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135 lines
5.6 KiB
HTML
135 lines
5.6 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>Gcov-tool Intro (Using the GNU Compiler Collection (GCC))</title>
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<meta name="description" content="Gcov-tool Intro (Using the GNU Compiler Collection (GCC))">
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<meta name="keywords" content="Gcov-tool Intro (Using the GNU Compiler Collection (GCC))">
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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="Gcov_002dtool.html#Gcov_002dtool" rel="up" title="Gcov-tool">
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<link href="Invoking-Gcov_002dtool.html#Invoking-Gcov_002dtool" rel="next" title="Invoking Gcov-tool">
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<link href="Gcov_002dtool.html#Gcov_002dtool" rel="prev" title="Gcov-tool">
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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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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">
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<a name="Gcov_002dtool-Intro"></a>
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<div class="header">
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<p>
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Next: <a href="Invoking-Gcov_002dtool.html#Invoking-Gcov_002dtool" accesskey="n" rel="next">Invoking Gcov-tool</a>, Up: <a href="Gcov_002dtool.html#Gcov_002dtool" accesskey="u" rel="up">Gcov-tool</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="Introduction-to-gcov_002dtool"></a>
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<h3 class="section">11.1 Introduction to <code>gcov-tool</code></h3>
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<p><code>gcov-tool</code> is an offline tool to process gcc’s gcda profile files.
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</p>
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<p>Current gcov-tool supports the following functionalities:
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</p>
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<ul>
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<li> merge two sets of profiles with weights.
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</li><li> read one set of profile and rewrite profile contents. One can scale or
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normalize the count values.
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</li></ul>
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<p>Examples of the use cases for this tool are:
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</p><ul>
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<li> Collect the profiles for different set of inputs, and use this tool to merge
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them. One can specify the weight to factor in the relative importance of
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each input.
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</li><li> Rewrite the profile after removing a subset of the gcda files, while maintaining
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the consistency of the summary and the histogram.
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</li><li> It can also be used to debug or libgcov code as the tools shares the majority
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code as the runtime library.
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</li></ul>
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<p>Note that for the merging operation, this profile generated offline may
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contain slight different values from the online merged profile. Here are
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a list of typical differences:
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</p>
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<ul>
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<li> histogram difference: This offline tool recomputes the histogram after merging
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the counters. The resulting histogram, therefore, is precise. The online
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merging does not have this capability – the histogram is merged from two
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histograms and the result is an approximation.
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</li><li> summary checksum difference: Summary checksum uses a CRC32 operation. The value
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depends on the link list order of gcov-info objects. This order is different in
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gcov-tool from that in the online merge. It’s expected to have different
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summary checksums. It does not really matter as the compiler does not use this
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checksum anywhere.
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</li><li> value profile counter values difference: Some counter values for value profile
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are runtime dependent, like heap addresses. It’s normal to see some difference
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in these kind of counters.
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</li></ul>
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<hr>
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<div class="header">
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<p>
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Next: <a href="Invoking-Gcov_002dtool.html#Invoking-Gcov_002dtool" accesskey="n" rel="next">Invoking Gcov-tool</a>, Up: <a href="Gcov_002dtool.html#Gcov_002dtool" accesskey="u" rel="up">Gcov-tool</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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</body>
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</html>
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