Macports keeps 3 different versions of LLVM installed
I was forced to uninstall all packages depending on llvm-3.3 and llvm-3.4, and then reinstall them. In my case, all of reinstalled packages had dependencies on llvm-3.5, not on llvm-3.3/3.4, thus there were no problems when I uninstalled both llvm-3.3 and llvm-3.4. I hope it works for you.