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97 lines
4.1 KiB
HTML
97 lines
4.1 KiB
HTML
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
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<!-- Copyright (C) 1992-2019 Free Software Foundation, Inc.
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Contributed by Cygnus Support. Written by Julia Menapace, Jim Kingdon,
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and David MacKenzie.
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Permission is granted to copy, distribute and/or modify this document
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<head>
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<title>Register Variables (STABS)</title>
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<meta name="description" content="Register Variables (STABS)">
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<link href="Symbol-Types-Index.html#Symbol-Types-Index" rel="index" title="Symbol Types Index">
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<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">
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<link href="Variables.html#Variables" rel="up" title="Variables">
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<link href="Common-Blocks.html#Common-Blocks" rel="next" title="Common Blocks">
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<link href="Global-Variables.html#Global-Variables" rel="prev" title="Global Variables">
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<a name="Register-Variables"></a>
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<div class="header">
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<p>
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Next: <a href="Common-Blocks.html#Common-Blocks" accesskey="n" rel="next">Common Blocks</a>, Previous: <a href="Global-Variables.html#Global-Variables" accesskey="p" rel="prev">Global Variables</a>, Up: <a href="Variables.html#Variables" accesskey="u" rel="up">Variables</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Symbol-Types-Index.html#Symbol-Types-Index" title="Index" rel="index">Index</a>]</p>
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</div>
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<hr>
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<a name="Register-Variables-1"></a>
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<h3 class="section">4.3 Register Variables</h3>
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<a name="index-N_005fRSYM"></a>
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<a name="index-C_005fRSYM"></a>
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<p>Register variables have their own stab type, <code>N_RSYM</code>
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(<code>C_RSYM</code> for XCOFF), and their own symbol descriptor, ‘<samp>r</samp>’.
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The stab’s value is the number of the register where the variable data
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will be stored.
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</p>
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<p>AIX defines a separate symbol descriptor ‘<samp>d</samp>’ for floating point
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registers. This seems unnecessary; why not just just give floating
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point registers different register numbers? I have not verified whether
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the compiler actually uses ‘<samp>d</samp>’.
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</p>
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<p>If the register is explicitly allocated to a global variable, but not
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initialized, as in:
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</p>
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<div class="example">
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<pre class="example">register int g_bar asm ("%g5");
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</pre></div>
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<p>then the stab may be emitted at the end of the object file, with
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the other bss symbols.
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</p>
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</body>
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</html>
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