diff options
Diffstat (limited to 'docs/GoldPlugin.html')
| -rw-r--r-- | docs/GoldPlugin.html | 63 |
1 files changed, 36 insertions, 27 deletions
diff --git a/docs/GoldPlugin.html b/docs/GoldPlugin.html index e25c45751929..92ba4116a071 100644 --- a/docs/GoldPlugin.html +++ b/docs/GoldPlugin.html @@ -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 # <-- a.o is LLVM bitcode file +$ 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 -$ llvm-gcc b.c -c -o b.o # <-- b.o is native object file -$ llvm-gcc -use-gold-plugin a.a b.o -o main # <-- link with LLVMgold plugin +$ clang b.c -c -o b.o # <-- b.o is native object file +$ clang -use-gold-plugin 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 @@ -158,20 +162,21 @@ $ llvm-gcc -use-gold-plugin a.a b.o -o main # <-- 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 & build the project as usual: <tt>./configure && make && make check</tt> </li> +</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> + + <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> <!--=========================================================================--> |