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7 <title>Building the LLVM C/C++ Front-End</title>
11 <div class="doc_title">
12 Building the LLVM GCC Front-End
16 <li><a href="#instructions">Building llvm-gcc from Source</a></li>
17 <li><a href="#license">License Information</a></li>
20 <div class="doc_author">
21 <p>Written by the LLVM Team</p>
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25 <div class="doc_section">
26 <a name="instructions">Building llvm-gcc from Source</a>
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30 <div class="doc_text">
32 <p>This section describes how to acquire and build llvm-gcc 4.0 and 4.2, which are
33 based on the GCC 4.0.1/4.2.1 front-ends respectively. Both front-ends support C,
34 C++, Objective-C and Objective-C++. The 4.2 front-end also supports Ada and
35 Fortran to some extent. Note that the instructions for building these front-ends
36 are completely different (and much easier!) than those for building llvm-gcc3 in
40 <li><p>Retrieve the appropriate llvm-gcc4.x-y.z.source.tar.gz archive from the
41 <a href="http://llvm.org/releases/">llvm web site</a>.</p>
43 <p>It is also possible to download the sources of the llvm-gcc front end
44 from a read-only mirror using subversion. To check out the 4.0 code
45 for first time use:</p>
47 <div class="doc_code">
49 svn co http://llvm.org/svn/llvm-project/llvm-gcc-4.0/trunk <i>dst-directory</i>
53 <p>To check out the 4.2 code use:</p>
55 <div class="doc_code">
57 svn co http://llvm.org/svn/llvm-project/llvm-gcc-4.2/trunk <i>dst-directory</i>
61 <p>After that, the code can be be updated in the destination directory
64 <div class="doc_code">
68 <p>The mirror is brought up to date every evening.</p></li>
70 <li>Follow the directions in the top-level <tt>README.LLVM</tt> file for
71 up-to-date instructions on how to build llvm-gcc. See below for building
72 with support for Ada or Fortran.
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78 <div class="doc_section">
79 <a name="license">Building the Ada front-end</a>
82 <div class="doc_text">
83 <p>Building with support for Ada amounts to following the directions in the
84 top-level <tt>README.LLVM</tt> file, adding ",ada" to EXTRALANGS, for example:
85 <tt>EXTRALANGS=,ada</tt></p>
87 <p>There are some complications however:</p>
90 <li><p>The only platform for which the Ada front-end is known to build is
91 32 bit intel x86 running linux. It is unlikely to build for other
92 systems without some work.</p></li>
93 <li><p>The build requires having a compiler that supports Ada, C and C++.
94 The Ada front-end is written in Ada so an Ada compiler is needed to
95 build it. What is more, the Ada compiler must not be more recent
96 than what it is trying to compile, otherwise the build will fail.
97 This rules out gcc-4.3 (but not gcc-4.2) and also the
98 <a href="http://libre.adacore.com/">2007 GNAT GPL Edition</a>.
99 The LLVM parts of llvm-gcc are written in C++ so a C++
100 compiler is needed to build them. The rest of gcc is written in C.
101 Some linux distributions provide a version of gcc that supports all
102 three languages (the Ada part often comes as an add-on package to
103 the rest of gcc). Otherwise it is possible to combine two versions
104 of gcc, one that supports Ada and C (such as the
105 <a href="http://libre.adacore.com/">2006 GNAT GPL Edition</a>)
106 and another which supports C++, see below.</p></li>
107 <li><p>Because the Ada front-end is experimental, it is wise to build the
108 compiler with checking enabled. This causes it to run slower, but
109 helps catch mistakes in the compiler (please report any problems using
110 <a href="http://llvm.org/bugs">LLVM bugzilla</a>).</p></li>
113 <p>Supposing appropriate compilers are available, llvm-gcc with Ada support can
114 be built on an x86-32 linux box using the following recipe:</p>
117 <li><p>Download the <a href="http://llvm.org/releases/download.html">LLVM source</a>
120 <div class="doc_code">
121 <pre>wget http://llvm.org/releases/2.2/llvm-2.2.tar.gz
122 tar xzf llvm-2.2.tar.gz
123 mv llvm-2.2 llvm</pre>
126 <p>or <a href="http://llvm.org/docs/GettingStarted.html#checkout">check out the
127 latest version from subversion</a>:</p>
129 <div class="doc_code">
130 <pre>svn co http://llvm.org/svn/llvm-project/llvm/trunk llvm</pre>
135 <a href="http://llvm.org/releases/download.html">llvm-gcc-4.2 source</a>
138 <div class="doc_code">
139 <pre>wget http://llvm.org/releases/2.2/llvm-gcc4.2-2.2.source.tar.gz
140 tar xzf llvm-gcc4.2-2.2.source.tar.gz
141 mv llvm-gcc4.2-2.2.source llvm-gcc-4.2</pre>
144 <p>or <a href="http://llvm.org/docs/GettingStarted.html#checkout">check out the
145 latest version from subversion</a>:</p>
147 <div class="doc_code">
148 <pre>svn co http://llvm.org/svn/llvm-project/llvm-gcc-4.2/trunk llvm-gcc-4.2</pre>
152 <li><p>Make a build directory <tt>llvm-objects</tt> for llvm and make it the
153 current directory:</p>
155 <div class="doc_code">
156 <pre>mkdir llvm-objects
157 cd llvm-objects</pre>
161 <li><p>Configure LLVM (here it is configured to install into <tt>/usr/local</tt>):</p>
163 <div class="doc_code">
164 <pre>../llvm/configure --prefix=<b>/usr/local</b></pre>
167 <p>If you have a multi-compiler setup and the C++ compiler is not the
168 default, then you can configure like this:</p>
170 <div class="doc_code">
171 <pre>CXX=<b>PATH_TO_C++_COMPILER</b> ../llvm/configure --prefix=<b>/usr/local</b></pre>
175 <li><p>Build LLVM with checking enabled (use <tt>ENABLE_OPTIMIZED=1</tt> to
176 build without checking):</p>
178 <div class="doc_code">
179 <pre>make ENABLE_OPTIMIZED=0</pre>
183 <li><p>Install LLVM (optional):</p>
185 <div class="doc_code">
186 <pre>make install</pre>
190 <li><p>Make a build directory <tt>llvm-gcc-4.2-objects</tt> for llvm-gcc and make it the
191 current directory:</p>
193 <div class="doc_code">
196 mkdir llvm-gcc-4.2-objects
197 cd llvm-gcc-4.2-objects</pre>
201 <li><p>Configure llvm-gcc (here it is configured to install into <tt>/usr/local</tt>).
202 The <tt>--enable-checking</tt> flag turns on sanity checks inside the compiler.
203 If you omit it then LLVM must be built with <tt>make ENABLE_OPTIMIZED=1</tt>.
204 Additional languages can be appended to the --enable-languages switch,
205 for example <tt>--enable-languages=ada,c,c++</tt>.</p>
207 <div class="doc_code">
208 <pre>../llvm-gcc-4.2/configure --prefix=<b>/usr/local</b> --enable-languages=ada,c --enable-checking --enable-llvm=$PWD/../llvm-objects --disable-shared --disable-bootstrap --disable-multilib</pre>
211 <p>If you have a multi-compiler setup, then you can configure like this:</p>
212 <div class="doc_code">
215 export CC=<b>PATH_TO_C_AND_ADA_COMPILER</b>
216 export CXX=<b>PATH_TO_C++_COMPILER</b>
217 ../llvm-gcc-4.2/configure --prefix=<b>/usr/local</b> --enable-languages=ada,c --enable-checking --enable-llvm=$PWD/../llvm-objects --disable-shared --disable-bootstrap --disable-multilib</pre>
221 <li><p>Build and install the compiler:</p>
223 <div class="doc_code">
232 <!-- *********************************************************************** -->
233 <div class="doc_section">
234 <a name="license">Building the Fortran front-end</a>
237 <div class="doc_text">
239 To build with support for Fortran, follow the directions in the top-level
240 <tt>README.LLVM</tt> file, adding ",fortran" to EXTRALANGS, for example:</p>
242 <div class="doc_code">
250 <!-- *********************************************************************** -->
251 <div class="doc_section">
252 <a name="license">License Information</a>
255 <div class="doc_text">
257 The LLVM GCC frontend is licensed to you under the GNU General Public License
258 and the GNU Lesser General Public License. Please see the files COPYING and
259 COPYING.LIB for more details.
263 More information is <a href="FAQ.html#license">available in the FAQ</a>.
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