There are a bunch of arguments in there that don't match my experience, which includes the JSC interpreter. JSC had an interpreter written in C++ and one written in assembly, and the main reason for using the assembly one was not raw perf - it was so the interpreter knows the JIT's ABI for fast JIT<->interpreter calls.

Mike's argument about control flow diamonds being bad for optimization is especially questionable. It's only bad if one branch of the diamond uses a lot more registers than the other, which as I said, can be fixed by using noinline.