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Re: spec2k comparison of gcc 4.1 and 4.2 on AMD K8


On 2/25/07, Daniel Berlin <dberlin@dberlin.org> wrote:
On 2/24/07, Serge Belyshev <belyshev@depni.sinp.msu.ru> wrote:
> I have compared 4.1.2 release (r121943) with three revisions of 4.2 on spec2k
> on an 2GHz AMD Athlon64 box (in 64bit mode), detailed results are below.
>
> In short, current 4.2 performs just as good as 4.1 on this target
> with the exception of huge 80% win on 178.galgel. All other difference
> lies almost in the noise.
>
> results:
>
> first number in each column is a runtime difference in %
> between corresponding 4.2 revision and 4.1.2 (+ is better, - is worse).
>
> second number is a +- confidence interval, i.e. according to my results,
> current 4.2 does (82.0+-1.7)% better than 4.1.2 on 178.galgel.
>
> (note some results are clearly noisy, but I've tried hard to avoid this --
> I did three runs on a completely idle machine, wasting 14 hours of machine time in total).
>
> r117890 -- 4.2 just before DannyB's aliasing fixes
> r117891 -- 4.2 with aliasing fixes.
> r122236 -- 4.2 current.


Uh, these are the wrong revisions. 117890 is correct, but 117891 is superseded by 117922, which will make things worse than 117891 will.

This is why the current numbers are worse than the second column, my guess.

In particular, 117922 is goin

grrr. 117922 is going to make all nonlocal loads and stores link together, and 117891 will not.



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