docs/GCCFEBuildInstrs.html

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   7   <title>Building the LLVM GCC Front-End</title>
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  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
  33 on the GCC 4.2.1 front-end.  Supported languages are Ada, C, C++, Fortran,
  34 Objective-C and Objective-C++.  Note that the instructions for building these
  35 front-ends are completely different (and much easier!) than those for building
  36 llvm-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>
  49 svn 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
  75 top-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">
 119 wget http://llvm.org/releases/2.7/llvm-2.7.tgz
 120 tar xzf llvm-2.7.tgz
 121 mv 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">
 136 wget http://llvm.org/releases/2.7/llvm-gcc-4.2-2.7.source.tgz
 137 tar xzf llvm-gcc-4.2-2.7.source.tgz
 138 mv 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">
 145 svn 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">
 153 mkdir llvm-objects
 154 cd 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">
 168 CXX=<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">
 179 make
 180 </pre>
 181       </li>
 182
 183   <li><p>Install LLVM (optional):</p>
 184
 185 <pre class="doc_code">
 186 make 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">
 194 cd ..
 195 mkdir llvm-gcc-4.2-objects
 196 cd 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=$PWD/../llvm-objects \
 210                           --disable-bootstrap --disable-multilib
 211 </pre>
 212
 213       <p>If you have a multi-compiler setup, then you can configure like this:</p>
 214
 215 <pre class="doc_code">
 216 export CC=<b>PATH_TO_C_AND_ADA_COMPILER</b>
 217 export CXX=<b>PATH_TO_C++_COMPILER</b>
 218 ../llvm-gcc-4.2/configure --prefix=<b>/usr/local</b> --enable-languages=ada,c \
 219                           --enable-checking --enable-llvm=$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">
 227 make
 228 make 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">
 244 EXTRALANGS=,fortran
 245 </pre>
 246
 247 </div>
 248
 249 <!-- *********************************************************************** -->
 250 <h2><a name="license">License Information</a></h2>
 251 <!-- *********************************************************************** -->
 252
 253 <div>
 254 <p>
 255 The LLVM GCC frontend is licensed to you under the GNU General Public License
 256 and the GNU Lesser General Public License.  Please see the files COPYING and
 257 COPYING.LIB for more details.
 258 </p>
 259
 260 <p>
 261 More information is <a href="FAQ.html#license">available in the FAQ</a>.
 262 </p>
 263 </div>
 264
 265 <!-- *********************************************************************** -->
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