Re: GCC 4.0.0 Performance Regressions?

[Jason Bucata <jbucata at tulsaconnect dot com>]

On Tue, May 10, 2005 at 11:46:38AM +0200, Giovanni Bajo wrote:
> Jason Bucata <jbucata@tulsaconnect.com> wrote:
> 
> >> You should try and isolate a single BYTEmark test which shows the
> >> biggest regression. It's better if you manage to pack the whole test
> >> as a single preprocessed source file. Theoretically, this file
> >> should be compilable and linkable, and the resulting binary should
> >> run for a while doing computations. 
> >> 
> >> With this kind of help, we can analyze the regression and see why
> >> it's slower with 4.0.0.
> > 
> > It was rather time-consuming but I managed to do it.  I picked the
> > numsort benchmark which had a serious regression:
> > http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21485
> 
> 
> Many, many thanks!
> 
> Giovanni Bajo

Would it help to report some others?  I might have time later this week to
work on some of the others, especially now that I have a much better idea of
what to look for.

OTOH I don't want to bother if the fix for this regression is likely to
impact the other regressions, too... unless these test cases later get
turned into regression tests for the compiler test suite or something.

Would it make a big difference to grab and use the latest snapshot, like the
bug guidelines suggest?  I'll give it a try if it really makes a big
difference to the optimizer detectives, but if it doesn't help I won't waste
my time.

Jason B.

-- 
"My interest is in the future; I am going to spend the rest of my life
there."
	-- Charles Kettering