Checking if an Integer is an Exact Binary Power

[tsbockman via Digitalmars-d]

On Monday, 25 April 2016 at 16:48:14 UTC, Lass Safin wrote:
> Example;
>
> import core.bitop;
> import core.cpuid;
>
> int count;
> if(hasPopcnt)
>     count = _popcnt; // Uses x86-instruction "popcnt".
> else
>     count = popcnt; // Phobos's software implementation.
>
> // Do stuff with count

That is not right (since 2.069, I think?). Adding that check just 
makes things slower and more complicated:

core.bitop.popcnt() itself already checks hasPopcnt, and forwards 
to the intrinsic if it is available.