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Re: Serious performance regression -- some tree optimizer questions
- From: Ulrich Weigand <Ulrich dot Weigand at de dot ibm dot com>
- To: Daniel Berlin <dberlin at dberlin dot org>
- Cc: gcc at gcc dot gnu dot org
- Date: Wed, 12 Jan 2005 19:13:18 +0100
- Subject: Re: Serious performance regression -- some tree optimizer questions
Daniel Berlin <dberlin@dberlin.org> wrote on 12/20/2004 01:25:49 AM:
> If you find it helps other testcases, or whatever, i'm happy to try to
> explore making that patch usable.
OK, the current situation w.r.t. mgrid is as follows:
With unmodified GCC, mgrid on 31-bit generates bad code due to a
combination of the problem fixed by your patch and IV selection
issues. On 64-bit, the problem addressed by your patch doesn't
occur, but we have problems due to IV sign-extension (and also
IV selection issues).
Now, with a combination of various ivopts patches by Zdenek
I'm able to get absolutely perfect code generated for mgrid
on 64-bit. However, on 31-bit we still run into the value
backsubstitution problem. If I now apply your patch in addition
to the ivopts patches used on 64-bit, I *also* get perfect code!
So, if we assume we can get the ivopts situation fixed in time,
your backsubstitution patch would definitely be helpful!
Mit freundlichen Gruessen / Best Regards
Ulrich Weigand
--
Dr. Ulrich Weigand
Linux for S/390 Design & Development
IBM Deutschland Entwicklung GmbH, Schoenaicher Str. 220, 71032 Boeblingen
Phone: +49-7031/16-3727 --- Email: Ulrich.Weigand@de.ibm.com