<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /> <link rel="stylesheet" href="llvm.css" type="text/css" media="screen" /> <title>Bootstrapping the LLVM C/C++ Front-End</title> </head> <body> <div class="doc_title"> Bootstrapping the LLVM C/C++ Front-End </div> <ol> <li><a href="#cautionarynote">A Cautionary Note</a> <li><a href="#instructions">Instructions</a> <li><a href="#license">License Information</a> </ol> <div class="doc_text"> <p><b>Written by Brian R. Gaeke</b></p> </div> <!-- *********************************************************************** --> <div class="doc_section"> <a name="cautionarynote">A Cautionary Note</a> </div> <!-- *********************************************************************** --> <div class="doc_text"> <p>This document is intended to explain the process of building the LLVM C/C++ front-end, based on GCC 3.4, from its source code. You would have to do this, for example, if you are porting LLVM to a new architecture or operating system.</p> <p><b>NOTE:</b> This is currently a somewhat fragile, error-prone process, and you should <b>only</b> try to do it if:</p> <ol> <li>you really, really, really can't use the binaries we distribute</li> <li>you need GCC to fix some of the header files on your system</li> <li>you are an elite GCC hacker.</li> </ol> <p>We welcome patches to help make this process simpler.</p> </div> <!-- *********************************************************************** --> <div class="doc_section"> <a name="instructions">Instructions</a> </div> <!-- *********************************************************************** --> <div class="doc_text"> <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 && pwd` $path ) </pre></li> <li><p>Unpack the C/C++ front-end source into cfrontend/src.</p></li> <li><p>Edit src/configure. Change the first line (starting w/ #!) to contain the correct full pathname of sh.</p></li> <li><p>Make "build" and "install" directories as siblings of the "src" tree.</p> <pre> % pwd /usr/local/example/cfrontend/src % cd .. % mkdir build install % set CFEINSTALL = `pwd`/install </pre></li> <li><p>Configure, build, and install the C front-end:</p> <p> <b>Linux/x86:</b> </p> <pre> % cd build % ../src/configure --prefix=$CFEINSTALL --disable-threads --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>Solaris/Sparc:</b> </p> <p> For Solaris/Sparc, LLVM only supports SparcV9. Therefore, the configure command line should like something like this: </p> <pre> % cd build % ../src/configure --prefix=$CFEINSTALL --disable-threads --disable-nls --disable-shared \ --enable-languages=c,c++ --host=sparcv9-sun-solaris2.8 % gmake all-gcc % setenv LLVM_LIB_SEARCH_PATH `pwd`/gcc % gmake all </pre> <p> At this point, libstdc++ may fail to build because of wchar errors (look for errors that reference <tt>vfwscanf</tt> or <tt>wcstof</tt>). If that happens, edit <tt>sparcv9-sun-solaris2.8/libstdc++-v3/config.h</tt> and comment out the line that defines <tt>_GLIBCXX_USE_WCHAR_T</tt>. </p> <p> Then, continue as below: </p> <pre> % gmake all % gmake install </pre> <p><b>Common Problem:</b> You may get error messages regarding the fact that LLVM does not support inline assembly. Here are two common fixes:</p> <ul> <li><p><b>Fix 1:</b> If you have system header files that include inline assembly, you may have to modify them to remove the inline assembly, and install the modified versions in <code>$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>Porting to a new architecture:</b> If you are porting the new front-end to a new architecture, or compiling in a different configuration that we have previously, there are probably several changes you will have to make to the GCC target to get it to work correctly. These include:<p> <ul> <li>Often targets include special or assembler linker flags which <tt>gccas</tt>/<tt>gccld</tt> does not understand. In general, these can just be removed.</li> <li>LLVM currently does not support any floating point values other than 32-bit and 64-bit IEEE floating point. The primary effect of this is that you may have to map "long double" onto "double".</li> <li>The profiling hooks in GCC do not apply at all to the LLVM front-end. These may need to be disabled.</li> <li>No inline assembly for position independent code. At the LLVM level, everything is position independent.</li> <li>We handle <tt>.init</tt> and <tt>.fini</tt> differently.</li> <li>You may have to disable multilib support in your target. Using multilib support causes the GCC compiler driver to add a lot of "<tt>-L</tt>" options to the link line, which do not relate to LLVM and confuse <tt>gccld</tt>. To disable multilibs, delete any <tt>MULTILIB_OPTIONS</tt> lines from your target files.</li> <li>Did we mention that we don't support inline assembly? You'll probably have to add some fixinclude hacks to disable it in the system headers.</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, LLVM" program in C and C++.</li> <li> running the tests under <tt>test/Programs</tt> using <code>gmake -C test/Programs</code></li> </ul> </p> </li> </ol> </div> <!-- *********************************************************************** --> <div class="doc_section"> <a name="license">License Information</a> </div> <div class="doc_text"> <p> The LLVM GCC frontend is licensed to you under the GNU General Public License and the GNU Lesser General Public License. Please see the files COPYING and COPYING.LIB for more details. </p> <p> The software also has the following additional copyrights: </p> <pre> Copyright (c) 1994 Hewlett-Packard Company Permission to use, copy, modify, distribute and sell this software and its documentation for any purpose is hereby granted without fee, provided that the above copyright notice appear in all copies and that both that copyright notice and this permission notice appear in supporting documentation. Hewlett-Packard Company makes no representations about the suitability of this software for any purpose. It is provided "as is" without express or implied warranty. Copyright (c) 1996, 1997, 1998, 1999 Silicon Graphics Computer Systems, Inc. Permission to use, copy, modify, distribute and sell this software and its documentation for any purpose is hereby granted without fee, provided that the above copyright notice appear in all copies and that both that copyright notice and this permission notice appear in supporting documentation. Silicon Graphics makes no representations about the suitability of this software for any purpose. It is provided "as is" without express or implied warranty. </pre> </div> <!-- *********************************************************************** --> <!-- *********************************************************************** --> <hr> <div class="doc_footer"> <address>Brian Gaeke</address> <a href="http://llvm.cs.uiuc.edu">The LLVM Compiler Infrastructure</a> <br> Last modified: $Date$ </div> </body> </html>