Clang\LLVM has some heuristics where it will convert cmovs generated by earlier passes back in to jumps https://reviews.llvm.org/D34769. Also the compilers can't always prove its safe to evaluate both sides of a ternary operator which would be needed to use a cmov. Here's a compiler explorer sample for clang and GCC that shows all these problems https://godbolt.org/z/IpZfZv, you change the -x86-cmov-converter option to true re-enable clangs cmov converter which will disable cmov in the last function.