1<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
2<html>
3<!-- This file documents the GNU Assembler "as".
4
5Copyright (C) 1991-2021 Free Software Foundation, Inc.
6
7Permission is granted to copy, distribute and/or modify this document
8under the terms of the GNU Free Documentation License, Version 1.3
9or any later version published by the Free Software Foundation;
10with no Invariant Sections, with no Front-Cover Texts, and with no
11Back-Cover Texts.  A copy of the license is included in the
12section entitled "GNU Free Documentation License".
13 -->
14<!-- Created by GNU Texinfo 5.1, http://www.gnu.org/software/texinfo/ -->
15<head>
16<title>Using as: Align</title>
17
18<meta name="description" content="Using as: Align">
19<meta name="keywords" content="Using as: Align">
20<meta name="resource-type" content="document">
21<meta name="distribution" content="global">
22<meta name="Generator" content="makeinfo">
23<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
24<link href="index.html#Top" rel="start" title="Top">
25<link href="AS-Index.html#AS-Index" rel="index" title="AS Index">
26<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">
27<link href="Pseudo-Ops.html#Pseudo-Ops" rel="up" title="Pseudo Ops">
28<link href="Altmacro.html#Altmacro" rel="next" title="Altmacro">
29<link href="ABORT-_0028COFF_0029.html#ABORT-_0028COFF_0029" rel="previous" title="ABORT (COFF)">
30<style type="text/css">
31<!--
32a.summary-letter {text-decoration: none}
33blockquote.smallquotation {font-size: smaller}
34div.display {margin-left: 3.2em}
35div.example {margin-left: 3.2em}
36div.indentedblock {margin-left: 3.2em}
37div.lisp {margin-left: 3.2em}
38div.smalldisplay {margin-left: 3.2em}
39div.smallexample {margin-left: 3.2em}
40div.smallindentedblock {margin-left: 3.2em; font-size: smaller}
41div.smalllisp {margin-left: 3.2em}
42kbd {font-style:oblique}
43pre.display {font-family: inherit}
44pre.format {font-family: inherit}
45pre.menu-comment {font-family: serif}
46pre.menu-preformatted {font-family: serif}
47pre.smalldisplay {font-family: inherit; font-size: smaller}
48pre.smallexample {font-size: smaller}
49pre.smallformat {font-family: inherit; font-size: smaller}
50pre.smalllisp {font-size: smaller}
51span.nocodebreak {white-space:nowrap}
52span.nolinebreak {white-space:nowrap}
53span.roman {font-family:serif; font-weight:normal}
54span.sansserif {font-family:sans-serif; font-weight:normal}
55ul.no-bullet {list-style: none}
56-->
57</style>
58
59
60</head>
61
62<body lang="en" bgcolor="#FFFFFF" text="#000000" link="#0000FF" vlink="#800080" alink="#FF0000">
63<a name="Align"></a>
64<div class="header">
65<p>
66Next: <a href="Altmacro.html#Altmacro" accesskey="n" rel="next">Altmacro</a>, Previous: <a href="ABORT-_0028COFF_0029.html#ABORT-_0028COFF_0029" accesskey="p" rel="previous">ABORT (COFF)</a>, Up: <a href="Pseudo-Ops.html#Pseudo-Ops" accesskey="u" rel="up">Pseudo Ops</a> &nbsp; [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="AS-Index.html#AS-Index" title="Index" rel="index">Index</a>]</p>
67</div>
68<hr>
69<a name="g_t_002ealign-_005babs_002dexpr_005b_002c-abs_002dexpr_005b_002c-abs_002dexpr_005d_005d_005d"></a>
70<h3 class="section">7.3 <code>.align [<var>abs-expr</var>[, <var>abs-expr</var>[, <var>abs-expr</var>]]]</code></h3>
71
72<a name="index-padding-the-location-counter"></a>
73<a name="index-align-directive"></a>
74<p>Pad the location counter (in the current subsection) to a particular storage
75boundary.  The first expression (which must be absolute) is the alignment
76required, as described below.  If this expression is omitted then a default
77value of 0 is used, effectively disabling alignment requirements.
78</p>
79<p>The second expression (also absolute) gives the fill value to be stored in the
80padding bytes.  It (and the comma) may be omitted.  If it is omitted, the
81padding bytes are normally zero.  However, on most systems, if the section is
82marked as containing code and the fill value is omitted, the space is filled
83with no-op instructions.
84</p>
85<p>The third expression is also absolute, and is also optional.  If it is present,
86it is the maximum number of bytes that should be skipped by this alignment
87directive.  If doing the alignment would require skipping more bytes than the
88specified maximum, then the alignment is not done at all.  You can omit the
89fill value (the second argument) entirely by simply using two commas after the
90required alignment; this can be useful if you want the alignment to be filled
91with no-op instructions when appropriate.
92</p>
93<p>The way the required alignment is specified varies from system to system.
94For the arc, hppa, i386 using ELF, iq2000, m68k, or1k,
95s390, sparc, tic4x and xtensa, the first expression is the
96alignment request in bytes.  For example &lsquo;<samp>.align 8</samp>&rsquo; advances
97the location counter until it is a multiple of 8.  If the location counter
98is already a multiple of 8, no change is needed.  For the tic54x, the
99first expression is the alignment request in words.
100</p>
101<p>For other systems, including ppc, i386 using a.out format, arm and
102strongarm, it is the
103number of low-order zero bits the location counter must have after
104advancement.  For example &lsquo;<samp>.align 3</samp>&rsquo; advances the location
105counter until it is a multiple of 8.  If the location counter is already a
106multiple of 8, no change is needed.
107</p>
108<p>This inconsistency is due to the different behaviors of the various
109native assemblers for these systems which GAS must emulate.
110GAS also provides <code>.balign</code> and <code>.p2align</code> directives,
111described later, which have a consistent behavior across all
112architectures (but are specific to GAS).
113</p>
114<hr>
115<div class="header">
116<p>
117Next: <a href="Altmacro.html#Altmacro" accesskey="n" rel="next">Altmacro</a>, Previous: <a href="ABORT-_0028COFF_0029.html#ABORT-_0028COFF_0029" accesskey="p" rel="previous">ABORT (COFF)</a>, Up: <a href="Pseudo-Ops.html#Pseudo-Ops" accesskey="u" rel="up">Pseudo Ops</a> &nbsp; [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="AS-Index.html#AS-Index" title="Index" rel="index">Index</a>]</p>
118</div>
119
120
121
122</body>
123</html>
124