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92 lines
4.2 KiB
HTML
92 lines
4.2 KiB
HTML
4 years ago
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<title>Pass manager - GNU Compiler Collection (GCC) Internals</title>
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<meta name="description" content="GNU Compiler Collection (GCC) Internals">
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<link title="Top" rel="start" href="index.html#Top">
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<link rel="up" href="Passes.html#Passes" title="Passes">
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<link rel="prev" href="Gimplification-pass.html#Gimplification-pass" title="Gimplification pass">
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<link rel="next" href="Tree-SSA-passes.html#Tree-SSA-passes" title="Tree SSA passes">
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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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(a) The FSF's Front-Cover Text is:
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A GNU Manual
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</head>
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<body>
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<div class="node">
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<a name="Pass-manager"></a>
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<p>
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Next: <a rel="next" accesskey="n" href="Tree-SSA-passes.html#Tree-SSA-passes">Tree SSA passes</a>,
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Previous: <a rel="previous" accesskey="p" href="Gimplification-pass.html#Gimplification-pass">Gimplification pass</a>,
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Up: <a rel="up" accesskey="u" href="Passes.html#Passes">Passes</a>
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<hr>
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</div>
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<h3 class="section">9.4 Pass manager</h3>
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<p>The pass manager is located in <samp><span class="file">passes.c</span></samp>, <samp><span class="file">tree-optimize.c</span></samp>
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and <samp><span class="file">tree-pass.h</span></samp>.
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It processes passes as described in <samp><span class="file">passes.def</span></samp>.
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Its job is to run all of the individual passes in the correct order,
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and take care of standard bookkeeping that applies to every pass.
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<p>The theory of operation is that each pass defines a structure that
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represents everything we need to know about that pass—when it
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should be run, how it should be run, what intermediate language
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form or on-the-side data structures it needs. We register the pass
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to be run in some particular order, and the pass manager arranges
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for everything to happen in the correct order.
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<p>The actuality doesn't completely live up to the theory at present.
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Command-line switches and <code>timevar_id_t</code> enumerations must still
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be defined elsewhere. The pass manager validates constraints but does
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not attempt to (re-)generate data structures or lower intermediate
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language form based on the requirements of the next pass. Nevertheless,
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what is present is useful, and a far sight better than nothing at all.
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<p>Each pass should have a unique name.
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Each pass may have its own dump file (for GCC debugging purposes).
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Passes with a name starting with a star do not dump anything.
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Sometimes passes are supposed to share a dump file / option name.
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To still give these unique names, you can use a prefix that is delimited
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by a space from the part that is used for the dump file / option name.
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E.g. When the pass name is "ud dce", the name used for dump file/options
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is "dce".
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<p>TODO: describe the global variables set up by the pass manager,
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and a brief description of how a new pass should use it.
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I need to look at what info RTL passes use first<small class="enddots">...</small>
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</body></html>
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