Building the LLVM GCC Front-End

+ +

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:
+ +
+
```
svn update
```
+
+ +
The mirror is brought up to date every evening.
Follow the directions in the top-level README.LLVM file for + up-to-date instructions on how to build llvm-gcc. See below for building + with support for Ada or Fortran. +

+ +

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. What is more, the Ada compiler must not be more recent + than what it is trying to compile, otherwise the build will fail. + This rules out gcc-4.3 (but not gcc-4.2) and also the + 2007 GNAT GPL Edition. + 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 + 2006 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 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

+ +

or check out the + latest version from subversion:

+ +

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

+ +

or check out the + latest version from subversion:

+ +

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):
+ +
+
```
../llvm/configure --prefix=/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):
+ +
+
```
make ENABLE_OPTIMIZED=0
```
+
+
Install LLVM (optional):
+ +
+
```
make install
```
+
+
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
```
+
+

+ +