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7  <title>Building the LLVM GCC Front-End</title>
8</head>
9<body>
10
11<h1>
12  Building the LLVM GCC Front-End
13</h1>
14
15<ol>
16  <li><a href="#instructions">Building llvm-gcc from Source</a></li>
17  <li><a href="#ada">Building the Ada front-end</a></li>
18  <li><a href="#fortran">Building the Fortran front-end</a></li>
19  <li><a href="#license">License Information</a></li>
20</ol>
21
22<div class="doc_author">
23  <p>Written by the LLVM Team</p>
24</div>
25
26<!-- *********************************************************************** -->
27<h2><a name="instructions">Building llvm-gcc from Source</a></h2>
28<!-- *********************************************************************** -->
29
30<div>
31
32<p>This section describes how to acquire and build llvm-gcc 4.2, which is based
33on the GCC 4.2.1 front-end.  Supported languages are Ada, C, C++, Fortran,
34Objective-C and Objective-C++.  Note that the instructions for building these
35front-ends are completely different (and much easier!) than those for building
36llvm-gcc3 in the past.</p>
37
38<ol>
39  <li><p>Retrieve the appropriate llvm-gcc-4.2-<i>version</i>.source.tar.gz
40         archive from the <a href="http://llvm.org/releases/">LLVM web
41         site</a>.</p>
42
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 4.2 code
45         for first time use:</p>
46
47<div class="doc_code">
48<pre>
49svn co http://llvm.org/svn/llvm-project/llvm-gcc-4.2/trunk <i>dst-directory</i>
50</pre>
51</div>
52
53      <p>After that, the code can be be updated in the destination directory
54         using:</p>
55
56<div class="doc_code">
57<pre>svn update</pre>
58</div>
59
60      <p>The mirror is brought up to date every evening.</p></li>
61
62  <li>Follow the directions in the top-level <tt>README.LLVM</tt> file for
63      up-to-date instructions on how to build llvm-gcc.  See below for building
64      with support for Ada or Fortran.
65</ol>
66
67</div>
68
69<!-- *********************************************************************** -->
70<h2><a name="ada">Building the Ada front-end</a></h2>
71<!-- *********************************************************************** -->
72
73<div>
74<p>Building with support for Ada amounts to following the directions in the
75top-level <tt>README.LLVM</tt> file, adding ",ada" to EXTRALANGS, for example:
76<tt>EXTRALANGS=,ada</tt></p>
77
78<p>There are some complications however:</p>
79
80<ol>
81  <li><p>The only platform for which the Ada front-end is known to build is
82      32 bit intel x86 running linux.  It is unlikely to build for other
83      systems without some work.</p></li>
84  <li><p>The build requires having a compiler that supports Ada, C and C++.
85      The Ada front-end is written in Ada so an Ada compiler is needed to
86      build it.  Compilers known to work with the
87      <a href="http://llvm.org/releases/download.html">LLVM 2.7 release</a>
88      are <a href="http://gcc.gnu.org/releases.html">gcc-4.2</a> and the
89      2005, 2006 and 2007 versions of the
90      <a href="http://libre.adacore.com/">GNAT GPL Edition</a>.
91      <b>GNAT GPL 2008, gcc-4.3 and later will not work</b>.
92      The LLVM parts of llvm-gcc are written in C++ so a C++ compiler is
93      needed to build them.  The rest of gcc is written in C.
94      Some linux distributions provide a version of gcc that supports all
95      three languages (the Ada part often comes as an add-on package to
96      the rest of gcc).  Otherwise it is possible to combine two versions
97      of gcc, one that supports Ada and C (such as the
98      <a href="http://libre.adacore.com/">2007 GNAT GPL Edition</a>)
99      and another which supports C++, see below.</p></li>
100  <li><p>Because the Ada front-end is experimental, it is wise to build the
101      compiler with checking enabled.  This causes it to run much slower, but
102      helps catch mistakes in the compiler (please report any problems using
103      <a href="http://llvm.org/bugs/">LLVM bugzilla</a>).</p></li>
104  <li><p>The Ada front-end <a href="http://llvm.org/PR2007">fails to
105      bootstrap</a>, due to lack of LLVM support for
106      <tt>setjmp</tt>/<tt>longjmp</tt> style exception handling (used
107      internally by the compiler), so you must specify
108      <tt>--disable-bootstrap</tt>.</p></li>
109</ol>
110
111<p>Supposing appropriate compilers are available, llvm-gcc with Ada support can
112   be built on an x86-32 linux box using the following recipe:</p>
113
114<ol>
115  <li><p>Download the <a href="http://llvm.org/releases/download.html">LLVM source</a>
116      and unpack it:</p>
117
118<pre class="doc_code">
119wget http://llvm.org/releases/2.7/llvm-2.7.tgz
120tar xzf llvm-2.7.tgz
121mv llvm-2.7 llvm
122</pre>
123
124      <p>or <a href="GettingStarted.html#checkout">check out the
125      latest version from subversion</a>:</p>
126
127<pre class="doc_code">svn co http://llvm.org/svn/llvm-project/llvm/trunk llvm</pre>
128
129      </li>
130
131  <li><p>Download the
132      <a href="http://llvm.org/releases/download.html">llvm-gcc-4.2 source</a>
133      and unpack it:</p>
134
135<pre class="doc_code">
136wget http://llvm.org/releases/2.7/llvm-gcc-4.2-2.7.source.tgz
137tar xzf llvm-gcc-4.2-2.7.source.tgz
138mv llvm-gcc-4.2-2.7.source llvm-gcc-4.2
139</pre>
140
141      <p>or <a href="GettingStarted.html#checkout">check out the
142      latest version from subversion</a>:</p>
143
144<pre class="doc_code">
145svn co http://llvm.org/svn/llvm-project/llvm-gcc-4.2/trunk llvm-gcc-4.2
146</pre>
147      </li>
148
149  <li><p>Make a build directory <tt>llvm-objects</tt> for llvm and make it the
150      current directory:</p>
151
152<pre class="doc_code">
153mkdir llvm-objects
154cd llvm-objects
155</pre>
156      </li>
157
158  <li><p>Configure LLVM (here it is configured to install into <tt>/usr/local</tt>):</p>
159
160<pre class="doc_code">
161../llvm/configure --prefix=<b>/usr/local</b> --enable-optimized --enable-assertions
162</pre>
163
164      <p>If you have a multi-compiler setup and the C++ compiler is not the
165      default, then you can configure like this:</p>
166
167<pre class="doc_code">
168CXX=<b>PATH_TO_C++_COMPILER</b> ../llvm/configure --prefix=<b>/usr/local</b> --enable-optimized --enable-assertions
169</pre>
170
171      <p>To compile without checking (not recommended), replace
172      <tt>--enable-assertions</tt> with <tt>--disable-assertions</tt>.</p>
173
174      </li>
175
176  <li><p>Build LLVM:</p>
177
178<pre class="doc_code">
179make
180</pre>
181      </li>
182
183  <li><p>Install LLVM (optional):</p>
184
185<pre class="doc_code">
186make install
187</pre>
188      </li>
189
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>
192
193<pre class="doc_code">
194cd ..
195mkdir llvm-gcc-4.2-objects
196cd llvm-gcc-4.2-objects
197</pre>
198      </li>
199
200  <li><p>Configure llvm-gcc (here it is configured to install into <tt>/usr/local</tt>).
201      The <tt>--enable-checking</tt> flag turns on sanity checks inside the compiler.
202      To turn off these checks (not recommended), replace <tt>--enable-checking</tt>
203      with <tt>--disable-checking</tt>.
204      Additional languages can be appended to the <tt>--enable-languages</tt> switch,
205      for example <tt>--enable-languages=ada,c,c++</tt>.</p>
206
207<pre class="doc_code">
208../llvm-gcc-4.2/configure --prefix=<b>/usr/local</b> --enable-languages=ada,c \
209                          --enable-checking --enable-llvm=$PWD/../llvm-objects \
210			  --disable-bootstrap --disable-multilib
211</pre>
212
213      <p>If you have a multi-compiler setup, then you can configure like this:</p>
214
215<pre class="doc_code">
216export CC=<b>PATH_TO_C_AND_ADA_COMPILER</b>
217export CXX=<b>PATH_TO_C++_COMPILER</b>
218../llvm-gcc-4.2/configure --prefix=<b>/usr/local</b> --enable-languages=ada,c \
219                          --enable-checking --enable-llvm=$PWD/../llvm-objects \
220			  --disable-bootstrap --disable-multilib
221</pre>
222      </li>
223
224  <li><p>Build and install the compiler:</p>
225
226<pre class="doc_code">
227make
228make install
229</pre>
230      </li>
231</ol>
232
233</div>
234
235<!-- *********************************************************************** -->
236<h2><a name="fortran">Building the Fortran front-end</a></h2>
237<!-- *********************************************************************** -->
238
239<div>
240<p>To build with support for Fortran, follow the directions in the top-level
241<tt>README.LLVM</tt> file, adding ",fortran" to EXTRALANGS, for example:</p>
242
243<pre class="doc_code">
244EXTRALANGS=,fortran
245</pre>
246
247</div>
248
249<!-- *********************************************************************** -->
250<h2><a name="license">License Information</a></h2>
251<!-- *********************************************************************** -->
252
253<div>
254<p>
255The LLVM GCC frontend is licensed to you under the GNU General Public License
256and the GNU Lesser General Public License.  Please see the files COPYING and
257COPYING.LIB for more details.
258</p>
259
260<p>
261More information is <a href="FAQ.html#license">available in the FAQ</a>.
262</p>
263</div>
264
265<!-- *********************************************************************** -->
266
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274  <a href="http://llvm.org/">LLVM Compiler Infrastructure</a><br>
275  Last modified: $Date: 2011-04-22 20:30:22 -0400 (Fri, 22 Apr 2011) $
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