117 lines
4.9 KiB
HTML
117 lines
4.9 KiB
HTML
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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) 1988-2016 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 5.2, http://www.gnu.org/software/texinfo/ -->
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<head>
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<title>GNU Compiler Collection (GCC) Internals: Debug Information</title>
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<meta name="description" content="GNU Compiler Collection (GCC) Internals: Debug Information">
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<meta name="keywords" content="GNU Compiler Collection (GCC) Internals: Debug Information">
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<meta name="resource-type" content="document">
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<meta name="distribution" content="global">
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<meta name="Generator" content="makeinfo">
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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="RTL.html#RTL" rel="up" title="RTL">
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<link href="Insns.html#Insns" rel="next" title="Insns">
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<link href="Assembler.html#Assembler" rel="prev" title="Assembler">
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<style type="text/css">
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<!--
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a.summary-letter {text-decoration: none}
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kbd {font-style:oblique}
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pre.display {font-family: inherit}
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pre.smalldisplay {font-family: inherit; font-size: smaller}
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span.nocodebreak {white-space:nowrap}
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span.nolinebreak {white-space:nowrap}
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span.roman {font-family:serif; font-weight:normal}
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span.sansserif {font-family:sans-serif; font-weight:normal}
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ul.no-bullet {list-style: none}
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-->
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</style>
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</head>
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<body lang="en" bgcolor="#FFFFFF" text="#000000" link="#0000FF" vlink="#800080" alink="#FF0000">
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<a name="Debug-Information"></a>
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<div class="header">
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<p>
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Next: <a href="Insns.html#Insns" accesskey="n" rel="next">Insns</a>, Previous: <a href="Assembler.html#Assembler" accesskey="p" rel="prev">Assembler</a>, Up: <a href="RTL.html#RTL" accesskey="u" rel="up">RTL</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="Variable-Location-Debug-Information-in-RTL"></a>
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<h3 class="section">13.18 Variable Location Debug Information in RTL</h3>
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<a name="index-Variable-Location-Debug-Information-in-RTL"></a>
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<p>Variable tracking relies on <code>MEM_EXPR</code> and <code>REG_EXPR</code>
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annotations to determine what user variables memory and register
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references refer to.
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</p>
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<p>Variable tracking at assignments uses these notes only when they refer
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to variables that live at fixed locations (e.g., addressable
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variables, global non-automatic variables). For variables whose
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location may vary, it relies on the following types of notes.
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</p>
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<dl compact="compact">
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<dd><a name="index-var_005flocation"></a>
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</dd>
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<dt><code>(var_location:<var>mode</var> <var>var</var> <var>exp</var> <var>stat</var>)</code></dt>
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<dd><p>Binds variable <code>var</code>, a tree, to value <var>exp</var>, an RTL
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expression. It appears only in <code>NOTE_INSN_VAR_LOCATION</code> and
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<code>DEBUG_INSN</code>s, with slightly different meanings. <var>mode</var>, if
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present, represents the mode of <var>exp</var>, which is useful if it is a
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modeless expression. <var>stat</var> is only meaningful in notes,
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indicating whether the variable is known to be initialized or
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uninitialized.
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</p>
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<a name="index-debug_005fexpr"></a>
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</dd>
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<dt><code>(debug_expr:<var>mode</var> <var>decl</var>)</code></dt>
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<dd><p>Stands for the value bound to the <code>DEBUG_EXPR_DECL</code> <var>decl</var>,
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that points back to it, within value expressions in
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<code>VAR_LOCATION</code> nodes.
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</p>
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</dd>
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</dl>
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</body>
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</html>
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