** Installation procedure for Linux machines **
(takes a while)

(unfortunately it is not as simple as apt installing llvm-dev, because
the official ubuntu distribution does not contain all the useful librairies)

Install 3.4 for compatibility reasons.

1- download where you want

svn co http://llvm.org/svn/llvm-project/llvm/tags/RELEASE_34/final llvm

cd llvm/tools
svn co http://llvm.org/svn/llvm-project/cfe/tags/RELEASE_34/final clang

cd ../projects/
svn co http://llvm.org/svn/llvm-project/compiler-rt/tags/RELEASE_34/final compiler-rt

cd ../tools/clang/tools/
svn co http://llvm.org/svn/llvm-project/clang-tools-extra/tags/RELEASE_34/final extra

2 - Build

inside the llvm directory :

mkdir build
make -j4  

(it takes 30 min to compile on my machine)

(if you want to install it in /usr/local then )
sudo make install     (recommanded)

(patch for cmake)
locate LLVM-Config.cmake
(should be in /usr/share/llvm-3.4/cmake/)
(in this directory, make a symbolic link named LLVMConfig.cmake)
cd /usr/share/llvm-3.4/cmake/
ln -s LLVM-Config.cmake LLVMConfig.cmake

3 - Check 
(opt should be in the path :)
opt --version
locate libLLVMAnalysis.a
(should be somewhere, idealy in /usr/lib/llvm-3.4/lib/)
locate raw_ostream.h
(/usr/include/llvm-3.4/llvm/Support/)

4- Set Shell variables (as user)
(get the script)
wget http://laure.gonnord.org/pro/research/ER03_2015/llvm-setup2.sh
(first, edit the path on the first line)
chmod 755 llvm-setup2.sh
./llvm-setup2.sh
(!! this will modify your .bash_profile, do not forget to source it after)
source ~/.bash_profile