llvm-6502/docs/CFEBuildInstrs.html
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<title>Bootstrapping the C/C++ Front-End</title>
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<div class="doc_title">
Bootstrapping the C/C++ Front-End
</div>
<p>This document is intended to explain the process of building the LLVM
C/C++ front-end, based on GCC 3.4, from source.</p>
<p><b>NOTE:</b> This is currently a somewhat fragile, error-prone
process, and you should only try to do it if (A) you really, really,
really can't use the binaries we distribute, and (B) you are a wicked
good GCC hacker.</p>
<p>We welcome patches to help make this process simpler.</p>
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<div class="doc_section">
<a name="instructions">Instructions</a>
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<p>
<ol>
<li><p>Configure and build the LLVM libraries and tools using:</p>
<pre>
% cd llvm
% ./configure [options...]
% gmake tools-only
</pre>
<p>The use of the non-default target "tools-only" means that the
LLVM tools and libraries will build, and the binaries will be
deposited in llvm/tools/Debug, but the runtime (bytecode)
libraries will not build.</p></li>
<li><p>Add the directory containing the tools to your PATH.</p>
<pre>
% set path = ( `cd llvm/tools/Debug &amp;&amp; pwd` $path )
</pre></li>
<li><p>Unpack the C/C++ front-end source into cfrontend/src.</p></li>
<li><p>Edit src/configure. Change the first line (starting w/ #!) to
contain the correct full pathname of sh.</p></li>
<li><p>Make "build" and "install" directories as siblings of the "src"
tree.</p>
<pre>
% pwd
/usr/local/example/cfrontend/src
% cd ..
% mkdir build install
% set CFEINSTALL = `pwd`/install
</pre></li>
<li><p>Configure, build and install the C front-end:</p>
<pre>
% cd build
% ../src/configure --prefix=$CFEINSTALL --disable-nls --disable-shared \
--enable-languages=c,c++
% gmake all-gcc
% setenv LLVM_LIB_SEARCH_PATH `pwd`/gcc
% gmake all; gmake install
</pre>
<p><b>Common Problem 1:</b> You may get error messages regarding the fact
that LLVM does not support inline assembly. Here are two common
fixes:</p>
<ul>
<li><p><b>Fix 1:</b> If you have system header files that include
inline assembly, you may have to modify them to remove the inline
assembly, and install the modified versions in
<code>$CFEINSTALL/<i>target-triplet</i>/sys-include</code>.</p></li>
<li><b>Fix 2:</b> If you are building the C++ front-end on a CPU we
haven't tried yet, you will probably have to edit the appropriate
version of atomicity.h under
<code>src/libstdc++-v3/config/cpu/<i>name-of-cpu</i>/atomicity.h</code>
and apply a patch so that it does not use inline assembly.</p></li>
</ul>
<p><b>Common Problem 2:</b> <b>FIXME:</b> Chris should add a section about
common problems porting to a new architecture, including changes you
might have to make to the <tt>gcc/gcc/config/<i>name-of-cpu</i></tt>
directory. For example (expand these):</p>
<ul>
<li>Munge linker flags so they are compatible with <tt>gccld</tt>.</li>
<li>Change the target so it doesn't have long double; just use double
instead.</li>
<li>No inline assembly for position independent code.</li>
<li>We handle init and fini differently.</li>
<li>Do not include inline assembly map things for SPARC, or profile
things.</li>
</ul>
</li>
<li><p>Go back into the LLVM source tree proper. Edit Makefile.config
to redefine <code>LLVMGCCDIR</code> to the full pathname of the
<code>$CFEINSTALL</code> directory, which is the directory you just
installed the C front-end into. (The ./configure script is likely to
have set this to a directory which does not exist on your system.)</p></li>
<li><p>If you edited header files during the C/C++ front-end build as
described in "Fix 1" above, you must now copy those header files from
<code>$CFEINSTALL/<i>target-triplet</i>/sys-include</code> to
<code>$CFEINSTALL/lib/gcc/<i>target-triplet</i>/3.4-llvm/include</code>.
(This should be the "include" directory in the same directory as the
libgcc.a library, which you can find by running
<code>$CFEINSTALL/bin/gcc --print-libgcc-file-name</code>.)</p></li>
<li><p>Build and install the runtime (bytecode) libraries by running:</p>
<pre>
% gmake -C runtime
% mkdir $CFEINSTALL/bytecode-libs
% gmake -C runtime install
% setenv LLVM_LIB_SEARCH_PATH $CFEINSTALL/bytecode-libs
</pre></li>
<li><p>Test the newly-installed C frontend by one or more of the
following means:</p>
<ul>
<li> compiling and running a "hello, world" program in C or C++.</li>
<li> running the tests under test/Programs using <code>gmake -C
test/Programs</code></li>
</ul>
</p>
</li>
</ol>
</div>
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<hr><font size="-1">
<address><a href="mailto:gaeke -at- uiuc.edu">Brian Gaeke</a></address>
Last modified: $Date$
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