Written by Brian R. Gaeke
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.
NOTE: This is currently a somewhat fragile, error-prone process, and you should only try to do it if:
We welcome patches to help make this process simpler.
Configure and build the LLVM libraries and tools using:
% cd llvm % ./configure [options...] % gmake tools-only
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.
Add the directory containing the tools to your PATH.
% set path = ( `cd llvm/tools/Debug && pwd` $path )
Unpack the C/C++ front-end source into cfrontend/src.
Edit src/configure. Change the first line (starting w/ #!) to contain the correct full pathname of sh.
Make "build" and "install" directories as siblings of the "src" tree.
% pwd /usr/local/example/cfrontend/src % cd .. % mkdir build install % set CFEINSTALL = `pwd`/install
Configure, build and install the C front-end:
% cd build % ../src/configure --prefix=$CFEINSTALL --disable-nls --disable-shared \ --enable-languages=c,c++ % gmake all-gcc % setenv LLVM_LIB_SEARCH_PATH `pwd`/gcc % gmake all; gmake install
Common Problem: You may get error messages regarding the fact that LLVM does not support inline assembly. Here are two common fixes:
Fix 1: 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
src/libstdc++-v3/config/cpu/name-of-cpu/atomicity.hand apply a patch so that it does not use inline assembly.
Porting to a new architecture: 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:
Go back into the LLVM source tree proper. Edit Makefile.config
LLVMGCCDIR to the full pathname of the
$CFEINSTALL 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.)
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
(This should be the "include" directory in the same directory as the
libgcc.a library, which you can find by running
Build and install the runtime (bytecode) libraries by running:
% gmake -C runtime % mkdir $CFEINSTALL/bytecode-libs % gmake -C runtime install % setenv LLVM_LIB_SEARCH_PATH $CFEINSTALL/bytecode-libs
Test the newly-installed C frontend by one or more of the following means:
gmake -C test/Programs