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6 <title>Bootstrapping the LLVM C/C++ Front-End</title>
10 <div class="doc_title">
11 Bootstrapping the LLVM C/C++ Front-End
15 <li><a href="#cautionarynote">A Cautionary Note</a>
16 <li><a href="#instructions">Instructions</a>
17 <li><a href="#license">License Information</a>
20 <div class="doc_text">
21 <p><b>Written by Brian R. Gaeke</b></p>
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25 <div class="doc_section">
26 <a name="cautionarynote">A Cautionary Note</a>
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30 <div class="doc_text">
31 <p>This document is intended to explain the process of building the
32 LLVM C/C++ front-end, based on GCC 3.4, from its source code. You
33 would have to do this, for example, if you are porting LLVM to a new
34 architecture or operating system.</p>
36 <p><b>NOTE:</b> This is currently a somewhat fragile, error-prone
37 process, and you should <b>only</b> try to do it if:</p>
40 <li>you really, really, really can't use the binaries we distribute</li>
41 <li>you need GCC to fix some of the header files on your system</li>
42 <li>you are an elite GCC hacker.</li>
45 <p>We welcome patches to help make this process simpler.</p>
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49 <div class="doc_section">
50 <a name="instructions">Instructions</a>
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54 <div class="doc_text">
57 <li><p>Configure and build the LLVM libraries and tools using:</p>
60 % ./configure [options...]
63 <p>The use of the non-default target "tools-only" means that the
64 LLVM tools and libraries will build, and the binaries will be
65 deposited in llvm/tools/Debug, but the runtime (bytecode)
66 libraries will not build.</p></li>
68 <li><p>Add the directory containing the tools to your PATH.</p>
70 % set path = ( `cd llvm/tools/Debug && pwd` $path )
73 <li><p>Unpack the C/C++ front-end source into cfrontend/src.</p></li>
75 <li><p>Edit src/configure. Change the first line (starting w/ #!) to
76 contain the correct full pathname of sh.</p></li>
78 <li><p>Make "build" and "install" directories as siblings of the "src"
82 /usr/local/example/cfrontend/src
85 % set CFEINSTALL = `pwd`/install
88 <li><p>Configure, build, and install the C front-end:</p>
96 % ../src/configure --prefix=$CFEINSTALL --disable-threads --disable-nls --disable-shared \
97 --enable-languages=c,c++
99 % setenv LLVM_LIB_SEARCH_PATH `pwd`/gcc
100 % gmake all; gmake install
104 <b>Solaris/SPARC:</b>
108 For Solaris/SPARC, LLVM only supports the SPARC V9. Therefore, the
109 configure command line should specify sparcv9, as shown below. Also,
110 note that Solaris has trouble with various wide (multibyte) character
111 functions from C as referenced from C++, so we typically configure with
112 --disable-c-mbchar (cf. <a href="http://llvm.cs.uiuc.edu/PR206">Bug 206</a>).
117 % ../src/configure --prefix=$CFEINSTALL --disable-threads --disable-nls \
118 --disable-shared --enable-languages=c,c++ --host=sparcv9-sun-solaris2.8 \
121 % setenv LLVM_LIB_SEARCH_PATH `pwd`/gcc
122 % gmake all; gmake install
125 <p><b>Common Problem:</b> You may get error messages regarding the fact
126 that LLVM does not support inline assembly. Here are two common
130 <li><p><b>Fix 1:</b> If you have system header files that include
131 inline assembly, you may have to modify them to remove the inline
132 assembly, and install the modified versions in
133 <code>$CFEINSTALL/<i>target-triplet</i>/sys-include</code>.</p></li>
135 <li><b>Fix 2:</b> If you are building the C++ front-end on a CPU we
136 haven't tried yet, you will probably have to edit the appropriate
137 version of atomicity.h under
138 <code>src/libstdc++-v3/config/cpu/<i>name-of-cpu</i>/atomicity.h</code>
139 and apply a patch so that it does not use inline assembly.</p></li>
142 <p><b>Porting to a new architecture:</b> If you are porting the new front-end
143 to a new architecture, or compiling in a different configuration that we have
144 previously, there are probably several changes you will have to make to the GCC
145 target to get it to work correctly. These include:<p>
148 <li>Often targets include special or assembler linker flags which
149 <tt>gccas</tt>/<tt>gccld</tt> does not understand. In general, these can
150 just be removed.</li>
151 <li>LLVM currently does not support any floating point values other than
152 32-bit and 64-bit IEEE floating point. The primary effect of this is
153 that you may have to map "long double" onto "double".</li>
154 <li>The profiling hooks in GCC do not apply at all to the LLVM front-end.
155 These may need to be disabled.</li>
156 <li>No inline assembly for position independent code. At the LLVM level,
157 everything is position independent.</li>
158 <li>We handle <tt>.init</tt> and <tt>.fini</tt> differently.</li>
159 <li>You may have to disable multilib support in your target. Using multilib
160 support causes the GCC compiler driver to add a lot of "<tt>-L</tt>"
161 options to the link line, which do not relate to LLVM and confuse
162 <tt>gccld</tt>. To disable multilibs, delete any
163 <tt>MULTILIB_OPTIONS</tt> lines from your target files.</li>
164 <li>Did we mention that we don't support inline assembly? You'll probably
165 have to add some fixinclude hacks to disable it in the system
170 <li><p>Go back into the LLVM source tree proper. Edit Makefile.config
171 to redefine <code>LLVMGCCDIR</code> to the full pathname of the
172 <code>$CFEINSTALL</code> directory, which is the directory you just
173 installed the C front-end into. (The ./configure script is likely to
174 have set this to a directory which does not exist on your system.)</p></li>
176 <li><p>If you edited header files during the C/C++ front-end build as
177 described in "Fix 1" above, you must now copy those header files from
178 <code>$CFEINSTALL/<i>target-triplet</i>/sys-include</code> to
179 <code>$CFEINSTALL/lib/gcc/<i>target-triplet</i>/3.4-llvm/include</code>.
180 (This should be the "include" directory in the same directory as the
181 libgcc.a library, which you can find by running
182 <code>$CFEINSTALL/bin/gcc --print-libgcc-file-name</code>.)</p></li>
184 <li><p>Build and install the runtime (bytecode) libraries by running:</p>
187 % mkdir $CFEINSTALL/bytecode-libs
188 % gmake -C runtime install-bytecode
189 % setenv LLVM_LIB_SEARCH_PATH $CFEINSTALL/bytecode-libs
192 <li><p>Test the newly-installed C frontend by one or more of the
195 <li> compiling and running a "hello, LLVM" program in C and C++.</li>
196 <li> running the tests under <tt>test/Programs</tt> using <code>gmake -C
197 test/Programs</code></li>
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205 <div class="doc_section">
206 <a name="license">License Information</a>
209 <div class="doc_text">
211 The LLVM GCC frontend is licensed to you under the GNU General Public License
212 and the GNU Lesser General Public License. Please see the files COPYING and
213 COPYING.LIB for more details.
217 The software also has the following additional copyrights:
222 Hewlett-Packard Company
224 Permission to use, copy, modify, distribute and sell this software
225 and its documentation for any purpose is hereby granted without fee,
226 provided that the above copyright notice appear in all copies and
227 that both that copyright notice and this permission notice appear
228 in supporting documentation. Hewlett-Packard Company makes no
229 representations about the suitability of this software for any
230 purpose. It is provided "as is" without express or implied warranty.
232 Copyright (c) 1996, 1997, 1998, 1999
233 Silicon Graphics Computer Systems, Inc.
235 Permission to use, copy, modify, distribute and sell this software
236 and its documentation for any purpose is hereby granted without fee,
237 provided that the above copyright notice appear in all copies and
238 that both that copyright notice and this permission notice appear
239 in supporting documentation. Silicon Graphics makes no
240 representations about the suitability of this software for any
241 purpose. It is provided "as is" without express or implied warranty.
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249 <div class="doc_footer">
250 <address>Brian Gaeke</address>
251 <a href="http://llvm.cs.uiuc.edu">The LLVM Compiler Infrastructure</a>
253 Last modified: $Date$