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98 lines
4.7 KiB
HTML
98 lines
4.7 KiB
HTML
4 years ago
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<html lang="en">
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<head>
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<title>GENERIC - GNU Compiler Collection (GCC) Internals</title>
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<meta http-equiv="Content-Type" content="text/html">
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<meta name="description" content="GNU Compiler Collection (GCC) Internals">
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<meta name="generator" content="makeinfo 4.13">
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<link title="Top" rel="start" href="index.html#Top">
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<link rel="prev" href="Passes.html#Passes" title="Passes">
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<link rel="next" href="GIMPLE.html#GIMPLE" title="GIMPLE">
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<link href="http://www.gnu.org/software/texinfo/" rel="generator-home" title="Texinfo Homepage">
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<!--
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Copyright (C) 1988-2015 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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<meta http-equiv="Content-Style-Type" content="text/css">
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<style type="text/css"><!--
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pre.display { font-family:inherit }
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pre.format { font-family:inherit }
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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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--></style>
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</head>
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<body>
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<div class="node">
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<a name="GENERIC"></a>
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<p>
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Next: <a rel="next" accesskey="n" href="GIMPLE.html#GIMPLE">GIMPLE</a>,
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Previous: <a rel="previous" accesskey="p" href="Passes.html#Passes">Passes</a>,
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Up: <a rel="up" accesskey="u" href="index.html#Top">Top</a>
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<hr>
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</div>
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<h2 class="chapter">10 GENERIC</h2>
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<p><a name="index-GENERIC-1712"></a>
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The purpose of GENERIC is simply to provide a
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language-independent way of representing an entire function in
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trees. To this end, it was necessary to add a few new tree codes
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to the back end, but almost everything was already there. If you
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can express it with the codes in <code>gcc/tree.def</code>, it's
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GENERIC.
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<p>Early on, there was a great deal of debate about how to think
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about statements in a tree IL. In GENERIC, a statement is
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defined as any expression whose value, if any, is ignored. A
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statement will always have <code>TREE_SIDE_EFFECTS</code> set (or it
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will be discarded), but a non-statement expression may also have
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side effects. A <code>CALL_EXPR</code>, for instance.
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<p>It would be possible for some local optimizations to work on the
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GENERIC form of a function; indeed, the adapted tree inliner
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works fine on GENERIC, but the current compiler performs inlining
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after lowering to GIMPLE (a restricted form described in the next
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section). Indeed, currently the frontends perform this lowering
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before handing off to <code>tree_rest_of_compilation</code>, but this
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seems inelegant.
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<ul class="menu">
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<li><a accesskey="1" href="Deficiencies.html#Deficiencies">Deficiencies</a>: Topics net yet covered in this document.
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<li><a accesskey="2" href="Tree-overview.html#Tree-overview">Tree overview</a>: All about <code>tree</code>s.
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<li><a accesskey="3" href="Types.html#Types">Types</a>: Fundamental and aggregate types.
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<li><a accesskey="4" href="Declarations.html#Declarations">Declarations</a>: Type declarations and variables.
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<li><a accesskey="5" href="Attributes.html#Attributes">Attributes</a>: Declaration and type attributes.
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<li><a accesskey="6" href="Expression-trees.html#Expression-trees">Expressions</a>: Operating on data.
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<li><a accesskey="7" href="Statements.html#Statements">Statements</a>: Control flow and related trees.
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<li><a accesskey="8" href="Functions.html#Functions">Functions</a>: Function bodies, linkage, and other aspects.
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<li><a accesskey="9" href="Language_002ddependent-trees.html#Language_002ddependent-trees">Language-dependent trees</a>: Topics and trees specific to language front ends.
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<li><a href="C-and-C_002b_002b-Trees.html#C-and-C_002b_002b-Trees">C and C++ Trees</a>: Trees specific to C and C++.
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<li><a href="Java-Trees.html#Java-Trees">Java Trees</a>: Trees specific to Java.
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</ul>
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<!-- -->
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<!-- Deficiencies -->
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<!-- -->
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</body></html>
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