This is a set of individual patches, which contain all the customizations to llvm/clang currently in the FreeBSD base system. These can be applied in alphabetical order to a pristine llvm/clang 3.7.0 source tree, for example by doing: svn co https://llvm.org/svn/llvm-project/llvm/trunk llvm-3.7.0 svn co https://llvm.org/svn/llvm-project/cfe/trunk llvm-3.7.0/tools/clang cd llvm-3.7.0 for p in /usr/src/contrib/llvm/patches/patch-*.diff; do patch -p0 -f -F0 -E -i $p -s || break done A number of these consist of hand-written modifications, specifically for FreeBSD, while most others are cherry pickings off the llvm and clang trunks. When a new version of llvm/clang is eventually imported, those latter ones will largely disappear.