aarch64-linux-gnu-4.9/share/doc/as.html/Align.html - toolchains/linux-x86/gcc - Git at Google

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 Next: <a href="Altmacro.html#Altmacro" accesskey="n" rel="next">Altmacro</a>, Previous: <a href="ABORT-_0028COFF_0029.html#ABORT-_0028COFF_0029" accesskey="p" rel="prev">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>
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 <a name="g_t_002ealign-abs_002dexpr_002c-abs_002dexpr_002c-abs_002dexpr"></a>
 <h3 class="section">7.3 <code>.align <var>abs-expr</var>, <var>abs-expr</var>, <var>abs-expr</var></code></h3>

 <a name="index-padding-the-location-counter"></a>
 <a name="index-align-directive"></a>
 <p>Pad the location counter (in the current subsection) to a particular storage
 boundary.  The first expression (which must be absolute) is the alignment
 required, as described below.
 </p>
 <p>The second expression (also absolute) gives the fill value to be stored in the
 padding bytes.  It (and the comma) may be omitted.  If it is omitted, the
 padding bytes are normally zero.  However, on some systems, if the section is
 marked as containing code and the fill value is omitted, the space is filled
 with no-op instructions.
 </p>
 <p>The third expression is also absolute, and is also optional.  If it is present,
 it is the maximum number of bytes that should be skipped by this alignment
 directive.  If doing the alignment would require skipping more bytes than the
 specified maximum, then the alignment is not done at all.  You can omit the
 fill value (the second argument) entirely by simply using two commas after the
 required alignment; this can be useful if you want the alignment to be filled
 with no-op instructions when appropriate.
 </p>
 <p>The way the required alignment is specified varies from system to system.
 For the arc, hppa, i386 using ELF, i860, iq2000, m68k, or32,
 s390, sparc, tic4x, tic80 and xtensa, the first expression is the
 alignment request in bytes.  For example &lsquo;<samp>.align 8</samp>&rsquo; advances
 the location counter until it is a multiple of 8.  If the location counter
 is already a multiple of 8, no change is needed.  For the tic54x, the
 first expression is the alignment request in words.
 </p>
 <p>For other systems, including ppc, i386 using a.out format, arm and
 strongarm, it is the
 number of low-order zero bits the location counter must have after
 advancement.  For example &lsquo;<samp>.align 3</samp>&rsquo; advances the location
 counter until it a multiple of 8.  If the location counter is already a
 multiple of 8, no change is needed.
 </p>
 <p>This inconsistency is due to the different behaviors of the various
 native assemblers for these systems which GAS must emulate.
 GAS also provides <code>.balign</code> and <code>.p2align</code> directives,
 described later, which have a consistent behavior across all
 architectures (but are specific to GAS).
 </p>
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	Next: <a href="Altmacro.html#Altmacro" accesskey="n" rel="next">Altmacro</a>, Previous: <a href="ABORT-_0028COFF_0029.html#ABORT-_0028COFF_0029" accesskey="p" rel="prev">ABORT (COFF)</a>, Up: <a href="Pseudo-Ops.html#Pseudo-Ops" accesskey="u" rel="up">Pseudo Ops</a>   [<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>
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	<hr>
	<a name="g_t_002ealign-abs_002dexpr_002c-abs_002dexpr_002c-abs_002dexpr"></a>
	<h3 class="section">7.3 <code>.align <var>abs-expr</var>, <var>abs-expr</var>, <var>abs-expr</var></code></h3>

	<a name="index-padding-the-location-counter"></a>
	<a name="index-align-directive"></a>
	<p>Pad the location counter (in the current subsection) to a particular storage
	boundary. The first expression (which must be absolute) is the alignment
	required, as described below.
	</p>
	<p>The second expression (also absolute) gives the fill value to be stored in the
	padding bytes. It (and the comma) may be omitted. If it is omitted, the
	padding bytes are normally zero. However, on some systems, if the section is
	marked as containing code and the fill value is omitted, the space is filled
	with no-op instructions.
	</p>
	<p>The third expression is also absolute, and is also optional. If it is present,
	it is the maximum number of bytes that should be skipped by this alignment
	directive. If doing the alignment would require skipping more bytes than the
	specified maximum, then the alignment is not done at all. You can omit the
	fill value (the second argument) entirely by simply using two commas after the
	required alignment; this can be useful if you want the alignment to be filled
	with no-op instructions when appropriate.
	</p>
	<p>The way the required alignment is specified varies from system to system.
	For the arc, hppa, i386 using ELF, i860, iq2000, m68k, or32,
	s390, sparc, tic4x, tic80 and xtensa, the first expression is the
	alignment request in bytes. For example ‘<samp>.align 8</samp>’ advances
	the location counter until it is a multiple of 8. If the location counter
	is already a multiple of 8, no change is needed. For the tic54x, the
	first expression is the alignment request in words.
	</p>
	<p>For other systems, including ppc, i386 using a.out format, arm and
	strongarm, it is the
	number of low-order zero bits the location counter must have after
	advancement. For example ‘<samp>.align 3</samp>’ advances the location
	counter until it a multiple of 8. If the location counter is already a
	multiple of 8, no change is needed.
	</p>
	<p>This inconsistency is due to the different behaviors of the various
	native assemblers for these systems which GAS must emulate.
	GAS also provides <code>.balign</code> and <code>.p2align</code> directives,
	described later, which have a consistent behavior across all
	architectures (but are specific to GAS).
	</p>
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