It's not (by itself, at least). But you can give it hints, as in my example above (with __builtin_unreachable; other compilers have similar facilities, like __a

It's not (by itself, at least). But you can give it hints, as in my example above (with __builtin_unreachable; other compilers have similar facilities, like __assume in MSVC). The compiler should, in theory, be able to deduce that x % 113 is always 0, and therefore must be a multiple of 113.