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<a name="Caller-Saves"></a>
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Next: <a rel="next" accesskey="n" href="Function-Entry.html#Function-Entry">Function Entry</a>,
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Previous: <a rel="previous" accesskey="p" href="Aggregate-Return.html#Aggregate-Return">Aggregate Return</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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<div class="defun">
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— Macro: <b>HARD_REGNO_CALLER_SAVE_MODE</b> (<var>regno, nregs</var>)<var><a name="index-HARD_005fREGNO_005fCALLER_005fSAVE_005fMODE-4289"></a></var><br>
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<blockquote><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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