98 lines
4.3 KiB
HTML
98 lines
4.3 KiB
HTML
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<title>GNU Compiler Collection (GCC) Internals: Caller Saves</title>
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<link href="Option-Index.html#Option-Index" rel="index" title="Option Index">
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<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">
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<a name="Caller-Saves"></a>
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<p>
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Next: <a href="Function-Entry.html#Function-Entry" accesskey="n" rel="next">Function Entry</a>, Previous: <a href="Aggregate-Return.html#Aggregate-Return" accesskey="p" rel="prev">Aggregate Return</a>, Up: <a href="Stack-and-Calling.html#Stack-and-Calling" accesskey="u" rel="up">Stack and Calling</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Option-Index.html#Option-Index" title="Index" rel="index">Index</a>]</p>
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<hr>
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<a name="Caller_002dSaves-Register-Allocation"></a>
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<h4 class="subsection">17.9.10 Caller-Saves Register Allocation</h4>
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<p>If you enable it, GCC can save registers around function calls. This
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makes it possible to use call-clobbered registers to hold variables that
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must live across calls.
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</p>
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<dl>
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<dt><a name="index-HARD_005fREGNO_005fCALLER_005fSAVE_005fMODE"></a>Macro: <strong>HARD_REGNO_CALLER_SAVE_MODE</strong> <em>(<var>regno</var>, <var>nregs</var>)</em></dt>
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<dd><p>A C expression specifying which mode is required for saving <var>nregs</var>
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of a pseudo-register in call-clobbered hard register <var>regno</var>. If
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<var>regno</var> is unsuitable for caller save, <code>VOIDmode</code> should be
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returned. For most machines this macro need not be defined since GCC
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will select the smallest suitable mode.
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</p></dd></dl>
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