llvm/docs/GCCFEBuildInstrs.html

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<title>Building the LLVM GCC Front-End</title>
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<body>
<div class="doc_title">
Building the LLVM GCC Front-End
</div>
<ol>
<li><a href="#instructions">Building llvm-gcc from Source</a></li>
<li><a href="#license">License Information</a></li>
</ol>
<div class="doc_author">
<p>Written by the LLVM Team</p>
</div>
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<div class="doc_section">
<a name="instructions">Building llvm-gcc from Source</a>
</div>
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<div class="doc_text">
<p>This section describes how to acquire and build llvm-gcc 4.0 and 4.2, which are
based on the GCC 4.0.1/4.2.1 front-ends respectively. Both front-ends support C,
C++, Objective-C and Objective-C++. The 4.2 front-end also supports Ada and
Fortran to some extent. Note that the instructions for building these front-ends
are completely different (and much easier!) than those for building llvm-gcc3 in
the past.</p>
<ol>
<li><p>Retrieve the appropriate llvm-gcc4.x-y.z.source.tar.gz archive from the
<a href="http://llvm.org/releases/">llvm web site</a>.</p>
<p>It is also possible to download the sources of the llvm-gcc front end
from a read-only mirror using subversion. To check out the 4.0 code
for first time use:</p>
<div class="doc_code">
<pre>
svn co http://llvm.org/svn/llvm-project/llvm-gcc-4.0/trunk <i>dst-directory</i>
</pre>
</div>
<p>To check out the 4.2 code use:</p>
<div class="doc_code">
<pre>
svn co http://llvm.org/svn/llvm-project/llvm-gcc-4.2/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-gcc. See below for building
with support for Ada or Fortran.
</ol>
</div>
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<div class="doc_section">
<a name="license">Building the Ada front-end</a>
</div>
<div class="doc_text">
<p>Building with support for Ada amounts to following the directions in the
top-level <tt>README.LLVM</tt> file, adding ",ada" to EXTRALANGS, for example:
<tt>EXTRALANGS=,ada</tt></p>
<p>There are some complications however:</p>
<ol>
<li><p>The only platform for which the Ada front-end is known to build is
32 bit intel x86 running linux. It is unlikely to build for other
systems without some work.</p></li>
<li><p>The build requires having a compiler that supports Ada, C and C++.
The Ada front-end is written in Ada so an Ada compiler is needed to
build it. Appropriate Ada compilers are gcc-4.2 (or earlier) or the
<a href="http://libre.adacore.com/">2006 GNAT GPL Edition</a>
(or earlier). As a general rule, the Ada compiler used for the
build must not be more recent than the Ada compiler it is building.
This is why the build fails with gcc-4.3 and the 2007 GNAT GPL Edition.
The LLVM parts of llvm-gcc are written in C++ so a C++ compiler is
needed to build them. The rest of gcc is written in C.
Some linux distributions provide a version of gcc that supports all
three languages (the Ada part often comes as an add-on package to
the rest of gcc). Otherwise it is possible to combine two versions
of gcc, one that supports Ada and C (such as the
<a href="http://libre.adacore.com/">2006 GNAT GPL Edition</a>)
and another which supports C++, see below.</p></li>
<li><p>Because the Ada front-end is experimental, it is wise to build the
compiler with checking enabled. This causes it to run slower, but
helps catch mistakes in the compiler (please report any problems using
<a href="http://llvm.org/bugs">LLVM bugzilla</a>).</p></li>
</ol>
<p>Supposing appropriate compilers are available, llvm-gcc with Ada support can
be built on an x86-32 linux box using the following recipe:</p>
<ol>
<li><p>Download the <a href="http://llvm.org/releases/download.html">LLVM source</a>
and unpack it:</p>
<div class="doc_code">
<pre>wget http://llvm.org/releases/2.2/llvm-2.2.tar.gz
tar xzf llvm-2.2.tar.gz
mv llvm-2.2 llvm</pre>
</div>
<p>or <a href="GettingStarted.html#checkout">check out the
latest version from subversion</a>:</p>
<div class="doc_code">
<pre>svn co http://llvm.org/svn/llvm-project/llvm/trunk llvm</pre>
</div>
</li>
<li><p>Download the
<a href="http://llvm.org/releases/download.html">llvm-gcc-4.2 source</a>
and unpack it:</p>
<div class="doc_code">
<pre>wget http://llvm.org/releases/2.2/llvm-gcc4.2-2.2.source.tar.gz
tar xzf llvm-gcc4.2-2.2.source.tar.gz
mv llvm-gcc4.2-2.2.source llvm-gcc-4.2</pre>
</div>
<p>or <a href="GettingStarted.html#checkout">check out the
latest version from subversion</a>:</p>
<div class="doc_code">
<pre>svn co http://llvm.org/svn/llvm-project/llvm-gcc-4.2/trunk llvm-gcc-4.2</pre>
</div>
</li>
<li><p>Make a build directory <tt>llvm-objects</tt> for llvm and make it the
current directory:</p>
<div class="doc_code">
<pre>mkdir llvm-objects
cd llvm-objects</pre>
</div>
</li>
<li><p>Configure LLVM (here it is configured to install into <tt>/usr/local</tt>):</p>
<div class="doc_code">
<pre>../llvm/configure --prefix=<b>/usr/local</b></pre>
</div>
<p>If you have a multi-compiler setup and the C++ compiler is not the
default, then you can configure like this:</p>
<div class="doc_code">
<pre>CXX=<b>PATH_TO_C++_COMPILER</b> ../llvm/configure --prefix=<b>/usr/local</b></pre>
</div>
</li>
<li><p>Build LLVM with checking enabled (use <tt>ENABLE_OPTIMIZED=1</tt> to
build without checking):</p>
<div class="doc_code">
<pre>make ENABLE_OPTIMIZED=0</pre>
</div>
</li>
<li><p>Install LLVM (optional):</p>
<div class="doc_code">
<pre>make install</pre>
</div>
</li>
<li><p>Make a build directory <tt>llvm-gcc-4.2-objects</tt> for llvm-gcc and make it the
current directory:</p>
<div class="doc_code">
<pre>
cd ..
mkdir llvm-gcc-4.2-objects
cd llvm-gcc-4.2-objects</pre>
</div>
</li>
<li><p>Configure llvm-gcc (here it is configured to install into <tt>/usr/local</tt>).
The <tt>--enable-checking</tt> flag turns on sanity checks inside the compiler.
If you omit it then LLVM must be built with <tt>make ENABLE_OPTIMIZED=1</tt>.
Additional languages can be appended to the --enable-languages switch,
for example <tt>--enable-languages=ada,c,c++</tt>.</p>
<div class="doc_code">
<pre>../llvm-gcc-4.2/configure --prefix=<b>/usr/local</b> --enable-languages=ada,c --enable-checking --enable-llvm=$PWD/../llvm-objects --disable-shared --disable-bootstrap --disable-multilib</pre>
</div>
<p>If you have a multi-compiler setup, then you can configure like this:</p>
<div class="doc_code">
<pre>
export CC=<b>PATH_TO_C_AND_ADA_COMPILER</b>
export CXX=<b>PATH_TO_C++_COMPILER</b>
../llvm-gcc-4.2/configure --prefix=<b>/usr/local</b> --enable-languages=ada,c --enable-checking --enable-llvm=$PWD/../llvm-objects --disable-shared --disable-bootstrap --disable-multilib</pre>
</div>
</li>
<li><p>Build and install the compiler:</p>
<div class="doc_code">
<pre>make
make install</pre>
</div>
</li>
</ol>
</div>
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<div class="doc_section">
<a name="license">Building the Fortran front-end</a>
</div>
<div class="doc_text">
<p>
To build with support for Fortran, follow the directions in the top-level
<tt>README.LLVM</tt> file, adding ",fortran" to EXTRALANGS, for example:</p>
<div class="doc_code">
<pre>
EXTRALANGS=,fortran
</pre>
</div>
</div>
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<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>
</div>
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