Except code duplication destroys performance because the instruction cache isn't infinite. I think we can agree that the relooper isn't the optimal solution to this problem...it's a compromise that works pretty well, but its a compromise nonetheless. It also means that you need to involve the LLVM toolchain anyway, just like in pnacl. I don't know if pnacl is a better solution or asm.js, but what I do know is that both are compromise and both have advantages and disadvantages.