It is very hard to do, and LLVM has been difficult to use as a JIT in past projects (Unladen Swallow, for example). However, Apple is experimenting with this i

It is very hard to do, and LLVM has been difficult to use as a JIT in past projects (Unladen Swallow, for example). However, Apple is experimenting with this in their FTL (fourth tier LLVM-based) JIT project in JSC. Because Apple drives both JSC and LLVM, this has the highest chance of success of any similar project, I believe, so it is very interesting to watch.