Mike's primary complaint is bad register allocation. It is very important to keep the most important state consistently in registers. In my experience, compilers still struggle to do good register allocation in big and branchy functions.

Even perfect branch prediction cannot solve the problem of unnecessary spills.

I read a research paper that proved that the branch prediction issues are non-issue with modern predictors (eg. TTAGE). It is of course true that register spills happen, but it's not bad enough to want to write hand-written assembly. Especially when you simulate AOT-compiled code (eg. RISC-V and WASM), you will already be 3-10x faster than Lua already. For my purposes of using this kind of emulator for scripting, it is already fine.

Throw instruction counting into the mix, and you can even be faster than LuaJIT, although I'm not sure how it manages to screw up the counting so badly. I wrote a little bit about it here: https://medium.com/@fwsgonzo/time-to-first-instruction-53a04...