Regenerate.

[oota-llvm.git] / docs / GoldPlugin.html

diff --git a/docs/GoldPlugin.html b/docs/GoldPlugin.html
index 1a2268f4f72a7b3d5dc4edb9e3b80ddd525c5b62..b5148ab3312edeef34d4448e6f0afbe3e1bfcc86 100644 (file)
--- a/docs/GoldPlugin.html
+++ b/docs/GoldPlugin.html
@@ -11,7 +11,11 @@
 <ol>
   <li><a href="#introduction">Introduction</a></li>
   <li><a href="#build">How to build it</a></li>
-  <li><a href="#usage">Usage</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>
@@ -80,14 +84,104 @@ make all-gold
   linker, which is why you need gold to be the installed system linker in your
   path.</p>
 </div>
+
+<!-- ======================================================================= -->
+<div class="doc_subsection">
+  <a name="example1">Example of link time optimization</a>
+</div>
+
+<div class="doc_text">
+  <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 &lt;stdio.h&gt;
+
+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 &lt;stdio.h&gt;
+
+extern void foo2(void);
+
+void foo1(void) {
+  foo2();
+}
+
+void foo4(void) {
+  printf("Foo4");
+}
+
+--- command lines ---
+$ llvm-gcc -flto a.c -c -o a.o              # &lt;-- a.o is LLVM bitcode file
+$ llvm-gcc b.c -c -o b.o                    # &lt;-- b.o is native object file
+$ llvm-gcc -use-gold-plugin a.o 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="http://llvm.org/docs/LinkTimeOptimization.html#example1">libLTO
+  example</a> gold does not currently eliminate foo4.</p>
+</div>
+
+<!--=========================================================================-->
+<div class="doc_section"><a name="lto_autotools">Quickstart for using LTO with autotooled projects</a></div>
+<!--=========================================================================-->
+<div class="doc_text">
+  <p><tt>gold</tt>, <tt>ar</tt> and <tt>nm</tt> all support plugins now, so everything should be
+  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 libLLVMgold.so</a>.</li>
+    <li>Install the newly built binutils to <tt>$PREFIX</tt></li>
+    <li>Copy <tt>Release/lib/libLLVMgold.so</tt> to
+    <tt>$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"
+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="llvm-gcc -use-gold-plugin"
+export CXX="llvm-g++ -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>
+   </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>
+
 <!--=========================================================================-->
 <div class="doc_section"><a name="licensing">Licensing</a></div>
 <!--=========================================================================-->
 <div class="doc_text">
-Gold is licensed under the GPLv3. LLVMgold uses the interface file
+  <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.
+as much as gold could without the plugin.</p>
 </div>
 
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