This section describes how to acquire and build llvm-gcc 4.0 and 4.2, which are based on the GCC 4.0.1/4.2.1 front-ends respectively. Both front-ends support C, C++, Objective-C and Objective-C++. The 4.2 front-end also supports Ada and Fortran to some extent. Note that the instructions for building these front-ends are completely different (and much easier!) than those for building llvm-gcc3 in the past.
Retrieve the appropriate llvm-gcc4.x-y.z.source.tar.gz archive from the llvm web site.
It is also possible to download the sources of the llvm-gcc front end from a read-only mirror using subversion. To check out the 4.0 code for first time use:
svn co http://llvm.org/svn/llvm-project/llvm-gcc-4.0/trunk dst-directory
To check out the 4.2 code use:
svn co http://llvm.org/svn/llvm-project/llvm-gcc-4.2/trunk dst-directory
After that, the code can be be updated in the destination directory using:
The mirror is brought up to date every evening.
Building with support for Ada amounts to following the directions in the top-level README.LLVM file, adding ",ada" to EXTRALANGS, for example: EXTRALANGS=,ada
There are some complications however:
The only platform for which the Ada front-end is known to build is 32 bit intel x86 running linux. It is unlikely to build for other systems without some work.
The build requires having a compiler that supports Ada, C and C++. The Ada front-end is written in Ada so an Ada compiler is needed to build it. Compilers known to work with the LLVM 2.2 release are gcc-4.2 and the 2005 GNAT GPL Edition. LLVM from subversion also works with the 2006 and 2007 GNAT GPL Editions. The LLVM parts of llvm-gcc are written in C++ so a C++ compiler is needed to build them. The rest of gcc is written in C. Some linux distributions provide a version of gcc that supports all three languages (the Ada part often comes as an add-on package to the rest of gcc). Otherwise it is possible to combine two versions of gcc, one that supports Ada and C (such as the 2005 GNAT GPL Edition) and another which supports C++, see below.
Because the Ada front-end is experimental, it is wise to build the compiler with checking enabled. This causes it to run much slower, but helps catch mistakes in the compiler (please report any problems using LLVM bugzilla).
Supposing appropriate compilers are available, llvm-gcc with Ada support can be built on an x86-32 linux box using the following recipe:
Download the LLVM source and unpack it:
wget http://llvm.org/releases/2.2/llvm-2.2.tar.gz tar xzf llvm-2.2.tar.gz mv llvm-2.2 llvm
svn co http://llvm.org/svn/llvm-project/llvm/trunk llvm
Download the llvm-gcc-4.2 source and unpack it:
wget http://llvm.org/releases/2.2/llvm-gcc4.2-2.2.source.tar.gz tar xzf llvm-gcc4.2-2.2.source.tar.gz mv llvm-gcc4.2-2.2.source llvm-gcc-4.2
svn co http://llvm.org/svn/llvm-project/llvm-gcc-4.2/trunk llvm-gcc-4.2
Make a build directory llvm-objects for llvm and make it the current directory:
mkdir llvm-objects cd llvm-objects
Configure LLVM (here it is configured to install into /usr/local):
If you have a multi-compiler setup and the C++ compiler is not the default, then you can configure like this:
CXX=PATH_TO_C++_COMPILER ../llvm/configure --prefix=/usr/local
Build LLVM with checking enabled (use ENABLE_OPTIMIZED=1 to build without checking):
Install LLVM (optional):
Make a build directory llvm-gcc-4.2-objects for llvm-gcc and make it the current directory:
cd .. mkdir llvm-gcc-4.2-objects cd llvm-gcc-4.2-objects
Configure llvm-gcc (here it is configured to install into /usr/local). The --enable-checking flag turns on sanity checks inside the compiler. If you omit it then LLVM must be built with make ENABLE_OPTIMIZED=1. Additional languages can be appended to the --enable-languages switch, for example --enable-languages=ada,c,c++.
../llvm-gcc-4.2/configure --prefix=/usr/local --enable-languages=ada,c --enable-checking --enable-llvm=$PWD/../llvm-objects --disable-shared --disable-bootstrap --disable-multilib
If you have a multi-compiler setup, then you can configure like this:
export CC=PATH_TO_C_AND_ADA_COMPILER export CXX=PATH_TO_C++_COMPILER ../llvm-gcc-4.2/configure --prefix=/usr/local --enable-languages=ada,c --enable-checking --enable-llvm=$PWD/../llvm-objects --disable-shared --disable-bootstrap --disable-multilib
Build and install the compiler:
make make install
To build with support for Fortran, follow the directions in the top-level README.LLVM file, adding ",fortran" to EXTRALANGS, for example:
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.
More information is available in the FAQ.