1 \input texinfo @c -*-Texinfo-*-
2 @c Copyright 1991-2013 Free Software Foundation, Inc.
3 @c UPDATE!! On future updates--
4 @c (1) check for new machine-dep cmdline options in
5 @c md_parse_option definitions in config/tc-*.c
6 @c (2) for platform-specific directives, examine md_pseudo_op
8 @c (3) for object-format specific directives, examine obj_pseudo_op
10 @c (4) portable directives in potable[] in read.c
14 @macro gcctabopt{body}
17 @c defaults, config file may override:
22 @include asconfig.texi
27 @c common OR combinations of conditions
53 @set abnormal-separator
57 @settitle Using @value{AS}
60 @settitle Using @value{AS} (@value{TARGET})
62 @setchapternewpage odd
67 @c WARE! Some of the machine-dependent sections contain tables of machine
68 @c instructions. Except in multi-column format, these tables look silly.
69 @c Unfortunately, Texinfo doesn't have a general-purpose multi-col format, so
70 @c the multi-col format is faked within @example sections.
72 @c Again unfortunately, the natural size that fits on a page, for these tables,
73 @c is different depending on whether or not smallbook is turned on.
74 @c This matters, because of order: text flow switches columns at each page
77 @c The format faked in this source works reasonably well for smallbook,
78 @c not well for the default large-page format. This manual expects that if you
79 @c turn on @smallbook, you will also uncomment the "@set SMALL" to enable the
80 @c tables in question. You can turn on one without the other at your
81 @c discretion, of course.
84 @c the insn tables look just as silly in info files regardless of smallbook,
85 @c might as well show 'em anyways.
89 @dircategory Software development
91 * As: (as). The GNU assembler.
92 * Gas: (as). The GNU assembler.
100 This file documents the GNU Assembler "@value{AS}".
102 @c man begin COPYRIGHT
103 Copyright @copyright{} 1991-2013 Free Software Foundation, Inc.
105 Permission is granted to copy, distribute and/or modify this document
106 under the terms of the GNU Free Documentation License, Version 1.3
107 or any later version published by the Free Software Foundation;
108 with no Invariant Sections, with no Front-Cover Texts, and with no
109 Back-Cover Texts. A copy of the license is included in the
110 section entitled ``GNU Free Documentation License''.
116 @title Using @value{AS}
117 @subtitle The @sc{gnu} Assembler
119 @subtitle for the @value{TARGET} family
121 @ifset VERSION_PACKAGE
123 @subtitle @value{VERSION_PACKAGE}
126 @subtitle Version @value{VERSION}
129 The Free Software Foundation Inc.@: thanks The Nice Computer
130 Company of Australia for loaning Dean Elsner to write the
131 first (Vax) version of @command{as} for Project @sc{gnu}.
132 The proprietors, management and staff of TNCCA thank FSF for
133 distracting the boss while they got some work
136 @author Dean Elsner, Jay Fenlason & friends
140 \hfill {\it Using {\tt @value{AS}}}\par
141 \hfill Edited by Cygnus Support\par
143 %"boxit" macro for figures:
144 %Modified from Knuth's ``boxit'' macro from TeXbook (answer to exercise 21.3)
145 \gdef\boxit#1#2{\vbox{\hrule\hbox{\vrule\kern3pt
146 \vbox{\parindent=0pt\parskip=0pt\hsize=#1\kern3pt\strut\hfil
147 #2\hfil\strut\kern3pt}\kern3pt\vrule}\hrule}}%box with visible outline
148 \gdef\ibox#1#2{\hbox to #1{#2\hfil}\kern8pt}% invisible box
151 @vskip 0pt plus 1filll
152 Copyright @copyright{} 1991-2013 Free Software Foundation, Inc.
154 Permission is granted to copy, distribute and/or modify this document
155 under the terms of the GNU Free Documentation License, Version 1.3
156 or any later version published by the Free Software Foundation;
157 with no Invariant Sections, with no Front-Cover Texts, and with no
158 Back-Cover Texts. A copy of the license is included in the
159 section entitled ``GNU Free Documentation License''.
166 @top Using @value{AS}
168 This file is a user guide to the @sc{gnu} assembler @command{@value{AS}}
169 @ifset VERSION_PACKAGE
170 @value{VERSION_PACKAGE}
172 version @value{VERSION}.
174 This version of the file describes @command{@value{AS}} configured to generate
175 code for @value{TARGET} architectures.
178 This document is distributed under the terms of the GNU Free
179 Documentation License. A copy of the license is included in the
180 section entitled ``GNU Free Documentation License''.
183 * Overview:: Overview
184 * Invoking:: Command-Line Options
186 * Sections:: Sections and Relocation
188 * Expressions:: Expressions
189 * Pseudo Ops:: Assembler Directives
191 * Object Attributes:: Object Attributes
193 * Machine Dependencies:: Machine Dependent Features
194 * Reporting Bugs:: Reporting Bugs
195 * Acknowledgements:: Who Did What
196 * GNU Free Documentation License:: GNU Free Documentation License
197 * AS Index:: AS Index
204 This manual is a user guide to the @sc{gnu} assembler @command{@value{AS}}.
206 This version of the manual describes @command{@value{AS}} configured to generate
207 code for @value{TARGET} architectures.
211 @cindex invocation summary
212 @cindex option summary
213 @cindex summary of options
214 Here is a brief summary of how to invoke @command{@value{AS}}. For details,
215 see @ref{Invoking,,Command-Line Options}.
217 @c man title AS the portable GNU assembler.
221 gcc(1), ld(1), and the Info entries for @file{binutils} and @file{ld}.
225 @c We don't use deffn and friends for the following because they seem
226 @c to be limited to one line for the header.
228 @c man begin SYNOPSIS
229 @value{AS} [@b{-a}[@b{cdghlns}][=@var{file}]] [@b{--alternate}] [@b{-D}]
230 [@b{--compress-debug-sections}] [@b{--nocompress-debug-sections}]
231 [@b{--debug-prefix-map} @var{old}=@var{new}]
232 [@b{--defsym} @var{sym}=@var{val}] [@b{-f}] [@b{-g}] [@b{--gstabs}]
233 [@b{--gstabs+}] [@b{--gdwarf-2}] [@b{--gdwarf-sections}]
234 [@b{--help}] [@b{-I} @var{dir}] [@b{-J}]
235 [@b{-K}] [@b{-L}] [@b{--listing-lhs-width}=@var{NUM}]
236 [@b{--listing-lhs-width2}=@var{NUM}] [@b{--listing-rhs-width}=@var{NUM}]
237 [@b{--listing-cont-lines}=@var{NUM}] [@b{--keep-locals}] [@b{-o}
238 @var{objfile}] [@b{-R}] [@b{--reduce-memory-overheads}] [@b{--statistics}]
239 [@b{-v}] [@b{-version}] [@b{--version}] [@b{-W}] [@b{--warn}]
240 [@b{--fatal-warnings}] [@b{-w}] [@b{-x}] [@b{-Z}] [@b{@@@var{FILE}}]
241 [@b{--size-check=[error|warning]}]
242 [@b{--target-help}] [@var{target-options}]
243 [@b{--}|@var{files} @dots{}]
245 @c Target dependent options are listed below. Keep the list sorted.
246 @c Add an empty line for separation.
249 @emph{Target AArch64 options:}
251 [@b{-mabi}=@var{ABI}]
255 @emph{Target Alpha options:}
257 [@b{-mdebug} | @b{-no-mdebug}]
258 [@b{-replace} | @b{-noreplace}]
259 [@b{-relax}] [@b{-g}] [@b{-G@var{size}}]
260 [@b{-F}] [@b{-32addr}]
264 @emph{Target ARC options:}
270 @emph{Target ARM options:}
271 @c Don't document the deprecated options
272 [@b{-mcpu}=@var{processor}[+@var{extension}@dots{}]]
273 [@b{-march}=@var{architecture}[+@var{extension}@dots{}]]
274 [@b{-mfpu}=@var{floating-point-format}]
275 [@b{-mfloat-abi}=@var{abi}]
276 [@b{-meabi}=@var{ver}]
279 [@b{-mapcs-32}|@b{-mapcs-26}|@b{-mapcs-float}|
280 @b{-mapcs-reentrant}]
281 [@b{-mthumb-interwork}] [@b{-k}]
285 @emph{Target Blackfin options:}
286 [@b{-mcpu}=@var{processor}[-@var{sirevision}]]
293 @emph{Target CRIS options:}
294 [@b{--underscore} | @b{--no-underscore}]
296 [@b{--emulation=criself} | @b{--emulation=crisaout}]
297 [@b{--march=v0_v10} | @b{--march=v10} | @b{--march=v32} | @b{--march=common_v10_v32}]
298 @c Deprecated -- deliberately not documented.
303 @emph{Target D10V options:}
308 @emph{Target D30V options:}
309 [@b{-O}|@b{-n}|@b{-N}]
313 @emph{Target EPIPHANY options:}
314 [@b{-mepiphany}|@b{-mepiphany16}]
318 @emph{Target H8/300 options:}
322 @c HPPA has no machine-dependent assembler options (yet).
326 @emph{Target i386 options:}
327 [@b{--32}|@b{--x32}|@b{--64}] [@b{-n}]
328 [@b{-march}=@var{CPU}[+@var{EXTENSION}@dots{}]] [@b{-mtune}=@var{CPU}]
332 @emph{Target i960 options:}
333 @c see md_parse_option in tc-i960.c
334 [@b{-ACA}|@b{-ACA_A}|@b{-ACB}|@b{-ACC}|@b{-AKA}|@b{-AKB}|
336 [@b{-b}] [@b{-no-relax}]
340 @emph{Target IA-64 options:}
341 [@b{-mconstant-gp}|@b{-mauto-pic}]
342 [@b{-milp32}|@b{-milp64}|@b{-mlp64}|@b{-mp64}]
344 [@b{-mtune=itanium1}|@b{-mtune=itanium2}]
345 [@b{-munwind-check=warning}|@b{-munwind-check=error}]
346 [@b{-mhint.b=ok}|@b{-mhint.b=warning}|@b{-mhint.b=error}]
347 [@b{-x}|@b{-xexplicit}] [@b{-xauto}] [@b{-xdebug}]
351 @emph{Target IP2K options:}
352 [@b{-mip2022}|@b{-mip2022ext}]
356 @emph{Target M32C options:}
357 [@b{-m32c}|@b{-m16c}] [-relax] [-h-tick-hex]
361 @emph{Target M32R options:}
362 [@b{--m32rx}|@b{--[no-]warn-explicit-parallel-conflicts}|
367 @emph{Target M680X0 options:}
368 [@b{-l}] [@b{-m68000}|@b{-m68010}|@b{-m68020}|@dots{}]
372 @emph{Target M68HC11 options:}
373 [@b{-m68hc11}|@b{-m68hc12}|@b{-m68hcs12}|@b{-mm9s12x}|@b{-mm9s12xg}]
374 [@b{-mshort}|@b{-mlong}]
375 [@b{-mshort-double}|@b{-mlong-double}]
376 [@b{--force-long-branches}] [@b{--short-branches}]
377 [@b{--strict-direct-mode}] [@b{--print-insn-syntax}]
378 [@b{--print-opcodes}] [@b{--generate-example}]
382 @emph{Target MCORE options:}
383 [@b{-jsri2bsr}] [@b{-sifilter}] [@b{-relax}]
384 [@b{-mcpu=[210|340]}]
388 @emph{Target Meta options:}
389 [@b{-mcpu=@var{cpu}}] [@b{-mfpu=@var{cpu}}] [@b{-mdsp=@var{cpu}}]
392 @emph{Target MICROBLAZE options:}
393 @c MicroBlaze has no machine-dependent assembler options.
397 @emph{Target MIPS options:}
398 [@b{-nocpp}] [@b{-EL}] [@b{-EB}] [@b{-O}[@var{optimization level}]]
399 [@b{-g}[@var{debug level}]] [@b{-G} @var{num}] [@b{-KPIC}] [@b{-call_shared}]
400 [@b{-non_shared}] [@b{-xgot} [@b{-mvxworks-pic}]
401 [@b{-mabi}=@var{ABI}] [@b{-32}] [@b{-n32}] [@b{-64}] [@b{-mfp32}] [@b{-mgp32}]
402 [@b{-march}=@var{CPU}] [@b{-mtune}=@var{CPU}] [@b{-mips1}] [@b{-mips2}]
403 [@b{-mips3}] [@b{-mips4}] [@b{-mips5}] [@b{-mips32}] [@b{-mips32r2}]
404 [@b{-mips64}] [@b{-mips64r2}]
405 [@b{-construct-floats}] [@b{-no-construct-floats}]
406 [@b{-mnan=@var{encoding}}]
407 [@b{-trap}] [@b{-no-break}] [@b{-break}] [@b{-no-trap}]
408 [@b{-mips16}] [@b{-no-mips16}]
409 [@b{-mmicromips}] [@b{-mno-micromips}]
410 [@b{-msmartmips}] [@b{-mno-smartmips}]
411 [@b{-mips3d}] [@b{-no-mips3d}]
412 [@b{-mdmx}] [@b{-no-mdmx}]
413 [@b{-mdsp}] [@b{-mno-dsp}]
414 [@b{-mdspr2}] [@b{-mno-dspr2}]
415 [@b{-mmsa}] [@b{-mno-msa}]
416 [@b{-mmt}] [@b{-mno-mt}]
417 [@b{-mmcu}] [@b{-mno-mcu}]
418 [@b{-minsn32}] [@b{-mno-insn32}]
419 [@b{-mfix7000}] [@b{-mno-fix7000}]
420 [@b{-mfix-rm7000}] [@b{-mno-fix-rm7000}]
421 [@b{-mfix-vr4120}] [@b{-mno-fix-vr4120}]
422 [@b{-mfix-vr4130}] [@b{-mno-fix-vr4130}]
423 [@b{-mdebug}] [@b{-no-mdebug}]
424 [@b{-mpdr}] [@b{-mno-pdr}]
428 @emph{Target MMIX options:}
429 [@b{--fixed-special-register-names}] [@b{--globalize-symbols}]
430 [@b{--gnu-syntax}] [@b{--relax}] [@b{--no-predefined-symbols}]
431 [@b{--no-expand}] [@b{--no-merge-gregs}] [@b{-x}]
432 [@b{--linker-allocated-gregs}]
436 @emph{Target Nios II options:}
437 [@b{-relax-all}] [@b{-relax-section}] [@b{-no-relax}]
442 @emph{Target PDP11 options:}
443 [@b{-mpic}|@b{-mno-pic}] [@b{-mall}] [@b{-mno-extensions}]
444 [@b{-m}@var{extension}|@b{-mno-}@var{extension}]
445 [@b{-m}@var{cpu}] [@b{-m}@var{machine}]
449 @emph{Target picoJava options:}
454 @emph{Target PowerPC options:}
456 [@b{-mpwrx}|@b{-mpwr2}|@b{-mpwr}|@b{-m601}|@b{-mppc}|@b{-mppc32}|@b{-m603}|@b{-m604}|@b{-m403}|@b{-m405}|
457 @b{-m440}|@b{-m464}|@b{-m476}|@b{-m7400}|@b{-m7410}|@b{-m7450}|@b{-m7455}|@b{-m750cl}|@b{-mppc64}|
458 @b{-m620}|@b{-me500}|@b{-e500x2}|@b{-me500mc}|@b{-me500mc64}|@b{-me5500}|@b{-me6500}|@b{-mppc64bridge}|
459 @b{-mbooke}|@b{-mpower4}|@b{-mpwr4}|@b{-mpower5}|@b{-mpwr5}|@b{-mpwr5x}|@b{-mpower6}|@b{-mpwr6}|
460 @b{-mpower7}|@b{-mpwr7}|@b{-mpower8}|@b{-mpwr8}|@b{-ma2}|@b{-mcell}|@b{-mspe}|@b{-mtitan}|@b{-me300}|@b{-mcom}]
461 [@b{-many}] [@b{-maltivec}|@b{-mvsx}|@b{-mhtm}|@b{-mvle}]
462 [@b{-mregnames}|@b{-mno-regnames}]
463 [@b{-mrelocatable}|@b{-mrelocatable-lib}|@b{-K PIC}] [@b{-memb}]
464 [@b{-mlittle}|@b{-mlittle-endian}|@b{-le}|@b{-mbig}|@b{-mbig-endian}|@b{-be}]
465 [@b{-msolaris}|@b{-mno-solaris}]
466 [@b{-nops=@var{count}}]
470 @emph{Target RX options:}
471 [@b{-mlittle-endian}|@b{-mbig-endian}]
472 [@b{-m32bit-doubles}|@b{-m64bit-doubles}]
473 [@b{-muse-conventional-section-names}]
474 [@b{-msmall-data-limit}]
477 [@b{-mint-register=@var{number}}]
478 [@b{-mgcc-abi}|@b{-mrx-abi}]
482 @emph{Target s390 options:}
483 [@b{-m31}|@b{-m64}] [@b{-mesa}|@b{-mzarch}] [@b{-march}=@var{CPU}]
484 [@b{-mregnames}|@b{-mno-regnames}]
485 [@b{-mwarn-areg-zero}]
489 @emph{Target SCORE options:}
490 [@b{-EB}][@b{-EL}][@b{-FIXDD}][@b{-NWARN}]
491 [@b{-SCORE5}][@b{-SCORE5U}][@b{-SCORE7}][@b{-SCORE3}]
492 [@b{-march=score7}][@b{-march=score3}]
493 [@b{-USE_R1}][@b{-KPIC}][@b{-O0}][@b{-G} @var{num}][@b{-V}]
497 @emph{Target SPARC options:}
498 @c The order here is important. See c-sparc.texi.
499 [@b{-Av6}|@b{-Av7}|@b{-Av8}|@b{-Asparclet}|@b{-Asparclite}
500 @b{-Av8plus}|@b{-Av8plusa}|@b{-Av9}|@b{-Av9a}]
501 [@b{-xarch=v8plus}|@b{-xarch=v8plusa}] [@b{-bump}]
506 @emph{Target TIC54X options:}
507 [@b{-mcpu=54[123589]}|@b{-mcpu=54[56]lp}] [@b{-mfar-mode}|@b{-mf}]
508 [@b{-merrors-to-file} @var{<filename>}|@b{-me} @var{<filename>}]
513 @emph{Target TIC6X options:}
514 [@b{-march=@var{arch}}] [@b{-mbig-endian}|@b{-mlittle-endian}]
515 [@b{-mdsbt}|@b{-mno-dsbt}] [@b{-mpid=no}|@b{-mpid=near}|@b{-mpid=far}]
516 [@b{-mpic}|@b{-mno-pic}]
520 @emph{Target TILE-Gx options:}
521 [@b{-m32}|@b{-m64}][@b{-EB}][@b{-EL}]
524 @c TILEPro has no machine-dependent assembler options
529 @emph{Target Xtensa options:}
530 [@b{--[no-]text-section-literals}] [@b{--[no-]absolute-literals}]
531 [@b{--[no-]target-align}] [@b{--[no-]longcalls}]
532 [@b{--[no-]transform}]
533 [@b{--rename-section} @var{oldname}=@var{newname}]
538 @emph{Target Z80 options:}
539 [@b{-z80}] [@b{-r800}]
540 [@b{ -ignore-undocumented-instructions}] [@b{-Wnud}]
541 [@b{ -ignore-unportable-instructions}] [@b{-Wnup}]
542 [@b{ -warn-undocumented-instructions}] [@b{-Wud}]
543 [@b{ -warn-unportable-instructions}] [@b{-Wup}]
544 [@b{ -forbid-undocumented-instructions}] [@b{-Fud}]
545 [@b{ -forbid-unportable-instructions}] [@b{-Fup}]
549 @c Z8000 has no machine-dependent assembler options
558 @include at-file.texi
561 Turn on listings, in any of a variety of ways:
565 omit false conditionals
568 omit debugging directives
571 include general information, like @value{AS} version and options passed
574 include high-level source
580 include macro expansions
583 omit forms processing
589 set the name of the listing file
592 You may combine these options; for example, use @samp{-aln} for assembly
593 listing without forms processing. The @samp{=file} option, if used, must be
594 the last one. By itself, @samp{-a} defaults to @samp{-ahls}.
597 Begin in alternate macro mode.
599 @xref{Altmacro,,@code{.altmacro}}.
602 @item --compress-debug-sections
603 Compress DWARF debug sections using zlib. The debug sections are renamed
604 to begin with @samp{.zdebug}, and the resulting object file may not be
605 compatible with older linkers and object file utilities.
607 @item --nocompress-debug-sections
608 Do not compress DWARF debug sections. This is the default.
611 Ignored. This option is accepted for script compatibility with calls to
614 @item --debug-prefix-map @var{old}=@var{new}
615 When assembling files in directory @file{@var{old}}, record debugging
616 information describing them as in @file{@var{new}} instead.
618 @item --defsym @var{sym}=@var{value}
619 Define the symbol @var{sym} to be @var{value} before assembling the input file.
620 @var{value} must be an integer constant. As in C, a leading @samp{0x}
621 indicates a hexadecimal value, and a leading @samp{0} indicates an octal
622 value. The value of the symbol can be overridden inside a source file via the
623 use of a @code{.set} pseudo-op.
626 ``fast''---skip whitespace and comment preprocessing (assume source is
631 Generate debugging information for each assembler source line using whichever
632 debug format is preferred by the target. This currently means either STABS,
636 Generate stabs debugging information for each assembler line. This
637 may help debugging assembler code, if the debugger can handle it.
640 Generate stabs debugging information for each assembler line, with GNU
641 extensions that probably only gdb can handle, and that could make other
642 debuggers crash or refuse to read your program. This
643 may help debugging assembler code. Currently the only GNU extension is
644 the location of the current working directory at assembling time.
647 Generate DWARF2 debugging information for each assembler line. This
648 may help debugging assembler code, if the debugger can handle it. Note---this
649 option is only supported by some targets, not all of them.
651 @item --gdwarf-sections
652 Instead of creating a .debug_line section, create a series of
653 .debug_line.@var{foo} sections where @var{foo} is the name of the
654 corresponding code section. For example a code section called @var{.text.func}
655 will have its dwarf line number information placed into a section called
656 @var{.debug_line.text.func}. If the code section is just called @var{.text}
657 then debug line section will still be called just @var{.debug_line} without any
660 @item --size-check=error
661 @itemx --size-check=warning
662 Issue an error or warning for invalid ELF .size directive.
665 Print a summary of the command line options and exit.
668 Print a summary of all target specific options and exit.
671 Add directory @var{dir} to the search list for @code{.include} directives.
674 Don't warn about signed overflow.
677 @ifclear DIFF-TBL-KLUGE
678 This option is accepted but has no effect on the @value{TARGET} family.
680 @ifset DIFF-TBL-KLUGE
681 Issue warnings when difference tables altered for long displacements.
686 Keep (in the symbol table) local symbols. These symbols start with
687 system-specific local label prefixes, typically @samp{.L} for ELF systems
688 or @samp{L} for traditional a.out systems.
693 @item --listing-lhs-width=@var{number}
694 Set the maximum width, in words, of the output data column for an assembler
695 listing to @var{number}.
697 @item --listing-lhs-width2=@var{number}
698 Set the maximum width, in words, of the output data column for continuation
699 lines in an assembler listing to @var{number}.
701 @item --listing-rhs-width=@var{number}
702 Set the maximum width of an input source line, as displayed in a listing, to
705 @item --listing-cont-lines=@var{number}
706 Set the maximum number of lines printed in a listing for a single line of input
709 @item -o @var{objfile}
710 Name the object-file output from @command{@value{AS}} @var{objfile}.
713 Fold the data section into the text section.
715 @kindex --hash-size=@var{number}
716 Set the default size of GAS's hash tables to a prime number close to
717 @var{number}. Increasing this value can reduce the length of time it takes the
718 assembler to perform its tasks, at the expense of increasing the assembler's
719 memory requirements. Similarly reducing this value can reduce the memory
720 requirements at the expense of speed.
722 @item --reduce-memory-overheads
723 This option reduces GAS's memory requirements, at the expense of making the
724 assembly processes slower. Currently this switch is a synonym for
725 @samp{--hash-size=4051}, but in the future it may have other effects as well.
728 Print the maximum space (in bytes) and total time (in seconds) used by
731 @item --strip-local-absolute
732 Remove local absolute symbols from the outgoing symbol table.
736 Print the @command{as} version.
739 Print the @command{as} version and exit.
743 Suppress warning messages.
745 @item --fatal-warnings
746 Treat warnings as errors.
749 Don't suppress warning messages or treat them as errors.
758 Generate an object file even after errors.
760 @item -- | @var{files} @dots{}
761 Standard input, or source files to assemble.
769 @xref{AArch64 Options}, for the options available when @value{AS} is configured
770 for the 64-bit mode of the ARM Architecture (AArch64).
775 The following options are available when @value{AS} is configured for the
776 64-bit mode of the ARM Architecture (AArch64).
779 @include c-aarch64.texi
780 @c ended inside the included file
788 @xref{Alpha Options}, for the options available when @value{AS} is configured
789 for an Alpha processor.
794 The following options are available when @value{AS} is configured for an Alpha
798 @include c-alpha.texi
799 @c ended inside the included file
806 The following options are available when @value{AS} is configured for
811 This option selects the core processor variant.
813 Select either big-endian (-EB) or little-endian (-EL) output.
818 The following options are available when @value{AS} is configured for the ARM
822 @item -mcpu=@var{processor}[+@var{extension}@dots{}]
823 Specify which ARM processor variant is the target.
824 @item -march=@var{architecture}[+@var{extension}@dots{}]
825 Specify which ARM architecture variant is used by the target.
826 @item -mfpu=@var{floating-point-format}
827 Select which Floating Point architecture is the target.
828 @item -mfloat-abi=@var{abi}
829 Select which floating point ABI is in use.
831 Enable Thumb only instruction decoding.
832 @item -mapcs-32 | -mapcs-26 | -mapcs-float | -mapcs-reentrant
833 Select which procedure calling convention is in use.
835 Select either big-endian (-EB) or little-endian (-EL) output.
836 @item -mthumb-interwork
837 Specify that the code has been generated with interworking between Thumb and
840 Specify that PIC code has been generated.
848 @xref{Blackfin Options}, for the options available when @value{AS} is
849 configured for the Blackfin processor family.
854 The following options are available when @value{AS} is configured for
855 the Blackfin processor family.
859 @c ended inside the included file
866 See the info pages for documentation of the CRIS-specific options.
870 The following options are available when @value{AS} is configured for
873 @cindex D10V optimization
874 @cindex optimization, D10V
876 Optimize output by parallelizing instructions.
881 The following options are available when @value{AS} is configured for a D30V
884 @cindex D30V optimization
885 @cindex optimization, D30V
887 Optimize output by parallelizing instructions.
891 Warn when nops are generated.
893 @cindex D30V nops after 32-bit multiply
895 Warn when a nop after a 32-bit multiply instruction is generated.
901 The following options are available when @value{AS} is configured for the
902 Adapteva EPIPHANY series.
905 @xref{Epiphany Options}, for the options available when @value{AS} is
906 configured for an Epiphany processor.
911 The following options are available when @value{AS} is configured for
912 an Epiphany processor.
915 @include c-epiphany.texi
916 @c ended inside the included file
924 @xref{H8/300 Options}, for the options available when @value{AS} is configured
925 for an H8/300 processor.
930 The following options are available when @value{AS} is configured for an H8/300
934 @include c-h8300.texi
935 @c ended inside the included file
943 @xref{i386-Options}, for the options available when @value{AS} is
944 configured for an i386 processor.
949 The following options are available when @value{AS} is configured for
954 @c ended inside the included file
961 The following options are available when @value{AS} is configured for the
962 Intel 80960 processor.
965 @item -ACA | -ACA_A | -ACB | -ACC | -AKA | -AKB | -AKC | -AMC
966 Specify which variant of the 960 architecture is the target.
969 Add code to collect statistics about branches taken.
972 Do not alter compare-and-branch instructions for long displacements;
979 The following options are available when @value{AS} is configured for the
985 Specifies that the extended IP2022 instructions are allowed.
988 Restores the default behaviour, which restricts the permitted instructions to
989 just the basic IP2022 ones.
995 The following options are available when @value{AS} is configured for the
996 Renesas M32C and M16C processors.
1001 Assemble M32C instructions.
1004 Assemble M16C instructions (the default).
1007 Enable support for link-time relaxations.
1010 Support H'00 style hex constants in addition to 0x00 style.
1016 The following options are available when @value{AS} is configured for the
1017 Renesas M32R (formerly Mitsubishi M32R) series.
1022 Specify which processor in the M32R family is the target. The default
1023 is normally the M32R, but this option changes it to the M32RX.
1025 @item --warn-explicit-parallel-conflicts or --Wp
1026 Produce warning messages when questionable parallel constructs are
1029 @item --no-warn-explicit-parallel-conflicts or --Wnp
1030 Do not produce warning messages when questionable parallel constructs are
1037 The following options are available when @value{AS} is configured for the
1038 Motorola 68000 series.
1043 Shorten references to undefined symbols, to one word instead of two.
1045 @item -m68000 | -m68008 | -m68010 | -m68020 | -m68030
1046 @itemx | -m68040 | -m68060 | -m68302 | -m68331 | -m68332
1047 @itemx | -m68333 | -m68340 | -mcpu32 | -m5200
1048 Specify what processor in the 68000 family is the target. The default
1049 is normally the 68020, but this can be changed at configuration time.
1051 @item -m68881 | -m68882 | -mno-68881 | -mno-68882
1052 The target machine does (or does not) have a floating-point coprocessor.
1053 The default is to assume a coprocessor for 68020, 68030, and cpu32. Although
1054 the basic 68000 is not compatible with the 68881, a combination of the
1055 two can be specified, since it's possible to do emulation of the
1056 coprocessor instructions with the main processor.
1058 @item -m68851 | -mno-68851
1059 The target machine does (or does not) have a memory-management
1060 unit coprocessor. The default is to assume an MMU for 68020 and up.
1068 @xref{Nios II Options}, for the options available when @value{AS} is configured
1069 for an Altera Nios II processor.
1073 @c man begin OPTIONS
1074 The following options are available when @value{AS} is configured for an
1075 Altera Nios II processor.
1077 @c man begin INCLUDE
1078 @include c-nios2.texi
1079 @c ended inside the included file
1085 For details about the PDP-11 machine dependent features options,
1086 see @ref{PDP-11-Options}.
1089 @item -mpic | -mno-pic
1090 Generate position-independent (or position-dependent) code. The
1091 default is @option{-mpic}.
1094 @itemx -mall-extensions
1095 Enable all instruction set extensions. This is the default.
1097 @item -mno-extensions
1098 Disable all instruction set extensions.
1100 @item -m@var{extension} | -mno-@var{extension}
1101 Enable (or disable) a particular instruction set extension.
1104 Enable the instruction set extensions supported by a particular CPU, and
1105 disable all other extensions.
1107 @item -m@var{machine}
1108 Enable the instruction set extensions supported by a particular machine
1109 model, and disable all other extensions.
1115 The following options are available when @value{AS} is configured for
1116 a picoJava processor.
1120 @cindex PJ endianness
1121 @cindex endianness, PJ
1122 @cindex big endian output, PJ
1124 Generate ``big endian'' format output.
1126 @cindex little endian output, PJ
1128 Generate ``little endian'' format output.
1134 The following options are available when @value{AS} is configured for the
1135 Motorola 68HC11 or 68HC12 series.
1139 @item -m68hc11 | -m68hc12 | -m68hcs12 | -mm9s12x | -mm9s12xg
1140 Specify what processor is the target. The default is
1141 defined by the configuration option when building the assembler.
1143 @item --xgate-ramoffset
1144 Instruct the linker to offset RAM addresses from S12X address space into
1145 XGATE address space.
1148 Specify to use the 16-bit integer ABI.
1151 Specify to use the 32-bit integer ABI.
1153 @item -mshort-double
1154 Specify to use the 32-bit double ABI.
1157 Specify to use the 64-bit double ABI.
1159 @item --force-long-branches
1160 Relative branches are turned into absolute ones. This concerns
1161 conditional branches, unconditional branches and branches to a
1164 @item -S | --short-branches
1165 Do not turn relative branches into absolute ones
1166 when the offset is out of range.
1168 @item --strict-direct-mode
1169 Do not turn the direct addressing mode into extended addressing mode
1170 when the instruction does not support direct addressing mode.
1172 @item --print-insn-syntax
1173 Print the syntax of instruction in case of error.
1175 @item --print-opcodes
1176 Print the list of instructions with syntax and then exit.
1178 @item --generate-example
1179 Print an example of instruction for each possible instruction and then exit.
1180 This option is only useful for testing @command{@value{AS}}.
1186 The following options are available when @command{@value{AS}} is configured
1187 for the SPARC architecture:
1190 @item -Av6 | -Av7 | -Av8 | -Asparclet | -Asparclite
1191 @itemx -Av8plus | -Av8plusa | -Av9 | -Av9a
1192 Explicitly select a variant of the SPARC architecture.
1194 @samp{-Av8plus} and @samp{-Av8plusa} select a 32 bit environment.
1195 @samp{-Av9} and @samp{-Av9a} select a 64 bit environment.
1197 @samp{-Av8plusa} and @samp{-Av9a} enable the SPARC V9 instruction set with
1198 UltraSPARC extensions.
1200 @item -xarch=v8plus | -xarch=v8plusa
1201 For compatibility with the Solaris v9 assembler. These options are
1202 equivalent to -Av8plus and -Av8plusa, respectively.
1205 Warn when the assembler switches to another architecture.
1210 The following options are available when @value{AS} is configured for the 'c54x
1215 Enable extended addressing mode. All addresses and relocations will assume
1216 extended addressing (usually 23 bits).
1217 @item -mcpu=@var{CPU_VERSION}
1218 Sets the CPU version being compiled for.
1219 @item -merrors-to-file @var{FILENAME}
1220 Redirect error output to a file, for broken systems which don't support such
1221 behaviour in the shell.
1226 The following options are available when @value{AS} is configured for
1231 This option sets the largest size of an object that can be referenced
1232 implicitly with the @code{gp} register. It is only accepted for targets that
1233 use ECOFF format, such as a DECstation running Ultrix. The default value is 8.
1235 @cindex MIPS endianness
1236 @cindex endianness, MIPS
1237 @cindex big endian output, MIPS
1239 Generate ``big endian'' format output.
1241 @cindex little endian output, MIPS
1243 Generate ``little endian'' format output.
1255 Generate code for a particular MIPS Instruction Set Architecture level.
1256 @samp{-mips1} is an alias for @samp{-march=r3000}, @samp{-mips2} is an
1257 alias for @samp{-march=r6000}, @samp{-mips3} is an alias for
1258 @samp{-march=r4000} and @samp{-mips4} is an alias for @samp{-march=r8000}.
1259 @samp{-mips5}, @samp{-mips32}, @samp{-mips32r2}, @samp{-mips64}, and
1260 @samp{-mips64r2} correspond to generic MIPS V, MIPS32, MIPS32 Release 2,
1261 MIPS64, and MIPS64 Release 2 ISA processors, respectively.
1263 @item -march=@var{cpu}
1264 Generate code for a particular MIPS CPU.
1266 @item -mtune=@var{cpu}
1267 Schedule and tune for a particular MIPS CPU.
1271 Cause nops to be inserted if the read of the destination register
1272 of an mfhi or mflo instruction occurs in the following two instructions.
1275 @itemx -mno-fix-rm7000
1276 Cause nops to be inserted if a dmult or dmultu instruction is
1277 followed by a load instruction.
1281 Cause stabs-style debugging output to go into an ECOFF-style .mdebug
1282 section instead of the standard ELF .stabs sections.
1286 Control generation of @code{.pdr} sections.
1290 The register sizes are normally inferred from the ISA and ABI, but these
1291 flags force a certain group of registers to be treated as 32 bits wide at
1292 all times. @samp{-mgp32} controls the size of general-purpose registers
1293 and @samp{-mfp32} controls the size of floating-point registers.
1297 Generate code for the MIPS 16 processor. This is equivalent to putting
1298 @code{.set mips16} at the start of the assembly file. @samp{-no-mips16}
1299 turns off this option.
1302 @itemx -mno-micromips
1303 Generate code for the microMIPS processor. This is equivalent to putting
1304 @code{.set micromips} at the start of the assembly file. @samp{-mno-micromips}
1305 turns off this option. This is equivalent to putting @code{.set nomicromips}
1306 at the start of the assembly file.
1309 @itemx -mno-smartmips
1310 Enables the SmartMIPS extension to the MIPS32 instruction set. This is
1311 equivalent to putting @code{.set smartmips} at the start of the assembly file.
1312 @samp{-mno-smartmips} turns off this option.
1316 Generate code for the MIPS-3D Application Specific Extension.
1317 This tells the assembler to accept MIPS-3D instructions.
1318 @samp{-no-mips3d} turns off this option.
1322 Generate code for the MDMX Application Specific Extension.
1323 This tells the assembler to accept MDMX instructions.
1324 @samp{-no-mdmx} turns off this option.
1328 Generate code for the DSP Release 1 Application Specific Extension.
1329 This tells the assembler to accept DSP Release 1 instructions.
1330 @samp{-mno-dsp} turns off this option.
1334 Generate code for the DSP Release 2 Application Specific Extension.
1335 This option implies -mdsp.
1336 This tells the assembler to accept DSP Release 2 instructions.
1337 @samp{-mno-dspr2} turns off this option.
1341 Generate code for the MIPS SIMD Architecture Extension.
1342 This tells the assembler to accept MSA instructions.
1343 @samp{-mno-msa} turns off this option.
1347 Generate code for the MT Application Specific Extension.
1348 This tells the assembler to accept MT instructions.
1349 @samp{-mno-mt} turns off this option.
1353 Generate code for the MCU Application Specific Extension.
1354 This tells the assembler to accept MCU instructions.
1355 @samp{-mno-mcu} turns off this option.
1359 Only use 32-bit instruction encodings when generating code for the
1360 microMIPS processor. This option inhibits the use of any 16-bit
1361 instructions. This is equivalent to putting @code{.set insn32} at
1362 the start of the assembly file. @samp{-mno-insn32} turns off this
1363 option. This is equivalent to putting @code{.set noinsn32} at the
1364 start of the assembly file. By default @samp{-mno-insn32} is
1365 selected, allowing all instructions to be used.
1367 @item --construct-floats
1368 @itemx --no-construct-floats
1369 The @samp{--no-construct-floats} option disables the construction of
1370 double width floating point constants by loading the two halves of the
1371 value into the two single width floating point registers that make up
1372 the double width register. By default @samp{--construct-floats} is
1373 selected, allowing construction of these floating point constants.
1375 @item --relax-branch
1376 @itemx --no-relax-branch
1377 The @samp{--relax-branch} option enables the relaxation of out-of-range
1378 branches. By default @samp{--no-relax-branch} is selected, causing any
1379 out-of-range branches to produce an error.
1381 @item -mnan=@var{encoding}
1382 Select between the IEEE 754-2008 (@option{-mnan=2008}) or the legacy
1383 (@option{-mnan=legacy}) NaN encoding format. The latter is the default.
1386 @item --emulation=@var{name}
1387 This option was formerly used to switch between ELF and ECOFF output
1388 on targets like IRIX 5 that supported both. MIPS ECOFF support was
1389 removed in GAS 2.24, so the option now serves little purpose.
1390 It is retained for backwards compatibility.
1392 The available configuration names are: @samp{mipself}, @samp{mipslelf} and
1393 @samp{mipsbelf}. Choosing @samp{mipself} now has no effect, since the output
1394 is always ELF. @samp{mipslelf} and @samp{mipsbelf} select little- and
1395 big-endian output respectively, but @samp{-EL} and @samp{-EB} are now the
1396 preferred options instead.
1399 @command{@value{AS}} ignores this option. It is accepted for compatibility with
1406 Control how to deal with multiplication overflow and division by zero.
1407 @samp{--trap} or @samp{--no-break} (which are synonyms) take a trap exception
1408 (and only work for Instruction Set Architecture level 2 and higher);
1409 @samp{--break} or @samp{--no-trap} (also synonyms, and the default) take a
1413 When this option is used, @command{@value{AS}} will issue a warning every
1414 time it generates a nop instruction from a macro.
1419 The following options are available when @value{AS} is configured for
1425 Enable or disable the JSRI to BSR transformation. By default this is enabled.
1426 The command line option @samp{-nojsri2bsr} can be used to disable it.
1430 Enable or disable the silicon filter behaviour. By default this is disabled.
1431 The default can be overridden by the @samp{-sifilter} command line option.
1434 Alter jump instructions for long displacements.
1436 @item -mcpu=[210|340]
1437 Select the cpu type on the target hardware. This controls which instructions
1441 Assemble for a big endian target.
1444 Assemble for a little endian target.
1453 @xref{Meta Options}, for the options available when @value{AS} is configured
1454 for a Meta processor.
1458 @c man begin OPTIONS
1459 The following options are available when @value{AS} is configured for a
1462 @c man begin INCLUDE
1463 @include c-metag.texi
1464 @c ended inside the included file
1469 @c man begin OPTIONS
1471 See the info pages for documentation of the MMIX-specific options.
1478 @xref{PowerPC-Opts}, for the options available when @value{AS} is configured
1479 for a PowerPC processor.
1483 @c man begin OPTIONS
1484 The following options are available when @value{AS} is configured for a
1487 @c man begin INCLUDE
1489 @c ended inside the included file
1494 @c man begin OPTIONS
1496 See the info pages for documentation of the RX-specific options.
1500 The following options are available when @value{AS} is configured for the s390
1506 Select the word size, either 31/32 bits or 64 bits.
1509 Select the architecture mode, either the Enterprise System
1510 Architecture (esa) or the z/Architecture mode (zarch).
1511 @item -march=@var{processor}
1512 Specify which s390 processor variant is the target, @samp{g6}, @samp{g6},
1513 @samp{z900}, @samp{z990}, @samp{z9-109}, @samp{z9-ec}, @samp{z10},
1514 @samp{z196}, or @samp{zEC12}.
1516 @itemx -mno-regnames
1517 Allow or disallow symbolic names for registers.
1518 @item -mwarn-areg-zero
1519 Warn whenever the operand for a base or index register has been specified
1520 but evaluates to zero.
1528 @xref{TIC6X Options}, for the options available when @value{AS} is configured
1529 for a TMS320C6000 processor.
1533 @c man begin OPTIONS
1534 The following options are available when @value{AS} is configured for a
1535 TMS320C6000 processor.
1537 @c man begin INCLUDE
1538 @include c-tic6x.texi
1539 @c ended inside the included file
1547 @xref{TILE-Gx Options}, for the options available when @value{AS} is configured
1548 for a TILE-Gx processor.
1552 @c man begin OPTIONS
1553 The following options are available when @value{AS} is configured for a TILE-Gx
1556 @c man begin INCLUDE
1557 @include c-tilegx.texi
1558 @c ended inside the included file
1566 @xref{Xtensa Options}, for the options available when @value{AS} is configured
1567 for an Xtensa processor.
1571 @c man begin OPTIONS
1572 The following options are available when @value{AS} is configured for an
1575 @c man begin INCLUDE
1576 @include c-xtensa.texi
1577 @c ended inside the included file
1582 @c man begin OPTIONS
1585 The following options are available when @value{AS} is configured for
1586 a Z80 family processor.
1589 Assemble for Z80 processor.
1591 Assemble for R800 processor.
1592 @item -ignore-undocumented-instructions
1594 Assemble undocumented Z80 instructions that also work on R800 without warning.
1595 @item -ignore-unportable-instructions
1597 Assemble all undocumented Z80 instructions without warning.
1598 @item -warn-undocumented-instructions
1600 Issue a warning for undocumented Z80 instructions that also work on R800.
1601 @item -warn-unportable-instructions
1603 Issue a warning for undocumented Z80 instructions that do not work on R800.
1604 @item -forbid-undocumented-instructions
1606 Treat all undocumented instructions as errors.
1607 @item -forbid-unportable-instructions
1609 Treat undocumented Z80 instructions that do not work on R800 as errors.
1616 * Manual:: Structure of this Manual
1617 * GNU Assembler:: The GNU Assembler
1618 * Object Formats:: Object File Formats
1619 * Command Line:: Command Line
1620 * Input Files:: Input Files
1621 * Object:: Output (Object) File
1622 * Errors:: Error and Warning Messages
1626 @section Structure of this Manual
1628 @cindex manual, structure and purpose
1629 This manual is intended to describe what you need to know to use
1630 @sc{gnu} @command{@value{AS}}. We cover the syntax expected in source files, including
1631 notation for symbols, constants, and expressions; the directives that
1632 @command{@value{AS}} understands; and of course how to invoke @command{@value{AS}}.
1635 We also cover special features in the @value{TARGET}
1636 configuration of @command{@value{AS}}, including assembler directives.
1639 This manual also describes some of the machine-dependent features of
1640 various flavors of the assembler.
1643 @cindex machine instructions (not covered)
1644 On the other hand, this manual is @emph{not} intended as an introduction
1645 to programming in assembly language---let alone programming in general!
1646 In a similar vein, we make no attempt to introduce the machine
1647 architecture; we do @emph{not} describe the instruction set, standard
1648 mnemonics, registers or addressing modes that are standard to a
1649 particular architecture.
1651 You may want to consult the manufacturer's
1652 machine architecture manual for this information.
1656 For information on the H8/300 machine instruction set, see @cite{H8/300
1657 Series Programming Manual}. For the H8/300H, see @cite{H8/300H Series
1658 Programming Manual} (Renesas).
1661 For information on the Renesas (formerly Hitachi) / SuperH SH machine instruction set,
1662 see @cite{SH-Microcomputer User's Manual} (Renesas) or
1663 @cite{SH-4 32-bit CPU Core Architecture} (SuperH) and
1664 @cite{SuperH (SH) 64-Bit RISC Series} (SuperH).
1667 For information on the Z8000 machine instruction set, see @cite{Z8000 CPU Technical Manual}
1671 @c I think this is premature---doc@cygnus.com, 17jan1991
1673 Throughout this manual, we assume that you are running @dfn{GNU},
1674 the portable operating system from the @dfn{Free Software
1675 Foundation, Inc.}. This restricts our attention to certain kinds of
1676 computer (in particular, the kinds of computers that @sc{gnu} can run on);
1677 once this assumption is granted examples and definitions need less
1680 @command{@value{AS}} is part of a team of programs that turn a high-level
1681 human-readable series of instructions into a low-level
1682 computer-readable series of instructions. Different versions of
1683 @command{@value{AS}} are used for different kinds of computer.
1686 @c There used to be a section "Terminology" here, which defined
1687 @c "contents", "byte", "word", and "long". Defining "word" to any
1688 @c particular size is confusing when the .word directive may generate 16
1689 @c bits on one machine and 32 bits on another; in general, for the user
1690 @c version of this manual, none of these terms seem essential to define.
1691 @c They were used very little even in the former draft of the manual;
1692 @c this draft makes an effort to avoid them (except in names of
1696 @section The GNU Assembler
1698 @c man begin DESCRIPTION
1700 @sc{gnu} @command{as} is really a family of assemblers.
1702 This manual describes @command{@value{AS}}, a member of that family which is
1703 configured for the @value{TARGET} architectures.
1705 If you use (or have used) the @sc{gnu} assembler on one architecture, you
1706 should find a fairly similar environment when you use it on another
1707 architecture. Each version has much in common with the others,
1708 including object file formats, most assembler directives (often called
1709 @dfn{pseudo-ops}) and assembler syntax.@refill
1711 @cindex purpose of @sc{gnu} assembler
1712 @command{@value{AS}} is primarily intended to assemble the output of the
1713 @sc{gnu} C compiler @code{@value{GCC}} for use by the linker
1714 @code{@value{LD}}. Nevertheless, we've tried to make @command{@value{AS}}
1715 assemble correctly everything that other assemblers for the same
1716 machine would assemble.
1718 Any exceptions are documented explicitly (@pxref{Machine Dependencies}).
1721 @c This remark should appear in generic version of manual; assumption
1722 @c here is that generic version sets M680x0.
1723 This doesn't mean @command{@value{AS}} always uses the same syntax as another
1724 assembler for the same architecture; for example, we know of several
1725 incompatible versions of 680x0 assembly language syntax.
1730 Unlike older assemblers, @command{@value{AS}} is designed to assemble a source
1731 program in one pass of the source file. This has a subtle impact on the
1732 @kbd{.org} directive (@pxref{Org,,@code{.org}}).
1734 @node Object Formats
1735 @section Object File Formats
1737 @cindex object file format
1738 The @sc{gnu} assembler can be configured to produce several alternative
1739 object file formats. For the most part, this does not affect how you
1740 write assembly language programs; but directives for debugging symbols
1741 are typically different in different file formats. @xref{Symbol
1742 Attributes,,Symbol Attributes}.
1745 For the @value{TARGET} target, @command{@value{AS}} is configured to produce
1746 @value{OBJ-NAME} format object files.
1748 @c The following should exhaust all configs that set MULTI-OBJ, ideally
1750 On the @value{TARGET}, @command{@value{AS}} can be configured to produce either
1751 @code{b.out} or COFF format object files.
1754 On the @value{TARGET}, @command{@value{AS}} can be configured to produce either
1755 SOM or ELF format object files.
1760 @section Command Line
1762 @cindex command line conventions
1764 After the program name @command{@value{AS}}, the command line may contain
1765 options and file names. Options may appear in any order, and may be
1766 before, after, or between file names. The order of file names is
1769 @cindex standard input, as input file
1771 @file{--} (two hyphens) by itself names the standard input file
1772 explicitly, as one of the files for @command{@value{AS}} to assemble.
1774 @cindex options, command line
1775 Except for @samp{--} any command line argument that begins with a
1776 hyphen (@samp{-}) is an option. Each option changes the behavior of
1777 @command{@value{AS}}. No option changes the way another option works. An
1778 option is a @samp{-} followed by one or more letters; the case of
1779 the letter is important. All options are optional.
1781 Some options expect exactly one file name to follow them. The file
1782 name may either immediately follow the option's letter (compatible
1783 with older assemblers) or it may be the next command argument (@sc{gnu}
1784 standard). These two command lines are equivalent:
1787 @value{AS} -o my-object-file.o mumble.s
1788 @value{AS} -omy-object-file.o mumble.s
1792 @section Input Files
1795 @cindex source program
1796 @cindex files, input
1797 We use the phrase @dfn{source program}, abbreviated @dfn{source}, to
1798 describe the program input to one run of @command{@value{AS}}. The program may
1799 be in one or more files; how the source is partitioned into files
1800 doesn't change the meaning of the source.
1802 @c I added "con" prefix to "catenation" just to prove I can overcome my
1803 @c APL training... doc@cygnus.com
1804 The source program is a concatenation of the text in all the files, in the
1807 @c man begin DESCRIPTION
1808 Each time you run @command{@value{AS}} it assembles exactly one source
1809 program. The source program is made up of one or more files.
1810 (The standard input is also a file.)
1812 You give @command{@value{AS}} a command line that has zero or more input file
1813 names. The input files are read (from left file name to right). A
1814 command line argument (in any position) that has no special meaning
1815 is taken to be an input file name.
1817 If you give @command{@value{AS}} no file names it attempts to read one input file
1818 from the @command{@value{AS}} standard input, which is normally your terminal. You
1819 may have to type @key{ctl-D} to tell @command{@value{AS}} there is no more program
1822 Use @samp{--} if you need to explicitly name the standard input file
1823 in your command line.
1825 If the source is empty, @command{@value{AS}} produces a small, empty object
1830 @subheading Filenames and Line-numbers
1832 @cindex input file linenumbers
1833 @cindex line numbers, in input files
1834 There are two ways of locating a line in the input file (or files) and
1835 either may be used in reporting error messages. One way refers to a line
1836 number in a physical file; the other refers to a line number in a
1837 ``logical'' file. @xref{Errors, ,Error and Warning Messages}.
1839 @dfn{Physical files} are those files named in the command line given
1840 to @command{@value{AS}}.
1842 @dfn{Logical files} are simply names declared explicitly by assembler
1843 directives; they bear no relation to physical files. Logical file names help
1844 error messages reflect the original source file, when @command{@value{AS}} source
1845 is itself synthesized from other files. @command{@value{AS}} understands the
1846 @samp{#} directives emitted by the @code{@value{GCC}} preprocessor. See also
1847 @ref{File,,@code{.file}}.
1850 @section Output (Object) File
1856 Every time you run @command{@value{AS}} it produces an output file, which is
1857 your assembly language program translated into numbers. This file
1858 is the object file. Its default name is
1866 @code{b.out} when @command{@value{AS}} is configured for the Intel 80960.
1868 You can give it another name by using the @option{-o} option. Conventionally,
1869 object file names end with @file{.o}. The default name is used for historical
1870 reasons: older assemblers were capable of assembling self-contained programs
1871 directly into a runnable program. (For some formats, this isn't currently
1872 possible, but it can be done for the @code{a.out} format.)
1876 The object file is meant for input to the linker @code{@value{LD}}. It contains
1877 assembled program code, information to help @code{@value{LD}} integrate
1878 the assembled program into a runnable file, and (optionally) symbolic
1879 information for the debugger.
1881 @c link above to some info file(s) like the description of a.out.
1882 @c don't forget to describe @sc{gnu} info as well as Unix lossage.
1885 @section Error and Warning Messages
1887 @c man begin DESCRIPTION
1889 @cindex error messages
1890 @cindex warning messages
1891 @cindex messages from assembler
1892 @command{@value{AS}} may write warnings and error messages to the standard error
1893 file (usually your terminal). This should not happen when a compiler
1894 runs @command{@value{AS}} automatically. Warnings report an assumption made so
1895 that @command{@value{AS}} could keep assembling a flawed program; errors report a
1896 grave problem that stops the assembly.
1900 @cindex format of warning messages
1901 Warning messages have the format
1904 file_name:@b{NNN}:Warning Message Text
1908 @cindex line numbers, in warnings/errors
1909 (where @b{NNN} is a line number). If a logical file name has been given
1910 (@pxref{File,,@code{.file}}) it is used for the filename, otherwise the name of
1911 the current input file is used. If a logical line number was given
1913 (@pxref{Line,,@code{.line}})
1915 then it is used to calculate the number printed,
1916 otherwise the actual line in the current source file is printed. The
1917 message text is intended to be self explanatory (in the grand Unix
1920 @cindex format of error messages
1921 Error messages have the format
1923 file_name:@b{NNN}:FATAL:Error Message Text
1925 The file name and line number are derived as for warning
1926 messages. The actual message text may be rather less explanatory
1927 because many of them aren't supposed to happen.
1930 @chapter Command-Line Options
1932 @cindex options, all versions of assembler
1933 This chapter describes command-line options available in @emph{all}
1934 versions of the @sc{gnu} assembler; see @ref{Machine Dependencies},
1935 for options specific
1937 to the @value{TARGET} target.
1940 to particular machine architectures.
1943 @c man begin DESCRIPTION
1945 If you are invoking @command{@value{AS}} via the @sc{gnu} C compiler,
1946 you can use the @samp{-Wa} option to pass arguments through to the assembler.
1947 The assembler arguments must be separated from each other (and the @samp{-Wa})
1948 by commas. For example:
1951 gcc -c -g -O -Wa,-alh,-L file.c
1955 This passes two options to the assembler: @samp{-alh} (emit a listing to
1956 standard output with high-level and assembly source) and @samp{-L} (retain
1957 local symbols in the symbol table).
1959 Usually you do not need to use this @samp{-Wa} mechanism, since many compiler
1960 command-line options are automatically passed to the assembler by the compiler.
1961 (You can call the @sc{gnu} compiler driver with the @samp{-v} option to see
1962 precisely what options it passes to each compilation pass, including the
1968 * a:: -a[cdghlns] enable listings
1969 * alternate:: --alternate enable alternate macro syntax
1970 * D:: -D for compatibility
1971 * f:: -f to work faster
1972 * I:: -I for .include search path
1973 @ifclear DIFF-TBL-KLUGE
1974 * K:: -K for compatibility
1976 @ifset DIFF-TBL-KLUGE
1977 * K:: -K for difference tables
1980 * L:: -L to retain local symbols
1981 * listing:: --listing-XXX to configure listing output
1982 * M:: -M or --mri to assemble in MRI compatibility mode
1983 * MD:: --MD for dependency tracking
1984 * o:: -o to name the object file
1985 * R:: -R to join data and text sections
1986 * statistics:: --statistics to see statistics about assembly
1987 * traditional-format:: --traditional-format for compatible output
1988 * v:: -v to announce version
1989 * W:: -W, --no-warn, --warn, --fatal-warnings to control warnings
1990 * Z:: -Z to make object file even after errors
1994 @section Enable Listings: @option{-a[cdghlns]}
2004 @cindex listings, enabling
2005 @cindex assembly listings, enabling
2007 These options enable listing output from the assembler. By itself,
2008 @samp{-a} requests high-level, assembly, and symbols listing.
2009 You can use other letters to select specific options for the list:
2010 @samp{-ah} requests a high-level language listing,
2011 @samp{-al} requests an output-program assembly listing, and
2012 @samp{-as} requests a symbol table listing.
2013 High-level listings require that a compiler debugging option like
2014 @samp{-g} be used, and that assembly listings (@samp{-al}) be requested
2017 Use the @samp{-ag} option to print a first section with general assembly
2018 information, like @value{AS} version, switches passed, or time stamp.
2020 Use the @samp{-ac} option to omit false conditionals from a listing. Any lines
2021 which are not assembled because of a false @code{.if} (or @code{.ifdef}, or any
2022 other conditional), or a true @code{.if} followed by an @code{.else}, will be
2023 omitted from the listing.
2025 Use the @samp{-ad} option to omit debugging directives from the
2028 Once you have specified one of these options, you can further control
2029 listing output and its appearance using the directives @code{.list},
2030 @code{.nolist}, @code{.psize}, @code{.eject}, @code{.title}, and
2032 The @samp{-an} option turns off all forms processing.
2033 If you do not request listing output with one of the @samp{-a} options, the
2034 listing-control directives have no effect.
2036 The letters after @samp{-a} may be combined into one option,
2037 @emph{e.g.}, @samp{-aln}.
2039 Note if the assembler source is coming from the standard input (e.g.,
2041 is being created by @code{@value{GCC}} and the @samp{-pipe} command line switch
2042 is being used) then the listing will not contain any comments or preprocessor
2043 directives. This is because the listing code buffers input source lines from
2044 stdin only after they have been preprocessed by the assembler. This reduces
2045 memory usage and makes the code more efficient.
2048 @section @option{--alternate}
2051 Begin in alternate macro mode, see @ref{Altmacro,,@code{.altmacro}}.
2054 @section @option{-D}
2057 This option has no effect whatsoever, but it is accepted to make it more
2058 likely that scripts written for other assemblers also work with
2059 @command{@value{AS}}.
2062 @section Work Faster: @option{-f}
2065 @cindex trusted compiler
2066 @cindex faster processing (@option{-f})
2067 @samp{-f} should only be used when assembling programs written by a
2068 (trusted) compiler. @samp{-f} stops the assembler from doing whitespace
2069 and comment preprocessing on
2070 the input file(s) before assembling them. @xref{Preprocessing,
2074 @emph{Warning:} if you use @samp{-f} when the files actually need to be
2075 preprocessed (if they contain comments, for example), @command{@value{AS}} does
2080 @section @code{.include} Search Path: @option{-I} @var{path}
2082 @kindex -I @var{path}
2083 @cindex paths for @code{.include}
2084 @cindex search path for @code{.include}
2085 @cindex @code{include} directive search path
2086 Use this option to add a @var{path} to the list of directories
2087 @command{@value{AS}} searches for files specified in @code{.include}
2088 directives (@pxref{Include,,@code{.include}}). You may use @option{-I} as
2089 many times as necessary to include a variety of paths. The current
2090 working directory is always searched first; after that, @command{@value{AS}}
2091 searches any @samp{-I} directories in the same order as they were
2092 specified (left to right) on the command line.
2095 @section Difference Tables: @option{-K}
2098 @ifclear DIFF-TBL-KLUGE
2099 On the @value{TARGET} family, this option is allowed, but has no effect. It is
2100 permitted for compatibility with the @sc{gnu} assembler on other platforms,
2101 where it can be used to warn when the assembler alters the machine code
2102 generated for @samp{.word} directives in difference tables. The @value{TARGET}
2103 family does not have the addressing limitations that sometimes lead to this
2104 alteration on other platforms.
2107 @ifset DIFF-TBL-KLUGE
2108 @cindex difference tables, warning
2109 @cindex warning for altered difference tables
2110 @command{@value{AS}} sometimes alters the code emitted for directives of the
2111 form @samp{.word @var{sym1}-@var{sym2}}. @xref{Word,,@code{.word}}.
2112 You can use the @samp{-K} option if you want a warning issued when this
2117 @section Include Local Symbols: @option{-L}
2120 @cindex local symbols, retaining in output
2121 Symbols beginning with system-specific local label prefixes, typically
2122 @samp{.L} for ELF systems or @samp{L} for traditional a.out systems, are
2123 called @dfn{local symbols}. @xref{Symbol Names}. Normally you do not see
2124 such symbols when debugging, because they are intended for the use of
2125 programs (like compilers) that compose assembler programs, not for your
2126 notice. Normally both @command{@value{AS}} and @code{@value{LD}} discard
2127 such symbols, so you do not normally debug with them.
2129 This option tells @command{@value{AS}} to retain those local symbols
2130 in the object file. Usually if you do this you also tell the linker
2131 @code{@value{LD}} to preserve those symbols.
2134 @section Configuring listing output: @option{--listing}
2136 The listing feature of the assembler can be enabled via the command line switch
2137 @samp{-a} (@pxref{a}). This feature combines the input source file(s) with a
2138 hex dump of the corresponding locations in the output object file, and displays
2139 them as a listing file. The format of this listing can be controlled by
2140 directives inside the assembler source (i.e., @code{.list} (@pxref{List}),
2141 @code{.title} (@pxref{Title}), @code{.sbttl} (@pxref{Sbttl}),
2142 @code{.psize} (@pxref{Psize}), and
2143 @code{.eject} (@pxref{Eject}) and also by the following switches:
2146 @item --listing-lhs-width=@samp{number}
2147 @kindex --listing-lhs-width
2148 @cindex Width of first line disassembly output
2149 Sets the maximum width, in words, of the first line of the hex byte dump. This
2150 dump appears on the left hand side of the listing output.
2152 @item --listing-lhs-width2=@samp{number}
2153 @kindex --listing-lhs-width2
2154 @cindex Width of continuation lines of disassembly output
2155 Sets the maximum width, in words, of any further lines of the hex byte dump for
2156 a given input source line. If this value is not specified, it defaults to being
2157 the same as the value specified for @samp{--listing-lhs-width}. If neither
2158 switch is used the default is to one.
2160 @item --listing-rhs-width=@samp{number}
2161 @kindex --listing-rhs-width
2162 @cindex Width of source line output
2163 Sets the maximum width, in characters, of the source line that is displayed
2164 alongside the hex dump. The default value for this parameter is 100. The
2165 source line is displayed on the right hand side of the listing output.
2167 @item --listing-cont-lines=@samp{number}
2168 @kindex --listing-cont-lines
2169 @cindex Maximum number of continuation lines
2170 Sets the maximum number of continuation lines of hex dump that will be
2171 displayed for a given single line of source input. The default value is 4.
2175 @section Assemble in MRI Compatibility Mode: @option{-M}
2178 @cindex MRI compatibility mode
2179 The @option{-M} or @option{--mri} option selects MRI compatibility mode. This
2180 changes the syntax and pseudo-op handling of @command{@value{AS}} to make it
2181 compatible with the @code{ASM68K} or the @code{ASM960} (depending upon the
2182 configured target) assembler from Microtec Research. The exact nature of the
2183 MRI syntax will not be documented here; see the MRI manuals for more
2184 information. Note in particular that the handling of macros and macro
2185 arguments is somewhat different. The purpose of this option is to permit
2186 assembling existing MRI assembler code using @command{@value{AS}}.
2188 The MRI compatibility is not complete. Certain operations of the MRI assembler
2189 depend upon its object file format, and can not be supported using other object
2190 file formats. Supporting these would require enhancing each object file format
2191 individually. These are:
2194 @item global symbols in common section
2196 The m68k MRI assembler supports common sections which are merged by the linker.
2197 Other object file formats do not support this. @command{@value{AS}} handles
2198 common sections by treating them as a single common symbol. It permits local
2199 symbols to be defined within a common section, but it can not support global
2200 symbols, since it has no way to describe them.
2202 @item complex relocations
2204 The MRI assemblers support relocations against a negated section address, and
2205 relocations which combine the start addresses of two or more sections. These
2206 are not support by other object file formats.
2208 @item @code{END} pseudo-op specifying start address
2210 The MRI @code{END} pseudo-op permits the specification of a start address.
2211 This is not supported by other object file formats. The start address may
2212 instead be specified using the @option{-e} option to the linker, or in a linker
2215 @item @code{IDNT}, @code{.ident} and @code{NAME} pseudo-ops
2217 The MRI @code{IDNT}, @code{.ident} and @code{NAME} pseudo-ops assign a module
2218 name to the output file. This is not supported by other object file formats.
2220 @item @code{ORG} pseudo-op
2222 The m68k MRI @code{ORG} pseudo-op begins an absolute section at a given
2223 address. This differs from the usual @command{@value{AS}} @code{.org} pseudo-op,
2224 which changes the location within the current section. Absolute sections are
2225 not supported by other object file formats. The address of a section may be
2226 assigned within a linker script.
2229 There are some other features of the MRI assembler which are not supported by
2230 @command{@value{AS}}, typically either because they are difficult or because they
2231 seem of little consequence. Some of these may be supported in future releases.
2235 @item EBCDIC strings
2237 EBCDIC strings are not supported.
2239 @item packed binary coded decimal
2241 Packed binary coded decimal is not supported. This means that the @code{DC.P}
2242 and @code{DCB.P} pseudo-ops are not supported.
2244 @item @code{FEQU} pseudo-op
2246 The m68k @code{FEQU} pseudo-op is not supported.
2248 @item @code{NOOBJ} pseudo-op
2250 The m68k @code{NOOBJ} pseudo-op is not supported.
2252 @item @code{OPT} branch control options
2254 The m68k @code{OPT} branch control options---@code{B}, @code{BRS}, @code{BRB},
2255 @code{BRL}, and @code{BRW}---are ignored. @command{@value{AS}} automatically
2256 relaxes all branches, whether forward or backward, to an appropriate size, so
2257 these options serve no purpose.
2259 @item @code{OPT} list control options
2261 The following m68k @code{OPT} list control options are ignored: @code{C},
2262 @code{CEX}, @code{CL}, @code{CRE}, @code{E}, @code{G}, @code{I}, @code{M},
2263 @code{MEX}, @code{MC}, @code{MD}, @code{X}.
2265 @item other @code{OPT} options
2267 The following m68k @code{OPT} options are ignored: @code{NEST}, @code{O},
2268 @code{OLD}, @code{OP}, @code{P}, @code{PCO}, @code{PCR}, @code{PCS}, @code{R}.
2270 @item @code{OPT} @code{D} option is default
2272 The m68k @code{OPT} @code{D} option is the default, unlike the MRI assembler.
2273 @code{OPT NOD} may be used to turn it off.
2275 @item @code{XREF} pseudo-op.
2277 The m68k @code{XREF} pseudo-op is ignored.
2279 @item @code{.debug} pseudo-op
2281 The i960 @code{.debug} pseudo-op is not supported.
2283 @item @code{.extended} pseudo-op
2285 The i960 @code{.extended} pseudo-op is not supported.
2287 @item @code{.list} pseudo-op.
2289 The various options of the i960 @code{.list} pseudo-op are not supported.
2291 @item @code{.optimize} pseudo-op
2293 The i960 @code{.optimize} pseudo-op is not supported.
2295 @item @code{.output} pseudo-op
2297 The i960 @code{.output} pseudo-op is not supported.
2299 @item @code{.setreal} pseudo-op
2301 The i960 @code{.setreal} pseudo-op is not supported.
2306 @section Dependency Tracking: @option{--MD}
2309 @cindex dependency tracking
2312 @command{@value{AS}} can generate a dependency file for the file it creates. This
2313 file consists of a single rule suitable for @code{make} describing the
2314 dependencies of the main source file.
2316 The rule is written to the file named in its argument.
2318 This feature is used in the automatic updating of makefiles.
2321 @section Name the Object File: @option{-o}
2324 @cindex naming object file
2325 @cindex object file name
2326 There is always one object file output when you run @command{@value{AS}}. By
2327 default it has the name
2330 @file{a.out} (or @file{b.out}, for Intel 960 targets only).
2344 You use this option (which takes exactly one filename) to give the
2345 object file a different name.
2347 Whatever the object file is called, @command{@value{AS}} overwrites any
2348 existing file of the same name.
2351 @section Join Data and Text Sections: @option{-R}
2354 @cindex data and text sections, joining
2355 @cindex text and data sections, joining
2356 @cindex joining text and data sections
2357 @cindex merging text and data sections
2358 @option{-R} tells @command{@value{AS}} to write the object file as if all
2359 data-section data lives in the text section. This is only done at
2360 the very last moment: your binary data are the same, but data
2361 section parts are relocated differently. The data section part of
2362 your object file is zero bytes long because all its bytes are
2363 appended to the text section. (@xref{Sections,,Sections and Relocation}.)
2365 When you specify @option{-R} it would be possible to generate shorter
2366 address displacements (because we do not have to cross between text and
2367 data section). We refrain from doing this simply for compatibility with
2368 older versions of @command{@value{AS}}. In future, @option{-R} may work this way.
2371 When @command{@value{AS}} is configured for COFF or ELF output,
2372 this option is only useful if you use sections named @samp{.text} and
2377 @option{-R} is not supported for any of the HPPA targets. Using
2378 @option{-R} generates a warning from @command{@value{AS}}.
2382 @section Display Assembly Statistics: @option{--statistics}
2384 @kindex --statistics
2385 @cindex statistics, about assembly
2386 @cindex time, total for assembly
2387 @cindex space used, maximum for assembly
2388 Use @samp{--statistics} to display two statistics about the resources used by
2389 @command{@value{AS}}: the maximum amount of space allocated during the assembly
2390 (in bytes), and the total execution time taken for the assembly (in @sc{cpu}
2393 @node traditional-format
2394 @section Compatible Output: @option{--traditional-format}
2396 @kindex --traditional-format
2397 For some targets, the output of @command{@value{AS}} is different in some ways
2398 from the output of some existing assembler. This switch requests
2399 @command{@value{AS}} to use the traditional format instead.
2401 For example, it disables the exception frame optimizations which
2402 @command{@value{AS}} normally does by default on @code{@value{GCC}} output.
2405 @section Announce Version: @option{-v}
2409 @cindex assembler version
2410 @cindex version of assembler
2411 You can find out what version of as is running by including the
2412 option @samp{-v} (which you can also spell as @samp{-version}) on the
2416 @section Control Warnings: @option{-W}, @option{--warn}, @option{--no-warn}, @option{--fatal-warnings}
2418 @command{@value{AS}} should never give a warning or error message when
2419 assembling compiler output. But programs written by people often
2420 cause @command{@value{AS}} to give a warning that a particular assumption was
2421 made. All such warnings are directed to the standard error file.
2425 @cindex suppressing warnings
2426 @cindex warnings, suppressing
2427 If you use the @option{-W} and @option{--no-warn} options, no warnings are issued.
2428 This only affects the warning messages: it does not change any particular of
2429 how @command{@value{AS}} assembles your file. Errors, which stop the assembly,
2432 @kindex --fatal-warnings
2433 @cindex errors, caused by warnings
2434 @cindex warnings, causing error
2435 If you use the @option{--fatal-warnings} option, @command{@value{AS}} considers
2436 files that generate warnings to be in error.
2439 @cindex warnings, switching on
2440 You can switch these options off again by specifying @option{--warn}, which
2441 causes warnings to be output as usual.
2444 @section Generate Object File in Spite of Errors: @option{-Z}
2445 @cindex object file, after errors
2446 @cindex errors, continuing after
2447 After an error message, @command{@value{AS}} normally produces no output. If for
2448 some reason you are interested in object file output even after
2449 @command{@value{AS}} gives an error message on your program, use the @samp{-Z}
2450 option. If there are any errors, @command{@value{AS}} continues anyways, and
2451 writes an object file after a final warning message of the form @samp{@var{n}
2452 errors, @var{m} warnings, generating bad object file.}
2457 @cindex machine-independent syntax
2458 @cindex syntax, machine-independent
2459 This chapter describes the machine-independent syntax allowed in a
2460 source file. @command{@value{AS}} syntax is similar to what many other
2461 assemblers use; it is inspired by the BSD 4.2
2466 assembler, except that @command{@value{AS}} does not assemble Vax bit-fields.
2470 * Preprocessing:: Preprocessing
2471 * Whitespace:: Whitespace
2472 * Comments:: Comments
2473 * Symbol Intro:: Symbols
2474 * Statements:: Statements
2475 * Constants:: Constants
2479 @section Preprocessing
2481 @cindex preprocessing
2482 The @command{@value{AS}} internal preprocessor:
2484 @cindex whitespace, removed by preprocessor
2486 adjusts and removes extra whitespace. It leaves one space or tab before
2487 the keywords on a line, and turns any other whitespace on the line into
2490 @cindex comments, removed by preprocessor
2492 removes all comments, replacing them with a single space, or an
2493 appropriate number of newlines.
2495 @cindex constants, converted by preprocessor
2497 converts character constants into the appropriate numeric values.
2500 It does not do macro processing, include file handling, or
2501 anything else you may get from your C compiler's preprocessor. You can
2502 do include file processing with the @code{.include} directive
2503 (@pxref{Include,,@code{.include}}). You can use the @sc{gnu} C compiler driver
2504 to get other ``CPP'' style preprocessing by giving the input file a
2505 @samp{.S} suffix. @xref{Overall Options, ,Options Controlling the Kind of
2506 Output, gcc.info, Using GNU CC}.
2508 Excess whitespace, comments, and character constants
2509 cannot be used in the portions of the input text that are not
2512 @cindex turning preprocessing on and off
2513 @cindex preprocessing, turning on and off
2516 If the first line of an input file is @code{#NO_APP} or if you use the
2517 @samp{-f} option, whitespace and comments are not removed from the input file.
2518 Within an input file, you can ask for whitespace and comment removal in
2519 specific portions of the by putting a line that says @code{#APP} before the
2520 text that may contain whitespace or comments, and putting a line that says
2521 @code{#NO_APP} after this text. This feature is mainly intend to support
2522 @code{asm} statements in compilers whose output is otherwise free of comments
2529 @dfn{Whitespace} is one or more blanks or tabs, in any order.
2530 Whitespace is used to separate symbols, and to make programs neater for
2531 people to read. Unless within character constants
2532 (@pxref{Characters,,Character Constants}), any whitespace means the same
2533 as exactly one space.
2539 There are two ways of rendering comments to @command{@value{AS}}. In both
2540 cases the comment is equivalent to one space.
2542 Anything from @samp{/*} through the next @samp{*/} is a comment.
2543 This means you may not nest these comments.
2547 The only way to include a newline ('\n') in a comment
2548 is to use this sort of comment.
2551 /* This sort of comment does not nest. */
2554 @cindex line comment character
2555 Anything from a @dfn{line comment} character up to the next newline is
2556 considered a comment and is ignored. The line comment character is target
2557 specific, and some targets multiple comment characters. Some targets also have
2558 line comment characters that only work if they are the first character on a
2559 line. Some targets use a sequence of two characters to introduce a line
2560 comment. Some targets can also change their line comment characters depending
2561 upon command line options that have been used. For more details see the
2562 @emph{Syntax} section in the documentation for individual targets.
2564 If the line comment character is the hash sign (@samp{#}) then it still has the
2565 special ability to enable and disable preprocessing (@pxref{Preprocessing}) and
2566 to specify logical line numbers:
2569 @cindex lines starting with @code{#}
2570 @cindex logical line numbers
2571 To be compatible with past assemblers, lines that begin with @samp{#} have a
2572 special interpretation. Following the @samp{#} should be an absolute
2573 expression (@pxref{Expressions}): the logical line number of the @emph{next}
2574 line. Then a string (@pxref{Strings, ,Strings}) is allowed: if present it is a
2575 new logical file name. The rest of the line, if any, should be whitespace.
2577 If the first non-whitespace characters on the line are not numeric,
2578 the line is ignored. (Just like a comment.)
2581 # This is an ordinary comment.
2582 # 42-6 "new_file_name" # New logical file name
2583 # This is logical line # 36.
2585 This feature is deprecated, and may disappear from future versions
2586 of @command{@value{AS}}.
2591 @cindex characters used in symbols
2592 @ifclear SPECIAL-SYMS
2593 A @dfn{symbol} is one or more characters chosen from the set of all
2594 letters (both upper and lower case), digits and the three characters
2600 A @dfn{symbol} is one or more characters chosen from the set of all
2601 letters (both upper and lower case), digits and the three characters
2602 @samp{._$}. (Save that, on the H8/300 only, you may not use @samp{$} in
2608 On most machines, you can also use @code{$} in symbol names; exceptions
2609 are noted in @ref{Machine Dependencies}.
2611 No symbol may begin with a digit. Case is significant.
2612 There is no length limit: all characters are significant. Multibyte characters
2613 are supported. Symbols are delimited by characters not in that set, or by the
2614 beginning of a file (since the source program must end with a newline, the end
2615 of a file is not a possible symbol delimiter). @xref{Symbols}.
2616 @cindex length of symbols
2621 @cindex statements, structure of
2622 @cindex line separator character
2623 @cindex statement separator character
2625 A @dfn{statement} ends at a newline character (@samp{\n}) or a
2626 @dfn{line separator character}. The line separator character is target
2627 specific and described in the @emph{Syntax} section of each
2628 target's documentation. Not all targets support a line separator character.
2629 The newline or line separator character is considered to be part of the
2630 preceding statement. Newlines and separators within character constants are an
2631 exception: they do not end statements.
2633 @cindex newline, required at file end
2634 @cindex EOF, newline must precede
2635 It is an error to end any statement with end-of-file: the last
2636 character of any input file should be a newline.@refill
2638 An empty statement is allowed, and may include whitespace. It is ignored.
2640 @cindex instructions and directives
2641 @cindex directives and instructions
2642 @c "key symbol" is not used elsewhere in the document; seems pedantic to
2643 @c @defn{} it in that case, as was done previously... doc@cygnus.com,
2645 A statement begins with zero or more labels, optionally followed by a
2646 key symbol which determines what kind of statement it is. The key
2647 symbol determines the syntax of the rest of the statement. If the
2648 symbol begins with a dot @samp{.} then the statement is an assembler
2649 directive: typically valid for any computer. If the symbol begins with
2650 a letter the statement is an assembly language @dfn{instruction}: it
2651 assembles into a machine language instruction.
2653 Different versions of @command{@value{AS}} for different computers
2654 recognize different instructions. In fact, the same symbol may
2655 represent a different instruction in a different computer's assembly
2659 @cindex @code{:} (label)
2660 @cindex label (@code{:})
2661 A label is a symbol immediately followed by a colon (@code{:}).
2662 Whitespace before a label or after a colon is permitted, but you may not
2663 have whitespace between a label's symbol and its colon. @xref{Labels}.
2666 For HPPA targets, labels need not be immediately followed by a colon, but
2667 the definition of a label must begin in column zero. This also implies that
2668 only one label may be defined on each line.
2672 label: .directive followed by something
2673 another_label: # This is an empty statement.
2674 instruction operand_1, operand_2, @dots{}
2681 A constant is a number, written so that its value is known by
2682 inspection, without knowing any context. Like this:
2685 .byte 74, 0112, 092, 0x4A, 0X4a, 'J, '\J # All the same value.
2686 .ascii "Ring the bell\7" # A string constant.
2687 .octa 0x123456789abcdef0123456789ABCDEF0 # A bignum.
2688 .float 0f-314159265358979323846264338327\
2689 95028841971.693993751E-40 # - pi, a flonum.
2694 * Characters:: Character Constants
2695 * Numbers:: Number Constants
2699 @subsection Character Constants
2701 @cindex character constants
2702 @cindex constants, character
2703 There are two kinds of character constants. A @dfn{character} stands
2704 for one character in one byte and its value may be used in
2705 numeric expressions. String constants (properly called string
2706 @emph{literals}) are potentially many bytes and their values may not be
2707 used in arithmetic expressions.
2711 * Chars:: Characters
2715 @subsubsection Strings
2717 @cindex string constants
2718 @cindex constants, string
2719 A @dfn{string} is written between double-quotes. It may contain
2720 double-quotes or null characters. The way to get special characters
2721 into a string is to @dfn{escape} these characters: precede them with
2722 a backslash @samp{\} character. For example @samp{\\} represents
2723 one backslash: the first @code{\} is an escape which tells
2724 @command{@value{AS}} to interpret the second character literally as a backslash
2725 (which prevents @command{@value{AS}} from recognizing the second @code{\} as an
2726 escape character). The complete list of escapes follows.
2728 @cindex escape codes, character
2729 @cindex character escape codes
2732 @c Mnemonic for ACKnowledge; for ASCII this is octal code 007.
2734 @cindex @code{\b} (backspace character)
2735 @cindex backspace (@code{\b})
2737 Mnemonic for backspace; for ASCII this is octal code 010.
2740 @c Mnemonic for EOText; for ASCII this is octal code 004.
2742 @cindex @code{\f} (formfeed character)
2743 @cindex formfeed (@code{\f})
2745 Mnemonic for FormFeed; for ASCII this is octal code 014.
2747 @cindex @code{\n} (newline character)
2748 @cindex newline (@code{\n})
2750 Mnemonic for newline; for ASCII this is octal code 012.
2753 @c Mnemonic for prefix; for ASCII this is octal code 033, usually known as @code{escape}.
2755 @cindex @code{\r} (carriage return character)
2756 @cindex carriage return (@code{\r})
2758 Mnemonic for carriage-Return; for ASCII this is octal code 015.
2761 @c Mnemonic for space; for ASCII this is octal code 040. Included for compliance with
2762 @c other assemblers.
2764 @cindex @code{\t} (tab)
2765 @cindex tab (@code{\t})
2767 Mnemonic for horizontal Tab; for ASCII this is octal code 011.
2770 @c Mnemonic for Vertical tab; for ASCII this is octal code 013.
2771 @c @item \x @var{digit} @var{digit} @var{digit}
2772 @c A hexadecimal character code. The numeric code is 3 hexadecimal digits.
2774 @cindex @code{\@var{ddd}} (octal character code)
2775 @cindex octal character code (@code{\@var{ddd}})
2776 @item \ @var{digit} @var{digit} @var{digit}
2777 An octal character code. The numeric code is 3 octal digits.
2778 For compatibility with other Unix systems, 8 and 9 are accepted as digits:
2779 for example, @code{\008} has the value 010, and @code{\009} the value 011.
2781 @cindex @code{\@var{xd...}} (hex character code)
2782 @cindex hex character code (@code{\@var{xd...}})
2783 @item \@code{x} @var{hex-digits...}
2784 A hex character code. All trailing hex digits are combined. Either upper or
2785 lower case @code{x} works.
2787 @cindex @code{\\} (@samp{\} character)
2788 @cindex backslash (@code{\\})
2790 Represents one @samp{\} character.
2793 @c Represents one @samp{'} (accent acute) character.
2794 @c This is needed in single character literals
2795 @c (@xref{Characters,,Character Constants}.) to represent
2798 @cindex @code{\"} (doublequote character)
2799 @cindex doublequote (@code{\"})
2801 Represents one @samp{"} character. Needed in strings to represent
2802 this character, because an unescaped @samp{"} would end the string.
2804 @item \ @var{anything-else}
2805 Any other character when escaped by @kbd{\} gives a warning, but
2806 assembles as if the @samp{\} was not present. The idea is that if
2807 you used an escape sequence you clearly didn't want the literal
2808 interpretation of the following character. However @command{@value{AS}} has no
2809 other interpretation, so @command{@value{AS}} knows it is giving you the wrong
2810 code and warns you of the fact.
2813 Which characters are escapable, and what those escapes represent,
2814 varies widely among assemblers. The current set is what we think
2815 the BSD 4.2 assembler recognizes, and is a subset of what most C
2816 compilers recognize. If you are in doubt, do not use an escape
2820 @subsubsection Characters
2822 @cindex single character constant
2823 @cindex character, single
2824 @cindex constant, single character
2825 A single character may be written as a single quote immediately
2826 followed by that character. The same escapes apply to characters as
2827 to strings. So if you want to write the character backslash, you
2828 must write @kbd{'\\} where the first @code{\} escapes the second
2829 @code{\}. As you can see, the quote is an acute accent, not a
2830 grave accent. A newline
2832 @ifclear abnormal-separator
2833 (or semicolon @samp{;})
2835 @ifset abnormal-separator
2837 (or dollar sign @samp{$}, for the H8/300; or semicolon @samp{;} for the
2842 immediately following an acute accent is taken as a literal character
2843 and does not count as the end of a statement. The value of a character
2844 constant in a numeric expression is the machine's byte-wide code for
2845 that character. @command{@value{AS}} assumes your character code is ASCII:
2846 @kbd{'A} means 65, @kbd{'B} means 66, and so on. @refill
2849 @subsection Number Constants
2851 @cindex constants, number
2852 @cindex number constants
2853 @command{@value{AS}} distinguishes three kinds of numbers according to how they
2854 are stored in the target machine. @emph{Integers} are numbers that
2855 would fit into an @code{int} in the C language. @emph{Bignums} are
2856 integers, but they are stored in more than 32 bits. @emph{Flonums}
2857 are floating point numbers, described below.
2860 * Integers:: Integers
2865 * Bit Fields:: Bit Fields
2871 @subsubsection Integers
2873 @cindex constants, integer
2875 @cindex binary integers
2876 @cindex integers, binary
2877 A binary integer is @samp{0b} or @samp{0B} followed by zero or more of
2878 the binary digits @samp{01}.
2880 @cindex octal integers
2881 @cindex integers, octal
2882 An octal integer is @samp{0} followed by zero or more of the octal
2883 digits (@samp{01234567}).
2885 @cindex decimal integers
2886 @cindex integers, decimal
2887 A decimal integer starts with a non-zero digit followed by zero or
2888 more digits (@samp{0123456789}).
2890 @cindex hexadecimal integers
2891 @cindex integers, hexadecimal
2892 A hexadecimal integer is @samp{0x} or @samp{0X} followed by one or
2893 more hexadecimal digits chosen from @samp{0123456789abcdefABCDEF}.
2895 Integers have the usual values. To denote a negative integer, use
2896 the prefix operator @samp{-} discussed under expressions
2897 (@pxref{Prefix Ops,,Prefix Operators}).
2900 @subsubsection Bignums
2903 @cindex constants, bignum
2904 A @dfn{bignum} has the same syntax and semantics as an integer
2905 except that the number (or its negative) takes more than 32 bits to
2906 represent in binary. The distinction is made because in some places
2907 integers are permitted while bignums are not.
2910 @subsubsection Flonums
2912 @cindex floating point numbers
2913 @cindex constants, floating point
2915 @cindex precision, floating point
2916 A @dfn{flonum} represents a floating point number. The translation is
2917 indirect: a decimal floating point number from the text is converted by
2918 @command{@value{AS}} to a generic binary floating point number of more than
2919 sufficient precision. This generic floating point number is converted
2920 to a particular computer's floating point format (or formats) by a
2921 portion of @command{@value{AS}} specialized to that computer.
2923 A flonum is written by writing (in order)
2928 (@samp{0} is optional on the HPPA.)
2932 A letter, to tell @command{@value{AS}} the rest of the number is a flonum.
2934 @kbd{e} is recommended. Case is not important.
2936 @c FIXME: verify if flonum syntax really this vague for most cases
2937 (Any otherwise illegal letter works here, but that might be changed. Vax BSD
2938 4.2 assembler seems to allow any of @samp{defghDEFGH}.)
2941 On the H8/300, Renesas / SuperH SH,
2942 and AMD 29K architectures, the letter must be
2943 one of the letters @samp{DFPRSX} (in upper or lower case).
2945 On the ARC, the letter must be one of the letters @samp{DFRS}
2946 (in upper or lower case).
2948 On the Intel 960 architecture, the letter must be
2949 one of the letters @samp{DFT} (in upper or lower case).
2951 On the HPPA architecture, the letter must be @samp{E} (upper case only).
2955 One of the letters @samp{DFRS} (in upper or lower case).
2958 One of the letters @samp{DFPRSX} (in upper or lower case).
2961 The letter @samp{E} (upper case only).
2964 One of the letters @samp{DFT} (in upper or lower case).
2969 An optional sign: either @samp{+} or @samp{-}.
2972 An optional @dfn{integer part}: zero or more decimal digits.
2975 An optional @dfn{fractional part}: @samp{.} followed by zero
2976 or more decimal digits.
2979 An optional exponent, consisting of:
2983 An @samp{E} or @samp{e}.
2984 @c I can't find a config where "EXP_CHARS" is other than 'eE', but in
2985 @c principle this can perfectly well be different on different targets.
2987 Optional sign: either @samp{+} or @samp{-}.
2989 One or more decimal digits.
2994 At least one of the integer part or the fractional part must be
2995 present. The floating point number has the usual base-10 value.
2997 @command{@value{AS}} does all processing using integers. Flonums are computed
2998 independently of any floating point hardware in the computer running
2999 @command{@value{AS}}.
3003 @c Bit fields are written as a general facility but are also controlled
3004 @c by a conditional-compilation flag---which is as of now (21mar91)
3005 @c turned on only by the i960 config of GAS.
3007 @subsubsection Bit Fields
3010 @cindex constants, bit field
3011 You can also define numeric constants as @dfn{bit fields}.
3012 Specify two numbers separated by a colon---
3014 @var{mask}:@var{value}
3017 @command{@value{AS}} applies a bitwise @sc{and} between @var{mask} and
3020 The resulting number is then packed
3022 @c this conditional paren in case bit fields turned on elsewhere than 960
3023 (in host-dependent byte order)
3025 into a field whose width depends on which assembler directive has the
3026 bit-field as its argument. Overflow (a result from the bitwise and
3027 requiring more binary digits to represent) is not an error; instead,
3028 more constants are generated, of the specified width, beginning with the
3029 least significant digits.@refill
3031 The directives @code{.byte}, @code{.hword}, @code{.int}, @code{.long},
3032 @code{.short}, and @code{.word} accept bit-field arguments.
3037 @chapter Sections and Relocation
3042 * Secs Background:: Background
3043 * Ld Sections:: Linker Sections
3044 * As Sections:: Assembler Internal Sections
3045 * Sub-Sections:: Sub-Sections
3049 @node Secs Background
3052 Roughly, a section is a range of addresses, with no gaps; all data
3053 ``in'' those addresses is treated the same for some particular purpose.
3054 For example there may be a ``read only'' section.
3056 @cindex linker, and assembler
3057 @cindex assembler, and linker
3058 The linker @code{@value{LD}} reads many object files (partial programs) and
3059 combines their contents to form a runnable program. When @command{@value{AS}}
3060 emits an object file, the partial program is assumed to start at address 0.
3061 @code{@value{LD}} assigns the final addresses for the partial program, so that
3062 different partial programs do not overlap. This is actually an
3063 oversimplification, but it suffices to explain how @command{@value{AS}} uses
3066 @code{@value{LD}} moves blocks of bytes of your program to their run-time
3067 addresses. These blocks slide to their run-time addresses as rigid
3068 units; their length does not change and neither does the order of bytes
3069 within them. Such a rigid unit is called a @emph{section}. Assigning
3070 run-time addresses to sections is called @dfn{relocation}. It includes
3071 the task of adjusting mentions of object-file addresses so they refer to
3072 the proper run-time addresses.
3074 For the H8/300, and for the Renesas / SuperH SH,
3075 @command{@value{AS}} pads sections if needed to
3076 ensure they end on a word (sixteen bit) boundary.
3079 @cindex standard assembler sections
3080 An object file written by @command{@value{AS}} has at least three sections, any
3081 of which may be empty. These are named @dfn{text}, @dfn{data} and
3086 When it generates COFF or ELF output,
3088 @command{@value{AS}} can also generate whatever other named sections you specify
3089 using the @samp{.section} directive (@pxref{Section,,@code{.section}}).
3090 If you do not use any directives that place output in the @samp{.text}
3091 or @samp{.data} sections, these sections still exist, but are empty.
3096 When @command{@value{AS}} generates SOM or ELF output for the HPPA,
3098 @command{@value{AS}} can also generate whatever other named sections you
3099 specify using the @samp{.space} and @samp{.subspace} directives. See
3100 @cite{HP9000 Series 800 Assembly Language Reference Manual}
3101 (HP 92432-90001) for details on the @samp{.space} and @samp{.subspace}
3102 assembler directives.
3105 Additionally, @command{@value{AS}} uses different names for the standard
3106 text, data, and bss sections when generating SOM output. Program text
3107 is placed into the @samp{$CODE$} section, data into @samp{$DATA$}, and
3108 BSS into @samp{$BSS$}.
3112 Within the object file, the text section starts at address @code{0}, the
3113 data section follows, and the bss section follows the data section.
3116 When generating either SOM or ELF output files on the HPPA, the text
3117 section starts at address @code{0}, the data section at address
3118 @code{0x4000000}, and the bss section follows the data section.
3121 To let @code{@value{LD}} know which data changes when the sections are
3122 relocated, and how to change that data, @command{@value{AS}} also writes to the
3123 object file details of the relocation needed. To perform relocation
3124 @code{@value{LD}} must know, each time an address in the object
3128 Where in the object file is the beginning of this reference to
3131 How long (in bytes) is this reference?
3133 Which section does the address refer to? What is the numeric value of
3135 (@var{address}) @minus{} (@var{start-address of section})?
3138 Is the reference to an address ``Program-Counter relative''?
3141 @cindex addresses, format of
3142 @cindex section-relative addressing
3143 In fact, every address @command{@value{AS}} ever uses is expressed as
3145 (@var{section}) + (@var{offset into section})
3148 Further, most expressions @command{@value{AS}} computes have this section-relative
3151 (For some object formats, such as SOM for the HPPA, some expressions are
3152 symbol-relative instead.)
3155 In this manual we use the notation @{@var{secname} @var{N}@} to mean ``offset
3156 @var{N} into section @var{secname}.''
3158 Apart from text, data and bss sections you need to know about the
3159 @dfn{absolute} section. When @code{@value{LD}} mixes partial programs,
3160 addresses in the absolute section remain unchanged. For example, address
3161 @code{@{absolute 0@}} is ``relocated'' to run-time address 0 by
3162 @code{@value{LD}}. Although the linker never arranges two partial programs'
3163 data sections with overlapping addresses after linking, @emph{by definition}
3164 their absolute sections must overlap. Address @code{@{absolute@ 239@}} in one
3165 part of a program is always the same address when the program is running as
3166 address @code{@{absolute@ 239@}} in any other part of the program.
3168 The idea of sections is extended to the @dfn{undefined} section. Any
3169 address whose section is unknown at assembly time is by definition
3170 rendered @{undefined @var{U}@}---where @var{U} is filled in later.
3171 Since numbers are always defined, the only way to generate an undefined
3172 address is to mention an undefined symbol. A reference to a named
3173 common block would be such a symbol: its value is unknown at assembly
3174 time so it has section @emph{undefined}.
3176 By analogy the word @emph{section} is used to describe groups of sections in
3177 the linked program. @code{@value{LD}} puts all partial programs' text
3178 sections in contiguous addresses in the linked program. It is
3179 customary to refer to the @emph{text section} of a program, meaning all
3180 the addresses of all partial programs' text sections. Likewise for
3181 data and bss sections.
3183 Some sections are manipulated by @code{@value{LD}}; others are invented for
3184 use of @command{@value{AS}} and have no meaning except during assembly.
3187 @section Linker Sections
3188 @code{@value{LD}} deals with just four kinds of sections, summarized below.
3193 @cindex named sections
3194 @cindex sections, named
3195 @item named sections
3198 @cindex text section
3199 @cindex data section
3203 These sections hold your program. @command{@value{AS}} and @code{@value{LD}} treat them as
3204 separate but equal sections. Anything you can say of one section is
3207 When the program is running, however, it is
3208 customary for the text section to be unalterable. The
3209 text section is often shared among processes: it contains
3210 instructions, constants and the like. The data section of a running
3211 program is usually alterable: for example, C variables would be stored
3212 in the data section.
3217 This section contains zeroed bytes when your program begins running. It
3218 is used to hold uninitialized variables or common storage. The length of
3219 each partial program's bss section is important, but because it starts
3220 out containing zeroed bytes there is no need to store explicit zero
3221 bytes in the object file. The bss section was invented to eliminate
3222 those explicit zeros from object files.
3224 @cindex absolute section
3225 @item absolute section
3226 Address 0 of this section is always ``relocated'' to runtime address 0.
3227 This is useful if you want to refer to an address that @code{@value{LD}} must
3228 not change when relocating. In this sense we speak of absolute
3229 addresses being ``unrelocatable'': they do not change during relocation.
3231 @cindex undefined section
3232 @item undefined section
3233 This ``section'' is a catch-all for address references to objects not in
3234 the preceding sections.
3235 @c FIXME: ref to some other doc on obj-file formats could go here.
3238 @cindex relocation example
3239 An idealized example of three relocatable sections follows.
3241 The example uses the traditional section names @samp{.text} and @samp{.data}.
3243 Memory addresses are on the horizontal axis.
3247 @c END TEXI2ROFF-KILL
3250 partial program # 1: |ttttt|dddd|00|
3257 partial program # 2: |TTT|DDD|000|
3260 +--+---+-----+--+----+---+-----+~~
3261 linked program: | |TTT|ttttt| |dddd|DDD|00000|
3262 +--+---+-----+--+----+---+-----+~~
3264 addresses: 0 @dots{}
3271 \line{\it Partial program \#1: \hfil}
3272 \line{\ibox{2.5cm}{\tt text}\ibox{2cm}{\tt data}\ibox{1cm}{\tt bss}\hfil}
3273 \line{\boxit{2.5cm}{\tt ttttt}\boxit{2cm}{\tt dddd}\boxit{1cm}{\tt 00}\hfil}
3275 \line{\it Partial program \#2: \hfil}
3276 \line{\ibox{1cm}{\tt text}\ibox{1.5cm}{\tt data}\ibox{1cm}{\tt bss}\hfil}
3277 \line{\boxit{1cm}{\tt TTT}\boxit{1.5cm}{\tt DDDD}\boxit{1cm}{\tt 000}\hfil}
3279 \line{\it linked program: \hfil}
3280 \line{\ibox{.5cm}{}\ibox{1cm}{\tt text}\ibox{2.5cm}{}\ibox{.75cm}{}\ibox{2cm}{\tt data}\ibox{1.5cm}{}\ibox{2cm}{\tt bss}\hfil}
3281 \line{\boxit{.5cm}{}\boxit{1cm}{\tt TTT}\boxit{2.5cm}{\tt
3282 ttttt}\boxit{.75cm}{}\boxit{2cm}{\tt dddd}\boxit{1.5cm}{\tt
3283 DDDD}\boxit{2cm}{\tt 00000}\ \dots\hfil}
3285 \line{\it addresses: \hfil}
3289 @c END TEXI2ROFF-KILL
3292 @section Assembler Internal Sections
3294 @cindex internal assembler sections
3295 @cindex sections in messages, internal
3296 These sections are meant only for the internal use of @command{@value{AS}}. They
3297 have no meaning at run-time. You do not really need to know about these
3298 sections for most purposes; but they can be mentioned in @command{@value{AS}}
3299 warning messages, so it might be helpful to have an idea of their
3300 meanings to @command{@value{AS}}. These sections are used to permit the
3301 value of every expression in your assembly language program to be a
3302 section-relative address.
3305 @cindex assembler internal logic error
3306 @item ASSEMBLER-INTERNAL-LOGIC-ERROR!
3307 An internal assembler logic error has been found. This means there is a
3308 bug in the assembler.
3310 @cindex expr (internal section)
3312 The assembler stores complex expression internally as combinations of
3313 symbols. When it needs to represent an expression as a symbol, it puts
3314 it in the expr section.
3316 @c FIXME item transfer[t] vector preload
3317 @c FIXME item transfer[t] vector postload
3318 @c FIXME item register
3322 @section Sub-Sections
3324 @cindex numbered subsections
3325 @cindex grouping data
3331 fall into two sections: text and data.
3333 You may have separate groups of
3335 data in named sections
3339 data in named sections
3345 that you want to end up near to each other in the object file, even though they
3346 are not contiguous in the assembler source. @command{@value{AS}} allows you to
3347 use @dfn{subsections} for this purpose. Within each section, there can be
3348 numbered subsections with values from 0 to 8192. Objects assembled into the
3349 same subsection go into the object file together with other objects in the same
3350 subsection. For example, a compiler might want to store constants in the text
3351 section, but might not want to have them interspersed with the program being
3352 assembled. In this case, the compiler could issue a @samp{.text 0} before each
3353 section of code being output, and a @samp{.text 1} before each group of
3354 constants being output.
3356 Subsections are optional. If you do not use subsections, everything
3357 goes in subsection number zero.
3360 Each subsection is zero-padded up to a multiple of four bytes.
3361 (Subsections may be padded a different amount on different flavors
3362 of @command{@value{AS}}.)
3366 On the H8/300 platform, each subsection is zero-padded to a word
3367 boundary (two bytes).
3368 The same is true on the Renesas SH.
3371 @c FIXME section padding (alignment)?
3372 @c Rich Pixley says padding here depends on target obj code format; that
3373 @c doesn't seem particularly useful to say without further elaboration,
3374 @c so for now I say nothing about it. If this is a generic BFD issue,
3375 @c these paragraphs might need to vanish from this manual, and be
3376 @c discussed in BFD chapter of binutils (or some such).
3380 Subsections appear in your object file in numeric order, lowest numbered
3381 to highest. (All this to be compatible with other people's assemblers.)
3382 The object file contains no representation of subsections; @code{@value{LD}} and
3383 other programs that manipulate object files see no trace of them.
3384 They just see all your text subsections as a text section, and all your
3385 data subsections as a data section.
3387 To specify which subsection you want subsequent statements assembled
3388 into, use a numeric argument to specify it, in a @samp{.text
3389 @var{expression}} or a @samp{.data @var{expression}} statement.
3392 When generating COFF output, you
3397 can also use an extra subsection
3398 argument with arbitrary named sections: @samp{.section @var{name},
3403 When generating ELF output, you
3408 can also use the @code{.subsection} directive (@pxref{SubSection})
3409 to specify a subsection: @samp{.subsection @var{expression}}.
3411 @var{Expression} should be an absolute expression
3412 (@pxref{Expressions}). If you just say @samp{.text} then @samp{.text 0}
3413 is assumed. Likewise @samp{.data} means @samp{.data 0}. Assembly
3414 begins in @code{text 0}. For instance:
3416 .text 0 # The default subsection is text 0 anyway.
3417 .ascii "This lives in the first text subsection. *"
3419 .ascii "But this lives in the second text subsection."
3421 .ascii "This lives in the data section,"
3422 .ascii "in the first data subsection."
3424 .ascii "This lives in the first text section,"
3425 .ascii "immediately following the asterisk (*)."
3428 Each section has a @dfn{location counter} incremented by one for every byte
3429 assembled into that section. Because subsections are merely a convenience
3430 restricted to @command{@value{AS}} there is no concept of a subsection location
3431 counter. There is no way to directly manipulate a location counter---but the
3432 @code{.align} directive changes it, and any label definition captures its
3433 current value. The location counter of the section where statements are being
3434 assembled is said to be the @dfn{active} location counter.
3437 @section bss Section
3440 @cindex common variable storage
3441 The bss section is used for local common variable storage.
3442 You may allocate address space in the bss section, but you may
3443 not dictate data to load into it before your program executes. When
3444 your program starts running, all the contents of the bss
3445 section are zeroed bytes.
3447 The @code{.lcomm} pseudo-op defines a symbol in the bss section; see
3448 @ref{Lcomm,,@code{.lcomm}}.
3450 The @code{.comm} pseudo-op may be used to declare a common symbol, which is
3451 another form of uninitialized symbol; see @ref{Comm,,@code{.comm}}.
3454 When assembling for a target which supports multiple sections, such as ELF or
3455 COFF, you may switch into the @code{.bss} section and define symbols as usual;
3456 see @ref{Section,,@code{.section}}. You may only assemble zero values into the
3457 section. Typically the section will only contain symbol definitions and
3458 @code{.skip} directives (@pxref{Skip,,@code{.skip}}).
3465 Symbols are a central concept: the programmer uses symbols to name
3466 things, the linker uses symbols to link, and the debugger uses symbols
3470 @cindex debuggers, and symbol order
3471 @emph{Warning:} @command{@value{AS}} does not place symbols in the object file in
3472 the same order they were declared. This may break some debuggers.
3477 * Setting Symbols:: Giving Symbols Other Values
3478 * Symbol Names:: Symbol Names
3479 * Dot:: The Special Dot Symbol
3480 * Symbol Attributes:: Symbol Attributes
3487 A @dfn{label} is written as a symbol immediately followed by a colon
3488 @samp{:}. The symbol then represents the current value of the
3489 active location counter, and is, for example, a suitable instruction
3490 operand. You are warned if you use the same symbol to represent two
3491 different locations: the first definition overrides any other
3495 On the HPPA, the usual form for a label need not be immediately followed by a
3496 colon, but instead must start in column zero. Only one label may be defined on
3497 a single line. To work around this, the HPPA version of @command{@value{AS}} also
3498 provides a special directive @code{.label} for defining labels more flexibly.
3501 @node Setting Symbols
3502 @section Giving Symbols Other Values
3504 @cindex assigning values to symbols
3505 @cindex symbol values, assigning
3506 A symbol can be given an arbitrary value by writing a symbol, followed
3507 by an equals sign @samp{=}, followed by an expression
3508 (@pxref{Expressions}). This is equivalent to using the @code{.set}
3509 directive. @xref{Set,,@code{.set}}. In the same way, using a double
3510 equals sign @samp{=}@samp{=} here represents an equivalent of the
3511 @code{.eqv} directive. @xref{Eqv,,@code{.eqv}}.
3514 Blackfin does not support symbol assignment with @samp{=}.
3518 @section Symbol Names
3520 @cindex symbol names
3521 @cindex names, symbol
3522 @ifclear SPECIAL-SYMS
3523 Symbol names begin with a letter or with one of @samp{._}. On most
3524 machines, you can also use @code{$} in symbol names; exceptions are
3525 noted in @ref{Machine Dependencies}. That character may be followed by any
3526 string of digits, letters, dollar signs (unless otherwise noted for a
3527 particular target machine), and underscores.
3531 Symbol names begin with a letter or with one of @samp{._}. On the
3532 Renesas SH you can also use @code{$} in symbol names. That
3533 character may be followed by any string of digits, letters, dollar signs (save
3534 on the H8/300), and underscores.
3538 Case of letters is significant: @code{foo} is a different symbol name
3541 Multibyte characters are supported. To generate a symbol name containing
3542 multibyte characters enclose it within double quotes and use escape codes. cf
3543 @xref{Strings}. Generating a multibyte symbol name from a label is not
3544 currently supported.
3546 Each symbol has exactly one name. Each name in an assembly language program
3547 refers to exactly one symbol. You may use that symbol name any number of times
3550 @subheading Local Symbol Names
3552 @cindex local symbol names
3553 @cindex symbol names, local
3554 A local symbol is any symbol beginning with certain local label prefixes.
3555 By default, the local label prefix is @samp{.L} for ELF systems or
3556 @samp{L} for traditional a.out systems, but each target may have its own
3557 set of local label prefixes.
3559 On the HPPA local symbols begin with @samp{L$}.
3562 Local symbols are defined and used within the assembler, but they are
3563 normally not saved in object files. Thus, they are not visible when debugging.
3564 You may use the @samp{-L} option (@pxref{L, ,Include Local Symbols:
3565 @option{-L}}) to retain the local symbols in the object files.
3567 @subheading Local Labels
3569 @cindex local labels
3570 @cindex temporary symbol names
3571 @cindex symbol names, temporary
3572 Local labels help compilers and programmers use names temporarily.
3573 They create symbols which are guaranteed to be unique over the entire scope of
3574 the input source code and which can be referred to by a simple notation.
3575 To define a local label, write a label of the form @samp{@b{N}:} (where @b{N}
3576 represents any positive integer). To refer to the most recent previous
3577 definition of that label write @samp{@b{N}b}, using the same number as when
3578 you defined the label. To refer to the next definition of a local label, write
3579 @samp{@b{N}f}---the @samp{b} stands for ``backwards'' and the @samp{f} stands
3582 There is no restriction on how you can use these labels, and you can reuse them
3583 too. So that it is possible to repeatedly define the same local label (using
3584 the same number @samp{@b{N}}), although you can only refer to the most recently
3585 defined local label of that number (for a backwards reference) or the next
3586 definition of a specific local label for a forward reference. It is also worth
3587 noting that the first 10 local labels (@samp{@b{0:}}@dots{}@samp{@b{9:}}) are
3588 implemented in a slightly more efficient manner than the others.
3599 Which is the equivalent of:
3602 label_1: branch label_3
3603 label_2: branch label_1
3604 label_3: branch label_4
3605 label_4: branch label_3
3608 Local label names are only a notational device. They are immediately
3609 transformed into more conventional symbol names before the assembler uses them.
3610 The symbol names are stored in the symbol table, appear in error messages, and
3611 are optionally emitted to the object file. The names are constructed using
3615 @item @emph{local label prefix}
3616 All local symbols begin with the system-specific local label prefix.
3617 Normally both @command{@value{AS}} and @code{@value{LD}} forget symbols
3618 that start with the local label prefix. These labels are
3619 used for symbols you are never intended to see. If you use the
3620 @samp{-L} option then @command{@value{AS}} retains these symbols in the
3621 object file. If you also instruct @code{@value{LD}} to retain these symbols,
3622 you may use them in debugging.
3625 This is the number that was used in the local label definition. So if the
3626 label is written @samp{55:} then the number is @samp{55}.
3629 This unusual character is included so you do not accidentally invent a symbol
3630 of the same name. The character has ASCII value of @samp{\002} (control-B).
3632 @item @emph{ordinal number}
3633 This is a serial number to keep the labels distinct. The first definition of
3634 @samp{0:} gets the number @samp{1}. The 15th definition of @samp{0:} gets the
3635 number @samp{15}, and so on. Likewise the first definition of @samp{1:} gets
3636 the number @samp{1} and its 15th definition gets @samp{15} as well.
3639 So for example, the first @code{1:} may be named @code{.L1@kbd{C-B}1}, and
3640 the 44th @code{3:} may be named @code{.L3@kbd{C-B}44}.
3642 @subheading Dollar Local Labels
3643 @cindex dollar local symbols
3645 @code{@value{AS}} also supports an even more local form of local labels called
3646 dollar labels. These labels go out of scope (i.e., they become undefined) as
3647 soon as a non-local label is defined. Thus they remain valid for only a small
3648 region of the input source code. Normal local labels, by contrast, remain in
3649 scope for the entire file, or until they are redefined by another occurrence of
3650 the same local label.
3652 Dollar labels are defined in exactly the same way as ordinary local labels,
3653 except that they have a dollar sign suffix to their numeric value, e.g.,
3656 They can also be distinguished from ordinary local labels by their transformed
3657 names which use ASCII character @samp{\001} (control-A) as the magic character
3658 to distinguish them from ordinary labels. For example, the fifth definition of
3659 @samp{6$} may be named @samp{.L6@kbd{C-A}5}.
3662 @section The Special Dot Symbol
3664 @cindex dot (symbol)
3665 @cindex @code{.} (symbol)
3666 @cindex current address
3667 @cindex location counter
3668 The special symbol @samp{.} refers to the current address that
3669 @command{@value{AS}} is assembling into. Thus, the expression @samp{melvin:
3670 .long .} defines @code{melvin} to contain its own address.
3671 Assigning a value to @code{.} is treated the same as a @code{.org}
3673 @ifclear no-space-dir
3674 Thus, the expression @samp{.=.+4} is the same as saying
3678 @node Symbol Attributes
3679 @section Symbol Attributes
3681 @cindex symbol attributes
3682 @cindex attributes, symbol
3683 Every symbol has, as well as its name, the attributes ``Value'' and
3684 ``Type''. Depending on output format, symbols can also have auxiliary
3687 The detailed definitions are in @file{a.out.h}.
3690 If you use a symbol without defining it, @command{@value{AS}} assumes zero for
3691 all these attributes, and probably won't warn you. This makes the
3692 symbol an externally defined symbol, which is generally what you
3696 * Symbol Value:: Value
3697 * Symbol Type:: Type
3700 * a.out Symbols:: Symbol Attributes: @code{a.out}
3704 * a.out Symbols:: Symbol Attributes: @code{a.out}
3707 * a.out Symbols:: Symbol Attributes: @code{a.out}, @code{b.out}
3712 * COFF Symbols:: Symbol Attributes for COFF
3715 * SOM Symbols:: Symbol Attributes for SOM
3722 @cindex value of a symbol
3723 @cindex symbol value
3724 The value of a symbol is (usually) 32 bits. For a symbol which labels a
3725 location in the text, data, bss or absolute sections the value is the
3726 number of addresses from the start of that section to the label.
3727 Naturally for text, data and bss sections the value of a symbol changes
3728 as @code{@value{LD}} changes section base addresses during linking. Absolute
3729 symbols' values do not change during linking: that is why they are
3732 The value of an undefined symbol is treated in a special way. If it is
3733 0 then the symbol is not defined in this assembler source file, and
3734 @code{@value{LD}} tries to determine its value from other files linked into the
3735 same program. You make this kind of symbol simply by mentioning a symbol
3736 name without defining it. A non-zero value represents a @code{.comm}
3737 common declaration. The value is how much common storage to reserve, in
3738 bytes (addresses). The symbol refers to the first address of the
3744 @cindex type of a symbol
3746 The type attribute of a symbol contains relocation (section)
3747 information, any flag settings indicating that a symbol is external, and
3748 (optionally), other information for linkers and debuggers. The exact
3749 format depends on the object-code output format in use.
3754 @c The following avoids a "widow" subsection title. @group would be
3755 @c better if it were available outside examples.
3758 @subsection Symbol Attributes: @code{a.out}, @code{b.out}
3760 @cindex @code{b.out} symbol attributes
3761 @cindex symbol attributes, @code{b.out}
3762 These symbol attributes appear only when @command{@value{AS}} is configured for
3763 one of the Berkeley-descended object output formats---@code{a.out} or
3769 @subsection Symbol Attributes: @code{a.out}
3771 @cindex @code{a.out} symbol attributes
3772 @cindex symbol attributes, @code{a.out}
3778 @subsection Symbol Attributes: @code{a.out}
3780 @cindex @code{a.out} symbol attributes
3781 @cindex symbol attributes, @code{a.out}
3785 * Symbol Desc:: Descriptor
3786 * Symbol Other:: Other
3790 @subsubsection Descriptor
3792 @cindex descriptor, of @code{a.out} symbol
3793 This is an arbitrary 16-bit value. You may establish a symbol's
3794 descriptor value by using a @code{.desc} statement
3795 (@pxref{Desc,,@code{.desc}}). A descriptor value means nothing to
3796 @command{@value{AS}}.
3799 @subsubsection Other
3801 @cindex other attribute, of @code{a.out} symbol
3802 This is an arbitrary 8-bit value. It means nothing to @command{@value{AS}}.
3807 @subsection Symbol Attributes for COFF
3809 @cindex COFF symbol attributes
3810 @cindex symbol attributes, COFF
3812 The COFF format supports a multitude of auxiliary symbol attributes;
3813 like the primary symbol attributes, they are set between @code{.def} and
3814 @code{.endef} directives.
3816 @subsubsection Primary Attributes
3818 @cindex primary attributes, COFF symbols
3819 The symbol name is set with @code{.def}; the value and type,
3820 respectively, with @code{.val} and @code{.type}.
3822 @subsubsection Auxiliary Attributes
3824 @cindex auxiliary attributes, COFF symbols
3825 The @command{@value{AS}} directives @code{.dim}, @code{.line}, @code{.scl},
3826 @code{.size}, @code{.tag}, and @code{.weak} can generate auxiliary symbol
3827 table information for COFF.
3832 @subsection Symbol Attributes for SOM
3834 @cindex SOM symbol attributes
3835 @cindex symbol attributes, SOM
3837 The SOM format for the HPPA supports a multitude of symbol attributes set with
3838 the @code{.EXPORT} and @code{.IMPORT} directives.
3840 The attributes are described in @cite{HP9000 Series 800 Assembly
3841 Language Reference Manual} (HP 92432-90001) under the @code{IMPORT} and
3842 @code{EXPORT} assembler directive documentation.
3846 @chapter Expressions
3850 @cindex numeric values
3851 An @dfn{expression} specifies an address or numeric value.
3852 Whitespace may precede and/or follow an expression.
3854 The result of an expression must be an absolute number, or else an offset into
3855 a particular section. If an expression is not absolute, and there is not
3856 enough information when @command{@value{AS}} sees the expression to know its
3857 section, a second pass over the source program might be necessary to interpret
3858 the expression---but the second pass is currently not implemented.
3859 @command{@value{AS}} aborts with an error message in this situation.
3862 * Empty Exprs:: Empty Expressions
3863 * Integer Exprs:: Integer Expressions
3867 @section Empty Expressions
3869 @cindex empty expressions
3870 @cindex expressions, empty
3871 An empty expression has no value: it is just whitespace or null.
3872 Wherever an absolute expression is required, you may omit the
3873 expression, and @command{@value{AS}} assumes a value of (absolute) 0. This
3874 is compatible with other assemblers.
3877 @section Integer Expressions
3879 @cindex integer expressions
3880 @cindex expressions, integer
3881 An @dfn{integer expression} is one or more @emph{arguments} delimited
3882 by @emph{operators}.
3885 * Arguments:: Arguments
3886 * Operators:: Operators
3887 * Prefix Ops:: Prefix Operators
3888 * Infix Ops:: Infix Operators
3892 @subsection Arguments
3894 @cindex expression arguments
3895 @cindex arguments in expressions
3896 @cindex operands in expressions
3897 @cindex arithmetic operands
3898 @dfn{Arguments} are symbols, numbers or subexpressions. In other
3899 contexts arguments are sometimes called ``arithmetic operands''. In
3900 this manual, to avoid confusing them with the ``instruction operands'' of
3901 the machine language, we use the term ``argument'' to refer to parts of
3902 expressions only, reserving the word ``operand'' to refer only to machine
3903 instruction operands.
3905 Symbols are evaluated to yield @{@var{section} @var{NNN}@} where
3906 @var{section} is one of text, data, bss, absolute,
3907 or undefined. @var{NNN} is a signed, 2's complement 32 bit
3910 Numbers are usually integers.
3912 A number can be a flonum or bignum. In this case, you are warned
3913 that only the low order 32 bits are used, and @command{@value{AS}} pretends
3914 these 32 bits are an integer. You may write integer-manipulating
3915 instructions that act on exotic constants, compatible with other
3918 @cindex subexpressions
3919 Subexpressions are a left parenthesis @samp{(} followed by an integer
3920 expression, followed by a right parenthesis @samp{)}; or a prefix
3921 operator followed by an argument.
3924 @subsection Operators
3926 @cindex operators, in expressions
3927 @cindex arithmetic functions
3928 @cindex functions, in expressions
3929 @dfn{Operators} are arithmetic functions, like @code{+} or @code{%}. Prefix
3930 operators are followed by an argument. Infix operators appear
3931 between their arguments. Operators may be preceded and/or followed by
3935 @subsection Prefix Operator
3937 @cindex prefix operators
3938 @command{@value{AS}} has the following @dfn{prefix operators}. They each take
3939 one argument, which must be absolute.
3941 @c the tex/end tex stuff surrounding this small table is meant to make
3942 @c it align, on the printed page, with the similar table in the next
3943 @c section (which is inside an enumerate).
3945 \global\advance\leftskip by \itemindent
3950 @dfn{Negation}. Two's complement negation.
3952 @dfn{Complementation}. Bitwise not.
3956 \global\advance\leftskip by -\itemindent
3960 @subsection Infix Operators
3962 @cindex infix operators
3963 @cindex operators, permitted arguments
3964 @dfn{Infix operators} take two arguments, one on either side. Operators
3965 have precedence, but operations with equal precedence are performed left
3966 to right. Apart from @code{+} or @option{-}, both arguments must be
3967 absolute, and the result is absolute.
3970 @cindex operator precedence
3971 @cindex precedence of operators
3978 @dfn{Multiplication}.
3981 @dfn{Division}. Truncation is the same as the C operator @samp{/}
3987 @dfn{Shift Left}. Same as the C operator @samp{<<}.
3990 @dfn{Shift Right}. Same as the C operator @samp{>>}.
3994 Intermediate precedence
3999 @dfn{Bitwise Inclusive Or}.
4005 @dfn{Bitwise Exclusive Or}.
4008 @dfn{Bitwise Or Not}.
4015 @cindex addition, permitted arguments
4016 @cindex plus, permitted arguments
4017 @cindex arguments for addition
4019 @dfn{Addition}. If either argument is absolute, the result has the section of
4020 the other argument. You may not add together arguments from different
4023 @cindex subtraction, permitted arguments
4024 @cindex minus, permitted arguments
4025 @cindex arguments for subtraction
4027 @dfn{Subtraction}. If the right argument is absolute, the
4028 result has the section of the left argument.
4029 If both arguments are in the same section, the result is absolute.
4030 You may not subtract arguments from different sections.
4031 @c FIXME is there still something useful to say about undefined - undefined ?
4033 @cindex comparison expressions
4034 @cindex expressions, comparison
4039 @dfn{Is Not Equal To}
4043 @dfn{Is Greater Than}
4045 @dfn{Is Greater Than Or Equal To}
4047 @dfn{Is Less Than Or Equal To}
4049 The comparison operators can be used as infix operators. A true results has a
4050 value of -1 whereas a false result has a value of 0. Note, these operators
4051 perform signed comparisons.
4054 @item Lowest Precedence
4063 These two logical operations can be used to combine the results of sub
4064 expressions. Note, unlike the comparison operators a true result returns a
4065 value of 1 but a false results does still return 0. Also note that the logical
4066 or operator has a slightly lower precedence than logical and.
4071 In short, it's only meaningful to add or subtract the @emph{offsets} in an
4072 address; you can only have a defined section in one of the two arguments.
4075 @chapter Assembler Directives
4077 @cindex directives, machine independent
4078 @cindex pseudo-ops, machine independent
4079 @cindex machine independent directives
4080 All assembler directives have names that begin with a period (@samp{.}).
4081 The rest of the name is letters, usually in lower case.
4083 This chapter discusses directives that are available regardless of the
4084 target machine configuration for the @sc{gnu} assembler.
4086 Some machine configurations provide additional directives.
4087 @xref{Machine Dependencies}.
4090 @ifset machine-directives
4091 @xref{Machine Dependencies}, for additional directives.
4096 * Abort:: @code{.abort}
4098 * ABORT (COFF):: @code{.ABORT}
4101 * Align:: @code{.align @var{abs-expr} , @var{abs-expr}}
4102 * Altmacro:: @code{.altmacro}
4103 * Ascii:: @code{.ascii "@var{string}"}@dots{}
4104 * Asciz:: @code{.asciz "@var{string}"}@dots{}
4105 * Balign:: @code{.balign @var{abs-expr} , @var{abs-expr}}
4106 * Bundle directives:: @code{.bundle_align_mode @var{abs-expr}}, @code{.bundle_lock}, @code{.bundle_unlock}
4107 * Byte:: @code{.byte @var{expressions}}
4108 * CFI directives:: @code{.cfi_startproc [simple]}, @code{.cfi_endproc}, etc.
4109 * Comm:: @code{.comm @var{symbol} , @var{length} }
4110 * Data:: @code{.data @var{subsection}}
4112 * Def:: @code{.def @var{name}}
4115 * Desc:: @code{.desc @var{symbol}, @var{abs-expression}}
4121 * Double:: @code{.double @var{flonums}}
4122 * Eject:: @code{.eject}
4123 * Else:: @code{.else}
4124 * Elseif:: @code{.elseif}
4127 * Endef:: @code{.endef}
4130 * Endfunc:: @code{.endfunc}
4131 * Endif:: @code{.endif}
4132 * Equ:: @code{.equ @var{symbol}, @var{expression}}
4133 * Equiv:: @code{.equiv @var{symbol}, @var{expression}}
4134 * Eqv:: @code{.eqv @var{symbol}, @var{expression}}
4136 * Error:: @code{.error @var{string}}
4137 * Exitm:: @code{.exitm}
4138 * Extern:: @code{.extern}
4139 * Fail:: @code{.fail}
4140 * File:: @code{.file}
4141 * Fill:: @code{.fill @var{repeat} , @var{size} , @var{value}}
4142 * Float:: @code{.float @var{flonums}}
4143 * Func:: @code{.func}
4144 * Global:: @code{.global @var{symbol}}, @code{.globl @var{symbol}}
4146 * Gnu_attribute:: @code{.gnu_attribute @var{tag},@var{value}}
4147 * Hidden:: @code{.hidden @var{names}}
4150 * hword:: @code{.hword @var{expressions}}
4151 * Ident:: @code{.ident}
4152 * If:: @code{.if @var{absolute expression}}
4153 * Incbin:: @code{.incbin "@var{file}"[,@var{skip}[,@var{count}]]}
4154 * Include:: @code{.include "@var{file}"}
4155 * Int:: @code{.int @var{expressions}}
4157 * Internal:: @code{.internal @var{names}}
4160 * Irp:: @code{.irp @var{symbol},@var{values}}@dots{}
4161 * Irpc:: @code{.irpc @var{symbol},@var{values}}@dots{}
4162 * Lcomm:: @code{.lcomm @var{symbol} , @var{length}}
4163 * Lflags:: @code{.lflags}
4164 @ifclear no-line-dir
4165 * Line:: @code{.line @var{line-number}}
4168 * Linkonce:: @code{.linkonce [@var{type}]}
4169 * List:: @code{.list}
4170 * Ln:: @code{.ln @var{line-number}}
4171 * Loc:: @code{.loc @var{fileno} @var{lineno}}
4172 * Loc_mark_labels:: @code{.loc_mark_labels @var{enable}}
4174 * Local:: @code{.local @var{names}}
4177 * Long:: @code{.long @var{expressions}}
4179 * Lsym:: @code{.lsym @var{symbol}, @var{expression}}
4182 * Macro:: @code{.macro @var{name} @var{args}}@dots{}
4183 * MRI:: @code{.mri @var{val}}
4184 * Noaltmacro:: @code{.noaltmacro}
4185 * Nolist:: @code{.nolist}
4186 * Octa:: @code{.octa @var{bignums}}
4187 * Offset:: @code{.offset @var{loc}}
4188 * Org:: @code{.org @var{new-lc}, @var{fill}}
4189 * P2align:: @code{.p2align @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
4191 * PopSection:: @code{.popsection}
4192 * Previous:: @code{.previous}
4195 * Print:: @code{.print @var{string}}
4197 * Protected:: @code{.protected @var{names}}
4200 * Psize:: @code{.psize @var{lines}, @var{columns}}
4201 * Purgem:: @code{.purgem @var{name}}
4203 * PushSection:: @code{.pushsection @var{name}}
4206 * Quad:: @code{.quad @var{bignums}}
4207 * Reloc:: @code{.reloc @var{offset}, @var{reloc_name}[, @var{expression}]}
4208 * Rept:: @code{.rept @var{count}}
4209 * Sbttl:: @code{.sbttl "@var{subheading}"}
4211 * Scl:: @code{.scl @var{class}}
4214 * Section:: @code{.section @var{name}[, @var{flags}]}
4217 * Set:: @code{.set @var{symbol}, @var{expression}}
4218 * Short:: @code{.short @var{expressions}}
4219 * Single:: @code{.single @var{flonums}}
4221 * Size:: @code{.size [@var{name} , @var{expression}]}
4223 @ifclear no-space-dir
4224 * Skip:: @code{.skip @var{size} , @var{fill}}
4227 * Sleb128:: @code{.sleb128 @var{expressions}}
4228 @ifclear no-space-dir
4229 * Space:: @code{.space @var{size} , @var{fill}}
4232 * Stab:: @code{.stabd, .stabn, .stabs}
4235 * String:: @code{.string "@var{str}"}, @code{.string8 "@var{str}"}, @code{.string16 "@var{str}"}, @code{.string32 "@var{str}"}, @code{.string64 "@var{str}"}
4236 * Struct:: @code{.struct @var{expression}}
4238 * SubSection:: @code{.subsection}
4239 * Symver:: @code{.symver @var{name},@var{name2@@nodename}}
4243 * Tag:: @code{.tag @var{structname}}
4246 * Text:: @code{.text @var{subsection}}
4247 * Title:: @code{.title "@var{heading}"}
4249 * Type:: @code{.type <@var{int} | @var{name} , @var{type description}>}
4252 * Uleb128:: @code{.uleb128 @var{expressions}}
4254 * Val:: @code{.val @var{addr}}
4258 * Version:: @code{.version "@var{string}"}
4259 * VTableEntry:: @code{.vtable_entry @var{table}, @var{offset}}
4260 * VTableInherit:: @code{.vtable_inherit @var{child}, @var{parent}}
4263 * Warning:: @code{.warning @var{string}}
4264 * Weak:: @code{.weak @var{names}}
4265 * Weakref:: @code{.weakref @var{alias}, @var{symbol}}
4266 * Word:: @code{.word @var{expressions}}
4267 * Deprecated:: Deprecated Directives
4271 @section @code{.abort}
4273 @cindex @code{abort} directive
4274 @cindex stopping the assembly
4275 This directive stops the assembly immediately. It is for
4276 compatibility with other assemblers. The original idea was that the
4277 assembly language source would be piped into the assembler. If the sender
4278 of the source quit, it could use this directive tells @command{@value{AS}} to
4279 quit also. One day @code{.abort} will not be supported.
4283 @section @code{.ABORT} (COFF)
4285 @cindex @code{ABORT} directive
4286 When producing COFF output, @command{@value{AS}} accepts this directive as a
4287 synonym for @samp{.abort}.
4290 When producing @code{b.out} output, @command{@value{AS}} accepts this directive,
4296 @section @code{.align @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
4298 @cindex padding the location counter
4299 @cindex @code{align} directive
4300 Pad the location counter (in the current subsection) to a particular storage
4301 boundary. The first expression (which must be absolute) is the alignment
4302 required, as described below.
4304 The second expression (also absolute) gives the fill value to be stored in the
4305 padding bytes. It (and the comma) may be omitted. If it is omitted, the
4306 padding bytes are normally zero. However, on some systems, if the section is
4307 marked as containing code and the fill value is omitted, the space is filled
4308 with no-op instructions.
4310 The third expression is also absolute, and is also optional. If it is present,
4311 it is the maximum number of bytes that should be skipped by this alignment
4312 directive. If doing the alignment would require skipping more bytes than the
4313 specified maximum, then the alignment is not done at all. You can omit the
4314 fill value (the second argument) entirely by simply using two commas after the
4315 required alignment; this can be useful if you want the alignment to be filled
4316 with no-op instructions when appropriate.
4318 The way the required alignment is specified varies from system to system.
4319 For the arc, hppa, i386 using ELF, i860, iq2000, m68k, or32,
4320 s390, sparc, tic4x, tic80 and xtensa, the first expression is the
4321 alignment request in bytes. For example @samp{.align 8} advances
4322 the location counter until it is a multiple of 8. If the location counter
4323 is already a multiple of 8, no change is needed. For the tic54x, the
4324 first expression is the alignment request in words.
4326 For other systems, including ppc, i386 using a.out format, arm and
4327 strongarm, it is the
4328 number of low-order zero bits the location counter must have after
4329 advancement. For example @samp{.align 3} advances the location
4330 counter until it a multiple of 8. If the location counter is already a
4331 multiple of 8, no change is needed.
4333 This inconsistency is due to the different behaviors of the various
4334 native assemblers for these systems which GAS must emulate.
4335 GAS also provides @code{.balign} and @code{.p2align} directives,
4336 described later, which have a consistent behavior across all
4337 architectures (but are specific to GAS).
4340 @section @code{.altmacro}
4341 Enable alternate macro mode, enabling:
4344 @item LOCAL @var{name} [ , @dots{} ]
4345 One additional directive, @code{LOCAL}, is available. It is used to
4346 generate a string replacement for each of the @var{name} arguments, and
4347 replace any instances of @var{name} in each macro expansion. The
4348 replacement string is unique in the assembly, and different for each
4349 separate macro expansion. @code{LOCAL} allows you to write macros that
4350 define symbols, without fear of conflict between separate macro expansions.
4352 @item String delimiters
4353 You can write strings delimited in these other ways besides
4354 @code{"@var{string}"}:
4357 @item '@var{string}'
4358 You can delimit strings with single-quote characters.
4360 @item <@var{string}>
4361 You can delimit strings with matching angle brackets.
4364 @item single-character string escape
4365 To include any single character literally in a string (even if the
4366 character would otherwise have some special meaning), you can prefix the
4367 character with @samp{!} (an exclamation mark). For example, you can
4368 write @samp{<4.3 !> 5.4!!>} to get the literal text @samp{4.3 > 5.4!}.
4370 @item Expression results as strings
4371 You can write @samp{%@var{expr}} to evaluate the expression @var{expr}
4372 and use the result as a string.
4376 @section @code{.ascii "@var{string}"}@dots{}
4378 @cindex @code{ascii} directive
4379 @cindex string literals
4380 @code{.ascii} expects zero or more string literals (@pxref{Strings})
4381 separated by commas. It assembles each string (with no automatic
4382 trailing zero byte) into consecutive addresses.
4385 @section @code{.asciz "@var{string}"}@dots{}
4387 @cindex @code{asciz} directive
4388 @cindex zero-terminated strings
4389 @cindex null-terminated strings
4390 @code{.asciz} is just like @code{.ascii}, but each string is followed by
4391 a zero byte. The ``z'' in @samp{.asciz} stands for ``zero''.
4394 @section @code{.balign[wl] @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
4396 @cindex padding the location counter given number of bytes
4397 @cindex @code{balign} directive
4398 Pad the location counter (in the current subsection) to a particular
4399 storage boundary. The first expression (which must be absolute) is the
4400 alignment request in bytes. For example @samp{.balign 8} advances
4401 the location counter until it is a multiple of 8. If the location counter
4402 is already a multiple of 8, no change is needed.
4404 The second expression (also absolute) gives the fill value to be stored in the
4405 padding bytes. It (and the comma) may be omitted. If it is omitted, the
4406 padding bytes are normally zero. However, on some systems, if the section is
4407 marked as containing code and the fill value is omitted, the space is filled
4408 with no-op instructions.
4410 The third expression is also absolute, and is also optional. If it is present,
4411 it is the maximum number of bytes that should be skipped by this alignment
4412 directive. If doing the alignment would require skipping more bytes than the
4413 specified maximum, then the alignment is not done at all. You can omit the
4414 fill value (the second argument) entirely by simply using two commas after the
4415 required alignment; this can be useful if you want the alignment to be filled
4416 with no-op instructions when appropriate.
4418 @cindex @code{balignw} directive
4419 @cindex @code{balignl} directive
4420 The @code{.balignw} and @code{.balignl} directives are variants of the
4421 @code{.balign} directive. The @code{.balignw} directive treats the fill
4422 pattern as a two byte word value. The @code{.balignl} directives treats the
4423 fill pattern as a four byte longword value. For example, @code{.balignw
4424 4,0x368d} will align to a multiple of 4. If it skips two bytes, they will be
4425 filled in with the value 0x368d (the exact placement of the bytes depends upon
4426 the endianness of the processor). If it skips 1 or 3 bytes, the fill value is
4429 @node Bundle directives
4430 @section @code{.bundle_align_mode @var{abs-expr}}
4431 @cindex @code{bundle_align_mode} directive
4433 @cindex instruction bundle
4434 @cindex aligned instruction bundle
4435 @code{.bundle_align_mode} enables or disables @dfn{aligned instruction
4436 bundle} mode. In this mode, sequences of adjacent instructions are grouped
4437 into fixed-sized @dfn{bundles}. If the argument is zero, this mode is
4438 disabled (which is the default state). If the argument it not zero, it
4439 gives the size of an instruction bundle as a power of two (as for the
4440 @code{.p2align} directive, @pxref{P2align}).
4442 For some targets, it's an ABI requirement that no instruction may span a
4443 certain aligned boundary. A @dfn{bundle} is simply a sequence of
4444 instructions that starts on an aligned boundary. For example, if
4445 @var{abs-expr} is @code{5} then the bundle size is 32, so each aligned
4446 chunk of 32 bytes is a bundle. When aligned instruction bundle mode is in
4447 effect, no single instruction may span a boundary between bundles. If an
4448 instruction would start too close to the end of a bundle for the length of
4449 that particular instruction to fit within the bundle, then the space at the
4450 end of that bundle is filled with no-op instructions so the instruction
4451 starts in the next bundle. As a corollary, it's an error if any single
4452 instruction's encoding is longer than the bundle size.
4454 @section @code{.bundle_lock} and @code{.bundle_unlock}
4455 @cindex @code{bundle_lock} directive
4456 @cindex @code{bundle_unlock} directive
4457 The @code{.bundle_lock} and directive @code{.bundle_unlock} directives
4458 allow explicit control over instruction bundle padding. These directives
4459 are only valid when @code{.bundle_align_mode} has been used to enable
4460 aligned instruction bundle mode. It's an error if they appear when
4461 @code{.bundle_align_mode} has not been used at all, or when the last
4462 directive was @w{@code{.bundle_align_mode 0}}.
4464 @cindex bundle-locked
4465 For some targets, it's an ABI requirement that certain instructions may
4466 appear only as part of specified permissible sequences of multiple
4467 instructions, all within the same bundle. A pair of @code{.bundle_lock}
4468 and @code{.bundle_unlock} directives define a @dfn{bundle-locked}
4469 instruction sequence. For purposes of aligned instruction bundle mode, a
4470 sequence starting with @code{.bundle_lock} and ending with
4471 @code{.bundle_unlock} is treated as a single instruction. That is, the
4472 entire sequence must fit into a single bundle and may not span a bundle
4473 boundary. If necessary, no-op instructions will be inserted before the
4474 first instruction of the sequence so that the whole sequence starts on an
4475 aligned bundle boundary. It's an error if the sequence is longer than the
4478 For convenience when using @code{.bundle_lock} and @code{.bundle_unlock}
4479 inside assembler macros (@pxref{Macro}), bundle-locked sequences may be
4480 nested. That is, a second @code{.bundle_lock} directive before the next
4481 @code{.bundle_unlock} directive has no effect except that it must be
4482 matched by another closing @code{.bundle_unlock} so that there is the
4483 same number of @code{.bundle_lock} and @code{.bundle_unlock} directives.
4486 @section @code{.byte @var{expressions}}
4488 @cindex @code{byte} directive
4489 @cindex integers, one byte
4490 @code{.byte} expects zero or more expressions, separated by commas.
4491 Each expression is assembled into the next byte.
4493 @node CFI directives
4494 @section @code{.cfi_sections @var{section_list}}
4495 @cindex @code{cfi_sections} directive
4496 @code{.cfi_sections} may be used to specify whether CFI directives
4497 should emit @code{.eh_frame} section and/or @code{.debug_frame} section.
4498 If @var{section_list} is @code{.eh_frame}, @code{.eh_frame} is emitted,
4499 if @var{section_list} is @code{.debug_frame}, @code{.debug_frame} is emitted.
4500 To emit both use @code{.eh_frame, .debug_frame}. The default if this
4501 directive is not used is @code{.cfi_sections .eh_frame}.
4503 @section @code{.cfi_startproc [simple]}
4504 @cindex @code{cfi_startproc} directive
4505 @code{.cfi_startproc} is used at the beginning of each function that
4506 should have an entry in @code{.eh_frame}. It initializes some internal
4507 data structures. Don't forget to close the function by
4508 @code{.cfi_endproc}.
4510 Unless @code{.cfi_startproc} is used along with parameter @code{simple}
4511 it also emits some architecture dependent initial CFI instructions.
4513 @section @code{.cfi_endproc}
4514 @cindex @code{cfi_endproc} directive
4515 @code{.cfi_endproc} is used at the end of a function where it closes its
4516 unwind entry previously opened by
4517 @code{.cfi_startproc}, and emits it to @code{.eh_frame}.
4519 @section @code{.cfi_personality @var{encoding} [, @var{exp}]}
4520 @code{.cfi_personality} defines personality routine and its encoding.
4521 @var{encoding} must be a constant determining how the personality
4522 should be encoded. If it is 255 (@code{DW_EH_PE_omit}), second
4523 argument is not present, otherwise second argument should be
4524 a constant or a symbol name. When using indirect encodings,
4525 the symbol provided should be the location where personality
4526 can be loaded from, not the personality routine itself.
4527 The default after @code{.cfi_startproc} is @code{.cfi_personality 0xff},
4528 no personality routine.
4530 @section @code{.cfi_lsda @var{encoding} [, @var{exp}]}
4531 @code{.cfi_lsda} defines LSDA and its encoding.
4532 @var{encoding} must be a constant determining how the LSDA
4533 should be encoded. If it is 255 (@code{DW_EH_PE_omit}), second
4534 argument is not present, otherwise second argument should be a constant
4535 or a symbol name. The default after @code{.cfi_startproc} is @code{.cfi_lsda 0xff},
4538 @section @code{.cfi_def_cfa @var{register}, @var{offset}}
4539 @code{.cfi_def_cfa} defines a rule for computing CFA as: @i{take
4540 address from @var{register} and add @var{offset} to it}.
4542 @section @code{.cfi_def_cfa_register @var{register}}
4543 @code{.cfi_def_cfa_register} modifies a rule for computing CFA. From
4544 now on @var{register} will be used instead of the old one. Offset
4547 @section @code{.cfi_def_cfa_offset @var{offset}}
4548 @code{.cfi_def_cfa_offset} modifies a rule for computing CFA. Register
4549 remains the same, but @var{offset} is new. Note that it is the
4550 absolute offset that will be added to a defined register to compute
4553 @section @code{.cfi_adjust_cfa_offset @var{offset}}
4554 Same as @code{.cfi_def_cfa_offset} but @var{offset} is a relative
4555 value that is added/substracted from the previous offset.
4557 @section @code{.cfi_offset @var{register}, @var{offset}}
4558 Previous value of @var{register} is saved at offset @var{offset} from
4561 @section @code{.cfi_rel_offset @var{register}, @var{offset}}
4562 Previous value of @var{register} is saved at offset @var{offset} from
4563 the current CFA register. This is transformed to @code{.cfi_offset}
4564 using the known displacement of the CFA register from the CFA.
4565 This is often easier to use, because the number will match the
4566 code it's annotating.
4568 @section @code{.cfi_register @var{register1}, @var{register2}}
4569 Previous value of @var{register1} is saved in register @var{register2}.
4571 @section @code{.cfi_restore @var{register}}
4572 @code{.cfi_restore} says that the rule for @var{register} is now the
4573 same as it was at the beginning of the function, after all initial
4574 instruction added by @code{.cfi_startproc} were executed.
4576 @section @code{.cfi_undefined @var{register}}
4577 From now on the previous value of @var{register} can't be restored anymore.
4579 @section @code{.cfi_same_value @var{register}}
4580 Current value of @var{register} is the same like in the previous frame,
4581 i.e. no restoration needed.
4583 @section @code{.cfi_remember_state},
4584 First save all current rules for all registers by @code{.cfi_remember_state},
4585 then totally screw them up by subsequent @code{.cfi_*} directives and when
4586 everything is hopelessly bad, use @code{.cfi_restore_state} to restore
4587 the previous saved state.
4589 @section @code{.cfi_return_column @var{register}}
4590 Change return column @var{register}, i.e. the return address is either
4591 directly in @var{register} or can be accessed by rules for @var{register}.
4593 @section @code{.cfi_signal_frame}
4594 Mark current function as signal trampoline.
4596 @section @code{.cfi_window_save}
4597 SPARC register window has been saved.
4599 @section @code{.cfi_escape} @var{expression}[, @dots{}]
4600 Allows the user to add arbitrary bytes to the unwind info. One
4601 might use this to add OS-specific CFI opcodes, or generic CFI
4602 opcodes that GAS does not yet support.
4604 @section @code{.cfi_val_encoded_addr @var{register}, @var{encoding}, @var{label}}
4605 The current value of @var{register} is @var{label}. The value of @var{label}
4606 will be encoded in the output file according to @var{encoding}; see the
4607 description of @code{.cfi_personality} for details on this encoding.
4609 The usefulness of equating a register to a fixed label is probably
4610 limited to the return address register. Here, it can be useful to
4611 mark a code segment that has only one return address which is reached
4612 by a direct branch and no copy of the return address exists in memory
4613 or another register.
4616 @section @code{.comm @var{symbol} , @var{length} }
4618 @cindex @code{comm} directive
4619 @cindex symbol, common
4620 @code{.comm} declares a common symbol named @var{symbol}. When linking, a
4621 common symbol in one object file may be merged with a defined or common symbol
4622 of the same name in another object file. If @code{@value{LD}} does not see a
4623 definition for the symbol--just one or more common symbols--then it will
4624 allocate @var{length} bytes of uninitialized memory. @var{length} must be an
4625 absolute expression. If @code{@value{LD}} sees multiple common symbols with
4626 the same name, and they do not all have the same size, it will allocate space
4627 using the largest size.
4630 When using ELF or (as a GNU extension) PE, the @code{.comm} directive takes
4631 an optional third argument. This is the desired alignment of the symbol,
4632 specified for ELF as a byte boundary (for example, an alignment of 16 means
4633 that the least significant 4 bits of the address should be zero), and for PE
4634 as a power of two (for example, an alignment of 5 means aligned to a 32-byte
4635 boundary). The alignment must be an absolute expression, and it must be a
4636 power of two. If @code{@value{LD}} allocates uninitialized memory for the
4637 common symbol, it will use the alignment when placing the symbol. If no
4638 alignment is specified, @command{@value{AS}} will set the alignment to the
4639 largest power of two less than or equal to the size of the symbol, up to a
4640 maximum of 16 on ELF, or the default section alignment of 4 on PE@footnote{This
4641 is not the same as the executable image file alignment controlled by @code{@value{LD}}'s
4642 @samp{--section-alignment} option; image file sections in PE are aligned to
4643 multiples of 4096, which is far too large an alignment for ordinary variables.
4644 It is rather the default alignment for (non-debug) sections within object
4645 (@samp{*.o}) files, which are less strictly aligned.}.
4649 The syntax for @code{.comm} differs slightly on the HPPA. The syntax is
4650 @samp{@var{symbol} .comm, @var{length}}; @var{symbol} is optional.
4654 @section @code{.data @var{subsection}}
4656 @cindex @code{data} directive
4657 @code{.data} tells @command{@value{AS}} to assemble the following statements onto the
4658 end of the data subsection numbered @var{subsection} (which is an
4659 absolute expression). If @var{subsection} is omitted, it defaults
4664 @section @code{.def @var{name}}
4666 @cindex @code{def} directive
4667 @cindex COFF symbols, debugging
4668 @cindex debugging COFF symbols
4669 Begin defining debugging information for a symbol @var{name}; the
4670 definition extends until the @code{.endef} directive is encountered.
4673 This directive is only observed when @command{@value{AS}} is configured for COFF
4674 format output; when producing @code{b.out}, @samp{.def} is recognized,
4681 @section @code{.desc @var{symbol}, @var{abs-expression}}
4683 @cindex @code{desc} directive
4684 @cindex COFF symbol descriptor
4685 @cindex symbol descriptor, COFF
4686 This directive sets the descriptor of the symbol (@pxref{Symbol Attributes})
4687 to the low 16 bits of an absolute expression.
4690 The @samp{.desc} directive is not available when @command{@value{AS}} is
4691 configured for COFF output; it is only for @code{a.out} or @code{b.out}
4692 object format. For the sake of compatibility, @command{@value{AS}} accepts
4693 it, but produces no output, when configured for COFF.
4699 @section @code{.dim}
4701 @cindex @code{dim} directive
4702 @cindex COFF auxiliary symbol information
4703 @cindex auxiliary symbol information, COFF
4704 This directive is generated by compilers to include auxiliary debugging
4705 information in the symbol table. It is only permitted inside
4706 @code{.def}/@code{.endef} pairs.
4709 @samp{.dim} is only meaningful when generating COFF format output; when
4710 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
4716 @section @code{.double @var{flonums}}
4718 @cindex @code{double} directive
4719 @cindex floating point numbers (double)
4720 @code{.double} expects zero or more flonums, separated by commas. It
4721 assembles floating point numbers.
4723 The exact kind of floating point numbers emitted depends on how
4724 @command{@value{AS}} is configured. @xref{Machine Dependencies}.
4728 On the @value{TARGET} family @samp{.double} emits 64-bit floating-point numbers
4729 in @sc{ieee} format.
4734 @section @code{.eject}
4736 @cindex @code{eject} directive
4737 @cindex new page, in listings
4738 @cindex page, in listings
4739 @cindex listing control: new page
4740 Force a page break at this point, when generating assembly listings.
4743 @section @code{.else}
4745 @cindex @code{else} directive
4746 @code{.else} is part of the @command{@value{AS}} support for conditional
4747 assembly; see @ref{If,,@code{.if}}. It marks the beginning of a section
4748 of code to be assembled if the condition for the preceding @code{.if}
4752 @section @code{.elseif}
4754 @cindex @code{elseif} directive
4755 @code{.elseif} is part of the @command{@value{AS}} support for conditional
4756 assembly; see @ref{If,,@code{.if}}. It is shorthand for beginning a new
4757 @code{.if} block that would otherwise fill the entire @code{.else} section.
4760 @section @code{.end}
4762 @cindex @code{end} directive
4763 @code{.end} marks the end of the assembly file. @command{@value{AS}} does not
4764 process anything in the file past the @code{.end} directive.
4768 @section @code{.endef}
4770 @cindex @code{endef} directive
4771 This directive flags the end of a symbol definition begun with
4775 @samp{.endef} is only meaningful when generating COFF format output; if
4776 @command{@value{AS}} is configured to generate @code{b.out}, it accepts this
4777 directive but ignores it.
4782 @section @code{.endfunc}
4783 @cindex @code{endfunc} directive
4784 @code{.endfunc} marks the end of a function specified with @code{.func}.
4787 @section @code{.endif}
4789 @cindex @code{endif} directive
4790 @code{.endif} is part of the @command{@value{AS}} support for conditional assembly;
4791 it marks the end of a block of code that is only assembled
4792 conditionally. @xref{If,,@code{.if}}.
4795 @section @code{.equ @var{symbol}, @var{expression}}
4797 @cindex @code{equ} directive
4798 @cindex assigning values to symbols
4799 @cindex symbols, assigning values to
4800 This directive sets the value of @var{symbol} to @var{expression}.
4801 It is synonymous with @samp{.set}; see @ref{Set,,@code{.set}}.
4804 The syntax for @code{equ} on the HPPA is
4805 @samp{@var{symbol} .equ @var{expression}}.
4809 The syntax for @code{equ} on the Z80 is
4810 @samp{@var{symbol} equ @var{expression}}.
4811 On the Z80 it is an eror if @var{symbol} is already defined,
4812 but the symbol is not protected from later redefinition.
4813 Compare @ref{Equiv}.
4817 @section @code{.equiv @var{symbol}, @var{expression}}
4818 @cindex @code{equiv} directive
4819 The @code{.equiv} directive is like @code{.equ} and @code{.set}, except that
4820 the assembler will signal an error if @var{symbol} is already defined. Note a
4821 symbol which has been referenced but not actually defined is considered to be
4824 Except for the contents of the error message, this is roughly equivalent to
4831 plus it protects the symbol from later redefinition.
4834 @section @code{.eqv @var{symbol}, @var{expression}}
4835 @cindex @code{eqv} directive
4836 The @code{.eqv} directive is like @code{.equiv}, but no attempt is made to
4837 evaluate the expression or any part of it immediately. Instead each time
4838 the resulting symbol is used in an expression, a snapshot of its current
4842 @section @code{.err}
4843 @cindex @code{err} directive
4844 If @command{@value{AS}} assembles a @code{.err} directive, it will print an error
4845 message and, unless the @option{-Z} option was used, it will not generate an
4846 object file. This can be used to signal an error in conditionally compiled code.
4849 @section @code{.error "@var{string}"}
4850 @cindex error directive
4852 Similarly to @code{.err}, this directive emits an error, but you can specify a
4853 string that will be emitted as the error message. If you don't specify the
4854 message, it defaults to @code{".error directive invoked in source file"}.
4855 @xref{Errors, ,Error and Warning Messages}.
4858 .error "This code has not been assembled and tested."
4862 @section @code{.exitm}
4863 Exit early from the current macro definition. @xref{Macro}.
4866 @section @code{.extern}
4868 @cindex @code{extern} directive
4869 @code{.extern} is accepted in the source program---for compatibility
4870 with other assemblers---but it is ignored. @command{@value{AS}} treats
4871 all undefined symbols as external.
4874 @section @code{.fail @var{expression}}
4876 @cindex @code{fail} directive
4877 Generates an error or a warning. If the value of the @var{expression} is 500
4878 or more, @command{@value{AS}} will print a warning message. If the value is less
4879 than 500, @command{@value{AS}} will print an error message. The message will
4880 include the value of @var{expression}. This can occasionally be useful inside
4881 complex nested macros or conditional assembly.
4884 @section @code{.file}
4885 @cindex @code{file} directive
4887 @ifclear no-file-dir
4888 There are two different versions of the @code{.file} directive. Targets
4889 that support DWARF2 line number information use the DWARF2 version of
4890 @code{.file}. Other targets use the default version.
4892 @subheading Default Version
4894 @cindex logical file name
4895 @cindex file name, logical
4896 This version of the @code{.file} directive tells @command{@value{AS}} that we
4897 are about to start a new logical file. The syntax is:
4903 @var{string} is the new file name. In general, the filename is
4904 recognized whether or not it is surrounded by quotes @samp{"}; but if you wish
4905 to specify an empty file name, you must give the quotes--@code{""}. This
4906 statement may go away in future: it is only recognized to be compatible with
4907 old @command{@value{AS}} programs.
4909 @subheading DWARF2 Version
4912 When emitting DWARF2 line number information, @code{.file} assigns filenames
4913 to the @code{.debug_line} file name table. The syntax is:
4916 .file @var{fileno} @var{filename}
4919 The @var{fileno} operand should be a unique positive integer to use as the
4920 index of the entry in the table. The @var{filename} operand is a C string
4923 The detail of filename indices is exposed to the user because the filename
4924 table is shared with the @code{.debug_info} section of the DWARF2 debugging
4925 information, and thus the user must know the exact indices that table
4929 @section @code{.fill @var{repeat} , @var{size} , @var{value}}
4931 @cindex @code{fill} directive
4932 @cindex writing patterns in memory
4933 @cindex patterns, writing in memory
4934 @var{repeat}, @var{size} and @var{value} are absolute expressions.
4935 This emits @var{repeat} copies of @var{size} bytes. @var{Repeat}
4936 may be zero or more. @var{Size} may be zero or more, but if it is
4937 more than 8, then it is deemed to have the value 8, compatible with
4938 other people's assemblers. The contents of each @var{repeat} bytes
4939 is taken from an 8-byte number. The highest order 4 bytes are
4940 zero. The lowest order 4 bytes are @var{value} rendered in the
4941 byte-order of an integer on the computer @command{@value{AS}} is assembling for.
4942 Each @var{size} bytes in a repetition is taken from the lowest order
4943 @var{size} bytes of this number. Again, this bizarre behavior is
4944 compatible with other people's assemblers.
4946 @var{size} and @var{value} are optional.
4947 If the second comma and @var{value} are absent, @var{value} is
4948 assumed zero. If the first comma and following tokens are absent,
4949 @var{size} is assumed to be 1.
4952 @section @code{.float @var{flonums}}
4954 @cindex floating point numbers (single)
4955 @cindex @code{float} directive
4956 This directive assembles zero or more flonums, separated by commas. It
4957 has the same effect as @code{.single}.
4959 The exact kind of floating point numbers emitted depends on how
4960 @command{@value{AS}} is configured.
4961 @xref{Machine Dependencies}.
4965 On the @value{TARGET} family, @code{.float} emits 32-bit floating point numbers
4966 in @sc{ieee} format.
4971 @section @code{.func @var{name}[,@var{label}]}
4972 @cindex @code{func} directive
4973 @code{.func} emits debugging information to denote function @var{name}, and
4974 is ignored unless the file is assembled with debugging enabled.
4975 Only @samp{--gstabs[+]} is currently supported.
4976 @var{label} is the entry point of the function and if omitted @var{name}
4977 prepended with the @samp{leading char} is used.
4978 @samp{leading char} is usually @code{_} or nothing, depending on the target.
4979 All functions are currently defined to have @code{void} return type.
4980 The function must be terminated with @code{.endfunc}.
4983 @section @code{.global @var{symbol}}, @code{.globl @var{symbol}}
4985 @cindex @code{global} directive
4986 @cindex symbol, making visible to linker
4987 @code{.global} makes the symbol visible to @code{@value{LD}}. If you define
4988 @var{symbol} in your partial program, its value is made available to
4989 other partial programs that are linked with it. Otherwise,
4990 @var{symbol} takes its attributes from a symbol of the same name
4991 from another file linked into the same program.
4993 Both spellings (@samp{.globl} and @samp{.global}) are accepted, for
4994 compatibility with other assemblers.
4997 On the HPPA, @code{.global} is not always enough to make it accessible to other
4998 partial programs. You may need the HPPA-only @code{.EXPORT} directive as well.
4999 @xref{HPPA Directives, ,HPPA Assembler Directives}.
5004 @section @code{.gnu_attribute @var{tag},@var{value}}
5005 Record a @sc{gnu} object attribute for this file. @xref{Object Attributes}.
5008 @section @code{.hidden @var{names}}
5010 @cindex @code{hidden} directive
5012 This is one of the ELF visibility directives. The other two are
5013 @code{.internal} (@pxref{Internal,,@code{.internal}}) and
5014 @code{.protected} (@pxref{Protected,,@code{.protected}}).
5016 This directive overrides the named symbols default visibility (which is set by
5017 their binding: local, global or weak). The directive sets the visibility to
5018 @code{hidden} which means that the symbols are not visible to other components.
5019 Such symbols are always considered to be @code{protected} as well.
5023 @section @code{.hword @var{expressions}}
5025 @cindex @code{hword} directive
5026 @cindex integers, 16-bit
5027 @cindex numbers, 16-bit
5028 @cindex sixteen bit integers
5029 This expects zero or more @var{expressions}, and emits
5030 a 16 bit number for each.
5033 This directive is a synonym for @samp{.short}; depending on the target
5034 architecture, it may also be a synonym for @samp{.word}.
5038 This directive is a synonym for @samp{.short}.
5041 This directive is a synonym for both @samp{.short} and @samp{.word}.
5046 @section @code{.ident}
5048 @cindex @code{ident} directive
5050 This directive is used by some assemblers to place tags in object files. The
5051 behavior of this directive varies depending on the target. When using the
5052 a.out object file format, @command{@value{AS}} simply accepts the directive for
5053 source-file compatibility with existing assemblers, but does not emit anything
5054 for it. When using COFF, comments are emitted to the @code{.comment} or
5055 @code{.rdata} section, depending on the target. When using ELF, comments are
5056 emitted to the @code{.comment} section.
5059 @section @code{.if @var{absolute expression}}
5061 @cindex conditional assembly
5062 @cindex @code{if} directive
5063 @code{.if} marks the beginning of a section of code which is only
5064 considered part of the source program being assembled if the argument
5065 (which must be an @var{absolute expression}) is non-zero. The end of
5066 the conditional section of code must be marked by @code{.endif}
5067 (@pxref{Endif,,@code{.endif}}); optionally, you may include code for the
5068 alternative condition, flagged by @code{.else} (@pxref{Else,,@code{.else}}).
5069 If you have several conditions to check, @code{.elseif} may be used to avoid
5070 nesting blocks if/else within each subsequent @code{.else} block.
5072 The following variants of @code{.if} are also supported:
5074 @cindex @code{ifdef} directive
5075 @item .ifdef @var{symbol}
5076 Assembles the following section of code if the specified @var{symbol}
5077 has been defined. Note a symbol which has been referenced but not yet defined
5078 is considered to be undefined.
5080 @cindex @code{ifb} directive
5081 @item .ifb @var{text}
5082 Assembles the following section of code if the operand is blank (empty).
5084 @cindex @code{ifc} directive
5085 @item .ifc @var{string1},@var{string2}
5086 Assembles the following section of code if the two strings are the same. The
5087 strings may be optionally quoted with single quotes. If they are not quoted,
5088 the first string stops at the first comma, and the second string stops at the
5089 end of the line. Strings which contain whitespace should be quoted. The
5090 string comparison is case sensitive.
5092 @cindex @code{ifeq} directive
5093 @item .ifeq @var{absolute expression}
5094 Assembles the following section of code if the argument is zero.
5096 @cindex @code{ifeqs} directive
5097 @item .ifeqs @var{string1},@var{string2}
5098 Another form of @code{.ifc}. The strings must be quoted using double quotes.
5100 @cindex @code{ifge} directive
5101 @item .ifge @var{absolute expression}
5102 Assembles the following section of code if the argument is greater than or
5105 @cindex @code{ifgt} directive
5106 @item .ifgt @var{absolute expression}
5107 Assembles the following section of code if the argument is greater than zero.
5109 @cindex @code{ifle} directive
5110 @item .ifle @var{absolute expression}
5111 Assembles the following section of code if the argument is less than or equal
5114 @cindex @code{iflt} directive
5115 @item .iflt @var{absolute expression}
5116 Assembles the following section of code if the argument is less than zero.
5118 @cindex @code{ifnb} directive
5119 @item .ifnb @var{text}
5120 Like @code{.ifb}, but the sense of the test is reversed: this assembles the
5121 following section of code if the operand is non-blank (non-empty).
5123 @cindex @code{ifnc} directive
5124 @item .ifnc @var{string1},@var{string2}.
5125 Like @code{.ifc}, but the sense of the test is reversed: this assembles the
5126 following section of code if the two strings are not the same.
5128 @cindex @code{ifndef} directive
5129 @cindex @code{ifnotdef} directive
5130 @item .ifndef @var{symbol}
5131 @itemx .ifnotdef @var{symbol}
5132 Assembles the following section of code if the specified @var{symbol}
5133 has not been defined. Both spelling variants are equivalent. Note a symbol
5134 which has been referenced but not yet defined is considered to be undefined.
5136 @cindex @code{ifne} directive
5137 @item .ifne @var{absolute expression}
5138 Assembles the following section of code if the argument is not equal to zero
5139 (in other words, this is equivalent to @code{.if}).
5141 @cindex @code{ifnes} directive
5142 @item .ifnes @var{string1},@var{string2}
5143 Like @code{.ifeqs}, but the sense of the test is reversed: this assembles the
5144 following section of code if the two strings are not the same.
5148 @section @code{.incbin "@var{file}"[,@var{skip}[,@var{count}]]}
5150 @cindex @code{incbin} directive
5151 @cindex binary files, including
5152 The @code{incbin} directive includes @var{file} verbatim at the current
5153 location. You can control the search paths used with the @samp{-I} command-line
5154 option (@pxref{Invoking,,Command-Line Options}). Quotation marks are required
5157 The @var{skip} argument skips a number of bytes from the start of the
5158 @var{file}. The @var{count} argument indicates the maximum number of bytes to
5159 read. Note that the data is not aligned in any way, so it is the user's
5160 responsibility to make sure that proper alignment is provided both before and
5161 after the @code{incbin} directive.
5164 @section @code{.include "@var{file}"}
5166 @cindex @code{include} directive
5167 @cindex supporting files, including
5168 @cindex files, including
5169 This directive provides a way to include supporting files at specified
5170 points in your source program. The code from @var{file} is assembled as
5171 if it followed the point of the @code{.include}; when the end of the
5172 included file is reached, assembly of the original file continues. You
5173 can control the search paths used with the @samp{-I} command-line option
5174 (@pxref{Invoking,,Command-Line Options}). Quotation marks are required
5178 @section @code{.int @var{expressions}}
5180 @cindex @code{int} directive
5181 @cindex integers, 32-bit
5182 Expect zero or more @var{expressions}, of any section, separated by commas.
5183 For each expression, emit a number that, at run time, is the value of that
5184 expression. The byte order and bit size of the number depends on what kind
5185 of target the assembly is for.
5189 On most forms of the H8/300, @code{.int} emits 16-bit
5190 integers. On the H8/300H and the Renesas SH, however, @code{.int} emits
5197 @section @code{.internal @var{names}}
5199 @cindex @code{internal} directive
5201 This is one of the ELF visibility directives. The other two are
5202 @code{.hidden} (@pxref{Hidden,,@code{.hidden}}) and
5203 @code{.protected} (@pxref{Protected,,@code{.protected}}).
5205 This directive overrides the named symbols default visibility (which is set by
5206 their binding: local, global or weak). The directive sets the visibility to
5207 @code{internal} which means that the symbols are considered to be @code{hidden}
5208 (i.e., not visible to other components), and that some extra, processor specific
5209 processing must also be performed upon the symbols as well.
5213 @section @code{.irp @var{symbol},@var{values}}@dots{}
5215 @cindex @code{irp} directive
5216 Evaluate a sequence of statements assigning different values to @var{symbol}.
5217 The sequence of statements starts at the @code{.irp} directive, and is
5218 terminated by an @code{.endr} directive. For each @var{value}, @var{symbol} is
5219 set to @var{value}, and the sequence of statements is assembled. If no
5220 @var{value} is listed, the sequence of statements is assembled once, with
5221 @var{symbol} set to the null string. To refer to @var{symbol} within the
5222 sequence of statements, use @var{\symbol}.
5224 For example, assembling
5232 is equivalent to assembling
5240 For some caveats with the spelling of @var{symbol}, see also @ref{Macro}.
5243 @section @code{.irpc @var{symbol},@var{values}}@dots{}
5245 @cindex @code{irpc} directive
5246 Evaluate a sequence of statements assigning different values to @var{symbol}.
5247 The sequence of statements starts at the @code{.irpc} directive, and is
5248 terminated by an @code{.endr} directive. For each character in @var{value},
5249 @var{symbol} is set to the character, and the sequence of statements is
5250 assembled. If no @var{value} is listed, the sequence of statements is
5251 assembled once, with @var{symbol} set to the null string. To refer to
5252 @var{symbol} within the sequence of statements, use @var{\symbol}.
5254 For example, assembling
5262 is equivalent to assembling
5270 For some caveats with the spelling of @var{symbol}, see also the discussion
5274 @section @code{.lcomm @var{symbol} , @var{length}}
5276 @cindex @code{lcomm} directive
5277 @cindex local common symbols
5278 @cindex symbols, local common
5279 Reserve @var{length} (an absolute expression) bytes for a local common
5280 denoted by @var{symbol}. The section and value of @var{symbol} are
5281 those of the new local common. The addresses are allocated in the bss
5282 section, so that at run-time the bytes start off zeroed. @var{Symbol}
5283 is not declared global (@pxref{Global,,@code{.global}}), so is normally
5284 not visible to @code{@value{LD}}.
5287 Some targets permit a third argument to be used with @code{.lcomm}. This
5288 argument specifies the desired alignment of the symbol in the bss section.
5292 The syntax for @code{.lcomm} differs slightly on the HPPA. The syntax is
5293 @samp{@var{symbol} .lcomm, @var{length}}; @var{symbol} is optional.
5297 @section @code{.lflags}
5299 @cindex @code{lflags} directive (ignored)
5300 @command{@value{AS}} accepts this directive, for compatibility with other
5301 assemblers, but ignores it.
5303 @ifclear no-line-dir
5305 @section @code{.line @var{line-number}}
5307 @cindex @code{line} directive
5308 @cindex logical line number
5310 Change the logical line number. @var{line-number} must be an absolute
5311 expression. The next line has that logical line number. Therefore any other
5312 statements on the current line (after a statement separator character) are
5313 reported as on logical line number @var{line-number} @minus{} 1. One day
5314 @command{@value{AS}} will no longer support this directive: it is recognized only
5315 for compatibility with existing assembler programs.
5318 Even though this is a directive associated with the @code{a.out} or
5319 @code{b.out} object-code formats, @command{@value{AS}} still recognizes it
5320 when producing COFF output, and treats @samp{.line} as though it
5321 were the COFF @samp{.ln} @emph{if} it is found outside a
5322 @code{.def}/@code{.endef} pair.
5324 Inside a @code{.def}, @samp{.line} is, instead, one of the directives
5325 used by compilers to generate auxiliary symbol information for
5330 @section @code{.linkonce [@var{type}]}
5332 @cindex @code{linkonce} directive
5333 @cindex common sections
5334 Mark the current section so that the linker only includes a single copy of it.
5335 This may be used to include the same section in several different object files,
5336 but ensure that the linker will only include it once in the final output file.
5337 The @code{.linkonce} pseudo-op must be used for each instance of the section.
5338 Duplicate sections are detected based on the section name, so it should be
5341 This directive is only supported by a few object file formats; as of this
5342 writing, the only object file format which supports it is the Portable
5343 Executable format used on Windows NT.
5345 The @var{type} argument is optional. If specified, it must be one of the
5346 following strings. For example:
5350 Not all types may be supported on all object file formats.
5354 Silently discard duplicate sections. This is the default.
5357 Warn if there are duplicate sections, but still keep only one copy.
5360 Warn if any of the duplicates have different sizes.
5363 Warn if any of the duplicates do not have exactly the same contents.
5367 @section @code{.list}
5369 @cindex @code{list} directive
5370 @cindex listing control, turning on
5371 Control (in conjunction with the @code{.nolist} directive) whether or
5372 not assembly listings are generated. These two directives maintain an
5373 internal counter (which is zero initially). @code{.list} increments the
5374 counter, and @code{.nolist} decrements it. Assembly listings are
5375 generated whenever the counter is greater than zero.
5377 By default, listings are disabled. When you enable them (with the
5378 @samp{-a} command line option; @pxref{Invoking,,Command-Line Options}),
5379 the initial value of the listing counter is one.
5382 @section @code{.ln @var{line-number}}
5384 @cindex @code{ln} directive
5385 @ifclear no-line-dir
5386 @samp{.ln} is a synonym for @samp{.line}.
5389 Tell @command{@value{AS}} to change the logical line number. @var{line-number}
5390 must be an absolute expression. The next line has that logical
5391 line number, so any other statements on the current line (after a
5392 statement separator character @code{;}) are reported as on logical
5393 line number @var{line-number} @minus{} 1.
5396 This directive is accepted, but ignored, when @command{@value{AS}} is
5397 configured for @code{b.out}; its effect is only associated with COFF
5403 @section @code{.loc @var{fileno} @var{lineno} [@var{column}] [@var{options}]}
5404 @cindex @code{loc} directive
5405 When emitting DWARF2 line number information,
5406 the @code{.loc} directive will add a row to the @code{.debug_line} line
5407 number matrix corresponding to the immediately following assembly
5408 instruction. The @var{fileno}, @var{lineno}, and optional @var{column}
5409 arguments will be applied to the @code{.debug_line} state machine before
5412 The @var{options} are a sequence of the following tokens in any order:
5416 This option will set the @code{basic_block} register in the
5417 @code{.debug_line} state machine to @code{true}.
5420 This option will set the @code{prologue_end} register in the
5421 @code{.debug_line} state machine to @code{true}.
5423 @item epilogue_begin
5424 This option will set the @code{epilogue_begin} register in the
5425 @code{.debug_line} state machine to @code{true}.
5427 @item is_stmt @var{value}
5428 This option will set the @code{is_stmt} register in the
5429 @code{.debug_line} state machine to @code{value}, which must be
5432 @item isa @var{value}
5433 This directive will set the @code{isa} register in the @code{.debug_line}
5434 state machine to @var{value}, which must be an unsigned integer.
5436 @item discriminator @var{value}
5437 This directive will set the @code{discriminator} register in the @code{.debug_line}
5438 state machine to @var{value}, which must be an unsigned integer.
5442 @node Loc_mark_labels
5443 @section @code{.loc_mark_labels @var{enable}}
5444 @cindex @code{loc_mark_labels} directive
5445 When emitting DWARF2 line number information,
5446 the @code{.loc_mark_labels} directive makes the assembler emit an entry
5447 to the @code{.debug_line} line number matrix with the @code{basic_block}
5448 register in the state machine set whenever a code label is seen.
5449 The @var{enable} argument should be either 1 or 0, to enable or disable
5450 this function respectively.
5454 @section @code{.local @var{names}}
5456 @cindex @code{local} directive
5457 This directive, which is available for ELF targets, marks each symbol in
5458 the comma-separated list of @code{names} as a local symbol so that it
5459 will not be externally visible. If the symbols do not already exist,
5460 they will be created.
5462 For targets where the @code{.lcomm} directive (@pxref{Lcomm}) does not
5463 accept an alignment argument, which is the case for most ELF targets,
5464 the @code{.local} directive can be used in combination with @code{.comm}
5465 (@pxref{Comm}) to define aligned local common data.
5469 @section @code{.long @var{expressions}}
5471 @cindex @code{long} directive
5472 @code{.long} is the same as @samp{.int}. @xref{Int,,@code{.int}}.
5475 @c no one seems to know what this is for or whether this description is
5476 @c what it really ought to do
5478 @section @code{.lsym @var{symbol}, @var{expression}}
5480 @cindex @code{lsym} directive
5481 @cindex symbol, not referenced in assembly
5482 @code{.lsym} creates a new symbol named @var{symbol}, but does not put it in
5483 the hash table, ensuring it cannot be referenced by name during the
5484 rest of the assembly. This sets the attributes of the symbol to be
5485 the same as the expression value:
5487 @var{other} = @var{descriptor} = 0
5488 @var{type} = @r{(section of @var{expression})}
5489 @var{value} = @var{expression}
5492 The new symbol is not flagged as external.
5496 @section @code{.macro}
5499 The commands @code{.macro} and @code{.endm} allow you to define macros that
5500 generate assembly output. For example, this definition specifies a macro
5501 @code{sum} that puts a sequence of numbers into memory:
5504 .macro sum from=0, to=5
5513 With that definition, @samp{SUM 0,5} is equivalent to this assembly input:
5525 @item .macro @var{macname}
5526 @itemx .macro @var{macname} @var{macargs} @dots{}
5527 @cindex @code{macro} directive
5528 Begin the definition of a macro called @var{macname}. If your macro
5529 definition requires arguments, specify their names after the macro name,
5530 separated by commas or spaces. You can qualify the macro argument to
5531 indicate whether all invocations must specify a non-blank value (through
5532 @samp{:@code{req}}), or whether it takes all of the remaining arguments
5533 (through @samp{:@code{vararg}}). You can supply a default value for any
5534 macro argument by following the name with @samp{=@var{deflt}}. You
5535 cannot define two macros with the same @var{macname} unless it has been
5536 subject to the @code{.purgem} directive (@pxref{Purgem}) between the two
5537 definitions. For example, these are all valid @code{.macro} statements:
5541 Begin the definition of a macro called @code{comm}, which takes no
5544 @item .macro plus1 p, p1
5545 @itemx .macro plus1 p p1
5546 Either statement begins the definition of a macro called @code{plus1},
5547 which takes two arguments; within the macro definition, write
5548 @samp{\p} or @samp{\p1} to evaluate the arguments.
5550 @item .macro reserve_str p1=0 p2
5551 Begin the definition of a macro called @code{reserve_str}, with two
5552 arguments. The first argument has a default value, but not the second.
5553 After the definition is complete, you can call the macro either as
5554 @samp{reserve_str @var{a},@var{b}} (with @samp{\p1} evaluating to
5555 @var{a} and @samp{\p2} evaluating to @var{b}), or as @samp{reserve_str
5556 ,@var{b}} (with @samp{\p1} evaluating as the default, in this case
5557 @samp{0}, and @samp{\p2} evaluating to @var{b}).
5559 @item .macro m p1:req, p2=0, p3:vararg
5560 Begin the definition of a macro called @code{m}, with at least three
5561 arguments. The first argument must always have a value specified, but
5562 not the second, which instead has a default value. The third formal
5563 will get assigned all remaining arguments specified at invocation time.
5565 When you call a macro, you can specify the argument values either by
5566 position, or by keyword. For example, @samp{sum 9,17} is equivalent to
5567 @samp{sum to=17, from=9}.
5571 Note that since each of the @var{macargs} can be an identifier exactly
5572 as any other one permitted by the target architecture, there may be
5573 occasional problems if the target hand-crafts special meanings to certain
5574 characters when they occur in a special position. For example, if the colon
5575 (@code{:}) is generally permitted to be part of a symbol name, but the
5576 architecture specific code special-cases it when occurring as the final
5577 character of a symbol (to denote a label), then the macro parameter
5578 replacement code will have no way of knowing that and consider the whole
5579 construct (including the colon) an identifier, and check only this
5580 identifier for being the subject to parameter substitution. So for example
5581 this macro definition:
5589 might not work as expected. Invoking @samp{label foo} might not create a label
5590 called @samp{foo} but instead just insert the text @samp{\l:} into the
5591 assembler source, probably generating an error about an unrecognised
5594 Similarly problems might occur with the period character (@samp{.})
5595 which is often allowed inside opcode names (and hence identifier names). So
5596 for example constructing a macro to build an opcode from a base name and a
5597 length specifier like this:
5600 .macro opcode base length
5605 and invoking it as @samp{opcode store l} will not create a @samp{store.l}
5606 instruction but instead generate some kind of error as the assembler tries to
5607 interpret the text @samp{\base.\length}.
5609 There are several possible ways around this problem:
5612 @item Insert white space
5613 If it is possible to use white space characters then this is the simplest
5622 @item Use @samp{\()}
5623 The string @samp{\()} can be used to separate the end of a macro argument from
5624 the following text. eg:
5627 .macro opcode base length
5632 @item Use the alternate macro syntax mode
5633 In the alternative macro syntax mode the ampersand character (@samp{&}) can be
5634 used as a separator. eg:
5644 Note: this problem of correctly identifying string parameters to pseudo ops
5645 also applies to the identifiers used in @code{.irp} (@pxref{Irp})
5646 and @code{.irpc} (@pxref{Irpc}) as well.
5649 @cindex @code{endm} directive
5650 Mark the end of a macro definition.
5653 @cindex @code{exitm} directive
5654 Exit early from the current macro definition.
5656 @cindex number of macros executed
5657 @cindex macros, count executed
5659 @command{@value{AS}} maintains a counter of how many macros it has
5660 executed in this pseudo-variable; you can copy that number to your
5661 output with @samp{\@@}, but @emph{only within a macro definition}.
5663 @item LOCAL @var{name} [ , @dots{} ]
5664 @emph{Warning: @code{LOCAL} is only available if you select ``alternate
5665 macro syntax'' with @samp{--alternate} or @code{.altmacro}.}
5666 @xref{Altmacro,,@code{.altmacro}}.
5670 @section @code{.mri @var{val}}
5672 @cindex @code{mri} directive
5673 @cindex MRI mode, temporarily
5674 If @var{val} is non-zero, this tells @command{@value{AS}} to enter MRI mode. If
5675 @var{val} is zero, this tells @command{@value{AS}} to exit MRI mode. This change
5676 affects code assembled until the next @code{.mri} directive, or until the end
5677 of the file. @xref{M, MRI mode, MRI mode}.
5680 @section @code{.noaltmacro}
5681 Disable alternate macro mode. @xref{Altmacro}.
5684 @section @code{.nolist}
5686 @cindex @code{nolist} directive
5687 @cindex listing control, turning off
5688 Control (in conjunction with the @code{.list} directive) whether or
5689 not assembly listings are generated. These two directives maintain an
5690 internal counter (which is zero initially). @code{.list} increments the
5691 counter, and @code{.nolist} decrements it. Assembly listings are
5692 generated whenever the counter is greater than zero.
5695 @section @code{.octa @var{bignums}}
5697 @c FIXME: double size emitted for "octa" on i960, others? Or warn?
5698 @cindex @code{octa} directive
5699 @cindex integer, 16-byte
5700 @cindex sixteen byte integer
5701 This directive expects zero or more bignums, separated by commas. For each
5702 bignum, it emits a 16-byte integer.
5704 The term ``octa'' comes from contexts in which a ``word'' is two bytes;
5705 hence @emph{octa}-word for 16 bytes.
5708 @section @code{.offset @var{loc}}
5710 @cindex @code{offset} directive
5711 Set the location counter to @var{loc} in the absolute section. @var{loc} must
5712 be an absolute expression. This directive may be useful for defining
5713 symbols with absolute values. Do not confuse it with the @code{.org}
5717 @section @code{.org @var{new-lc} , @var{fill}}
5719 @cindex @code{org} directive
5720 @cindex location counter, advancing
5721 @cindex advancing location counter
5722 @cindex current address, advancing
5723 Advance the location counter of the current section to
5724 @var{new-lc}. @var{new-lc} is either an absolute expression or an
5725 expression with the same section as the current subsection. That is,
5726 you can't use @code{.org} to cross sections: if @var{new-lc} has the
5727 wrong section, the @code{.org} directive is ignored. To be compatible
5728 with former assemblers, if the section of @var{new-lc} is absolute,
5729 @command{@value{AS}} issues a warning, then pretends the section of @var{new-lc}
5730 is the same as the current subsection.
5732 @code{.org} may only increase the location counter, or leave it
5733 unchanged; you cannot use @code{.org} to move the location counter
5736 @c double negative used below "not undefined" because this is a specific
5737 @c reference to "undefined" (as SEG_UNKNOWN is called in this manual)
5738 @c section. doc@cygnus.com 18feb91
5739 Because @command{@value{AS}} tries to assemble programs in one pass, @var{new-lc}
5740 may not be undefined. If you really detest this restriction we eagerly await
5741 a chance to share your improved assembler.
5743 Beware that the origin is relative to the start of the section, not
5744 to the start of the subsection. This is compatible with other
5745 people's assemblers.
5747 When the location counter (of the current subsection) is advanced, the
5748 intervening bytes are filled with @var{fill} which should be an
5749 absolute expression. If the comma and @var{fill} are omitted,
5750 @var{fill} defaults to zero.
5753 @section @code{.p2align[wl] @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
5755 @cindex padding the location counter given a power of two
5756 @cindex @code{p2align} directive
5757 Pad the location counter (in the current subsection) to a particular
5758 storage boundary. The first expression (which must be absolute) is the
5759 number of low-order zero bits the location counter must have after
5760 advancement. For example @samp{.p2align 3} advances the location
5761 counter until it a multiple of 8. If the location counter is already a
5762 multiple of 8, no change is needed.
5764 The second expression (also absolute) gives the fill value to be stored in the
5765 padding bytes. It (and the comma) may be omitted. If it is omitted, the
5766 padding bytes are normally zero. However, on some systems, if the section is
5767 marked as containing code and the fill value is omitted, the space is filled
5768 with no-op instructions.
5770 The third expression is also absolute, and is also optional. If it is present,
5771 it is the maximum number of bytes that should be skipped by this alignment
5772 directive. If doing the alignment would require skipping more bytes than the
5773 specified maximum, then the alignment is not done at all. You can omit the
5774 fill value (the second argument) entirely by simply using two commas after the
5775 required alignment; this can be useful if you want the alignment to be filled
5776 with no-op instructions when appropriate.
5778 @cindex @code{p2alignw} directive
5779 @cindex @code{p2alignl} directive
5780 The @code{.p2alignw} and @code{.p2alignl} directives are variants of the
5781 @code{.p2align} directive. The @code{.p2alignw} directive treats the fill
5782 pattern as a two byte word value. The @code{.p2alignl} directives treats the
5783 fill pattern as a four byte longword value. For example, @code{.p2alignw
5784 2,0x368d} will align to a multiple of 4. If it skips two bytes, they will be
5785 filled in with the value 0x368d (the exact placement of the bytes depends upon
5786 the endianness of the processor). If it skips 1 or 3 bytes, the fill value is
5791 @section @code{.popsection}
5793 @cindex @code{popsection} directive
5794 @cindex Section Stack
5795 This is one of the ELF section stack manipulation directives. The others are
5796 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
5797 @code{.pushsection} (@pxref{PushSection}), and @code{.previous}
5800 This directive replaces the current section (and subsection) with the top
5801 section (and subsection) on the section stack. This section is popped off the
5807 @section @code{.previous}
5809 @cindex @code{previous} directive
5810 @cindex Section Stack
5811 This is one of the ELF section stack manipulation directives. The others are
5812 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
5813 @code{.pushsection} (@pxref{PushSection}), and @code{.popsection}
5814 (@pxref{PopSection}).
5816 This directive swaps the current section (and subsection) with most recently
5817 referenced section/subsection pair prior to this one. Multiple
5818 @code{.previous} directives in a row will flip between two sections (and their
5819 subsections). For example:
5831 Will place 0x1234 and 0x9abc into subsection 1 and 0x5678 into subsection 2 of
5837 # Now in section A subsection 1
5841 # Now in section B subsection 0
5844 # Now in section B subsection 1
5847 # Now in section B subsection 0
5851 Will place 0x1234 into section A, 0x5678 and 0xdef0 into subsection 0 of
5852 section B and 0x9abc into subsection 1 of section B.
5854 In terms of the section stack, this directive swaps the current section with
5855 the top section on the section stack.
5859 @section @code{.print @var{string}}
5861 @cindex @code{print} directive
5862 @command{@value{AS}} will print @var{string} on the standard output during
5863 assembly. You must put @var{string} in double quotes.
5867 @section @code{.protected @var{names}}
5869 @cindex @code{protected} directive
5871 This is one of the ELF visibility directives. The other two are
5872 @code{.hidden} (@pxref{Hidden}) and @code{.internal} (@pxref{Internal}).
5874 This directive overrides the named symbols default visibility (which is set by
5875 their binding: local, global or weak). The directive sets the visibility to
5876 @code{protected} which means that any references to the symbols from within the
5877 components that defines them must be resolved to the definition in that
5878 component, even if a definition in another component would normally preempt
5883 @section @code{.psize @var{lines} , @var{columns}}
5885 @cindex @code{psize} directive
5886 @cindex listing control: paper size
5887 @cindex paper size, for listings
5888 Use this directive to declare the number of lines---and, optionally, the
5889 number of columns---to use for each page, when generating listings.
5891 If you do not use @code{.psize}, listings use a default line-count
5892 of 60. You may omit the comma and @var{columns} specification; the
5893 default width is 200 columns.
5895 @command{@value{AS}} generates formfeeds whenever the specified number of
5896 lines is exceeded (or whenever you explicitly request one, using
5899 If you specify @var{lines} as @code{0}, no formfeeds are generated save
5900 those explicitly specified with @code{.eject}.
5903 @section @code{.purgem @var{name}}
5905 @cindex @code{purgem} directive
5906 Undefine the macro @var{name}, so that later uses of the string will not be
5907 expanded. @xref{Macro}.
5911 @section @code{.pushsection @var{name} [, @var{subsection}] [, "@var{flags}"[, @@@var{type}[,@var{arguments}]]]}
5913 @cindex @code{pushsection} directive
5914 @cindex Section Stack
5915 This is one of the ELF section stack manipulation directives. The others are
5916 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
5917 @code{.popsection} (@pxref{PopSection}), and @code{.previous}
5920 This directive pushes the current section (and subsection) onto the
5921 top of the section stack, and then replaces the current section and
5922 subsection with @code{name} and @code{subsection}. The optional
5923 @code{flags}, @code{type} and @code{arguments} are treated the same
5924 as in the @code{.section} (@pxref{Section}) directive.
5928 @section @code{.quad @var{bignums}}
5930 @cindex @code{quad} directive
5931 @code{.quad} expects zero or more bignums, separated by commas. For
5932 each bignum, it emits
5934 an 8-byte integer. If the bignum won't fit in 8 bytes, it prints a
5935 warning message; and just takes the lowest order 8 bytes of the bignum.
5936 @cindex eight-byte integer
5937 @cindex integer, 8-byte
5939 The term ``quad'' comes from contexts in which a ``word'' is two bytes;
5940 hence @emph{quad}-word for 8 bytes.
5943 a 16-byte integer. If the bignum won't fit in 16 bytes, it prints a
5944 warning message; and just takes the lowest order 16 bytes of the bignum.
5945 @cindex sixteen-byte integer
5946 @cindex integer, 16-byte
5950 @section @code{.reloc @var{offset}, @var{reloc_name}[, @var{expression}]}
5952 @cindex @code{reloc} directive
5953 Generate a relocation at @var{offset} of type @var{reloc_name} with value
5954 @var{expression}. If @var{offset} is a number, the relocation is generated in
5955 the current section. If @var{offset} is an expression that resolves to a
5956 symbol plus offset, the relocation is generated in the given symbol's section.
5957 @var{expression}, if present, must resolve to a symbol plus addend or to an
5958 absolute value, but note that not all targets support an addend. e.g. ELF REL
5959 targets such as i386 store an addend in the section contents rather than in the
5960 relocation. This low level interface does not support addends stored in the
5964 @section @code{.rept @var{count}}
5966 @cindex @code{rept} directive
5967 Repeat the sequence of lines between the @code{.rept} directive and the next
5968 @code{.endr} directive @var{count} times.
5970 For example, assembling
5978 is equivalent to assembling
5987 @section @code{.sbttl "@var{subheading}"}
5989 @cindex @code{sbttl} directive
5990 @cindex subtitles for listings
5991 @cindex listing control: subtitle
5992 Use @var{subheading} as the title (third line, immediately after the
5993 title line) when generating assembly listings.
5995 This directive affects subsequent pages, as well as the current page if
5996 it appears within ten lines of the top of a page.
6000 @section @code{.scl @var{class}}
6002 @cindex @code{scl} directive
6003 @cindex symbol storage class (COFF)
6004 @cindex COFF symbol storage class
6005 Set the storage-class value for a symbol. This directive may only be
6006 used inside a @code{.def}/@code{.endef} pair. Storage class may flag
6007 whether a symbol is static or external, or it may record further
6008 symbolic debugging information.
6011 The @samp{.scl} directive is primarily associated with COFF output; when
6012 configured to generate @code{b.out} output format, @command{@value{AS}}
6013 accepts this directive but ignores it.
6019 @section @code{.section @var{name}}
6021 @cindex named section
6022 Use the @code{.section} directive to assemble the following code into a section
6025 This directive is only supported for targets that actually support arbitrarily
6026 named sections; on @code{a.out} targets, for example, it is not accepted, even
6027 with a standard @code{a.out} section name.
6031 @c only print the extra heading if both COFF and ELF are set
6032 @subheading COFF Version
6035 @cindex @code{section} directive (COFF version)
6036 For COFF targets, the @code{.section} directive is used in one of the following
6040 .section @var{name}[, "@var{flags}"]
6041 .section @var{name}[, @var{subsection}]
6044 If the optional argument is quoted, it is taken as flags to use for the
6045 section. Each flag is a single character. The following flags are recognized:
6048 bss section (uninitialized data)
6050 section is not loaded
6056 exclude section from linking
6062 shared section (meaningful for PE targets)
6064 ignored. (For compatibility with the ELF version)
6066 section is not readable (meaningful for PE targets)
6068 single-digit power-of-two section alignment (GNU extension)
6071 If no flags are specified, the default flags depend upon the section name. If
6072 the section name is not recognized, the default will be for the section to be
6073 loaded and writable. Note the @code{n} and @code{w} flags remove attributes
6074 from the section, rather than adding them, so if they are used on their own it
6075 will be as if no flags had been specified at all.
6077 If the optional argument to the @code{.section} directive is not quoted, it is
6078 taken as a subsection number (@pxref{Sub-Sections}).
6083 @c only print the extra heading if both COFF and ELF are set
6084 @subheading ELF Version
6087 @cindex Section Stack
6088 This is one of the ELF section stack manipulation directives. The others are
6089 @code{.subsection} (@pxref{SubSection}), @code{.pushsection}
6090 (@pxref{PushSection}), @code{.popsection} (@pxref{PopSection}), and
6091 @code{.previous} (@pxref{Previous}).
6093 @cindex @code{section} directive (ELF version)
6094 For ELF targets, the @code{.section} directive is used like this:
6097 .section @var{name} [, "@var{flags}"[, @@@var{type}[,@var{flag_specific_arguments}]]]
6100 The optional @var{flags} argument is a quoted string which may contain any
6101 combination of the following characters:
6104 section is allocatable
6106 section is excluded from executable and shared library.
6110 section is executable
6112 section is mergeable
6114 section contains zero terminated strings
6116 section is a member of a section group
6118 section is used for thread-local-storage
6120 section is a member of the previously-current section's group, if any
6123 The optional @var{type} argument may contain one of the following constants:
6126 section contains data
6128 section does not contain data (i.e., section only occupies space)
6130 section contains data which is used by things other than the program
6132 section contains an array of pointers to init functions
6134 section contains an array of pointers to finish functions
6135 @item @@preinit_array
6136 section contains an array of pointers to pre-init functions
6139 Many targets only support the first three section types.
6141 Note on targets where the @code{@@} character is the start of a comment (eg
6142 ARM) then another character is used instead. For example the ARM port uses the
6145 If @var{flags} contains the @code{M} symbol then the @var{type} argument must
6146 be specified as well as an extra argument---@var{entsize}---like this:
6149 .section @var{name} , "@var{flags}"M, @@@var{type}, @var{entsize}
6152 Sections with the @code{M} flag but not @code{S} flag must contain fixed size
6153 constants, each @var{entsize} octets long. Sections with both @code{M} and
6154 @code{S} must contain zero terminated strings where each character is
6155 @var{entsize} bytes long. The linker may remove duplicates within sections with
6156 the same name, same entity size and same flags. @var{entsize} must be an
6157 absolute expression. For sections with both @code{M} and @code{S}, a string
6158 which is a suffix of a larger string is considered a duplicate. Thus
6159 @code{"def"} will be merged with @code{"abcdef"}; A reference to the first
6160 @code{"def"} will be changed to a reference to @code{"abcdef"+3}.
6162 If @var{flags} contains the @code{G} symbol then the @var{type} argument must
6163 be present along with an additional field like this:
6166 .section @var{name} , "@var{flags}"G, @@@var{type}, @var{GroupName}[, @var{linkage}]
6169 The @var{GroupName} field specifies the name of the section group to which this
6170 particular section belongs. The optional linkage field can contain:
6173 indicates that only one copy of this section should be retained
6178 Note: if both the @var{M} and @var{G} flags are present then the fields for
6179 the Merge flag should come first, like this:
6182 .section @var{name} , "@var{flags}"MG, @@@var{type}, @var{entsize}, @var{GroupName}[, @var{linkage}]
6185 If @var{flags} contains the @code{?} symbol then it may not also contain the
6186 @code{G} symbol and the @var{GroupName} or @var{linkage} fields should not be
6187 present. Instead, @code{?} says to consider the section that's current before
6188 this directive. If that section used @code{G}, then the new section will use
6189 @code{G} with those same @var{GroupName} and @var{linkage} fields implicitly.
6190 If not, then the @code{?} symbol has no effect.
6192 If no flags are specified, the default flags depend upon the section name. If
6193 the section name is not recognized, the default will be for the section to have
6194 none of the above flags: it will not be allocated in memory, nor writable, nor
6195 executable. The section will contain data.
6197 For ELF targets, the assembler supports another type of @code{.section}
6198 directive for compatibility with the Solaris assembler:
6201 .section "@var{name}"[, @var{flags}...]
6204 Note that the section name is quoted. There may be a sequence of comma
6208 section is allocatable
6212 section is executable
6214 section is excluded from executable and shared library.
6216 section is used for thread local storage
6219 This directive replaces the current section and subsection. See the
6220 contents of the gas testsuite directory @code{gas/testsuite/gas/elf} for
6221 some examples of how this directive and the other section stack directives
6227 @section @code{.set @var{symbol}, @var{expression}}
6229 @cindex @code{set} directive
6230 @cindex symbol value, setting
6231 Set the value of @var{symbol} to @var{expression}. This
6232 changes @var{symbol}'s value and type to conform to
6233 @var{expression}. If @var{symbol} was flagged as external, it remains
6234 flagged (@pxref{Symbol Attributes}).
6236 You may @code{.set} a symbol many times in the same assembly.
6238 If you @code{.set} a global symbol, the value stored in the object
6239 file is the last value stored into it.
6242 On Z80 @code{set} is a real instruction, use
6243 @samp{@var{symbol} defl @var{expression}} instead.
6247 @section @code{.short @var{expressions}}
6249 @cindex @code{short} directive
6251 @code{.short} is normally the same as @samp{.word}.
6252 @xref{Word,,@code{.word}}.
6254 In some configurations, however, @code{.short} and @code{.word} generate
6255 numbers of different lengths. @xref{Machine Dependencies}.
6259 @code{.short} is the same as @samp{.word}. @xref{Word,,@code{.word}}.
6262 This expects zero or more @var{expressions}, and emits
6263 a 16 bit number for each.
6268 @section @code{.single @var{flonums}}
6270 @cindex @code{single} directive
6271 @cindex floating point numbers (single)
6272 This directive assembles zero or more flonums, separated by commas. It
6273 has the same effect as @code{.float}.
6275 The exact kind of floating point numbers emitted depends on how
6276 @command{@value{AS}} is configured. @xref{Machine Dependencies}.
6280 On the @value{TARGET} family, @code{.single} emits 32-bit floating point
6281 numbers in @sc{ieee} format.
6287 @section @code{.size}
6289 This directive is used to set the size associated with a symbol.
6293 @c only print the extra heading if both COFF and ELF are set
6294 @subheading COFF Version
6297 @cindex @code{size} directive (COFF version)
6298 For COFF targets, the @code{.size} directive is only permitted inside
6299 @code{.def}/@code{.endef} pairs. It is used like this:
6302 .size @var{expression}
6306 @samp{.size} is only meaningful when generating COFF format output; when
6307 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
6314 @c only print the extra heading if both COFF and ELF are set
6315 @subheading ELF Version
6318 @cindex @code{size} directive (ELF version)
6319 For ELF targets, the @code{.size} directive is used like this:
6322 .size @var{name} , @var{expression}
6325 This directive sets the size associated with a symbol @var{name}.
6326 The size in bytes is computed from @var{expression} which can make use of label
6327 arithmetic. This directive is typically used to set the size of function
6332 @ifclear no-space-dir
6334 @section @code{.skip @var{size} , @var{fill}}
6336 @cindex @code{skip} directive
6337 @cindex filling memory
6338 This directive emits @var{size} bytes, each of value @var{fill}. Both
6339 @var{size} and @var{fill} are absolute expressions. If the comma and
6340 @var{fill} are omitted, @var{fill} is assumed to be zero. This is the same as
6345 @section @code{.sleb128 @var{expressions}}
6347 @cindex @code{sleb128} directive
6348 @var{sleb128} stands for ``signed little endian base 128.'' This is a
6349 compact, variable length representation of numbers used by the DWARF
6350 symbolic debugging format. @xref{Uleb128, ,@code{.uleb128}}.
6352 @ifclear no-space-dir
6354 @section @code{.space @var{size} , @var{fill}}
6356 @cindex @code{space} directive
6357 @cindex filling memory
6358 This directive emits @var{size} bytes, each of value @var{fill}. Both
6359 @var{size} and @var{fill} are absolute expressions. If the comma
6360 and @var{fill} are omitted, @var{fill} is assumed to be zero. This is the same
6365 @emph{Warning:} @code{.space} has a completely different meaning for HPPA
6366 targets; use @code{.block} as a substitute. See @cite{HP9000 Series 800
6367 Assembly Language Reference Manual} (HP 92432-90001) for the meaning of the
6368 @code{.space} directive. @xref{HPPA Directives,,HPPA Assembler Directives},
6376 @section @code{.stabd, .stabn, .stabs}
6378 @cindex symbolic debuggers, information for
6379 @cindex @code{stab@var{x}} directives
6380 There are three directives that begin @samp{.stab}.
6381 All emit symbols (@pxref{Symbols}), for use by symbolic debuggers.
6382 The symbols are not entered in the @command{@value{AS}} hash table: they
6383 cannot be referenced elsewhere in the source file.
6384 Up to five fields are required:
6388 This is the symbol's name. It may contain any character except
6389 @samp{\000}, so is more general than ordinary symbol names. Some
6390 debuggers used to code arbitrarily complex structures into symbol names
6394 An absolute expression. The symbol's type is set to the low 8 bits of
6395 this expression. Any bit pattern is permitted, but @code{@value{LD}}
6396 and debuggers choke on silly bit patterns.
6399 An absolute expression. The symbol's ``other'' attribute is set to the
6400 low 8 bits of this expression.
6403 An absolute expression. The symbol's descriptor is set to the low 16
6404 bits of this expression.
6407 An absolute expression which becomes the symbol's value.
6410 If a warning is detected while reading a @code{.stabd}, @code{.stabn},
6411 or @code{.stabs} statement, the symbol has probably already been created;
6412 you get a half-formed symbol in your object file. This is
6413 compatible with earlier assemblers!
6416 @cindex @code{stabd} directive
6417 @item .stabd @var{type} , @var{other} , @var{desc}
6419 The ``name'' of the symbol generated is not even an empty string.
6420 It is a null pointer, for compatibility. Older assemblers used a
6421 null pointer so they didn't waste space in object files with empty
6424 The symbol's value is set to the location counter,
6425 relocatably. When your program is linked, the value of this symbol
6426 is the address of the location counter when the @code{.stabd} was
6429 @cindex @code{stabn} directive
6430 @item .stabn @var{type} , @var{other} , @var{desc} , @var{value}
6431 The name of the symbol is set to the empty string @code{""}.
6433 @cindex @code{stabs} directive
6434 @item .stabs @var{string} , @var{type} , @var{other} , @var{desc} , @var{value}
6435 All five fields are specified.
6441 @section @code{.string} "@var{str}", @code{.string8} "@var{str}", @code{.string16}
6442 "@var{str}", @code{.string32} "@var{str}", @code{.string64} "@var{str}"
6444 @cindex string, copying to object file
6445 @cindex string8, copying to object file
6446 @cindex string16, copying to object file
6447 @cindex string32, copying to object file
6448 @cindex string64, copying to object file
6449 @cindex @code{string} directive
6450 @cindex @code{string8} directive
6451 @cindex @code{string16} directive
6452 @cindex @code{string32} directive
6453 @cindex @code{string64} directive
6455 Copy the characters in @var{str} to the object file. You may specify more than
6456 one string to copy, separated by commas. Unless otherwise specified for a
6457 particular machine, the assembler marks the end of each string with a 0 byte.
6458 You can use any of the escape sequences described in @ref{Strings,,Strings}.
6460 The variants @code{string16}, @code{string32} and @code{string64} differ from
6461 the @code{string} pseudo opcode in that each 8-bit character from @var{str} is
6462 copied and expanded to 16, 32 or 64 bits respectively. The expanded characters
6463 are stored in target endianness byte order.
6469 .string "B\0\0\0Y\0\0\0E\0\0\0" /* On little endian targets. */
6470 .string "\0\0\0B\0\0\0Y\0\0\0E" /* On big endian targets. */
6475 @section @code{.struct @var{expression}}
6477 @cindex @code{struct} directive
6478 Switch to the absolute section, and set the section offset to @var{expression},
6479 which must be an absolute expression. You might use this as follows:
6488 This would define the symbol @code{field1} to have the value 0, the symbol
6489 @code{field2} to have the value 4, and the symbol @code{field3} to have the
6490 value 8. Assembly would be left in the absolute section, and you would need to
6491 use a @code{.section} directive of some sort to change to some other section
6492 before further assembly.
6496 @section @code{.subsection @var{name}}
6498 @cindex @code{subsection} directive
6499 @cindex Section Stack
6500 This is one of the ELF section stack manipulation directives. The others are
6501 @code{.section} (@pxref{Section}), @code{.pushsection} (@pxref{PushSection}),
6502 @code{.popsection} (@pxref{PopSection}), and @code{.previous}
6505 This directive replaces the current subsection with @code{name}. The current
6506 section is not changed. The replaced subsection is put onto the section stack
6507 in place of the then current top of stack subsection.
6512 @section @code{.symver}
6513 @cindex @code{symver} directive
6514 @cindex symbol versioning
6515 @cindex versions of symbols
6516 Use the @code{.symver} directive to bind symbols to specific version nodes
6517 within a source file. This is only supported on ELF platforms, and is
6518 typically used when assembling files to be linked into a shared library.
6519 There are cases where it may make sense to use this in objects to be bound
6520 into an application itself so as to override a versioned symbol from a
6523 For ELF targets, the @code{.symver} directive can be used like this:
6525 .symver @var{name}, @var{name2@@nodename}
6527 If the symbol @var{name} is defined within the file
6528 being assembled, the @code{.symver} directive effectively creates a symbol
6529 alias with the name @var{name2@@nodename}, and in fact the main reason that we
6530 just don't try and create a regular alias is that the @var{@@} character isn't
6531 permitted in symbol names. The @var{name2} part of the name is the actual name
6532 of the symbol by which it will be externally referenced. The name @var{name}
6533 itself is merely a name of convenience that is used so that it is possible to
6534 have definitions for multiple versions of a function within a single source
6535 file, and so that the compiler can unambiguously know which version of a
6536 function is being mentioned. The @var{nodename} portion of the alias should be
6537 the name of a node specified in the version script supplied to the linker when
6538 building a shared library. If you are attempting to override a versioned
6539 symbol from a shared library, then @var{nodename} should correspond to the
6540 nodename of the symbol you are trying to override.
6542 If the symbol @var{name} is not defined within the file being assembled, all
6543 references to @var{name} will be changed to @var{name2@@nodename}. If no
6544 reference to @var{name} is made, @var{name2@@nodename} will be removed from the
6547 Another usage of the @code{.symver} directive is:
6549 .symver @var{name}, @var{name2@@@@nodename}
6551 In this case, the symbol @var{name} must exist and be defined within
6552 the file being assembled. It is similar to @var{name2@@nodename}. The
6553 difference is @var{name2@@@@nodename} will also be used to resolve
6554 references to @var{name2} by the linker.
6556 The third usage of the @code{.symver} directive is:
6558 .symver @var{name}, @var{name2@@@@@@nodename}
6560 When @var{name} is not defined within the
6561 file being assembled, it is treated as @var{name2@@nodename}. When
6562 @var{name} is defined within the file being assembled, the symbol
6563 name, @var{name}, will be changed to @var{name2@@@@nodename}.
6568 @section @code{.tag @var{structname}}
6570 @cindex COFF structure debugging
6571 @cindex structure debugging, COFF
6572 @cindex @code{tag} directive
6573 This directive is generated by compilers to include auxiliary debugging
6574 information in the symbol table. It is only permitted inside
6575 @code{.def}/@code{.endef} pairs. Tags are used to link structure
6576 definitions in the symbol table with instances of those structures.
6579 @samp{.tag} is only used when generating COFF format output; when
6580 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
6586 @section @code{.text @var{subsection}}
6588 @cindex @code{text} directive
6589 Tells @command{@value{AS}} to assemble the following statements onto the end of
6590 the text subsection numbered @var{subsection}, which is an absolute
6591 expression. If @var{subsection} is omitted, subsection number zero
6595 @section @code{.title "@var{heading}"}
6597 @cindex @code{title} directive
6598 @cindex listing control: title line
6599 Use @var{heading} as the title (second line, immediately after the
6600 source file name and pagenumber) when generating assembly listings.
6602 This directive affects subsequent pages, as well as the current page if
6603 it appears within ten lines of the top of a page.
6607 @section @code{.type}
6609 This directive is used to set the type of a symbol.
6613 @c only print the extra heading if both COFF and ELF are set
6614 @subheading COFF Version
6617 @cindex COFF symbol type
6618 @cindex symbol type, COFF
6619 @cindex @code{type} directive (COFF version)
6620 For COFF targets, this directive is permitted only within
6621 @code{.def}/@code{.endef} pairs. It is used like this:
6627 This records the integer @var{int} as the type attribute of a symbol table
6631 @samp{.type} is associated only with COFF format output; when
6632 @command{@value{AS}} is configured for @code{b.out} output, it accepts this
6633 directive but ignores it.
6639 @c only print the extra heading if both COFF and ELF are set
6640 @subheading ELF Version
6643 @cindex ELF symbol type
6644 @cindex symbol type, ELF
6645 @cindex @code{type} directive (ELF version)
6646 For ELF targets, the @code{.type} directive is used like this:
6649 .type @var{name} , @var{type description}
6652 This sets the type of symbol @var{name} to be either a
6653 function symbol or an object symbol. There are five different syntaxes
6654 supported for the @var{type description} field, in order to provide
6655 compatibility with various other assemblers.
6657 Because some of the characters used in these syntaxes (such as @samp{@@} and
6658 @samp{#}) are comment characters for some architectures, some of the syntaxes
6659 below do not work on all architectures. The first variant will be accepted by
6660 the GNU assembler on all architectures so that variant should be used for
6661 maximum portability, if you do not need to assemble your code with other
6664 The syntaxes supported are:
6667 .type <name> STT_<TYPE_IN_UPPER_CASE>
6668 .type <name>,#<type>
6669 .type <name>,@@<type>
6670 .type <name>,%<type>
6671 .type <name>,"<type>"
6674 The types supported are:
6679 Mark the symbol as being a function name.
6682 @itemx gnu_indirect_function
6683 Mark the symbol as an indirect function when evaluated during reloc
6684 processing. (This is only supported on assemblers targeting GNU systems).
6688 Mark the symbol as being a data object.
6692 Mark the symbol as being a thead-local data object.
6696 Mark the symbol as being a common data object.
6700 Does not mark the symbol in any way. It is supported just for completeness.
6702 @item gnu_unique_object
6703 Marks the symbol as being a globally unique data object. The dynamic linker
6704 will make sure that in the entire process there is just one symbol with this
6705 name and type in use. (This is only supported on assemblers targeting GNU
6710 Note: Some targets support extra types in addition to those listed above.
6716 @section @code{.uleb128 @var{expressions}}
6718 @cindex @code{uleb128} directive
6719 @var{uleb128} stands for ``unsigned little endian base 128.'' This is a
6720 compact, variable length representation of numbers used by the DWARF
6721 symbolic debugging format. @xref{Sleb128, ,@code{.sleb128}}.
6725 @section @code{.val @var{addr}}
6727 @cindex @code{val} directive
6728 @cindex COFF value attribute
6729 @cindex value attribute, COFF
6730 This directive, permitted only within @code{.def}/@code{.endef} pairs,
6731 records the address @var{addr} as the value attribute of a symbol table
6735 @samp{.val} is used only for COFF output; when @command{@value{AS}} is
6736 configured for @code{b.out}, it accepts this directive but ignores it.
6742 @section @code{.version "@var{string}"}
6744 @cindex @code{version} directive
6745 This directive creates a @code{.note} section and places into it an ELF
6746 formatted note of type NT_VERSION. The note's name is set to @code{string}.
6751 @section @code{.vtable_entry @var{table}, @var{offset}}
6753 @cindex @code{vtable_entry} directive
6754 This directive finds or creates a symbol @code{table} and creates a
6755 @code{VTABLE_ENTRY} relocation for it with an addend of @code{offset}.
6758 @section @code{.vtable_inherit @var{child}, @var{parent}}
6760 @cindex @code{vtable_inherit} directive
6761 This directive finds the symbol @code{child} and finds or creates the symbol
6762 @code{parent} and then creates a @code{VTABLE_INHERIT} relocation for the
6763 parent whose addend is the value of the child symbol. As a special case the
6764 parent name of @code{0} is treated as referring to the @code{*ABS*} section.
6768 @section @code{.warning "@var{string}"}
6769 @cindex warning directive
6770 Similar to the directive @code{.error}
6771 (@pxref{Error,,@code{.error "@var{string}"}}), but just emits a warning.
6774 @section @code{.weak @var{names}}
6776 @cindex @code{weak} directive
6777 This directive sets the weak attribute on the comma separated list of symbol
6778 @code{names}. If the symbols do not already exist, they will be created.
6780 On COFF targets other than PE, weak symbols are a GNU extension. This
6781 directive sets the weak attribute on the comma separated list of symbol
6782 @code{names}. If the symbols do not already exist, they will be created.
6784 On the PE target, weak symbols are supported natively as weak aliases.
6785 When a weak symbol is created that is not an alias, GAS creates an
6786 alternate symbol to hold the default value.
6789 @section @code{.weakref @var{alias}, @var{target}}
6791 @cindex @code{weakref} directive
6792 This directive creates an alias to the target symbol that enables the symbol to
6793 be referenced with weak-symbol semantics, but without actually making it weak.
6794 If direct references or definitions of the symbol are present, then the symbol
6795 will not be weak, but if all references to it are through weak references, the
6796 symbol will be marked as weak in the symbol table.
6798 The effect is equivalent to moving all references to the alias to a separate
6799 assembly source file, renaming the alias to the symbol in it, declaring the
6800 symbol as weak there, and running a reloadable link to merge the object files
6801 resulting from the assembly of the new source file and the old source file that
6802 had the references to the alias removed.
6804 The alias itself never makes to the symbol table, and is entirely handled
6805 within the assembler.
6808 @section @code{.word @var{expressions}}
6810 @cindex @code{word} directive
6811 This directive expects zero or more @var{expressions}, of any section,
6812 separated by commas.
6815 For each expression, @command{@value{AS}} emits a 32-bit number.
6818 For each expression, @command{@value{AS}} emits a 16-bit number.
6823 The size of the number emitted, and its byte order,
6824 depend on what target computer the assembly is for.
6827 @c on amd29k, i960, sparc the "special treatment to support compilers" doesn't
6828 @c happen---32-bit addressability, period; no long/short jumps.
6829 @ifset DIFF-TBL-KLUGE
6830 @cindex difference tables altered
6831 @cindex altered difference tables
6833 @emph{Warning: Special Treatment to support Compilers}
6837 Machines with a 32-bit address space, but that do less than 32-bit
6838 addressing, require the following special treatment. If the machine of
6839 interest to you does 32-bit addressing (or doesn't require it;
6840 @pxref{Machine Dependencies}), you can ignore this issue.
6843 In order to assemble compiler output into something that works,
6844 @command{@value{AS}} occasionally does strange things to @samp{.word} directives.
6845 Directives of the form @samp{.word sym1-sym2} are often emitted by
6846 compilers as part of jump tables. Therefore, when @command{@value{AS}} assembles a
6847 directive of the form @samp{.word sym1-sym2}, and the difference between
6848 @code{sym1} and @code{sym2} does not fit in 16 bits, @command{@value{AS}}
6849 creates a @dfn{secondary jump table}, immediately before the next label.
6850 This secondary jump table is preceded by a short-jump to the
6851 first byte after the secondary table. This short-jump prevents the flow
6852 of control from accidentally falling into the new table. Inside the
6853 table is a long-jump to @code{sym2}. The original @samp{.word}
6854 contains @code{sym1} minus the address of the long-jump to
6857 If there were several occurrences of @samp{.word sym1-sym2} before the
6858 secondary jump table, all of them are adjusted. If there was a
6859 @samp{.word sym3-sym4}, that also did not fit in sixteen bits, a
6860 long-jump to @code{sym4} is included in the secondary jump table,
6861 and the @code{.word} directives are adjusted to contain @code{sym3}
6862 minus the address of the long-jump to @code{sym4}; and so on, for as many
6863 entries in the original jump table as necessary.
6866 @emph{This feature may be disabled by compiling @command{@value{AS}} with the
6867 @samp{-DWORKING_DOT_WORD} option.} This feature is likely to confuse
6868 assembly language programmers.
6871 @c end DIFF-TBL-KLUGE
6874 @section Deprecated Directives
6876 @cindex deprecated directives
6877 @cindex obsolescent directives
6878 One day these directives won't work.
6879 They are included for compatibility with older assemblers.
6886 @node Object Attributes
6887 @chapter Object Attributes
6888 @cindex object attributes
6890 @command{@value{AS}} assembles source files written for a specific architecture
6891 into object files for that architecture. But not all object files are alike.
6892 Many architectures support incompatible variations. For instance, floating
6893 point arguments might be passed in floating point registers if the object file
6894 requires hardware floating point support---or floating point arguments might be
6895 passed in integer registers if the object file supports processors with no
6896 hardware floating point unit. Or, if two objects are built for different
6897 generations of the same architecture, the combination may require the
6898 newer generation at run-time.
6900 This information is useful during and after linking. At link time,
6901 @command{@value{LD}} can warn about incompatible object files. After link
6902 time, tools like @command{gdb} can use it to process the linked file
6905 Compatibility information is recorded as a series of object attributes. Each
6906 attribute has a @dfn{vendor}, @dfn{tag}, and @dfn{value}. The vendor is a
6907 string, and indicates who sets the meaning of the tag. The tag is an integer,
6908 and indicates what property the attribute describes. The value may be a string
6909 or an integer, and indicates how the property affects this object. Missing
6910 attributes are the same as attributes with a zero value or empty string value.
6912 Object attributes were developed as part of the ABI for the ARM Architecture.
6913 The file format is documented in @cite{ELF for the ARM Architecture}.
6916 * GNU Object Attributes:: @sc{gnu} Object Attributes
6917 * Defining New Object Attributes:: Defining New Object Attributes
6920 @node GNU Object Attributes
6921 @section @sc{gnu} Object Attributes
6923 The @code{.gnu_attribute} directive records an object attribute
6924 with vendor @samp{gnu}.
6926 Except for @samp{Tag_compatibility}, which has both an integer and a string for
6927 its value, @sc{gnu} attributes have a string value if the tag number is odd and
6928 an integer value if the tag number is even. The second bit (@code{@var{tag} &
6929 2} is set for architecture-independent attributes and clear for
6930 architecture-dependent ones.
6932 @subsection Common @sc{gnu} attributes
6934 These attributes are valid on all architectures.
6937 @item Tag_compatibility (32)
6938 The compatibility attribute takes an integer flag value and a vendor name. If
6939 the flag value is 0, the file is compatible with other toolchains. If it is 1,
6940 then the file is only compatible with the named toolchain. If it is greater
6941 than 1, the file can only be processed by other toolchains under some private
6942 arrangement indicated by the flag value and the vendor name.
6945 @subsection MIPS Attributes
6948 @item Tag_GNU_MIPS_ABI_FP (4)
6949 The floating-point ABI used by this object file. The value will be:
6953 0 for files not affected by the floating-point ABI.
6955 1 for files using the hardware floating-point with a standard double-precision
6958 2 for files using the hardware floating-point ABI with a single-precision FPU.
6960 3 for files using the software floating-point ABI.
6962 4 for files using the hardware floating-point ABI with 64-bit wide
6963 double-precision floating-point registers and 32-bit wide general
6968 @subsection PowerPC Attributes
6971 @item Tag_GNU_Power_ABI_FP (4)
6972 The floating-point ABI used by this object file. The value will be:
6976 0 for files not affected by the floating-point ABI.
6978 1 for files using double-precision hardware floating-point ABI.
6980 2 for files using the software floating-point ABI.
6982 3 for files using single-precision hardware floating-point ABI.
6985 @item Tag_GNU_Power_ABI_Vector (8)
6986 The vector ABI used by this object file. The value will be:
6990 0 for files not affected by the vector ABI.
6992 1 for files using general purpose registers to pass vectors.
6994 2 for files using AltiVec registers to pass vectors.
6996 3 for files using SPE registers to pass vectors.
7000 @node Defining New Object Attributes
7001 @section Defining New Object Attributes
7003 If you want to define a new @sc{gnu} object attribute, here are the places you
7004 will need to modify. New attributes should be discussed on the @samp{binutils}
7009 This manual, which is the official register of attributes.
7011 The header for your architecture @file{include/elf}, to define the tag.
7013 The @file{bfd} support file for your architecture, to merge the attribute
7014 and issue any appropriate link warnings.
7016 Test cases in @file{ld/testsuite} for merging and link warnings.
7018 @file{binutils/readelf.c} to display your attribute.
7020 GCC, if you want the compiler to mark the attribute automatically.
7026 @node Machine Dependencies
7027 @chapter Machine Dependent Features
7029 @cindex machine dependencies
7030 The machine instruction sets are (almost by definition) different on
7031 each machine where @command{@value{AS}} runs. Floating point representations
7032 vary as well, and @command{@value{AS}} often supports a few additional
7033 directives or command-line options for compatibility with other
7034 assemblers on a particular platform. Finally, some versions of
7035 @command{@value{AS}} support special pseudo-instructions for branch
7038 This chapter discusses most of these differences, though it does not
7039 include details on any machine's instruction set. For details on that
7040 subject, see the hardware manufacturer's manual.
7044 * AArch64-Dependent:: AArch64 Dependent Features
7047 * Alpha-Dependent:: Alpha Dependent Features
7050 * ARC-Dependent:: ARC Dependent Features
7053 * ARM-Dependent:: ARM Dependent Features
7056 * AVR-Dependent:: AVR Dependent Features
7059 * Blackfin-Dependent:: Blackfin Dependent Features
7062 * CR16-Dependent:: CR16 Dependent Features
7065 * CRIS-Dependent:: CRIS Dependent Features
7068 * D10V-Dependent:: D10V Dependent Features
7071 * D30V-Dependent:: D30V Dependent Features
7074 * Epiphany-Dependent:: EPIPHANY Dependent Features
7077 * H8/300-Dependent:: Renesas H8/300 Dependent Features
7080 * HPPA-Dependent:: HPPA Dependent Features
7083 * ESA/390-Dependent:: IBM ESA/390 Dependent Features
7086 * i386-Dependent:: Intel 80386 and AMD x86-64 Dependent Features
7089 * i860-Dependent:: Intel 80860 Dependent Features
7092 * i960-Dependent:: Intel 80960 Dependent Features
7095 * IA-64-Dependent:: Intel IA-64 Dependent Features
7098 * IP2K-Dependent:: IP2K Dependent Features
7101 * LM32-Dependent:: LM32 Dependent Features
7104 * M32C-Dependent:: M32C Dependent Features
7107 * M32R-Dependent:: M32R Dependent Features
7110 * M68K-Dependent:: M680x0 Dependent Features
7113 * M68HC11-Dependent:: M68HC11 and 68HC12 Dependent Features
7116 * Meta-Dependent :: Meta Dependent Features
7119 * MicroBlaze-Dependent:: MICROBLAZE Dependent Features
7122 * MIPS-Dependent:: MIPS Dependent Features
7125 * MMIX-Dependent:: MMIX Dependent Features
7128 * MSP430-Dependent:: MSP430 Dependent Features
7131 * NiosII-Dependent:: Altera Nios II Dependent Features
7134 * NS32K-Dependent:: NS32K Dependent Features
7137 * SH-Dependent:: Renesas / SuperH SH Dependent Features
7138 * SH64-Dependent:: SuperH SH64 Dependent Features
7141 * PDP-11-Dependent:: PDP-11 Dependent Features
7144 * PJ-Dependent:: picoJava Dependent Features
7147 * PPC-Dependent:: PowerPC Dependent Features
7150 * RL78-Dependent:: RL78 Dependent Features
7153 * RX-Dependent:: RX Dependent Features
7156 * S/390-Dependent:: IBM S/390 Dependent Features
7159 * SCORE-Dependent:: SCORE Dependent Features
7162 * Sparc-Dependent:: SPARC Dependent Features
7165 * TIC54X-Dependent:: TI TMS320C54x Dependent Features
7168 * TIC6X-Dependent :: TI TMS320C6x Dependent Features
7171 * TILE-Gx-Dependent :: Tilera TILE-Gx Dependent Features
7174 * TILEPro-Dependent :: Tilera TILEPro Dependent Features
7177 * V850-Dependent:: V850 Dependent Features
7180 * XGATE-Dependent:: XGATE Features
7183 * XSTORMY16-Dependent:: XStormy16 Dependent Features
7186 * Xtensa-Dependent:: Xtensa Dependent Features
7189 * Z80-Dependent:: Z80 Dependent Features
7192 * Z8000-Dependent:: Z8000 Dependent Features
7195 * Vax-Dependent:: VAX Dependent Features
7202 @c The following major nodes are *sections* in the GENERIC version, *chapters*
7203 @c in single-cpu versions. This is mainly achieved by @lowersections. There is a
7204 @c peculiarity: to preserve cross-references, there must be a node called
7205 @c "Machine Dependencies". Hence the conditional nodenames in each
7206 @c major node below. Node defaulting in makeinfo requires adjacency of
7207 @c node and sectioning commands; hence the repetition of @chapter BLAH
7208 @c in both conditional blocks.
7211 @include c-aarch64.texi
7215 @include c-alpha.texi
7231 @include c-bfin.texi
7235 @include c-cr16.texi
7239 @include c-cris.texi
7244 @node Machine Dependencies
7245 @chapter Machine Dependent Features
7247 The machine instruction sets are different on each Renesas chip family,
7248 and there are also some syntax differences among the families. This
7249 chapter describes the specific @command{@value{AS}} features for each
7253 * H8/300-Dependent:: Renesas H8/300 Dependent Features
7254 * SH-Dependent:: Renesas SH Dependent Features
7261 @include c-d10v.texi
7265 @include c-d30v.texi
7269 @include c-epiphany.texi
7273 @include c-h8300.texi
7277 @include c-hppa.texi
7281 @include c-i370.texi
7285 @include c-i386.texi
7289 @include c-i860.texi
7293 @include c-i960.texi
7297 @include c-ia64.texi
7301 @include c-ip2k.texi
7305 @include c-lm32.texi
7309 @include c-m32c.texi
7313 @include c-m32r.texi
7317 @include c-m68k.texi
7321 @include c-m68hc11.texi
7325 @include c-metag.texi
7329 @include c-microblaze.texi
7333 @include c-mips.texi
7337 @include c-mmix.texi
7341 @include c-msp430.texi
7345 @include c-nios2.texi
7349 @include c-ns32k.texi
7353 @include c-pdp11.texi
7365 @include c-rl78.texi
7373 @include c-s390.texi
7377 @include c-score.texi
7382 @include c-sh64.texi
7386 @include c-sparc.texi
7390 @include c-tic54x.texi
7394 @include c-tic6x.texi
7398 @include c-tilegx.texi
7402 @include c-tilepro.texi
7418 @include c-v850.texi
7422 @include c-xgate.texi
7426 @include c-xstormy16.texi
7430 @include c-xtensa.texi
7434 @c reverse effect of @down at top of generic Machine-Dep chapter
7438 @node Reporting Bugs
7439 @chapter Reporting Bugs
7440 @cindex bugs in assembler
7441 @cindex reporting bugs in assembler
7443 Your bug reports play an essential role in making @command{@value{AS}} reliable.
7445 Reporting a bug may help you by bringing a solution to your problem, or it may
7446 not. But in any case the principal function of a bug report is to help the
7447 entire community by making the next version of @command{@value{AS}} work better.
7448 Bug reports are your contribution to the maintenance of @command{@value{AS}}.
7450 In order for a bug report to serve its purpose, you must include the
7451 information that enables us to fix the bug.
7454 * Bug Criteria:: Have you found a bug?
7455 * Bug Reporting:: How to report bugs
7459 @section Have You Found a Bug?
7460 @cindex bug criteria
7462 If you are not sure whether you have found a bug, here are some guidelines:
7465 @cindex fatal signal
7466 @cindex assembler crash
7467 @cindex crash of assembler
7469 If the assembler gets a fatal signal, for any input whatever, that is a
7470 @command{@value{AS}} bug. Reliable assemblers never crash.
7472 @cindex error on valid input
7474 If @command{@value{AS}} produces an error message for valid input, that is a bug.
7476 @cindex invalid input
7478 If @command{@value{AS}} does not produce an error message for invalid input, that
7479 is a bug. However, you should note that your idea of ``invalid input'' might
7480 be our idea of ``an extension'' or ``support for traditional practice''.
7483 If you are an experienced user of assemblers, your suggestions for improvement
7484 of @command{@value{AS}} are welcome in any case.
7488 @section How to Report Bugs
7490 @cindex assembler bugs, reporting
7492 A number of companies and individuals offer support for @sc{gnu} products. If
7493 you obtained @command{@value{AS}} from a support organization, we recommend you
7494 contact that organization first.
7496 You can find contact information for many support companies and
7497 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
7501 In any event, we also recommend that you send bug reports for @command{@value{AS}}
7505 The fundamental principle of reporting bugs usefully is this:
7506 @strong{report all the facts}. If you are not sure whether to state a
7507 fact or leave it out, state it!
7509 Often people omit facts because they think they know what causes the problem
7510 and assume that some details do not matter. Thus, you might assume that the
7511 name of a symbol you use in an example does not matter. Well, probably it does
7512 not, but one cannot be sure. Perhaps the bug is a stray memory reference which
7513 happens to fetch from the location where that name is stored in memory;
7514 perhaps, if the name were different, the contents of that location would fool
7515 the assembler into doing the right thing despite the bug. Play it safe and
7516 give a specific, complete example. That is the easiest thing for you to do,
7517 and the most helpful.
7519 Keep in mind that the purpose of a bug report is to enable us to fix the bug if
7520 it is new to us. Therefore, always write your bug reports on the assumption
7521 that the bug has not been reported previously.
7523 Sometimes people give a few sketchy facts and ask, ``Does this ring a
7524 bell?'' This cannot help us fix a bug, so it is basically useless. We
7525 respond by asking for enough details to enable us to investigate.
7526 You might as well expedite matters by sending them to begin with.
7528 To enable us to fix the bug, you should include all these things:
7532 The version of @command{@value{AS}}. @command{@value{AS}} announces it if you start
7533 it with the @samp{--version} argument.
7535 Without this, we will not know whether there is any point in looking for
7536 the bug in the current version of @command{@value{AS}}.
7539 Any patches you may have applied to the @command{@value{AS}} source.
7542 The type of machine you are using, and the operating system name and
7546 What compiler (and its version) was used to compile @command{@value{AS}}---e.g.
7550 The command arguments you gave the assembler to assemble your example and
7551 observe the bug. To guarantee you will not omit something important, list them
7552 all. A copy of the Makefile (or the output from make) is sufficient.
7554 If we were to try to guess the arguments, we would probably guess wrong
7555 and then we might not encounter the bug.
7558 A complete input file that will reproduce the bug. If the bug is observed when
7559 the assembler is invoked via a compiler, send the assembler source, not the
7560 high level language source. Most compilers will produce the assembler source
7561 when run with the @samp{-S} option. If you are using @code{@value{GCC}}, use
7562 the options @samp{-v --save-temps}; this will save the assembler source in a
7563 file with an extension of @file{.s}, and also show you exactly how
7564 @command{@value{AS}} is being run.
7567 A description of what behavior you observe that you believe is
7568 incorrect. For example, ``It gets a fatal signal.''
7570 Of course, if the bug is that @command{@value{AS}} gets a fatal signal, then we
7571 will certainly notice it. But if the bug is incorrect output, we might not
7572 notice unless it is glaringly wrong. You might as well not give us a chance to
7575 Even if the problem you experience is a fatal signal, you should still say so
7576 explicitly. Suppose something strange is going on, such as, your copy of
7577 @command{@value{AS}} is out of sync, or you have encountered a bug in the C
7578 library on your system. (This has happened!) Your copy might crash and ours
7579 would not. If you told us to expect a crash, then when ours fails to crash, we
7580 would know that the bug was not happening for us. If you had not told us to
7581 expect a crash, then we would not be able to draw any conclusion from our
7585 If you wish to suggest changes to the @command{@value{AS}} source, send us context
7586 diffs, as generated by @code{diff} with the @samp{-u}, @samp{-c}, or @samp{-p}
7587 option. Always send diffs from the old file to the new file. If you even
7588 discuss something in the @command{@value{AS}} source, refer to it by context, not
7591 The line numbers in our development sources will not match those in your
7592 sources. Your line numbers would convey no useful information to us.
7595 Here are some things that are not necessary:
7599 A description of the envelope of the bug.
7601 Often people who encounter a bug spend a lot of time investigating
7602 which changes to the input file will make the bug go away and which
7603 changes will not affect it.
7605 This is often time consuming and not very useful, because the way we
7606 will find the bug is by running a single example under the debugger
7607 with breakpoints, not by pure deduction from a series of examples.
7608 We recommend that you save your time for something else.
7610 Of course, if you can find a simpler example to report @emph{instead}
7611 of the original one, that is a convenience for us. Errors in the
7612 output will be easier to spot, running under the debugger will take
7613 less time, and so on.
7615 However, simplification is not vital; if you do not want to do this,
7616 report the bug anyway and send us the entire test case you used.
7619 A patch for the bug.
7621 A patch for the bug does help us if it is a good one. But do not omit
7622 the necessary information, such as the test case, on the assumption that
7623 a patch is all we need. We might see problems with your patch and decide
7624 to fix the problem another way, or we might not understand it at all.
7626 Sometimes with a program as complicated as @command{@value{AS}} it is very hard to
7627 construct an example that will make the program follow a certain path through
7628 the code. If you do not send us the example, we will not be able to construct
7629 one, so we will not be able to verify that the bug is fixed.
7631 And if we cannot understand what bug you are trying to fix, or why your
7632 patch should be an improvement, we will not install it. A test case will
7633 help us to understand.
7636 A guess about what the bug is or what it depends on.
7638 Such guesses are usually wrong. Even we cannot guess right about such
7639 things without first using the debugger to find the facts.
7642 @node Acknowledgements
7643 @chapter Acknowledgements
7645 If you have contributed to GAS and your name isn't listed here,
7646 it is not meant as a slight. We just don't know about it. Send mail to the
7647 maintainer, and we'll correct the situation. Currently
7649 the maintainer is Nick Clifton (email address @code{nickc@@redhat.com}).
7651 Dean Elsner wrote the original @sc{gnu} assembler for the VAX.@footnote{Any
7654 Jay Fenlason maintained GAS for a while, adding support for GDB-specific debug
7655 information and the 68k series machines, most of the preprocessing pass, and
7656 extensive changes in @file{messages.c}, @file{input-file.c}, @file{write.c}.
7658 K. Richard Pixley maintained GAS for a while, adding various enhancements and
7659 many bug fixes, including merging support for several processors, breaking GAS
7660 up to handle multiple object file format back ends (including heavy rewrite,
7661 testing, an integration of the coff and b.out back ends), adding configuration
7662 including heavy testing and verification of cross assemblers and file splits
7663 and renaming, converted GAS to strictly ANSI C including full prototypes, added
7664 support for m680[34]0 and cpu32, did considerable work on i960 including a COFF
7665 port (including considerable amounts of reverse engineering), a SPARC opcode
7666 file rewrite, DECstation, rs6000, and hp300hpux host ports, updated ``know''
7667 assertions and made them work, much other reorganization, cleanup, and lint.
7669 Ken Raeburn wrote the high-level BFD interface code to replace most of the code
7670 in format-specific I/O modules.
7672 The original VMS support was contributed by David L. Kashtan. Eric Youngdale
7673 has done much work with it since.
7675 The Intel 80386 machine description was written by Eliot Dresselhaus.
7677 Minh Tran-Le at IntelliCorp contributed some AIX 386 support.
7679 The Motorola 88k machine description was contributed by Devon Bowen of Buffalo
7680 University and Torbjorn Granlund of the Swedish Institute of Computer Science.
7682 Keith Knowles at the Open Software Foundation wrote the original MIPS back end
7683 (@file{tc-mips.c}, @file{tc-mips.h}), and contributed Rose format support
7684 (which hasn't been merged in yet). Ralph Campbell worked with the MIPS code to
7685 support a.out format.
7687 Support for the Zilog Z8k and Renesas H8/300 processors (tc-z8k,
7688 tc-h8300), and IEEE 695 object file format (obj-ieee), was written by
7689 Steve Chamberlain of Cygnus Support. Steve also modified the COFF back end to
7690 use BFD for some low-level operations, for use with the H8/300 and AMD 29k
7693 John Gilmore built the AMD 29000 support, added @code{.include} support, and
7694 simplified the configuration of which versions accept which directives. He
7695 updated the 68k machine description so that Motorola's opcodes always produced
7696 fixed-size instructions (e.g., @code{jsr}), while synthetic instructions
7697 remained shrinkable (@code{jbsr}). John fixed many bugs, including true tested
7698 cross-compilation support, and one bug in relaxation that took a week and
7699 required the proverbial one-bit fix.
7701 Ian Lance Taylor of Cygnus Support merged the Motorola and MIT syntax for the
7702 68k, completed support for some COFF targets (68k, i386 SVR3, and SCO Unix),
7703 added support for MIPS ECOFF and ELF targets, wrote the initial RS/6000 and
7704 PowerPC assembler, and made a few other minor patches.
7706 Steve Chamberlain made GAS able to generate listings.
7708 Hewlett-Packard contributed support for the HP9000/300.
7710 Jeff Law wrote GAS and BFD support for the native HPPA object format (SOM)
7711 along with a fairly extensive HPPA testsuite (for both SOM and ELF object
7712 formats). This work was supported by both the Center for Software Science at
7713 the University of Utah and Cygnus Support.
7715 Support for ELF format files has been worked on by Mark Eichin of Cygnus
7716 Support (original, incomplete implementation for SPARC), Pete Hoogenboom and
7717 Jeff Law at the University of Utah (HPPA mainly), Michael Meissner of the Open
7718 Software Foundation (i386 mainly), and Ken Raeburn of Cygnus Support (sparc,
7719 and some initial 64-bit support).
7721 Linas Vepstas added GAS support for the ESA/390 ``IBM 370'' architecture.
7723 Richard Henderson rewrote the Alpha assembler. Klaus Kaempf wrote GAS and BFD
7724 support for openVMS/Alpha.
7726 Timothy Wall, Michael Hayes, and Greg Smart contributed to the various tic*
7729 David Heine, Sterling Augustine, Bob Wilson and John Ruttenberg from Tensilica,
7730 Inc.@: added support for Xtensa processors.
7732 Several engineers at Cygnus Support have also provided many small bug fixes and
7733 configuration enhancements.
7735 Jon Beniston added support for the Lattice Mico32 architecture.
7737 Many others have contributed large or small bugfixes and enhancements. If
7738 you have contributed significant work and are not mentioned on this list, and
7739 want to be, let us know. Some of the history has been lost; we are not
7740 intentionally leaving anyone out.
7742 @node GNU Free Documentation License
7743 @appendix GNU Free Documentation License
7747 @unnumbered AS Index
projects / deliverable / binutils-gdb.git / blob