Why if(__ctfe)?

[Ilya Yaroshenko via Digitalmars-d-learn]

On Tuesday, 16 September 2014 at 13:28:17 UTC, Rene Zwanenburg 
wrote:
> On Tuesday, 16 September 2014 at 13:17:28 UTC, Adam D. Ruppe 
> wrote:
>> On Tuesday, 16 September 2014 at 13:11:50 UTC, Ilya Yaroshenko 
>> wrote:
>>> Why not "static if(__ctfe)" ?
>>
>> ctfe is a runtime condition. The function has the same code 
>> when run at compile time, it is just being run in a different 
>> environment.
>
> Note that if(__ctfe) does not incur a runtime performance 
> penalty. Even in debug builds will the branch be removed.

It is a kind of magic ;)