Re: [patch 1/13] Qsort

[Matt Mackall]

On Sun, Jan 23, 2005 at 05:58:00AM +0100, Felipe Alfaro Solana wrote:
> On 23 Jan 2005, at 03:39, Andi Kleen wrote:
> 
> >Felipe Alfaro Solana <lkml@xxxxxxx> writes:
> >>
> >>AFAIK, XOR is quite expensive on IA32 when compared to simple MOV
> >>operatings. Also, since the original patch uses 3 MOVs to perform the
> >>swapping, and your version uses 3 XOR operations, I don't see any
> >>gains.
> >
> >Both are one cycle latency for register<->register on all x86 cores
> >I've looked at. What makes you think differently?
> 
> I thought XOR was more expensie. Anyways, I still don't see any 
> advantage in replacing 3 MOVs with 3 XORs.

Again, no temporaries needed.

But I benched it and it was quite a bit slower.

-- 
Mathematics is the supreme nostalgia of our time.
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