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<a name="Caller_002dSaves-Register-Allocation"></a>
<h4 class="subsection">18.9.10 Caller-Saves Register Allocation</h4>

<p>If you enable it, GCC can save registers around function calls.  This
makes it possible to use call-clobbered registers to hold variables that
must live across calls.
</p>
<dl>
<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>
<dd><p>A C expression specifying which mode is required for saving <var>nregs</var>
of a pseudo-register in call-clobbered hard register <var>regno</var>.  If
<var>regno</var> is unsuitable for caller save, <code>VOIDmode</code> should be
returned.  For most machines this macro need not be defined since GCC
will select the smallest suitable mode.
</p></dd></dl>


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