The LLVM Compiler has the ability to optimize code and is preferable for intensive computational tasks. We have used LLVM in order to compile OpenSim.

Compiling mono's version of llvm:

git clone -b mono git://github.com/mono/llvm.git
cd llvm
git branch mono-2-11
git checkout mono-2-11
./configure --prefix=/opt/mono-2.11 --enable-optimized --enable-targets="x86 x86_64"
make
make install

Getting mono:

git clone git://github.com/mono/mono
cd mono
git branch mono-2-11
git checkout mono
cd mono
PATH="/opt/mono-2.11/bin:$PATH"
./configure --prefix=/opt/mono-2.11 --enable-llvm=yes
make
make install

Which installs a separate mono build in /opt/mono2.11.

It is important to note that the compilers mcs, gmcs, dmcs etc… Support the /sdk:VERSION flag which cannot be found in earlier mono versions. One has to make sure that the compilers are used from /opt/mono-2.11 instead of the mono version that may be installed on the system.

In order to do that, one should change the path such that:

PATH="/opt/mono-2.11/bin:$PATH"

it includes the path to the llvm-compiled mono before the system binaries.