Re: [tip:x86/asm] x86: Prefer TZCNT over BFS

[Jan Beulich]

>>> On 17.09.12 at 19:05, "H. Peter Anvin" <hpa@xxxxxxxxx> wrote:
> Honestly, I don't see a reason to not do this unconditionally.  On
> anything but (pre-686-era) extremely old CPUs the cost of the extra
> prefix is zero.  On the really old CPUs the cost of the BSF instruction
> will dwarf the penalty cycle for the extra prefix, so the whole
> mechanism around doing it conditionally seems pointless.

I certainly don't mind re-submitting with the whole thing made
unconditional (implying that the prior version would be dropped
in any case).

Jan

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