82 lines
4.1 KiB
HTML
82 lines
4.1 KiB
HTML
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<html lang="en">
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<head>
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<title>P2align - Using as</title>
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<meta name="description" content="Using as">
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<meta name="generator" content="makeinfo 4.13">
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<link title="Top" rel="start" href="index.html#Top">
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<link rel="up" href="Pseudo-Ops.html#Pseudo-Ops" title="Pseudo Ops">
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<link rel="prev" href="Org.html#Org" title="Org">
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<link href="http://www.gnu.org/software/texinfo/" rel="generator-home" title="Texinfo Homepage">
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<!--
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This file documents the GNU Assembler "as".
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Copyright (C) 1991-2019 Free Software Foundation, Inc.
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Permission is granted to copy, distribute and/or modify this document
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under the terms of the GNU Free Documentation License, Version 1.3
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or any later version published by the Free Software Foundation;
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with no Invariant Sections, with no Front-Cover Texts, and with no
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Back-Cover Texts. A copy of the license is included in the
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section entitled ``GNU Free Documentation License''.
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</head>
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<body>
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<div class="node">
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<a name="P2align"></a>
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<p>
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Next: <a rel="next" accesskey="n" href="PopSection.html#PopSection">PopSection</a>,
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Previous: <a rel="previous" accesskey="p" href="Org.html#Org">Org</a>,
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Up: <a rel="up" accesskey="u" href="Pseudo-Ops.html#Pseudo-Ops">Pseudo Ops</a>
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<hr>
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</div>
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<h3 class="section">7.69 <code>.p2align[wl] </code><var>abs-expr</var><code>, </code><var>abs-expr</var><code>, </code><var>abs-expr</var></h3>
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<p><a name="index-padding-the-location-counter-given-a-power-of-two-431"></a><a name="index-g_t_0040code_007bp2align_007d-directive-432"></a>Pad the location counter (in the current subsection) to a particular
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storage boundary. The first expression (which must be absolute) is the
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number of low-order zero bits the location counter must have after
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advancement. For example ‘<samp><span class="samp">.p2align 3</span></samp>’ advances the location
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counter until it is a multiple of 8. If the location counter is already a
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multiple of 8, no change is needed.
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<p>The second expression (also absolute) gives the fill value to be stored in the
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padding bytes. It (and the comma) may be omitted. If it is omitted, the
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padding bytes are normally zero. However, on most systems, if the section is
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marked as containing code and the fill value is omitted, the space is filled
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with no-op instructions.
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<p>The third expression is also absolute, and is also optional. If it is present,
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it is the maximum number of bytes that should be skipped by this alignment
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directive. If doing the alignment would require skipping more bytes than the
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specified maximum, then the alignment is not done at all. You can omit the
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fill value (the second argument) entirely by simply using two commas after the
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required alignment; this can be useful if you want the alignment to be filled
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with no-op instructions when appropriate.
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<p><a name="index-g_t_0040code_007bp2alignw_007d-directive-433"></a><a name="index-g_t_0040code_007bp2alignl_007d-directive-434"></a>The <code>.p2alignw</code> and <code>.p2alignl</code> directives are variants of the
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<code>.p2align</code> directive. The <code>.p2alignw</code> directive treats the fill
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pattern as a two byte word value. The <code>.p2alignl</code> directives treats the
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fill pattern as a four byte longword value. For example, <code>.p2alignw
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2,0x368d</code> will align to a multiple of 4. If it skips two bytes, they will be
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filled in with the value 0x368d (the exact placement of the bytes depends upon
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the endianness of the processor). If it skips 1 or 3 bytes, the fill value is
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undefined.
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</body></html>
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