vortex peak performance regression

[Jan Hubicka]

> > Zoltan,
> > It looks like your patch:
> > + 2001-11-30  Zoltan Hidvegi <hzoli@hzoli.2y.net>
> > +
> > + 	* unroll.c (unroll_loop): Correct special exit cases.
> > +
> > causes regression in the spec2000 tester - most importantly the vortex
> > benchmark (- see www.suse.de/~aj/SPEC
> > 
> > It is not obvious for me why, but can you please double check
> > whether the regression is unavoidable.
> 
> I have to think more about it, as I was unable to quickly produce a
> testcase to show it is necessary.  But it only adds a single increment
> to the loop, but that also requires an extra register, that may be
> just enough to run out of registers.  I have no more time to think
The difference is small enought to make this possible explanation.
> about this today, I'll try to look at it tomorrow.  Which architecture
> did you run the test?  It can make a difference if it has
You may look at the pages for details - it is Athlon, so the register
pressure definitly does make sense.

Honza
> count-regiter loop or not.
> 
> Zoli