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7 <title>Bootstrapping the LLVM C/C++ Front-End</title>
11 <div class="doc_title">
12 Bootstrapping the LLVM C/C++ Front-End
16 <li><a href="#cautionarynote">A Cautionary Note</a>
18 <li><a href="#cygwin">Building under Cygwin</a></li>
19 <li><a href="#aix">Building under AIX</a></li>
22 <li><a href="#instructions">llvm-gcc4 Instructions</a></li>
23 <li><a href="#llvm-gcc3-instructions">llvm-gcc3 Instructions</a></li>
24 <li><a href="#license">License Information</a></li>
27 <div class="doc_author">
28 <p>Written by Brian R. Gaeke and
29 <a href="http://nondot.org/sabre">Chris Lattner</a></p>
32 <!-- *********************************************************************** -->
33 <div class="doc_section">
34 <a name="cautionarynote">A Cautionary Note</a>
36 <!-- *********************************************************************** -->
38 <div class="doc_text">
39 <p>This document is intended to explain the process of building the
40 LLVM C/C++ front-end from its source code. You have to do this, for example, if
41 you are porting LLVM to a new architecture or operating system, if you are
42 working from Top-Of-Tree CVS/SVN, or if there is no precompiled snapshot
45 <p><b>NOTE:</b> This is currently a somewhat fragile, error-prone
46 process, and you should <b>only</b> try to do it if:</p>
49 <li>you really, really, really can't use the binaries we distribute</li>
50 <li>you are an elite GCC hacker.</li>
51 <li>you want to use the latest bits from CVS.</li>
54 <p>We welcome patches to help make this process simpler.</p>
57 <!--=========================================================================-->
58 <div class="doc_subsection">
59 <a name="cygwin">Building under Cygwin</a>
61 <!--=========================================================================-->
63 <div class="doc_text">
64 <p>If you are building LLVM and the GCC front-end under Cygwin, please note that
65 the LLVM and GCC makefiles do not correctly handle spaces in paths. To deal
66 with this issue, make sure that your LLVM and GCC source and build trees are
67 located in a top-level directory (like <tt>/cygdrive/c/llvm</tt> and
68 <tt>/cygdrive/c/llvm-cfrontend</tt>), not in a directory that contains a space
69 (which includes your "home directory", because it lives under the "Documents
70 and Settings" directory). We welcome patches to fix this issue.
72 <p>It has been found that the GCC 3.3.3 compiler provided with recent Cygwin
73 versions is incapable of compiling the LLVM GCC front-end correctly. If your
75 installation includes GCC 3.3.3, we <i>strongly</i> recommend that you download
76 GCC 3.4.3, build it separately, and use it for compiling the LLVM GCC front-end.
78 shown to work correctly.</p>
79 <p>Some versions of Cygwin utilize an experimental version of GNU binutils that
80 will cause the GNU <tt>ld</tt> linker to fail an assertion when linking
81 components of the libstdc++. It is recommended that you replace the entire
82 binutils package with version 2.15 such that "<tt>ld --version</tt>" responds
84 <pre>GNU ld version 2.15</pre>
86 <pre>GNU ld version 2.15.91 20040725</pre>
89 <!--=========================================================================-->
90 <div class="doc_subsection"><a name="aix">Building under AIX</a></div>
91 <div class="doc_text">
92 <p>If you are building LLVM and the GCC front-end under AIX, do NOT use GNU
93 Binutils. They are not stable under AIX and may produce incorrect and/or
94 invalid code. Instead, use the system assembler and linker.
98 <!-- *********************************************************************** -->
99 <div class="doc_section">
100 <a name="instructions">llvm-gcc4 Instructions</a>
102 <!-- *********************************************************************** -->
104 <div class="doc_text">
106 <p>This section describes how to aquire and build llvm-gcc4, which is based on
107 the GCC 4.0.1 front-end. This front-end supports C, C++, Objective-C, and
108 Objective-C++. Note that the instructions for building this front-end are
109 completely different than those for building llvm-gcc3.
114 <p>Retrieve the appropriate llvm-gcc4-x.y.source.tar.gz archive from the llvm
116 <p>It is also possible to download the sources of the llvm-gcc4 front end from
117 a read-only mirror using subversion. To check out the code the first time use:
120 <tt>svn co svn://anonsvn.opensource.apple.com/svn/llvm/trunk
121 <i>dst-directory</i></tt>
123 <p>After that, the code can be be updated in the destination directory using;
128 <p>The mirror is brought up to date every evening.</p>
131 <li>Follow the directions in the top-level README.LLVM file for up-to-date
132 instructions on how to build llvm-gcc4.</li>
136 <!-- *********************************************************************** -->
137 <div class="doc_section">
138 <a name="llvm-gcc3-instructions">llvm-gcc3 Instructions</a>
140 <!-- *********************************************************************** -->
142 <div class="doc_text">
144 <li>Aquire llvm-gcc3 from <a href="GettingStarted.html#checkout">LLVM CVS</a> or
145 from a <a href="http://llvm.org/releases/">release tarball</a>.</li>
147 <li><p>Configure and build the LLVM libraries and tools. There are two ways to
148 do this: either with <i>objdir</i> == <i>srcdir</i> or
149 <i>objdir</i> != <i>srcdir</i>. It is recommended
150 that <i>srcdir</i> be the same as <i>objdir</i> for your LLVM tree (but note
151 that you should always use <i>srcdir</i> != <i>objdir</i> for llvm-gcc):</p>
153 <li>With <i>objdir</i> != <i>srcdir</i>:<pre>
155 % <i>srcdir</i>/configure --prefix=/some/path/you/can/install/to [options...]
158 <li>With <i>objdir</i> == <i>srcdir</i>:<pre>
160 % ./configure --prefix=/some/path/you/can/install/to [options...]
164 <p>This will build all of the LLVM tools and libraries. The <tt>--prefix</tt>
165 option defaults to /usr/local (per configure standards) but unless you are a
166 system administrator, you probably won't be able to install LLVM there because
167 of permissions. Specify a path into which LLVM can be installed (e.g.
168 <tt>--prefix=/home/user/llvm</tt>).</p>
171 <li><p>Add the directory containing the tools to your PATH.</p>
173 % set path = ( `cd llvm/Debug/bin && pwd` $path )
176 <li><p>Unpack the C/C++ front-end source into cfrontend/src, either by
177 untar'ing a cfrontend.source.tar.gz file or checking out CVS into this
180 <li><p>Make "build" and "install" directories as siblings of the "src" tree:</p>
183 /usr/local/example/cfrontend/src
185 % mkdir build install
186 % set CFEINSTALL = `pwd`/install
190 <li><p>Configure, build, and install the GCC front-end:</p>
193 <b>Linux/x86:</b><br>
194 <b>Linux/IA-64:</b><br>
195 <b>MacOS X/PowerPC</b> (requires dlcompat library):<br>
201 % ../src/configure --prefix=$CFEINSTALL --disable-threads --disable-nls \
202 --disable-shared --enable-languages=c,c++ --program-prefix=llvm-
203 % gmake all; gmake install
206 <p><b>Cygwin/x86:</b></p>
210 % ../src/configure --prefix=$CFEINSTALL --disable-threads --disable-nls \
211 --disable-shared --enable-languages=c,c++ --disable-c-mbchar \
212 --program-prefix=llvm-
213 % gmake all; gmake install
216 <p><b>Solaris/SPARC:</b></p>
219 The GCC front-end can be configured for either SPARC V8 (32 bit) or SPARC V9 (64
220 bit). This changes, among other things, the sizes of integer types and the
221 macros defined for conditional compilation.
225 The SPARC V8 ABI support is more robust than the V9 ABI support and can generate
226 SPARC V9 code. It is highly recommended that you use the V8 ABI with LLVM, as
228 note that Solaris has trouble with various wide (multibyte) character
229 functions from C as referenced from C++, so we typically configure with
230 --disable-c-mbchar (cf. <a href="http://llvm.org/PR206">Bug 206</a>).
235 % ../src/configure --prefix=$CFEINSTALL --disable-threads --disable-nls \
236 --disable-shared --enable-languages=c,c++ --host=sparc-sun-solaris2.8 \
237 --disable-c-mbchar --program-prefix=llvm-
238 % gmake all; gmake install
241 <p><b>Common Problem:</b> You may get error messages regarding the fact
242 that LLVM does not support inline assembly. Here are two common
246 <li><p><b>Fix 1:</b> If you have system header files that include
247 inline assembly, you may have to modify them to remove the inline
248 assembly and install the modified versions in
249 <code>$CFEINSTALL/lib/gcc/<i>target-triplet</i>/3.4-llvm/include</code>.</li>
251 <li><b>Fix 2:</b> If you are building the C++ front-end on a CPU we
252 haven't tried yet, you will probably have to edit the appropriate
253 version of atomicity.h under
254 <code>src/libstdc++-v3/config/cpu/<i>name-of-cpu</i>/atomicity.h</code>
255 and apply a patch so that it does not use inline assembly.</li>
258 <p><b>Porting to a new architecture:</b> If you are porting the front-end
259 to a new architecture or compiling in a configuration that we have
260 not tried previously, there are probably several changes you will have to make
261 to the GCC target to get it to work correctly. These include:<p>
264 <li>Often targets include special assembler or linker flags which
265 <tt>gccas</tt>/<tt>gccld</tt> does not understand. In general, these can
266 just be removed.</li>
267 <li>LLVM currently does not support any floating point values other than
268 32-bit and 64-bit IEEE floating point. The primary effect of this is
269 that you may have to map "long double" onto "double".</li>
270 <li>The profiling hooks in GCC do not apply at all to the LLVM front-end.
271 These may need to be disabled.</li>
272 <li>No inline assembly for position independent code. At the LLVM level,
273 everything is position independent.</li>
274 <li>We handle <tt>.init</tt> and <tt>.fini</tt> differently.</li>
275 <li>You may have to disable multilib support in your target. Using multilib
276 support causes the GCC compiler driver to add a lot of "<tt>-L</tt>"
277 options to the link line, which do not relate to LLVM and confuse
278 <tt>gccld</tt>. To disable multilibs, delete any
279 <tt>MULTILIB_OPTIONS</tt> lines from your target files.</li>
280 <li>Did we mention that we don't support inline assembly? You'll probably
281 have to add some fixinclude hacks to disable it in the system
286 <li><p>Put <tt>$CFEINSTALL/bin</tt> into your <tt>PATH</tt> environment
289 <li>sh: <tt>export PATH=$CFEINSTALL/bin:$PATH</tt></li>
290 <li>csh: <tt>setenv PATH $CFEINSTALL/bin:$PATH</tt></li>
294 <li><p>Go back into the LLVM source tree proper. Rerun configure, using
295 the same options as the last time. This will cause the configuration to now find
296 the newly built llvm-gcc and llvm-g++ executables. </p></li>
298 <li><p>Rebuild your CVS tree. This shouldn't cause the whole thing to be
299 rebuilt, but it should build the runtime libraries. After the tree is
300 built, install the runtime libraries into your GCC front-end build tree.
301 These are the commands you need:</p>
304 % gmake -C runtime install-bytecode
307 <li><p>Optionally, build a symbol table for the newly installed runtime
308 libraries. Although this step is optional, you are strongly encouraged to
309 do this as the symbol tables will make a significant difference in your
310 link times. Use the <tt>llvm-ranlib</tt> tool to do this, as follows:</p>
313 % llvm-ranlib libiberty.a
314 % llvm-ranlib libstdc++.a
315 % llvm-ranlib libsupc++.a
316 % cd $CFEINSTALL/lib/gcc/<i>target-triplet</i>/3.4-llvm
317 % llvm-ranlib libgcc.a
318 % llvm-ranlib libgcov.a
321 <li><p>Test the newly-installed C frontend by one or more of the
324 <li> running the feature & regression tests via <tt>make check</tt></li>
325 <li> compiling and running a "hello, LLVM" program in C and C++.</li>
326 <li> running the tests found in the <tt>llvm-test</tt> CVS module</li>
331 <!-- *********************************************************************** -->
332 <div class="doc_section">
333 <a name="license">License Information</a>
336 <div class="doc_text">
338 The LLVM GCC frontend is licensed to you under the GNU General Public License
339 and the GNU Lesser General Public License. Please see the files COPYING and
340 COPYING.LIB for more details.
344 More information is <a href="FAQ.html#license">available in the FAQ</a>.
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