www/get_started.html - platform/external/clang - Gitiles

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 <h1>Getting Started: Building and Running Clang</h1>

 <p>This page gives you the shortest path to checking out Clang and demos a few
 options.  This should get you up and running with the minimum of muss and fuss.
 If you like what you see, please consider <a href="get_involved.html">getting
 involved</a> with the Clang community.  If you run into problems, please file
 bugs in <a href="http://llvm.org/bugs/">LLVM Bugzilla</a>.</p>

 <h2 id="download">Release Clang Versions</h2>

 <p>Clang is released as part of regular LLVM releases. You can download the release versions from <a href="http://llvm.org/releases/">http://llvm.org/releases/</a>.</p>
 <p>Clang is also provided in all major BSD or GNU/Linux distributions as part of their respective packaging systems. From Xcode 4.2, Clang is the default compiler for Mac OS X.</p>

 <h2 id="build">Building Clang and Working with the Code</h2>

 <h3 id="buildNix">On Unix-like Systems</h3>

 <p>If you would like to check out and build Clang, the current procedure is as
 follows:</p>

 <ol>
   <li>Get the required tools.
   <ul>
     <li>See
       <a href="http://llvm.org/docs/GettingStarted.html#requirements">
       Getting Started with the LLVM System - Requirements</a>.</li>
     <li>Note also that Python is needed for running the test suite.
       Get it at: <a href="http://www.python.org/download">
       http://www.python.org/download</a></li>
     <li>Standard build process uses CMake. Get it at:
       <a href="http://www.cmake.org/download">
       http://www.cmake.org/download</a></li>
   </ul>

   <li>Check out LLVM:
   <ul>
     <li>Change directory to where you want the llvm directory placed.</li>
     <li><tt>svn co http://llvm.org/svn/llvm-project/llvm/trunk llvm</tt></li>
   </ul>
   </li>
   <li>Check out Clang:
   <ul>
     <li><tt>cd llvm/tools</tt></li>
     <li><tt>svn co http://llvm.org/svn/llvm-project/cfe/trunk clang</tt></li>
     <li><tt>cd ../..</tt></li>
   </ul>
   </li>
   <li>Check out extra Clang tools: (optional)
   <ul>
     <li><tt>cd llvm/tools/clang/tools</tt></li>
     <li><tt>svn co http://llvm.org/svn/llvm-project/clang-tools-extra/trunk
         extra</tt></li>
     <li><tt>cd ../../../..</tt></li>
   </ul>
   </li>
   <li>Check out Compiler-RT (optional):
   <ul>
     <li><tt>cd llvm/projects</tt></li>
     <li><tt>svn co http://llvm.org/svn/llvm-project/compiler-rt/trunk
         compiler-rt</tt></li>
     <li><tt>cd ../..</tt></li>
   </ul>
   </li>
   <li>Check out libcxx: (only required to build and run Compiler-RT tests on OS X, optional otherwise)
   <ul>
     <li><tt>cd llvm/projects</tt></li>
     <li><tt>svn co http://llvm.org/svn/llvm-project/libcxx/trunk
         libcxx</tt></li>
     <li><tt>cd ../..</tt></li>
   </ul>
   </li>
   <li>Build LLVM and Clang:
   <ul>
     <li><tt>mkdir build</tt> (in-tree build is not supported)</li>
     <li><tt>cd build</tt></li>
     <li><tt>cmake -G "Unix Makefiles" ../llvm</tt></li>
     <li><tt>make</tt></li>
     <li>This builds both LLVM and Clang for debug mode.</li>
     <li>Note: For subsequent Clang development, you can just run
         <tt>make clang</tt>.</li>
     <li>CMake allows you to generate project files for several IDEs: Xcode,
         Eclipse CDT4, CodeBlocks, Qt-Creator (use the CodeBlocks generator),
         KDevelop3. For more details see
         <a href="http://llvm.org/docs/CMake.html">Building LLVM with CMake</a>
         page.</li>
   </ul>
   </li>

   <li>If you intend to use Clang's C++ support, you may need to tell it how
       to find your C++ standard library headers. In general, Clang will detect
       the best version of libstdc++ headers available and use them - it will
       look both for system installations of libstdc++ as well as installations
       adjacent to Clang itself. If your configuration fits neither of these
       scenarios, you can use the <tt>-DGCC_INSTALL_PREFIX</tt> cmake option
       to tell Clang where the gcc containing the desired libstdc++ is installed.
   </li>
   <li>Try it out (assuming you add llvm/build/bin to your path):
   <ul>
     <li><tt>clang --help</tt></li>
     <li><tt>clang file.c -fsyntax-only</tt> (check for correctness)</li>
     <li><tt>clang file.c -S -emit-llvm -o -</tt> (print out unoptimized llvm code)</li>
     <li><tt>clang file.c -S -emit-llvm -o - -O3</tt></li>
     <li><tt>clang file.c -S -O3 -o -</tt> (output native machine code)</li>
   </ul>
   </li>
 </ol>

 <p>If you encounter problems while building Clang, make sure that your LLVM
 checkout is at the same revision as your Clang checkout. LLVM's interfaces
 change over time, and mismatched revisions are not expected to work
 together.</p>

 <h3>Simultaneously Building Clang and LLVM:</h3>

 <p>Once you have checked out Clang into the llvm source tree it will build along
 with the rest of <tt>llvm</tt>. To build all of LLVM and Clang together all at
 once simply run <tt>make</tt> from the root LLVM directory.</p>

 <p><em>Note:</em> Observe that Clang is technically part of a separate
 Subversion repository. As mentioned above, the latest Clang sources are tied to
 the latest sources in the LLVM tree. You can update your toplevel LLVM project
 and all (possibly unrelated) projects inside it with <tt><b>make
 update</b></tt>. This will run <tt>svn update</tt> on all subdirectories related
 to subversion. </p>

 <h3 id="buildWindows">Using Visual Studio</h3>

 <p>The following details setting up for and building Clang on Windows using
 Visual Studio:</p>

 <ol>
   <li>Get the required tools:
   <ul>
     <li><b>Subversion</b>.  Source code control program.  Get it from:
         <a href="http://subversion.apache.org/packages.html">
         http://subversion.apache.org/packages.html</a></li>
     <li><b>CMake</b>.  This is used for generating Visual Studio solution and
         project files.  Get it from:
         <a href="http://www.cmake.org/cmake/resources/software.html">
         http://www.cmake.org/cmake/resources/software.html</a></li>
     <li><b>Visual Studio 2013 or later</b></li>
     <li><b>Python</b>.  This is needed only if you will be running the tests
         (which is essential, if you will be developing for clang).
         Get it from:
         <a href="http://www.python.org/download/">
         http://www.python.org/download/</a></li>
     <li><b>GnuWin32 tools</b>
         These are also necessary for running the tests.
         (Note that the grep from MSYS or Cygwin doesn't work with the tests
         because of embedded double-quotes in the search strings.  The GNU
         grep does work in this case.)
         Get them from <a href="http://getgnuwin32.sourceforge.net/">
         http://getgnuwin32.sourceforge.net/</a>.</li>
   </ul>
   </li>

   <li>Check out LLVM:
   <ul>
     <li><tt>svn co http://llvm.org/svn/llvm-project/llvm/trunk llvm</tt></li>
   </ul>
   </li>
   <li>Check out Clang:
   <ul>
      <li><tt>cd llvm\tools</tt>
      <li><tt>svn co http://llvm.org/svn/llvm-project/cfe/trunk clang</tt></li>
   </ul>
   <p><em>Note</em>:  Some Clang tests are sensitive to the line endings.  Ensure
      that checking out the files does not convert LF line endings to CR+LF.
      If you use git-svn, make sure your <tt>core.autocrlf</tt> setting is false.</p>
   </li>
   <li>Run CMake to generate the Visual Studio solution and project files:
   <ul>
     <li><tt>cd ..\..</tt>  (back to where you started)</li>
     <li><tt>mkdir build</tt> (for building without polluting the source dir)</li>
     <li><tt>cd build</tt></li>
     <li>If you are using Visual Studio 2013:  <tt>cmake -G "Visual Studio 12" ..\llvm</tt></li>
     <li>See the <a href="http://www.llvm.org/docs/CMake.html">LLVM CMake guide</a> for
         more information on other configuration options for CMake.</li>
     <li>The above, if successful, will have created an LLVM.sln file in the
        <tt>build</tt> directory.
   </ul>
   </li>
   <li>Build Clang:
   <ul>
     <li>Open LLVM.sln in Visual Studio.</li>
     <li>Build the "clang" project for just the compiler driver and front end, or
       the "ALL_BUILD" project to build everything, including tools.</li>
   </ul>
   </li>
   <li>Try it out (assuming you added llvm/debug/bin to your path).  (See the
     running examples from above.)</li>
   <li>See <a href="hacking.html#testingWindows">
      Hacking on clang - Testing using Visual Studio on Windows</a> for information
      on running regression tests on Windows.</li>
 </ol>

 <p>Note that once you have checked out both llvm and clang, to synchronize
 to the latest code base, use the <tt>svn update</tt> command in both the
 llvm and llvm\tools\clang directories, as they are separate repositories.</p>

 <h2 id="driver">Clang Compiler Driver (Drop-in Substitute for GCC)</h2>

 <p>The <tt>clang</tt> tool is the compiler driver and front-end, which is
 designed to be a drop-in replacement for the <tt>gcc</tt> command.  Here are
 some examples of how to use the high-level driver:
 </p>

 <pre class="code">
 $ <b>cat t.c</b>
 #include &lt;stdio.h&gt;
 int main(int argc, char **argv) { printf("hello world\n"); }
 $ <b>clang t.c</b>
 $ <b>./a.out</b>
 hello world
 </pre>

 <p>The 'clang' driver is designed to work as closely to GCC as possible to
   maximize portability.  The only major difference between the two is that
   Clang defaults to gnu99 mode while GCC defaults to gnu89 mode.  If you see
   weird link-time errors relating to inline functions, try passing -std=gnu89
   to clang.</p>

 <h2>Examples of using Clang</h2>

 <!-- Thanks to
  http://shiflett.org/blog/2006/oct/formatting-and-highlighting-php-code-listings
 Site suggested using pre in CSS, but doesn't work in IE, so went for the <pre>
 tag. -->

 <pre class="code">
 $ <b>cat ~/t.c</b>
 typedef float V __attribute__((vector_size(16)));
 V foo(V a, V b) { return a+b*a; }
 </pre>


 <h3>Preprocessing:</h3>

 <pre class="code">
 $ <b>clang ~/t.c -E</b>
 # 1 "/Users/sabre/t.c" 1

 typedef float V __attribute__((vector_size(16)));

 V foo(V a, V b) { return a+b*a; }
 </pre>


 <h3>Type checking:</h3>

 <pre class="code">
 $ <b>clang -fsyntax-only ~/t.c</b>
 </pre>


 <h3>GCC options:</h3>

 <pre class="code">
 $ <b>clang -fsyntax-only ~/t.c -pedantic</b>
 /Users/sabre/t.c:2:17: <span style="color:magenta">warning:</span> extension used
 <span style="color:darkgreen">typedef float V __attribute__((vector_size(16)));</span>
 <span style="color:blue">                ^</span>
 1 diagnostic generated.
 </pre>


 <h3>Pretty printing from the AST:</h3>

 <p>Note, the <tt>-cc1</tt> argument indicates the compiler front-end, and
 not the driver, should be run. The compiler front-end has several additional
 Clang specific features which are not exposed through the GCC compatible driver
 interface.</p>

 <pre class="code">
 $ <b>clang -cc1 ~/t.c -ast-print</b>
 typedef float V __attribute__(( vector_size(16) ));
 V foo(V a, V b) {
    return a + b * a;
 }
 </pre>


 <h3>Code generation with LLVM:</h3>

 <pre class="code">
 $ <b>clang ~/t.c -S -emit-llvm -o -</b>
 define &lt;4 x float&gt; @foo(&lt;4 x float&gt; %a, &lt;4 x float&gt; %b) {
 entry:
          %mul = mul &lt;4 x float&gt; %b, %a
          %add = add &lt;4 x float&gt; %mul, %a
          ret &lt;4 x float&gt; %add
 }
 $ <b>clang -fomit-frame-pointer -O3 -S -o - t.c</b> <i># On x86_64</i>
 ...
 _foo:
 Leh_func_begin1:
 	mulps	%xmm0, %xmm1
 	addps	%xmm1, %xmm0
 	ret
 Leh_func_end1:
 </pre>

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	<META http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
	<title>Clang - Getting Started</title>
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	<link type="text/css" rel="stylesheet" href="content.css">
	</head>
	<body>

	<!--#include virtual="menu.html.incl"-->

	<div id="content">

	<h1>Getting Started: Building and Running Clang</h1>

	<p>This page gives you the shortest path to checking out Clang and demos a few
	options. This should get you up and running with the minimum of muss and fuss.
	If you like what you see, please consider <a href="get_involved.html">getting
	involved</a> with the Clang community. If you run into problems, please file
	bugs in <a href="http://llvm.org/bugs/">LLVM Bugzilla</a>.</p>

	<h2 id="download">Release Clang Versions</h2>

	<p>Clang is released as part of regular LLVM releases. You can download the release versions from <a href="http://llvm.org/releases/">http://llvm.org/releases/</a>.</p>
	<p>Clang is also provided in all major BSD or GNU/Linux distributions as part of their respective packaging systems. From Xcode 4.2, Clang is the default compiler for Mac OS X.</p>

	<h2 id="build">Building Clang and Working with the Code</h2>

	<h3 id="buildNix">On Unix-like Systems</h3>

	<p>If you would like to check out and build Clang, the current procedure is as
	follows:</p>

	<ol>
	<li>Get the required tools.
	<ul>
	<li>See
	<a href="http://llvm.org/docs/GettingStarted.html#requirements">
	Getting Started with the LLVM System - Requirements</a>.</li>
	<li>Note also that Python is needed for running the test suite.
	Get it at: <a href="http://www.python.org/download">
	http://www.python.org/download</a></li>
	<li>Standard build process uses CMake. Get it at:
	<a href="http://www.cmake.org/download">
	http://www.cmake.org/download</a></li>
	</ul>

	<li>Check out LLVM:
	<ul>
	<li>Change directory to where you want the llvm directory placed.</li>
	<li><tt>svn co http://llvm.org/svn/llvm-project/llvm/trunk llvm</tt></li>
	</ul>
	</li>
	<li>Check out Clang:
	<ul>
	<li><tt>cd llvm/tools</tt></li>
	<li><tt>svn co http://llvm.org/svn/llvm-project/cfe/trunk clang</tt></li>
	<li><tt>cd ../..</tt></li>
	</ul>
	</li>
	<li>Check out extra Clang tools: (optional)
	<ul>
	<li><tt>cd llvm/tools/clang/tools</tt></li>
	<li><tt>svn co http://llvm.org/svn/llvm-project/clang-tools-extra/trunk
	extra</tt></li>
	<li><tt>cd ../../../..</tt></li>
	</ul>
	</li>
	<li>Check out Compiler-RT (optional):
	<ul>
	<li><tt>cd llvm/projects</tt></li>
	<li><tt>svn co http://llvm.org/svn/llvm-project/compiler-rt/trunk
	compiler-rt</tt></li>
	<li><tt>cd ../..</tt></li>
	</ul>
	</li>
	<li>Check out libcxx: (only required to build and run Compiler-RT tests on OS X, optional otherwise)
	<ul>
	<li><tt>cd llvm/projects</tt></li>
	<li><tt>svn co http://llvm.org/svn/llvm-project/libcxx/trunk
	libcxx</tt></li>
	<li><tt>cd ../..</tt></li>
	</ul>
	</li>
	<li>Build LLVM and Clang:
	<ul>
	<li><tt>mkdir build</tt> (in-tree build is not supported)</li>
	<li><tt>cd build</tt></li>
	<li><tt>cmake -G "Unix Makefiles" ../llvm</tt></li>
	<li><tt>make</tt></li>
	<li>This builds both LLVM and Clang for debug mode.</li>
	<li>Note: For subsequent Clang development, you can just run
	<tt>make clang</tt>.</li>
	<li>CMake allows you to generate project files for several IDEs: Xcode,
	Eclipse CDT4, CodeBlocks, Qt-Creator (use the CodeBlocks generator),
	KDevelop3. For more details see
	<a href="http://llvm.org/docs/CMake.html">Building LLVM with CMake</a>
	page.</li>
	</ul>
	</li>

	<li>If you intend to use Clang's C++ support, you may need to tell it how
	to find your C++ standard library headers. In general, Clang will detect
	the best version of libstdc++ headers available and use them - it will
	look both for system installations of libstdc++ as well as installations
	adjacent to Clang itself. If your configuration fits neither of these
	scenarios, you can use the <tt>-DGCC_INSTALL_PREFIX</tt> cmake option
	to tell Clang where the gcc containing the desired libstdc++ is installed.
	</li>
	<li>Try it out (assuming you add llvm/build/bin to your path):
	<ul>
	<li><tt>clang --help</tt></li>
	<li><tt>clang file.c -fsyntax-only</tt> (check for correctness)</li>
	<li><tt>clang file.c -S -emit-llvm -o -</tt> (print out unoptimized llvm code)</li>
	<li><tt>clang file.c -S -emit-llvm -o - -O3</tt></li>
	<li><tt>clang file.c -S -O3 -o -</tt> (output native machine code)</li>
	</ul>
	</li>
	</ol>

	<p>If you encounter problems while building Clang, make sure that your LLVM
	checkout is at the same revision as your Clang checkout. LLVM's interfaces
	change over time, and mismatched revisions are not expected to work
	together.</p>

	<h3>Simultaneously Building Clang and LLVM:</h3>

	<p>Once you have checked out Clang into the llvm source tree it will build along
	with the rest of <tt>llvm</tt>. To build all of LLVM and Clang together all at
	once simply run <tt>make</tt> from the root LLVM directory.</p>

	<p><em>Note:</em> Observe that Clang is technically part of a separate
	Subversion repository. As mentioned above, the latest Clang sources are tied to
	the latest sources in the LLVM tree. You can update your toplevel LLVM project
	and all (possibly unrelated) projects inside it with <tt><b>make
	update</b></tt>. This will run <tt>svn update</tt> on all subdirectories related
	to subversion. </p>

	<h3 id="buildWindows">Using Visual Studio</h3>

	<p>The following details setting up for and building Clang on Windows using
	Visual Studio:</p>

	<ol>
	<li>Get the required tools:
	<ul>
	<li><b>Subversion</b>. Source code control program. Get it from:
	<a href="http://subversion.apache.org/packages.html">
	http://subversion.apache.org/packages.html</a></li>
	<li><b>CMake</b>. This is used for generating Visual Studio solution and
	project files. Get it from:
	<a href="http://www.cmake.org/cmake/resources/software.html">
	http://www.cmake.org/cmake/resources/software.html</a></li>
	<li><b>Visual Studio 2013 or later</b></li>
	<li><b>Python</b>. This is needed only if you will be running the tests
	(which is essential, if you will be developing for clang).
	Get it from:
	<a href="http://www.python.org/download/">
	http://www.python.org/download/</a></li>
	<li><b>GnuWin32 tools</b>
	These are also necessary for running the tests.
	(Note that the grep from MSYS or Cygwin doesn't work with the tests
	because of embedded double-quotes in the search strings. The GNU
	grep does work in this case.)
	Get them from <a href="http://getgnuwin32.sourceforge.net/">
	http://getgnuwin32.sourceforge.net/</a>.</li>
	</ul>
	</li>

	<li>Check out LLVM:
	<ul>
	<li><tt>svn co http://llvm.org/svn/llvm-project/llvm/trunk llvm</tt></li>
	</ul>
	</li>
	<li>Check out Clang:
	<ul>
	<li><tt>cd llvm\tools</tt>
	<li><tt>svn co http://llvm.org/svn/llvm-project/cfe/trunk clang</tt></li>
	</ul>
	<p><em>Note</em>: Some Clang tests are sensitive to the line endings. Ensure
	that checking out the files does not convert LF line endings to CR+LF.
	If you use git-svn, make sure your <tt>core.autocrlf</tt> setting is false.</p>
	</li>
	<li>Run CMake to generate the Visual Studio solution and project files:
	<ul>
	<li><tt>cd ..\..</tt> (back to where you started)</li>
	<li><tt>mkdir build</tt> (for building without polluting the source dir)</li>
	<li><tt>cd build</tt></li>
	<li>If you are using Visual Studio 2013: <tt>cmake -G "Visual Studio 12" ..\llvm</tt></li>
	<li>See the <a href="http://www.llvm.org/docs/CMake.html">LLVM CMake guide</a> for
	more information on other configuration options for CMake.</li>
	<li>The above, if successful, will have created an LLVM.sln file in the
	<tt>build</tt> directory.
	</ul>
	</li>
	<li>Build Clang:
	<ul>
	<li>Open LLVM.sln in Visual Studio.</li>
	<li>Build the "clang" project for just the compiler driver and front end, or
	the "ALL_BUILD" project to build everything, including tools.</li>
	</ul>
	</li>
	<li>Try it out (assuming you added llvm/debug/bin to your path). (See the
	running examples from above.)</li>
	<li>See <a href="hacking.html#testingWindows">
	Hacking on clang - Testing using Visual Studio on Windows</a> for information
	on running regression tests on Windows.</li>
	</ol>

	<p>Note that once you have checked out both llvm and clang, to synchronize
	to the latest code base, use the <tt>svn update</tt> command in both the
	llvm and llvm\tools\clang directories, as they are separate repositories.</p>

	<h2 id="driver">Clang Compiler Driver (Drop-in Substitute for GCC)</h2>

	<p>The <tt>clang</tt> tool is the compiler driver and front-end, which is
	designed to be a drop-in replacement for the <tt>gcc</tt> command. Here are
	some examples of how to use the high-level driver:
	</p>

	<pre class="code">
	$ <b>cat t.c</b>
	#include <stdio.h>
	int main(int argc, char **argv) { printf("hello world\n"); }
	$ <b>clang t.c</b>
	$ <b>./a.out</b>
	hello world
	</pre>

	<p>The 'clang' driver is designed to work as closely to GCC as possible to
	maximize portability. The only major difference between the two is that
	Clang defaults to gnu99 mode while GCC defaults to gnu89 mode. If you see
	weird link-time errors relating to inline functions, try passing -std=gnu89
	to clang.</p>

	<h2>Examples of using Clang</h2>

	<!-- Thanks to
	http://shiflett.org/blog/2006/oct/formatting-and-highlighting-php-code-listings
	Site suggested using pre in CSS, but doesn't work in IE, so went for the <pre>
	tag. -->

	<pre class="code">
	$ <b>cat ~/t.c</b>
	typedef float V __attribute__((vector_size(16)));
	V foo(V a, V b) { return a+b*a; }
	</pre>


	<h3>Preprocessing:</h3>

	<pre class="code">
	$ <b>clang ~/t.c -E</b>
	# 1 "/Users/sabre/t.c" 1

	typedef float V __attribute__((vector_size(16)));

	V foo(V a, V b) { return a+b*a; }
	</pre>


	<h3>Type checking:</h3>

	<pre class="code">
	$ <b>clang -fsyntax-only ~/t.c</b>
	</pre>


	<h3>GCC options:</h3>

	<pre class="code">
	$ <b>clang -fsyntax-only ~/t.c -pedantic</b>
	/Users/sabre/t.c:2:17: <span style="color:magenta">warning:</span> extension used
	<span style="color:darkgreen">typedef float V __attribute__((vector_size(16)));</span>
	<span style="color:blue"> ^</span>
	1 diagnostic generated.
	</pre>


	<h3>Pretty printing from the AST:</h3>

	<p>Note, the <tt>-cc1</tt> argument indicates the compiler front-end, and
	not the driver, should be run. The compiler front-end has several additional
	Clang specific features which are not exposed through the GCC compatible driver
	interface.</p>

	<pre class="code">
	$ <b>clang -cc1 ~/t.c -ast-print</b>
	typedef float V __attribute__(( vector_size(16) ));
	V foo(V a, V b) {
	return a + b * a;
	}
	</pre>


	<h3>Code generation with LLVM:</h3>

	<pre class="code">
	$ <b>clang ~/t.c -S -emit-llvm -o -</b>
	define <4 x float> @foo(<4 x float> %a, <4 x float> %b) {
	entry:
	%mul = mul <4 x float> %b, %a
	%add = add <4 x float> %mul, %a
	ret <4 x float> %add
	}
	$ <b>clang -fomit-frame-pointer -O3 -S -o - t.c</b> <i># On x86_64</i>
	...
	_foo:
	Leh_func_begin1:
	mulps %xmm0, %xmm1
	addps %xmm1, %xmm0
	ret
	Leh_func_end1:
	</pre>

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