It is too early to assume that. It just fails to optimize that specific piece of library code, but when the author implements it himself LLVM does choose cmov i

It is too early to assume that. It just fails to optimize that specific piece of library code, but when the author implements it himself LLVM does choose cmov instructions. It still can find the optimization but either something is preventing that in the first case, or llvm’s model thinks the alternative is faster.