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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"
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<html>
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<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
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<link rel="stylesheet" href="llvm.css" type="text/css" media="screen">
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<title>Bootstrapping the LLVM C/C++ Front-End</title>
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</head>
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<body>
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<div class="doc_title">
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Bootstrapping the LLVM C/C++ Front-End
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</div>
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<ol>
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<li><a href="#cautionarynote">A Cautionary Note</a>
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<ul>
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<li><a href="#cygwin">Building under Cygwin</a></li>
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<li><a href="#aix">Building under AIX</a></li>
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</ul>
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</li>
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<li><a href="#instructions">llvm-gcc4 Instructions</a></li>
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<li><a href="#llvm-gcc3-instructions">llvm-gcc3 Instructions</a></li>
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<li><a href="#license">License Information</a></li>
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</ol>
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<div class="doc_author">
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<p>Written by Brian R. Gaeke and
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<a href="http://nondot.org/sabre">Chris Lattner</a></p>
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</div>
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<!-- *********************************************************************** -->
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<div class="doc_section">
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<a name="cautionarynote">A Cautionary Note</a>
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</div>
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<!-- *********************************************************************** -->
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<div class="doc_text">
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<p>This document is intended to explain the process of building the
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LLVM C/C++ front-end from its source code. You have to do this, for example, if
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you are porting LLVM to a new architecture or operating system, if you are
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working from Top-Of-Tree CVS/SVN, or if there is no precompiled snapshot
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available.</p>
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<p><b>NOTE:</b> This is currently a somewhat fragile, error-prone
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process, and you should <b>only</b> try to do it if:</p>
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<ol>
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<li>you really, really, really can't use the binaries we distribute</li>
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<li>you are an elite GCC hacker.</li>
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<li>you want to use the latest bits from CVS.</li>
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</ol>
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<p>We welcome patches to help make this process simpler.</p>
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</div>
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<!--=========================================================================-->
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<div class="doc_subsection">
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<a name="cygwin">Building under Cygwin</a>
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</div>
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<!--=========================================================================-->
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<div class="doc_text">
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<p>If you are building LLVM and the GCC front-end under Cygwin, please note that
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the LLVM and GCC makefiles do not correctly handle spaces in paths. To deal
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with this issue, make sure that your LLVM and GCC source and build trees are
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located in a top-level directory (like <tt>/cygdrive/c/llvm</tt> and
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<tt>/cygdrive/c/llvm-cfrontend</tt>), not in a directory that contains a space
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(which includes your "home directory", because it lives under the "Documents
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and Settings" directory). We welcome patches to fix this issue.
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</p>
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<p>It has been found that the GCC 3.3.3 compiler provided with recent Cygwin
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versions is incapable of compiling the LLVM GCC front-end correctly. If your
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Cygwin
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installation includes GCC 3.3.3, we <i>strongly</i> recommend that you download
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GCC 3.4.3, build it separately, and use it for compiling the LLVM GCC front-end.
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This has been
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shown to work correctly.</p>
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<p>Some versions of Cygwin utilize an experimental version of GNU binutils that
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will cause the GNU <tt>ld</tt> linker to fail an assertion when linking
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components of the libstdc++. It is recommended that you replace the entire
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binutils package with version 2.15 such that "<tt>ld --version</tt>" responds
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with</p>
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<pre>GNU ld version 2.15</pre>
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not with:<br/>
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<pre>GNU ld version 2.15.91 20040725</pre>
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</div>
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<!--=========================================================================-->
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<div class="doc_subsection"><a name="aix">Building under AIX</a></div>
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<div class="doc_text">
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<p>If you are building LLVM and the GCC front-end under AIX, do NOT use GNU
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Binutils. They are not stable under AIX and may produce incorrect and/or
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invalid code. Instead, use the system assembler and linker.
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</p>
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</div>
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<!-- *********************************************************************** -->
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<div class="doc_section">
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<a name="instructions">llvm-gcc4 Instructions</a>
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</div>
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<!-- *********************************************************************** -->
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<div class="doc_text">
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<p>This section describes how to aquire and build llvm-gcc4, which is based on
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the GCC 4.0.1 front-end. This front-end supports C, C++, Objective-C, and
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Objective-C++. Note that the instructions for building this front-end are
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completely different than those for building llvm-gcc3.
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</p>
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<ol>
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<li>
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<p>Retrieve the appropriate llvm-gcc4-x.y.source.tar.gz archive from the llvm
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web site.</p>
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<p>It is also possible to download the sources of the llvm-gcc4 front end from
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a read-only mirror using subversion. To check out the code the first time use:
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</p>
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<tt>svn co svn://anonsvn.opensource.apple.com/svn/llvm/trunk
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<i>dst-directory</i></tt>
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<p>After that, the code can be be updated in the destination directory using;
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</p>
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<tt>svn update</tt>
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<p>The mirror is brought up to date every evening.</p>
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</li>
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<li>Follow the directions in the top-level README.LLVM file for up-to-date
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instructions on how to build llvm-gcc4.</li>
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</ol>
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</div>
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<!-- *********************************************************************** -->
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<div class="doc_section">
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<a name="llvm-gcc3-instructions">llvm-gcc3 Instructions</a>
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</div>
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<!-- *********************************************************************** -->
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<div class="doc_text">
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<ol>
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<li>Aquire llvm-gcc3 from <a href="GettingStarted.html#checkout">LLVM CVS</a> or
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from a <a href="http://llvm.org/releases/">release tarball</a>.</li>
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<li><p>Configure and build the LLVM libraries and tools. There are two ways to
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do this: either with <i>objdir</i> == <i>srcdir</i> or
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<i>objdir</i> != <i>srcdir</i>. It is recommended
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that <i>srcdir</i> be the same as <i>objdir</i> for your LLVM tree (but note
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that you should always use <i>srcdir</i> != <i>objdir</i> for llvm-gcc):</p>
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<ul>
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<li>With <i>objdir</i> != <i>srcdir</i>:<pre>
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% cd <i>objdir</i>
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% <i>srcdir</i>/configure --prefix=/some/path/you/can/install/to [options...]
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% gmake tools-only
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</pre></li>
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<li>With <i>objdir</i> == <i>srcdir</i>:<pre>
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% cd llvm
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% ./configure --prefix=/some/path/you/can/install/to [options...]
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% gmake tools-only
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</pre></li>
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</ul>
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<p>This will build all of the LLVM tools and libraries. The <tt>--prefix</tt>
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option defaults to /usr/local (per configure standards) but unless you are a
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system administrator, you probably won't be able to install LLVM there because
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of permissions. Specify a path into which LLVM can be installed (e.g.
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<tt>--prefix=/home/user/llvm</tt>).</p>
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</li>
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<li><p>Add the directory containing the tools to your PATH.</p>
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<pre>
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% set path = ( `cd llvm/Debug/bin && pwd` $path )
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</pre></li>
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<li><p>Unpack the C/C++ front-end source into cfrontend/src, either by
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untar'ing a cfrontend.source.tar.gz file or checking out CVS into this
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directory.</p></li>
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<li><p>Make "build" and "install" directories as siblings of the "src" tree:</p>
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<pre>
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% pwd
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/usr/local/example/cfrontend/src
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% cd ..
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% mkdir build install
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% set CFEINSTALL = `pwd`/install
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</pre></li>
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<li><p>Configure, build, and install the GCC front-end:</p>
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<p>
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<b>Linux/x86:</b><br>
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<b>Linux/IA-64:</b><br>
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<b>MacOS X/PowerPC</b> (requires dlcompat library):<br>
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<b>AIX/PowerPC:</b>
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</p>
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<pre>
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% cd build
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% ../src/configure --prefix=$CFEINSTALL --disable-threads --disable-nls \
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--disable-shared --enable-languages=c,c++ --program-prefix=llvm-
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% gmake all; gmake install
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</pre>
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<p><b>Cygwin/x86:</b></p>
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<pre>
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% cd build
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% ../src/configure --prefix=$CFEINSTALL --disable-threads --disable-nls \
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--disable-shared --enable-languages=c,c++ --disable-c-mbchar \
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--program-prefix=llvm-
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% gmake all; gmake install
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</pre>
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<p><b>Solaris/SPARC:</b></p>
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<p>
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The GCC front-end can be configured for either SPARC V8 (32 bit) or SPARC V9 (64
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bit). This changes, among other things, the sizes of integer types and the
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macros defined for conditional compilation.
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</p>
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<p>
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The SPARC V8 ABI support is more robust than the V9 ABI support and can generate
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SPARC V9 code. It is highly recommended that you use the V8 ABI with LLVM, as
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shown below. Also,
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note that Solaris has trouble with various wide (multibyte) character
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functions from C as referenced from C++, so we typically configure with
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--disable-c-mbchar (cf. <a href="http://llvm.org/PR206">Bug 206</a>).
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</p>
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<pre>
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% cd build
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% ../src/configure --prefix=$CFEINSTALL --disable-threads --disable-nls \
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--disable-shared --enable-languages=c,c++ --host=sparc-sun-solaris2.8 \
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--disable-c-mbchar --program-prefix=llvm-
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% gmake all; gmake install
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</pre>
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<p><b>Common Problem:</b> You may get error messages regarding the fact
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that LLVM does not support inline assembly. Here are two common
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fixes:</p>
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<ul>
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<li><p><b>Fix 1:</b> If you have system header files that include
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inline assembly, you may have to modify them to remove the inline
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assembly and install the modified versions in
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<code>$CFEINSTALL/lib/gcc/<i>target-triplet</i>/3.4-llvm/include</code>.</li>
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<li><b>Fix 2:</b> If you are building the C++ front-end on a CPU we
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haven't tried yet, you will probably have to edit the appropriate
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version of atomicity.h under
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<code>src/libstdc++-v3/config/cpu/<i>name-of-cpu</i>/atomicity.h</code>
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and apply a patch so that it does not use inline assembly.</li>
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</ul>
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<p><b>Porting to a new architecture:</b> If you are porting the front-end
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to a new architecture or compiling in a configuration that we have
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not tried previously, there are probably several changes you will have to make
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to the GCC target to get it to work correctly. These include:<p>
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<ul>
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<li>Often targets include special assembler or linker flags which
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<tt>gccas</tt>/<tt>gccld</tt> does not understand. In general, these can
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just be removed.</li>
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<li>LLVM currently does not support any floating point values other than
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32-bit and 64-bit IEEE floating point. The primary effect of this is
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that you may have to map "long double" onto "double".</li>
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<li>The profiling hooks in GCC do not apply at all to the LLVM front-end.
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These may need to be disabled.</li>
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<li>No inline assembly for position independent code. At the LLVM level,
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everything is position independent.</li>
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<li>We handle <tt>.init</tt> and <tt>.fini</tt> differently.</li>
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<li>You may have to disable multilib support in your target. Using multilib
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support causes the GCC compiler driver to add a lot of "<tt>-L</tt>"
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options to the link line, which do not relate to LLVM and confuse
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<tt>gccld</tt>. To disable multilibs, delete any
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<tt>MULTILIB_OPTIONS</tt> lines from your target files.</li>
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<li>Did we mention that we don't support inline assembly? You'll probably
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have to add some fixinclude hacks to disable it in the system
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headers.</li>
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</ul>
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</li>
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<li><p>Put <tt>$CFEINSTALL/bin</tt> into your <tt>PATH</tt> environment
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variable.</p>
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<ul>
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<li>sh: <tt>export PATH=$CFEINSTALL/bin:$PATH</tt></li>
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<li>csh: <tt>setenv PATH $CFEINSTALL/bin:$PATH</tt></li>
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</ul>
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</li>
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<li><p>Go back into the LLVM source tree proper. Rerun configure, using
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the same options as the last time. This will cause the configuration to now find
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the newly built llvm-gcc and llvm-g++ executables. </p></li>
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<li><p>Rebuild your CVS tree. This shouldn't cause the whole thing to be
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rebuilt, but it should build the runtime libraries. After the tree is
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built, install the runtime libraries into your GCC front-end build tree.
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These are the commands you need:</p>
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<pre>
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% gmake
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% gmake -C runtime install-bytecode
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</pre></li>
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<li><p>Optionally, build a symbol table for the newly installed runtime
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libraries. Although this step is optional, you are strongly encouraged to
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do this as the symbol tables will make a significant difference in your
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link times. Use the <tt>llvm-ranlib</tt> tool to do this, as follows:</p>
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<pre>
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% cd $CFEINSTALL/lib
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% llvm-ranlib libiberty.a
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% llvm-ranlib libstdc++.a
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% llvm-ranlib libsupc++.a
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% cd $CFEINSTALL/lib/gcc/<i>target-triplet</i>/3.4-llvm
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% llvm-ranlib libgcc.a
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% llvm-ranlib libgcov.a
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</pre>
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<li><p>Test the newly-installed C frontend by one or more of the
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following means:</p>
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<ul>
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<li> running the feature & regression tests via <tt>make check</tt></li>
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<li> compiling and running a "hello, LLVM" program in C and C++.</li>
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<li> running the tests found in the <tt>llvm-test</tt> CVS module</li>
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</ul></li>
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</ol>
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</div>
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<!-- *********************************************************************** -->
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<div class="doc_section">
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<a name="license">License Information</a>
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</div>
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<div class="doc_text">
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<p>
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The LLVM GCC frontend is licensed to you under the GNU General Public License
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and the GNU Lesser General Public License. Please see the files COPYING and
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COPYING.LIB for more details.
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</p>
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<p>
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More information is <a href="FAQ.html#license">available in the FAQ</a>.
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</p>
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</pre>
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</div>
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<!-- *********************************************************************** -->
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<hr>
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<address>
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src="http://jigsaw.w3.org/css-validator/images/vcss" alt="Valid CSS!"></a>
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Brian Gaeke<br>
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<a href="http://llvm.org">LLVM Compiler Infrastructure</a><br>
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Last modified: $Date$
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</address>
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