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. Symbols are
2489 delimited by characters not in that set, or by the beginning of a file
2490 (since the source program must end with a newline, the end of a file is
2491 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 Each symbol has exactly one name. Each name in an assembly language program
3418 refers to exactly one symbol. You may use that symbol name any number of times
3421 @subheading Local Symbol Names
3423 @cindex local symbol names
3424 @cindex symbol names, local
3425 A local symbol is any symbol beginning with certain local label prefixes.
3426 By default, the local label prefix is @samp{.L} for ELF systems or
3427 @samp{L} for traditional a.out systems, but each target may have its own
3428 set of local label prefixes.
3430 On the HPPA local symbols begin with @samp{L$}.
3433 Local symbols are defined and used within the assembler, but they are
3434 normally not saved in object files. Thus, they are not visible when debugging.
3435 You may use the @samp{-L} option (@pxref{L, ,Include Local Symbols:
3436 @option{-L}}) to retain the local symbols in the object files.
3438 @subheading Local Labels
3440 @cindex local labels
3441 @cindex temporary symbol names
3442 @cindex symbol names, temporary
3443 Local labels help compilers and programmers use names temporarily.
3444 They create symbols which are guaranteed to be unique over the entire scope of
3445 the input source code and which can be referred to by a simple notation.
3446 To define a local label, write a label of the form @samp{@b{N}:} (where @b{N}
3447 represents any positive integer). To refer to the most recent previous
3448 definition of that label write @samp{@b{N}b}, using the same number as when
3449 you defined the label. To refer to the next definition of a local label, write
3450 @samp{@b{N}f}---the @samp{b} stands for ``backwards'' and the @samp{f} stands
3453 There is no restriction on how you can use these labels, and you can reuse them
3454 too. So that it is possible to repeatedly define the same local label (using
3455 the same number @samp{@b{N}}), although you can only refer to the most recently
3456 defined local label of that number (for a backwards reference) or the next
3457 definition of a specific local label for a forward reference. It is also worth
3458 noting that the first 10 local labels (@samp{@b{0:}}@dots{}@samp{@b{9:}}) are
3459 implemented in a slightly more efficient manner than the others.
3470 Which is the equivalent of:
3473 label_1: branch label_3
3474 label_2: branch label_1
3475 label_3: branch label_4
3476 label_4: branch label_3
3479 Local label names are only a notational device. They are immediately
3480 transformed into more conventional symbol names before the assembler uses them.
3481 The symbol names are stored in the symbol table, appear in error messages, and
3482 are optionally emitted to the object file. The names are constructed using
3486 @item @emph{local label prefix}
3487 All local symbols begin with the system-specific local label prefix.
3488 Normally both @command{@value{AS}} and @code{@value{LD}} forget symbols
3489 that start with the local label prefix. These labels are
3490 used for symbols you are never intended to see. If you use the
3491 @samp{-L} option then @command{@value{AS}} retains these symbols in the
3492 object file. If you also instruct @code{@value{LD}} to retain these symbols,
3493 you may use them in debugging.
3496 This is the number that was used in the local label definition. So if the
3497 label is written @samp{55:} then the number is @samp{55}.
3500 This unusual character is included so you do not accidentally invent a symbol
3501 of the same name. The character has ASCII value of @samp{\002} (control-B).
3503 @item @emph{ordinal number}
3504 This is a serial number to keep the labels distinct. The first definition of
3505 @samp{0:} gets the number @samp{1}. The 15th definition of @samp{0:} gets the
3506 number @samp{15}, and so on. Likewise the first definition of @samp{1:} gets
3507 the number @samp{1} and its 15th definition gets @samp{15} as well.
3510 So for example, the first @code{1:} may be named @code{.L1@kbd{C-B}1}, and
3511 the 44th @code{3:} may be named @code{.L3@kbd{C-B}44}.
3513 @subheading Dollar Local Labels
3514 @cindex dollar local symbols
3516 @code{@value{AS}} also supports an even more local form of local labels called
3517 dollar labels. These labels go out of scope (i.e., they become undefined) as
3518 soon as a non-local label is defined. Thus they remain valid for only a small
3519 region of the input source code. Normal local labels, by contrast, remain in
3520 scope for the entire file, or until they are redefined by another occurrence of
3521 the same local label.
3523 Dollar labels are defined in exactly the same way as ordinary local labels,
3524 except that they have a dollar sign suffix to their numeric value, e.g.,
3527 They can also be distinguished from ordinary local labels by their transformed
3528 names which use ASCII character @samp{\001} (control-A) as the magic character
3529 to distinguish them from ordinary labels. For example, the fifth definition of
3530 @samp{6$} may be named @samp{.L6@kbd{C-A}5}.
3533 @section The Special Dot Symbol
3535 @cindex dot (symbol)
3536 @cindex @code{.} (symbol)
3537 @cindex current address
3538 @cindex location counter
3539 The special symbol @samp{.} refers to the current address that
3540 @command{@value{AS}} is assembling into. Thus, the expression @samp{melvin:
3541 .long .} defines @code{melvin} to contain its own address.
3542 Assigning a value to @code{.} is treated the same as a @code{.org}
3544 @ifclear no-space-dir
3545 Thus, the expression @samp{.=.+4} is the same as saying
3549 @node Symbol Attributes
3550 @section Symbol Attributes
3552 @cindex symbol attributes
3553 @cindex attributes, symbol
3554 Every symbol has, as well as its name, the attributes ``Value'' and
3555 ``Type''. Depending on output format, symbols can also have auxiliary
3558 The detailed definitions are in @file{a.out.h}.
3561 If you use a symbol without defining it, @command{@value{AS}} assumes zero for
3562 all these attributes, and probably won't warn you. This makes the
3563 symbol an externally defined symbol, which is generally what you
3567 * Symbol Value:: Value
3568 * Symbol Type:: Type
3571 * a.out Symbols:: Symbol Attributes: @code{a.out}
3575 * a.out Symbols:: Symbol Attributes: @code{a.out}
3578 * a.out Symbols:: Symbol Attributes: @code{a.out}, @code{b.out}
3583 * COFF Symbols:: Symbol Attributes for COFF
3586 * SOM Symbols:: Symbol Attributes for SOM
3593 @cindex value of a symbol
3594 @cindex symbol value
3595 The value of a symbol is (usually) 32 bits. For a symbol which labels a
3596 location in the text, data, bss or absolute sections the value is the
3597 number of addresses from the start of that section to the label.
3598 Naturally for text, data and bss sections the value of a symbol changes
3599 as @code{@value{LD}} changes section base addresses during linking. Absolute
3600 symbols' values do not change during linking: that is why they are
3603 The value of an undefined symbol is treated in a special way. If it is
3604 0 then the symbol is not defined in this assembler source file, and
3605 @code{@value{LD}} tries to determine its value from other files linked into the
3606 same program. You make this kind of symbol simply by mentioning a symbol
3607 name without defining it. A non-zero value represents a @code{.comm}
3608 common declaration. The value is how much common storage to reserve, in
3609 bytes (addresses). The symbol refers to the first address of the
3615 @cindex type of a symbol
3617 The type attribute of a symbol contains relocation (section)
3618 information, any flag settings indicating that a symbol is external, and
3619 (optionally), other information for linkers and debuggers. The exact
3620 format depends on the object-code output format in use.
3625 @c The following avoids a "widow" subsection title. @group would be
3626 @c better if it were available outside examples.
3629 @subsection Symbol Attributes: @code{a.out}, @code{b.out}
3631 @cindex @code{b.out} symbol attributes
3632 @cindex symbol attributes, @code{b.out}
3633 These symbol attributes appear only when @command{@value{AS}} is configured for
3634 one of the Berkeley-descended object output formats---@code{a.out} or
3640 @subsection Symbol Attributes: @code{a.out}
3642 @cindex @code{a.out} symbol attributes
3643 @cindex symbol attributes, @code{a.out}
3649 @subsection Symbol Attributes: @code{a.out}
3651 @cindex @code{a.out} symbol attributes
3652 @cindex symbol attributes, @code{a.out}
3656 * Symbol Desc:: Descriptor
3657 * Symbol Other:: Other
3661 @subsubsection Descriptor
3663 @cindex descriptor, of @code{a.out} symbol
3664 This is an arbitrary 16-bit value. You may establish a symbol's
3665 descriptor value by using a @code{.desc} statement
3666 (@pxref{Desc,,@code{.desc}}). A descriptor value means nothing to
3667 @command{@value{AS}}.
3670 @subsubsection Other
3672 @cindex other attribute, of @code{a.out} symbol
3673 This is an arbitrary 8-bit value. It means nothing to @command{@value{AS}}.
3678 @subsection Symbol Attributes for COFF
3680 @cindex COFF symbol attributes
3681 @cindex symbol attributes, COFF
3683 The COFF format supports a multitude of auxiliary symbol attributes;
3684 like the primary symbol attributes, they are set between @code{.def} and
3685 @code{.endef} directives.
3687 @subsubsection Primary Attributes
3689 @cindex primary attributes, COFF symbols
3690 The symbol name is set with @code{.def}; the value and type,
3691 respectively, with @code{.val} and @code{.type}.
3693 @subsubsection Auxiliary Attributes
3695 @cindex auxiliary attributes, COFF symbols
3696 The @command{@value{AS}} directives @code{.dim}, @code{.line}, @code{.scl},
3697 @code{.size}, @code{.tag}, and @code{.weak} can generate auxiliary symbol
3698 table information for COFF.
3703 @subsection Symbol Attributes for SOM
3705 @cindex SOM symbol attributes
3706 @cindex symbol attributes, SOM
3708 The SOM format for the HPPA supports a multitude of symbol attributes set with
3709 the @code{.EXPORT} and @code{.IMPORT} directives.
3711 The attributes are described in @cite{HP9000 Series 800 Assembly
3712 Language Reference Manual} (HP 92432-90001) under the @code{IMPORT} and
3713 @code{EXPORT} assembler directive documentation.
3717 @chapter Expressions
3721 @cindex numeric values
3722 An @dfn{expression} specifies an address or numeric value.
3723 Whitespace may precede and/or follow an expression.
3725 The result of an expression must be an absolute number, or else an offset into
3726 a particular section. If an expression is not absolute, and there is not
3727 enough information when @command{@value{AS}} sees the expression to know its
3728 section, a second pass over the source program might be necessary to interpret
3729 the expression---but the second pass is currently not implemented.
3730 @command{@value{AS}} aborts with an error message in this situation.
3733 * Empty Exprs:: Empty Expressions
3734 * Integer Exprs:: Integer Expressions
3738 @section Empty Expressions
3740 @cindex empty expressions
3741 @cindex expressions, empty
3742 An empty expression has no value: it is just whitespace or null.
3743 Wherever an absolute expression is required, you may omit the
3744 expression, and @command{@value{AS}} assumes a value of (absolute) 0. This
3745 is compatible with other assemblers.
3748 @section Integer Expressions
3750 @cindex integer expressions
3751 @cindex expressions, integer
3752 An @dfn{integer expression} is one or more @emph{arguments} delimited
3753 by @emph{operators}.
3756 * Arguments:: Arguments
3757 * Operators:: Operators
3758 * Prefix Ops:: Prefix Operators
3759 * Infix Ops:: Infix Operators
3763 @subsection Arguments
3765 @cindex expression arguments
3766 @cindex arguments in expressions
3767 @cindex operands in expressions
3768 @cindex arithmetic operands
3769 @dfn{Arguments} are symbols, numbers or subexpressions. In other
3770 contexts arguments are sometimes called ``arithmetic operands''. In
3771 this manual, to avoid confusing them with the ``instruction operands'' of
3772 the machine language, we use the term ``argument'' to refer to parts of
3773 expressions only, reserving the word ``operand'' to refer only to machine
3774 instruction operands.
3776 Symbols are evaluated to yield @{@var{section} @var{NNN}@} where
3777 @var{section} is one of text, data, bss, absolute,
3778 or undefined. @var{NNN} is a signed, 2's complement 32 bit
3781 Numbers are usually integers.
3783 A number can be a flonum or bignum. In this case, you are warned
3784 that only the low order 32 bits are used, and @command{@value{AS}} pretends
3785 these 32 bits are an integer. You may write integer-manipulating
3786 instructions that act on exotic constants, compatible with other
3789 @cindex subexpressions
3790 Subexpressions are a left parenthesis @samp{(} followed by an integer
3791 expression, followed by a right parenthesis @samp{)}; or a prefix
3792 operator followed by an argument.
3795 @subsection Operators
3797 @cindex operators, in expressions
3798 @cindex arithmetic functions
3799 @cindex functions, in expressions
3800 @dfn{Operators} are arithmetic functions, like @code{+} or @code{%}. Prefix
3801 operators are followed by an argument. Infix operators appear
3802 between their arguments. Operators may be preceded and/or followed by
3806 @subsection Prefix Operator
3808 @cindex prefix operators
3809 @command{@value{AS}} has the following @dfn{prefix operators}. They each take
3810 one argument, which must be absolute.
3812 @c the tex/end tex stuff surrounding this small table is meant to make
3813 @c it align, on the printed page, with the similar table in the next
3814 @c section (which is inside an enumerate).
3816 \global\advance\leftskip by \itemindent
3821 @dfn{Negation}. Two's complement negation.
3823 @dfn{Complementation}. Bitwise not.
3827 \global\advance\leftskip by -\itemindent
3831 @subsection Infix Operators
3833 @cindex infix operators
3834 @cindex operators, permitted arguments
3835 @dfn{Infix operators} take two arguments, one on either side. Operators
3836 have precedence, but operations with equal precedence are performed left
3837 to right. Apart from @code{+} or @option{-}, both arguments must be
3838 absolute, and the result is absolute.
3841 @cindex operator precedence
3842 @cindex precedence of operators
3849 @dfn{Multiplication}.
3852 @dfn{Division}. Truncation is the same as the C operator @samp{/}
3858 @dfn{Shift Left}. Same as the C operator @samp{<<}.
3861 @dfn{Shift Right}. Same as the C operator @samp{>>}.
3865 Intermediate precedence
3870 @dfn{Bitwise Inclusive Or}.
3876 @dfn{Bitwise Exclusive Or}.
3879 @dfn{Bitwise Or Not}.
3886 @cindex addition, permitted arguments
3887 @cindex plus, permitted arguments
3888 @cindex arguments for addition
3890 @dfn{Addition}. If either argument is absolute, the result has the section of
3891 the other argument. You may not add together arguments from different
3894 @cindex subtraction, permitted arguments
3895 @cindex minus, permitted arguments
3896 @cindex arguments for subtraction
3898 @dfn{Subtraction}. If the right argument is absolute, the
3899 result has the section of the left argument.
3900 If both arguments are in the same section, the result is absolute.
3901 You may not subtract arguments from different sections.
3902 @c FIXME is there still something useful to say about undefined - undefined ?
3904 @cindex comparison expressions
3905 @cindex expressions, comparison
3910 @dfn{Is Not Equal To}
3914 @dfn{Is Greater Than}
3916 @dfn{Is Greater Than Or Equal To}
3918 @dfn{Is Less Than Or Equal To}
3920 The comparison operators can be used as infix operators. A true results has a
3921 value of -1 whereas a false result has a value of 0. Note, these operators
3922 perform signed comparisons.
3925 @item Lowest Precedence
3934 These two logical operations can be used to combine the results of sub
3935 expressions. Note, unlike the comparison operators a true result returns a
3936 value of 1 but a false results does still return 0. Also note that the logical
3937 or operator has a slightly lower precedence than logical and.
3942 In short, it's only meaningful to add or subtract the @emph{offsets} in an
3943 address; you can only have a defined section in one of the two arguments.
3946 @chapter Assembler Directives
3948 @cindex directives, machine independent
3949 @cindex pseudo-ops, machine independent
3950 @cindex machine independent directives
3951 All assembler directives have names that begin with a period (@samp{.}).
3952 The rest of the name is letters, usually in lower case.
3954 This chapter discusses directives that are available regardless of the
3955 target machine configuration for the @sc{gnu} assembler.
3957 Some machine configurations provide additional directives.
3958 @xref{Machine Dependencies}.
3961 @ifset machine-directives
3962 @xref{Machine Dependencies}, for additional directives.
3967 * Abort:: @code{.abort}
3969 * ABORT (COFF):: @code{.ABORT}
3972 * Align:: @code{.align @var{abs-expr} , @var{abs-expr}}
3973 * Altmacro:: @code{.altmacro}
3974 * Ascii:: @code{.ascii "@var{string}"}@dots{}
3975 * Asciz:: @code{.asciz "@var{string}"}@dots{}
3976 * Balign:: @code{.balign @var{abs-expr} , @var{abs-expr}}
3977 * Bundle directives:: @code{.bundle_align_mode @var{abs-expr}}, @code{.bundle_lock}, @code{.bundle_unlock}
3978 * Byte:: @code{.byte @var{expressions}}
3979 * CFI directives:: @code{.cfi_startproc [simple]}, @code{.cfi_endproc}, etc.
3980 * Comm:: @code{.comm @var{symbol} , @var{length} }
3981 * Data:: @code{.data @var{subsection}}
3983 * Def:: @code{.def @var{name}}
3986 * Desc:: @code{.desc @var{symbol}, @var{abs-expression}}
3992 * Double:: @code{.double @var{flonums}}
3993 * Eject:: @code{.eject}
3994 * Else:: @code{.else}
3995 * Elseif:: @code{.elseif}
3998 * Endef:: @code{.endef}
4001 * Endfunc:: @code{.endfunc}
4002 * Endif:: @code{.endif}
4003 * Equ:: @code{.equ @var{symbol}, @var{expression}}
4004 * Equiv:: @code{.equiv @var{symbol}, @var{expression}}
4005 * Eqv:: @code{.eqv @var{symbol}, @var{expression}}
4007 * Error:: @code{.error @var{string}}
4008 * Exitm:: @code{.exitm}
4009 * Extern:: @code{.extern}
4010 * Fail:: @code{.fail}
4011 * File:: @code{.file}
4012 * Fill:: @code{.fill @var{repeat} , @var{size} , @var{value}}
4013 * Float:: @code{.float @var{flonums}}
4014 * Func:: @code{.func}
4015 * Global:: @code{.global @var{symbol}}, @code{.globl @var{symbol}}
4017 * Gnu_attribute:: @code{.gnu_attribute @var{tag},@var{value}}
4018 * Hidden:: @code{.hidden @var{names}}
4021 * hword:: @code{.hword @var{expressions}}
4022 * Ident:: @code{.ident}
4023 * If:: @code{.if @var{absolute expression}}
4024 * Incbin:: @code{.incbin "@var{file}"[,@var{skip}[,@var{count}]]}
4025 * Include:: @code{.include "@var{file}"}
4026 * Int:: @code{.int @var{expressions}}
4028 * Internal:: @code{.internal @var{names}}
4031 * Irp:: @code{.irp @var{symbol},@var{values}}@dots{}
4032 * Irpc:: @code{.irpc @var{symbol},@var{values}}@dots{}
4033 * Lcomm:: @code{.lcomm @var{symbol} , @var{length}}
4034 * Lflags:: @code{.lflags}
4035 @ifclear no-line-dir
4036 * Line:: @code{.line @var{line-number}}
4039 * Linkonce:: @code{.linkonce [@var{type}]}
4040 * List:: @code{.list}
4041 * Ln:: @code{.ln @var{line-number}}
4042 * Loc:: @code{.loc @var{fileno} @var{lineno}}
4043 * Loc_mark_labels:: @code{.loc_mark_labels @var{enable}}
4045 * Local:: @code{.local @var{names}}
4048 * Long:: @code{.long @var{expressions}}
4050 * Lsym:: @code{.lsym @var{symbol}, @var{expression}}
4053 * Macro:: @code{.macro @var{name} @var{args}}@dots{}
4054 * MRI:: @code{.mri @var{val}}
4055 * Noaltmacro:: @code{.noaltmacro}
4056 * Nolist:: @code{.nolist}
4057 * Octa:: @code{.octa @var{bignums}}
4058 * Offset:: @code{.offset @var{loc}}
4059 * Org:: @code{.org @var{new-lc}, @var{fill}}
4060 * P2align:: @code{.p2align @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
4062 * PopSection:: @code{.popsection}
4063 * Previous:: @code{.previous}
4066 * Print:: @code{.print @var{string}}
4068 * Protected:: @code{.protected @var{names}}
4071 * Psize:: @code{.psize @var{lines}, @var{columns}}
4072 * Purgem:: @code{.purgem @var{name}}
4074 * PushSection:: @code{.pushsection @var{name}}
4077 * Quad:: @code{.quad @var{bignums}}
4078 * Reloc:: @code{.reloc @var{offset}, @var{reloc_name}[, @var{expression}]}
4079 * Rept:: @code{.rept @var{count}}
4080 * Sbttl:: @code{.sbttl "@var{subheading}"}
4082 * Scl:: @code{.scl @var{class}}
4085 * Section:: @code{.section @var{name}[, @var{flags}]}
4088 * Set:: @code{.set @var{symbol}, @var{expression}}
4089 * Short:: @code{.short @var{expressions}}
4090 * Single:: @code{.single @var{flonums}}
4092 * Size:: @code{.size [@var{name} , @var{expression}]}
4094 @ifclear no-space-dir
4095 * Skip:: @code{.skip @var{size} , @var{fill}}
4098 * Sleb128:: @code{.sleb128 @var{expressions}}
4099 @ifclear no-space-dir
4100 * Space:: @code{.space @var{size} , @var{fill}}
4103 * Stab:: @code{.stabd, .stabn, .stabs}
4106 * String:: @code{.string "@var{str}"}, @code{.string8 "@var{str}"}, @code{.string16 "@var{str}"}, @code{.string32 "@var{str}"}, @code{.string64 "@var{str}"}
4107 * Struct:: @code{.struct @var{expression}}
4109 * SubSection:: @code{.subsection}
4110 * Symver:: @code{.symver @var{name},@var{name2@@nodename}}
4114 * Tag:: @code{.tag @var{structname}}
4117 * Text:: @code{.text @var{subsection}}
4118 * Title:: @code{.title "@var{heading}"}
4120 * Type:: @code{.type <@var{int} | @var{name} , @var{type description}>}
4123 * Uleb128:: @code{.uleb128 @var{expressions}}
4125 * Val:: @code{.val @var{addr}}
4129 * Version:: @code{.version "@var{string}"}
4130 * VTableEntry:: @code{.vtable_entry @var{table}, @var{offset}}
4131 * VTableInherit:: @code{.vtable_inherit @var{child}, @var{parent}}
4134 * Warning:: @code{.warning @var{string}}
4135 * Weak:: @code{.weak @var{names}}
4136 * Weakref:: @code{.weakref @var{alias}, @var{symbol}}
4137 * Word:: @code{.word @var{expressions}}
4138 * Deprecated:: Deprecated Directives
4142 @section @code{.abort}
4144 @cindex @code{abort} directive
4145 @cindex stopping the assembly
4146 This directive stops the assembly immediately. It is for
4147 compatibility with other assemblers. The original idea was that the
4148 assembly language source would be piped into the assembler. If the sender
4149 of the source quit, it could use this directive tells @command{@value{AS}} to
4150 quit also. One day @code{.abort} will not be supported.
4154 @section @code{.ABORT} (COFF)
4156 @cindex @code{ABORT} directive
4157 When producing COFF output, @command{@value{AS}} accepts this directive as a
4158 synonym for @samp{.abort}.
4161 When producing @code{b.out} output, @command{@value{AS}} accepts this directive,
4167 @section @code{.align @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
4169 @cindex padding the location counter
4170 @cindex @code{align} directive
4171 Pad the location counter (in the current subsection) to a particular storage
4172 boundary. The first expression (which must be absolute) is the alignment
4173 required, as described below.
4175 The second expression (also absolute) gives the fill value to be stored in the
4176 padding bytes. It (and the comma) may be omitted. If it is omitted, the
4177 padding bytes are normally zero. However, on some systems, if the section is
4178 marked as containing code and the fill value is omitted, the space is filled
4179 with no-op instructions.
4181 The third expression is also absolute, and is also optional. If it is present,
4182 it is the maximum number of bytes that should be skipped by this alignment
4183 directive. If doing the alignment would require skipping more bytes than the
4184 specified maximum, then the alignment is not done at all. You can omit the
4185 fill value (the second argument) entirely by simply using two commas after the
4186 required alignment; this can be useful if you want the alignment to be filled
4187 with no-op instructions when appropriate.
4189 The way the required alignment is specified varies from system to system.
4190 For the arc, hppa, i386 using ELF, i860, iq2000, m68k, or32,
4191 s390, sparc, tic4x, tic80 and xtensa, the first expression is the
4192 alignment request in bytes. For example @samp{.align 8} advances
4193 the location counter until it is a multiple of 8. If the location counter
4194 is already a multiple of 8, no change is needed. For the tic54x, the
4195 first expression is the alignment request in words.
4197 For other systems, including ppc, i386 using a.out format, arm and
4198 strongarm, it is the
4199 number of low-order zero bits the location counter must have after
4200 advancement. For example @samp{.align 3} advances the location
4201 counter until it a multiple of 8. If the location counter is already a
4202 multiple of 8, no change is needed.
4204 This inconsistency is due to the different behaviors of the various
4205 native assemblers for these systems which GAS must emulate.
4206 GAS also provides @code{.balign} and @code{.p2align} directives,
4207 described later, which have a consistent behavior across all
4208 architectures (but are specific to GAS).
4211 @section @code{.altmacro}
4212 Enable alternate macro mode, enabling:
4215 @item LOCAL @var{name} [ , @dots{} ]
4216 One additional directive, @code{LOCAL}, is available. It is used to
4217 generate a string replacement for each of the @var{name} arguments, and
4218 replace any instances of @var{name} in each macro expansion. The
4219 replacement string is unique in the assembly, and different for each
4220 separate macro expansion. @code{LOCAL} allows you to write macros that
4221 define symbols, without fear of conflict between separate macro expansions.
4223 @item String delimiters
4224 You can write strings delimited in these other ways besides
4225 @code{"@var{string}"}:
4228 @item '@var{string}'
4229 You can delimit strings with single-quote characters.
4231 @item <@var{string}>
4232 You can delimit strings with matching angle brackets.
4235 @item single-character string escape
4236 To include any single character literally in a string (even if the
4237 character would otherwise have some special meaning), you can prefix the
4238 character with @samp{!} (an exclamation mark). For example, you can
4239 write @samp{<4.3 !> 5.4!!>} to get the literal text @samp{4.3 > 5.4!}.
4241 @item Expression results as strings
4242 You can write @samp{%@var{expr}} to evaluate the expression @var{expr}
4243 and use the result as a string.
4247 @section @code{.ascii "@var{string}"}@dots{}
4249 @cindex @code{ascii} directive
4250 @cindex string literals
4251 @code{.ascii} expects zero or more string literals (@pxref{Strings})
4252 separated by commas. It assembles each string (with no automatic
4253 trailing zero byte) into consecutive addresses.
4256 @section @code{.asciz "@var{string}"}@dots{}
4258 @cindex @code{asciz} directive
4259 @cindex zero-terminated strings
4260 @cindex null-terminated strings
4261 @code{.asciz} is just like @code{.ascii}, but each string is followed by
4262 a zero byte. The ``z'' in @samp{.asciz} stands for ``zero''.
4265 @section @code{.balign[wl] @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
4267 @cindex padding the location counter given number of bytes
4268 @cindex @code{balign} directive
4269 Pad the location counter (in the current subsection) to a particular
4270 storage boundary. The first expression (which must be absolute) is the
4271 alignment request in bytes. For example @samp{.balign 8} advances
4272 the location counter until it is a multiple of 8. If the location counter
4273 is already a multiple of 8, no change is needed.
4275 The second expression (also absolute) gives the fill value to be stored in the
4276 padding bytes. It (and the comma) may be omitted. If it is omitted, the
4277 padding bytes are normally zero. However, on some systems, if the section is
4278 marked as containing code and the fill value is omitted, the space is filled
4279 with no-op instructions.
4281 The third expression is also absolute, and is also optional. If it is present,
4282 it is the maximum number of bytes that should be skipped by this alignment
4283 directive. If doing the alignment would require skipping more bytes than the
4284 specified maximum, then the alignment is not done at all. You can omit the
4285 fill value (the second argument) entirely by simply using two commas after the
4286 required alignment; this can be useful if you want the alignment to be filled
4287 with no-op instructions when appropriate.
4289 @cindex @code{balignw} directive
4290 @cindex @code{balignl} directive
4291 The @code{.balignw} and @code{.balignl} directives are variants of the
4292 @code{.balign} directive. The @code{.balignw} directive treats the fill
4293 pattern as a two byte word value. The @code{.balignl} directives treats the
4294 fill pattern as a four byte longword value. For example, @code{.balignw
4295 4,0x368d} will align to a multiple of 4. If it skips two bytes, they will be
4296 filled in with the value 0x368d (the exact placement of the bytes depends upon
4297 the endianness of the processor). If it skips 1 or 3 bytes, the fill value is
4300 @node Bundle directives
4301 @section @code{.bundle_align_mode @var{abs-expr}}
4302 @cindex @code{bundle_align_mode} directive
4304 @cindex instruction bundle
4305 @cindex aligned instruction bundle
4306 @code{.bundle_align_mode} enables or disables @dfn{aligned instruction
4307 bundle} mode. In this mode, sequences of adjacent instructions are grouped
4308 into fixed-sized @dfn{bundles}. If the argument is zero, this mode is
4309 disabled (which is the default state). If the argument it not zero, it
4310 gives the size of an instruction bundle as a power of two (as for the
4311 @code{.p2align} directive, @pxref{P2align}).
4313 For some targets, it's an ABI requirement that no instruction may span a
4314 certain aligned boundary. A @dfn{bundle} is simply a sequence of
4315 instructions that starts on an aligned boundary. For example, if
4316 @var{abs-expr} is @code{5} then the bundle size is 32, so each aligned
4317 chunk of 32 bytes is a bundle. When aligned instruction bundle mode is in
4318 effect, no single instruction may span a boundary between bundles. If an
4319 instruction would start too close to the end of a bundle for the length of
4320 that particular instruction to fit within the bundle, then the space at the
4321 end of that bundle is filled with no-op instructions so the instruction
4322 starts in the next bundle. As a corollary, it's an error if any single
4323 instruction's encoding is longer than the bundle size.
4325 @section @code{.bundle_lock} and @code{.bundle_unlock}
4326 @cindex @code{bundle_lock} directive
4327 @cindex @code{bundle_unlock} directive
4328 The @code{.bundle_lock} and directive @code{.bundle_unlock} directives
4329 allow explicit control over instruction bundle padding. These directives
4330 are only valid when @code{.bundle_align_mode} has been used to enable
4331 aligned instruction bundle mode. It's an error if they appear when
4332 @code{.bundle_align_mode} has not been used at all, or when the last
4333 directive was @w{@code{.bundle_align_mode 0}}.
4335 @cindex bundle-locked
4336 For some targets, it's an ABI requirement that certain instructions may
4337 appear only as part of specified permissible sequences of multiple
4338 instructions, all within the same bundle. A pair of @code{.bundle_lock}
4339 and @code{.bundle_unlock} directives define a @dfn{bundle-locked}
4340 instruction sequence. For purposes of aligned instruction bundle mode, a
4341 sequence starting with @code{.bundle_lock} and ending with
4342 @code{.bundle_unlock} is treated as a single instruction. That is, the
4343 entire sequence must fit into a single bundle and may not span a bundle
4344 boundary. If necessary, no-op instructions will be inserted before the
4345 first instruction of the sequence so that the whole sequence starts on an
4346 aligned bundle boundary. It's an error if the sequence is longer than the
4349 Bundle-locked sequences do not nest. It's an error if two
4350 @code{.bundle_lock} directives appear without an intervening
4351 @code{.bundle_unlock} directive.
4354 @section @code{.byte @var{expressions}}
4356 @cindex @code{byte} directive
4357 @cindex integers, one byte
4358 @code{.byte} expects zero or more expressions, separated by commas.
4359 Each expression is assembled into the next byte.
4361 @node CFI directives
4362 @section @code{.cfi_sections @var{section_list}}
4363 @cindex @code{cfi_sections} directive
4364 @code{.cfi_sections} may be used to specify whether CFI directives
4365 should emit @code{.eh_frame} section and/or @code{.debug_frame} section.
4366 If @var{section_list} is @code{.eh_frame}, @code{.eh_frame} is emitted,
4367 if @var{section_list} is @code{.debug_frame}, @code{.debug_frame} is emitted.
4368 To emit both use @code{.eh_frame, .debug_frame}. The default if this
4369 directive is not used is @code{.cfi_sections .eh_frame}.
4371 @section @code{.cfi_startproc [simple]}
4372 @cindex @code{cfi_startproc} directive
4373 @code{.cfi_startproc} is used at the beginning of each function that
4374 should have an entry in @code{.eh_frame}. It initializes some internal
4375 data structures. Don't forget to close the function by
4376 @code{.cfi_endproc}.
4378 Unless @code{.cfi_startproc} is used along with parameter @code{simple}
4379 it also emits some architecture dependent initial CFI instructions.
4381 @section @code{.cfi_endproc}
4382 @cindex @code{cfi_endproc} directive
4383 @code{.cfi_endproc} is used at the end of a function where it closes its
4384 unwind entry previously opened by
4385 @code{.cfi_startproc}, and emits it to @code{.eh_frame}.
4387 @section @code{.cfi_personality @var{encoding} [, @var{exp}]}
4388 @code{.cfi_personality} defines personality routine and its encoding.
4389 @var{encoding} must be a constant determining how the personality
4390 should be encoded. If it is 255 (@code{DW_EH_PE_omit}), second
4391 argument is not present, otherwise second argument should be
4392 a constant or a symbol name. When using indirect encodings,
4393 the symbol provided should be the location where personality
4394 can be loaded from, not the personality routine itself.
4395 The default after @code{.cfi_startproc} is @code{.cfi_personality 0xff},
4396 no personality routine.
4398 @section @code{.cfi_lsda @var{encoding} [, @var{exp}]}
4399 @code{.cfi_lsda} defines LSDA and its encoding.
4400 @var{encoding} must be a constant determining how the LSDA
4401 should be encoded. If it is 255 (@code{DW_EH_PE_omit}), second
4402 argument is not present, otherwise second argument should be a constant
4403 or a symbol name. The default after @code{.cfi_startproc} is @code{.cfi_lsda 0xff},
4406 @section @code{.cfi_def_cfa @var{register}, @var{offset}}
4407 @code{.cfi_def_cfa} defines a rule for computing CFA as: @i{take
4408 address from @var{register} and add @var{offset} to it}.
4410 @section @code{.cfi_def_cfa_register @var{register}}
4411 @code{.cfi_def_cfa_register} modifies a rule for computing CFA. From
4412 now on @var{register} will be used instead of the old one. Offset
4415 @section @code{.cfi_def_cfa_offset @var{offset}}
4416 @code{.cfi_def_cfa_offset} modifies a rule for computing CFA. Register
4417 remains the same, but @var{offset} is new. Note that it is the
4418 absolute offset that will be added to a defined register to compute
4421 @section @code{.cfi_adjust_cfa_offset @var{offset}}
4422 Same as @code{.cfi_def_cfa_offset} but @var{offset} is a relative
4423 value that is added/substracted from the previous offset.
4425 @section @code{.cfi_offset @var{register}, @var{offset}}
4426 Previous value of @var{register} is saved at offset @var{offset} from
4429 @section @code{.cfi_rel_offset @var{register}, @var{offset}}
4430 Previous value of @var{register} is saved at offset @var{offset} from
4431 the current CFA register. This is transformed to @code{.cfi_offset}
4432 using the known displacement of the CFA register from the CFA.
4433 This is often easier to use, because the number will match the
4434 code it's annotating.
4436 @section @code{.cfi_register @var{register1}, @var{register2}}
4437 Previous value of @var{register1} is saved in register @var{register2}.
4439 @section @code{.cfi_restore @var{register}}
4440 @code{.cfi_restore} says that the rule for @var{register} is now the
4441 same as it was at the beginning of the function, after all initial
4442 instruction added by @code{.cfi_startproc} were executed.
4444 @section @code{.cfi_undefined @var{register}}
4445 From now on the previous value of @var{register} can't be restored anymore.
4447 @section @code{.cfi_same_value @var{register}}
4448 Current value of @var{register} is the same like in the previous frame,
4449 i.e. no restoration needed.
4451 @section @code{.cfi_remember_state},
4452 First save all current rules for all registers by @code{.cfi_remember_state},
4453 then totally screw them up by subsequent @code{.cfi_*} directives and when
4454 everything is hopelessly bad, use @code{.cfi_restore_state} to restore
4455 the previous saved state.
4457 @section @code{.cfi_return_column @var{register}}
4458 Change return column @var{register}, i.e. the return address is either
4459 directly in @var{register} or can be accessed by rules for @var{register}.
4461 @section @code{.cfi_signal_frame}
4462 Mark current function as signal trampoline.
4464 @section @code{.cfi_window_save}
4465 SPARC register window has been saved.
4467 @section @code{.cfi_escape} @var{expression}[, @dots{}]
4468 Allows the user to add arbitrary bytes to the unwind info. One
4469 might use this to add OS-specific CFI opcodes, or generic CFI
4470 opcodes that GAS does not yet support.
4472 @section @code{.cfi_val_encoded_addr @var{register}, @var{encoding}, @var{label}}
4473 The current value of @var{register} is @var{label}. The value of @var{label}
4474 will be encoded in the output file according to @var{encoding}; see the
4475 description of @code{.cfi_personality} for details on this encoding.
4477 The usefulness of equating a register to a fixed label is probably
4478 limited to the return address register. Here, it can be useful to
4479 mark a code segment that has only one return address which is reached
4480 by a direct branch and no copy of the return address exists in memory
4481 or another register.
4484 @section @code{.comm @var{symbol} , @var{length} }
4486 @cindex @code{comm} directive
4487 @cindex symbol, common
4488 @code{.comm} declares a common symbol named @var{symbol}. When linking, a
4489 common symbol in one object file may be merged with a defined or common symbol
4490 of the same name in another object file. If @code{@value{LD}} does not see a
4491 definition for the symbol--just one or more common symbols--then it will
4492 allocate @var{length} bytes of uninitialized memory. @var{length} must be an
4493 absolute expression. If @code{@value{LD}} sees multiple common symbols with
4494 the same name, and they do not all have the same size, it will allocate space
4495 using the largest size.
4498 When using ELF or (as a GNU extension) PE, the @code{.comm} directive takes
4499 an optional third argument. This is the desired alignment of the symbol,
4500 specified for ELF as a byte boundary (for example, an alignment of 16 means
4501 that the least significant 4 bits of the address should be zero), and for PE
4502 as a power of two (for example, an alignment of 5 means aligned to a 32-byte
4503 boundary). The alignment must be an absolute expression, and it must be a
4504 power of two. If @code{@value{LD}} allocates uninitialized memory for the
4505 common symbol, it will use the alignment when placing the symbol. If no
4506 alignment is specified, @command{@value{AS}} will set the alignment to the
4507 largest power of two less than or equal to the size of the symbol, up to a
4508 maximum of 16 on ELF, or the default section alignment of 4 on PE@footnote{This
4509 is not the same as the executable image file alignment controlled by @code{@value{LD}}'s
4510 @samp{--section-alignment} option; image file sections in PE are aligned to
4511 multiples of 4096, which is far too large an alignment for ordinary variables.
4512 It is rather the default alignment for (non-debug) sections within object
4513 (@samp{*.o}) files, which are less strictly aligned.}.
4517 The syntax for @code{.comm} differs slightly on the HPPA. The syntax is
4518 @samp{@var{symbol} .comm, @var{length}}; @var{symbol} is optional.
4522 @section @code{.data @var{subsection}}
4524 @cindex @code{data} directive
4525 @code{.data} tells @command{@value{AS}} to assemble the following statements onto the
4526 end of the data subsection numbered @var{subsection} (which is an
4527 absolute expression). If @var{subsection} is omitted, it defaults
4532 @section @code{.def @var{name}}
4534 @cindex @code{def} directive
4535 @cindex COFF symbols, debugging
4536 @cindex debugging COFF symbols
4537 Begin defining debugging information for a symbol @var{name}; the
4538 definition extends until the @code{.endef} directive is encountered.
4541 This directive is only observed when @command{@value{AS}} is configured for COFF
4542 format output; when producing @code{b.out}, @samp{.def} is recognized,
4549 @section @code{.desc @var{symbol}, @var{abs-expression}}
4551 @cindex @code{desc} directive
4552 @cindex COFF symbol descriptor
4553 @cindex symbol descriptor, COFF
4554 This directive sets the descriptor of the symbol (@pxref{Symbol Attributes})
4555 to the low 16 bits of an absolute expression.
4558 The @samp{.desc} directive is not available when @command{@value{AS}} is
4559 configured for COFF output; it is only for @code{a.out} or @code{b.out}
4560 object format. For the sake of compatibility, @command{@value{AS}} accepts
4561 it, but produces no output, when configured for COFF.
4567 @section @code{.dim}
4569 @cindex @code{dim} directive
4570 @cindex COFF auxiliary symbol information
4571 @cindex auxiliary symbol information, COFF
4572 This directive is generated by compilers to include auxiliary debugging
4573 information in the symbol table. It is only permitted inside
4574 @code{.def}/@code{.endef} pairs.
4577 @samp{.dim} is only meaningful when generating COFF format output; when
4578 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
4584 @section @code{.double @var{flonums}}
4586 @cindex @code{double} directive
4587 @cindex floating point numbers (double)
4588 @code{.double} expects zero or more flonums, separated by commas. It
4589 assembles floating point numbers.
4591 The exact kind of floating point numbers emitted depends on how
4592 @command{@value{AS}} is configured. @xref{Machine Dependencies}.
4596 On the @value{TARGET} family @samp{.double} emits 64-bit floating-point numbers
4597 in @sc{ieee} format.
4602 @section @code{.eject}
4604 @cindex @code{eject} directive
4605 @cindex new page, in listings
4606 @cindex page, in listings
4607 @cindex listing control: new page
4608 Force a page break at this point, when generating assembly listings.
4611 @section @code{.else}
4613 @cindex @code{else} directive
4614 @code{.else} is part of the @command{@value{AS}} support for conditional
4615 assembly; see @ref{If,,@code{.if}}. It marks the beginning of a section
4616 of code to be assembled if the condition for the preceding @code{.if}
4620 @section @code{.elseif}
4622 @cindex @code{elseif} directive
4623 @code{.elseif} is part of the @command{@value{AS}} support for conditional
4624 assembly; see @ref{If,,@code{.if}}. It is shorthand for beginning a new
4625 @code{.if} block that would otherwise fill the entire @code{.else} section.
4628 @section @code{.end}
4630 @cindex @code{end} directive
4631 @code{.end} marks the end of the assembly file. @command{@value{AS}} does not
4632 process anything in the file past the @code{.end} directive.
4636 @section @code{.endef}
4638 @cindex @code{endef} directive
4639 This directive flags the end of a symbol definition begun with
4643 @samp{.endef} is only meaningful when generating COFF format output; if
4644 @command{@value{AS}} is configured to generate @code{b.out}, it accepts this
4645 directive but ignores it.
4650 @section @code{.endfunc}
4651 @cindex @code{endfunc} directive
4652 @code{.endfunc} marks the end of a function specified with @code{.func}.
4655 @section @code{.endif}
4657 @cindex @code{endif} directive
4658 @code{.endif} is part of the @command{@value{AS}} support for conditional assembly;
4659 it marks the end of a block of code that is only assembled
4660 conditionally. @xref{If,,@code{.if}}.
4663 @section @code{.equ @var{symbol}, @var{expression}}
4665 @cindex @code{equ} directive
4666 @cindex assigning values to symbols
4667 @cindex symbols, assigning values to
4668 This directive sets the value of @var{symbol} to @var{expression}.
4669 It is synonymous with @samp{.set}; see @ref{Set,,@code{.set}}.
4672 The syntax for @code{equ} on the HPPA is
4673 @samp{@var{symbol} .equ @var{expression}}.
4677 The syntax for @code{equ} on the Z80 is
4678 @samp{@var{symbol} equ @var{expression}}.
4679 On the Z80 it is an eror if @var{symbol} is already defined,
4680 but the symbol is not protected from later redefinition.
4681 Compare @ref{Equiv}.
4685 @section @code{.equiv @var{symbol}, @var{expression}}
4686 @cindex @code{equiv} directive
4687 The @code{.equiv} directive is like @code{.equ} and @code{.set}, except that
4688 the assembler will signal an error if @var{symbol} is already defined. Note a
4689 symbol which has been referenced but not actually defined is considered to be
4692 Except for the contents of the error message, this is roughly equivalent to
4699 plus it protects the symbol from later redefinition.
4702 @section @code{.eqv @var{symbol}, @var{expression}}
4703 @cindex @code{eqv} directive
4704 The @code{.eqv} directive is like @code{.equiv}, but no attempt is made to
4705 evaluate the expression or any part of it immediately. Instead each time
4706 the resulting symbol is used in an expression, a snapshot of its current
4710 @section @code{.err}
4711 @cindex @code{err} directive
4712 If @command{@value{AS}} assembles a @code{.err} directive, it will print an error
4713 message and, unless the @option{-Z} option was used, it will not generate an
4714 object file. This can be used to signal an error in conditionally compiled code.
4717 @section @code{.error "@var{string}"}
4718 @cindex error directive
4720 Similarly to @code{.err}, this directive emits an error, but you can specify a
4721 string that will be emitted as the error message. If you don't specify the
4722 message, it defaults to @code{".error directive invoked in source file"}.
4723 @xref{Errors, ,Error and Warning Messages}.
4726 .error "This code has not been assembled and tested."
4730 @section @code{.exitm}
4731 Exit early from the current macro definition. @xref{Macro}.
4734 @section @code{.extern}
4736 @cindex @code{extern} directive
4737 @code{.extern} is accepted in the source program---for compatibility
4738 with other assemblers---but it is ignored. @command{@value{AS}} treats
4739 all undefined symbols as external.
4742 @section @code{.fail @var{expression}}
4744 @cindex @code{fail} directive
4745 Generates an error or a warning. If the value of the @var{expression} is 500
4746 or more, @command{@value{AS}} will print a warning message. If the value is less
4747 than 500, @command{@value{AS}} will print an error message. The message will
4748 include the value of @var{expression}. This can occasionally be useful inside
4749 complex nested macros or conditional assembly.
4752 @section @code{.file}
4753 @cindex @code{file} directive
4755 @ifclear no-file-dir
4756 There are two different versions of the @code{.file} directive. Targets
4757 that support DWARF2 line number information use the DWARF2 version of
4758 @code{.file}. Other targets use the default version.
4760 @subheading Default Version
4762 @cindex logical file name
4763 @cindex file name, logical
4764 This version of the @code{.file} directive tells @command{@value{AS}} that we
4765 are about to start a new logical file. The syntax is:
4771 @var{string} is the new file name. In general, the filename is
4772 recognized whether or not it is surrounded by quotes @samp{"}; but if you wish
4773 to specify an empty file name, you must give the quotes--@code{""}. This
4774 statement may go away in future: it is only recognized to be compatible with
4775 old @command{@value{AS}} programs.
4777 @subheading DWARF2 Version
4780 When emitting DWARF2 line number information, @code{.file} assigns filenames
4781 to the @code{.debug_line} file name table. The syntax is:
4784 .file @var{fileno} @var{filename}
4787 The @var{fileno} operand should be a unique positive integer to use as the
4788 index of the entry in the table. The @var{filename} operand is a C string
4791 The detail of filename indices is exposed to the user because the filename
4792 table is shared with the @code{.debug_info} section of the DWARF2 debugging
4793 information, and thus the user must know the exact indices that table
4797 @section @code{.fill @var{repeat} , @var{size} , @var{value}}
4799 @cindex @code{fill} directive
4800 @cindex writing patterns in memory
4801 @cindex patterns, writing in memory
4802 @var{repeat}, @var{size} and @var{value} are absolute expressions.
4803 This emits @var{repeat} copies of @var{size} bytes. @var{Repeat}
4804 may be zero or more. @var{Size} may be zero or more, but if it is
4805 more than 8, then it is deemed to have the value 8, compatible with
4806 other people's assemblers. The contents of each @var{repeat} bytes
4807 is taken from an 8-byte number. The highest order 4 bytes are
4808 zero. The lowest order 4 bytes are @var{value} rendered in the
4809 byte-order of an integer on the computer @command{@value{AS}} is assembling for.
4810 Each @var{size} bytes in a repetition is taken from the lowest order
4811 @var{size} bytes of this number. Again, this bizarre behavior is
4812 compatible with other people's assemblers.
4814 @var{size} and @var{value} are optional.
4815 If the second comma and @var{value} are absent, @var{value} is
4816 assumed zero. If the first comma and following tokens are absent,
4817 @var{size} is assumed to be 1.
4820 @section @code{.float @var{flonums}}
4822 @cindex floating point numbers (single)
4823 @cindex @code{float} directive
4824 This directive assembles zero or more flonums, separated by commas. It
4825 has the same effect as @code{.single}.
4827 The exact kind of floating point numbers emitted depends on how
4828 @command{@value{AS}} is configured.
4829 @xref{Machine Dependencies}.
4833 On the @value{TARGET} family, @code{.float} emits 32-bit floating point numbers
4834 in @sc{ieee} format.
4839 @section @code{.func @var{name}[,@var{label}]}
4840 @cindex @code{func} directive
4841 @code{.func} emits debugging information to denote function @var{name}, and
4842 is ignored unless the file is assembled with debugging enabled.
4843 Only @samp{--gstabs[+]} is currently supported.
4844 @var{label} is the entry point of the function and if omitted @var{name}
4845 prepended with the @samp{leading char} is used.
4846 @samp{leading char} is usually @code{_} or nothing, depending on the target.
4847 All functions are currently defined to have @code{void} return type.
4848 The function must be terminated with @code{.endfunc}.
4851 @section @code{.global @var{symbol}}, @code{.globl @var{symbol}}
4853 @cindex @code{global} directive
4854 @cindex symbol, making visible to linker
4855 @code{.global} makes the symbol visible to @code{@value{LD}}. If you define
4856 @var{symbol} in your partial program, its value is made available to
4857 other partial programs that are linked with it. Otherwise,
4858 @var{symbol} takes its attributes from a symbol of the same name
4859 from another file linked into the same program.
4861 Both spellings (@samp{.globl} and @samp{.global}) are accepted, for
4862 compatibility with other assemblers.
4865 On the HPPA, @code{.global} is not always enough to make it accessible to other
4866 partial programs. You may need the HPPA-only @code{.EXPORT} directive as well.
4867 @xref{HPPA Directives, ,HPPA Assembler Directives}.
4872 @section @code{.gnu_attribute @var{tag},@var{value}}
4873 Record a @sc{gnu} object attribute for this file. @xref{Object Attributes}.
4876 @section @code{.hidden @var{names}}
4878 @cindex @code{hidden} directive
4880 This is one of the ELF visibility directives. The other two are
4881 @code{.internal} (@pxref{Internal,,@code{.internal}}) and
4882 @code{.protected} (@pxref{Protected,,@code{.protected}}).
4884 This directive overrides the named symbols default visibility (which is set by
4885 their binding: local, global or weak). The directive sets the visibility to
4886 @code{hidden} which means that the symbols are not visible to other components.
4887 Such symbols are always considered to be @code{protected} as well.
4891 @section @code{.hword @var{expressions}}
4893 @cindex @code{hword} directive
4894 @cindex integers, 16-bit
4895 @cindex numbers, 16-bit
4896 @cindex sixteen bit integers
4897 This expects zero or more @var{expressions}, and emits
4898 a 16 bit number for each.
4901 This directive is a synonym for @samp{.short}; depending on the target
4902 architecture, it may also be a synonym for @samp{.word}.
4906 This directive is a synonym for @samp{.short}.
4909 This directive is a synonym for both @samp{.short} and @samp{.word}.
4914 @section @code{.ident}
4916 @cindex @code{ident} directive
4918 This directive is used by some assemblers to place tags in object files. The
4919 behavior of this directive varies depending on the target. When using the
4920 a.out object file format, @command{@value{AS}} simply accepts the directive for
4921 source-file compatibility with existing assemblers, but does not emit anything
4922 for it. When using COFF, comments are emitted to the @code{.comment} or
4923 @code{.rdata} section, depending on the target. When using ELF, comments are
4924 emitted to the @code{.comment} section.
4927 @section @code{.if @var{absolute expression}}
4929 @cindex conditional assembly
4930 @cindex @code{if} directive
4931 @code{.if} marks the beginning of a section of code which is only
4932 considered part of the source program being assembled if the argument
4933 (which must be an @var{absolute expression}) is non-zero. The end of
4934 the conditional section of code must be marked by @code{.endif}
4935 (@pxref{Endif,,@code{.endif}}); optionally, you may include code for the
4936 alternative condition, flagged by @code{.else} (@pxref{Else,,@code{.else}}).
4937 If you have several conditions to check, @code{.elseif} may be used to avoid
4938 nesting blocks if/else within each subsequent @code{.else} block.
4940 The following variants of @code{.if} are also supported:
4942 @cindex @code{ifdef} directive
4943 @item .ifdef @var{symbol}
4944 Assembles the following section of code if the specified @var{symbol}
4945 has been defined. Note a symbol which has been referenced but not yet defined
4946 is considered to be undefined.
4948 @cindex @code{ifb} directive
4949 @item .ifb @var{text}
4950 Assembles the following section of code if the operand is blank (empty).
4952 @cindex @code{ifc} directive
4953 @item .ifc @var{string1},@var{string2}
4954 Assembles the following section of code if the two strings are the same. The
4955 strings may be optionally quoted with single quotes. If they are not quoted,
4956 the first string stops at the first comma, and the second string stops at the
4957 end of the line. Strings which contain whitespace should be quoted. The
4958 string comparison is case sensitive.
4960 @cindex @code{ifeq} directive
4961 @item .ifeq @var{absolute expression}
4962 Assembles the following section of code if the argument is zero.
4964 @cindex @code{ifeqs} directive
4965 @item .ifeqs @var{string1},@var{string2}
4966 Another form of @code{.ifc}. The strings must be quoted using double quotes.
4968 @cindex @code{ifge} directive
4969 @item .ifge @var{absolute expression}
4970 Assembles the following section of code if the argument is greater than or
4973 @cindex @code{ifgt} directive
4974 @item .ifgt @var{absolute expression}
4975 Assembles the following section of code if the argument is greater than zero.
4977 @cindex @code{ifle} directive
4978 @item .ifle @var{absolute expression}
4979 Assembles the following section of code if the argument is less than or equal
4982 @cindex @code{iflt} directive
4983 @item .iflt @var{absolute expression}
4984 Assembles the following section of code if the argument is less than zero.
4986 @cindex @code{ifnb} directive
4987 @item .ifnb @var{text}
4988 Like @code{.ifb}, but the sense of the test is reversed: this assembles the
4989 following section of code if the operand is non-blank (non-empty).
4991 @cindex @code{ifnc} directive
4992 @item .ifnc @var{string1},@var{string2}.
4993 Like @code{.ifc}, but the sense of the test is reversed: this assembles the
4994 following section of code if the two strings are not the same.
4996 @cindex @code{ifndef} directive
4997 @cindex @code{ifnotdef} directive
4998 @item .ifndef @var{symbol}
4999 @itemx .ifnotdef @var{symbol}
5000 Assembles the following section of code if the specified @var{symbol}
5001 has not been defined. Both spelling variants are equivalent. Note a symbol
5002 which has been referenced but not yet defined is considered to be undefined.
5004 @cindex @code{ifne} directive
5005 @item .ifne @var{absolute expression}
5006 Assembles the following section of code if the argument is not equal to zero
5007 (in other words, this is equivalent to @code{.if}).
5009 @cindex @code{ifnes} directive
5010 @item .ifnes @var{string1},@var{string2}
5011 Like @code{.ifeqs}, but the sense of the test is reversed: this assembles the
5012 following section of code if the two strings are not the same.
5016 @section @code{.incbin "@var{file}"[,@var{skip}[,@var{count}]]}
5018 @cindex @code{incbin} directive
5019 @cindex binary files, including
5020 The @code{incbin} directive includes @var{file} verbatim at the current
5021 location. You can control the search paths used with the @samp{-I} command-line
5022 option (@pxref{Invoking,,Command-Line Options}). Quotation marks are required
5025 The @var{skip} argument skips a number of bytes from the start of the
5026 @var{file}. The @var{count} argument indicates the maximum number of bytes to
5027 read. Note that the data is not aligned in any way, so it is the user's
5028 responsibility to make sure that proper alignment is provided both before and
5029 after the @code{incbin} directive.
5032 @section @code{.include "@var{file}"}
5034 @cindex @code{include} directive
5035 @cindex supporting files, including
5036 @cindex files, including
5037 This directive provides a way to include supporting files at specified
5038 points in your source program. The code from @var{file} is assembled as
5039 if it followed the point of the @code{.include}; when the end of the
5040 included file is reached, assembly of the original file continues. You
5041 can control the search paths used with the @samp{-I} command-line option
5042 (@pxref{Invoking,,Command-Line Options}). Quotation marks are required
5046 @section @code{.int @var{expressions}}
5048 @cindex @code{int} directive
5049 @cindex integers, 32-bit
5050 Expect zero or more @var{expressions}, of any section, separated by commas.
5051 For each expression, emit a number that, at run time, is the value of that
5052 expression. The byte order and bit size of the number depends on what kind
5053 of target the assembly is for.
5057 On most forms of the H8/300, @code{.int} emits 16-bit
5058 integers. On the H8/300H and the Renesas SH, however, @code{.int} emits
5065 @section @code{.internal @var{names}}
5067 @cindex @code{internal} directive
5069 This is one of the ELF visibility directives. The other two are
5070 @code{.hidden} (@pxref{Hidden,,@code{.hidden}}) and
5071 @code{.protected} (@pxref{Protected,,@code{.protected}}).
5073 This directive overrides the named symbols default visibility (which is set by
5074 their binding: local, global or weak). The directive sets the visibility to
5075 @code{internal} which means that the symbols are considered to be @code{hidden}
5076 (i.e., not visible to other components), and that some extra, processor specific
5077 processing must also be performed upon the symbols as well.
5081 @section @code{.irp @var{symbol},@var{values}}@dots{}
5083 @cindex @code{irp} directive
5084 Evaluate a sequence of statements assigning different values to @var{symbol}.
5085 The sequence of statements starts at the @code{.irp} directive, and is
5086 terminated by an @code{.endr} directive. For each @var{value}, @var{symbol} is
5087 set to @var{value}, and the sequence of statements is assembled. If no
5088 @var{value} is listed, the sequence of statements is assembled once, with
5089 @var{symbol} set to the null string. To refer to @var{symbol} within the
5090 sequence of statements, use @var{\symbol}.
5092 For example, assembling
5100 is equivalent to assembling
5108 For some caveats with the spelling of @var{symbol}, see also @ref{Macro}.
5111 @section @code{.irpc @var{symbol},@var{values}}@dots{}
5113 @cindex @code{irpc} directive
5114 Evaluate a sequence of statements assigning different values to @var{symbol}.
5115 The sequence of statements starts at the @code{.irpc} directive, and is
5116 terminated by an @code{.endr} directive. For each character in @var{value},
5117 @var{symbol} is set to the character, and the sequence of statements is
5118 assembled. If no @var{value} is listed, the sequence of statements is
5119 assembled once, with @var{symbol} set to the null string. To refer to
5120 @var{symbol} within the sequence of statements, use @var{\symbol}.
5122 For example, assembling
5130 is equivalent to assembling
5138 For some caveats with the spelling of @var{symbol}, see also the discussion
5142 @section @code{.lcomm @var{symbol} , @var{length}}
5144 @cindex @code{lcomm} directive
5145 @cindex local common symbols
5146 @cindex symbols, local common
5147 Reserve @var{length} (an absolute expression) bytes for a local common
5148 denoted by @var{symbol}. The section and value of @var{symbol} are
5149 those of the new local common. The addresses are allocated in the bss
5150 section, so that at run-time the bytes start off zeroed. @var{Symbol}
5151 is not declared global (@pxref{Global,,@code{.global}}), so is normally
5152 not visible to @code{@value{LD}}.
5155 Some targets permit a third argument to be used with @code{.lcomm}. This
5156 argument specifies the desired alignment of the symbol in the bss section.
5160 The syntax for @code{.lcomm} differs slightly on the HPPA. The syntax is
5161 @samp{@var{symbol} .lcomm, @var{length}}; @var{symbol} is optional.
5165 @section @code{.lflags}
5167 @cindex @code{lflags} directive (ignored)
5168 @command{@value{AS}} accepts this directive, for compatibility with other
5169 assemblers, but ignores it.
5171 @ifclear no-line-dir
5173 @section @code{.line @var{line-number}}
5175 @cindex @code{line} directive
5176 @cindex logical line number
5178 Change the logical line number. @var{line-number} must be an absolute
5179 expression. The next line has that logical line number. Therefore any other
5180 statements on the current line (after a statement separator character) are
5181 reported as on logical line number @var{line-number} @minus{} 1. One day
5182 @command{@value{AS}} will no longer support this directive: it is recognized only
5183 for compatibility with existing assembler programs.
5186 Even though this is a directive associated with the @code{a.out} or
5187 @code{b.out} object-code formats, @command{@value{AS}} still recognizes it
5188 when producing COFF output, and treats @samp{.line} as though it
5189 were the COFF @samp{.ln} @emph{if} it is found outside a
5190 @code{.def}/@code{.endef} pair.
5192 Inside a @code{.def}, @samp{.line} is, instead, one of the directives
5193 used by compilers to generate auxiliary symbol information for
5198 @section @code{.linkonce [@var{type}]}
5200 @cindex @code{linkonce} directive
5201 @cindex common sections
5202 Mark the current section so that the linker only includes a single copy of it.
5203 This may be used to include the same section in several different object files,
5204 but ensure that the linker will only include it once in the final output file.
5205 The @code{.linkonce} pseudo-op must be used for each instance of the section.
5206 Duplicate sections are detected based on the section name, so it should be
5209 This directive is only supported by a few object file formats; as of this
5210 writing, the only object file format which supports it is the Portable
5211 Executable format used on Windows NT.
5213 The @var{type} argument is optional. If specified, it must be one of the
5214 following strings. For example:
5218 Not all types may be supported on all object file formats.
5222 Silently discard duplicate sections. This is the default.
5225 Warn if there are duplicate sections, but still keep only one copy.
5228 Warn if any of the duplicates have different sizes.
5231 Warn if any of the duplicates do not have exactly the same contents.
5235 @section @code{.list}
5237 @cindex @code{list} directive
5238 @cindex listing control, turning on
5239 Control (in conjunction with the @code{.nolist} directive) whether or
5240 not assembly listings are generated. These two directives maintain an
5241 internal counter (which is zero initially). @code{.list} increments the
5242 counter, and @code{.nolist} decrements it. Assembly listings are
5243 generated whenever the counter is greater than zero.
5245 By default, listings are disabled. When you enable them (with the
5246 @samp{-a} command line option; @pxref{Invoking,,Command-Line Options}),
5247 the initial value of the listing counter is one.
5250 @section @code{.ln @var{line-number}}
5252 @cindex @code{ln} directive
5253 @ifclear no-line-dir
5254 @samp{.ln} is a synonym for @samp{.line}.
5257 Tell @command{@value{AS}} to change the logical line number. @var{line-number}
5258 must be an absolute expression. The next line has that logical
5259 line number, so any other statements on the current line (after a
5260 statement separator character @code{;}) are reported as on logical
5261 line number @var{line-number} @minus{} 1.
5264 This directive is accepted, but ignored, when @command{@value{AS}} is
5265 configured for @code{b.out}; its effect is only associated with COFF
5271 @section @code{.loc @var{fileno} @var{lineno} [@var{column}] [@var{options}]}
5272 @cindex @code{loc} directive
5273 When emitting DWARF2 line number information,
5274 the @code{.loc} directive will add a row to the @code{.debug_line} line
5275 number matrix corresponding to the immediately following assembly
5276 instruction. The @var{fileno}, @var{lineno}, and optional @var{column}
5277 arguments will be applied to the @code{.debug_line} state machine before
5280 The @var{options} are a sequence of the following tokens in any order:
5284 This option will set the @code{basic_block} register in the
5285 @code{.debug_line} state machine to @code{true}.
5288 This option will set the @code{prologue_end} register in the
5289 @code{.debug_line} state machine to @code{true}.
5291 @item epilogue_begin
5292 This option will set the @code{epilogue_begin} register in the
5293 @code{.debug_line} state machine to @code{true}.
5295 @item is_stmt @var{value}
5296 This option will set the @code{is_stmt} register in the
5297 @code{.debug_line} state machine to @code{value}, which must be
5300 @item isa @var{value}
5301 This directive will set the @code{isa} register in the @code{.debug_line}
5302 state machine to @var{value}, which must be an unsigned integer.
5304 @item discriminator @var{value}
5305 This directive will set the @code{discriminator} register in the @code{.debug_line}
5306 state machine to @var{value}, which must be an unsigned integer.
5310 @node Loc_mark_labels
5311 @section @code{.loc_mark_labels @var{enable}}
5312 @cindex @code{loc_mark_labels} directive
5313 When emitting DWARF2 line number information,
5314 the @code{.loc_mark_labels} directive makes the assembler emit an entry
5315 to the @code{.debug_line} line number matrix with the @code{basic_block}
5316 register in the state machine set whenever a code label is seen.
5317 The @var{enable} argument should be either 1 or 0, to enable or disable
5318 this function respectively.
5322 @section @code{.local @var{names}}
5324 @cindex @code{local} directive
5325 This directive, which is available for ELF targets, marks each symbol in
5326 the comma-separated list of @code{names} as a local symbol so that it
5327 will not be externally visible. If the symbols do not already exist,
5328 they will be created.
5330 For targets where the @code{.lcomm} directive (@pxref{Lcomm}) does not
5331 accept an alignment argument, which is the case for most ELF targets,
5332 the @code{.local} directive can be used in combination with @code{.comm}
5333 (@pxref{Comm}) to define aligned local common data.
5337 @section @code{.long @var{expressions}}
5339 @cindex @code{long} directive
5340 @code{.long} is the same as @samp{.int}. @xref{Int,,@code{.int}}.
5343 @c no one seems to know what this is for or whether this description is
5344 @c what it really ought to do
5346 @section @code{.lsym @var{symbol}, @var{expression}}
5348 @cindex @code{lsym} directive
5349 @cindex symbol, not referenced in assembly
5350 @code{.lsym} creates a new symbol named @var{symbol}, but does not put it in
5351 the hash table, ensuring it cannot be referenced by name during the
5352 rest of the assembly. This sets the attributes of the symbol to be
5353 the same as the expression value:
5355 @var{other} = @var{descriptor} = 0
5356 @var{type} = @r{(section of @var{expression})}
5357 @var{value} = @var{expression}
5360 The new symbol is not flagged as external.
5364 @section @code{.macro}
5367 The commands @code{.macro} and @code{.endm} allow you to define macros that
5368 generate assembly output. For example, this definition specifies a macro
5369 @code{sum} that puts a sequence of numbers into memory:
5372 .macro sum from=0, to=5
5381 With that definition, @samp{SUM 0,5} is equivalent to this assembly input:
5393 @item .macro @var{macname}
5394 @itemx .macro @var{macname} @var{macargs} @dots{}
5395 @cindex @code{macro} directive
5396 Begin the definition of a macro called @var{macname}. If your macro
5397 definition requires arguments, specify their names after the macro name,
5398 separated by commas or spaces. You can qualify the macro argument to
5399 indicate whether all invocations must specify a non-blank value (through
5400 @samp{:@code{req}}), or whether it takes all of the remaining arguments
5401 (through @samp{:@code{vararg}}). You can supply a default value for any
5402 macro argument by following the name with @samp{=@var{deflt}}. You
5403 cannot define two macros with the same @var{macname} unless it has been
5404 subject to the @code{.purgem} directive (@pxref{Purgem}) between the two
5405 definitions. For example, these are all valid @code{.macro} statements:
5409 Begin the definition of a macro called @code{comm}, which takes no
5412 @item .macro plus1 p, p1
5413 @itemx .macro plus1 p p1
5414 Either statement begins the definition of a macro called @code{plus1},
5415 which takes two arguments; within the macro definition, write
5416 @samp{\p} or @samp{\p1} to evaluate the arguments.
5418 @item .macro reserve_str p1=0 p2
5419 Begin the definition of a macro called @code{reserve_str}, with two
5420 arguments. The first argument has a default value, but not the second.
5421 After the definition is complete, you can call the macro either as
5422 @samp{reserve_str @var{a},@var{b}} (with @samp{\p1} evaluating to
5423 @var{a} and @samp{\p2} evaluating to @var{b}), or as @samp{reserve_str
5424 ,@var{b}} (with @samp{\p1} evaluating as the default, in this case
5425 @samp{0}, and @samp{\p2} evaluating to @var{b}).
5427 @item .macro m p1:req, p2=0, p3:vararg
5428 Begin the definition of a macro called @code{m}, with at least three
5429 arguments. The first argument must always have a value specified, but
5430 not the second, which instead has a default value. The third formal
5431 will get assigned all remaining arguments specified at invocation time.
5433 When you call a macro, you can specify the argument values either by
5434 position, or by keyword. For example, @samp{sum 9,17} is equivalent to
5435 @samp{sum to=17, from=9}.
5439 Note that since each of the @var{macargs} can be an identifier exactly
5440 as any other one permitted by the target architecture, there may be
5441 occasional problems if the target hand-crafts special meanings to certain
5442 characters when they occur in a special position. For example, if the colon
5443 (@code{:}) is generally permitted to be part of a symbol name, but the
5444 architecture specific code special-cases it when occurring as the final
5445 character of a symbol (to denote a label), then the macro parameter
5446 replacement code will have no way of knowing that and consider the whole
5447 construct (including the colon) an identifier, and check only this
5448 identifier for being the subject to parameter substitution. So for example
5449 this macro definition:
5457 might not work as expected. Invoking @samp{label foo} might not create a label
5458 called @samp{foo} but instead just insert the text @samp{\l:} into the
5459 assembler source, probably generating an error about an unrecognised
5462 Similarly problems might occur with the period character (@samp{.})
5463 which is often allowed inside opcode names (and hence identifier names). So
5464 for example constructing a macro to build an opcode from a base name and a
5465 length specifier like this:
5468 .macro opcode base length
5473 and invoking it as @samp{opcode store l} will not create a @samp{store.l}
5474 instruction but instead generate some kind of error as the assembler tries to
5475 interpret the text @samp{\base.\length}.
5477 There are several possible ways around this problem:
5480 @item Insert white space
5481 If it is possible to use white space characters then this is the simplest
5490 @item Use @samp{\()}
5491 The string @samp{\()} can be used to separate the end of a macro argument from
5492 the following text. eg:
5495 .macro opcode base length
5500 @item Use the alternate macro syntax mode
5501 In the alternative macro syntax mode the ampersand character (@samp{&}) can be
5502 used as a separator. eg:
5512 Note: this problem of correctly identifying string parameters to pseudo ops
5513 also applies to the identifiers used in @code{.irp} (@pxref{Irp})
5514 and @code{.irpc} (@pxref{Irpc}) as well.
5517 @cindex @code{endm} directive
5518 Mark the end of a macro definition.
5521 @cindex @code{exitm} directive
5522 Exit early from the current macro definition.
5524 @cindex number of macros executed
5525 @cindex macros, count executed
5527 @command{@value{AS}} maintains a counter of how many macros it has
5528 executed in this pseudo-variable; you can copy that number to your
5529 output with @samp{\@@}, but @emph{only within a macro definition}.
5531 @item LOCAL @var{name} [ , @dots{} ]
5532 @emph{Warning: @code{LOCAL} is only available if you select ``alternate
5533 macro syntax'' with @samp{--alternate} or @code{.altmacro}.}
5534 @xref{Altmacro,,@code{.altmacro}}.
5538 @section @code{.mri @var{val}}
5540 @cindex @code{mri} directive
5541 @cindex MRI mode, temporarily
5542 If @var{val} is non-zero, this tells @command{@value{AS}} to enter MRI mode. If
5543 @var{val} is zero, this tells @command{@value{AS}} to exit MRI mode. This change
5544 affects code assembled until the next @code{.mri} directive, or until the end
5545 of the file. @xref{M, MRI mode, MRI mode}.
5548 @section @code{.noaltmacro}
5549 Disable alternate macro mode. @xref{Altmacro}.
5552 @section @code{.nolist}
5554 @cindex @code{nolist} directive
5555 @cindex listing control, turning off
5556 Control (in conjunction with the @code{.list} directive) whether or
5557 not assembly listings are generated. These two directives maintain an
5558 internal counter (which is zero initially). @code{.list} increments the
5559 counter, and @code{.nolist} decrements it. Assembly listings are
5560 generated whenever the counter is greater than zero.
5563 @section @code{.octa @var{bignums}}
5565 @c FIXME: double size emitted for "octa" on i960, others? Or warn?
5566 @cindex @code{octa} directive
5567 @cindex integer, 16-byte
5568 @cindex sixteen byte integer
5569 This directive expects zero or more bignums, separated by commas. For each
5570 bignum, it emits a 16-byte integer.
5572 The term ``octa'' comes from contexts in which a ``word'' is two bytes;
5573 hence @emph{octa}-word for 16 bytes.
5576 @section @code{.offset @var{loc}}
5578 @cindex @code{offset} directive
5579 Set the location counter to @var{loc} in the absolute section. @var{loc} must
5580 be an absolute expression. This directive may be useful for defining
5581 symbols with absolute values. Do not confuse it with the @code{.org}
5585 @section @code{.org @var{new-lc} , @var{fill}}
5587 @cindex @code{org} directive
5588 @cindex location counter, advancing
5589 @cindex advancing location counter
5590 @cindex current address, advancing
5591 Advance the location counter of the current section to
5592 @var{new-lc}. @var{new-lc} is either an absolute expression or an
5593 expression with the same section as the current subsection. That is,
5594 you can't use @code{.org} to cross sections: if @var{new-lc} has the
5595 wrong section, the @code{.org} directive is ignored. To be compatible
5596 with former assemblers, if the section of @var{new-lc} is absolute,
5597 @command{@value{AS}} issues a warning, then pretends the section of @var{new-lc}
5598 is the same as the current subsection.
5600 @code{.org} may only increase the location counter, or leave it
5601 unchanged; you cannot use @code{.org} to move the location counter
5604 @c double negative used below "not undefined" because this is a specific
5605 @c reference to "undefined" (as SEG_UNKNOWN is called in this manual)
5606 @c section. doc@cygnus.com 18feb91
5607 Because @command{@value{AS}} tries to assemble programs in one pass, @var{new-lc}
5608 may not be undefined. If you really detest this restriction we eagerly await
5609 a chance to share your improved assembler.
5611 Beware that the origin is relative to the start of the section, not
5612 to the start of the subsection. This is compatible with other
5613 people's assemblers.
5615 When the location counter (of the current subsection) is advanced, the
5616 intervening bytes are filled with @var{fill} which should be an
5617 absolute expression. If the comma and @var{fill} are omitted,
5618 @var{fill} defaults to zero.
5621 @section @code{.p2align[wl] @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
5623 @cindex padding the location counter given a power of two
5624 @cindex @code{p2align} directive
5625 Pad the location counter (in the current subsection) to a particular
5626 storage boundary. The first expression (which must be absolute) is the
5627 number of low-order zero bits the location counter must have after
5628 advancement. For example @samp{.p2align 3} advances the location
5629 counter until it a multiple of 8. If the location counter is already a
5630 multiple of 8, no change is needed.
5632 The second expression (also absolute) gives the fill value to be stored in the
5633 padding bytes. It (and the comma) may be omitted. If it is omitted, the
5634 padding bytes are normally zero. However, on some systems, if the section is
5635 marked as containing code and the fill value is omitted, the space is filled
5636 with no-op instructions.
5638 The third expression is also absolute, and is also optional. If it is present,
5639 it is the maximum number of bytes that should be skipped by this alignment
5640 directive. If doing the alignment would require skipping more bytes than the
5641 specified maximum, then the alignment is not done at all. You can omit the
5642 fill value (the second argument) entirely by simply using two commas after the
5643 required alignment; this can be useful if you want the alignment to be filled
5644 with no-op instructions when appropriate.
5646 @cindex @code{p2alignw} directive
5647 @cindex @code{p2alignl} directive
5648 The @code{.p2alignw} and @code{.p2alignl} directives are variants of the
5649 @code{.p2align} directive. The @code{.p2alignw} directive treats the fill
5650 pattern as a two byte word value. The @code{.p2alignl} directives treats the
5651 fill pattern as a four byte longword value. For example, @code{.p2alignw
5652 2,0x368d} will align to a multiple of 4. If it skips two bytes, they will be
5653 filled in with the value 0x368d (the exact placement of the bytes depends upon
5654 the endianness of the processor). If it skips 1 or 3 bytes, the fill value is
5659 @section @code{.popsection}
5661 @cindex @code{popsection} directive
5662 @cindex Section Stack
5663 This is one of the ELF section stack manipulation directives. The others are
5664 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
5665 @code{.pushsection} (@pxref{PushSection}), and @code{.previous}
5668 This directive replaces the current section (and subsection) with the top
5669 section (and subsection) on the section stack. This section is popped off the
5675 @section @code{.previous}
5677 @cindex @code{previous} directive
5678 @cindex Section Stack
5679 This is one of the ELF section stack manipulation directives. The others are
5680 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
5681 @code{.pushsection} (@pxref{PushSection}), and @code{.popsection}
5682 (@pxref{PopSection}).
5684 This directive swaps the current section (and subsection) with most recently
5685 referenced section/subsection pair prior to this one. Multiple
5686 @code{.previous} directives in a row will flip between two sections (and their
5687 subsections). For example:
5699 Will place 0x1234 and 0x9abc into subsection 1 and 0x5678 into subsection 2 of
5705 # Now in section A subsection 1
5709 # Now in section B subsection 0
5712 # Now in section B subsection 1
5715 # Now in section B subsection 0
5719 Will place 0x1234 into section A, 0x5678 and 0xdef0 into subsection 0 of
5720 section B and 0x9abc into subsection 1 of section B.
5722 In terms of the section stack, this directive swaps the current section with
5723 the top section on the section stack.
5727 @section @code{.print @var{string}}
5729 @cindex @code{print} directive
5730 @command{@value{AS}} will print @var{string} on the standard output during
5731 assembly. You must put @var{string} in double quotes.
5735 @section @code{.protected @var{names}}
5737 @cindex @code{protected} directive
5739 This is one of the ELF visibility directives. The other two are
5740 @code{.hidden} (@pxref{Hidden}) and @code{.internal} (@pxref{Internal}).
5742 This directive overrides the named symbols default visibility (which is set by
5743 their binding: local, global or weak). The directive sets the visibility to
5744 @code{protected} which means that any references to the symbols from within the
5745 components that defines them must be resolved to the definition in that
5746 component, even if a definition in another component would normally preempt
5751 @section @code{.psize @var{lines} , @var{columns}}
5753 @cindex @code{psize} directive
5754 @cindex listing control: paper size
5755 @cindex paper size, for listings
5756 Use this directive to declare the number of lines---and, optionally, the
5757 number of columns---to use for each page, when generating listings.
5759 If you do not use @code{.psize}, listings use a default line-count
5760 of 60. You may omit the comma and @var{columns} specification; the
5761 default width is 200 columns.
5763 @command{@value{AS}} generates formfeeds whenever the specified number of
5764 lines is exceeded (or whenever you explicitly request one, using
5767 If you specify @var{lines} as @code{0}, no formfeeds are generated save
5768 those explicitly specified with @code{.eject}.
5771 @section @code{.purgem @var{name}}
5773 @cindex @code{purgem} directive
5774 Undefine the macro @var{name}, so that later uses of the string will not be
5775 expanded. @xref{Macro}.
5779 @section @code{.pushsection @var{name} [, @var{subsection}] [, "@var{flags}"[, @@@var{type}[,@var{arguments}]]]}
5781 @cindex @code{pushsection} directive
5782 @cindex Section Stack
5783 This is one of the ELF section stack manipulation directives. The others are
5784 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
5785 @code{.popsection} (@pxref{PopSection}), and @code{.previous}
5788 This directive pushes the current section (and subsection) onto the
5789 top of the section stack, and then replaces the current section and
5790 subsection with @code{name} and @code{subsection}. The optional
5791 @code{flags}, @code{type} and @code{arguments} are treated the same
5792 as in the @code{.section} (@pxref{Section}) directive.
5796 @section @code{.quad @var{bignums}}
5798 @cindex @code{quad} directive
5799 @code{.quad} expects zero or more bignums, separated by commas. For
5800 each bignum, it emits
5802 an 8-byte integer. If the bignum won't fit in 8 bytes, it prints a
5803 warning message; and just takes the lowest order 8 bytes of the bignum.
5804 @cindex eight-byte integer
5805 @cindex integer, 8-byte
5807 The term ``quad'' comes from contexts in which a ``word'' is two bytes;
5808 hence @emph{quad}-word for 8 bytes.
5811 a 16-byte integer. If the bignum won't fit in 16 bytes, it prints a
5812 warning message; and just takes the lowest order 16 bytes of the bignum.
5813 @cindex sixteen-byte integer
5814 @cindex integer, 16-byte
5818 @section @code{.reloc @var{offset}, @var{reloc_name}[, @var{expression}]}
5820 @cindex @code{reloc} directive
5821 Generate a relocation at @var{offset} of type @var{reloc_name} with value
5822 @var{expression}. If @var{offset} is a number, the relocation is generated in
5823 the current section. If @var{offset} is an expression that resolves to a
5824 symbol plus offset, the relocation is generated in the given symbol's section.
5825 @var{expression}, if present, must resolve to a symbol plus addend or to an
5826 absolute value, but note that not all targets support an addend. e.g. ELF REL
5827 targets such as i386 store an addend in the section contents rather than in the
5828 relocation. This low level interface does not support addends stored in the
5832 @section @code{.rept @var{count}}
5834 @cindex @code{rept} directive
5835 Repeat the sequence of lines between the @code{.rept} directive and the next
5836 @code{.endr} directive @var{count} times.
5838 For example, assembling
5846 is equivalent to assembling
5855 @section @code{.sbttl "@var{subheading}"}
5857 @cindex @code{sbttl} directive
5858 @cindex subtitles for listings
5859 @cindex listing control: subtitle
5860 Use @var{subheading} as the title (third line, immediately after the
5861 title line) when generating assembly listings.
5863 This directive affects subsequent pages, as well as the current page if
5864 it appears within ten lines of the top of a page.
5868 @section @code{.scl @var{class}}
5870 @cindex @code{scl} directive
5871 @cindex symbol storage class (COFF)
5872 @cindex COFF symbol storage class
5873 Set the storage-class value for a symbol. This directive may only be
5874 used inside a @code{.def}/@code{.endef} pair. Storage class may flag
5875 whether a symbol is static or external, or it may record further
5876 symbolic debugging information.
5879 The @samp{.scl} directive is primarily associated with COFF output; when
5880 configured to generate @code{b.out} output format, @command{@value{AS}}
5881 accepts this directive but ignores it.
5887 @section @code{.section @var{name}}
5889 @cindex named section
5890 Use the @code{.section} directive to assemble the following code into a section
5893 This directive is only supported for targets that actually support arbitrarily
5894 named sections; on @code{a.out} targets, for example, it is not accepted, even
5895 with a standard @code{a.out} section name.
5899 @c only print the extra heading if both COFF and ELF are set
5900 @subheading COFF Version
5903 @cindex @code{section} directive (COFF version)
5904 For COFF targets, the @code{.section} directive is used in one of the following
5908 .section @var{name}[, "@var{flags}"]
5909 .section @var{name}[, @var{subsection}]
5912 If the optional argument is quoted, it is taken as flags to use for the
5913 section. Each flag is a single character. The following flags are recognized:
5916 bss section (uninitialized data)
5918 section is not loaded
5928 shared section (meaningful for PE targets)
5930 ignored. (For compatibility with the ELF version)
5932 section is not readable (meaningful for PE targets)
5934 single-digit power-of-two section alignment (GNU extension)
5937 If no flags are specified, the default flags depend upon the section name. If
5938 the section name is not recognized, the default will be for the section to be
5939 loaded and writable. Note the @code{n} and @code{w} flags remove attributes
5940 from the section, rather than adding them, so if they are used on their own it
5941 will be as if no flags had been specified at all.
5943 If the optional argument to the @code{.section} directive is not quoted, it is
5944 taken as a subsection number (@pxref{Sub-Sections}).
5949 @c only print the extra heading if both COFF and ELF are set
5950 @subheading ELF Version
5953 @cindex Section Stack
5954 This is one of the ELF section stack manipulation directives. The others are
5955 @code{.subsection} (@pxref{SubSection}), @code{.pushsection}
5956 (@pxref{PushSection}), @code{.popsection} (@pxref{PopSection}), and
5957 @code{.previous} (@pxref{Previous}).
5959 @cindex @code{section} directive (ELF version)
5960 For ELF targets, the @code{.section} directive is used like this:
5963 .section @var{name} [, "@var{flags}"[, @@@var{type}[,@var{flag_specific_arguments}]]]
5966 The optional @var{flags} argument is a quoted string which may contain any
5967 combination of the following characters:
5970 section is allocatable
5972 section is excluded from executable and shared library.
5976 section is executable
5978 section is mergeable
5980 section contains zero terminated strings
5982 section is a member of a section group
5984 section is used for thread-local-storage
5986 section is a member of the previously-current section's group, if any
5989 The optional @var{type} argument may contain one of the following constants:
5992 section contains data
5994 section does not contain data (i.e., section only occupies space)
5996 section contains data which is used by things other than the program
5998 section contains an array of pointers to init functions
6000 section contains an array of pointers to finish functions
6001 @item @@preinit_array
6002 section contains an array of pointers to pre-init functions
6005 Many targets only support the first three section types.
6007 Note on targets where the @code{@@} character is the start of a comment (eg
6008 ARM) then another character is used instead. For example the ARM port uses the
6011 If @var{flags} contains the @code{M} symbol then the @var{type} argument must
6012 be specified as well as an extra argument---@var{entsize}---like this:
6015 .section @var{name} , "@var{flags}"M, @@@var{type}, @var{entsize}
6018 Sections with the @code{M} flag but not @code{S} flag must contain fixed size
6019 constants, each @var{entsize} octets long. Sections with both @code{M} and
6020 @code{S} must contain zero terminated strings where each character is
6021 @var{entsize} bytes long. The linker may remove duplicates within sections with
6022 the same name, same entity size and same flags. @var{entsize} must be an
6023 absolute expression. For sections with both @code{M} and @code{S}, a string
6024 which is a suffix of a larger string is considered a duplicate. Thus
6025 @code{"def"} will be merged with @code{"abcdef"}; A reference to the first
6026 @code{"def"} will be changed to a reference to @code{"abcdef"+3}.
6028 If @var{flags} contains the @code{G} symbol then the @var{type} argument must
6029 be present along with an additional field like this:
6032 .section @var{name} , "@var{flags}"G, @@@var{type}, @var{GroupName}[, @var{linkage}]
6035 The @var{GroupName} field specifies the name of the section group to which this
6036 particular section belongs. The optional linkage field can contain:
6039 indicates that only one copy of this section should be retained
6044 Note: if both the @var{M} and @var{G} flags are present then the fields for
6045 the Merge flag should come first, like this:
6048 .section @var{name} , "@var{flags}"MG, @@@var{type}, @var{entsize}, @var{GroupName}[, @var{linkage}]
6051 If @var{flags} contains the @code{?} symbol then it may not also contain the
6052 @code{G} symbol and the @var{GroupName} or @var{linkage} fields should not be
6053 present. Instead, @code{?} says to consider the section that's current before
6054 this directive. If that section used @code{G}, then the new section will use
6055 @code{G} with those same @var{GroupName} and @var{linkage} fields implicitly.
6056 If not, then the @code{?} symbol has no effect.
6058 If no flags are specified, the default flags depend upon the section name. If
6059 the section name is not recognized, the default will be for the section to have
6060 none of the above flags: it will not be allocated in memory, nor writable, nor
6061 executable. The section will contain data.
6063 For ELF targets, the assembler supports another type of @code{.section}
6064 directive for compatibility with the Solaris assembler:
6067 .section "@var{name}"[, @var{flags}...]
6070 Note that the section name is quoted. There may be a sequence of comma
6074 section is allocatable
6078 section is executable
6080 section is excluded from executable and shared library.
6082 section is used for thread local storage
6085 This directive replaces the current section and subsection. See the
6086 contents of the gas testsuite directory @code{gas/testsuite/gas/elf} for
6087 some examples of how this directive and the other section stack directives
6093 @section @code{.set @var{symbol}, @var{expression}}
6095 @cindex @code{set} directive
6096 @cindex symbol value, setting
6097 Set the value of @var{symbol} to @var{expression}. This
6098 changes @var{symbol}'s value and type to conform to
6099 @var{expression}. If @var{symbol} was flagged as external, it remains
6100 flagged (@pxref{Symbol Attributes}).
6102 You may @code{.set} a symbol many times in the same assembly.
6104 If you @code{.set} a global symbol, the value stored in the object
6105 file is the last value stored into it.
6108 On Z80 @code{set} is a real instruction, use
6109 @samp{@var{symbol} defl @var{expression}} instead.
6113 @section @code{.short @var{expressions}}
6115 @cindex @code{short} directive
6117 @code{.short} is normally the same as @samp{.word}.
6118 @xref{Word,,@code{.word}}.
6120 In some configurations, however, @code{.short} and @code{.word} generate
6121 numbers of different lengths. @xref{Machine Dependencies}.
6125 @code{.short} is the same as @samp{.word}. @xref{Word,,@code{.word}}.
6128 This expects zero or more @var{expressions}, and emits
6129 a 16 bit number for each.
6134 @section @code{.single @var{flonums}}
6136 @cindex @code{single} directive
6137 @cindex floating point numbers (single)
6138 This directive assembles zero or more flonums, separated by commas. It
6139 has the same effect as @code{.float}.
6141 The exact kind of floating point numbers emitted depends on how
6142 @command{@value{AS}} is configured. @xref{Machine Dependencies}.
6146 On the @value{TARGET} family, @code{.single} emits 32-bit floating point
6147 numbers in @sc{ieee} format.
6153 @section @code{.size}
6155 This directive is used to set the size associated with a symbol.
6159 @c only print the extra heading if both COFF and ELF are set
6160 @subheading COFF Version
6163 @cindex @code{size} directive (COFF version)
6164 For COFF targets, the @code{.size} directive is only permitted inside
6165 @code{.def}/@code{.endef} pairs. It is used like this:
6168 .size @var{expression}
6172 @samp{.size} is only meaningful when generating COFF format output; when
6173 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
6180 @c only print the extra heading if both COFF and ELF are set
6181 @subheading ELF Version
6184 @cindex @code{size} directive (ELF version)
6185 For ELF targets, the @code{.size} directive is used like this:
6188 .size @var{name} , @var{expression}
6191 This directive sets the size associated with a symbol @var{name}.
6192 The size in bytes is computed from @var{expression} which can make use of label
6193 arithmetic. This directive is typically used to set the size of function
6198 @ifclear no-space-dir
6200 @section @code{.skip @var{size} , @var{fill}}
6202 @cindex @code{skip} directive
6203 @cindex filling memory
6204 This directive emits @var{size} bytes, each of value @var{fill}. Both
6205 @var{size} and @var{fill} are absolute expressions. If the comma and
6206 @var{fill} are omitted, @var{fill} is assumed to be zero. This is the same as
6211 @section @code{.sleb128 @var{expressions}}
6213 @cindex @code{sleb128} directive
6214 @var{sleb128} stands for ``signed little endian base 128.'' This is a
6215 compact, variable length representation of numbers used by the DWARF
6216 symbolic debugging format. @xref{Uleb128, ,@code{.uleb128}}.
6218 @ifclear no-space-dir
6220 @section @code{.space @var{size} , @var{fill}}
6222 @cindex @code{space} directive
6223 @cindex filling memory
6224 This directive emits @var{size} bytes, each of value @var{fill}. Both
6225 @var{size} and @var{fill} are absolute expressions. If the comma
6226 and @var{fill} are omitted, @var{fill} is assumed to be zero. This is the same
6231 @emph{Warning:} @code{.space} has a completely different meaning for HPPA
6232 targets; use @code{.block} as a substitute. See @cite{HP9000 Series 800
6233 Assembly Language Reference Manual} (HP 92432-90001) for the meaning of the
6234 @code{.space} directive. @xref{HPPA Directives,,HPPA Assembler Directives},
6242 @section @code{.stabd, .stabn, .stabs}
6244 @cindex symbolic debuggers, information for
6245 @cindex @code{stab@var{x}} directives
6246 There are three directives that begin @samp{.stab}.
6247 All emit symbols (@pxref{Symbols}), for use by symbolic debuggers.
6248 The symbols are not entered in the @command{@value{AS}} hash table: they
6249 cannot be referenced elsewhere in the source file.
6250 Up to five fields are required:
6254 This is the symbol's name. It may contain any character except
6255 @samp{\000}, so is more general than ordinary symbol names. Some
6256 debuggers used to code arbitrarily complex structures into symbol names
6260 An absolute expression. The symbol's type is set to the low 8 bits of
6261 this expression. Any bit pattern is permitted, but @code{@value{LD}}
6262 and debuggers choke on silly bit patterns.
6265 An absolute expression. The symbol's ``other'' attribute is set to the
6266 low 8 bits of this expression.
6269 An absolute expression. The symbol's descriptor is set to the low 16
6270 bits of this expression.
6273 An absolute expression which becomes the symbol's value.
6276 If a warning is detected while reading a @code{.stabd}, @code{.stabn},
6277 or @code{.stabs} statement, the symbol has probably already been created;
6278 you get a half-formed symbol in your object file. This is
6279 compatible with earlier assemblers!
6282 @cindex @code{stabd} directive
6283 @item .stabd @var{type} , @var{other} , @var{desc}
6285 The ``name'' of the symbol generated is not even an empty string.
6286 It is a null pointer, for compatibility. Older assemblers used a
6287 null pointer so they didn't waste space in object files with empty
6290 The symbol's value is set to the location counter,
6291 relocatably. When your program is linked, the value of this symbol
6292 is the address of the location counter when the @code{.stabd} was
6295 @cindex @code{stabn} directive
6296 @item .stabn @var{type} , @var{other} , @var{desc} , @var{value}
6297 The name of the symbol is set to the empty string @code{""}.
6299 @cindex @code{stabs} directive
6300 @item .stabs @var{string} , @var{type} , @var{other} , @var{desc} , @var{value}
6301 All five fields are specified.
6307 @section @code{.string} "@var{str}", @code{.string8} "@var{str}", @code{.string16}
6308 "@var{str}", @code{.string32} "@var{str}", @code{.string64} "@var{str}"
6310 @cindex string, copying to object file
6311 @cindex string8, copying to object file
6312 @cindex string16, copying to object file
6313 @cindex string32, copying to object file
6314 @cindex string64, copying to object file
6315 @cindex @code{string} directive
6316 @cindex @code{string8} directive
6317 @cindex @code{string16} directive
6318 @cindex @code{string32} directive
6319 @cindex @code{string64} directive
6321 Copy the characters in @var{str} to the object file. You may specify more than
6322 one string to copy, separated by commas. Unless otherwise specified for a
6323 particular machine, the assembler marks the end of each string with a 0 byte.
6324 You can use any of the escape sequences described in @ref{Strings,,Strings}.
6326 The variants @code{string16}, @code{string32} and @code{string64} differ from
6327 the @code{string} pseudo opcode in that each 8-bit character from @var{str} is
6328 copied and expanded to 16, 32 or 64 bits respectively. The expanded characters
6329 are stored in target endianness byte order.
6335 .string "B\0\0\0Y\0\0\0E\0\0\0" /* On little endian targets. */
6336 .string "\0\0\0B\0\0\0Y\0\0\0E" /* On big endian targets. */
6341 @section @code{.struct @var{expression}}
6343 @cindex @code{struct} directive
6344 Switch to the absolute section, and set the section offset to @var{expression},
6345 which must be an absolute expression. You might use this as follows:
6354 This would define the symbol @code{field1} to have the value 0, the symbol
6355 @code{field2} to have the value 4, and the symbol @code{field3} to have the
6356 value 8. Assembly would be left in the absolute section, and you would need to
6357 use a @code{.section} directive of some sort to change to some other section
6358 before further assembly.
6362 @section @code{.subsection @var{name}}
6364 @cindex @code{subsection} directive
6365 @cindex Section Stack
6366 This is one of the ELF section stack manipulation directives. The others are
6367 @code{.section} (@pxref{Section}), @code{.pushsection} (@pxref{PushSection}),
6368 @code{.popsection} (@pxref{PopSection}), and @code{.previous}
6371 This directive replaces the current subsection with @code{name}. The current
6372 section is not changed. The replaced subsection is put onto the section stack
6373 in place of the then current top of stack subsection.
6378 @section @code{.symver}
6379 @cindex @code{symver} directive
6380 @cindex symbol versioning
6381 @cindex versions of symbols
6382 Use the @code{.symver} directive to bind symbols to specific version nodes
6383 within a source file. This is only supported on ELF platforms, and is
6384 typically used when assembling files to be linked into a shared library.
6385 There are cases where it may make sense to use this in objects to be bound
6386 into an application itself so as to override a versioned symbol from a
6389 For ELF targets, the @code{.symver} directive can be used like this:
6391 .symver @var{name}, @var{name2@@nodename}
6393 If the symbol @var{name} is defined within the file
6394 being assembled, the @code{.symver} directive effectively creates a symbol
6395 alias with the name @var{name2@@nodename}, and in fact the main reason that we
6396 just don't try and create a regular alias is that the @var{@@} character isn't
6397 permitted in symbol names. The @var{name2} part of the name is the actual name
6398 of the symbol by which it will be externally referenced. The name @var{name}
6399 itself is merely a name of convenience that is used so that it is possible to
6400 have definitions for multiple versions of a function within a single source
6401 file, and so that the compiler can unambiguously know which version of a
6402 function is being mentioned. The @var{nodename} portion of the alias should be
6403 the name of a node specified in the version script supplied to the linker when
6404 building a shared library. If you are attempting to override a versioned
6405 symbol from a shared library, then @var{nodename} should correspond to the
6406 nodename of the symbol you are trying to override.
6408 If the symbol @var{name} is not defined within the file being assembled, all
6409 references to @var{name} will be changed to @var{name2@@nodename}. If no
6410 reference to @var{name} is made, @var{name2@@nodename} will be removed from the
6413 Another usage of the @code{.symver} directive is:
6415 .symver @var{name}, @var{name2@@@@nodename}
6417 In this case, the symbol @var{name} must exist and be defined within
6418 the file being assembled. It is similar to @var{name2@@nodename}. The
6419 difference is @var{name2@@@@nodename} will also be used to resolve
6420 references to @var{name2} by the linker.
6422 The third usage of the @code{.symver} directive is:
6424 .symver @var{name}, @var{name2@@@@@@nodename}
6426 When @var{name} is not defined within the
6427 file being assembled, it is treated as @var{name2@@nodename}. When
6428 @var{name} is defined within the file being assembled, the symbol
6429 name, @var{name}, will be changed to @var{name2@@@@nodename}.
6434 @section @code{.tag @var{structname}}
6436 @cindex COFF structure debugging
6437 @cindex structure debugging, COFF
6438 @cindex @code{tag} directive
6439 This directive is generated by compilers to include auxiliary debugging
6440 information in the symbol table. It is only permitted inside
6441 @code{.def}/@code{.endef} pairs. Tags are used to link structure
6442 definitions in the symbol table with instances of those structures.
6445 @samp{.tag} is only used when generating COFF format output; when
6446 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
6452 @section @code{.text @var{subsection}}
6454 @cindex @code{text} directive
6455 Tells @command{@value{AS}} to assemble the following statements onto the end of
6456 the text subsection numbered @var{subsection}, which is an absolute
6457 expression. If @var{subsection} is omitted, subsection number zero
6461 @section @code{.title "@var{heading}"}
6463 @cindex @code{title} directive
6464 @cindex listing control: title line
6465 Use @var{heading} as the title (second line, immediately after the
6466 source file name and pagenumber) when generating assembly listings.
6468 This directive affects subsequent pages, as well as the current page if
6469 it appears within ten lines of the top of a page.
6473 @section @code{.type}
6475 This directive is used to set the type of a symbol.
6479 @c only print the extra heading if both COFF and ELF are set
6480 @subheading COFF Version
6483 @cindex COFF symbol type
6484 @cindex symbol type, COFF
6485 @cindex @code{type} directive (COFF version)
6486 For COFF targets, this directive is permitted only within
6487 @code{.def}/@code{.endef} pairs. It is used like this:
6493 This records the integer @var{int} as the type attribute of a symbol table
6497 @samp{.type} is associated only with COFF format output; when
6498 @command{@value{AS}} is configured for @code{b.out} output, it accepts this
6499 directive but ignores it.
6505 @c only print the extra heading if both COFF and ELF are set
6506 @subheading ELF Version
6509 @cindex ELF symbol type
6510 @cindex symbol type, ELF
6511 @cindex @code{type} directive (ELF version)
6512 For ELF targets, the @code{.type} directive is used like this:
6515 .type @var{name} , @var{type description}
6518 This sets the type of symbol @var{name} to be either a
6519 function symbol or an object symbol. There are five different syntaxes
6520 supported for the @var{type description} field, in order to provide
6521 compatibility with various other assemblers.
6523 Because some of the characters used in these syntaxes (such as @samp{@@} and
6524 @samp{#}) are comment characters for some architectures, some of the syntaxes
6525 below do not work on all architectures. The first variant will be accepted by
6526 the GNU assembler on all architectures so that variant should be used for
6527 maximum portability, if you do not need to assemble your code with other
6530 The syntaxes supported are:
6533 .type <name> STT_<TYPE_IN_UPPER_CASE>
6534 .type <name>,#<type>
6535 .type <name>,@@<type>
6536 .type <name>,%<type>
6537 .type <name>,"<type>"
6540 The types supported are:
6545 Mark the symbol as being a function name.
6548 @itemx gnu_indirect_function
6549 Mark the symbol as an indirect function when evaluated during reloc
6550 processing. (This is only supported on assemblers targeting GNU systems).
6554 Mark the symbol as being a data object.
6558 Mark the symbol as being a thead-local data object.
6562 Mark the symbol as being a common data object.
6566 Does not mark the symbol in any way. It is supported just for completeness.
6568 @item gnu_unique_object
6569 Marks the symbol as being a globally unique data object. The dynamic linker
6570 will make sure that in the entire process there is just one symbol with this
6571 name and type in use. (This is only supported on assemblers targeting GNU
6576 Note: Some targets support extra types in addition to those listed above.
6582 @section @code{.uleb128 @var{expressions}}
6584 @cindex @code{uleb128} directive
6585 @var{uleb128} stands for ``unsigned little endian base 128.'' This is a
6586 compact, variable length representation of numbers used by the DWARF
6587 symbolic debugging format. @xref{Sleb128, ,@code{.sleb128}}.
6591 @section @code{.val @var{addr}}
6593 @cindex @code{val} directive
6594 @cindex COFF value attribute
6595 @cindex value attribute, COFF
6596 This directive, permitted only within @code{.def}/@code{.endef} pairs,
6597 records the address @var{addr} as the value attribute of a symbol table
6601 @samp{.val} is used only for COFF output; when @command{@value{AS}} is
6602 configured for @code{b.out}, it accepts this directive but ignores it.
6608 @section @code{.version "@var{string}"}
6610 @cindex @code{version} directive
6611 This directive creates a @code{.note} section and places into it an ELF
6612 formatted note of type NT_VERSION. The note's name is set to @code{string}.
6617 @section @code{.vtable_entry @var{table}, @var{offset}}
6619 @cindex @code{vtable_entry} directive
6620 This directive finds or creates a symbol @code{table} and creates a
6621 @code{VTABLE_ENTRY} relocation for it with an addend of @code{offset}.
6624 @section @code{.vtable_inherit @var{child}, @var{parent}}
6626 @cindex @code{vtable_inherit} directive
6627 This directive finds the symbol @code{child} and finds or creates the symbol
6628 @code{parent} and then creates a @code{VTABLE_INHERIT} relocation for the
6629 parent whose addend is the value of the child symbol. As a special case the
6630 parent name of @code{0} is treated as referring to the @code{*ABS*} section.
6634 @section @code{.warning "@var{string}"}
6635 @cindex warning directive
6636 Similar to the directive @code{.error}
6637 (@pxref{Error,,@code{.error "@var{string}"}}), but just emits a warning.
6640 @section @code{.weak @var{names}}
6642 @cindex @code{weak} directive
6643 This directive sets the weak attribute on the comma separated list of symbol
6644 @code{names}. If the symbols do not already exist, they will be created.
6646 On COFF targets other than PE, weak symbols are a GNU extension. This
6647 directive sets the weak attribute on the comma separated list of symbol
6648 @code{names}. If the symbols do not already exist, they will be created.
6650 On the PE target, weak symbols are supported natively as weak aliases.
6651 When a weak symbol is created that is not an alias, GAS creates an
6652 alternate symbol to hold the default value.
6655 @section @code{.weakref @var{alias}, @var{target}}
6657 @cindex @code{weakref} directive
6658 This directive creates an alias to the target symbol that enables the symbol to
6659 be referenced with weak-symbol semantics, but without actually making it weak.
6660 If direct references or definitions of the symbol are present, then the symbol
6661 will not be weak, but if all references to it are through weak references, the
6662 symbol will be marked as weak in the symbol table.
6664 The effect is equivalent to moving all references to the alias to a separate
6665 assembly source file, renaming the alias to the symbol in it, declaring the
6666 symbol as weak there, and running a reloadable link to merge the object files
6667 resulting from the assembly of the new source file and the old source file that
6668 had the references to the alias removed.
6670 The alias itself never makes to the symbol table, and is entirely handled
6671 within the assembler.
6674 @section @code{.word @var{expressions}}
6676 @cindex @code{word} directive
6677 This directive expects zero or more @var{expressions}, of any section,
6678 separated by commas.
6681 For each expression, @command{@value{AS}} emits a 32-bit number.
6684 For each expression, @command{@value{AS}} emits a 16-bit number.
6689 The size of the number emitted, and its byte order,
6690 depend on what target computer the assembly is for.
6693 @c on amd29k, i960, sparc the "special treatment to support compilers" doesn't
6694 @c happen---32-bit addressability, period; no long/short jumps.
6695 @ifset DIFF-TBL-KLUGE
6696 @cindex difference tables altered
6697 @cindex altered difference tables
6699 @emph{Warning: Special Treatment to support Compilers}
6703 Machines with a 32-bit address space, but that do less than 32-bit
6704 addressing, require the following special treatment. If the machine of
6705 interest to you does 32-bit addressing (or doesn't require it;
6706 @pxref{Machine Dependencies}), you can ignore this issue.
6709 In order to assemble compiler output into something that works,
6710 @command{@value{AS}} occasionally does strange things to @samp{.word} directives.
6711 Directives of the form @samp{.word sym1-sym2} are often emitted by
6712 compilers as part of jump tables. Therefore, when @command{@value{AS}} assembles a
6713 directive of the form @samp{.word sym1-sym2}, and the difference between
6714 @code{sym1} and @code{sym2} does not fit in 16 bits, @command{@value{AS}}
6715 creates a @dfn{secondary jump table}, immediately before the next label.
6716 This secondary jump table is preceded by a short-jump to the
6717 first byte after the secondary table. This short-jump prevents the flow
6718 of control from accidentally falling into the new table. Inside the
6719 table is a long-jump to @code{sym2}. The original @samp{.word}
6720 contains @code{sym1} minus the address of the long-jump to
6723 If there were several occurrences of @samp{.word sym1-sym2} before the
6724 secondary jump table, all of them are adjusted. If there was a
6725 @samp{.word sym3-sym4}, that also did not fit in sixteen bits, a
6726 long-jump to @code{sym4} is included in the secondary jump table,
6727 and the @code{.word} directives are adjusted to contain @code{sym3}
6728 minus the address of the long-jump to @code{sym4}; and so on, for as many
6729 entries in the original jump table as necessary.
6732 @emph{This feature may be disabled by compiling @command{@value{AS}} with the
6733 @samp{-DWORKING_DOT_WORD} option.} This feature is likely to confuse
6734 assembly language programmers.
6737 @c end DIFF-TBL-KLUGE
6740 @section Deprecated Directives
6742 @cindex deprecated directives
6743 @cindex obsolescent directives
6744 One day these directives won't work.
6745 They are included for compatibility with older assemblers.
6752 @node Object Attributes
6753 @chapter Object Attributes
6754 @cindex object attributes
6756 @command{@value{AS}} assembles source files written for a specific architecture
6757 into object files for that architecture. But not all object files are alike.
6758 Many architectures support incompatible variations. For instance, floating
6759 point arguments might be passed in floating point registers if the object file
6760 requires hardware floating point support---or floating point arguments might be
6761 passed in integer registers if the object file supports processors with no
6762 hardware floating point unit. Or, if two objects are built for different
6763 generations of the same architecture, the combination may require the
6764 newer generation at run-time.
6766 This information is useful during and after linking. At link time,
6767 @command{@value{LD}} can warn about incompatible object files. After link
6768 time, tools like @command{gdb} can use it to process the linked file
6771 Compatibility information is recorded as a series of object attributes. Each
6772 attribute has a @dfn{vendor}, @dfn{tag}, and @dfn{value}. The vendor is a
6773 string, and indicates who sets the meaning of the tag. The tag is an integer,
6774 and indicates what property the attribute describes. The value may be a string
6775 or an integer, and indicates how the property affects this object. Missing
6776 attributes are the same as attributes with a zero value or empty string value.
6778 Object attributes were developed as part of the ABI for the ARM Architecture.
6779 The file format is documented in @cite{ELF for the ARM Architecture}.
6782 * GNU Object Attributes:: @sc{gnu} Object Attributes
6783 * Defining New Object Attributes:: Defining New Object Attributes
6786 @node GNU Object Attributes
6787 @section @sc{gnu} Object Attributes
6789 The @code{.gnu_attribute} directive records an object attribute
6790 with vendor @samp{gnu}.
6792 Except for @samp{Tag_compatibility}, which has both an integer and a string for
6793 its value, @sc{gnu} attributes have a string value if the tag number is odd and
6794 an integer value if the tag number is even. The second bit (@code{@var{tag} &
6795 2} is set for architecture-independent attributes and clear for
6796 architecture-dependent ones.
6798 @subsection Common @sc{gnu} attributes
6800 These attributes are valid on all architectures.
6803 @item Tag_compatibility (32)
6804 The compatibility attribute takes an integer flag value and a vendor name. If
6805 the flag value is 0, the file is compatible with other toolchains. If it is 1,
6806 then the file is only compatible with the named toolchain. If it is greater
6807 than 1, the file can only be processed by other toolchains under some private
6808 arrangement indicated by the flag value and the vendor name.
6811 @subsection MIPS Attributes
6814 @item Tag_GNU_MIPS_ABI_FP (4)
6815 The floating-point ABI used by this object file. The value will be:
6819 0 for files not affected by the floating-point ABI.
6821 1 for files using the hardware floating-point with a standard double-precision
6824 2 for files using the hardware floating-point ABI with a single-precision FPU.
6826 3 for files using the software floating-point ABI.
6828 4 for files using the hardware floating-point ABI with 64-bit wide
6829 double-precision floating-point registers and 32-bit wide general
6834 @subsection PowerPC Attributes
6837 @item Tag_GNU_Power_ABI_FP (4)
6838 The floating-point ABI used by this object file. The value will be:
6842 0 for files not affected by the floating-point ABI.
6844 1 for files using double-precision hardware floating-point ABI.
6846 2 for files using the software floating-point ABI.
6848 3 for files using single-precision hardware floating-point ABI.
6851 @item Tag_GNU_Power_ABI_Vector (8)
6852 The vector ABI used by this object file. The value will be:
6856 0 for files not affected by the vector ABI.
6858 1 for files using general purpose registers to pass vectors.
6860 2 for files using AltiVec registers to pass vectors.
6862 3 for files using SPE registers to pass vectors.
6866 @node Defining New Object Attributes
6867 @section Defining New Object Attributes
6869 If you want to define a new @sc{gnu} object attribute, here are the places you
6870 will need to modify. New attributes should be discussed on the @samp{binutils}
6875 This manual, which is the official register of attributes.
6877 The header for your architecture @file{include/elf}, to define the tag.
6879 The @file{bfd} support file for your architecture, to merge the attribute
6880 and issue any appropriate link warnings.
6882 Test cases in @file{ld/testsuite} for merging and link warnings.
6884 @file{binutils/readelf.c} to display your attribute.
6886 GCC, if you want the compiler to mark the attribute automatically.
6892 @node Machine Dependencies
6893 @chapter Machine Dependent Features
6895 @cindex machine dependencies
6896 The machine instruction sets are (almost by definition) different on
6897 each machine where @command{@value{AS}} runs. Floating point representations
6898 vary as well, and @command{@value{AS}} often supports a few additional
6899 directives or command-line options for compatibility with other
6900 assemblers on a particular platform. Finally, some versions of
6901 @command{@value{AS}} support special pseudo-instructions for branch
6904 This chapter discusses most of these differences, though it does not
6905 include details on any machine's instruction set. For details on that
6906 subject, see the hardware manufacturer's manual.
6910 * Alpha-Dependent:: Alpha Dependent Features
6913 * ARC-Dependent:: ARC Dependent Features
6916 * ARM-Dependent:: ARM Dependent Features
6919 * AVR-Dependent:: AVR Dependent Features
6922 * Blackfin-Dependent:: Blackfin Dependent Features
6925 * CR16-Dependent:: CR16 Dependent Features
6928 * CRIS-Dependent:: CRIS Dependent Features
6931 * D10V-Dependent:: D10V Dependent Features
6934 * D30V-Dependent:: D30V Dependent Features
6937 * Epiphany-Dependent:: EPIPHANY Dependent Features
6940 * H8/300-Dependent:: Renesas H8/300 Dependent Features
6943 * HPPA-Dependent:: HPPA Dependent Features
6946 * ESA/390-Dependent:: IBM ESA/390 Dependent Features
6949 * i386-Dependent:: Intel 80386 and AMD x86-64 Dependent Features
6952 * i860-Dependent:: Intel 80860 Dependent Features
6955 * i960-Dependent:: Intel 80960 Dependent Features
6958 * IA-64-Dependent:: Intel IA-64 Dependent Features
6961 * IP2K-Dependent:: IP2K Dependent Features
6964 * LM32-Dependent:: LM32 Dependent Features
6967 * M32C-Dependent:: M32C Dependent Features
6970 * M32R-Dependent:: M32R Dependent Features
6973 * M68K-Dependent:: M680x0 Dependent Features
6976 * M68HC11-Dependent:: M68HC11 and 68HC12 Dependent Features
6979 * MicroBlaze-Dependent:: MICROBLAZE Dependent Features
6982 * MIPS-Dependent:: MIPS Dependent Features
6985 * MMIX-Dependent:: MMIX Dependent Features
6988 * MSP430-Dependent:: MSP430 Dependent Features
6991 * NS32K-Dependent:: NS32K Dependent Features
6994 * SH-Dependent:: Renesas / SuperH SH Dependent Features
6995 * SH64-Dependent:: SuperH SH64 Dependent Features
6998 * PDP-11-Dependent:: PDP-11 Dependent Features
7001 * PJ-Dependent:: picoJava Dependent Features
7004 * PPC-Dependent:: PowerPC Dependent Features
7007 * RL78-Dependent:: RL78 Dependent Features
7010 * RX-Dependent:: RX Dependent Features
7013 * S/390-Dependent:: IBM S/390 Dependent Features
7016 * SCORE-Dependent:: SCORE Dependent Features
7019 * Sparc-Dependent:: SPARC Dependent Features
7022 * TIC54X-Dependent:: TI TMS320C54x Dependent Features
7025 * TIC6X-Dependent :: TI TMS320C6x Dependent Features
7028 * TILE-Gx-Dependent :: Tilera TILE-Gx Dependent Features
7031 * TILEPro-Dependent :: Tilera TILEPro Dependent Features
7034 * V850-Dependent:: V850 Dependent Features
7037 * XGATE-Dependent:: XGATE Features
7040 * XSTORMY16-Dependent:: XStormy16 Dependent Features
7043 * Xtensa-Dependent:: Xtensa Dependent Features
7046 * Z80-Dependent:: Z80 Dependent Features
7049 * Z8000-Dependent:: Z8000 Dependent Features
7052 * Vax-Dependent:: VAX Dependent Features
7059 @c The following major nodes are *sections* in the GENERIC version, *chapters*
7060 @c in single-cpu versions. This is mainly achieved by @lowersections. There is a
7061 @c peculiarity: to preserve cross-references, there must be a node called
7062 @c "Machine Dependencies". Hence the conditional nodenames in each
7063 @c major node below. Node defaulting in makeinfo requires adjacency of
7064 @c node and sectioning commands; hence the repetition of @chapter BLAH
7065 @c in both conditional blocks.
7068 @include c-alpha.texi
7084 @include c-bfin.texi
7088 @include c-cr16.texi
7092 @include c-cris.texi
7097 @node Machine Dependencies
7098 @chapter Machine Dependent Features
7100 The machine instruction sets are different on each Renesas chip family,
7101 and there are also some syntax differences among the families. This
7102 chapter describes the specific @command{@value{AS}} features for each
7106 * H8/300-Dependent:: Renesas H8/300 Dependent Features
7107 * SH-Dependent:: Renesas SH Dependent Features
7114 @include c-d10v.texi
7118 @include c-d30v.texi
7122 @include c-epiphany.texi
7126 @include c-h8300.texi
7130 @include c-hppa.texi
7134 @include c-i370.texi
7138 @include c-i386.texi
7142 @include c-i860.texi
7146 @include c-i960.texi
7150 @include c-ia64.texi
7154 @include c-ip2k.texi
7158 @include c-lm32.texi
7162 @include c-m32c.texi
7166 @include c-m32r.texi
7170 @include c-m68k.texi
7174 @include c-m68hc11.texi
7178 @include c-microblaze.texi
7182 @include c-mips.texi
7186 @include c-mmix.texi
7190 @include c-msp430.texi
7194 @include c-ns32k.texi
7198 @include c-pdp11.texi
7210 @include c-rl78.texi
7218 @include c-s390.texi
7222 @include c-score.texi
7227 @include c-sh64.texi
7231 @include c-sparc.texi
7235 @include c-tic54x.texi
7239 @include c-tic6x.texi
7243 @include c-tilegx.texi
7247 @include c-tilepro.texi
7263 @include c-v850.texi
7267 @include c-xgate.texi
7271 @include c-xstormy16.texi
7275 @include c-xtensa.texi
7279 @c reverse effect of @down at top of generic Machine-Dep chapter
7283 @node Reporting Bugs
7284 @chapter Reporting Bugs
7285 @cindex bugs in assembler
7286 @cindex reporting bugs in assembler
7288 Your bug reports play an essential role in making @command{@value{AS}} reliable.
7290 Reporting a bug may help you by bringing a solution to your problem, or it may
7291 not. But in any case the principal function of a bug report is to help the
7292 entire community by making the next version of @command{@value{AS}} work better.
7293 Bug reports are your contribution to the maintenance of @command{@value{AS}}.
7295 In order for a bug report to serve its purpose, you must include the
7296 information that enables us to fix the bug.
7299 * Bug Criteria:: Have you found a bug?
7300 * Bug Reporting:: How to report bugs
7304 @section Have You Found a Bug?
7305 @cindex bug criteria
7307 If you are not sure whether you have found a bug, here are some guidelines:
7310 @cindex fatal signal
7311 @cindex assembler crash
7312 @cindex crash of assembler
7314 If the assembler gets a fatal signal, for any input whatever, that is a
7315 @command{@value{AS}} bug. Reliable assemblers never crash.
7317 @cindex error on valid input
7319 If @command{@value{AS}} produces an error message for valid input, that is a bug.
7321 @cindex invalid input
7323 If @command{@value{AS}} does not produce an error message for invalid input, that
7324 is a bug. However, you should note that your idea of ``invalid input'' might
7325 be our idea of ``an extension'' or ``support for traditional practice''.
7328 If you are an experienced user of assemblers, your suggestions for improvement
7329 of @command{@value{AS}} are welcome in any case.
7333 @section How to Report Bugs
7335 @cindex assembler bugs, reporting
7337 A number of companies and individuals offer support for @sc{gnu} products. If
7338 you obtained @command{@value{AS}} from a support organization, we recommend you
7339 contact that organization first.
7341 You can find contact information for many support companies and
7342 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
7346 In any event, we also recommend that you send bug reports for @command{@value{AS}}
7350 The fundamental principle of reporting bugs usefully is this:
7351 @strong{report all the facts}. If you are not sure whether to state a
7352 fact or leave it out, state it!
7354 Often people omit facts because they think they know what causes the problem
7355 and assume that some details do not matter. Thus, you might assume that the
7356 name of a symbol you use in an example does not matter. Well, probably it does
7357 not, but one cannot be sure. Perhaps the bug is a stray memory reference which
7358 happens to fetch from the location where that name is stored in memory;
7359 perhaps, if the name were different, the contents of that location would fool
7360 the assembler into doing the right thing despite the bug. Play it safe and
7361 give a specific, complete example. That is the easiest thing for you to do,
7362 and the most helpful.
7364 Keep in mind that the purpose of a bug report is to enable us to fix the bug if
7365 it is new to us. Therefore, always write your bug reports on the assumption
7366 that the bug has not been reported previously.
7368 Sometimes people give a few sketchy facts and ask, ``Does this ring a
7369 bell?'' This cannot help us fix a bug, so it is basically useless. We
7370 respond by asking for enough details to enable us to investigate.
7371 You might as well expedite matters by sending them to begin with.
7373 To enable us to fix the bug, you should include all these things:
7377 The version of @command{@value{AS}}. @command{@value{AS}} announces it if you start
7378 it with the @samp{--version} argument.
7380 Without this, we will not know whether there is any point in looking for
7381 the bug in the current version of @command{@value{AS}}.
7384 Any patches you may have applied to the @command{@value{AS}} source.
7387 The type of machine you are using, and the operating system name and
7391 What compiler (and its version) was used to compile @command{@value{AS}}---e.g.
7395 The command arguments you gave the assembler to assemble your example and
7396 observe the bug. To guarantee you will not omit something important, list them
7397 all. A copy of the Makefile (or the output from make) is sufficient.
7399 If we were to try to guess the arguments, we would probably guess wrong
7400 and then we might not encounter the bug.
7403 A complete input file that will reproduce the bug. If the bug is observed when
7404 the assembler is invoked via a compiler, send the assembler source, not the
7405 high level language source. Most compilers will produce the assembler source
7406 when run with the @samp{-S} option. If you are using @code{@value{GCC}}, use
7407 the options @samp{-v --save-temps}; this will save the assembler source in a
7408 file with an extension of @file{.s}, and also show you exactly how
7409 @command{@value{AS}} is being run.
7412 A description of what behavior you observe that you believe is
7413 incorrect. For example, ``It gets a fatal signal.''
7415 Of course, if the bug is that @command{@value{AS}} gets a fatal signal, then we
7416 will certainly notice it. But if the bug is incorrect output, we might not
7417 notice unless it is glaringly wrong. You might as well not give us a chance to
7420 Even if the problem you experience is a fatal signal, you should still say so
7421 explicitly. Suppose something strange is going on, such as, your copy of
7422 @command{@value{AS}} is out of sync, or you have encountered a bug in the C
7423 library on your system. (This has happened!) Your copy might crash and ours
7424 would not. If you told us to expect a crash, then when ours fails to crash, we
7425 would know that the bug was not happening for us. If you had not told us to
7426 expect a crash, then we would not be able to draw any conclusion from our
7430 If you wish to suggest changes to the @command{@value{AS}} source, send us context
7431 diffs, as generated by @code{diff} with the @samp{-u}, @samp{-c}, or @samp{-p}
7432 option. Always send diffs from the old file to the new file. If you even
7433 discuss something in the @command{@value{AS}} source, refer to it by context, not
7436 The line numbers in our development sources will not match those in your
7437 sources. Your line numbers would convey no useful information to us.
7440 Here are some things that are not necessary:
7444 A description of the envelope of the bug.
7446 Often people who encounter a bug spend a lot of time investigating
7447 which changes to the input file will make the bug go away and which
7448 changes will not affect it.
7450 This is often time consuming and not very useful, because the way we
7451 will find the bug is by running a single example under the debugger
7452 with breakpoints, not by pure deduction from a series of examples.
7453 We recommend that you save your time for something else.
7455 Of course, if you can find a simpler example to report @emph{instead}
7456 of the original one, that is a convenience for us. Errors in the
7457 output will be easier to spot, running under the debugger will take
7458 less time, and so on.
7460 However, simplification is not vital; if you do not want to do this,
7461 report the bug anyway and send us the entire test case you used.
7464 A patch for the bug.
7466 A patch for the bug does help us if it is a good one. But do not omit
7467 the necessary information, such as the test case, on the assumption that
7468 a patch is all we need. We might see problems with your patch and decide
7469 to fix the problem another way, or we might not understand it at all.
7471 Sometimes with a program as complicated as @command{@value{AS}} it is very hard to
7472 construct an example that will make the program follow a certain path through
7473 the code. If you do not send us the example, we will not be able to construct
7474 one, so we will not be able to verify that the bug is fixed.
7476 And if we cannot understand what bug you are trying to fix, or why your
7477 patch should be an improvement, we will not install it. A test case will
7478 help us to understand.
7481 A guess about what the bug is or what it depends on.
7483 Such guesses are usually wrong. Even we cannot guess right about such
7484 things without first using the debugger to find the facts.
7487 @node Acknowledgements
7488 @chapter Acknowledgements
7490 If you have contributed to GAS and your name isn't listed here,
7491 it is not meant as a slight. We just don't know about it. Send mail to the
7492 maintainer, and we'll correct the situation. Currently
7494 the maintainer is Ken Raeburn (email address @code{raeburn@@cygnus.com}).
7496 Dean Elsner wrote the original @sc{gnu} assembler for the VAX.@footnote{Any
7499 Jay Fenlason maintained GAS for a while, adding support for GDB-specific debug
7500 information and the 68k series machines, most of the preprocessing pass, and
7501 extensive changes in @file{messages.c}, @file{input-file.c}, @file{write.c}.
7503 K. Richard Pixley maintained GAS for a while, adding various enhancements and
7504 many bug fixes, including merging support for several processors, breaking GAS
7505 up to handle multiple object file format back ends (including heavy rewrite,
7506 testing, an integration of the coff and b.out back ends), adding configuration
7507 including heavy testing and verification of cross assemblers and file splits
7508 and renaming, converted GAS to strictly ANSI C including full prototypes, added
7509 support for m680[34]0 and cpu32, did considerable work on i960 including a COFF
7510 port (including considerable amounts of reverse engineering), a SPARC opcode
7511 file rewrite, DECstation, rs6000, and hp300hpux host ports, updated ``know''
7512 assertions and made them work, much other reorganization, cleanup, and lint.
7514 Ken Raeburn wrote the high-level BFD interface code to replace most of the code
7515 in format-specific I/O modules.
7517 The original VMS support was contributed by David L. Kashtan. Eric Youngdale
7518 has done much work with it since.
7520 The Intel 80386 machine description was written by Eliot Dresselhaus.
7522 Minh Tran-Le at IntelliCorp contributed some AIX 386 support.
7524 The Motorola 88k machine description was contributed by Devon Bowen of Buffalo
7525 University and Torbjorn Granlund of the Swedish Institute of Computer Science.
7527 Keith Knowles at the Open Software Foundation wrote the original MIPS back end
7528 (@file{tc-mips.c}, @file{tc-mips.h}), and contributed Rose format support
7529 (which hasn't been merged in yet). Ralph Campbell worked with the MIPS code to
7530 support a.out format.
7532 Support for the Zilog Z8k and Renesas H8/300 processors (tc-z8k,
7533 tc-h8300), and IEEE 695 object file format (obj-ieee), was written by
7534 Steve Chamberlain of Cygnus Support. Steve also modified the COFF back end to
7535 use BFD for some low-level operations, for use with the H8/300 and AMD 29k
7538 John Gilmore built the AMD 29000 support, added @code{.include} support, and
7539 simplified the configuration of which versions accept which directives. He
7540 updated the 68k machine description so that Motorola's opcodes always produced
7541 fixed-size instructions (e.g., @code{jsr}), while synthetic instructions
7542 remained shrinkable (@code{jbsr}). John fixed many bugs, including true tested
7543 cross-compilation support, and one bug in relaxation that took a week and
7544 required the proverbial one-bit fix.
7546 Ian Lance Taylor of Cygnus Support merged the Motorola and MIT syntax for the
7547 68k, completed support for some COFF targets (68k, i386 SVR3, and SCO Unix),
7548 added support for MIPS ECOFF and ELF targets, wrote the initial RS/6000 and
7549 PowerPC assembler, and made a few other minor patches.
7551 Steve Chamberlain made GAS able to generate listings.
7553 Hewlett-Packard contributed support for the HP9000/300.
7555 Jeff Law wrote GAS and BFD support for the native HPPA object format (SOM)
7556 along with a fairly extensive HPPA testsuite (for both SOM and ELF object
7557 formats). This work was supported by both the Center for Software Science at
7558 the University of Utah and Cygnus Support.
7560 Support for ELF format files has been worked on by Mark Eichin of Cygnus
7561 Support (original, incomplete implementation for SPARC), Pete Hoogenboom and
7562 Jeff Law at the University of Utah (HPPA mainly), Michael Meissner of the Open
7563 Software Foundation (i386 mainly), and Ken Raeburn of Cygnus Support (sparc,
7564 and some initial 64-bit support).
7566 Linas Vepstas added GAS support for the ESA/390 ``IBM 370'' architecture.
7568 Richard Henderson rewrote the Alpha assembler. Klaus Kaempf wrote GAS and BFD
7569 support for openVMS/Alpha.
7571 Timothy Wall, Michael Hayes, and Greg Smart contributed to the various tic*
7574 David Heine, Sterling Augustine, Bob Wilson and John Ruttenberg from Tensilica,
7575 Inc.@: added support for Xtensa processors.
7577 Several engineers at Cygnus Support have also provided many small bug fixes and
7578 configuration enhancements.
7580 Jon Beniston added support for the Lattice Mico32 architecture.
7582 Many others have contributed large or small bugfixes and enhancements. If
7583 you have contributed significant work and are not mentioned on this list, and
7584 want to be, let us know. Some of the history has been lost; we are not
7585 intentionally leaving anyone out.
7587 @node GNU Free Documentation License
7588 @appendix GNU Free Documentation License
7592 @unnumbered AS Index