[Renaud]

I suppose the point was to show that it's pretty bad to resort to copy/pasting clever bit hacks into libraries without taking care of how they work.

The fact that the code isn't necessarily obvious makes me think that whoever used it was hoping for an optimisation of sorts.

Terseness can lead to obfuscation, and that's the wrong sort of optimisation. So we can hope that the developer was going for speed instead, but the results show that was a huge failure.

Maybe this won't affect performance in this particular library, maybe it's called once or twice and it doesn't matter, but if this is part of the innards of a game or a cryptographic function or some low-level network stack, it could have very detrimental consequences on performance.