0 is not a power of 2

[Brian Schott via Digitalmars-d]

On Tuesday, 19 May 2015 at 20:01:29 UTC, deadalnix wrote:
> Have you tried things like :
>
> (x >> bsr(x)) == 1 ?
>
> I have no idea if this is faster or not, but worth trying.

https://issues.dlang.org/show_bug.cgi?id=14380

"If the content source operand is 0, the content of the 
destination operand is undefined" - This applies to both the bsf 
and bsr instructions.