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Re: Patch: MOVE_RATIO on x86 prescott
On 8/27/05, Dale Johannesen <dalej@apple.com> wrote:
> On Aug 27, 2005, at 1:11 AM, Richard Guenther wrote:
> > On 8/27/05, Dale Johannesen <dalej@apple.com> wrote:
> >> Feedback from users led us to conclude this is set too low.
> >> The test here tries copying arrays of size 9 to 16 words with
> >> mainline (which uses 'rep movsl') and a modified copy with
> >> the patch below (which uses loads and stores); you'll see
> >> loads and stores are faster in all cases, by 2 to 1 or more.
>
> >> This patch increases MOVE_RATIO to 17 for Prescott, with
> >> the effect that the 'rep; movsl' sequence is never used.
> >> A SPEC run shows +1/2% on int (which is within the margin
> >> of error, really), break-even on FP. OK?
> >
> > I don't think this is appropriate for stage3
>
> Fair enough. It's not a regression or a bug, I guess.
>
> > - noting that MOVE_RATIO
> > will f.i. affect inlining and sra decisions.
>
> I know. The SPEC results convince me it's a good idea overall,
> considering all that. Do you think additional testing is needed?
> If so, what?
I suppose MOVE_RATIO is not changed for -Os? In any way,
comparing compile time and code size of SPEC and a CSiBE
run with -O2 would be useful.
Richard.