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gerrit-public.fairphone.software / fp2-dev / platform / external / llvm / ebc6765970b96434eaa8c2254a9038113313065d / . / docs / GoldPlugin.html
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3<html>
4<head>
5 <title>LLVM gold plugin</title>
6 <link rel="stylesheet" href="llvm.css" type="text/css">
7</head>
8<body>
9
10<div class="doc_title">LLVM gold plugin</div>
11<ol>
12 <li><a href="#introduction">Introduction</a></li>
13 <li><a href="#build">How to build it</a></li>
14 <li><a href="#usage">Usage</a></li>
15 <li><a href="#licensing">Licensing</a></li>
16</ol>
17<div class="doc_author">Written by Nick Lewycky</div>
18
19<!--=========================================================================-->
20<div class="doc_section"><a name="introduction">Introduction</a></div>
21<!--=========================================================================-->
22<div class="doc_text">
23 <p>Building with link time optimization requires cooperation with the
24system linker. To support LTO on Linux systems, we requires that you use
25<a href="http://sourceware.org/binutils">gold</a> which has support for
26LTO via plugins. This is the same system used by the upcoming
27<a href="http://gcc.gnu.org/wiki/LinkTimeOptimization">GCC LTO</a>
28support.</p>
29 <p>The LLVMgold plugin implements the gold
30<a href="http://gcc.gnu.org/wiki/whopr/driver">plugin interface</a> on
31top of
32<a href="http://llvm.org/docs/LinkTimeOptimization.html#lto">libLTO</a>.
33The same plugin can also be used by other tools such as <tt>ar</tt> and
34<tt>nm</tt>.
35</div>
36<!--=========================================================================-->
37<div class="doc_section"><a name="build">How to build it</a></div>
38<!--=========================================================================-->
39<div class="doc_text">
40 <p>You need to build gold with plugin support and build the LLVMgold
41plugin.</p>
42<ul>
43 <li>Build gold with plugin support:
44 <pre class="doc_code">
45mkdir binutils
46cd binutils
47cvs -z 9 -d :pserver:anoncvs@sourceware.org:/cvs/src login
48<em>{enter "anoncvs" as the password}</em>
49cvs -z 9 -d :pserver:anoncvs@sourceware.org:/cvs/src co src
50mkdir build
51cd build
52../src/configure --enable-gold --enable-plugins
53make all-gold
54</pre>
55 That should leave you with binutils/build/gold/ld-new which supports the
56-plugin option.
57
58 <li>Build LLVMgold. Configure LLVM with
59 <tt>--with-binutils-include=/path/to/binutils/src/include</tt> and run
60 <tt>make</tt>.
61</ul>
62</div>
63<!--=========================================================================-->
64<div class="doc_section"><a name="usage">Usage</a></div>
65<!--=========================================================================-->
66<div class="doc_text">
67 <p>The linker takes a <tt>-plugin</tt> option that points to the path of
68 the plugin <tt>.so</tt> file. To find out what link command <tt>gcc</tt>
69 would run in a given situation, run <tt>gcc -v <em>[...]</em></tt> and look
70 for the line where it runs <tt>collect2</tt>. Replace that with
71 <tt>ld-new -plugin /path/to/LLVMgold.so</tt> to test it out. Once you're
72 ready to switch to using gold, backup your existing <tt>/usr/bin/ld</tt>
73 then replace it with <tt>ld-new</tt>.</p>
74 <p>You can produce bitcode files from <tt>llvm-gcc</tt> using
75 <tt>-emit-llvm</tt> or <tt>-flto</tt> or <tt>-O4</tt> which is equivalent
76 to <tt>-O3 -flto</tt>.</p>
77 <p><tt>llvm-gcc</tt> has a <tt>-use-gold-plugin</tt> option which looks
78 for the gold plugin in the same directories as it looks for <tt>cc1</tt>.
79 It will not look for an alternate linker, which is why you need gold to be
80 the installed system linker in your path.</p>
81</div>
82<!--=========================================================================-->
83<div class="doc_section"><a name="licensing">Licensing</a></div>
84<!--=========================================================================-->
85<div class="doc_text">
86Gold is licensed under the GPLv3. LLVMgold uses the interface file
87<tt>plugin-api.h</tt> from gold which means that the resulting LLVMgold.so
88binary is also GPLv3. This can still be used to link non-GPLv3 programs just
89as much as gold could without the plugin.
90</div>
91
92<!-- *********************************************************************** -->
93<hr>
94<address>
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99 Written by the
100 <a href="mailto:nicholas@metrix.on.ca">Nick Lewycky</a><br>
101 <a href="http://llvm.org">The LLVM Compiler Infrastructure</a><br>
102 Last modified: $Date: 2009-01-01 23:10:51 -0800 (Thu, 01 Jan 2009) $
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