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Re: [PATCH]: Add -fno-tree-reassoc to "fix" PR target/27855
- From: "H.J. Lu" <hjl at lucon dot org>
- To: Uros Bizjak <ubizjak at gmail dot com>
- Cc: GCC Patches <gcc-patches at gcc dot gnu dot org>
- Date: Mon, 9 Jul 2007 12:59:07 -0700
- Subject: Re: [PATCH]: Add -fno-tree-reassoc to "fix" PR target/27855
- References: <46927A7D.5020404@gmail.com>
On Mon, Jul 09, 2007 at 08:12:13PM +0200, Uros Bizjak wrote:
> Hello!
>
> The problem with current reassociation pass is, that it produces
> significantly slower code for various tight matrix multiplication loops.
> One example is taken from PR target/27855 and I was trying to test the
> code, produced with current gcc mainline.
>
> The tests were performed on core2 in 64bit mode, using '-DREPS=10000 -O3
> -msse3 -march=core2 -ffast-math' flags, with and without newly
> introduced -fno-tree-reassoc flag.
>
> The results were _interesting_, showing extreme differences in the run
> times:
>
Can you try the patch:
http://gcc.gnu.org/bugzilla/attachment.cgi?id=13656
in
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=32183
H.J.