Re: Using POPCNT and other advanced bit manipulation instructions

Alvaro Herrera <alvherre@2ndquadrant.com> writes:
> Ah, I understand it now:
> https://stackoverflow.com/questions/25683690/confusion-about-bsr-and-lzcnt/43443701#43443701
> if you call LZCNT/TZCNT on a CPU that doesn't support it, it won't raise
> SIGILL or anything ... it'll just silently compute the wrong result.
> That's certainly not what I call a fallback!

Yeah, that's pretty nasty; it means there's no backstop for whether
your choose function gets it right :-(

Is POPCNT any better in this respect?

            regards, tom lane