-freduce-all-givs and fortran

[Toon Moene]

Andreas Jaeger wrote:

> Toon Moene <moene@knmi.nl> writes:

> >> Using -fno-move-all-movables  -fno-reduce-all-givs is a
> >> performance gain for 171.swim and 200.sixtrack but pessimizes
> >> 172.[m]grid and 173.app[lu], 168.wupwise is indifferent.
> >
> > Fascinating ... Do 171.swim and 200.sixtrack profit from loop
> > optimization *at all* ?  What happens if you use
> >
> > -O2 -march=athlon -malign-double -fno-strength-reduce

> I'll run some tests later.

Thanks.

> Anything else you like to see tested for
> those two?

Nothing that comes to mind now.  The problem is, for further
experimentation I need the source code, and shelling out $500 to SPEC
just for the pleasure of being able to look at 171.swim and 200.sixtrack
is a bit overdone, as far as I am concerned ...

However, it looks like there is a correlation between "getting a strong
boost from Jakub's giv-combine fix" and "doing bad with aggressive giv
strength reduction" (both 171.swim and 200.sixtrack).

It could be that both programs need a lot of extra registers for givs,
while somehow they are impossible to combine.  Unfortunately, I cannot
come up with example code that has this property, off hand.

--
Toon Moene, KNMI, PO Box 201, 3730 AE De Bilt, The Netherlands.
Tel. +31302206443, Fax +31302210407,  e-mail moene@knmi.nl
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