I haven't used SLEM, but checking its commits it seems that the last one was from early 2011, so it's updated to LLVM version 2.9 at the latest. The IR has significantly changed since then, so it would probably not be usable if you try to use it with a newer LLVM.
You can update it, of course, but perhaps a better option would be LLVM-J - Java bindings to LLVM. It's updated to LLVM 3.1, in which the IR is far closer to what it is right now, plus it's basically just a wrapper around LLVM's C API, so updating it yourself should be relatively simple.