<html lang="en">
<head>
<title>Pass manager - GNU Compiler Collection (GCC) Internals</title>
<meta http-equiv="Content-Type" content="text/html">
<meta name="description" content="GNU Compiler Collection (GCC) Internals">
<meta name="generator" content="makeinfo 4.13">
<link title="Top" rel="start" href="index.html#Top">
<link rel="up" href="Passes.html#Passes" title="Passes">
<link rel="prev" href="Gimplification-pass.html#Gimplification-pass" title="Gimplification pass">
<link rel="next" href="Tree-SSA-passes.html#Tree-SSA-passes" title="Tree SSA passes">
<link href="http://www.gnu.org/software/texinfo/" rel="generator-home" title="Texinfo Homepage">
<!--
Copyright (C) 1988-2015 Free Software Foundation, Inc.
Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.3 or
any later version published by the Free Software Foundation; with the
Invariant Sections being ``Funding Free Software'', the Front-Cover
Texts being (a) (see below), and with the Back-Cover Texts being (b)
(see below). A copy of the license is included in the section entitled
``GNU Free Documentation License''.
(a) The FSF's Front-Cover Text is:
A GNU Manual
(b) The FSF's Back-Cover Text is:
You have freedom to copy and modify this GNU Manual, like GNU
software. Copies published by the Free Software Foundation raise
funds for GNU development.-->
<meta http-equiv="Content-Style-Type" content="text/css">
<style type="text/css"><!--
pre.display { font-family:inherit }
pre.format { font-family:inherit }
pre.smalldisplay { font-family:inherit; font-size:smaller }
pre.smallformat { font-family:inherit; font-size:smaller }
pre.smallexample { font-size:smaller }
pre.smalllisp { font-size:smaller }
span.sc { font-variant:small-caps }
span.roman { font-family:serif; font-weight:normal; }
span.sansserif { font-family:sans-serif; font-weight:normal; }
--></style>
</head>
<body>
<div class="node">
<a name="Pass-manager"></a>
<p>
Next: <a rel="next" accesskey="n" href="Tree-SSA-passes.html#Tree-SSA-passes">Tree SSA passes</a>,
Previous: <a rel="previous" accesskey="p" href="Gimplification-pass.html#Gimplification-pass">Gimplification pass</a>,
Up: <a rel="up" accesskey="u" href="Passes.html#Passes">Passes</a>
<hr>
</div>
<h3 class="section">9.4 Pass manager</h3>
<p>The pass manager is located in <samp><span class="file">passes.c</span></samp>, <samp><span class="file">tree-optimize.c</span></samp>
and <samp><span class="file">tree-pass.h</span></samp>.
It processes passes as described in <samp><span class="file">passes.def</span></samp>.
Its job is to run all of the individual passes in the correct order,
and take care of standard bookkeeping that applies to every pass.
<p>The theory of operation is that each pass defines a structure that
represents everything we need to know about that pass—when it
should be run, how it should be run, what intermediate language
form or on-the-side data structures it needs. We register the pass
to be run in some particular order, and the pass manager arranges
for everything to happen in the correct order.
<p>The actuality doesn't completely live up to the theory at present.
Command-line switches and <code>timevar_id_t</code> enumerations must still
be defined elsewhere. The pass manager validates constraints but does
not attempt to (re-)generate data structures or lower intermediate
language form based on the requirements of the next pass. Nevertheless,
what is present is useful, and a far sight better than nothing at all.
<p>Each pass should have a unique name.
Each pass may have its own dump file (for GCC debugging purposes).
Passes with a name starting with a star do not dump anything.
Sometimes passes are supposed to share a dump file / option name.
To still give these unique names, you can use a prefix that is delimited
by a space from the part that is used for the dump file / option name.
E.g. When the pass name is "ud dce", the name used for dump file/options
is "dce".
<p>TODO: describe the global variables set up by the pass manager,
and a brief description of how a new pass should use it.
I need to look at what info RTL passes use first<small class="enddots">...</small>
</body></html>