The fun bit is right at the start when the author notices that the compiler spots this and optimizes it away.

We didn't get into the deeper question of benchmarking it vs. a three-register swap, because I suspect the latter would be handled entirely by register renaming and end up being faster due to not requiring allocation of an ALU unit. Difficult to benchmark that because in order for it to make a difference, you'd need to surround it with other arithmetic instructions.

A meta question is why this persists. It has the right qualities for a "party trick": slightly esoteric piece of knowledge, not actually that hard to understand when you do know about it, but unintuitive enough that most people don't spontaneously reinvent it.

See also: https://en.wikipedia.org/wiki/Fast_inverse_square_root , which requires a bit more maths.

The other classic use of XOR - cursor overdrawing - has also long since gone away. It used to be possible to easily draw a cursor on a monochrome display by XORing it in, then to move it you simply XOR it again, restoring the original image.