> And for the unlikely branch, isn’t the complier will compile this branch > into a cold branch that will do no harm to the function performance? The test (cmp insn or something like that) still needs to be there. Since there is only a simple assignment in the branch, the compiler may just choose not to have a cold branch in this case. The only difference is in which case you would jump here. You can see for yourself (and prove me wrong if it comes to it). Miroslav