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<a name="Tail-Calls"></a>
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Next: <a rel="next" accesskey="n" href="Stack-Smashing-Protection.html#Stack-Smashing-Protection">Stack Smashing Protection</a>,
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Previous: <a rel="previous" accesskey="p" href="Profiling.html#Profiling">Profiling</a>,
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Up: <a rel="up" accesskey="u" href="Stack-and-Calling.html#Stack-and-Calling">Stack and Calling</a>
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<h4 class="subsection">17.9.13 Permitting tail calls</h4>
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<p><a name="index-tail-calls-4316"></a>
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<div class="defun">
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— Target Hook: bool <b>TARGET_FUNCTION_OK_FOR_SIBCALL</b> (<var>tree decl, tree exp</var>)<var><a name="index-TARGET_005fFUNCTION_005fOK_005fFOR_005fSIBCALL-4317"></a></var><br>
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<blockquote><p>True if it is OK to do sibling call optimization for the specified
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call expression <var>exp</var>. <var>decl</var> will be the called function,
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or <code>NULL</code> if this is an indirect call.
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<p>It is not uncommon for limitations of calling conventions to prevent
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tail calls to functions outside the current unit of translation, or
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during PIC compilation. The hook is used to enforce these restrictions,
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as the <code>sibcall</code> md pattern can not fail, or fall over to a
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“normal” call. The criteria for successful sibling call optimization
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may vary greatly between different architectures.
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</p></blockquote></div>
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<div class="defun">
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— Target Hook: void <b>TARGET_EXTRA_LIVE_ON_ENTRY</b> (<var>bitmap regs</var>)<var><a name="index-TARGET_005fEXTRA_005fLIVE_005fON_005fENTRY-4318"></a></var><br>
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<blockquote><p>Add any hard registers to <var>regs</var> that are live on entry to the
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function. This hook only needs to be defined to provide registers that
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cannot be found by examination of FUNCTION_ARG_REGNO_P, the callee saved
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registers, STATIC_CHAIN_INCOMING_REGNUM, STATIC_CHAIN_REGNUM,
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TARGET_STRUCT_VALUE_RTX, FRAME_POINTER_REGNUM, EH_USES,
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FRAME_POINTER_REGNUM, ARG_POINTER_REGNUM, and the PIC_OFFSET_TABLE_REGNUM.
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</p></blockquote></div>
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<div class="defun">
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— Target Hook: void <b>TARGET_SET_UP_BY_PROLOGUE</b> (<var>struct hard_reg_set_container *</var>)<var><a name="index-TARGET_005fSET_005fUP_005fBY_005fPROLOGUE-4319"></a></var><br>
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<blockquote><p>This hook should add additional registers that are computed by the prologue to the hard regset for shrink-wrapping optimization purposes.
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</p></blockquote></div>
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<div class="defun">
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— Target Hook: bool <b>TARGET_WARN_FUNC_RETURN</b> (<var>tree</var>)<var><a name="index-TARGET_005fWARN_005fFUNC_005fRETURN-4320"></a></var><br>
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<blockquote><p>True if a function's return statements should be checked for matching the function's return type. This includes checking for falling off the end of a non-void function. Return false if no such check should be made.
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</p></blockquote></div>
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