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119 lines
5.8 KiB
HTML
119 lines
5.8 KiB
HTML
4 years ago
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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
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<html>
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<!-- Copyright (C) 1988-2018 Free Software Foundation, Inc.
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Permission is granted to copy, distribute and/or modify this document
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under the terms of the GNU Free Documentation License, Version 1.3 or
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any later version published by the Free Software Foundation; with the
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Invariant Sections being "Funding Free Software", the Front-Cover
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Texts being (a) (see below), and with the Back-Cover Texts being (b)
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(see below). A copy of the license is included in the section entitled
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"GNU Free Documentation License".
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(a) The FSF's Front-Cover Text is:
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A GNU Manual
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(b) The FSF's Back-Cover Text is:
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You have freedom to copy and modify this GNU Manual, like GNU
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software. Copies published by the Free Software Foundation raise
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funds for GNU development. -->
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<!-- Created by GNU Texinfo 6.4, http://www.gnu.org/software/texinfo/ -->
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<head>
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<title>Tail Calls (GNU Compiler Collection (GCC) Internals)</title>
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<meta name="description" content="Tail Calls (GNU Compiler Collection (GCC) Internals)">
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<meta name="keywords" content="Tail Calls (GNU Compiler Collection (GCC) Internals)">
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<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
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<link href="index.html#Top" rel="start" title="Top">
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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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<link href="Stack-and-Calling.html#Stack-and-Calling" rel="up" title="Stack and Calling">
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<link href="Shrink_002dwrapping-separate-components.html#Shrink_002dwrapping-separate-components" rel="next" title="Shrink-wrapping separate components">
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<link href="Profiling.html#Profiling" rel="prev" title="Profiling">
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</style>
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</head>
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<body lang="en">
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<a name="Tail-Calls"></a>
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<div class="header">
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<p>
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Next: <a href="Shrink_002dwrapping-separate-components.html#Shrink_002dwrapping-separate-components" accesskey="n" rel="next">Shrink-wrapping separate components</a>, Previous: <a href="Profiling.html#Profiling" accesskey="p" rel="prev">Profiling</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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</div>
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<hr>
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<a name="Permitting-tail-calls"></a>
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<h4 class="subsection">18.9.13 Permitting tail calls</h4>
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<a name="index-tail-calls"></a>
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<dl>
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<dt><a name="index-TARGET_005fFUNCTION_005fOK_005fFOR_005fSIBCALL"></a>Target Hook: <em>bool</em> <strong>TARGET_FUNCTION_OK_FOR_SIBCALL</strong> <em>(tree <var>decl</var>, tree <var>exp</var>)</em></dt>
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<dd><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>
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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></dd></dl>
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<dl>
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<dt><a name="index-TARGET_005fEXTRA_005fLIVE_005fON_005fENTRY"></a>Target Hook: <em>void</em> <strong>TARGET_EXTRA_LIVE_ON_ENTRY</strong> <em>(bitmap <var>regs</var>)</em></dt>
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<dd><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></dd></dl>
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<dl>
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<dt><a name="index-TARGET_005fSET_005fUP_005fBY_005fPROLOGUE"></a>Target Hook: <em>void</em> <strong>TARGET_SET_UP_BY_PROLOGUE</strong> <em>(struct hard_reg_set_container *<var></var>)</em></dt>
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<dd><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></dd></dl>
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<dl>
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<dt><a name="index-TARGET_005fWARN_005fFUNC_005fRETURN"></a>Target Hook: <em>bool</em> <strong>TARGET_WARN_FUNC_RETURN</strong> <em>(tree)</em></dt>
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<dd><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></dd></dl>
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</body>
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</html>
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