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Remove mention of llvm-gcc/llvm-g++ from doc.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@139998 91177308-0d34-0410-b5e6-96231b3b80d8
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Bill Wendling 2011-09-18 12:37:20 +00:00
parent 91e43fd17a
commit ea55c83e7f
1 changed files with 36 additions and 27 deletions
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63
docs/GoldPlugin.html
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@ -75,6 +75,7 @@ placed.
<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
@ -82,19 +83,21 @@ placed.
<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>llvm-gcc</tt> using
<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><tt>llvm-gcc</tt> has a <tt>-use-gold-plugin</tt> option which looks
for the gold plugin in the same directories as it looks for <tt>cc1</tt> and
passes the <tt>-plugin</tt> option to ld. It will not look for an alternate
<p><tt>Clang</tt> has a <tt>-use-gold-plugin</tt> option which looks for the
gold plugin in the same directories as it looks for <tt>cc1</tt> and passes
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>
<tt>/usr/bin</tt>.<p>
<!-- ======================================================================= -->
<h3>
@ -137,11 +140,12 @@ void foo4(void) {
}
--- command lines ---
$ llvm-gcc -flto a.c -c -o a.o # &lt;-- a.o is LLVM bitcode file
$ clang -flto a.c -c -o a.o # &lt;-- a.o is LLVM bitcode file
$ ar q a.a a.o # &lt;-- a.a is an archive with LLVM bitcode
$ llvm-gcc b.c -c -o b.o # &lt;-- b.o is native object file
$ llvm-gcc -use-gold-plugin a.a b.o -o main # &lt;-- link with LLVMgold plugin
$ clang b.c -c -o b.o # &lt;-- b.o is native object file
$ clang -use-gold-plugin a.a b.o -o main # &lt;-- 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
@ -158,20 +162,21 @@ $ llvm-gcc -use-gold-plugin a.a b.o -o main # &lt;-- link with LLVMgold plugin
</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>
<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/libexec/gcc/x86_64-unknown-linux-gnu/4.2.1/</tt> and
<tt>$PREFIX/lib/bfd-plugins/</tt></li>
<li>Set environment variables (<tt>$PREFIX</tt> is where you installed llvm-gcc and
binutils):
<pre class="doc_code">
export CC="$PREFIX/bin/llvm-gcc -use-gold-plugin"
export CXX="$PREFIX/bin/llvm-g++ -use-gold-plugin"
<tt>$PREFIX/libexec/gcc/x86_64-unknown-linux-gnu/4.2.1/</tt> and
<tt>$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 -use-gold-plugin"
export CXX="$PREFIX/bin/clang++ -use-gold-plugin"
export AR="$PREFIX/bin/ar"
export NM="$PREFIX/bin/nm"
export RANLIB=/bin/true #ranlib is not needed, and doesn't support .bc files in .a
@ -179,18 +184,22 @@ export CFLAGS="-O4"
</pre>
</li>
<li>Or you can just set your path:
<pre class="doc_code">
<pre class="doc_code">
export PATH="$PREFIX/bin:$PATH"
export CC="llvm-gcc -use-gold-plugin"
export CXX="llvm-g++ -use-gold-plugin"
export CC="clang -use-gold-plugin"
export CXX="clang++ -use-gold-plugin"
export RANLIB=/bin/true
export CFLAGS="-O4"
</pre>
</li>
<li>Configure &amp; build the project as usual: <tt>./configure &amp;&amp; make &amp;&amp; make check</tt> </li>
</pre></li>
<li>Configure &amp; build the project as usual:
<pre class="doc_code">
% ./configure &amp;&amp; make &amp;&amp; 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>
<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>
<!--=========================================================================-->