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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"
"http://www.w3.org/TR/html4/strict.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<link rel="stylesheet" href="llvm.css" type="text/css" media="screen">
<title>Bootstrapping the LLVM C/C++ Front-End</title>
</head>
<body>
<div class="doc_title">
Bootstrapping the LLVM C/C++ Front-End
</div>
<ol>
<li><a href="#cautionarynote">A Cautionary Note</a>
<ul>
<li><a href="#cygwin">Building under Cygwin</a></li>
<li><a href="#aix">Building under AIX</a></li>
</ul>
</li>
<li><a href="#instructions">llvm-gcc4 Instructions</a></li>
<li><a href="#llvm-gcc3-instructions">llvm-gcc3 Instructions</a></li>
<li><a href="#license">License Information</a></li>
</ol>
<div class="doc_author">
<p>Written by Brian R. Gaeke and
<a href="http://nondot.org/sabre">Chris Lattner</a></p>
</div>
<!-- *********************************************************************** -->
<div class="doc_section">
<a name="cautionarynote">A Cautionary Note</a>
</div>
<!-- *********************************************************************** -->
<div class="doc_text">
<p>This document is intended to explain the process of building the LLVM C/C++
front-end from its source code. You have to do this, for example, if you are
porting LLVM to a new architecture or operating system, if you are working from
Top-Of-Tree CVS/SVN, or if there is no precompiled snapshot available.</p>
<p><b>NOTE:</b> This is currently a somewhat fragile, error-prone process, and
you should <b>only</b> try to do it if:</p>
<ol>
<li>you really, <em>really</em>, <b><em>really</em></b> can't use the
binaries we distribute</li>
<li>you are an elite GCC hacker.</li>
<li>you want to use the latest bits from CVS.</li>
</ol>
<p>We welcome patches to help make this process simpler.</p>
</div>
<!--=========================================================================-->
<div class="doc_subsection">
<a name="cygwin">Building under Cygwin</a>
</div>
<!--=========================================================================-->
<div class="doc_text">
<p>If you are building LLVM and the GCC front-end under Cygwin, please note that
the LLVM and GCC makefiles do not correctly handle spaces in paths. To deal
with this issue, make sure that your LLVM and GCC source and build trees are
located in a top-level directory (like <tt>/cygdrive/c/llvm</tt> and
<tt>/cygdrive/c/llvm-cfrontend</tt>), not in a directory that contains a space
(which includes your "home directory", because it lives under the "Documents and
Settings" directory). We welcome patches to fix this issue.</p>
<p>It has been found that the GCC 3.3.3 compiler provided with recent Cygwin
versions is incapable of compiling the LLVM GCC front-end correctly. If your
Cygwin installation includes GCC 3.3.3, we <em>strongly</em> recommend that you
download GCC 3.4.3, build it separately, and use it for compiling the LLVM GCC
front-end. This has been shown to work correctly.</p>
<p>Some versions of Cygwin utilize an experimental version of GNU binutils that
will cause the GNU <tt>ld</tt> linker to fail an assertion when linking
components of the libstdc++. It is recommended that you replace the entire
binutils package with version 2.15 such that "<tt>ld --version</tt>" responds
with</p>
<div class="doc_code">
<pre>GNU ld version 2.15</pre>
</div>
<p>not with:</p>
<div class="doc_code">
<pre>GNU ld version 2.15.91 20040725</pre>
</div>
</div>
<!--=========================================================================-->
<div class="doc_subsection"><a name="aix">Building under AIX</a></div>
<div class="doc_text">
<p>If you are building LLVM and the GCC front-end under AIX, do NOT use GNU
Binutils. They are not stable under AIX and may produce incorrect and/or
invalid code. Instead, use the system assembler and linker.</p>
</div>
<!-- *********************************************************************** -->
<div class="doc_section">
<a name="instructions">llvm-gcc4 Instructions</a>
</div>
<!-- *********************************************************************** -->
<div class="doc_text">
<p>This section describes how to aquire and build llvm-gcc4, which is based on
the GCC 4.0.1 front-end. This front-end supports C, C++, Objective-C, and
Objective-C++. Note that the instructions for building this front-end are
completely different than those for building llvm-gcc3.</p>
<ol>
<li><p>Retrieve the appropriate llvm-gcc4-x.y.source.tar.gz archive from the
llvm web site.</p>
<p>It is also possible to download the sources of the llvm-gcc4 front end
from a read-only mirror using subversion. To check out the code the
first time use:</p>
<div class="doc_code">
<pre>
svn co svn://anonsvn.opensource.apple.com/svn/llvm/trunk <i>dst-directory</i>
</pre>
</div>
<p>After that, the code can be be updated in the destination directory
using:</p>
<div class="doc_code">
<pre>svn update</pre>
</div>
<p>The mirror is brought up to date every evening.</p></li>
<li>Follow the directions in the top-level <tt>README.LLVM</tt> file for
up-to-date instructions on how to build llvm-gcc4.</li>
</ol>
</div>
<!-- *********************************************************************** -->
<div class="doc_section">
<a name="llvm-gcc3-instructions">llvm-gcc3 Instructions</a>
</div>
<!-- *********************************************************************** -->
<div class="doc_text">
<ol>
<li>Aquire llvm-gcc3 from <a href="GettingStarted.html#checkout">LLVM CVS</a>
or from a <a href="http://llvm.org/releases/">release tarball</a>.</li>
<li><p>Configure and build the LLVM libraries and tools. There are two ways to
do this: either with <tt><i>objdir</i> == <i>srcdir</i></tt> or
<tt><i>objdir</i> != <i>srcdir</i></tt>. It is recommended that
<tt><i>srcdir</i></tt> be the same as <tt><i>objdir</i></tt> for your
LLVM tree (but note that you should always use <tt><i>srcdir</i> !=
<i>objdir</i></tt> for llvm-gcc):</p>
<ul>
<li><p>With <tt><i>objdir</i> != <i>srcdir</i></tt>:</p>
<div class="doc_code">
<pre>
% cd <i>objdir</i>
% <i>srcdir</i>/configure --prefix=/some/path/you/can/install/to [options...]
% gmake tools-only
</pre>
</div>
</li>
<li><p>With <tt><i>objdir</i> == <i>srcdir</i></tt>:</p>
<div class="doc_code">
<pre>
% cd llvm
% ./configure --prefix=/some/path/you/can/install/to [options...]
% gmake tools-only
</pre>
</div>
</li>
</ul>
<p>This will build all of the LLVM tools and libraries. The
<tt>--prefix</tt> option defaults to <tt>/usr/local</tt> (per configure
standards) but unless you are a system administrator, you probably
won't be able to install LLVM there because of permissions. Specify a
path into which LLVM can be installed
(e.g. <tt>--prefix=/home/user/llvm</tt>).</p></li>
<li><p>Add the directory containing the tools to your PATH.</p>
<div class="doc_code">
csh:
<pre>
% set path = ( `cd llvm/Debug/bin && pwd` $path )
</pre>
sh:
<pre>
% export PATH=`cd llvm/Debug/bin && pwd`:$PATH
</pre>
</div>
</li>
<li><p>Unpack the C/C++ front-end source, either by
untar'ing/unzipping a tar.gz file or checking out CVS into this
directory.</p></li>
<li><p>Make "build" and "install" directories as siblings of the "src"
tree:</p>
<div class="doc_code">
csh:
<pre>
% pwd
/usr/local/example/llvm-gcc3.4/src
% cd ..
% mkdir build install
% set CFEINSTALL = `pwd`/install
</pre>
sh:
<pre>
% pwd
/usr/local/example/llvm-gcc3.4/src
% cd ..
% mkdir build install
% export CFEINSTALL=`pwd`/install
</pre>
</div>
</li>
<li><p>Configure, build, and install the GCC front-end:</p>
<p>
<b>Linux/x86:</b><br>
<b>Linux/IA-64:</b><br>
<b>MacOS X/PowerPC</b> (requires dlcompat library):<br>
<b>AIX/PowerPC:</b>
</p>
<div class="doc_code">
<pre>
% cd build
% ../src/configure --prefix=$CFEINSTALL --disable-threads --disable-nls \
--disable-shared --enable-languages=c,c++ --program-prefix=llvm-
% gmake all; gmake install
</pre>
</div>
<p><b>Cygwin/x86:</b></p>
<div class="doc_code">
<pre>
% cd build
% ../src/configure --prefix=$CFEINSTALL --disable-threads --disable-nls \
--disable-shared --enable-languages=c,c++ --disable-c-mbchar \
--program-prefix=llvm-
% gmake all; gmake install
</pre>
</div>
<p><b>Solaris/SPARC:</b></p>
<p>The GCC front-end can be configured for either SPARC V8 (32 bit) or
SPARC V9 (64 bit). This changes, among other things, the sizes of
integer types and the macros defined for conditional compilation.</p>
<p>The SPARC V8 ABI support is more robust than the V9 ABI support and can
generate SPARC V9 code. It is highly recommended that you use the V8
ABI with LLVM, as shown below. Also, note that Solaris has trouble
with various wide (multibyte) character functions from C as referenced
from C++, so we typically configure with --disable-c-mbchar (cf. <a
href="http://llvm.org/PR206">Bug 206</a>).</p>
<div class="doc_code">
<pre>
% cd build
% ../src/configure --prefix=$CFEINSTALL --disable-threads --disable-nls \
--disable-shared --enable-languages=c,c++ --host=sparc-sun-solaris2.8 \
--disable-c-mbchar --program-prefix=llvm-
% gmake all; gmake install
</pre>
</div>
<p><b>Common Problem:</b> You may get error messages regarding the fact
that LLVM does not support inline assembly. Here are two common
fixes:</p>
<ul>
<li><p><b>Fix 1:</b> If you have system header files that include inline
assembly, you may have to modify them to remove the inline assembly
and install the modified versions in
<code>$CFEINSTALL/lib/gcc/<i>target-triplet</i>/3.4-llvm/include</code>.</li>
<li><b>Fix 2:</b> If you are building the C++ front-end on a CPU we
haven't tried yet, you will probably have to edit the appropriate
version of atomicity.h under
<code>src/libstdc++-v3/config/cpu/<i>name-of-cpu</i>/atomicity.h</code>
and apply a patch so that it does not use inline assembly.</li>
</ul>
<p><b>Porting to a new architecture:</b> If you are porting the front-end
to a new architecture or compiling in a configuration that we have not
tried previously, there are probably several changes you will have to
make to the GCC target to get it to work correctly. These include:</p>
<ul>
<li>Often targets include special assembler or linker flags which
<tt>gccas</tt>/<tt>gccld</tt> does not understand. In general,
these can just be removed.</li>
<li>LLVM currently does not support any floating point values other than
32-bit and 64-bit IEEE floating point. The primary effect of this
is that you may have to map "long double" onto "double".</li>
<li>The profiling hooks in GCC do not apply at all to the LLVM
front-end. These may need to be disabled.</li>
<li>No inline assembly for position independent code. At the LLVM
level, everything is position independent.</li>
<li>We handle <tt>.init</tt> and <tt>.fini</tt> differently.</li>
<li>You may have to disable multilib support in your target. Using
multilib support causes the GCC compiler driver to add a lot of
"<tt>-L</tt>" options to the link line, which do not relate to LLVM
and confuse <tt>gccld</tt>. To disable multilibs, delete any
<tt>MULTILIB_OPTIONS</tt> lines from your target files.</li>
<li>Did we mention that we don't support inline assembly? You'll
probably have to add some fixinclude hacks to disable it in the
system headers.</li>
</ul></li>
<li><p>Put <tt>$CFEINSTALL/bin</tt> into your <tt>PATH</tt> environment
variable.</p>
<div class="doc_code">
csh:
<pre>
% setenv PATH $CFEINSTALL/bin:$PATH
</pre>
sh:
<pre>
% export PATH=$CFEINSTALL/bin:$PATH
</pre>
</div>
</li>
<li><p>Go back into the LLVM source tree proper. Rerun configure, using the
same options as the last time. This will cause the configuration to now
find the newly built llvm-gcc and llvm-g++ executables. </p></li>
<li><p>Rebuild your CVS tree. This shouldn't cause the whole thing to be
rebuilt, but it should build the runtime libraries. After the tree is
built, install the runtime libraries into your GCC front-end build tree.
These are the commands you need:</p>
<div class="doc_code">
<pre>
% gmake
% gmake -C runtime install-bytecode
</pre>
</div>
</li>
<li><p>Optionally, build a symbol table for the newly installed runtime
libraries. Although this step is optional, you are strongly encouraged to
do this as the symbol tables will make a significant difference in your
link times. Use the <tt>llvm-ranlib</tt> tool to do this, as follows:</p>
<div class="doc_code">
<pre>
% cd $CFEINSTALL/lib
% llvm-ranlib libiberty.a
% llvm-ranlib libstdc++.a
% llvm-ranlib libsupc++.a
% cd $CFEINSTALL/lib/gcc/<i>target-triplet</i>/3.4-llvm
% llvm-ranlib libgcc.a
% llvm-ranlib libgcov.a
</pre>
</div>
</li>
<li><p>Test the newly-installed C frontend by one or more of the following
means:</p>
<ul>
<li>running the feature & regression tests via <tt>make
check</tt></li>
<li>compiling and running a "hello, LLVM" program in C and C++.</li>
<li>running the tests found in the <tt>llvm-test</tt> CVS module</li>
</ul></li>
</ol>
</div>
<!-- *********************************************************************** -->
<div class="doc_section">
<a name="license">License Information</a>
</div>
<div class="doc_text">
<p>
The LLVM GCC frontend is licensed to you under the GNU General Public License
and the GNU Lesser General Public License. Please see the files COPYING and
COPYING.LIB for more details.
</p>
<p>
More information is <a href="FAQ.html#license">available in the FAQ</a>.
</p>
</pre>
</div>
<!-- *********************************************************************** -->
<hr>
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