Not only the work of the C/C++ optimizer but the exact reason why C++ constexpr was designed - to compute expressions during the compile-time iff all its depend

Not only the work of the C/C++ optimizer but the exact reason why C++ constexpr was designed - to compute expressions during the compile-time iff all its dependants can be resolved during the compile time. If they don't it's still cool, they behave as a normal runtime function.