[chacham15]

The difference here between the obvious method and the best method is 55ns. Is there a reason that this problem deserves this much attention for as little a difference in time? (I realize that it is 6.5x more, but if it isnt at the center of some core loop, the multiplicative factor doesnt really matter). What use cases are there for this?

[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.