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diff --git a/docs/GoldPlugin.html b/docs/GoldPlugin.html deleted file mode 100644 index 1e99a5a..0000000 --- a/docs/GoldPlugin.html +++ /dev/null @@ -1,227 +0,0 @@ -<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" - "http://www.w3.org/TR/html4/strict.dtd"> -<html> -<head> - <meta http-equiv="Content-Type" content="text/html; charset=utf-8"> - <title>LLVM gold plugin</title> - <link rel="stylesheet" href="_static/llvm.css" type="text/css"> -</head> -<body> - -<h1>LLVM gold plugin</h1> -<ol> - <li><a href="#introduction">Introduction</a></li> - <li><a href="#build">How to build it</a></li> - <li><a href="#usage">Usage</a> - <ul> - <li><a href="#example1">Example of link time optimization</a></li> - <li><a href="#lto_autotools">Quickstart for using LTO with autotooled projects</a></li> - </ul></li> - <li><a href="#licensing">Licensing</a></li> -</ol> -<div class="doc_author">Written by Nick Lewycky</div> - -<!--=========================================================================--> -<h2><a name="introduction">Introduction</a></h2> -<!--=========================================================================--> -<div> - <p>Building with link time optimization requires cooperation from the -system linker. LTO support on Linux systems requires that you use -the <a href="http://sourceware.org/binutils">gold linker</a> which supports -LTO via plugins. This is the same mechanism used by the -<a href="http://gcc.gnu.org/wiki/LinkTimeOptimization">GCC LTO</a> -project.</p> - <p>The LLVM gold plugin implements the -<a href="http://gcc.gnu.org/wiki/whopr/driver">gold plugin interface</a> -on top of -<a href="LinkTimeOptimization.html#lto">libLTO</a>. -The same plugin can also be used by other tools such as <tt>ar</tt> and -<tt>nm</tt>. -</div> -<!--=========================================================================--> -<h2><a name="build">How to build it</a></h2> -<!--=========================================================================--> -<div> - <p>You need to have gold with plugin support and build the LLVMgold -plugin. Check whether you have gold running <tt>/usr/bin/ld -v</tt>. It will -report “GNU gold” or else “GNU ld” if not. If you have -gold, check for plugin support by running <tt>/usr/bin/ld -plugin</tt>. If it -complains “missing argument” then you have plugin support. If not, -such as an “unknown option” error then you will either need to -build gold or install a version with plugin support.</p> -<ul> - <li>To build gold with plugin support: - <pre class="doc_code"> -mkdir binutils -cd binutils -cvs -z 9 -d :pserver:anoncvs@sourceware.org:/cvs/src login -<em>{enter "anoncvs" as the password}</em> -cvs -z 9 -d :pserver:anoncvs@sourceware.org:/cvs/src co binutils -mkdir build -cd build -../src/configure --enable-gold --enable-plugins -make all-gold -</pre> - That should leave you with <tt>binutils/build/gold/ld-new</tt> which supports the <tt>-plugin</tt> option. It also built would have -<tt>binutils/build/binutils/ar</tt> and <tt>nm-new</tt> which support plugins -but don't have a visible -plugin option, instead relying on the gold plugin -being present in <tt>../lib/bfd-plugins</tt> relative to where the binaries are -placed. - <li>Build the LLVMgold plugin: Configure LLVM with - <tt>--with-binutils-include=/path/to/binutils/src/include</tt> and run - <tt>make</tt>. -</ul> -</div> -<!--=========================================================================--> -<h2><a name="usage">Usage</a></h2> -<!--=========================================================================--> -<div> - - <p>The linker takes a <tt>-plugin</tt> option that points to the path of - the plugin <tt>.so</tt> file. To find out what link command <tt>gcc</tt> - would run in a given situation, run <tt>gcc -v <em>[...]</em></tt> and look - for the line where it runs <tt>collect2</tt>. Replace that with - <tt>ld-new -plugin /path/to/LLVMgold.so</tt> to test it out. Once you're - ready to switch to using gold, backup your existing <tt>/usr/bin/ld</tt> - then replace it with <tt>ld-new</tt>.</p> - - <p>You can produce bitcode files from <tt>clang</tt> using - <tt>-emit-llvm</tt> or <tt>-flto</tt>, or the <tt>-O4</tt> flag which is - synonymous with <tt>-O3 -flto</tt>.</p> - - <p>Any of these flags will also cause <tt>clang</tt> to look for the - gold plugin in the <tt>lib</tt> directory under its prefix and pass the - <tt>-plugin</tt> option to <tt>ld</tt>. It will not look for an alternate - linker, which is why you need gold to be the installed system linker in - your path.</p> - - <p>If you want <tt>ar</tt> and <tt>nm</tt> to work seamlessly as well, install - <tt>LLVMgold.so</tt> to <tt>/usr/lib/bfd-plugins</tt>. If you built your - own gold, be sure to install the <tt>ar</tt> and <tt>nm-new</tt> you built to - <tt>/usr/bin</tt>.<p> - -<!-- ======================================================================= --> -<h3> - <a name="example1">Example of link time optimization</a> -</h3> - -<div> - <p>The following example shows a worked example of the gold plugin mixing - LLVM bitcode and native code. -<pre class="doc_code"> ---- a.c --- -#include <stdio.h> - -extern void foo1(void); -extern void foo4(void); - -void foo2(void) { - printf("Foo2\n"); -} - -void foo3(void) { - foo4(); -} - -int main(void) { - foo1(); -} - ---- b.c --- -#include <stdio.h> - -extern void foo2(void); - -void foo1(void) { - foo2(); -} - -void foo4(void) { - printf("Foo4"); -} - ---- command lines --- -$ clang -flto a.c -c -o a.o # <-- a.o is LLVM bitcode file -$ ar q a.a a.o # <-- a.a is an archive with LLVM bitcode -$ clang b.c -c -o b.o # <-- b.o is native object file -$ clang -flto a.a b.o -o main # <-- link with LLVMgold plugin -</pre> - - <p>Gold informs the plugin that foo3 is never referenced outside the IR, - leading LLVM to delete that function. However, unlike in the - <a href="LinkTimeOptimization.html#example1">libLTO - example</a> gold does not currently eliminate foo4.</p> -</div> - -</div> - -<!--=========================================================================--> -<h2> - <a name="lto_autotools"> - Quickstart for using LTO with autotooled projects - </a> -</h2> -<!--=========================================================================--> -<div> - <p>Once your system <tt>ld</tt>, <tt>ar</tt>, and <tt>nm</tt> all support LLVM - bitcode, everything is in place for an easy to use LTO build of autotooled - projects:</p> - - <ul> - <li>Follow the instructions <a href="#build">on how to build LLVMgold.so</a>.</li> - <li>Install the newly built binutils to <tt>$PREFIX</tt></li> - <li>Copy <tt>Release/lib/LLVMgold.so</tt> to - <tt>$PREFIX/lib/bfd-plugins/</tt></li> - <li>Set environment variables (<tt>$PREFIX</tt> is where you installed clang and - binutils): -<pre class="doc_code"> -export CC="$PREFIX/bin/clang -flto" -export CXX="$PREFIX/bin/clang++ -flto" -export AR="$PREFIX/bin/ar" -export NM="$PREFIX/bin/nm" -export RANLIB=/bin/true #ranlib is not needed, and doesn't support .bc files in .a -export CFLAGS="-O4" -</pre> - </li> - <li>Or you can just set your path: -<pre class="doc_code"> -export PATH="$PREFIX/bin:$PATH" -export CC="clang -flto" -export CXX="clang++ -flto" -export RANLIB=/bin/true -export CFLAGS="-O4" -</pre></li> - <li>Configure & build the project as usual: -<pre class="doc_code"> -% ./configure && make && make check -</pre></li> - </ul> - - <p>The environment variable settings may work for non-autotooled projects - too, but you may need to set the <tt>LD</tt> environment variable as - well.</p> -</div> - -<!--=========================================================================--> -<h2><a name="licensing">Licensing</a></h2> -<!--=========================================================================--> -<div> - <p>Gold is licensed under the GPLv3. LLVMgold uses the interface file -<tt>plugin-api.h</tt> from gold which means that the resulting LLVMgold.so -binary is also GPLv3. This can still be used to link non-GPLv3 programs just -as much as gold could without the plugin.</p> -</div> - -<!-- *********************************************************************** --> -<hr> -<address> - <a href="http://jigsaw.w3.org/css-validator/check/referer"><img - src="http://jigsaw.w3.org/css-validator/images/vcss-blue" alt="Valid CSS"></a> - <a href="http://validator.w3.org/check/referer"><img - src="http://www.w3.org/Icons/valid-html401-blue" alt="Valid HTML 4.01"></a> - <a href="mailto:nicholas@metrix.on.ca">Nick Lewycky</a><br> - <a href="http://llvm.org/">The LLVM Compiler Infrastructure</a><br> - Last modified: $Date: 2010-04-16 23:58:21 -0800 (Fri, 16 Apr 2010) $ -</address> -</body> -</html> |
