similar vein, we make no attempt to introduce the machine
1523 architecture; we do @emph{not} describe the instruction set, standard
1524 mnemonics, registers or addressing modes that are standard to a
1525 particular architecture.
1527 You may want to consult the manufacturer's
1528 machine architecture manual for this information.
1532 For information on the H8/300 machine instruction set, see @cite{H8/300
1533 Series Programming Manual}. For the H8/300H, see @cite{H8/300H Series
1534 Programming Manual} (Renesas).
1537 For information on the Renesas (formerly Hitachi) / SuperH SH machine instruction set,
1538 see @cite{SH-Microcomputer User's Manual} (Renesas) or
1539 @cite{SH-4 32-bit CPU Core Architecture} (SuperH) and
1540 @cite{SuperH (SH) 64-Bit RISC Series} (SuperH).
1543 For information on the Z8000 machine instruction set, see @cite{Z8000 CPU Technical Manual}
1547 @c I think this is premature---doc@cygnus.com, 17jan1991
1549 Throughout this manual, we assume that you are running @dfn{GNU},
1550 the portable operating system from the @dfn{Free Software
1551 Foundation, Inc.}. This restricts our attention to certain kinds of
1552 computer (in particular, the kinds of computers that @sc{gnu} can run on);
1553 once this assumption is granted examples and definitions need less
1556 @command{@value{AS}} is part of a team of programs that turn a high-level
1557 human-readable series of instructions into a low-level
1558 computer-readable series of instructions. Different versions of
1559 @command{@value{AS}} are used for different kinds of computer.
1562 @c There used to be a section "Terminology" here, which defined
1563 @c "contents", "byte", "word", and "long". Defining "word" to any
1564 @c particular size is confusing when the .word directive may generate 16
1565 @c bits on one machine and 32 bits on another; in general, for the user
1566 @c version of this manual, none of these terms seem essential to define.
1567 @c They were used very little even in the former draft of the manual;
1568 @c this draft makes an effort to avoid them (except in names of
1572 @section The GNU Assembler
1574 @c man begin DESCRIPTION
1576 @sc{gnu} @command{as} is really a family of assemblers.
1578 This manual describes @command{@value{AS}}, a member of that family which is
1579 configured for the @value{TARGET} architectures.
1581 If you use (or have used) the @sc{gnu} assembler on one architecture, you
1582 should find a fairly similar environment when you use it on another
1583 architecture. Each version has much in common with the others,
1584 including object file formats, most assembler directives (often called
1585 @dfn{pseudo-ops}) and assembler syntax.@refill
1587 @cindex purpose of @sc{gnu} assembler
1588 @command{@value{AS}} is primarily intended to assemble the output of the
1589 @sc{gnu} C compiler @code{@value{GCC}} for use by the linker
1590 @code{@value{LD}}. Nevertheless, we've tried to make @command{@value{AS}}
1591 assemble correctly everything that other assemblers for the same
1592 machine would assemble.
1594 Any exceptions are documented explicitly (@pxref{Machine Dependencies}).
1597 @c This remark should appear in generic version of manual; assumption
1598 @c here is that generic version sets M680x0.
1599 This doesn't mean @command{@value{AS}} always uses the same syntax as another
1600 assembler for the same architecture; for example, we know of several
1601 incompatible versions of 680x0 assembly language syntax.
1606 Unlike older assemblers, @command{@value{AS}} is designed to assemble a source
1607 program in one pass of the source file. This has a subtle impact on the
1608 @kbd{.org} directive (@pxref{Org,,@code{.org}}).
1610 @node Object Formats
1611 @section Object File Formats
1613 @cindex object file format
1614 The @sc{gnu} assembler can be configured to produce several alternative
1615 object file formats. For the most part, this does not affect how you
1616 write assembly language programs; but directives for debugging symbols
1617 are typically different in different file formats. @xref{Symbol
1618 Attributes,,Symbol Attributes}.
1621 For the @value{TARGET} target, @command{@value{AS}} is configured to produce
1622 @value{OBJ-NAME} format object files.
1624 @c The following should exhaust all configs that set MULTI-OBJ, ideally
1626 On the @value{TARGET}, @command{@value{AS}} can be configured to produce either
1627 @code{b.out} or COFF format object files.
1630 On the @value{TARGET}, @command{@value{AS}} can be configured to produce either
1631 SOM or ELF format object files.
1636 @section Command Line
1638 @cindex command line conventions
1640 After the program name @command{@value{AS}}, the command line may contain
1641 options and file names. Options may appear in any order, and may be
1642 before, after, or between file names. The order of file names is
1645 @cindex standard input, as input file
1647 @file{--} (two hyphens) by itself names the standard input file
1648 explicitly, as one of the files for @command{@value{AS}} to assemble.
1650 @cindex options, command line
1651 Except for @samp{--} any command line argument that begins with a
1652 hyphen (@samp{-}) is an option. Each option changes the behavior of
1653 @command{@value{AS}}. No option changes the way another option works. An
1654 option is a @samp{-} followed by one or more letters; the case of
1655 the letter is important. All options are optional.
1657 Some options expect exactly one file name to follow them. The file
1658 name may either immediately follow the option's letter (compatible
1659 with older assemblers) or it may be the next command argument (@sc{gnu}
1660 standard). These two command lines are equivalent:
1663 @value{AS} -o my-object-file.o mumble.s
1664 @value{AS} -omy-object-file.o mumble.s
1668 @section Input Files
1671 @cindex source program
1672 @cindex files, input
1673 We use the phrase @dfn{source program}, abbreviated @dfn{source}, to
1674 describe the program input to one run of @command{@value{AS}}. The program may
1675 be in one or more files; how the source is partitioned into files
1676 doesn't change the meaning of the source.
1678 @c I added "con" prefix to "catenation" just to prove I can overcome my
1679 @c APL training... doc@cygnus.com
1680 The source program is a concatenation of the text in all the files, in the
1683 @c man begin DESCRIPTION
1684 Each time you run @command{@value{AS}} it assembles exactly one source
1685 program. The source program is made up of one or more files.
1686 (The standard input is also a file.)
1688 You give @command{@value{AS}} a command line that has zero or more input file
1689 names. The input files are read (from left file name to right). A
1690 command line argument (in any position) that has no special meaning
1691 is taken to be an input file name.
1693 If you give @command{@value{AS}} no file names it attempts to read one input file
1694 from the @command{@value{AS}} standard input, which is normally your terminal. You
1695 may have to type @key{ctl-D} to tell @command{@value{AS}} there is no more program
1698 Use @samp{--} if you need to explicitly name the standard input file
1699 in your command line.
1701 If the source is empty, @command{@value{AS}} produces a small, empty object
1706 @subheading Filenames and Line-numbers
1708 @cindex input file linenumbers
1709 @cindex line numbers, in input files
1710 There are two ways of locating a line in the input file (or files) and
1711 either may be used in reporting error messages. One way refers to a line
1712 number in a physical file; the other refers to a line number in a
1713 ``logical'' file. @xref{Errors, ,Error and Warning Messages}.
1715 @dfn{Physical files} are those files named in the command line given
1716 to @command{@value{AS}}.
1718 @dfn{Logical files} are simply names declared explicitly by assembler
1719 directives; they bear no relation to physical files. Logical file names help
1720 error messages reflect the original source file, when @command{@value{AS}} source
1721 is itself synthesized from other files. @command{@value{AS}} understands the
1722 @samp{#} directives emitted by the @code{@value{GCC}} preprocessor. See also
1723 @ref{File,,@code{.file}}.
1726 @section Output (Object) File
1732 Every time you run @command{@value{AS}} it produces an output file, which is
1733 your assembly language program translated into numbers. This file
1734 is the object file. Its default name is
1742 @code{b.out} when @command{@value{AS}} is configured for the Intel 80960.
1744 You can give it another name by using the @option{-o} option. Conventionally,
1745 object file names end with @file{.o}. The default name is used for historical
1746 reasons: older assemblers were capable of assembling self-contained programs
1747 directly into a runnable program. (For some formats, this isn't currently
1748 possible, but it can be done for the @code{a.out} format.)
1752 The object file is meant for input to the linker @code{@value{LD}}. It contains
1753 assembled program code, information to help @code{@value{LD}} integrate
1754 the assembled program into a runnable file, and (optionally) symbolic
1755 information for the debugger.
1757 @c link above to some info file(s) like the description of a.out.
1758 @c don't forget to describe @sc{gnu} info as well as Unix lossage.
1761 @section Error and Warning Messages
1763 @c man begin DESCRIPTION
1765 @cindex error messages
1766 @cindex warning messages
1767 @cindex messages from assembler
1768 @command{@value{AS}} may write warnings and error messages to the standard error
1769 file (usually your terminal). This should not happen when a compiler
1770 runs @command{@value{AS}} automatically. Warnings report an assumption made so
1771 that @command{@value{AS}} could keep assembling a flawed program; errors report a
1772 grave problem that stops the assembly.
1776 @cindex format of warning messages
1777 Warning messages have the format
1780 file_name:@b{NNN}:Warning Message Text
1784 @cindex line numbers, in warnings/errors
1785 (where @b{NNN} is a line number). If a logical file name has been given
1786 (@pxref{File,,@code{.file}}) it is used for the filename, otherwise the name of
1787 the current input file is used. If a logical line number was given
1789 (@pxref{Line,,@code{.line}})
1791 then it is used to calculate the number printed,
1792 otherwise the actual line in the current source file is printed. The
1793 message text is intended to be self explanatory (in the grand Unix
1796 @cindex format of error messages
1797 Error messages have the format
1799 file_name:@b{NNN}:FATAL:Error Message Text
1801 The file name and line number are derived as for warning
1802 messages. The actual message text may be rather less explanatory
1803 because many of them aren't supposed to happen.
1806 @chapter Command-Line Options
1808 @cindex options, all versions of assembler
1809 This chapter describes command-line options available in @emph{all}
1810 versions of the @sc{gnu} assembler; see @ref{Machine Dependencies},
1811 for options specific
1813 to the @value{TARGET} target.
1816 to particular machine architectures.
1819 @c man begin DESCRIPTION
1821 If you are invoking @command{@value{AS}} via the @sc{gnu} C compiler,
1822 you can use the @samp{-Wa} option to pass arguments through to the assembler.
1823 The assembler arguments must be separated from each other (and the @samp{-Wa})
1824 by commas. For example:
1827 gcc -c -g -O -Wa,-alh,-L file.c
1831 This passes two options to the assembler: @samp{-alh} (emit a listing to
1832 standard output with high-level and assembly source) and @samp{-L} (retain
1833 local symbols in the symbol table).
1835 Usually you do not need to use this @samp{-Wa} mechanism, since many compiler
1836 command-line options are automatically passed to the assembler by the compiler.
1837 (You can call the @sc{gnu} compiler driver with the @samp{-v} option to see
1838 precisely what options it passes to each compilation pass, including the
1844 * a:: -a[cdghlns] enable listings
1845 * alternate:: --alternate enable alternate macro syntax
1846 * D:: -D for compatibility
1847 * f:: -f to work faster
1848 * I:: -I for .include search path
1849 @ifclear DIFF-TBL-KLUGE
1850 * K:: -K for compatibility
1852 @ifset DIFF-TBL-KLUGE
1853 * K:: -K for difference tables
1856 * L:: -L to retain local symbols
1857 * listing:: --listing-XXX to configure listing output
1858 * M:: -M or --mri to assemble in MRI compatibility mode
1859 * MD:: --MD for dependency tracking
1860 * o:: -o to name the object file
1861 * R:: -R to join data and text sections
1862 * statistics:: --statistics to see statistics about assembly
1863 * traditional-format:: --traditional-format for compatible output
1864 * v:: -v to announce version
1865 * W:: -W, --no-warn, --warn, --fatal-warnings to control warnings
1866 * Z:: -Z to make object file even after errors
1870 @section Enable Listings: @option{-a[cdghlns]}
1880 @cindex listings, enabling
1881 @cindex assembly listings, enabling
1883 These options enable listing output from the assembler. By itself,
1884 @samp{-a} requests high-level, assembly, and symbols listing.
1885 You can use other letters to select specific options for the list:
1886 @samp{-ah} requests a high-level language listing,
1887 @samp{-al} requests an output-program assembly listing, and
1888 @samp{-as} requests a symbol table listing.
1889 High-level listings require that a compiler debugging option like
1890 @samp{-g} be used, and that assembly listings (@samp{-al}) be requested
1893 Use the @samp{-ag} option to print a first section with general assembly
1894 information, like @value{AS} version, switches passed, or time stamp.
1896 Use the @samp{-ac} option to omit false conditionals from a listing. Any lines
1897 which are not assembled because of a false @code{.if} (or @code{.ifdef}, or any
1898 other conditional), or a true @code{.if} followed by an @code{.else}, will be
1899 omitted from the listing.
1901 Use the @samp{-ad} option to omit debugging directives from the
1904 Once you have specified one of these options, you can further control
1905 listing output and its appearance using the directives @code{.list},
1906 @code{.nolist}, @code{.psize}, @code{.eject}, @code{.title}, and
1908 The @samp{-an} option turns off all forms processing.
1909 If you do not request listing output with one of the @samp{-a} options, the
1910 listing-control directives have no effect.
1912 The letters after @samp{-a} may be combined into one option,
1913 @emph{e.g.}, @samp{-aln}.
1915 Note if the assembler source is coming from the standard input (e.g.,
1917 is being created by @code{@value{GCC}} and the @samp{-pipe} command line switch
1918 is being used) then the listing will not contain any comments or preprocessor
1919 directives. This is because the listing code buffers input source lines from
1920 stdin only after they have been preprocessed by the assembler. This reduces
1921 memory usage and makes the code more efficient.
1924 @section @option{--alternate}
1927 Begin in alternate macro mode, see @ref{Altmacro,,@code{.altmacro}}.
1930 @section @option{-D}
1933 This option has no effect whatsoever, but it is accepted to make it more
1934 likely that scripts written for other assemblers also work with
1935 @command{@value{AS}}.
1938 @section Work Faster: @option{-f}
1941 @cindex trusted compiler
1942 @cindex faster processing (@option{-f})
1943 @samp{-f} should only be used when assembling programs written by a
1944 (trusted) compiler. @samp{-f} stops the assembler from doing whitespace
1945 and comment preprocessing on
1946 the input file(s) before assembling them. @xref{Preprocessing,
1950 @emph{Warning:} if you use @samp{-f} when the files actually need to be
1951 preprocessed (if they contain comments, for example), @command{@value{AS}} does
1956 @section @code{.include} Search Path: @option{-I} @var{path}
1958 @kindex -I @var{path}
1959 @cindex paths for @code{.include}
1960 @cindex search path for @code{.include}
1961 @cindex @code{include} directive search path
1962 Use this option to add a @var{path} to the list of directories
1963 @command{@value{AS}} searches for files specified in @code{.include}
1964 directives (@pxref{Include,,@code{.include}}). You may use @option{-I} as
1965 many times as necessary to include a variety of paths. The current
1966 working directory is always searched first; after that, @command{@value{AS}}
1967 searches any @samp{-I} directories in the same order as they were
1968 specified (left to right) on the command line.
1971 @section Difference Tables: @option{-K}
1974 @ifclear DIFF-TBL-KLUGE
1975 On the @value{TARGET} family, this option is allowed, but has no effect. It is
1976 permitted for compatibility with the @sc{gnu} assembler on other platforms,
1977 where it can be used to warn when the assembler alters the machine code
1978 generated for @samp{.word} directives in difference tables. The @value{TARGET}
1979 family does not have the addressing limitations that sometimes lead to this
1980 alteration on other platforms.
1983 @ifset DIFF-TBL-KLUGE
1984 @cindex difference tables, warning
1985 @cindex warning for altered difference tables
1986 @command{@value{AS}} sometimes alters the code emitted for directives of the
1987 form @samp{.word @var{sym1}-@var{sym2}}. @xref{Word,,@code{.word}}.
1988 You can use the @samp{-K} option if you want a warning issued when this
1993 @section Include Local Symbols: @option{-L}
1996 @cindex local symbols, retaining in output
1997 Symbols beginning with system-specific local label prefixes, typically
1998 @samp{.L} for ELF systems or @samp{L} for traditional a.out systems, are
1999 called @dfn{local symbols}. @xref{Symbol Names}. Normally you do not see
2000 such symbols when debugging, because they are intended for the use of
2001 programs (like compilers) that compose assembler programs, not for your
2002 notice. Normally both @command{@value{AS}} and @code{@value{LD}} discard
2003 such symbols, so you do not normally debug with them.
2005 This option tells @command{@value{AS}} to retain those local symbols
2006 in the object file. Usually if you do this you also tell the linker
2007 @code{@value{LD}} to preserve those symbols.
2010 @section Configuring listing output: @option{--listing}
2012 The listing feature of the assembler can be enabled via the command line switch
2013 @samp{-a} (@pxref{a}). This feature combines the input source file(s) with a
2014 hex dump of the corresponding locations in the output object file, and displays
2015 them as a listing file. The format of this listing can be controlled by
2016 directives inside the assembler source (i.e., @code{.list} (@pxref{List}),
2017 @code{.title} (@pxref{Title}), @code{.sbttl} (@pxref{Sbttl}),
2018 @code{.psize} (@pxref{Psize}), and
2019 @code{.eject} (@pxref{Eject}) and also by the following switches:
2022 @item --listing-lhs-width=@samp{number}
2023 @kindex --listing-lhs-width
2024 @cindex Width of first line disassembly output
2025 Sets the maximum width, in words, of the first line of the hex byte dump. This
2026 dump appears on the left hand side of the listing output.
2028 @item --listing-lhs-width2=@samp{number}
2029 @kindex --listing-lhs-width2
2030 @cindex Width of continuation lines of disassembly output
2031 Sets the maximum width, in words, of any further lines of the hex byte dump for
2032 a given input source line. If this value is not specified, it defaults to being
2033 the same as the value specified for @samp{--listing-lhs-width}. If neither
2034 switch is used the default is to one.
2036 @item --listing-rhs-width=@samp{number}
2037 @kindex --listing-rhs-width
2038 @cindex Width of source line output
2039 Sets the maximum width, in characters, of the source line that is displayed
2040 alongside the hex dump. The default value for this parameter is 100. The
2041 source line is displayed on the right hand side of the listing output.
2043 @item --listing-cont-lines=@samp{number}
2044 @kindex --listing-cont-lines
2045 @cindex Maximum number of continuation lines
2046 Sets the maximum number of continuation lines of hex dump that will be
2047 displayed for a given single line of source input. The default value is 4.
2051 @section Assemble in MRI Compatibility Mode: @option{-M}
2054 @cindex MRI compatibility mode
2055 The @option{-M} or @option{--mri} option selects MRI compatibility mode. This
2056 changes the syntax and pseudo-op handling of @command{@value{AS}} to make it
2057 compatible with the @code{ASM68K} or the @code{ASM960} (depending upon the
2058 configured target) assembler from Microtec Research. The exact nature of the
2059 MRI syntax will not be documented here; see the MRI manuals for more
2060 information. Note in particular that the handling of macros and macro
2061 arguments is somewhat different. The purpose of this option is to permit
2062 assembling existing MRI assembler code using @command{@value{AS}}.
2064 The MRI compatibility is not complete. Certain operations of the MRI assembler
2065 depend upon its object file format, and can not be supported using other object
2066 file formats. Supporting these would require enhancing each object file format
2067 individually. These are:
2070 @item global symbols in common section
2072 The m68k MRI assembler supports common sections which are merged by the linker.
2073 Other object file formats do not support this. @command{@value{AS}} handles
2074 common sections by treating them as a single common symbol. It permits local
2075 symbols to be defined within a common section, but it can not support global
2076 symbols, since it has no way to describe them.
2078 @item complex relocations
2080 The MRI assemblers support relocations against a negated section address, and
2081 relocations which combine the start addresses of two or more sections. These
2082 are not support by other object file formats.
2084 @item @code{END} pseudo-op specifying start address
2086 The MRI @code{END} pseudo-op permits the specification of a start address.
2087 This is not supported by other object file formats. The start address may
2088 instead be specified using the @option{-e} option to the linker, or in a linker
2091 @item @code{IDNT}, @code{.ident} and @code{NAME} pseudo-ops
2093 The MRI @code{IDNT}, @code{.ident} and @code{NAME} pseudo-ops assign a module
2094 name to the output file. This is not supported by other object file formats.
2096 @item @code{ORG} pseudo-op
2098 The m68k MRI @code{ORG} pseudo-op begins an absolute section at a given
2099 address. This differs from the usual @command{@value{AS}} @code{.org} pseudo-op,
2100 which changes the location within the current section. Absolute sections are
2101 not supported by other object file formats. The address of a section may be
2102 assigned within a linker script.
2105 There are some other features of the MRI assembler which are not supported by
2106 @command{@value{AS}}, typically either because they are difficult or because they
2107 seem of little consequence. Some of these may be supported in future releases.
2111 @item EBCDIC strings
2113 EBCDIC strings are not supported.
2115 @item packed binary coded decimal
2117 Packed binary coded decimal is not supported. This means that the @code{DC.P}
2118 and @code{DCB.P} pseudo-ops are not supported.
2120 @item @code{FEQU} pseudo-op
2122 The m68k @code{FEQU} pseudo-op is not supported.
2124 @item @code{NOOBJ} pseudo-op
2126 The m68k @code{NOOBJ} pseudo-op is not supported.
2128 @item @code{OPT} branch control options
2130 The m68k @code{OPT} branch control options---@code{B}, @code{BRS}, @code{BRB},
2131 @code{BRL}, and @code{BRW}---are ignored. @command{@value{AS}} automatically
2132 relaxes all branches, whether forward or backward, to an appropriate size, so
2133 these options serve no purpose.
2135 @item @code{OPT} list control options
2137 The following m68k @code{OPT} list control options are ignored: @code{C},
2138 @code{CEX}, @code{CL}, @code{CRE}, @code{E}, @code{G}, @code{I}, @code{M},
2139 @code{MEX}, @code{MC}, @code{MD}, @code{X}.
2141 @item other @code{OPT} options
2143 The following m68k @code{OPT} options are ignored: @code{NEST}, @code{O},
2144 @code{OLD}, @code{OP}, @code{P}, @code{PCO}, @code{PCR}, @code{PCS}, @code{R}.
2146 @item @code{OPT} @code{D} option is default
2148 The m68k @code{OPT} @code{D} option is the default, unlike the MRI assembler.
2149 @code{OPT NOD} may be used to turn it off.
2151 @item @code{XREF} pseudo-op.
2153 The m68k @code{XREF} pseudo-op is ignored.
2155 @item @code{.debug} pseudo-op
2157 The i960 @code{.debug} pseudo-op is not supported.
2159 @item @code{.extended} pseudo-op
2161 The i960 @code{.extended} pseudo-op is not supported.
2163 @item @code{.list} pseudo-op.
2165 The various options of the i960 @code{.list} pseudo-op are not supported.
2167 @item @code{.optimize} pseudo-op
2169 The i960 @code{.optimize} pseudo-op is not supported.
2171 @item @code{.output} pseudo-op
2173 The i960 @code{.output} pseudo-op is not supported.
2175 @item @code{.setreal} pseudo-op
2177 The i960 @code{.setreal} pseudo-op is not supported.
2182 @section Dependency Tracking: @option{--MD}
2185 @cindex dependency tracking
2188 @command{@value{AS}} can generate a dependency file for the file it creates. This
2189 file consists of a single rule suitable for @code{make} describing the
2190 dependencies of the main source file.
2192 The rule is written to the file named in its argument.
2194 This feature is used in the automatic updating of makefiles.
2197 @section Name the Object File: @option{-o}
2200 @cindex naming object file
2201 @cindex object file name
2202 There is always one object file output when you run @command{@value{AS}}. By
2203 default it has the name
2206 @file{a.out} (or @file{b.out}, for Intel 960 targets only).
2220 You use this option (which takes exactly one filename) to give the
2221 object file a different name.
2223 Whatever the object file is called, @command{@value{AS}} overwrites any
2224 existing file of the same name.
2227 @section Join Data and Text Sections: @option{-R}
2230 @cindex data and text sections, joining
2231 @cindex text and data sections, joining
2232 @cindex joining text and data sections
2233 @cindex merging text and data sections
2234 @option{-R} tells @command{@value{AS}} to write the object file as if all
2235 data-section data lives in the text section. This is only done at
2236 the very last moment: your binary data are the same, but data
2237 section parts are relocated differently. The data section part of
2238 your object file is zero bytes long because all its bytes are
2239 appended to the text section. (@xref{Sections,,Sections and Relocation}.)
2241 When you specify @option{-R} it would be possible to generate shorter
2242 address displacements (because we do not have to cross between text and
2243 data section). We refrain from doing this simply for compatibility with
2244 older versions of @command{@value{AS}}. In future, @option{-R} may work this way.
2247 When @command{@value{AS}} is configured for COFF or ELF output,
2248 this option is only useful if you use sections named @samp{.text} and
2253 @option{-R} is not supported for any of the HPPA targets. Using
2254 @option{-R} generates a warning from @command{@value{AS}}.
2258 @section Display Assembly Statistics: @option{--statistics}
2260 @kindex --statistics
2261 @cindex statistics, about assembly
2262 @cindex time, total for assembly
2263 @cindex space used, maximum for assembly
2264 Use @samp{--statistics} to display two statistics about the resources used by
2265 @command{@value{AS}}: the maximum amount of space allocated during the assembly
2266 (in bytes), and the total execution time taken for the assembly (in @sc{cpu}
2269 @node traditional-format
2270 @section Compatible Output: @option{--traditional-format}
2272 @kindex --traditional-format
2273 For some targets, the output of @command{@value{AS}} is different in some ways
2274 from the output of some existing assembler. This switch requests
2275 @command{@value{AS}} to use the traditional format instead.
2277 For example, it disables the exception frame optimizations which
2278 @command{@value{AS}} normally does by default on @code{@value{GCC}} output.
2281 @section Announce Version: @option{-v}
2285 @cindex assembler version
2286 @cindex version of assembler
2287 You can find out what version of as is running by including the
2288 option @samp{-v} (which you can also spell as @samp{-version}) on the
2292 @section Control Warnings: @option{-W}, @option{--warn}, @option{--no-warn}, @option{--fatal-warnings}
2294 @command{@value{AS}} should never give a warning or error message when
2295 assembling compiler output. But programs written by people often
2296 cause @command{@value{AS}} to give a warning that a particular assumption was
2297 made. All such warnings are directed to the standard error file.
2301 @cindex suppressing warnings
2302 @cindex warnings, suppressing
2303 If you use the @option{-W} and @option{--no-warn} options, no warnings are issued.
2304 This only affects the warning messages: it does not change any particular of
2305 how @command{@value{AS}} assembles your file. Errors, which stop the assembly,
2308 @kindex --fatal-warnings
2309 @cindex errors, caused by warnings
2310 @cindex warnings, causing error
2311 If you use the @option{--fatal-warnings} option, @command{@value{AS}} considers
2312 files that generate warnings to be in error.
2315 @cindex warnings, switching on
2316 You can switch these options off again by specifying @option{--warn}, which
2317 causes warnings to be output as usual.
2320 @section Generate Object File in Spite of Errors: @option{-Z}
2321 @cindex object file, after errors
2322 @cindex errors, continuing after
2323 After an error message, @command{@value{AS}} normally produces no output. If for
2324 some reason you are interested in object file output even after
2325 @command{@value{AS}} gives an error message on your program, use the @samp{-Z}
2326 option. If there are any errors, @command{@value{AS}} continues anyways, and
2327 writes an object file after a final warning message of the form @samp{@var{n}
2328 errors, @var{m} warnings, generating bad object file.}
2333 @cindex machine-independent syntax
2334 @cindex syntax, machine-independent
2335 This chapter describes the machine-independent syntax allowed in a
2336 source file. @command{@value{AS}} syntax is similar to what many other
2337 assemblers use; it is inspired by the BSD 4.2
2342 assembler, except that @command{@value{AS}} does not assemble Vax bit-fields.
2346 * Preprocessing:: Preprocessing
2347 * Whitespace:: Whitespace
2348 * Comments:: Comments
2349 * Symbol Intro:: Symbols
2350 * Statements:: Statements
2351 * Constants:: Constants
2355 @section Preprocessing
2357 @cindex preprocessing
2358 The @command{@value{AS}} internal preprocessor:
2360 @cindex whitespace, removed by preprocessor
2362 adjusts and removes extra whitespace. It leaves one space or tab before
2363 the keywords on a line, and turns any other whitespace on the line into
2366 @cindex comments, removed by preprocessor
2368 removes all comments, replacing them with a single space, or an
2369 appropriate number of newlines.
2371 @cindex constants, converted by preprocessor
2373 converts character constants into the appropriate numeric values.
2376 It does not do macro processing, include file handling, or
2377 anything else you may get from your C compiler's preprocessor. You can
2378 do include file processing with the @code{.include} directive
2379 (@pxref{Include,,@code{.include}}). You can use the @sc{gnu} C compiler driver
2380 to get other ``CPP'' style preprocessing by giving the input file a
2381 @samp{.S} suffix. @xref{Overall Options, ,Options Controlling the Kind of
2382 Output, gcc.info, Using GNU CC}.
2384 Excess whitespace, comments, and character constants
2385 cannot be used in the portions of the input text that are not
2388 @cindex turning preprocessing on and off
2389 @cindex preprocessing, turning on and off
2392 If the first line of an input file is @code{#NO_APP} or if you use the
2393 @samp{-f} option, whitespace and comments are not removed from the input file.
2394 Within an input file, you can ask for whitespace and comment removal in
2395 specific portions of the by putting a line that says @code{#APP} before the
2396 text that may contain whitespace or comments, and putting a line that says
2397 @code{#NO_APP} after this text. This feature is mainly intend to support
2398 @code{asm} statements in compilers whose output is otherwise free of comments
2405 @dfn{Whitespace} is one or more blanks or tabs, in any order.
2406 Whitespace is used to separate symbols, and to make programs neater for
2407 people to read. Unless within character constants
2408 (@pxref{Characters,,Character Constants}), any whitespace means the same
2409 as exactly one space.
2415 There are two ways of rendering comments to @command{@value{AS}}. In both
2416 cases the comment is equivalent to one space.
2418 Anything from @samp{/*} through the next @samp{*/} is a comment.
2419 This means you may not nest these comments.
2423 The only way to include a newline ('\n') in a comment
2424 is to use this sort of comment.
2427 /* This sort of comment does not nest. */
2430 @cindex line comment character
2431 Anything from a @dfn{line comment} character up to the next newline is
2432 considered a comment and is ignored. The line comment character is target
2433 specific, and some targets multiple comment characters. Some targets also have
2434 line comment characters that only work if they are the first character on a
2435 line. Some targets use a sequence of two characters to introduce a line
2436 comment. Some targets can also change their line comment characters depending
2437 upon command line options that have been used. For more details see the
2438 @emph{Syntax} section in the documentation for individual targets.
2440 If the line comment character is the hash sign (@samp{#}) then it still has the
2441 special ability to enable and disable preprocessing (@pxref{Preprocessing}) and
2442 to specify logical line numbers:
2445 @cindex lines starting with @code{#}
2446 @cindex logical line numbers
2447 To be compatible with past assemblers, lines that begin with @samp{#} have a
2448 special interpretation. Following the @samp{#} should be an absolute
2449 expression (@pxref{Expressions}): the logical line number of the @emph{next}
2450 line. Then a string (@pxref{Strings, ,Strings}) is allowed: if present it is a
2451 new logical file name. The rest of the line, if any, should be whitespace.
2453 If the first non-whitespace characters on the line are not numeric,
2454 the line is ignored. (Just like a comment.)
2457 # This is an ordinary comment.
2458 # 42-6 "new_file_name" # New logical file name
2459 # This is logical line # 36.
2461 This feature is deprecated, and may disappear from future versions
2462 of @command{@value{AS}}.
2467 @cindex characters used in symbols
2468 @ifclear SPECIAL-SYMS
2469 A @dfn{symbol} is one or more characters chosen from the set of all
2470 letters (both upper and lower case), digits and the three characters
2476 A @dfn{symbol} is one or more characters chosen from the set of all
2477 letters (both upper and lower case), digits and the three characters
2478 @samp{._$}. (Save that, on the H8/300 only, you may not use @samp{$} in
2484 On most machines, you can also use @code{$} in symbol names; exceptions
2485 are noted in @ref{Machine Dependencies}.
2487 No symbol may begin with a digit. Case is significant.
2488 There is no length limit: all characters are significant. Multibyte characters
2489 are supported. Symbols are delimited by characters not in that set, or by the
2490 beginning of a file (since the source program must end with a newline, the end
2491 of a file is not a possible symbol delimiter). @xref{Symbols}.
2492 @cindex length of symbols
2497 @cindex statements, structure of
2498 @cindex line separator character
2499 @cindex statement separator character
2501 A @dfn{statement} ends at a newline character (@samp{\n}) or a
2502 @dfn{line separator character}. The line separator character is target
2503 specific and described in the @emph{Syntax} section of each
2504 target's documentation. Not all targets support a line separator character.
2505 The newline or line separator character is considered to be part of the
2506 preceding statement. Newlines and separators within character constants are an
2507 exception: they do not end statements.
2509 @cindex newline, required at file end
2510 @cindex EOF, newline must precede
2511 It is an error to end any statement with end-of-file: the last
2512 character of any input file should be a newline.@refill
2514 An empty statement is allowed, and may include whitespace. It is ignored.
2516 @cindex instructions and directives
2517 @cindex directives and instructions
2518 @c "key symbol" is not used elsewhere in the document; seems pedantic to
2519 @c @defn{} it in that case, as was done previously... doc@cygnus.com,
2521 A statement begins with zero or more labels, optionally followed by a
2522 key symbol which determines what kind of statement it is. The key
2523 symbol determines the syntax of the rest of the statement. If the
2524 symbol begins with a dot @samp{.} then the statement is an assembler
2525 directive: typically valid for any computer. If the symbol begins with
2526 a letter the statement is an assembly language @dfn{instruction}: it
2527 assembles into a machine language instruction.
2529 Different versions of @command{@value{AS}} for different computers
2530 recognize different instructions. In fact, the same symbol may
2531 represent a different instruction in a different computer's assembly
2535 @cindex @code{:} (label)
2536 @cindex label (@code{:})
2537 A label is a symbol immediately followed by a colon (@code{:}).
2538 Whitespace before a label or after a colon is permitted, but you may not
2539 have whitespace between a label's symbol and its colon. @xref{Labels}.
2542 For HPPA targets, labels need not be immediately followed by a colon, but
2543 the definition of a label must begin in column zero. This also implies that
2544 only one label may be defined on each line.
2548 label: .directive followed by something
2549 another_label: # This is an empty statement.
2550 instruction operand_1, operand_2, @dots{}
2557 A constant is a number, written so that its value is known by
2558 inspection, without knowing any context. Like this:
2561 .byte 74, 0112, 092, 0x4A, 0X4a, 'J, '\J # All the same value.
2562 .ascii "Ring the bell\7" # A string constant.
2563 .octa 0x123456789abcdef0123456789ABCDEF0 # A bignum.
2564 .float 0f-314159265358979323846264338327\
2565 95028841971.693993751E-40 # - pi, a flonum.
2570 * Characters:: Character Constants
2571 * Numbers:: Number Constants
2575 @subsection Character Constants
2577 @cindex character constants
2578 @cindex constants, character
2579 There are two kinds of character constants. A @dfn{character} stands
2580 for one character in one byte and its value may be used in
2581 numeric expressions. String constants (properly called string
2582 @emph{literals}) are potentially many bytes and their values may not be
2583 used in arithmetic expressions.
2587 * Chars:: Characters
2591 @subsubsection Strings
2593 @cindex string constants
2594 @cindex constants, string
2595 A @dfn{string} is written between double-quotes. It may contain
2596 double-quotes or null characters. The way to get special characters
2597 into a string is to @dfn{escape} these characters: precede them with
2598 a backslash @samp{\} character. For example @samp{\\} represents
2599 one backslash: the first @code{\} is an escape which tells
2600 @command{@value{AS}} to interpret the second character literally as a backslash
2601 (which prevents @command{@value{AS}} from recognizing the second @code{\} as an
2602 escape character). The complete list of escapes follows.
2604 @cindex escape codes, character
2605 @cindex character escape codes
2608 @c Mnemonic for ACKnowledge; for ASCII this is octal code 007.
2610 @cindex @code{\b} (backspace character)
2611 @cindex backspace (@code{\b})
2613 Mnemonic for backspace; for ASCII this is octal code 010.
2616 @c Mnemonic for EOText; for ASCII this is octal code 004.
2618 @cindex @code{\f} (formfeed character)
2619 @cindex formfeed (@code{\f})
2621 Mnemonic for FormFeed; for ASCII this is octal code 014.
2623 @cindex @code{\n} (newline character)
2624 @cindex newline (@code{\n})
2626 Mnemonic for newline; for ASCII this is octal code 012.
2629 @c Mnemonic for prefix; for ASCII this is octal code 033, usually known as @code{escape}.
2631 @cindex @code{\r} (carriage return character)
2632 @cindex carriage return (@code{\r})
2634 Mnemonic for carriage-Return; for ASCII this is octal code 015.
2637 @c Mnemonic for space; for ASCII this is octal code 040. Included for compliance with
2638 @c other assemblers.
2640 @cindex @code{\t} (tab)
2641 @cindex tab (@code{\t})
2643 Mnemonic for horizontal Tab; for ASCII this is octal code 011.
2646 @c Mnemonic for Vertical tab; for ASCII this is octal code 013.
2647 @c @item \x @var{digit} @var{digit} @var{digit}
2648 @c A hexadecimal character code. The numeric code is 3 hexadecimal digits.
2650 @cindex @code{\@var{ddd}} (octal character code)
2651 @cindex octal character code (@code{\@var{ddd}})
2652 @item \ @var{digit} @var{digit} @var{digit}
2653 An octal character code. The numeric code is 3 octal digits.
2654 For compatibility with other Unix systems, 8 and 9 are accepted as digits:
2655 for example, @code{\008} has the value 010, and @code{\009} the value 011.
2657 @cindex @code{\@var{xd...}} (hex character code)
2658 @cindex hex character code (@code{\@var{xd...}})
2659 @item \@code{x} @var{hex-digits...}
2660 A hex character code. All trailing hex digits are combined. Either upper or
2661 lower case @code{x} works.
2663 @cindex @code{\\} (@samp{\} character)
2664 @cindex backslash (@code{\\})
2666 Represents one @samp{\} character.
2669 @c Represents one @samp{'} (accent acute) character.
2670 @c This is needed in single character literals
2671 @c (@xref{Characters,,Character Constants}.) to represent
2674 @cindex @code{\"} (doublequote character)
2675 @cindex doublequote (@code{\"})
2677 Represents one @samp{"} character. Needed in strings to represent
2678 this character, because an unescaped @samp{"} would end the string.
2680 @item \ @var{anything-else}
2681 Any other character when escaped by @kbd{\} gives a warning, but
2682 assembles as if the @samp{\} was not present. The idea is that if
2683 you used an escape sequence you clearly didn't want the literal
2684 interpretation of the following character. However @command{@value{AS}} has no
2685 other interpretation, so @command{@value{AS}} knows it is giving you the wrong
2686 code and warns you of the fact.
2689 Which characters are escapable, and what those escapes represent,
2690 varies widely among assemblers. The current set is what we think
2691 the BSD 4.2 assembler recognizes, and is a subset of what most C
2692 compilers recognize. If you are in doubt, do not use an escape
2696 @subsubsection Characters
2698 @cindex single character constant
2699 @cindex character, single
2700 @cindex constant, single character
2701 A single character may be written as a single quote immediately
2702 followed by that character. The same escapes apply to characters as
2703 to strings. So if you want to write the character backslash, you
2704 must write @kbd{'\\} where the first @code{\} escapes the second
2705 @code{\}. As you can see, the quote is an acute accent, not a
2706 grave accent. A newline
2708 @ifclear abnormal-separator
2709 (or semicolon @samp{;})
2711 @ifset abnormal-separator
2713 (or dollar sign @samp{$}, for the H8/300; or semicolon @samp{;} for the
2718 immediately following an acute accent is taken as a literal character
2719 and does not count as the end of a statement. The value of a character
2720 constant in a numeric expression is the machine's byte-wide code for
2721 that character. @command{@value{AS}} assumes your character code is ASCII:
2722 @kbd{'A} means 65, @kbd{'B} means 66, and so on. @refill
2725 @subsection Number Constants
2727 @cindex constants, number
2728 @cindex number constants
2729 @command{@value{AS}} distinguishes three kinds of numbers according to how they
2730 are stored in the target machine. @emph{Integers} are numbers that
2731 would fit into an @code{int} in the C language. @emph{Bignums} are
2732 integers, but they are stored in more than 32 bits. @emph{Flonums}
2733 are floating point numbers, described below.
2736 * Integers:: Integers
2741 * Bit Fields:: Bit Fields
2747 @subsubsection Integers
2749 @cindex constants, integer
2751 @cindex binary integers
2752 @cindex integers, binary
2753 A binary integer is @samp{0b} or @samp{0B} followed by zero or more of
2754 the binary digits @samp{01}.
2756 @cindex octal integers
2757 @cindex integers, octal
2758 An octal integer is @samp{0} followed by zero or more of the octal
2759 digits (@samp{01234567}).
2761 @cindex decimal integers
2762 @cindex integers, decimal
2763 A decimal integer starts with a non-zero digit followed by zero or
2764 more digits (@samp{0123456789}).
2766 @cindex hexadecimal integers
2767 @cindex integers, hexadecimal
2768 A hexadecimal integer is @samp{0x} or @samp{0X} followed by one or
2769 more hexadecimal digits chosen from @samp{0123456789abcdefABCDEF}.
2771 Integers have the usual values. To denote a negative integer, use
2772 the prefix operator @samp{-} discussed under expressions
2773 (@pxref{Prefix Ops,,Prefix Operators}).
2776 @subsubsection Bignums
2779 @cindex constants, bignum
2780 A @dfn{bignum} has the same syntax and semantics as an integer
2781 except that the number (or its negative) takes more than 32 bits to
2782 represent in binary. The distinction is made because in some places
2783 integers are permitted while bignums are not.
2786 @subsubsection Flonums
2788 @cindex floating point numbers
2789 @cindex constants, floating point
2791 @cindex precision, floating point
2792 A @dfn{flonum} represents a floating point number. The translation is
2793 indirect: a decimal floating point number from the text is converted by
2794 @command{@value{AS}} to a generic binary floating point number of more than
2795 sufficient precision. This generic floating point number is converted
2796 to a particular computer's floating point format (or formats) by a
2797 portion of @command{@value{AS}} specialized to that computer.
2799 A flonum is written by writing (in order)
2804 (@samp{0} is optional on the HPPA.)
2808 A letter, to tell @command{@value{AS}} the rest of the number is a flonum.
2810 @kbd{e} is recommended. Case is not important.
2812 @c FIXME: verify if flonum syntax really this vague for most cases
2813 (Any otherwise illegal letter works here, but that might be changed. Vax BSD
2814 4.2 assembler seems to allow any of @samp{defghDEFGH}.)
2817 On the H8/300, Renesas / SuperH SH,
2818 and AMD 29K architectures, the letter must be
2819 one of the letters @samp{DFPRSX} (in upper or lower case).
2821 On the ARC, the letter must be one of the letters @samp{DFRS}
2822 (in upper or lower case).
2824 On the Intel 960 architecture, the letter must be
2825 one of the letters @samp{DFT} (in upper or lower case).
2827 On the HPPA architecture, the letter must be @samp{E} (upper case only).
2831 One of the letters @samp{DFRS} (in upper or lower case).
2834 One of the letters @samp{DFPRSX} (in upper or lower case).
2837 The letter @samp{E} (upper case only).
2840 One of the letters @samp{DFT} (in upper or lower case).
2845 An optional sign: either @samp{+} or @samp{-}.
2848 An optional @dfn{integer part}: zero or more decimal digits.
2851 An optional @dfn{fractional part}: @samp{.} followed by zero
2852 or more decimal digits.
2855 An optional exponent, consisting of:
2859 An @samp{E} or @samp{e}.
2860 @c I can't find a config where "EXP_CHARS" is other than 'eE', but in
2861 @c principle this can perfectly well be different on different targets.
2863 Optional sign: either @samp{+} or @samp{-}.
2865 One or more decimal digits.
2870 At least one of the integer part or the fractional part must be
2871 present. The floating point number has the usual base-10 value.
2873 @command{@value{AS}} does all processing using integers. Flonums are computed
2874 independently of any floating point hardware in the computer running
2875 @command{@value{AS}}.
2879 @c Bit fields are written as a general facility but are also controlled
2880 @c by a conditional-compilation flag---which is as of now (21mar91)
2881 @c turned on only by the i960 config of GAS.
2883 @subsubsection Bit Fields
2886 @cindex constants, bit field
2887 You can also define numeric constants as @dfn{bit fields}.
2888 Specify two numbers separated by a colon---
2890 @var{mask}:@var{value}
2893 @command{@value{AS}} applies a bitwise @sc{and} between @var{mask} and
2896 The resulting number is then packed
2898 @c this conditional paren in case bit fields turned on elsewhere than 960
2899 (in host-dependent byte order)
2901 into a field whose width depends on which assembler directive has the
2902 bit-field as its argument. Overflow (a result from the bitwise and
2903 requiring more binary digits to represent) is not an error; instead,
2904 more constants are generated, of the specified width, beginning with the
2905 least significant digits.@refill
2907 The directives @code{.byte}, @code{.hword}, @code{.int}, @code{.long},
2908 @code{.short}, and @code{.word} accept bit-field arguments.
2913 @chapter Sections and Relocation
2918 * Secs Background:: Background
2919 * Ld Sections:: Linker Sections
2920 * As Sections:: Assembler Internal Sections
2921 * Sub-Sections:: Sub-Sections
2925 @node Secs Background
2928 Roughly, a section is a range of addresses, with no gaps; all data
2929 ``in'' those addresses is treated the same for some particular purpose.
2930 For example there may be a ``read only'' section.
2932 @cindex linker, and assembler
2933 @cindex assembler, and linker
2934 The linker @code{@value{LD}} reads many object files (partial programs) and
2935 combines their contents to form a runnable program. When @command{@value{AS}}
2936 emits an object file, the partial program is assumed to start at address 0.
2937 @code{@value{LD}} assigns the final addresses for the partial program, so that
2938 different partial programs do not overlap. This is actually an
2939 oversimplification, but it suffices to explain how @command{@value{AS}} uses
2942 @code{@value{LD}} moves blocks of bytes of your program to their run-time
2943 addresses. These blocks slide to their run-time addresses as rigid
2944 units; their length does not change and neither does the order of bytes
2945 within them. Such a rigid unit is called a @emph{section}. Assigning
2946 run-time addresses to sections is called @dfn{relocation}. It includes
2947 the task of adjusting mentions of object-file addresses so they refer to
2948 the proper run-time addresses.
2950 For the H8/300, and for the Renesas / SuperH SH,
2951 @command{@value{AS}} pads sections if needed to
2952 ensure they end on a word (sixteen bit) boundary.
2955 @cindex standard assembler sections
2956 An object file written by @command{@value{AS}} has at least three sections, any
2957 of which may be empty. These are named @dfn{text}, @dfn{data} and
2962 When it generates COFF or ELF output,
2964 @command{@value{AS}} can also generate whatever other named sections you specify
2965 using the @samp{.section} directive (@pxref{Section,,@code{.section}}).
2966 If you do not use any directives that place output in the @samp{.text}
2967 or @samp{.data} sections, these sections still exist, but are empty.
2972 When @command{@value{AS}} generates SOM or ELF output for the HPPA,
2974 @command{@value{AS}} can also generate whatever other named sections you
2975 specify using the @samp{.space} and @samp{.subspace} directives. See
2976 @cite{HP9000 Series 800 Assembly Language Reference Manual}
2977 (HP 92432-90001) for details on the @samp{.space} and @samp{.subspace}
2978 assembler directives.
2981 Additionally, @command{@value{AS}} uses different names for the standard
2982 text, data, and bss sections when generating SOM output. Program text
2983 is placed into the @samp{$CODE$} section, data into @samp{$DATA$}, and
2984 BSS into @samp{$BSS$}.
2988 Within the object file, the text section starts at address @code{0}, the
2989 data section follows, and the bss section follows the data section.
2992 When generating either SOM or ELF output files on the HPPA, the text
2993 section starts at address @code{0}, the data section at address
2994 @code{0x4000000}, and the bss section follows the data section.
2997 To let @code{@value{LD}} know which data changes when the sections are
2998 relocated, and how to change that data, @command{@value{AS}} also writes to the
2999 object file details of the relocation needed. To perform relocation
3000 @code{@value{LD}} must know, each time an address in the object
3004 Where in the object file is the beginning of this reference to
3007 How long (in bytes) is this reference?
3009 Which section does the address refer to? What is the numeric value of
3011 (@var{address}) @minus{} (@var{start-address of section})?
3014 Is the reference to an address ``Program-Counter relative''?
3017 @cindex addresses, format of
3018 @cindex section-relative addressing
3019 In fact, every address @command{@value{AS}} ever uses is expressed as
3021 (@var{section}) + (@var{offset into section})
3024 Further, most expressions @command{@value{AS}} computes have this section-relative
3027 (For some object formats, such as SOM for the HPPA, some expressions are
3028 symbol-relative instead.)
3031 In this manual we use the notation @{@var{secname} @var{N}@} to mean ``offset
3032 @var{N} into section @var{secname}.''
3034 Apart from text, data and bss sections you need to know about the
3035 @dfn{absolute} section. When @code{@value{LD}} mixes partial programs,
3036 addresses in the absolute section remain unchanged. For example, address
3037 @code{@{absolute 0@}} is ``relocated'' to run-time address 0 by
3038 @code{@value{LD}}. Although the linker never arranges two partial programs'
3039 data sections with overlapping addresses after linking, @emph{by definition}
3040 their absolute sections must overlap. Address @code{@{absolute@ 239@}} in one
3041 part of a program is always the same address when the program is running as
3042 address @code{@{absolute@ 239@}} in any other part of the program.
3044 The idea of sections is extended to the @dfn{undefined} section. Any
3045 address whose section is unknown at assembly time is by definition
3046 rendered @{undefined @var{U}@}---where @var{U} is filled in later.
3047 Since numbers are always defined, the only way to generate an undefined
3048 address is to mention an undefined symbol. A reference to a named
3049 common block would be such a symbol: its value is unknown at assembly
3050 time so it has section @emph{undefined}.
3052 By analogy the word @emph{section} is used to describe groups of sections in
3053 the linked program. @code{@value{LD}} puts all partial programs' text
3054 sections in contiguous addresses in the linked program. It is
3055 customary to refer to the @emph{text section} of a program, meaning all
3056 the addresses of all partial programs' text sections. Likewise for
3057 data and bss sections.
3059 Some sections are manipulated by @code{@value{LD}}; others are invented for
3060 use of @command{@value{AS}} and have no meaning except during assembly.
3063 @section Linker Sections
3064 @code{@value{LD}} deals with just four kinds of sections, summarized below.
3069 @cindex named sections
3070 @cindex sections, named
3071 @item named sections
3074 @cindex text section
3075 @cindex data section
3079 These sections hold your program. @command{@value{AS}} and @code{@value{LD}} treat them as
3080 separate but equal sections. Anything you can say of one section is
3083 When the program is running, however, it is
3084 customary for the text section to be unalterable. The
3085 text section is often shared among processes: it contains
3086 instructions, constants and the like. The data section of a running
3087 program is usually alterable: for example, C variables would be stored
3088 in the data section.
3093 This section contains zeroed bytes when your program begins running. It
3094 is used to hold uninitialized variables or common storage. The length of
3095 each partial program's bss section is important, but because it starts
3096 out containing zeroed bytes there is no need to store explicit zero
3097 bytes in the object file. The bss section was invented to eliminate
3098 those explicit zeros from object files.
3100 @cindex absolute section
3101 @item absolute section
3102 Address 0 of this section is always ``relocated'' to runtime address 0.
3103 This is useful if you want to refer to an address that @code{@value{LD}} must
3104 not change when relocating. In this sense we speak of absolute
3105 addresses being ``unrelocatable'': they do not change during relocation.
3107 @cindex undefined section
3108 @item undefined section
3109 This ``section'' is a catch-all for address references to objects not in
3110 the preceding sections.
3111 @c FIXME: ref to some other doc on obj-file formats could go here.
3114 @cindex relocation example
3115 An idealized example of three relocatable sections follows.
3117 The example uses the traditional section names @samp{.text} and @samp{.data}.
3119 Memory addresses are on the horizontal axis.
3123 @c END TEXI2ROFF-KILL
3126 partial program # 1: |ttttt|dddd|00|
3133 partial program # 2: |TTT|DDD|000|
3136 +--+---+-----+--+----+---+-----+~~
3137 linked program: | |TTT|ttttt| |dddd|DDD|00000|
3138 +--+---+-----+--+----+---+-----+~~
3140 addresses: 0 @dots{}
3147 \line{\it Partial program \#1: \hfil}
3148 \line{\ibox{2.5cm}{\tt text}\ibox{2cm}{\tt data}\ibox{1cm}{\tt bss}\hfil}
3149 \line{\boxit{2.5cm}{\tt ttttt}\boxit{2cm}{\tt dddd}\boxit{1cm}{\tt 00}\hfil}
3151 \line{\it Partial program \#2: \hfil}
3152 \line{\ibox{1cm}{\tt text}\ibox{1.5cm}{\tt data}\ibox{1cm}{\tt bss}\hfil}
3153 \line{\boxit{1cm}{\tt TTT}\boxit{1.5cm}{\tt DDDD}\boxit{1cm}{\tt 000}\hfil}
3155 \line{\it linked program: \hfil}
3156 \line{\ibox{.5cm}{}\ibox{1cm}{\tt text}\ibox{2.5cm}{}\ibox{.75cm}{}\ibox{2cm}{\tt data}\ibox{1.5cm}{}\ibox{2cm}{\tt bss}\hfil}
3157 \line{\boxit{.5cm}{}\boxit{1cm}{\tt TTT}\boxit{2.5cm}{\tt
3158 ttttt}\boxit{.75cm}{}\boxit{2cm}{\tt dddd}\boxit{1.5cm}{\tt
3159 DDDD}\boxit{2cm}{\tt 00000}\ \dots\hfil}
3161 \line{\it addresses: \hfil}
3165 @c END TEXI2ROFF-KILL
3168 @section Assembler Internal Sections
3170 @cindex internal assembler sections
3171 @cindex sections in messages, internal
3172 These sections are meant only for the internal use of @command{@value{AS}}. They
3173 have no meaning at run-time. You do not really need to know about these
3174 sections for most purposes; but they can be mentioned in @command{@value{AS}}
3175 warning messages, so it might be helpful to have an idea of their
3176 meanings to @command{@value{AS}}. These sections are used to permit the
3177 value of every expression in your assembly language program to be a
3178 section-relative address.
3181 @cindex assembler internal logic error
3182 @item ASSEMBLER-INTERNAL-LOGIC-ERROR!
3183 An internal assembler logic error has been found. This means there is a
3184 bug in the assembler.
3186 @cindex expr (internal section)
3188 The assembler stores complex expression internally as combinations of
3189 symbols. When it needs to represent an expression as a symbol, it puts
3190 it in the expr section.
3192 @c FIXME item transfer[t] vector preload
3193 @c FIXME item transfer[t] vector postload
3194 @c FIXME item register
3198 @section Sub-Sections
3200 @cindex numbered subsections
3201 @cindex grouping data
3207 fall into two sections: text and data.
3209 You may have separate groups of
3211 data in named sections
3215 data in named sections
3221 that you want to end up near to each other in the object file, even though they
3222 are not contiguous in the assembler source. @command{@value{AS}} allows you to
3223 use @dfn{subsections} for this purpose. Within each section, there can be
3224 numbered subsections with values from 0 to 8192. Objects assembled into the
3225 same subsection go into the object file together with other objects in the same
3226 subsection. For example, a compiler might want to store constants in the text
3227 section, but might not want to have them interspersed with the program being
3228 assembled. In this case, the compiler could issue a @samp{.text 0} before each
3229 section of code being output, and a @samp{.text 1} before each group of
3230 constants being output.
3232 Subsections are optional. If you do not use subsections, everything
3233 goes in subsection number zero.
3236 Each subsection is zero-padded up to a multiple of four bytes.
3237 (Subsections may be padded a different amount on different flavors
3238 of @command{@value{AS}}.)
3242 On the H8/300 platform, each subsection is zero-padded to a word
3243 boundary (two bytes).
3244 The same is true on the Renesas SH.
3247 @c FIXME section padding (alignment)?
3248 @c Rich Pixley says padding here depends on target obj code format; that
3249 @c doesn't seem particularly useful to say without further elaboration,
3250 @c so for now I say nothing about it. If this is a generic BFD issue,
3251 @c these paragraphs might need to vanish from this manual, and be
3252 @c discussed in BFD chapter of binutils (or some such).
3256 Subsections appear in your object file in numeric order, lowest numbered
3257 to highest. (All this to be compatible with other people's assemblers.)
3258 The object file contains no representation of subsections; @code{@value{LD}} and
3259 other programs that manipulate object files see no trace of them.
3260 They just see all your text subsections as a text section, and all your
3261 data subsections as a data section.
3263 To specify which subsection you want subsequent statements assembled
3264 into, use a numeric argument to specify it, in a @samp{.text
3265 @var{expression}} or a @samp{.data @var{expression}} statement.
3268 When generating COFF output, you
3273 can also use an extra subsection
3274 argument with arbitrary named sections: @samp{.section @var{name},
3279 When generating ELF output, you
3284 can also use the @code{.subsection} directive (@pxref{SubSection})
3285 to specify a subsection: @samp{.subsection @var{expression}}.
3287 @var{Expression} should be an absolute expression
3288 (@pxref{Expressions}). If you just say @samp{.text} then @samp{.text 0}
3289 is assumed. Likewise @samp{.data} means @samp{.data 0}. Assembly
3290 begins in @code{text 0}. For instance:
3292 .text 0 # The default subsection is text 0 anyway.
3293 .ascii "This lives in the first text subsection. *"
3295 .ascii "But this lives in the second text subsection."
3297 .ascii "This lives in the data section,"
3298 .ascii "in the first data subsection."
3300 .ascii "This lives in the first text section,"
3301 .ascii "immediately following the asterisk (*)."
3304 Each section has a @dfn{location counter} incremented by one for every byte
3305 assembled into that section. Because subsections are merely a convenience
3306 restricted to @command{@value{AS}} there is no concept of a subsection location
3307 counter. There is no way to directly manipulate a location counter---but the
3308 @code{.align} directive changes it, and any label definition captures its
3309 current value. The location counter of the section where statements are being
3310 assembled is said to be the @dfn{active} location counter.
3313 @section bss Section
3316 @cindex common variable storage
3317 The bss section is used for local common variable storage.
3318 You may allocate address space in the bss section, but you may
3319 not dictate data to load into it before your program executes. When
3320 your program starts running, all the contents of the bss
3321 section are zeroed bytes.
3323 The @code{.lcomm} pseudo-op defines a symbol in the bss section; see
3324 @ref{Lcomm,,@code{.lcomm}}.
3326 The @code{.comm} pseudo-op may be used to declare a common symbol, which is
3327 another form of uninitialized symbol; see @ref{Comm,,@code{.comm}}.
3330 When assembling for a target which supports multiple sections, such as ELF or
3331 COFF, you may switch into the @code{.bss} section and define symbols as usual;
3332 see @ref{Section,,@code{.section}}. You may only assemble zero values into the
3333 section. Typically the section will only contain symbol definitions and
3334 @code{.skip} directives (@pxref{Skip,,@code{.skip}}).
3341 Symbols are a central concept: the programmer uses symbols to name
3342 things, the linker uses symbols to link, and the debugger uses symbols
3346 @cindex debuggers, and symbol order
3347 @emph{Warning:} @command{@value{AS}} does not place symbols in the object file in
3348 the same order they were declared. This may break some debuggers.
3353 * Setting Symbols:: Giving Symbols Other Values
3354 * Symbol Names:: Symbol Names
3355 * Dot:: The Special Dot Symbol
3356 * Symbol Attributes:: Symbol Attributes
3363 A @dfn{label} is written as a symbol immediately followed by a colon
3364 @samp{:}. The symbol then represents the current value of the
3365 active location counter, and is, for example, a suitable instruction
3366 operand. You are warned if you use the same symbol to represent two
3367 different locations: the first definition overrides any other
3371 On the HPPA, the usual form for a label need not be immediately followed by a
3372 colon, but instead must start in column zero. Only one label may be defined on
3373 a single line. To work around this, the HPPA version of @command{@value{AS}} also
3374 provides a special directive @code{.label} for defining labels more flexibly.
3377 @node Setting Symbols
3378 @section Giving Symbols Other Values
3380 @cindex assigning values to symbols
3381 @cindex symbol values, assigning
3382 A symbol can be given an arbitrary value by writing a symbol, followed
3383 by an equals sign @samp{=}, followed by an expression
3384 (@pxref{Expressions}). This is equivalent to using the @code{.set}
3385 directive. @xref{Set,,@code{.set}}. In the same way, using a double
3386 equals sign @samp{=}@samp{=} here represents an equivalent of the
3387 @code{.eqv} directive. @xref{Eqv,,@code{.eqv}}.
3390 Blackfin does not support symbol assignment with @samp{=}.
3394 @section Symbol Names
3396 @cindex symbol names
3397 @cindex names, symbol
3398 @ifclear SPECIAL-SYMS
3399 Symbol names begin with a letter or with one of @samp{._}. On most
3400 machines, you can also use @code{$} in symbol names; exceptions are
3401 noted in @ref{Machine Dependencies}. That character may be followed by any
3402 string of digits, letters, dollar signs (unless otherwise noted for a
3403 particular target machine), and underscores.
3407 Symbol names begin with a letter or with one of @samp{._}. On the
3408 Renesas SH you can also use @code{$} in symbol names. That
3409 character may be followed by any string of digits, letters, dollar signs (save
3410 on the H8/300), and underscores.
3414 Case of letters is significant: @code{foo} is a different symbol name
3417 Multibyte characters are supported. To generate a symbol name containing
3418 multibyte characters enclose it within double quotes and use escape codes. cf
3419 @xref{Strings}. Generating a multibyte symbol name from a label is not
3420 currently supported.
3422 Each symbol has exactly one name. Each name in an assembly language program
3423 refers to exactly one symbol. You may use that symbol name any number of times
3426 @subheading Local Symbol Names
3428 @cindex local symbol names
3429 @cindex symbol names, local
3430 A local symbol is any symbol beginning with certain local label prefixes.
3431 By default, the local label prefix is @samp{.L} for ELF systems or
3432 @samp{L} for traditional a.out systems, but each target may have its own
3433 set of local label prefixes.
3435 On the HPPA local symbols begin with @samp{L$}.
3438 Local symbols are defined and used within the assembler, but they are
3439 normally not saved in object files. Thus, they are not visible when debugging.
3440 You may use the @samp{-L} option (@pxref{L, ,Include Local Symbols:
3441 @option{-L}}) to retain the local symbols in the object files.
3443 @subheading Local Labels
3445 @cindex local labels
3446 @cindex temporary symbol names
3447 @cindex symbol names, temporary
3448 Local labels help compilers and programmers use names temporarily.
3449 They create symbols which are guaranteed to be unique over the entire scope of
3450 the input source code and which can be referred to by a simple notation.
3451 To define a local label, write a label of the form @samp{@b{N}:} (where @b{N}
3452 represents any positive integer). To refer to the most recent previous
3453 definition of that label write @samp{@b{N}b}, using the same number as when
3454 you defined the label. To refer to the next definition of a local label, write
3455 @samp{@b{N}f}---the @samp{b} stands for ``backwards'' and the @samp{f} stands
3458 There is no restriction on how you can use these labels, and you can reuse them
3459 too. So that it is possible to repeatedly define the same local label (using
3460 the same number @samp{@b{N}}), although you can only refer to the most recently
3461 defined local label of that number (for a backwards reference) or the next
3462 definition of a specific local label for a forward reference. It is also worth
3463 noting that the first 10 local labels (@samp{@b{0:}}@dots{}@samp{@b{9:}}) are
3464 implemented in a slightly more efficient manner than the others.
3475 Which is the equivalent of:
3478 label_1: branch label_3
3479 label_2: branch label_1
3480 label_3: branch label_4
3481 label_4: branch label_3
3484 Local label names are only a notational device. They are immediately
3485 transformed into more conventional symbol names before the assembler uses them.
3486 The symbol names are stored in the symbol table, appear in error messages, and
3487 are optionally emitted to the object file. The names are constructed using
3491 @item @emph{local label prefix}
3492 All local symbols begin with the system-specific local label prefix.
3493 Normally both @command{@value{AS}} and @code{@value{LD}} forget symbols
3494 that start with the local label prefix. These labels are
3495 used for symbols you are never intended to see. If you use the
3496 @samp{-L} option then @command{@value{AS}} retains these symbols in the
3497 object file. If you also instruct @code{@value{LD}} to retain these symbols,
3498 you may use them in debugging.
3501 This is the number that was used in the local label definition. So if the
3502 label is written @samp{55:} then the number is @samp{55}.
3505 This unusual character is included so you do not accidentally invent a symbol
3506 of the same name. The character has ASCII value of @samp{\002} (control-B).
3508 @item @emph{ordinal number}
3509 This is a serial number to keep the labels distinct. The first definition of
3510 @samp{0:} gets the number @samp{1}. The 15th definition of @samp{0:} gets the
3511 number @samp{15}, and so on. Likewise the first definition of @samp{1:} gets
3512 the number @samp{1} and its 15th definition gets @samp{15} as well.
3515 So for example, the first @code{1:} may be named @code{.L1@kbd{C-B}1}, and
3516 the 44th @code{3:} may be named @code{.L3@kbd{C-B}44}.
3518 @subheading Dollar Local Labels
3519 @cindex dollar local symbols
3521 @code{@value{AS}} also supports an even more local form of local labels called
3522 dollar labels. These labels go out of scope (i.e., they become undefined) as
3523 soon as a non-local label is defined. Thus they remain valid for only a small
3524 region of the input source code. Normal local labels, by contrast, remain in
3525 scope for the entire file, or until they are redefined by another occurrence of
3526 the same local label.
3528 Dollar labels are defined in exactly the same way as ordinary local labels,
3529 except that they have a dollar sign suffix to their numeric value, e.g.,
3532 They can also be distinguished from ordinary local labels by their transformed
3533 names which use ASCII character @samp{\001} (control-A) as the magic character
3534 to distinguish them from ordinary labels. For example, the fifth definition of
3535 @samp{6$} may be named @samp{.L6@kbd{C-A}5}.
3538 @section The Special Dot Symbol
3540 @cindex dot (symbol)
3541 @cindex @code{.} (symbol)
3542 @cindex current address
3543 @cindex location counter
3544 The special symbol @samp{.} refers to the current address that
3545 @command{@value{AS}} is assembling into. Thus, the expression @samp{melvin:
3546 .long .} defines @code{melvin} to contain its own address.
3547 Assigning a value to @code{.} is treated the same as a @code{.org}
3549 @ifclear no-space-dir
3550 Thus, the expression @samp{.=.+4} is the same as saying
3554 @node Symbol Attributes
3555 @section Symbol Attributes
3557 @cindex symbol attributes
3558 @cindex attributes, symbol
3559 Every symbol has, as well as its name, the attributes ``Value'' and
3560 ``Type''. Depending on output format, symbols can also have auxiliary
3563 The detailed definitions are in @file{a.out.h}.
3566 If you use a symbol without defining it, @command{@value{AS}} assumes zero for
3567 all these attributes, and probably won't warn you. This makes the
3568 symbol an externally defined symbol, which is generally what you
3572 * Symbol Value:: Value
3573 * Symbol Type:: Type
3576 * a.out Symbols:: Symbol Attributes: @code{a.out}
3580 * a.out Symbols:: Symbol Attributes: @code{a.out}
3583 * a.out Symbols:: Symbol Attributes: @code{a.out}, @code{b.out}
3588 * COFF Symbols:: Symbol Attributes for COFF
3591 * SOM Symbols:: Symbol Attributes for SOM
3598 @cindex value of a symbol
3599 @cindex symbol value
3600 The value of a symbol is (usually) 32 bits. For a symbol which labels a
3601 location in the text, data, bss or absolute sections the value is the
3602 number of addresses from the start of that section to the label.
3603 Naturally for text, data and bss sections the value of a symbol changes
3604 as @code{@value{LD}} changes section base addresses during linking. Absolute
3605 symbols' values do not change during linking: that is why they are
3608 The value of an undefined symbol is treated in a special way. If it is
3609 0 then the symbol is not defined in this assembler source file, and
3610 @code{@value{LD}} tries to determine its value from other files linked into the
3611 same program. You make this kind of symbol simply by mentioning a symbol
3612 name without defining it. A non-zero value represents a @code{.comm}
3613 common declaration. The value is how much common storage to reserve, in
3614 bytes (addresses). The symbol refers to the first address of the
3620 @cindex type of a symbol
3622 The type attribute of a symbol contains relocation (section)
3623 information, any flag settings indicating that a symbol is external, and
3624 (optionally), other information for linkers and debuggers. The exact
3625 format depends on the object-code output format in use.
3630 @c The following avoids a "widow" subsection title. @group would be
3631 @c better if it were available outside examples.
3634 @subsection Symbol Attributes: @code{a.out}, @code{b.out}
3636 @cindex @code{b.out} symbol attributes
3637 @cindex symbol attributes, @code{b.out}
3638 These symbol attributes appear only when @command{@value{AS}} is configured for
3639 one of the Berkeley-descended object output formats---@code{a.out} or
3645 @subsection Symbol Attributes: @code{a.out}
3647 @cindex @code{a.out} symbol attributes
3648 @cindex symbol attributes, @code{a.out}
3654 @subsection Symbol Attributes: @code{a.out}
3656 @cindex @code{a.out} symbol attributes
3657 @cindex symbol attributes, @code{a.out}
3661 * Symbol Desc:: Descriptor
3662 * Symbol Other:: Other
3666 @subsubsection Descriptor
3668 @cindex descriptor, of @code{a.out} symbol
3669 This is an arbitrary 16-bit value. You may establish a symbol's
3670 descriptor value by using a @code{.desc} statement
3671 (@pxref{Desc,,@code{.desc}}). A descriptor value means nothing to
3672 @command{@value{AS}}.
3675 @subsubsection Other
3677 @cindex other attribute, of @code{a.out} symbol
3678 This is an arbitrary 8-bit value. It means nothing to @command{@value{AS}}.
3683 @subsection Symbol Attributes for COFF
3685 @cindex COFF symbol attributes
3686 @cindex symbol attributes, COFF
3688 The COFF format supports a multitude of auxiliary symbol attributes;
3689 like the primary symbol attributes, they are set between @code{.def} and
3690 @code{.endef} directives.
3692 @subsubsection Primary Attributes
3694 @cindex primary attributes, COFF symbols
3695 The symbol name is set with @code{.def}; the value and type,
3696 respectively, with @code{.val} and @code{.type}.
3698 @subsubsection Auxiliary Attributes
3700 @cindex auxiliary attributes, COFF symbols
3701 The @command{@value{AS}} directives @code{.dim}, @code{.line}, @code{.scl},
3702 @code{.size}, @code{.tag}, and @code{.weak} can generate auxiliary symbol
3703 table information for COFF.
3708 @subsection Symbol Attributes for SOM
3710 @cindex SOM symbol attributes
3711 @cindex symbol attributes, SOM
3713 The SOM format for the HPPA supports a multitude of symbol attributes set with
3714 the @code{.EXPORT} and @code{.IMPORT} directives.
3716 The attributes are described in @cite{HP9000 Series 800 Assembly
3717 Language Reference Manual} (HP 92432-90001) under the @code{IMPORT} and
3718 @code{EXPORT} assembler directive documentation.
3722 @chapter Expressions
3726 @cindex numeric values
3727 An @dfn{expression} specifies an address or numeric value.
3728 Whitespace may precede and/or follow an expression.
3730 The result of an expression must be an absolute number, or else an offset into
3731 a particular section. If an expression is not absolute, and there is not
3732 enough information when @command{@value{AS}} sees the expression to know its
3733 section, a second pass over the source program might be necessary to interpret
3734 the expression---but the second pass is currently not implemented.
3735 @command{@value{AS}} aborts with an error message in this situation.
3738 * Empty Exprs:: Empty Expressions
3739 * Integer Exprs:: Integer Expressions
3743 @section Empty Expressions
3745 @cindex empty expressions
3746 @cindex expressions, empty
3747 An empty expression has no value: it is just whitespace or null.
3748 Wherever an absolute expression is required, you may omit the
3749 expression, and @command{@value{AS}} assumes a value of (absolute) 0. This
3750 is compatible with other assemblers.
3753 @section Integer Expressions
3755 @cindex integer expressions
3756 @cindex expressions, integer
3757 An @dfn{integer expression} is one or more @emph{arguments} delimited
3758 by @emph{operators}.
3761 * Arguments:: Arguments
3762 * Operators:: Operators
3763 * Prefix Ops:: Prefix Operators
3764 * Infix Ops:: Infix Operators
3768 @subsection Arguments
3770 @cindex expression arguments
3771 @cindex arguments in expressions
3772 @cindex operands in expressions
3773 @cindex arithmetic operands
3774 @dfn{Arguments} are symbols, numbers or subexpressions. In other
3775 contexts arguments are sometimes called ``arithmetic operands''. In
3776 this manual, to avoid confusing them with the ``instruction operands'' of
3777 the machine language, we use the term ``argument'' to refer to parts of
3778 expressions only, reserving the word ``operand'' to refer only to machine
3779 instruction operands.
3781 Symbols are evaluated to yield @{@var{section} @var{NNN}@} where
3782 @var{section} is one of text, data, bss, absolute,
3783 or undefined. @var{NNN} is a signed, 2's complement 32 bit
3786 Numbers are usually integers.
3788 A number can be a flonum or bignum. In this case, you are warned
3789 that only the low order 32 bits are used, and @command{@value{AS}} pretends
3790 these 32 bits are an integer. You may write integer-manipulating
3791 instructions that act on exotic constants, compatible with other
3794 @cindex subexpressions
3795 Subexpressions are a left parenthesis @samp{(} followed by an integer
3796 expression, followed by a right parenthesis @samp{)}; or a prefix
3797 operator followed by an argument.
3800 @subsection Operators
3802 @cindex operators, in expressions
3803 @cindex arithmetic functions
3804 @cindex functions, in expressions
3805 @dfn{Operators} are arithmetic functions, like @code{+} or @code{%}. Prefix
3806 operators are followed by an argument. Infix operators appear
3807 between their arguments. Operators may be preceded and/or followed by
3811 @subsection Prefix Operator
3813 @cindex prefix operators
3814 @command{@value{AS}} has the following @dfn{prefix operators}. They each take
3815 one argument, which must be absolute.
3817 @c the tex/end tex stuff surrounding this small table is meant to make
3818 @c it align, on the printed page, with the similar table in the next
3819 @c section (which is inside an enumerate).
3821 \global\advance\leftskip by \itemindent
3826 @dfn{Negation}. Two's complement negation.
3828 @dfn{Complementation}. Bitwise not.
3832 \global\advance\leftskip by -\itemindent
3836 @subsection Infix Operators
3838 @cindex infix operators
3839 @cindex operators, permitted arguments
3840 @dfn{Infix operators} take two arguments, one on either side. Operators
3841 have precedence, but operations with equal precedence are performed left
3842 to right. Apart from @code{+} or @option{-}, both arguments must be
3843 absolute, and the result is absolute.
3846 @cindex operator precedence
3847 @cindex precedence of operators
3854 @dfn{Multiplication}.
3857 @dfn{Division}. Truncation is the same as the C operator @samp{/}
3863 @dfn{Shift Left}. Same as the C operator @samp{<<}.
3866 @dfn{Shift Right}. Same as the C operator @samp{>>}.
3870 Intermediate precedence
3875 @dfn{Bitwise Inclusive Or}.
3881 @dfn{Bitwise Exclusive Or}.
3884 @dfn{Bitwise Or Not}.
3891 @cindex addition, permitted arguments
3892 @cindex plus, permitted arguments
3893 @cindex arguments for addition
3895 @dfn{Addition}. If either argument is absolute, the result has the section of
3896 the other argument. You may not add together arguments from different
3899 @cindex subtraction, permitted arguments
3900 @cindex minus, permitted arguments
3901 @cindex arguments for subtraction
3903 @dfn{Subtraction}. If the right argument is absolute, the
3904 result has the section of the left argument.
3905 If both arguments are in the same section, the result is absolute.
3906 You may not subtract arguments from different sections.
3907 @c FIXME is there still something useful to say about undefined - undefined ?
3909 @cindex comparison expressions
3910 @cindex expressions, comparison
3915 @dfn{Is Not Equal To}
3919 @dfn{Is Greater Than}
3921 @dfn{Is Greater Than Or Equal To}
3923 @dfn{Is Less Than Or Equal To}
3925 The comparison operators can be used as infix operators. A true results has a
3926 value of -1 whereas a false result has a value of 0. Note, these operators
3927 perform signed comparisons.
3930 @item Lowest Precedence
3939 These two logical operations can be used to combine the results of sub
3940 expressions. Note, unlike the comparison operators a true result returns a
3941 value of 1 but a false results does still return 0. Also note that the logical
3942 or operator has a slightly lower precedence than logical and.
3947 In short, it's only meaningful to add or subtract the @emph{offsets} in an
3948 address; you can only have a defined section in one of the two arguments.
3951 @chapter Assembler Directives
3953 @cindex directives, machine independent
3954 @cindex pseudo-ops, machine independent
3955 @cindex machine independent directives
3956 All assembler directives have names that begin with a period (@samp{.}).
3957 The rest of the name is letters, usually in lower case.
3959 This chapter discusses directives that are available regardless of the
3960 target machine configuration for the @sc{gnu} assembler.
3962 Some machine configurations provide additional directives.
3963 @xref{Machine Dependencies}.
3966 @ifset machine-directives
3967 @xref{Machine Dependencies}, for additional directives.
3972 * Abort:: @code{.abort}
3974 * ABORT (COFF):: @code{.ABORT}
3977 * Align:: @code{.align @var{abs-expr} , @var{abs-expr}}
3978 * Altmacro:: @code{.altmacro}
3979 * Ascii:: @code{.ascii "@var{string}"}@dots{}
3980 * Asciz:: @code{.asciz "@var{string}"}@dots{}
3981 * Balign:: @code{.balign @var{abs-expr} , @var{abs-expr}}
3982 * Bundle directives:: @code{.bundle_align_mode @var{abs-expr}}, @code{.bundle_lock}, @code{.bundle_unlock}
3983 * Byte:: @code{.byte @var{expressions}}
3984 * CFI directives:: @code{.cfi_startproc [simple]}, @code{.cfi_endproc}, etc.
3985 * Comm:: @code{.comm @var{symbol} , @var{length} }
3986 * Data:: @code{.data @var{subsection}}
3988 * Def:: @code{.def @var{name}}
3991 * Desc:: @code{.desc @var{symbol}, @var{abs-expression}}
3997 * Double:: @code{.double @var{flonums}}
3998 * Eject:: @code{.eject}
3999 * Else:: @code{.else}
4000 * Elseif:: @code{.elseif}
4003 * Endef:: @code{.endef}
4006 * Endfunc:: @code{.endfunc}
4007 * Endif:: @code{.endif}
4008 * Equ:: @code{.equ @var{symbol}, @var{expression}}
4009 * Equiv:: @code{.equiv @var{symbol}, @var{expression}}
4010 * Eqv:: @code{.eqv @var{symbol}, @var{expression}}
4012 * Error:: @code{.error @var{string}}
4013 * Exitm:: @code{.exitm}
4014 * Extern:: @code{.extern}
4015 * Fail:: @code{.fail}
4016 * File:: @code{.file}
4017 * Fill:: @code{.fill @var{repeat} , @var{size} , @var{value}}
4018 * Float:: @code{.float @var{flonums}}
4019 * Func:: @code{.func}
4020 * Global:: @code{.global @var{symbol}}, @code{.globl @var{symbol}}
4022 * Gnu_attribute:: @code{.gnu_attribute @var{tag},@var{value}}
4023 * Hidden:: @code{.hidden @var{names}}
4026 * hword:: @code{.hword @var{expressions}}
4027 * Ident:: @code{.ident}
4028 * If:: @code{.if @var{absolute expression}}
4029 * Incbin:: @code{.incbin "@var{file}"[,@var{skip}[,@var{count}]]}
4030 * Include:: @code{.include "@var{file}"}
4031 * Int:: @code{.int @var{expressions}}
4033 * Internal:: @code{.internal @var{names}}
4036 * Irp:: @code{.irp @var{symbol},@var{values}}@dots{}
4037 * Irpc:: @code{.irpc @var{symbol},@var{values}}@dots{}
4038 * Lcomm:: @code{.lcomm @var{symbol} , @var{length}}
4039 * Lflags:: @code{.lflags}
4040 @ifclear no-line-dir
4041 * Line:: @code{.line @var{line-number}}
4044 * Linkonce:: @code{.linkonce [@var{type}]}
4045 * List:: @code{.list}
4046 * Ln:: @code{.ln @var{line-number}}
4047 * Loc:: @code{.loc @var{fileno} @var{lineno}}
4048 * Loc_mark_labels:: @code{.loc_mark_labels @var{enable}}
4050 * Local:: @code{.local @var{names}}
4053 * Long:: @code{.long @var{expressions}}
4055 * Lsym:: @code{.lsym @var{symbol}, @var{expression}}
4058 * Macro:: @code{.macro @var{name} @var{args}}@dots{}
4059 * MRI:: @code{.mri @var{val}}
4060 * Noaltmacro:: @code{.noaltmacro}
4061 * Nolist:: @code{.nolist}
4062 * Octa:: @code{.octa @var{bignums}}
4063 * Offset:: @code{.offset @var{loc}}
4064 * Org:: @code{.org @var{new-lc}, @var{fill}}
4065 * P2align:: @code{.p2align @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
4067 * PopSection:: @code{.popsection}
4068 * Previous:: @code{.previous}
4071 * Print:: @code{.print @var{string}}
4073 * Protected:: @code{.protected @var{names}}
4076 * Psize:: @code{.psize @var{lines}, @var{columns}}
4077 * Purgem:: @code{.purgem @var{name}}
4079 * PushSection:: @code{.pushsection @var{name}}
4082 * Quad:: @code{.quad @var{bignums}}
4083 * Reloc:: @code{.reloc @var{offset}, @var{reloc_name}[, @var{expression}]}
4084 * Rept:: @code{.rept @var{count}}
4085 * Sbttl:: @code{.sbttl "@var{subheading}"}
4087 * Scl:: @code{.scl @var{class}}
4090 * Section:: @code{.section @var{name}[, @var{flags}]}
4093 * Set:: @code{.set @var{symbol}, @var{expression}}
4094 * Short:: @code{.short @var{expressions}}
4095 * Single:: @code{.single @var{flonums}}
4097 * Size:: @code{.size [@var{name} , @var{expression}]}
4099 @ifclear no-space-dir
4100 * Skip:: @code{.skip @var{size} , @var{fill}}
4103 * Sleb128:: @code{.sleb128 @var{expressions}}
4104 @ifclear no-space-dir
4105 * Space:: @code{.space @var{size} , @var{fill}}
4108 * Stab:: @code{.stabd, .stabn, .stabs}
4111 * String:: @code{.string "@var{str}"}, @code{.string8 "@var{str}"}, @code{.string16 "@var{str}"}, @code{.string32 "@var{str}"}, @code{.string64 "@var{str}"}
4112 * Struct:: @code{.struct @var{expression}}
4114 * SubSection:: @code{.subsection}
4115 * Symver:: @code{.symver @var{name},@var{name2@@nodename}}
4119 * Tag:: @code{.tag @var{structname}}
4122 * Text:: @code{.text @var{subsection}}
4123 * Title:: @code{.title "@var{heading}"}
4125 * Type:: @code{.type <@var{int} | @var{name} , @var{type description}>}
4128 * Uleb128:: @code{.uleb128 @var{expressions}}
4130 * Val:: @code{.val @var{addr}}
4134 * Version:: @code{.version "@var{string}"}
4135 * VTableEntry:: @code{.vtable_entry @var{table}, @var{offset}}
4136 * VTableInherit:: @code{.vtable_inherit @var{child}, @var{parent}}
4139 * Warning:: @code{.warning @var{string}}
4140 * Weak:: @code{.weak @var{names}}
4141 * Weakref:: @code{.weakref @var{alias}, @var{symbol}}
4142 * Word:: @code{.word @var{expressions}}
4143 * Deprecated:: Deprecated Directives
4147 @section @code{.abort}
4149 @cindex @code{abort} directive
4150 @cindex stopping the assembly
4151 This directive stops the assembly immediately. It is for
4152 compatibility with other assemblers. The original idea was that the
4153 assembly language source would be piped into the assembler. If the sender
4154 of the source quit, it could use this directive tells @command{@value{AS}} to
4155 quit also. One day @code{.abort} will not be supported.
4159 @section @code{.ABORT} (COFF)
4161 @cindex @code{ABORT} directive
4162 When producing COFF output, @command{@value{AS}} accepts this directive as a
4163 synonym for @samp{.abort}.
4166 When producing @code{b.out} output, @command{@value{AS}} accepts this directive,
4172 @section @code{.align @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
4174 @cindex padding the location counter
4175 @cindex @code{align} directive
4176 Pad the location counter (in the current subsection) to a particular storage
4177 boundary. The first expression (which must be absolute) is the alignment
4178 required, as described below.
4180 The second expression (also absolute) gives the fill value to be stored in the
4181 padding bytes. It (and the comma) may be omitted. If it is omitted, the
4182 padding bytes are normally zero. However, on some systems, if the section is
4183 marked as containing code and the fill value is omitted, the space is filled
4184 with no-op instructions.
4186 The third expression is also absolute, and is also optional. If it is present,
4187 it is the maximum number of bytes that should be skipped by this alignment
4188 directive. If doing the alignment would require skipping more bytes than the
4189 specified maximum, then the alignment is not done at all. You can omit the
4190 fill value (the second argument) entirely by simply using two commas after the
4191 required alignment; this can be useful if you want the alignment to be filled
4192 with no-op instructions when appropriate.
4194 The way the required alignment is specified varies from system to system.
4195 For the arc, hppa, i386 using ELF, i860, iq2000, m68k, or32,
4196 s390, sparc, tic4x, tic80 and xtensa, the first expression is the
4197 alignment request in bytes. For example @samp{.align 8} advances
4198 the location counter until it is a multiple of 8. If the location counter
4199 is already a multiple of 8, no change is needed. For the tic54x, the
4200 first expression is the alignment request in words.
4202 For other systems, including ppc, i386 using a.out format, arm and
4203 strongarm, it is the
4204 number of low-order zero bits the location counter must have after
4205 advancement. For example @samp{.align 3} advances the location
4206 counter until it a multiple of 8. If the location counter is already a
4207 multiple of 8, no change is needed.
4209 This inconsistency is due to the different behaviors of the various
4210 native assemblers for these systems which GAS must emulate.
4211 GAS also provides @code{.balign} and @code{.p2align} directives,
4212 described later, which have a consistent behavior across all
4213 architectures (but are specific to GAS).
4216 @section @code{.altmacro}
4217 Enable alternate macro mode, enabling:
4220 @item LOCAL @var{name} [ , @dots{} ]
4221 One additional directive, @code{LOCAL}, is available. It is used to
4222 generate a string replacement for each of the @var{name} arguments, and
4223 replace any instances of @var{name} in each macro expansion. The
4224 replacement string is unique in the assembly, and different for each
4225 separate macro expansion. @code{LOCAL} allows you to write macros that
4226 define symbols, without fear of conflict between separate macro expansions.
4228 @item String delimiters
4229 You can write strings delimited in these other ways besides
4230 @code{"@var{string}"}:
4233 @item '@var{string}'
4234 You can delimit strings with single-quote characters.
4236 @item <@var{string}>
4237 You can delimit strings with matching angle brackets.
4240 @item single-character string escape
4241 To include any single character literally in a string (even if the
4242 character would otherwise have some special meaning), you can prefix the
4243 character with @samp{!} (an exclamation mark). For example, you can
4244 write @samp{<4.3 !> 5.4!!>} to get the literal text @samp{4.3 > 5.4!}.
4246 @item Expression results as strings
4247 You can write @samp{%@var{expr}} to evaluate the expression @var{expr}
4248 and use the result as a string.
4252 @section @code{.ascii "@var{string}"}@dots{}
4254 @cindex @code{ascii} directive
4255 @cindex string literals
4256 @code{.ascii} expects zero or more string literals (@pxref{Strings})
4257 separated by commas. It assembles each string (with no automatic
4258 trailing zero byte) into consecutive addresses.
4261 @section @code{.asciz "@var{string}"}@dots{}
4263 @cindex @code{asciz} directive
4264 @cindex zero-terminated strings
4265 @cindex null-terminated strings
4266 @code{.asciz} is just like @code{.ascii}, but each string is followed by
4267 a zero byte. The ``z'' in @samp{.asciz} stands for ``zero''.
4270 @section @code{.balign[wl] @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
4272 @cindex padding the location counter given number of bytes
4273 @cindex @code{balign} directive
4274 Pad the location counter (in the current subsection) to a particular
4275 storage boundary. The first expression (which must be absolute) is the
4276 alignment request in bytes. For example @samp{.balign 8} advances
4277 the location counter until it is a multiple of 8. If the location counter
4278 is already a multiple of 8, no change is needed.
4280 The second expression (also absolute) gives the fill value to be stored in the
4281 padding bytes. It (and the comma) may be omitted. If it is omitted, the
4282 padding bytes are normally zero. However, on some systems, if the section is
4283 marked as containing code and the fill value is omitted, the space is filled
4284 with no-op instructions.
4286 The third expression is also absolute, and is also optional. If it is present,
4287 it is the maximum number of bytes that should be skipped by this alignment
4288 directive. If doing the alignment would require skipping more bytes than the
4289 specified maximum, then the alignment is not done at all. You can omit the
4290 fill value (the second argument) entirely by simply using two commas after the
4291 required alignment; this can be useful if you want the alignment to be filled
4292 with no-op instructions when appropriate.
4294 @cindex @code{balignw} directive
4295 @cindex @code{balignl} directive
4296 The @code{.balignw} and @code{.balignl} directives are variants of the
4297 @code{.balign} directive. The @code{.balignw} directive treats the fill
4298 pattern as a two byte word value. The @code{.balignl} directives treats the
4299 fill pattern as a four byte longword value. For example, @code{.balignw
4300 4,0x368d} will align to a multiple of 4. If it skips two bytes, they will be
4301 filled in with the value 0x368d (the exact placement of the bytes depends upon
4302 the endianness of the processor). If it skips 1 or 3 bytes, the fill value is
4305 @node Bundle directives
4306 @section @code{.bundle_align_mode @var{abs-expr}}
4307 @cindex @code{bundle_align_mode} directive
4309 @cindex instruction bundle
4310 @cindex aligned instruction bundle
4311 @code{.bundle_align_mode} enables or disables @dfn{aligned instruction
4312 bundle} mode. In this mode, sequences of adjacent instructions are grouped
4313 into fixed-sized @dfn{bundles}. If the argument is zero, this mode is
4314 disabled (which is the default state). If the argument it not zero, it
4315 gives the size of an instruction bundle as a power of two (as for the
4316 @code{.p2align} directive, @pxref{P2align}).
4318 For some targets, it's an ABI requirement that no instruction may span a
4319 certain aligned boundary. A @dfn{bundle} is simply a sequence of
4320 instructions that starts on an aligned boundary. For example, if
4321 @var{abs-expr} is @code{5} then the bundle size is 32, so each aligned
4322 chunk of 32 bytes is a bundle. When aligned instruction bundle mode is in
4323 effect, no single instruction may span a boundary between bundles. If an
4324 instruction would start too close to the end of a bundle for the length of
4325 that particular instruction to fit within the bundle, then the space at the
4326 end of that bundle is filled with no-op instructions so the instruction
4327 starts in the next bundle. As a corollary, it's an error if any single
4328 instruction's encoding is longer than the bundle size.
4330 @section @code{.bundle_lock} and @code{.bundle_unlock}
4331 @cindex @code{bundle_lock} directive
4332 @cindex @code{bundle_unlock} directive
4333 The @code{.bundle_lock} and directive @code{.bundle_unlock} directives
4334 allow explicit control over instruction bundle padding. These directives
4335 are only valid when @code{.bundle_align_mode} has been used to enable
4336 aligned instruction bundle mode. It's an error if they appear when
4337 @code{.bundle_align_mode} has not been used at all, or when the last
4338 directive was @w{@code{.bundle_align_mode 0}}.
4340 @cindex bundle-locked
4341 For some targets, it's an ABI requirement that certain instructions may
4342 appear only as part of specified permissible sequences of multiple
4343 instructions, all within the same bundle. A pair of @code{.bundle_lock}
4344 and @code{.bundle_unlock} directives define a @dfn{bundle-locked}
4345 instruction sequence. For purposes of aligned instruction bundle mode, a
4346 sequence starting with @code{.bundle_lock} and ending with
4347 @code{.bundle_unlock} is treated as a single instruction. That is, the
4348 entire sequence must fit into a single bundle and may not span a bundle
4349 boundary. If necessary, no-op instructions will be inserted before the
4350 first instruction of the sequence so that the whole sequence starts on an
4351 aligned bundle boundary. It's an error if the sequence is longer than the
4354 Bundle-locked sequences do not nest. It's an error if two
4355 @code{.bundle_lock} directives appear without an intervening
4356 @code{.bundle_unlock} directive.
4359 @section @code{.byte @var{expressions}}
4361 @cindex @code{byte} directive
4362 @cindex integers, one byte
4363 @code{.byte} expects zero or more expressions, separated by commas.
4364 Each expression is assembled into the next byte.
4366 @node CFI directives
4367 @section @code{.cfi_sections @var{section_list}}
4368 @cindex @code{cfi_sections} directive
4369 @code{.cfi_sections} may be used to specify whether CFI directives
4370 should emit @code{.eh_frame} section and/or @code{.debug_frame} section.
4371 If @var{section_list} is @code{.eh_frame}, @code{.eh_frame} is emitted,
4372 if @var{section_list} is @code{.debug_frame}, @code{.debug_frame} is emitted.
4373 To emit both use @code{.eh_frame, .debug_frame}. The default if this
4374 directive is not used is @code{.cfi_sections .eh_frame}.
4376 @section @code{.cfi_startproc [simple]}
4377 @cindex @code{cfi_startproc} directive
4378 @code{.cfi_startproc} is used at the beginning of each function that
4379 should have an entry in @code{.eh_frame}. It initializes some internal
4380 data structures. Don't forget to close the function by
4381 @code{.cfi_endproc}.
4383 Unless @code{.cfi_startproc} is used along with parameter @code{simple}
4384 it also emits some architecture dependent initial CFI instructions.
4386 @section @code{.cfi_endproc}
4387 @cindex @code{cfi_endproc} directive
4388 @code{.cfi_endproc} is used at the end of a function where it closes its
4389 unwind entry previously opened by
4390 @code{.cfi_startproc}, and emits it to @code{.eh_frame}.
4392 @section @code{.cfi_personality @var{encoding} [, @var{exp}]}
4393 @code{.cfi_personality} defines personality routine and its encoding.
4394 @var{encoding} must be a constant determining how the personality
4395 should be encoded. If it is 255 (@code{DW_EH_PE_omit}), second
4396 argument is not present, otherwise second argument should be
4397 a constant or a symbol name. When using indirect encodings,
4398 the symbol provided should be the location where personality
4399 can be loaded from, not the personality routine itself.
4400 The default after @code{.cfi_startproc} is @code{.cfi_personality 0xff},
4401 no personality routine.
4403 @section @code{.cfi_lsda @var{encoding} [, @var{exp}]}
4404 @code{.cfi_lsda} defines LSDA and its encoding.
4405 @var{encoding} must be a constant determining how the LSDA
4406 should be encoded. If it is 255 (@code{DW_EH_PE_omit}), second
4407 argument is not present, otherwise second argument should be a constant
4408 or a symbol name. The default after @code{.cfi_startproc} is @code{.cfi_lsda 0xff},
4411 @section @code{.cfi_def_cfa @var{register}, @var{offset}}
4412 @code{.cfi_def_cfa} defines a rule for computing CFA as: @i{take
4413 address from @var{register} and add @var{offset} to it}.
4415 @section @code{.cfi_def_cfa_register @var{register}}
4416 @code{.cfi_def_cfa_register} modifies a rule for computing CFA. From
4417 now on @var{register} will be used instead of the old one. Offset
4420 @section @code{.cfi_def_cfa_offset @var{offset}}
4421 @code{.cfi_def_cfa_offset} modifies a rule for computing CFA. Register
4422 remains the same, but @var{offset} is new. Note that it is the
4423 absolute offset that will be added to a defined register to compute
4426 @section @code{.cfi_adjust_cfa_offset @var{offset}}
4427 Same as @code{.cfi_def_cfa_offset} but @var{offset} is a relative
4428 value that is added/substracted from the previous offset.
4430 @section @code{.cfi_offset @var{register}, @var{offset}}
4431 Previous value of @var{register} is saved at offset @var{offset} from
4434 @section @code{.cfi_rel_offset @var{register}, @var{offset}}
4435 Previous value of @var{register} is saved at offset @var{offset} from
4436 the current CFA register. This is transformed to @code{.cfi_offset}
4437 using the known displacement of the CFA register from the CFA.
4438 This is often easier to use, because the number will match the
4439 code it's annotating.
4441 @section @code{.cfi_register @var{register1}, @var{register2}}
4442 Previous value of @var{register1} is saved in register @var{register2}.
4444 @section @code{.cfi_restore @var{register}}
4445 @code{.cfi_restore} says that the rule for @var{register} is now the
4446 same as it was at the beginning of the function, after all initial
4447 instruction added by @code{.cfi_startproc} were executed.
4449 @section @code{.cfi_undefined @var{register}}
4450 From now on the previous value of @var{register} can't be restored anymore.
4452 @section @code{.cfi_same_value @var{register}}
4453 Current value of @var{register} is the same like in the previous frame,
4454 i.e. no restoration needed.
4456 @section @code{.cfi_remember_state},
4457 First save all current rules for all registers by @code{.cfi_remember_state},
4458 then totally screw them up by subsequent @code{.cfi_*} directives and when
4459 everything is hopelessly bad, use @code{.cfi_restore_state} to restore
4460 the previous saved state.
4462 @section @code{.cfi_return_column @var{register}}
4463 Change return column @var{register}, i.e. the return address is either
4464 directly in @var{register} or can be accessed by rules for @var{register}.
4466 @section @code{.cfi_signal_frame}
4467 Mark current function as signal trampoline.
4469 @section @code{.cfi_window_save}
4470 SPARC register window has been saved.
4472 @section @code{.cfi_escape} @var{expression}[, @dots{}]
4473 Allows the user to add arbitrary bytes to the unwind info. One
4474 might use this to add OS-specific CFI opcodes, or generic CFI
4475 opcodes that GAS does not yet support.
4477 @section @code{.cfi_val_encoded_addr @var{register}, @var{encoding}, @var{label}}
4478 The current value of @var{register} is @var{label}. The value of @var{label}
4479 will be encoded in the output file according to @var{encoding}; see the
4480 description of @code{.cfi_personality} for details on this encoding.
4482 The usefulness of equating a register to a fixed label is probably
4483 limited to the return address register. Here, it can be useful to
4484 mark a code segment that has only one return address which is reached
4485 by a direct branch and no copy of the return address exists in memory
4486 or another register.
4489 @section @code{.comm @var{symbol} , @var{length} }
4491 @cindex @code{comm} directive
4492 @cindex symbol, common
4493 @code{.comm} declares a common symbol named @var{symbol}. When linking, a
4494 common symbol in one object file may be merged with a defined or common symbol
4495 of the same name in another object file. If @code{@value{LD}} does not see a
4496 definition for the symbol--just one or more common symbols--then it will
4497 allocate @var{length} bytes of uninitialized memory. @var{length} must be an
4498 absolute expression. If @code{@value{LD}} sees multiple common symbols with
4499 the same name, and they do not all have the same size, it will allocate space
4500 using the largest size.
4503 When using ELF or (as a GNU extension) PE, the @code{.comm} directive takes
4504 an optional third argument. This is the desired alignment of the symbol,
4505 specified for ELF as a byte boundary (for example, an alignment of 16 means
4506 that the least significant 4 bits of the address should be zero), and for PE
4507 as a power of two (for example, an alignment of 5 means aligned to a 32-byte
4508 boundary). The alignment must be an absolute expression, and it must be a
4509 power of two. If @code{@value{LD}} allocates uninitialized memory for the
4510 common symbol, it will use the alignment when placing the symbol. If no
4511 alignment is specified, @command{@value{AS}} will set the alignment to the
4512 largest power of two less than or equal to the size of the symbol, up to a
4513 maximum of 16 on ELF, or the default section alignment of 4 on PE@footnote{This
4514 is not the same as the executable image file alignment controlled by @code{@value{LD}}'s
4515 @samp{--section-alignment} option; image file sections in PE are aligned to
4516 multiples of 4096, which is far too large an alignment for ordinary variables.
4517 It is rather the default alignment for (non-debug) sections within object
4518 (@samp{*.o}) files, which are less strictly aligned.}.
4522 The syntax for @code{.comm} differs slightly on the HPPA. The syntax is
4523 @samp{@var{symbol} .comm, @var{length}}; @var{symbol} is optional.
4527 @section @code{.data @var{subsection}}
4529 @cindex @code{data} directive
4530 @code{.data} tells @command{@value{AS}} to assemble the following statements onto the
4531 end of the data subsection numbered @var{subsection} (which is an
4532 absolute expression). If @var{subsection} is omitted, it defaults
4537 @section @code{.def @var{name}}
4539 @cindex @code{def} directive
4540 @cindex COFF symbols, debugging
4541 @cindex debugging COFF symbols
4542 Begin defining debugging information for a symbol @var{name}; the
4543 definition extends until the @code{.endef} directive is encountered.
4546 This directive is only observed when @command{@value{AS}} is configured for COFF
4547 format output; when producing @code{b.out}, @samp{.def} is recognized,
4554 @section @code{.desc @var{symbol}, @var{abs-expression}}
4556 @cindex @code{desc} directive
4557 @cindex COFF symbol descriptor
4558 @cindex symbol descriptor, COFF
4559 This directive sets the descriptor of the symbol (@pxref{Symbol Attributes})
4560 to the low 16 bits of an absolute expression.
4563 The @samp{.desc} directive is not available when @command{@value{AS}} is
4564 configured for COFF output; it is only for @code{a.out} or @code{b.out}
4565 object format. For the sake of compatibility, @command{@value{AS}} accepts
4566 it, but produces no output, when configured for COFF.
4572 @section @code{.dim}
4574 @cindex @code{dim} directive
4575 @cindex COFF auxiliary symbol information
4576 @cindex auxiliary symbol information, COFF
4577 This directive is generated by compilers to include auxiliary debugging
4578 information in the symbol table. It is only permitted inside
4579 @code{.def}/@code{.endef} pairs.
4582 @samp{.dim} is only meaningful when generating COFF format output; when
4583 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
4589 @section @code{.double @var{flonums}}
4591 @cindex @code{double} directive
4592 @cindex floating point numbers (double)
4593 @code{.double} expects zero or more flonums, separated by commas. It
4594 assembles floating point numbers.
4596 The exact kind of floating point numbers emitted depends on how
4597 @command{@value{AS}} is configured. @xref{Machine Dependencies}.
4601 On the @value{TARGET} family @samp{.double} emits 64-bit floating-point numbers
4602 in @sc{ieee} format.
4607 @section @code{.eject}
4609 @cindex @code{eject} directive
4610 @cindex new page, in listings
4611 @cindex page, in listings
4612 @cindex listing control: new page
4613 Force a page break at this point, when generating assembly listings.
4616 @section @code{.else}
4618 @cindex @code{else} directive
4619 @code{.else} is part of the @command{@value{AS}} support for conditional
4620 assembly; see @ref{If,,@code{.if}}. It marks the beginning of a section
4621 of code to be assembled if the condition for the preceding @code{.if}
4625 @section @code{.elseif}
4627 @cindex @code{elseif} directive
4628 @code{.elseif} is part of the @command{@value{AS}} support for conditional
4629 assembly; see @ref{If,,@code{.if}}. It is shorthand for beginning a new
4630 @code{.if} block that would otherwise fill the entire @code{.else} section.
4633 @section @code{.end}
4635 @cindex @code{end} directive
4636 @code{.end} marks the end of the assembly file. @command{@value{AS}} does not
4637 process anything in the file past the @code{.end} directive.
4641 @section @code{.endef}
4643 @cindex @code{endef} directive
4644 This directive flags the end of a symbol definition begun with
4648 @samp{.endef} is only meaningful when generating COFF format output; if
4649 @command{@value{AS}} is configured to generate @code{b.out}, it accepts this
4650 directive but ignores it.
4655 @section @code{.endfunc}
4656 @cindex @code{endfunc} directive
4657 @code{.endfunc} marks the end of a function specified with @code{.func}.
4660 @section @code{.endif}
4662 @cindex @code{endif} directive
4663 @code{.endif} is part of the @command{@value{AS}} support for conditional assembly;
4664 it marks the end of a block of code that is only assembled
4665 conditionally. @xref{If,,@code{.if}}.
4668 @section @code{.equ @var{symbol}, @var{expression}}
4670 @cindex @code{equ} directive
4671 @cindex assigning values to symbols
4672 @cindex symbols, assigning values to
4673 This directive sets the value of @var{symbol} to @var{expression}.
4674 It is synonymous with @samp{.set}; see @ref{Set,,@code{.set}}.
4677 The syntax for @code{equ} on the HPPA is
4678 @samp{@var{symbol} .equ @var{expression}}.
4682 The syntax for @code{equ} on the Z80 is
4683 @samp{@var{symbol} equ @var{expression}}.
4684 On the Z80 it is an eror if @var{symbol} is already defined,
4685 but the symbol is not protected from later redefinition.
4686 Compare @ref{Equiv}.
4690 @section @code{.equiv @var{symbol}, @var{expression}}
4691 @cindex @code{equiv} directive
4692 The @code{.equiv} directive is like @code{.equ} and @code{.set}, except that
4693 the assembler will signal an error if @var{symbol} is already defined. Note a
4694 symbol which has been referenced but not actually defined is considered to be
4697 Except for the contents of the error message, this is roughly equivalent to
4704 plus it protects the symbol from later redefinition.
4707 @section @code{.eqv @var{symbol}, @var{expression}}
4708 @cindex @code{eqv} directive
4709 The @code{.eqv} directive is like @code{.equiv}, but no attempt is made to
4710 evaluate the expression or any part of it immediately. Instead each time
4711 the resulting symbol is used in an expression, a snapshot of its current
4715 @section @code{.err}
4716 @cindex @code{err} directive
4717 If @command{@value{AS}} assembles a @code{.err} directive, it will print an error
4718 message and, unless the @option{-Z} option was used, it will not generate an
4719 object file. This can be used to signal an error in conditionally compiled code.
4722 @section @code{.error "@var{string}"}
4723 @cindex error directive
4725 Similarly to @code{.err}, this directive emits an error, but you can specify a
4726 string that will be emitted as the error message. If you don't specify the
4727 message, it defaults to @code{".error directive invoked in source file"}.
4728 @xref{Errors, ,Error and Warning Messages}.
4731 .error "This code has not been assembled and tested."
4735 @section @code{.exitm}
4736 Exit early from the current macro definition. @xref{Macro}.
4739 @section @code{.extern}
4741 @cindex @code{extern} directive
4742 @code{.extern} is accepted in the source program---for compatibility
4743 with other assemblers---but it is ignored. @command{@value{AS}} treats
4744 all undefined symbols as external.
4747 @section @code{.fail @var{expression}}
4749 @cindex @code{fail} directive
4750 Generates an error or a warning. If the value of the @var{expression} is 500
4751 or more, @command{@value{AS}} will print a warning message. If the value is less
4752 than 500, @command{@value{AS}} will print an error message. The message will
4753 include the value of @var{expression}. This can occasionally be useful inside
4754 complex nested macros or conditional assembly.
4757 @section @code{.file}
4758 @cindex @code{file} directive
4760 @ifclear no-file-dir
4761 There are two different versions of the @code{.file} directive. Targets
4762 that support DWARF2 line number information use the DWARF2 version of
4763 @code{.file}. Other targets use the default version.
4765 @subheading Default Version
4767 @cindex logical file name
4768 @cindex file name, logical
4769 This version of the @code{.file} directive tells @command{@value{AS}} that we
4770 are about to start a new logical file. The syntax is:
4776 @var{string} is the new file name. In general, the filename is
4777 recognized whether or not it is surrounded by quotes @samp{"}; but if you wish
4778 to specify an empty file name, you must give the quotes--@code{""}. This
4779 statement may go away in future: it is only recognized to be compatible with
4780 old @command{@value{AS}} programs.
4782 @subheading DWARF2 Version
4785 When emitting DWARF2 line number information, @code{.file} assigns filenames
4786 to the @code{.debug_line} file name table. The syntax is:
4789 .file @var{fileno} @var{filename}
4792 The @var{fileno} operand should be a unique positive integer to use as the
4793 index of the entry in the table. The @var{filename} operand is a C string
4796 The detail of filename indices is exposed to the user because the filename
4797 table is shared with the @code{.debug_info} section of the DWARF2 debugging
4798 information, and thus the user must know the exact indices that table
4802 @section @code{.fill @var{repeat} , @var{size} , @var{value}}
4804 @cindex @code{fill} directive
4805 @cindex writing patterns in memory
4806 @cindex patterns, writing in memory
4807 @var{repeat}, @var{size} and @var{value} are absolute expressions.
4808 This emits @var{repeat} copies of @var{size} bytes. @var{Repeat}
4809 may be zero or more. @var{Size} may be zero or more, but if it is
4810 more than 8, then it is deemed to have the value 8, compatible with
4811 other people's assemblers. The contents of each @var{repeat} bytes
4812 is taken from an 8-byte number. The highest order 4 bytes are
4813 zero. The lowest order 4 bytes are @var{value} rendered in the
4814 byte-order of an integer on the computer @command{@value{AS}} is assembling for.
4815 Each @var{size} bytes in a repetition is taken from the lowest order
4816 @var{size} bytes of this number. Again, this bizarre behavior is
4817 compatible with other people's assemblers.
4819 @var{size} and @var{value} are optional.
4820 If the second comma and @var{value} are absent, @var{value} is
4821 assumed zero. If the first comma and following tokens are absent,
4822 @var{size} is assumed to be 1.
4825 @section @code{.float @var{flonums}}
4827 @cindex floating point numbers (single)
4828 @cindex @code{float} directive
4829 This directive assembles zero or more flonums, separated by commas. It
4830 has the same effect as @code{.single}.
4832 The exact kind of floating point numbers emitted depends on how
4833 @command{@value{AS}} is configured.
4834 @xref{Machine Dependencies}.
4838 On the @value{TARGET} family, @code{.float} emits 32-bit floating point numbers
4839 in @sc{ieee} format.
4844 @section @code{.func @var{name}[,@var{label}]}
4845 @cindex @code{func} directive
4846 @code{.func} emits debugging information to denote function @var{name}, and
4847 is ignored unless the file is assembled with debugging enabled.
4848 Only @samp{--gstabs[+]} is currently supported.
4849 @var{label} is the entry point of the function and if omitted @var{name}
4850 prepended with the @samp{leading char} is used.
4851 @samp{leading char} is usually @code{_} or nothing, depending on the target.
4852 All functions are currently defined to have @code{void} return type.
4853 The function must be terminated with @code{.endfunc}.
4856 @section @code{.global @var{symbol}}, @code{.globl @var{symbol}}
4858 @cindex @code{global} directive
4859 @cindex symbol, making visible to linker
4860 @code{.global} makes the symbol visible to @code{@value{LD}}. If you define
4861 @var{symbol} in your partial program, its value is made available to
4862 other partial programs that are linked with it. Otherwise,
4863 @var{symbol} takes its attributes from a symbol of the same name
4864 from another file linked into the same program.
4866 Both spellings (@samp{.globl} and @samp{.global}) are accepted, for
4867 compatibility with other assemblers.
4870 On the HPPA, @code{.global} is not always enough to make it accessible to other
4871 partial programs. You may need the HPPA-only @code{.EXPORT} directive as well.
4872 @xref{HPPA Directives, ,HPPA Assembler Directives}.
4877 @section @code{.gnu_attribute @var{tag},@var{value}}
4878 Record a @sc{gnu} object attribute for this file. @xref{Object Attributes}.
4881 @section @code{.hidden @var{names}}
4883 @cindex @code{hidden} directive
4885 This is one of the ELF visibility directives. The other two are
4886 @code{.internal} (@pxref{Internal,,@code{.internal}}) and
4887 @code{.protected} (@pxref{Protected,,@code{.protected}}).
4889 This directive overrides the named symbols default visibility (which is set by
4890 their binding: local, global or weak). The directive sets the visibility to
4891 @code{hidden} which means that the symbols are not visible to other components.
4892 Such symbols are always considered to be @code{protected} as well.
4896 @section @code{.hword @var{expressions}}
4898 @cindex @code{hword} directive
4899 @cindex integers, 16-bit
4900 @cindex numbers, 16-bit
4901 @cindex sixteen bit integers
4902 This expects zero or more @var{expressions}, and emits
4903 a 16 bit number for each.
4906 This directive is a synonym for @samp{.short}; depending on the target
4907 architecture, it may also be a synonym for @samp{.word}.
4911 This directive is a synonym for @samp{.short}.
4914 This directive is a synonym for both @samp{.short} and @samp{.word}.
4919 @section @code{.ident}
4921 @cindex @code{ident} directive
4923 This directive is used by some assemblers to place tags in object files. The
4924 behavior of this directive varies depending on the target. When using the
4925 a.out object file format, @command{@value{AS}} simply accepts the directive for
4926 source-file compatibility with existing assemblers, but does not emit anything
4927 for it. When using COFF, comments are emitted to the @code{.comment} or
4928 @code{.rdata} section, depending on the target. When using ELF, comments are
4929 emitted to the @code{.comment} section.
4932 @section @code{.if @var{absolute expression}}
4934 @cindex conditional assembly
4935 @cindex @code{if} directive
4936 @code{.if} marks the beginning of a section of code which is only
4937 considered part of the source program being assembled if the argument
4938 (which must be an @var{absolute expression}) is non-zero. The end of
4939 the conditional section of code must be marked by @code{.endif}
4940 (@pxref{Endif,,@code{.endif}}); optionally, you may include code for the
4941 alternative condition, flagged by @code{.else} (@pxref{Else,,@code{.else}}).
4942 If you have several conditions to check, @code{.elseif} may be used to avoid
4943 nesting blocks if/else within each subsequent @code{.else} block.
4945 The following variants of @code{.if} are also supported:
4947 @cindex @code{ifdef} directive
4948 @item .ifdef @var{symbol}
4949 Assembles the following section of code if the specified @var{symbol}
4950 has been defined. Note a symbol which has been referenced but not yet defined
4951 is considered to be undefined.
4953 @cindex @code{ifb} directive
4954 @item .ifb @var{text}
4955 Assembles the following section of code if the operand is blank (empty).
4957 @cindex @code{ifc} directive
4958 @item .ifc @var{string1},@var{string2}
4959 Assembles the following section of code if the two strings are the same. The
4960 strings may be optionally quoted with single quotes. If they are not quoted,
4961 the first string stops at the first comma, and the second string stops at the
4962 end of the line. Strings which contain whitespace should be quoted. The
4963 string comparison is case sensitive.
4965 @cindex @code{ifeq} directive
4966 @item .ifeq @var{absolute expression}
4967 Assembles the following section of code if the argument is zero.
4969 @cindex @code{ifeqs} directive
4970 @item .ifeqs @var{string1},@var{string2}
4971 Another form of @code{.ifc}. The strings must be quoted using double quotes.
4973 @cindex @code{ifge} directive
4974 @item .ifge @var{absolute expression}
4975 Assembles the following section of code if the argument is greater than or
4978 @cindex @code{ifgt} directive
4979 @item .ifgt @var{absolute expression}
4980 Assembles the following section of code if the argument is greater than zero.
4982 @cindex @code{ifle} directive
4983 @item .ifle @var{absolute expression}
4984 Assembles the following section of code if the argument is less than or equal
4987 @cindex @code{iflt} directive
4988 @item .iflt @var{absolute expression}
4989 Assembles the following section of code if the argument is less than zero.
4991 @cindex @code{ifnb} directive
4992 @item .ifnb @var{text}
4993 Like @code{.ifb}, but the sense of the test is reversed: this assembles the
4994 following section of code if the operand is non-blank (non-empty).
4996 @cindex @code{ifnc} directive
4997 @item .ifnc @var{string1},@var{string2}.
4998 Like @code{.ifc}, but the sense of the test is reversed: this assembles the
4999 following section of code if the two strings are not the same.
5001 @cindex @code{ifndef} directive
5002 @cindex @code{ifnotdef} directive
5003 @item .ifndef @var{symbol}
5004 @itemx .ifnotdef @var{symbol}
5005 Assembles the following section of code if the specified @var{symbol}
5006 has not been defined. Both spelling variants are equivalent. Note a symbol
5007 which has been referenced but not yet defined is considered to be undefined.
5009 @cindex @code{ifne} directive
5010 @item .ifne @var{absolute expression}
5011 Assembles the following section of code if the argument is not equal to zero
5012 (in other words, this is equivalent to @code{.if}).
5014 @cindex @code{ifnes} directive
5015 @item .ifnes @var{string1},@var{string2}
5016 Like @code{.ifeqs}, but the sense of the test is reversed: this assembles the
5017 following section of code if the two strings are not the same.
5021 @section @code{.incbin "@var{file}"[,@var{skip}[,@var{count}]]}
5023 @cindex @code{incbin} directive
5024 @cindex binary files, including
5025 The @code{incbin} directive includes @var{file} verbatim at the current
5026 location. You can control the search paths used with the @samp{-I} command-line
5027 option (@pxref{Invoking,,Command-Line Options}). Quotation marks are required
5030 The @var{skip} argument skips a number of bytes from the start of the
5031 @var{file}. The @var{count} argument indicates the maximum number of bytes to
5032 read. Note that the data is not aligned in any way, so it is the user's
5033 responsibility to make sure that proper alignment is provided both before and
5034 after the @code{incbin} directive.
5037 @section @code{.include "@var{file}"}
5039 @cindex @code{include} directive
5040 @cindex supporting files, including
5041 @cindex files, including
5042 This directive provides a way to include supporting files at specified
5043 points in your source program. The code from @var{file} is assembled as
5044 if it followed the point of the @code{.include}; when the end of the
5045 included file is reached, assembly of the original file continues. You
5046 can control the search paths used with the @samp{-I} command-line option
5047 (@pxref{Invoking,,Command-Line Options}). Quotation marks are required
5051 @section @code{.int @var{expressions}}
5053 @cindex @code{int} directive
5054 @cindex integers, 32-bit
5055 Expect zero or more @var{expressions}, of any section, separated by commas.
5056 For each expression, emit a number that, at run time, is the value of that
5057 expression. The byte order and bit size of the number depends on what kind
5058 of target the assembly is for.
5062 On most forms of the H8/300, @code{.int} emits 16-bit
5063 integers. On the H8/300H and the Renesas SH, however, @code{.int} emits
5070 @section @code{.internal @var{names}}
5072 @cindex @code{internal} directive
5074 This is one of the ELF visibility directives. The other two are
5075 @code{.hidden} (@pxref{Hidden,,@code{.hidden}}) and
5076 @code{.protected} (@pxref{Protected,,@code{.protected}}).
5078 This directive overrides the named symbols default visibility (which is set by
5079 their binding: local, global or weak). The directive sets the visibility to
5080 @code{internal} which means that the symbols are considered to be @code{hidden}
5081 (i.e., not visible to other components), and that some extra, processor specific
5082 processing must also be performed upon the symbols as well.
5086 @section @code{.irp @var{symbol},@var{values}}@dots{}
5088 @cindex @code{irp} directive
5089 Evaluate a sequence of statements assigning different values to @var{symbol}.
5090 The sequence of statements starts at the @code{.irp} directive, and is
5091 terminated by an @code{.endr} directive. For each @var{value}, @var{symbol} is
5092 set to @var{value}, and the sequence of statements is assembled. If no
5093 @var{value} is listed, the sequence of statements is assembled once, with
5094 @var{symbol} set to the null string. To refer to @var{symbol} within the
5095 sequence of statements, use @var{\symbol}.
5097 For example, assembling
5105 is equivalent to assembling
5113 For some caveats with the spelling of @var{symbol}, see also @ref{Macro}.
5116 @section @code{.irpc @var{symbol},@var{values}}@dots{}
5118 @cindex @code{irpc} directive
5119 Evaluate a sequence of statements assigning different values to @var{symbol}.
5120 The sequence of statements starts at the @code{.irpc} directive, and is
5121 terminated by an @code{.endr} directive. For each character in @var{value},
5122 @var{symbol} is set to the character, and the sequence of statements is
5123 assembled. If no @var{value} is listed, the sequence of statements is
5124 assembled once, with @var{symbol} set to the null string. To refer to
5125 @var{symbol} within the sequence of statements, use @var{\symbol}.
5127 For example, assembling
5135 is equivalent to assembling
5143 For some caveats with the spelling of @var{symbol}, see also the discussion
5147 @section @code{.lcomm @var{symbol} , @var{length}}
5149 @cindex @code{lcomm} directive
5150 @cindex local common symbols
5151 @cindex symbols, local common
5152 Reserve @var{length} (an absolute expression) bytes for a local common
5153 denoted by @var{symbol}. The section and value of @var{symbol} are
5154 those of the new local common. The addresses are allocated in the bss
5155 section, so that at run-time the bytes start off zeroed. @var{Symbol}
5156 is not declared global (@pxref{Global,,@code{.global}}), so is normally
5157 not visible to @code{@value{LD}}.
5160 Some targets permit a third argument to be used with @code{.lcomm}. This
5161 argument specifies the desired alignment of the symbol in the bss section.
5165 The syntax for @code{.lcomm} differs slightly on the HPPA. The syntax is
5166 @samp{@var{symbol} .lcomm, @var{length}}; @var{symbol} is optional.
5170 @section @code{.lflags}
5172 @cindex @code{lflags} directive (ignored)
5173 @command{@value{AS}} accepts this directive, for compatibility with other
5174 assemblers, but ignores it.
5176 @ifclear no-line-dir
5178 @section @code{.line @var{line-number}}
5180 @cindex @code{line} directive
5181 @cindex logical line number
5183 Change the logical line number. @var{line-number} must be an absolute
5184 expression. The next line has that logical line number. Therefore any other
5185 statements on the current line (after a statement separator character) are
5186 reported as on logical line number @var{line-number} @minus{} 1. One day
5187 @command{@value{AS}} will no longer support this directive: it is recognized only
5188 for compatibility with existing assembler programs.
5191 Even though this is a directive associated with the @code{a.out} or
5192 @code{b.out} object-code formats, @command{@value{AS}} still recognizes it
5193 when producing COFF output, and treats @samp{.line} as though it
5194 were the COFF @samp{.ln} @emph{if} it is found outside a
5195 @code{.def}/@code{.endef} pair.
5197 Inside a @code{.def}, @samp{.line} is, instead, one of the directives
5198 used by compilers to generate auxiliary symbol information for
5203 @section @code{.linkonce [@var{type}]}
5205 @cindex @code{linkonce} directive
5206 @cindex common sections
5207 Mark the current section so that the linker only includes a single copy of it.
5208 This may be used to include the same section in several different object files,
5209 but ensure that the linker will only include it once in the final output file.
5210 The @code{.linkonce} pseudo-op must be used for each instance of the section.
5211 Duplicate sections are detected based on the section name, so it should be
5214 This directive is only supported by a few object file formats; as of this
5215 writing, the only object file format which supports it is the Portable
5216 Executable format used on Windows NT.
5218 The @var{type} argument is optional. If specified, it must be one of the
5219 following strings. For example:
5223 Not all types may be supported on all object file formats.
5227 Silently discard duplicate sections. This is the default.
5230 Warn if there are duplicate sections, but still keep only one copy.
5233 Warn if any of the duplicates have different sizes.
5236 Warn if any of the duplicates do not have exactly the same contents.
5240 @section @code{.list}
5242 @cindex @code{list} directive
5243 @cindex listing control, turning on
5244 Control (in conjunction with the @code{.nolist} directive) whether or
5245 not assembly listings are generated. These two directives maintain an
5246 internal counter (which is zero initially). @code{.list} increments the
5247 counter, and @code{.nolist} decrements it. Assembly listings are
5248 generated whenever the counter is greater than zero.
5250 By default, listings are disabled. When you enable them (with the
5251 @samp{-a} command line option; @pxref{Invoking,,Command-Line Options}),
5252 the initial value of the listing counter is one.
5255 @section @code{.ln @var{line-number}}
5257 @cindex @code{ln} directive
5258 @ifclear no-line-dir
5259 @samp{.ln} is a synonym for @samp{.line}.
5262 Tell @command{@value{AS}} to change the logical line number. @var{line-number}
5263 must be an absolute expression. The next line has that logical
5264 line number, so any other statements on the current line (after a
5265 statement separator character @code{;}) are reported as on logical
5266 line number @var{line-number} @minus{} 1.
5269 This directive is accepted, but ignored, when @command{@value{AS}} is
5270 configured for @code{b.out}; its effect is only associated with COFF
5276 @section @code{.loc @var{fileno} @var{lineno} [@var{column}] [@var{options}]}
5277 @cindex @code{loc} directive
5278 When emitting DWARF2 line number information,
5279 the @code{.loc} directive will add a row to the @code{.debug_line} line
5280 number matrix corresponding to the immediately following assembly
5281 instruction. The @var{fileno}, @var{lineno}, and optional @var{column}
5282 arguments will be applied to the @code{.debug_line} state machine before
5285 The @var{options} are a sequence of the following tokens in any order:
5289 This option will set the @code{basic_block} register in the
5290 @code{.debug_line} state machine to @code{true}.
5293 This option will set the @code{prologue_end} register in the
5294 @code{.debug_line} state machine to @code{true}.
5296 @item epilogue_begin
5297 This option will set the @code{epilogue_begin} register in the
5298 @code{.debug_line} state machine to @code{true}.
5300 @item is_stmt @var{value}
5301 This option will set the @code{is_stmt} register in the
5302 @code{.debug_line} state machine to @code{value}, which must be
5305 @item isa @var{value}
5306 This directive will set the @code{isa} register in the @code{.debug_line}
5307 state machine to @var{value}, which must be an unsigned integer.
5309 @item discriminator @var{value}
5310 This directive will set the @code{discriminator} register in the @code{.debug_line}
5311 state machine to @var{value}, which must be an unsigned integer.
5315 @node Loc_mark_labels
5316 @section @code{.loc_mark_labels @var{enable}}
5317 @cindex @code{loc_mark_labels} directive
5318 When emitting DWARF2 line number information,
5319 the @code{.loc_mark_labels} directive makes the assembler emit an entry
5320 to the @code{.debug_line} line number matrix with the @code{basic_block}
5321 register in the state machine set whenever a code label is seen.
5322 The @var{enable} argument should be either 1 or 0, to enable or disable
5323 this function respectively.
5327 @section @code{.local @var{names}}
5329 @cindex @code{local} directive
5330 This directive, which is available for ELF targets, marks each symbol in
5331 the comma-separated list of @code{names} as a local symbol so that it
5332 will not be externally visible. If the symbols do not already exist,
5333 they will be created.
5335 For targets where the @code{.lcomm} directive (@pxref{Lcomm}) does not
5336 accept an alignment argument, which is the case for most ELF targets,
5337 the @code{.local} directive can be used in combination with @code{.comm}
5338 (@pxref{Comm}) to define aligned local common data.
5342 @section @code{.long @var{expressions}}
5344 @cindex @code{long} directive
5345 @code{.long} is the same as @samp{.int}. @xref{Int,,@code{.int}}.
5348 @c no one seems to know what this is for or whether this description is
5349 @c what it really ought to do
5351 @section @code{.lsym @var{symbol}, @var{expression}}
5353 @cindex @code{lsym} directive
5354 @cindex symbol, not referenced in assembly
5355 @code{.lsym} creates a new symbol named @var{symbol}, but does not put it in
5356 the hash table, ensuring it cannot be referenced by name during the
5357 rest of the assembly. This sets the attributes of the symbol to be
5358 the same as the expression value:
5360 @var{other} = @var{descriptor} = 0
5361 @var{type} = @r{(section of @var{expression})}
5362 @var{value} = @var{expression}
5365 The new symbol is not flagged as external.
5369 @section @code{.macro}
5372 The commands @code{.macro} and @code{.endm} allow you to define macros that
5373 generate assembly output. For example, this definition specifies a macro
5374 @code{sum} that puts a sequence of numbers into memory:
5377 .macro sum from=0, to=5
5386 With that definition, @samp{SUM 0,5} is equivalent to this assembly input:
5398 @item .macro @var{macname}
5399 @itemx .macro @var{macname} @var{macargs} @dots{}
5400 @cindex @code{macro} directive
5401 Begin the definition of a macro called @var{macname}. If your macro
5402 definition requires arguments, specify their names after the macro name,
5403 separated by commas or spaces. You can qualify the macro argument to
5404 indicate whether all invocations must specify a non-blank value (through
5405 @samp{:@code{req}}), or whether it takes all of the remaining arguments
5406 (through @samp{:@code{vararg}}). You can supply a default value for any
5407 macro argument by following the name with @samp{=@var{deflt}}. You
5408 cannot define two macros with the same @var{macname} unless it has been
5409 subject to the @code{.purgem} directive (@pxref{Purgem}) between the two
5410 definitions. For example, these are all valid @code{.macro} statements:
5414 Begin the definition of a macro called @code{comm}, which takes no
5417 @item .macro plus1 p, p1
5418 @itemx .macro plus1 p p1
5419 Either statement begins the definition of a macro called @code{plus1},
5420 which takes two arguments; within the macro definition, write
5421 @samp{\p} or @samp{\p1} to evaluate the arguments.
5423 @item .macro reserve_str p1=0 p2
5424 Begin the definition of a macro called @code{reserve_str}, with two
5425 arguments. The first argument has a default value, but not the second.
5426 After the definition is complete, you can call the macro either as
5427 @samp{reserve_str @var{a},@var{b}} (with @samp{\p1} evaluating to
5428 @var{a} and @samp{\p2} evaluating to @var{b}), or as @samp{reserve_str
5429 ,@var{b}} (with @samp{\p1} evaluating as the default, in this case
5430 @samp{0}, and @samp{\p2} evaluating to @var{b}).
5432 @item .macro m p1:req, p2=0, p3:vararg
5433 Begin the definition of a macro called @code{m}, with at least three
5434 arguments. The first argument must always have a value specified, but
5435 not the second, which instead has a default value. The third formal
5436 will get assigned all remaining arguments specified at invocation time.
5438 When you call a macro, you can specify the argument values either by
5439 position, or by keyword. For example, @samp{sum 9,17} is equivalent to
5440 @samp{sum to=17, from=9}.
5444 Note that since each of the @var{macargs} can be an identifier exactly
5445 as any other one permitted by the target architecture, there may be
5446 occasional problems if the target hand-crafts special meanings to certain
5447 characters when they occur in a special position. For example, if the colon
5448 (@code{:}) is generally permitted to be part of a symbol name, but the
5449 architecture specific code special-cases it when occurring as the final
5450 character of a symbol (to denote a label), then the macro parameter
5451 replacement code will have no way of knowing that and consider the whole
5452 construct (including the colon) an identifier, and check only this
5453 identifier for being the subject to parameter substitution. So for example
5454 this macro definition:
5462 might not work as expected. Invoking @samp{label foo} might not create a label
5463 called @samp{foo} but instead just insert the text @samp{\l:} into the
5464 assembler source, probably generating an error about an unrecognised
5467 Similarly problems might occur with the period character (@samp{.})
5468 which is often allowed inside opcode names (and hence identifier names). So
5469 for example constructing a macro to build an opcode from a base name and a
5470 length specifier like this:
5473 .macro opcode base length
5478 and invoking it as @samp{opcode store l} will not create a @samp{store.l}
5479 instruction but instead generate some kind of error as the assembler tries to
5480 interpret the text @samp{\base.\length}.
5482 There are several possible ways around this problem:
5485 @item Insert white space
5486 If it is possible to use white space characters then this is the simplest
5495 @item Use @samp{\()}
5496 The string @samp{\()} can be used to separate the end of a macro argument from
5497 the following text. eg:
5500 .macro opcode base length
5505 @item Use the alternate macro syntax mode
5506 In the alternative macro syntax mode the ampersand character (@samp{&}) can be
5507 used as a separator. eg:
5517 Note: this problem of correctly identifying string parameters to pseudo ops
5518 also applies to the identifiers used in @code{.irp} (@pxref{Irp})
5519 and @code{.irpc} (@pxref{Irpc}) as well.
5522 @cindex @code{endm} directive
5523 Mark the end of a macro definition.
5526 @cindex @code{exitm} directive
5527 Exit early from the current macro definition.
5529 @cindex number of macros executed
5530 @cindex macros, count executed
5532 @command{@value{AS}} maintains a counter of how many macros it has
5533 executed in this pseudo-variable; you can copy that number to your
5534 output with @samp{\@@}, but @emph{only within a macro definition}.
5536 @item LOCAL @var{name} [ , @dots{} ]
5537 @emph{Warning: @code{LOCAL} is only available if you select ``alternate
5538 macro syntax'' with @samp{--alternate} or @code{.altmacro}.}
5539 @xref{Altmacro,,@code{.altmacro}}.
5543 @section @code{.mri @var{val}}
5545 @cindex @code{mri} directive
5546 @cindex MRI mode, temporarily
5547 If @var{val} is non-zero, this tells @command{@value{AS}} to enter MRI mode. If
5548 @var{val} is zero, this tells @command{@value{AS}} to exit MRI mode. This change
5549 affects code assembled until the next @code{.mri} directive, or until the end
5550 of the file. @xref{M, MRI mode, MRI mode}.
5553 @section @code{.noaltmacro}
5554 Disable alternate macro mode. @xref{Altmacro}.
5557 @section @code{.nolist}
5559 @cindex @code{nolist} directive
5560 @cindex listing control, turning off
5561 Control (in conjunction with the @code{.list} directive) whether or
5562 not assembly listings are generated. These two directives maintain an
5563 internal counter (which is zero initially). @code{.list} increments the
5564 counter, and @code{.nolist} decrements it. Assembly listings are
5565 generated whenever the counter is greater than zero.
5568 @section @code{.octa @var{bignums}}
5570 @c FIXME: double size emitted for "octa" on i960, others? Or warn?
5571 @cindex @code{octa} directive
5572 @cindex integer, 16-byte
5573 @cindex sixteen byte integer
5574 This directive expects zero or more bignums, separated by commas. For each
5575 bignum, it emits a 16-byte integer.
5577 The term ``octa'' comes from contexts in which a ``word'' is two bytes;
5578 hence @emph{octa}-word for 16 bytes.
5581 @section @code{.offset @var{loc}}
5583 @cindex @code{offset} directive
5584 Set the location counter to @var{loc} in the absolute section. @var{loc} must
5585 be an absolute expression. This directive may be useful for defining
5586 symbols with absolute values. Do not confuse it with the @code{.org}
5590 @section @code{.org @var{new-lc} , @var{fill}}
5592 @cindex @code{org} directive
5593 @cindex location counter, advancing
5594 @cindex advancing location counter
5595 @cindex current address, advancing
5596 Advance the location counter of the current section to
5597 @var{new-lc}. @var{new-lc} is either an absolute expression or an
5598 expression with the same section as the current subsection. That is,
5599 you can't use @code{.org} to cross sections: if @var{new-lc} has the
5600 wrong section, the @code{.org} directive is ignored. To be compatible
5601 with former assemblers, if the section of @var{new-lc} is absolute,
5602 @command{@value{AS}} issues a warning, then pretends the section of @var{new-lc}
5603 is the same as the current subsection.
5605 @code{.org} may only increase the location counter, or leave it
5606 unchanged; you cannot use @code{.org} to move the location counter
5609 @c double negative used below "not undefined" because this is a specific
5610 @c reference to "undefined" (as SEG_UNKNOWN is called in this manual)
5611 @c section. doc@cygnus.com 18feb91
5612 Because @command{@value{AS}} tries to assemble programs in one pass, @var{new-lc}
5613 may not be undefined. If you really detest this restriction we eagerly await
5614 a chance to share your improved assembler.
5616 Beware that the origin is relative to the start of the section, not
5617 to the start of the subsection. This is compatible with other
5618 people's assemblers.
5620 When the location counter (of the current subsection) is advanced, the
5621 intervening bytes are filled with @var{fill} which should be an
5622 absolute expression. If the comma and @var{fill} are omitted,
5623 @var{fill} defaults to zero.
5626 @section @code{.p2align[wl] @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
5628 @cindex padding the location counter given a power of two
5629 @cindex @code{p2align} directive
5630 Pad the location counter (in the current subsection) to a particular
5631 storage boundary. The first expression (which must be absolute) is the
5632 number of low-order zero bits the location counter must have after
5633 advancement. For example @samp{.p2align 3} advances the location
5634 counter until it a multiple of 8. If the location counter is already a
5635 multiple of 8, no change is needed.
5637 The second expression (also absolute) gives the fill value to be stored in the
5638 padding bytes. It (and the comma) may be omitted. If it is omitted, the
5639 padding bytes are normally zero. However, on some systems, if the section is
5640 marked as containing code and the fill value is omitted, the space is filled
5641 with no-op instructions.
5643 The third expression is also absolute, and is also optional. If it is present,
5644 it is the maximum number of bytes that should be skipped by this alignment
5645 directive. If doing the alignment would require skipping more bytes than the
5646 specified maximum, then the alignment is not done at all. You can omit the
5647 fill value (the second argument) entirely by simply using two commas after the
5648 required alignment; this can be useful if you want the alignment to be filled
5649 with no-op instructions when appropriate.
5651 @cindex @code{p2alignw} directive
5652 @cindex @code{p2alignl} directive
5653 The @code{.p2alignw} and @code{.p2alignl} directives are variants of the
5654 @code{.p2align} directive. The @code{.p2alignw} directive treats the fill
5655 pattern as a two byte word value. The @code{.p2alignl} directives treats the
5656 fill pattern as a four byte longword value. For example, @code{.p2alignw
5657 2,0x368d} will align to a multiple of 4. If it skips two bytes, they will be
5658 filled in with the value 0x368d (the exact placement of the bytes depends upon
5659 the endianness of the processor). If it skips 1 or 3 bytes, the fill value is
5664 @section @code{.popsection}
5666 @cindex @code{popsection} directive
5667 @cindex Section Stack
5668 This is one of the ELF section stack manipulation directives. The others are
5669 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
5670 @code{.pushsection} (@pxref{PushSection}), and @code{.previous}
5673 This directive replaces the current section (and subsection) with the top
5674 section (and subsection) on the section stack. This section is popped off the
5680 @section @code{.previous}
5682 @cindex @code{previous} directive
5683 @cindex Section Stack
5684 This is one of the ELF section stack manipulation directives. The others are
5685 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
5686 @code{.pushsection} (@pxref{PushSection}), and @code{.popsection}
5687 (@pxref{PopSection}).
5689 This directive swaps the current section (and subsection) with most recently
5690 referenced section/subsection pair prior to this one. Multiple
5691 @code{.previous} directives in a row will flip between two sections (and their
5692 subsections). For example:
5704 Will place 0x1234 and 0x9abc into subsection 1 and 0x5678 into subsection 2 of
5710 # Now in section A subsection 1
5714 # Now in section B subsection 0
5717 # Now in section B subsection 1
5720 # Now in section B subsection 0
5724 Will place 0x1234 into section A, 0x5678 and 0xdef0 into subsection 0 of
5725 section B and 0x9abc into subsection 1 of section B.
5727 In terms of the section stack, this directive swaps the current section with
5728 the top section on the section stack.
5732 @section @code{.print @var{string}}
5734 @cindex @code{print} directive
5735 @command{@value{AS}} will print @var{string} on the standard output during
5736 assembly. You must put @var{string} in double quotes.
5740 @section @code{.protected @var{names}}
5742 @cindex @code{protected} directive
5744 This is one of the ELF visibility directives. The other two are
5745 @code{.hidden} (@pxref{Hidden}) and @code{.internal} (@pxref{Internal}).
5747 This directive overrides the named symbols default visibility (which is set by
5748 their binding: local, global or weak). The directive sets the visibility to
5749 @code{protected} which means that any references to the symbols from within the
5750 components that defines them must be resolved to the definition in that
5751 component, even if a definition in another component would normally preempt
5756 @section @code{.psize @var{lines} , @var{columns}}
5758 @cindex @code{psize} directive
5759 @cindex listing control: paper size
5760 @cindex paper size, for listings
5761 Use this directive to declare the number of lines---and, optionally, the
5762 number of columns---to use for each page, when generating listings.
5764 If you do not use @code{.psize}, listings use a default line-count
5765 of 60. You may omit the comma and @var{columns} specification; the
5766 default width is 200 columns.
5768 @command{@value{AS}} generates formfeeds whenever the specified number of
5769 lines is exceeded (or whenever you explicitly request one, using
5772 If you specify @var{lines} as @code{0}, no formfeeds are generated save
5773 those explicitly specified with @code{.eject}.
5776 @section @code{.purgem @var{name}}
5778 @cindex @code{purgem} directive
5779 Undefine the macro @var{name}, so that later uses of the string will not be
5780 expanded. @xref{Macro}.
5784 @section @code{.pushsection @var{name} [, @var{subsection}] [, "@var{flags}"[, @@@var{type}[,@var{arguments}]]]}
5786 @cindex @code{pushsection} directive
5787 @cindex Section Stack
5788 This is one of the ELF section stack manipulation directives. The others are
5789 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
5790 @code{.popsection} (@pxref{PopSection}), and @code{.previous}
5793 This directive pushes the current section (and subsection) onto the
5794 top of the section stack, and then replaces the current section and
5795 subsection with @code{name} and @code{subsection}. The optional
5796 @code{flags}, @code{type} and @code{arguments} are treated the same
5797 as in the @code{.section} (@pxref{Section}) directive.
5801 @section @code{.quad @var{bignums}}
5803 @cindex @code{quad} directive
5804 @code{.quad} expects zero or more bignums, separated by commas. For
5805 each bignum, it emits
5807 an 8-byte integer. If the bignum won't fit in 8 bytes, it prints a
5808 warning message; and just takes the lowest order 8 bytes of the bignum.
5809 @cindex eight-byte integer
5810 @cindex integer, 8-byte
5812 The term ``quad'' comes from contexts in which a ``word'' is two bytes;
5813 hence @emph{quad}-word for 8 bytes.
5816 a 16-byte integer. If the bignum won't fit in 16 bytes, it prints a
5817 warning message; and just takes the lowest order 16 bytes of the bignum.
5818 @cindex sixteen-byte integer
5819 @cindex integer, 16-byte
5823 @section @code{.reloc @var{offset}, @var{reloc_name}[, @var{expression}]}
5825 @cindex @code{reloc} directive
5826 Generate a relocation at @var{offset} of type @var{reloc_name} with value
5827 @var{expression}. If @var{offset} is a number, the relocation is generated in
5828 the current section. If @var{offset} is an expression that resolves to a
5829 symbol plus offset, the relocation is generated in the given symbol's section.
5830 @var{expression}, if present, must resolve to a symbol plus addend or to an
5831 absolute value, but note that not all targets support an addend. e.g. ELF REL
5832 targets such as i386 store an addend in the section contents rather than in the
5833 relocation. This low level interface does not support addends stored in the
5837 @section @code{.rept @var{count}}
5839 @cindex @code{rept} directive
5840 Repeat the sequence of lines between the @code{.rept} directive and the next
5841 @code{.endr} directive @var{count} times.
5843 For example, assembling
5851 is equivalent to assembling
5860 @section @code{.sbttl "@var{subheading}"}
5862 @cindex @code{sbttl} directive
5863 @cindex subtitles for listings
5864 @cindex listing control: subtitle
5865 Use @var{subheading} as the title (third line, immediately after the
5866 title line) when generating assembly listings.
5868 This directive affects subsequent pages, as well as the current page if
5869 it appears within ten lines of the top of a page.
5873 @section @code{.scl @var{class}}
5875 @cindex @code{scl} directive
5876 @cindex symbol storage class (COFF)
5877 @cindex COFF symbol storage class
5878 Set the storage-class value for a symbol. This directive may only be
5879 used inside a @code{.def}/@code{.endef} pair. Storage class may flag
5880 whether a symbol is static or external, or it may record further
5881 symbolic debugging information.
5884 The @samp{.scl} directive is primarily associated with COFF output; when
5885 configured to generate @code{b.out} output format, @command{@value{AS}}
5886 accepts this directive but ignores it.
5892 @section @code{.section @var{name}}
5894 @cindex named section
5895 Use the @code{.section} directive to assemble the following code into a section
5898 This directive is only supported for targets that actually support arbitrarily
5899 named sections; on @code{a.out} targets, for example, it is not accepted, even
5900 with a standard @code{a.out} section name.
5904 @c only print the extra heading if both COFF and ELF are set
5905 @subheading COFF Version
5908 @cindex @code{section} directive (COFF version)
5909 For COFF targets, the @code{.section} directive is used in one of the following
5913 .section @var{name}[, "@var{flags}"]
5914 .section @var{name}[, @var{subsection}]
5917 If the optional argument is quoted, it is taken as flags to use for the
5918 section. Each flag is a single character. The following flags are recognized:
5921 bss section (uninitialized data)
5923 section is not loaded
5933 shared section (meaningful for PE targets)
5935 ignored. (For compatibility with the ELF version)
5937 section is not readable (meaningful for PE targets)
5939 single-digit power-of-two section alignment (GNU extension)
5942 If no flags are specified, the default flags depend upon the section name. If
5943 the section name is not recognized, the default will be for the section to be
5944 loaded and writable. Note the @code{n} and @code{w} flags remove attributes
5945 from the section, rather than adding them, so if they are used on their own it
5946 will be as if no flags had been specified at all.
5948 If the optional argument to the @code{.section} directive is not quoted, it is
5949 taken as a subsection number (@pxref{Sub-Sections}).
5954 @c only print the extra heading if both COFF and ELF are set
5955 @subheading ELF Version
5958 @cindex Section Stack
5959 This is one of the ELF section stack manipulation directives. The others are
5960 @code{.subsection} (@pxref{SubSection}), @code{.pushsection}
5961 (@pxref{PushSection}), @code{.popsection} (@pxref{PopSection}), and
5962 @code{.previous} (@pxref{Previous}).
5964 @cindex @code{section} directive (ELF version)
5965 For ELF targets, the @code{.section} directive is used like this:
5968 .section @var{name} [, "@var{flags}"[, @@@var{type}[,@var{flag_specific_arguments}]]]
5971 The optional @var{flags} argument is a quoted string which may contain any
5972 combination of the following characters:
5975 section is allocatable
5977 section is excluded from executable and shared library.
5981 section is executable
5983 section is mergeable
5985 section contains zero terminated strings
5987 section is a member of a section group
5989 section is used for thread-local-storage
5991 section is a member of the previously-current section's group, if any
5994 The optional @var{type} argument may contain one of the following constants:
5997 section contains data
5999 section does not contain data (i.e., section only occupies space)
6001 section contains data which is used by things other than the program
6003 section contains an array of pointers to init functions
6005 section contains an array of pointers to finish functions
6006 @item @@preinit_array
6007 section contains an array of pointers to pre-init functions
6010 Many targets only support the first three section types.
6012 Note on targets where the @code{@@} character is the start of a comment (eg
6013 ARM) then another character is used instead. For example the ARM port uses the
6016 If @var{flags} contains the @code{M} symbol then the @var{type} argument must
6017 be specified as well as an extra argument---@var{entsize}---like this:
6020 .section @var{name} , "@var{flags}"M, @@@var{type}, @var{entsize}
6023 Sections with the @code{M} flag but not @code{S} flag must contain fixed size
6024 constants, each @var{entsize} octets long. Sections with both @code{M} and
6025 @code{S} must contain zero terminated strings where each character is
6026 @var{entsize} bytes long. The linker may remove duplicates within sections with
6027 the same name, same entity size and same flags. @var{entsize} must be an
6028 absolute expression. For sections with both @code{M} and @code{S}, a string
6029 which is a suffix of a larger string is considered a duplicate. Thus
6030 @code{"def"} will be merged with @code{"abcdef"}; A reference to the first
6031 @code{"def"} will be changed to a reference to @code{"abcdef"+3}.
6033 If @var{flags} contains the @code{G} symbol then the @var{type} argument must
6034 be present along with an additional field like this:
6037 .section @var{name} , "@var{flags}"G, @@@var{type}, @var{GroupName}[, @var{linkage}]
6040 The @var{GroupName} field specifies the name of the section group to which this
6041 particular section belongs. The optional linkage field can contain:
6044 indicates that only one copy of this section should be retained
6049 Note: if both the @var{M} and @var{G} flags are present then the fields for
6050 the Merge flag should come first, like this:
6053 .section @var{name} , "@var{flags}"MG, @@@var{type}, @var{entsize}, @var{GroupName}[, @var{linkage}]
6056 If @var{flags} contains the @code{?} symbol then it may not also contain the
6057 @code{G} symbol and the @var{GroupName} or @var{linkage} fields should not be
6058 present. Instead, @code{?} says to consider the section that's current before
6059 this directive. If that section used @code{G}, then the new section will use
6060 @code{G} with those same @var{GroupName} and @var{linkage} fields implicitly.
6061 If not, then the @code{?} symbol has no effect.
6063 If no flags are specified, the default flags depend upon the section name. If
6064 the section name is not recognized, the default will be for the section to have
6065 none of the above flags: it will not be allocated in memory, nor writable, nor
6066 executable. The section will contain data.
6068 For ELF targets, the assembler supports another type of @code{.section}
6069 directive for compatibility with the Solaris assembler:
6072 .section "@var{name}"[, @var{flags}...]
6075 Note that the section name is quoted. There may be a sequence of comma
6079 section is allocatable
6083 section is executable
6085 section is excluded from executable and shared library.
6087 section is used for thread local storage
6090 This directive replaces the current section and subsection. See the
6091 contents of the gas testsuite directory @code{gas/testsuite/gas/elf} for
6092 some examples of how this directive and the other section stack directives
6098 @section @code{.set @var{symbol}, @var{expression}}
6100 @cindex @code{set} directive
6101 @cindex symbol value, setting
6102 Set the value of @var{symbol} to @var{expression}. This
6103 changes @var{symbol}'s value and type to conform to
6104 @var{expression}. If @var{symbol} was flagged as external, it remains
6105 flagged (@pxref{Symbol Attributes}).
6107 You may @code{.set} a symbol many times in the same assembly.
6109 If you @code{.set} a global symbol, the value stored in the object
6110 file is the last value stored into it.
6113 On Z80 @code{set} is a real instruction, use
6114 @samp{@var{symbol} defl @var{expression}} instead.
6118 @section @code{.short @var{expressions}}
6120 @cindex @code{short} directive
6122 @code{.short} is normally the same as @samp{.word}.
6123 @xref{Word,,@code{.word}}.
6125 In some configurations, however, @code{.short} and @code{.word} generate
6126 numbers of different lengths. @xref{Machine Dependencies}.
6130 @code{.short} is the same as @samp{.word}. @xref{Word,,@code{.word}}.
6133 This expects zero or more @var{expressions}, and emits
6134 a 16 bit number for each.
6139 @section @code{.single @var{flonums}}
6141 @cindex @code{single} directive
6142 @cindex floating point numbers (single)
6143 This directive assembles zero or more flonums, separated by commas. It
6144 has the same effect as @code{.float}.
6146 The exact kind of floating point numbers emitted depends on how
6147 @command{@value{AS}} is configured. @xref{Machine Dependencies}.
6151 On the @value{TARGET} family, @code{.single} emits 32-bit floating point
6152 numbers in @sc{ieee} format.
6158 @section @code{.size}
6160 This directive is used to set the size associated with a symbol.
6164 @c only print the extra heading if both COFF and ELF are set
6165 @subheading COFF Version
6168 @cindex @code{size} directive (COFF version)
6169 For COFF targets, the @code{.size} directive is only permitted inside
6170 @code{.def}/@code{.endef} pairs. It is used like this:
6173 .size @var{expression}
6177 @samp{.size} is only meaningful when generating COFF format output; when
6178 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
6185 @c only print the extra heading if both COFF and ELF are set
6186 @subheading ELF Version
6189 @cindex @code{size} directive (ELF version)
6190 For ELF targets, the @code{.size} directive is used like this:
6193 .size @var{name} , @var{expression}
6196 This directive sets the size associated with a symbol @var{name}.
6197 The size in bytes is computed from @var{expression} which can make use of label
6198 arithmetic. This directive is typically used to set the size of function
6203 @ifclear no-space-dir
6205 @section @code{.skip @var{size} , @var{fill}}
6207 @cindex @code{skip} directive
6208 @cindex filling memory
6209 This directive emits @var{size} bytes, each of value @var{fill}. Both
6210 @var{size} and @var{fill} are absolute expressions. If the comma and
6211 @var{fill} are omitted, @var{fill} is assumed to be zero. This is the same as
6216 @section @code{.sleb128 @var{expressions}}
6218 @cindex @code{sleb128} directive
6219 @var{sleb128} stands for ``signed little endian base 128.'' This is a
6220 compact, variable length representation of numbers used by the DWARF
6221 symbolic debugging format. @xref{Uleb128, ,@code{.uleb128}}.
6223 @ifclear no-space-dir
6225 @section @code{.space @var{size} , @var{fill}}
6227 @cindex @code{space} directive
6228 @cindex filling memory
6229 This directive emits @var{size} bytes, each of value @var{fill}. Both
6230 @var{size} and @var{fill} are absolute expressions. If the comma
6231 and @var{fill} are omitted, @var{fill} is assumed to be zero. This is the same
6236 @emph{Warning:} @code{.space} has a completely different meaning for HPPA
6237 targets; use @code{.block} as a substitute. See @cite{HP9000 Series 800
6238 Assembly Language Reference Manual} (HP 92432-90001) for the meaning of the
6239 @code{.space} directive. @xref{HPPA Directives,,HPPA Assembler Directives},
6247 @section @code{.stabd, .stabn, .stabs}
6249 @cindex symbolic debuggers, information for
6250 @cindex @code{stab@var{x}} directives
6251 There are three directives that begin @samp{.stab}.
6252 All emit symbols (@pxref{Symbols}), for use by symbolic debuggers.
6253 The symbols are not entered in the @command{@value{AS}} hash table: they
6254 cannot be referenced elsewhere in the source file.
6255 Up to five fields are required:
6259 This is the symbol's name. It may contain any character except
6260 @samp{\000}, so is more general than ordinary symbol names. Some
6261 debuggers used to code arbitrarily complex structures into symbol names
6265 An absolute expression. The symbol's type is set to the low 8 bits of
6266 this expression. Any bit pattern is permitted, but @code{@value{LD}}
6267 and debuggers choke on silly bit patterns.
6270 An absolute expression. The symbol's ``other'' attribute is set to the
6271 low 8 bits of this expression.
6274 An absolute expression. The symbol's descriptor is set to the low 16
6275 bits of this expression.
6278 An absolute expression which becomes the symbol's value.
6281 If a warning is detected while reading a @code{.stabd}, @code{.stabn},
6282 or @code{.stabs} statement, the symbol has probably already been created;
6283 you get a half-formed symbol in your object file. This is
6284 compatible with earlier assemblers!
6287 @cindex @code{stabd} directive
6288 @item .stabd @var{type} , @var{other} , @var{desc}
6290 The ``name'' of the symbol generated is not even an empty string.
6291 It is a null pointer, for compatibility. Older assemblers used a
6292 null pointer so they didn't waste space in object files with empty
6295 The symbol's value is set to the location counter,
6296 relocatably. When your program is linked, the value of this symbol
6297 is the address of the location counter when the @code{.stabd} was
6300 @cindex @code{stabn} directive
6301 @item .stabn @var{type} , @var{other} , @var{desc} , @var{value}
6302 The name of the symbol is set to the empty string @code{""}.
6304 @cindex @code{stabs} directive
6305 @item .stabs @var{string} , @var{type} , @var{other} , @var{desc} , @var{value}
6306 All five fields are specified.
6312 @section @code{.string} "@var{str}", @code{.string8} "@var{str}", @code{.string16}
6313 "@var{str}", @code{.string32} "@var{str}", @code{.string64} "@var{str}"
6315 @cindex string, copying to object file
6316 @cindex string8, copying to object file
6317 @cindex string16, copying to object file
6318 @cindex string32, copying to object file
6319 @cindex string64, copying to object file
6320 @cindex @code{string} directive
6321 @cindex @code{string8} directive
6322 @cindex @code{string16} directive
6323 @cindex @code{string32} directive
6324 @cindex @code{string64} directive
6326 Copy the characters in @var{str} to the object file. You may specify more than
6327 one string to copy, separated by commas. Unless otherwise specified for a
6328 particular machine, the assembler marks the end of each string with a 0 byte.
6329 You can use any of the escape sequences described in @ref{Strings,,Strings}.
6331 The variants @code{string16}, @code{string32} and @code{string64} differ from
6332 the @code{string} pseudo opcode in that each 8-bit character from @var{str} is
6333 copied and expanded to 16, 32 or 64 bits respectively. The expanded characters
6334 are stored in target endianness byte order.
6340 .string "B\0\0\0Y\0\0\0E\0\0\0" /* On little endian targets. */
6341 .string "\0\0\0B\0\0\0Y\0\0\0E" /* On big endian targets. */
6346 @section @code{.struct @var{expression}}
6348 @cindex @code{struct} directive
6349 Switch to the absolute section, and set the section offset to @var{expression},
6350 which must be an absolute expression. You might use this as follows:
6359 This would define the symbol @code{field1} to have the value 0, the symbol
6360 @code{field2} to have the value 4, and the symbol @code{field3} to have the
6361 value 8. Assembly would be left in the absolute section, and you would need to
6362 use a @code{.section} directive of some sort to change to some other section
6363 before further assembly.
6367 @section @code{.subsection @var{name}}
6369 @cindex @code{subsection} directive
6370 @cindex Section Stack
6371 This is one of the ELF section stack manipulation directives. The others are
6372 @code{.section} (@pxref{Section}), @code{.pushsection} (@pxref{PushSection}),
6373 @code{.popsection} (@pxref{PopSection}), and @code{.previous}
6376 This directive replaces the current subsection with @code{name}. The current
6377 section is not changed. The replaced subsection is put onto the section stack
6378 in place of the then current top of stack subsection.
6383 @section @code{.symver}
6384 @cindex @code{symver} directive
6385 @cindex symbol versioning
6386 @cindex versions of symbols
6387 Use the @code{.symver} directive to bind symbols to specific version nodes
6388 within a source file. This is only supported on ELF platforms, and is
6389 typically used when assembling files to be linked into a shared library.
6390 There are cases where it may make sense to use this in objects to be bound
6391 into an application itself so as to override a versioned symbol from a
6394 For ELF targets, the @code{.symver} directive can be used like this:
6396 .symver @var{name}, @var{name2@@nodename}
6398 If the symbol @var{name} is defined within the file
6399 being assembled, the @code{.symver} directive effectively creates a symbol
6400 alias with the name @var{name2@@nodename}, and in fact the main reason that we
6401 just don't try and create a regular alias is that the @var{@@} character isn't
6402 permitted in symbol names. The @var{name2} part of the name is the actual name
6403 of the symbol by which it will be externally referenced. The name @var{name}
6404 itself is merely a name of convenience that is used so that it is possible to
6405 have definitions for multiple versions of a function within a single source
6406 file, and so that the compiler can unambiguously know which version of a
6407 function is being mentioned. The @var{nodename} portion of the alias should be
6408 the name of a node specified in the version script supplied to the linker when
6409 building a shared library. If you are attempting to override a versioned
6410 symbol from a shared library, then @var{nodename} should correspond to the
6411 nodename of the symbol you are trying to override.
6413 If the symbol @var{name} is not defined within the file being assembled, all
6414 references to @var{name} will be changed to @var{name2@@nodename}. If no
6415 reference to @var{name} is made, @var{name2@@nodename} will be removed from the
6418 Another usage of the @code{.symver} directive is:
6420 .symver @var{name}, @var{name2@@@@nodename}
6422 In this case, the symbol @var{name} must exist and be defined within
6423 the file being assembled. It is similar to @var{name2@@nodename}. The
6424 difference is @var{name2@@@@nodename} will also be used to resolve
6425 references to @var{name2} by the linker.
6427 The third usage of the @code{.symver} directive is:
6429 .symver @var{name}, @var{name2@@@@@@nodename}
6431 When @var{name} is not defined within the
6432 file being assembled, it is treated as @var{name2@@nodename}. When
6433 @var{name} is defined within the file being assembled, the symbol
6434 name, @var{name}, will be changed to @var{name2@@@@nodename}.
6439 @section @code{.tag @var{structname}}
6441 @cindex COFF structure debugging
6442 @cindex structure debugging, COFF
6443 @cindex @code{tag} directive
6444 This directive is generated by compilers to include auxiliary debugging
6445 information in the symbol table. It is only permitted inside
6446 @code{.def}/@code{.endef} pairs. Tags are used to link structure
6447 definitions in the symbol table with instances of those structures.
6450 @samp{.tag} is only used when generating COFF format output; when
6451 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
6457 @section @code{.text @var{subsection}}
6459 @cindex @code{text} directive
6460 Tells @command{@value{AS}} to assemble the following statements onto the end of
6461 the text subsection numbered @var{subsection}, which is an absolute
6462 expression. If @var{subsection} is omitted, subsection number zero
6466 @section @code{.title "@var{heading}"}
6468 @cindex @code{title} directive
6469 @cindex listing control: title line
6470 Use @var{heading} as the title (second line, immediately after the
6471 source file name and pagenumber) when generating assembly listings.
6473 This directive affects subsequent pages, as well as the current page if
6474 it appears within ten lines of the top of a page.
6478 @section @code{.type}
6480 This directive is used to set the type of a symbol.
6484 @c only print the extra heading if both COFF and ELF are set
6485 @subheading COFF Version
6488 @cindex COFF symbol type
6489 @cindex symbol type, COFF
6490 @cindex @code{type} directive (COFF version)
6491 For COFF targets, this directive is permitted only within
6492 @code{.def}/@code{.endef} pairs. It is used like this:
6498 This records the integer @var{int} as the type attribute of a symbol table
6502 @samp{.type} is associated only with COFF format output; when
6503 @command{@value{AS}} is configured for @code{b.out} output, it accepts this
6504 directive but ignores it.
6510 @c only print the extra heading if both COFF and ELF are set
6511 @subheading ELF Version
6514 @cindex ELF symbol type
6515 @cindex symbol type, ELF
6516 @cindex @code{type} directive (ELF version)
6517 For ELF targets, the @code{.type} directive is used like this:
6520 .type @var{name} , @var{type description}
6523 This sets the type of symbol @var{name} to be either a
6524 function symbol or an object symbol. There are five different syntaxes
6525 supported for the @var{type description} field, in order to provide
6526 compatibility with various other assemblers.
6528 Because some of the characters used in these syntaxes (such as @samp{@@} and
6529 @samp{#}) are comment characters for some architectures, some of the syntaxes
6530 below do not work on all architectures. The first variant will be accepted by
6531 the GNU assembler on all architectures so that variant should be used for
6532 maximum portability, if you do not need to assemble your code with other
6535 The syntaxes supported are:
6538 .type <name> STT_<TYPE_IN_UPPER_CASE>
6539 .type <name>,#<type>
6540 .type <name>,@@<type>
6541 .type <name>,%<type>
6542 .type <name>,"<type>"
6545 The types supported are:
6550 Mark the symbol as being a function name.
6553 @itemx gnu_indirect_function
6554 Mark the symbol as an indirect function when evaluated during reloc
6555 processing. (This is only supported on assemblers targeting GNU systems).
6559 Mark the symbol as being a data object.
6563 Mark the symbol as being a thead-local data object.
6567 Mark the symbol as being a common data object.
6571 Does not mark the symbol in any way. It is supported just for completeness.
6573 @item gnu_unique_object
6574 Marks the symbol as being a globally unique data object. The dynamic linker
6575 will make sure that in the entire process there is just one symbol with this
6576 name and type in use. (This is only supported on assemblers targeting GNU
6581 Note: Some targets support extra types in addition to those listed above.
6587 @section @code{.uleb128 @var{expressions}}
6589 @cindex @code{uleb128} directive
6590 @var{uleb128} stands for ``unsigned little endian base 128.'' This is a
6591 compact, variable length representation of numbers used by the DWARF
6592 symbolic debugging format. @xref{Sleb128, ,@code{.sleb128}}.
6596 @section @code{.val @var{addr}}
6598 @cindex @code{val} directive
6599 @cindex COFF value attribute
6600 @cindex value attribute, COFF
6601 This directive, permitted only within @code{.def}/@code{.endef} pairs,
6602 records the address @var{addr} as the value attribute of a symbol table
6606 @samp{.val} is used only for COFF output; when @command{@value{AS}} is
6607 configured for @code{b.out}, it accepts this directive but ignores it.
6613 @section @code{.version "@var{string}"}
6615 @cindex @code{version} directive
6616 This directive creates a @code{.note} section and places into it an ELF
6617 formatted note of type NT_VERSION. The note's name is set to @code{string}.
6622 @section @code{.vtable_entry @var{table}, @var{offset}}
6624 @cindex @code{vtable_entry} directive
6625 This directive finds or creates a symbol @code{table} and creates a
6626 @code{VTABLE_ENTRY} relocation for it with an addend of @code{offset}.
6629 @section @code{.vtable_inherit @var{child}, @var{parent}}
6631 @cindex @code{vtable_inherit} directive
6632 This directive finds the symbol @code{child} and finds or creates the symbol
6633 @code{parent} and then creates a @code{VTABLE_INHERIT} relocation for the
6634 parent whose addend is the value of the child symbol. As a special case the
6635 parent name of @code{0} is treated as referring to the @code{*ABS*} section.
6639 @section @code{.warning "@var{string}"}
6640 @cindex warning directive
6641 Similar to the directive @code{.error}
6642 (@pxref{Error,,@code{.error "@var{string}"}}), but just emits a warning.
6645 @section @code{.weak @var{names}}
6647 @cindex @code{weak} directive
6648 This directive sets the weak attribute on the comma separated list of symbol
6649 @code{names}. If the symbols do not already exist, they will be created.
6651 On COFF targets other than PE, weak symbols are a GNU extension. This
6652 directive sets the weak attribute on the comma separated list of symbol
6653 @code{names}. If the symbols do not already exist, they will be created.
6655 On the PE target, weak symbols are supported natively as weak aliases.
6656 When a weak symbol is created that is not an alias, GAS creates an
6657 alternate symbol to hold the default value.
6660 @section @code{.weakref @var{alias}, @var{target}}
6662 @cindex @code{weakref} directive
6663 This directive creates an alias to the target symbol that enables the symbol to
6664 be referenced with weak-symbol semantics, but without actually making it weak.
6665 If direct references or definitions of the symbol are present, then the symbol
6666 will not be weak, but if all references to it are through weak references, the
6667 symbol will be marked as weak in the symbol table.
6669 The effect is equivalent to moving all references to the alias to a separate
6670 assembly source file, renaming the alias to the symbol in it, declaring the
6671 symbol as weak there, and running a reloadable link to merge the object files
6672 resulting from the assembly of the new source file and the old source file that
6673 had the references to the alias removed.
6675 The alias itself never makes to the symbol table, and is entirely handled
6676 within the assembler.
6679 @section @code{.word @var{expressions}}
6681 @cindex @code{word} directive
6682 This directive expects zero or more @var{expressions}, of any section,
6683 separated by commas.
6686 For each expression, @command{@value{AS}} emits a 32-bit number.
6689 For each expression, @command{@value{AS}} emits a 16-bit number.
6694 The size of the number emitted, and its byte order,
6695 depend on what target computer the assembly is for.
6698 @c on amd29k, i960, sparc the "special treatment to support compilers" doesn't
6699 @c happen---32-bit addressability, period; no long/short jumps.
6700 @ifset DIFF-TBL-KLUGE
6701 @cindex difference tables altered
6702 @cindex altered difference tables
6704 @emph{Warning: Special Treatment to support Compilers}
6708 Machines with a 32-bit address space, but that do less than 32-bit
6709 addressing, require the following special treatment. If the machine of
6710 interest to you does 32-bit addressing (or doesn't require it;
6711 @pxref{Machine Dependencies}), you can ignore this issue.
6714 In order to assemble compiler output into something that works,
6715 @command{@value{AS}} occasionally does strange things to @samp{.word} directives.
6716 Directives of the form @samp{.word sym1-sym2} are often emitted by
6717 compilers as part of jump tables. Therefore, when @command{@value{AS}} assembles a
6718 directive of the form @samp{.word sym1-sym2}, and the difference between
6719 @code{sym1} and @code{sym2} does not fit in 16 bits, @command{@value{AS}}
6720 creates a @dfn{secondary jump table}, immediately before the next label.
6721 This secondary jump table is preceded by a short-jump to the
6722 first byte after the secondary table. This short-jump prevents the flow
6723 of control from accidentally falling into the new table. Inside the
6724 table is a long-jump to @code{sym2}. The original @samp{.word}
6725 contains @code{sym1} minus the address of the long-jump to
6728 If there were several occurrences of @samp{.word sym1-sym2} before the
6729 secondary jump table, all of them are adjusted. If there was a
6730 @samp{.word sym3-sym4}, that also did not fit in sixteen bits, a
6731 long-jump to @code{sym4} is included in the secondary jump table,
6732 and the @code{.word} directives are adjusted to contain @code{sym3}
6733 minus the address of the long-jump to @code{sym4}; and so on, for as many
6734 entries in the original jump table as necessary.
6737 @emph{This feature may be disabled by compiling @command{@value{AS}} with the
6738 @samp{-DWORKING_DOT_WORD} option.} This feature is likely to confuse
6739 assembly language programmers.
6742 @c end DIFF-TBL-KLUGE
6745 @section Deprecated Directives
6747 @cindex deprecated directives
6748 @cindex obsolescent directives
6749 One day these directives won't work.
6750 They are included for compatibility with older assemblers.
6757 @node Object Attributes
6758 @chapter Object Attributes
6759 @cindex object attributes
6761 @command{@value{AS}} assembles source files written for a specific architecture
6762 into object files for that architecture. But not all object files are alike.
6763 Many architectures support incompatible variations. For instance, floating
6764 point arguments might be passed in floating point registers if the object file
6765 requires hardware floating point support---or floating point arguments might be
6766 passed in integer registers if the object file supports processors with no
6767 hardware floating point unit. Or, if two objects are built for different
6768 generations of the same architecture, the combination may require the
6769 newer generation at run-time.
6771 This information is useful during and after linking. At link time,
6772 @command{@value{LD}} can warn about incompatible object files. After link
6773 time, tools like @command{gdb} can use it to process the linked file
6776 Compatibility information is recorded as a series of object attributes. Each
6777 attribute has a @dfn{vendor}, @dfn{tag}, and @dfn{value}. The vendor is a
6778 string, and indicates who sets the meaning of the tag. The tag is an integer,
6779 and indicates what property the attribute describes. The value may be a string
6780 or an integer, and indicates how the property affects this object. Missing
6781 attributes are the same as attributes with a zero value or empty string value.
6783 Object attributes were developed as part of the ABI for the ARM Architecture.
6784 The file format is documented in @cite{ELF for the ARM Architecture}.
6787 * GNU Object Attributes:: @sc{gnu} Object Attributes
6788 * Defining New Object Attributes:: Defining New Object Attributes
6791 @node GNU Object Attributes
6792 @section @sc{gnu} Object Attributes
6794 The @code{.gnu_attribute} directive records an object attribute
6795 with vendor @samp{gnu}.
6797 Except for @samp{Tag_compatibility}, which has both an integer and a string for
6798 its value, @sc{gnu} attributes have a string value if the tag number is odd and
6799 an integer value if the tag number is even. The second bit (@code{@var{tag} &
6800 2} is set for architecture-independent attributes and clear for
6801 architecture-dependent ones.
6803 @subsection Common @sc{gnu} attributes
6805 These attributes are valid on all architectures.
6808 @item Tag_compatibility (32)
6809 The compatibility attribute takes an integer flag value and a vendor name. If
6810 the flag value is 0, the file is compatible with other toolchains. If it is 1,
6811 then the file is only compatible with the named toolchain. If it is greater
6812 than 1, the file can only be processed by other toolchains under some private
6813 arrangement indicated by the flag value and the vendor name.
6816 @subsection MIPS Attributes
6819 @item Tag_GNU_MIPS_ABI_FP (4)
6820 The floating-point ABI used by this object file. The value will be:
6824 0 for files not affected by the floating-point ABI.
6826 1 for files using the hardware floating-point with a standard double-precision
6829 2 for files using the hardware floating-point ABI with a single-precision FPU.
6831 3 for files using the software floating-point ABI.
6833 4 for files using the hardware floating-point ABI with 64-bit wide
6834 double-precision floating-point registers and 32-bit wide general
6839 @subsection PowerPC Attributes
6842 @item Tag_GNU_Power_ABI_FP (4)
6843 The floating-point ABI used by this object file. The value will be:
6847 0 for files not affected by the floating-point ABI.
6849 1 for files using double-precision hardware floating-point ABI.
6851 2 for files using the software floating-point ABI.
6853 3 for files using single-precision hardware floating-point ABI.
6856 @item Tag_GNU_Power_ABI_Vector (8)
6857 The vector ABI used by this object file. The value will be:
6861 0 for files not affected by the vector ABI.
6863 1 for files using general purpose registers to pass vectors.
6865 2 for files using AltiVec registers to pass vectors.
6867 3 for files using SPE registers to pass vectors.
6871 @node Defining New Object Attributes
6872 @section Defining New Object Attributes
6874 If you want to define a new @sc{gnu} object attribute, here are the places you
6875 will need to modify. New attributes should be discussed on the @samp{binutils}
6880 This manual, which is the official register of attributes.
6882 The header for your architecture @file{include/elf}, to define the tag.
6884 The @file{bfd} support file for your architecture, to merge the attribute
6885 and issue any appropriate link warnings.
6887 Test cases in @file{ld/testsuite} for merging and link warnings.
6889 @file{binutils/readelf.c} to display your attribute.
6891 GCC, if you want the compiler to mark the attribute automatically.
6897 @node Machine Dependencies
6898 @chapter Machine Dependent Features
6900 @cindex machine dependencies
6901 The machine instruction sets are (almost by definition) different on
6902 each machine where @command{@value{AS}} runs. Floating point representations
6903 vary as well, and @command{@value{AS}} often supports a few additional
6904 directives or command-line options for compatibility with other
6905 assemblers on a particular platform. Finally, some versions of
6906 @command{@value{AS}} support special pseudo-instructions for branch
6909 This chapter discusses most of these differences, though it does not
6910 include details on any machine's instruction set. For details on that
6911 subject, see the hardware manufacturer's manual.
6915 * Alpha-Dependent:: Alpha Dependent Features
6918 * ARC-Dependent:: ARC Dependent Features
6921 * ARM-Dependent:: ARM Dependent Features
6924 * AVR-Dependent:: AVR Dependent Features
6927 * Blackfin-Dependent:: Blackfin Dependent Features
6930 * CR16-Dependent:: CR16 Dependent Features
6933 * CRIS-Dependent:: CRIS Dependent Features
6936 * D10V-Dependent:: D10V Dependent Features
6939 * D30V-Dependent:: D30V Dependent Features
6942 * Epiphany-Dependent:: EPIPHANY Dependent Features
6945 * H8/300-Dependent:: Renesas H8/300 Dependent Features
6948 * HPPA-Dependent:: HPPA Dependent Features
6951 * ESA/390-Dependent:: IBM ESA/390 Dependent Features
6954 * i386-Dependent:: Intel 80386 and AMD x86-64 Dependent Features
6957 * i860-Dependent:: Intel 80860 Dependent Features
6960 * i960-Dependent:: Intel 80960 Dependent Features
6963 * IA-64-Dependent:: Intel IA-64 Dependent Features
6966 * IP2K-Dependent:: IP2K Dependent Features
6969 * LM32-Dependent:: LM32 Dependent Features
6972 * M32C-Dependent:: M32C Dependent Features
6975 * M32R-Dependent:: M32R Dependent Features
6978 * M68K-Dependent:: M680x0 Dependent Features
6981 * M68HC11-Dependent:: M68HC11 and 68HC12 Dependent Features
6984 * MicroBlaze-Dependent:: MICROBLAZE Dependent Features
6987 * MIPS-Dependent:: MIPS Dependent Features
6990 * MMIX-Dependent:: MMIX Dependent Features
6993 * MSP430-Dependent:: MSP430 Dependent Features
6996 * NS32K-Dependent:: NS32K Dependent Features
6999 * SH-Dependent:: Renesas / SuperH SH Dependent Features
7000 * SH64-Dependent:: SuperH SH64 Dependent Features
7003 * PDP-11-Dependent:: PDP-11 Dependent Features
7006 * PJ-Dependent:: picoJava Dependent Features
7009 * PPC-Dependent:: PowerPC Dependent Features
7012 * RL78-Dependent:: RL78 Dependent Features
7015 * RX-Dependent:: RX Dependent Features
7018 * S/390-Dependent:: IBM S/390 Dependent Features
7021 * SCORE-Dependent:: SCORE Dependent Features
7024 * Sparc-Dependent:: SPARC Dependent Features
7027 * TIC54X-Dependent:: TI TMS320C54x Dependent Features
7030 * TIC6X-Dependent :: TI TMS320C6x Dependent Features
7033 * TILE-Gx-Dependent :: Tilera TILE-Gx Dependent Features
7036 * TILEPro-Dependent :: Tilera TILEPro Dependent Features
7039 * V850-Dependent:: V850 Dependent Features
7042 * XGATE-Dependent:: XGATE Features
7045 * XSTORMY16-Dependent:: XStormy16 Dependent Features
7048 * Xtensa-Dependent:: Xtensa Dependent Features
7051 * Z80-Dependent:: Z80 Dependent Features
7054 * Z8000-Dependent:: Z8000 Dependent Features
7057 * Vax-Dependent:: VAX Dependent Features
7064 @c The following major nodes are *sections* in the GENERIC version, *chapters*
7065 @c in single-cpu versions. This is mainly achieved by @lowersections. There is a
7066 @c peculiarity: to preserve cross-references, there must be a node called
7067 @c "Machine Dependencies". Hence the conditional nodenames in each
7068 @c major node below. Node defaulting in makeinfo requires adjacency of
7069 @c node and sectioning commands; hence the repetition of @chapter BLAH
7070 @c in both conditional blocks.
7073 @include c-alpha.texi
7089 @include c-bfin.texi
7093 @include c-cr16.texi
7097 @include c-cris.texi
7102 @node Machine Dependencies
7103 @chapter Machine Dependent Features
7105 The machine instruction sets are different on each Renesas chip family,
7106 and there are also some syntax differences among the families. This
7107 chapter describes the specific @command{@value{AS}} features for each
7111 * H8/300-Dependent:: Renesas H8/300 Dependent Features
7112 * SH-Dependent:: Renesas SH Dependent Features
7119 @include c-d10v.texi
7123 @include c-d30v.texi
7127 @include c-epiphany.texi
7131 @include c-h8300.texi
7135 @include c-hppa.texi
7139 @include c-i370.texi
7143 @include c-i386.texi
7147 @include c-i860.texi
7151 @include c-i960.texi
7155 @include c-ia64.texi
7159 @include c-ip2k.texi
7163 @include c-lm32.texi
7167 @include c-m32c.texi
7171 @include c-m32r.texi
7175 @include c-m68k.texi
7179 @include c-m68hc11.texi
7183 @include c-microblaze.texi
7187 @include c-mips.texi
7191 @include c-mmix.texi
7195 @include c-msp430.texi
7199 @include c-ns32k.texi
7203 @include c-pdp11.texi
7215 @include c-rl78.texi
7223 @include c-s390.texi
7227 @include c-score.texi
7232 @include c-sh64.texi
7236 @include c-sparc.texi
7240 @include c-tic54x.texi
7244 @include c-tic6x.texi
7248 @include c-tilegx.texi
7252 @include c-tilepro.texi
7268 @include c-v850.texi
7272 @include c-xgate.texi
7276 @include c-xstormy16.texi
7280 @include c-xtensa.texi
7284 @c reverse effect of @down at top of generic Machine-Dep chapter
7288 @node Reporting Bugs
7289 @chapter Reporting Bugs
7290 @cindex bugs in assembler
7291 @cindex reporting bugs in assembler
7293 Your bug reports play an essential role in making @command{@value{AS}} reliable.
7295 Reporting a bug may help you by bringing a solution to your problem, or it may
7296 not. But in any case the principal function of a bug report is to help the
7297 entire community by making the next version of @command{@value{AS}} work better.
7298 Bug reports are your contribution to the maintenance of @command{@value{AS}}.
7300 In order for a bug report to serve its purpose, you must include the
7301 information that enables us to fix the bug.
7304 * Bug Criteria:: Have you found a bug?
7305 * Bug Reporting:: How to report bugs
7309 @section Have You Found a Bug?
7310 @cindex bug criteria
7312 If you are not sure whether you have found a bug, here are some guidelines:
7315 @cindex fatal signal
7316 @cindex assembler crash
7317 @cindex crash of assembler
7319 If the assembler gets a fatal signal, for any input whatever, that is a
7320 @command{@value{AS}} bug. Reliable assemblers never crash.
7322 @cindex error on valid input
7324 If @command{@value{AS}} produces an error message for valid input, that is a bug.
7326 @cindex invalid input
7328 If @command{@value{AS}} does not produce an error message for invalid input, that
7329 is a bug. However, you should note that your idea of ``invalid input'' might
7330 be our idea of ``an extension'' or ``support for traditional practice''.
7333 If you are an experienced user of assemblers, your suggestions for improvement
7334 of @command{@value{AS}} are welcome in any case.
7338 @section How to Report Bugs
7340 @cindex assembler bugs, reporting
7342 A number of companies and individuals offer support for @sc{gnu} products. If
7343 you obtained @command{@value{AS}} from a support organization, we recommend you
7344 contact that organization first.
7346 You can find contact information for many support companies and
7347 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
7351 In any event, we also recommend that you send bug reports for @command{@value{AS}}
7355 The fundamental principle of reporting bugs usefully is this:
7356 @strong{report all the facts}. If you are not sure whether to state a
7357 fact or leave it out, state it!
7359 Often people omit facts because they think they know what causes the problem
7360 and assume that some details do not matter. Thus, you might assume that the
7361 name of a symbol you use in an example does not matter. Well, probably it does
7362 not, but one cannot be sure. Perhaps the bug is a stray memory reference which
7363 happens to fetch from the location where that name is stored in memory;
7364 perhaps, if the name were different, the contents of that location would fool
7365 the assembler into doing the right thing despite the bug. Play it safe and
7366 give a specific, complete example. That is the easiest thing for you to do,
7367 and the most helpful.
7369 Keep in mind that the purpose of a bug report is to enable us to fix the bug if
7370 it is new to us. Therefore, always write your bug reports on the assumption
7371 that the bug has not been reported previously.
7373 Sometimes people give a few sketchy facts and ask, ``Does this ring a
7374 bell?'' This cannot help us fix a bug, so it is basically useless. We
7375 respond by asking for enough details to enable us to investigate.
7376 You might as well expedite matters by sending them to begin with.
7378 To enable us to fix the bug, you should include all these things:
7382 The version of @command{@value{AS}}. @command{@value{AS}} announces it if you start
7383 it with the @samp{--version} argument.
7385 Without this, we will not know whether there is any point in looking for
7386 the bug in the current version of @command{@value{AS}}.
7389 Any patches you may have applied to the @command{@value{AS}} source.
7392 The type of machine you are using, and the operating system name and
7396 What compiler (and its version) was used to compile @command{@value{AS}}---e.g.
7400 The command arguments you gave the assembler to assemble your example and
7401 observe the bug. To guarantee you will not omit something important, list them
7402 all. A copy of the Makefile (or the output from make) is sufficient.
7404 If we were to try to guess the arguments, we would probably guess wrong
7405 and then we might not encounter the bug.
7408 A complete input file that will reproduce the bug. If the bug is observed when
7409 the assembler is invoked via a compiler, send the assembler source, not the
7410 high level language source. Most compilers will produce the assembler source
7411 when run with the @samp{-S} option. If you are using @code{@value{GCC}}, use
7412 the options @samp{-v --save-temps}; this will save the assembler source in a
7413 file with an extension of @file{.s}, and also show you exactly how
7414 @command{@value{AS}} is being run.
7417 A description of what behavior you observe that you believe is
7418 incorrect. For example, ``It gets a fatal signal.''
7420 Of course, if the bug is that @command{@value{AS}} gets a fatal signal, then we
7421 will certainly notice it. But if the bug is incorrect output, we might not
7422 notice unless it is glaringly wrong. You might as well not give us a chance to
7425 Even if the problem you experience is a fatal signal, you should still say so
7426 explicitly. Suppose something strange is going on, such as, your copy of
7427 @command{@value{AS}} is out of sync, or you have encountered a bug in the C
7428 library on your system. (This has happened!) Your copy might crash and ours
7429 would not. If you told us to expect a crash, then when ours fails to crash, we
7430 would know that the bug was not happening for us. If you had not told us to
7431 expect a crash, then we would not be able to draw any conclusion from our
7435 If you wish to suggest changes to the @command{@value{AS}} source, send us context
7436 diffs, as generated by @code{diff} with the @samp{-u}, @samp{-c}, or @samp{-p}
7437 option. Always send diffs from the old file to the new file. If you even
7438 discuss something in the @command{@value{AS}} source, refer to it by context, not
7441 The line numbers in our development sources will not match those in your
7442 sources. Your line numbers would convey no useful information to us.
7445 Here are some things that are not necessary:
7449 A description of the envelope of the bug.
7451 Often people who encounter a bug spend a lot of time investigating
7452 which changes to the input file will make the bug go away and which
7453 changes will not affect it.
7455 This is often time consuming and not very useful, because the way we
7456 will find the bug is by running a single example under the debugger
7457 with breakpoints, not by pure deduction from a series of examples.
7458 We recommend that you save your time for something else.
7460 Of course, if you can find a simpler example to report @emph{instead}
7461 of the original one, that is a convenience for us. Errors in the
7462 output will be easier to spot, running under the debugger will take
7463 less time, and so on.
7465 However, simplification is not vital; if you do not want to do this,
7466 report the bug anyway and send us the entire test case you used.
7469 A patch for the bug.
7471 A patch for the bug does help us if it is a good one. But do not omit
7472 the necessary information, such as the test case, on the assumption that
7473 a patch is all we need. We might see problems with your patch and decide
7474 to fix the problem another way, or we might not understand it at all.
7476 Sometimes with a program as complicated as @command{@value{AS}} it is very hard to
7477 construct an example that will make the program follow a certain path through
7478 the code. If you do not send us the example, we will not be able to construct
7479 one, so we will not be able to verify that the bug is fixed.
7481 And if we cannot understand what bug you are trying to fix, or why your
7482 patch should be an improvement, we will not install it. A test case will
7483 help us to understand.
7486 A guess about what the bug is or what it depends on.
7488 Such guesses are usually wrong. Even we cannot guess right about such
7489 things without first using the debugger to find the facts.
7492 @node Acknowledgements
7493 @chapter Acknowledgements
7495 If you have contributed to GAS and your name isn't listed here,
7496 it is not meant as a slight. We just don't know about it. Send mail to the
7497 maintainer, and we'll correct the situation. Currently
7499 the maintainer is Ken Raeburn (email address @code{raeburn@@cygnus.com}).
7501 Dean Elsner wrote the original @sc{gnu} assembler for the VAX.@footnote{Any
7504 Jay Fenlason maintained GAS for a while, adding support for GDB-specific debug
7505 information and the 68k series machines, most of the preprocessing pass, and
7506 extensive changes in @file{messages.c}, @file{input-file.c}, @file{write.c}.
7508 K. Richard Pixley maintained GAS for a while, adding various enhancements and
7509 many bug fixes, including merging support for several processors, breaking GAS
7510 up to handle multiple object file format back ends (including heavy rewrite,
7511 testing, an integration of the coff and b.out back ends), adding configuration
7512 including heavy testing and verification of cross assemblers and file splits
7513 and renaming, converted GAS to strictly ANSI C including full prototypes, added
7514 support for m680[34]0 and cpu32, did considerable work on i960 including a COFF
7515 port (including considerable amounts of reverse engineering), a SPARC opcode
7516 file rewrite, DECstation, rs6000, and hp300hpux host ports, updated ``know''
7517 assertions and made them work, much other reorganization, cleanup, and lint.
7519 Ken Raeburn wrote the high-level BFD interface code to replace most of the code
7520 in format-specific I/O modules.
7522 The original VMS support was contributed by David L. Kashtan. Eric Youngdale
7523 has done much work with it since.
7525 The Intel 80386 machine description was written by Eliot Dresselhaus.
7527 Minh Tran-Le at IntelliCorp contributed some AIX 386 support.
7529 The Motorola 88k machine description was contributed by Devon Bowen of Buffalo
7530 University and Torbjorn Granlund of the Swedish Institute of Computer Science.
7532 Keith Knowles at the Open Software Foundation wrote the original MIPS back end
7533 (@file{tc-mips.c}, @file{tc-mips.h}), and contributed Rose format support
7534 (which hasn't been merged in yet). Ralph Campbell worked with the MIPS code to
7535 support a.out format.
7537 Support for the Zilog Z8k and Renesas H8/300 processors (tc-z8k,
7538 tc-h8300), and IEEE 695 object file format (obj-ieee), was written by
7539 Steve Chamberlain of Cygnus Support. Steve also modified the COFF back end to
7540 use BFD for some low-level operations, for use with the H8/300 and AMD 29k
7543 John Gilmore built the AMD 29000 support, added @code{.include} support, and
7544 simplified the configuration of which versions accept which directives. He
7545 updated the 68k machine description so that Motorola's opcodes always produced
7546 fixed-size instructions (e.g., @code{jsr}), while synthetic instructions
7547 remained shrinkable (@code{jbsr}). John fixed many bugs, including true tested
7548 cross-compilation support, and one bug in relaxation that took a week and
7549 required the proverbial one-bit fix.
7551 Ian Lance Taylor of Cygnus Support merged the Motorola and MIT syntax for the
7552 68k, completed support for some COFF targets (68k, i386 SVR3, and SCO Unix),
7553 added support for MIPS ECOFF and ELF targets, wrote the initial RS/6000 and
7554 PowerPC assembler, and made a few other minor patches.
7556 Steve Chamberlain made GAS able to generate listings.
7558 Hewlett-Packard contributed support for the HP9000/300.
7560 Jeff Law wrote GAS and BFD support for the native HPPA object format (SOM)
7561 along with a fairly extensive HPPA testsuite (for both SOM and ELF object
7562 formats). This work was supported by both the Center for Software Science at
7563 the University of Utah and Cygnus Support.
7565 Support for ELF format files has been worked on by Mark Eichin of Cygnus
7566 Support (original, incomplete implementation for SPARC), Pete Hoogenboom and
7567 Jeff Law at the University of Utah (HPPA mainly), Michael Meissner of the Open
7568 Software Foundation (i386 mainly), and Ken Raeburn of Cygnus Support (sparc,
7569 and some initial 64-bit support).
7571 Linas Vepstas added GAS support for the ESA/390 ``IBM 370'' architecture.
7573 Richard Henderson rewrote the Alpha assembler. Klaus Kaempf wrote GAS and BFD
7574 support for openVMS/Alpha.
7576 Timothy Wall, Michael Hayes, and Greg Smart contributed to the various tic*
7579 David Heine, Sterling Augustine, Bob Wilson and John Ruttenberg from Tensilica,
7580 Inc.@: added support for Xtensa processors.
7582 Several engineers at Cygnus Support have also provided many small bug fixes and
7583 configuration enhancements.
7585 Jon Beniston added support for the Lattice Mico32 architecture.
7587 Many others have contributed large or small bugfixes and enhancements. If
7588 you have contributed significant work and are not mentioned on this list, and
7589 want to be, let us know. Some of the history has been lost; we are not
7590 intentionally leaving anyone out.
7592 @node GNU Free Documentation License
7593 @appendix GNU Free Documentation License
7597 @unnumbered AS Index