At least on x86, multiple additions and multiplications can be done with a single `lea` instruction so it's preferable to XOR. Though I have no idea about other architectures, compiler implementations, any interpreters...

That only helps with multiplications by statically known word sizes (4x, 8x, etc.) and not arbitrary x·y. It can help with many smaller constant multipliers if the complete is clever, but it has to be known at compile time.