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However, it requires that the JIT compiler knows about a lot of
optimisations. PyPy's JIT is full of those. It's not the fact that it has a
JIT compiler at all that makes it fast and not the fact that they compile
Python to machine code, it's the fact that they came up with a huge bunch
of specialisations that makes lots of code patterns fast once it detected
them. LLVM (or any other low-level JIT compiler) won't help at all with that.

Stefan

Very good point Stefan

I would just like to add that a lot of those also require changes in the object model which might render changes in CPython C API (like the introduction of maps). Certainly you can't keep the current C structures, which will already break some code.

Cheers,

fijal