PATCH: X86 calling convention cleanup

The four X86 calling convention implementations in X86ISelLowering.cpp contain several hundred lines of duplicated code. This patch refines the copies so that diff reveals refactoring opportunities instead of noise. Okay to commit?

(My goal is to introduce a crazy new ABI.)

— Gordon

cconv.patch (22.4 KB)

Yes, looks good to me.

Thanks for signing up to do the refactoring! I know this code can use a good scrubbing.