This is precisely the sort of thing you let the compiler worry about. Using godbolt.org I see that a constant multiplication by 30 is compiled to an `imul` in x

This is precisely the sort of thing you let the compiler worry about. Using godbolt.org I see that a constant multiplication by 30 is compiled to an `imul` in x86-64 (both clang and gcc) and `lsl`, `sub`, `lsl` in ARM64 (gcc).