0 is not a power of 2

[Steven Schveighoffer via Digitalmars-d]

On 5/19/15 5:32 PM, deadalnix wrote:
> On Tuesday, 19 May 2015 at 20:09:23 UTC, Steven Schveighoffer wrote:
>> On 5/19/15 4:01 PM, deadalnix wrote:
>>> Have you tried things like :
>>>
>>> (x >> bsr(x)) == 1 ?
>>>
>>> I have no idea if this is faster or not, but worth trying.
>>
>> Hm.. I think this would always succeed. Perhaps you mean:
>>
>> 1 << bsr(x) == x;
>>
>
> Both work as long as you use a fully defined instruction, like tzcnt.

Hm... I messed up, (x >> bsr(x)) is always zero. I think you meant to write:

x >> (bsr(x) - 1)

which always is 1.

Either way, it doesn't work.

-Steve