Re: middle-end/7561: Prefetch merging code in gcc-3.1/gcc/loop.c incorect

[Janis Johnson <janis187@us.ibm.com>]

The following reply was made to PR middle-end/7561; it has been noted by GNATS.

From: Janis Johnson <janis187@us.ibm.com>
To: redmond@ecf.utoronto.ca
Cc: gcc-gnats@gcc.gnu.org
Subject: Re: middle-end/7561: Prefetch merging code in gcc-3.1/gcc/loop.c incorect
Date: Wed, 14 Aug 2002 09:46:02 -0700

 On Fri, Aug 09, 2002 at 05:58:32PM -0000, redmond@ecf.utoronto.ca wrote:
 > 
 > >Number:         7561
 > >Category:       middle-end
 > >Synopsis:       Prefetch merging code in gcc-3.1/gcc/loop.c incorect
 
 Wow, someone is looking at the prefetch optimization code!  I'm still
 catching up on mailing lists after a two-week vacation and didn't see
 your bug report until just now.
 
 In June I posted some changes to the way the prefetches are merged, and
 changed things in general to handle "sparse" prefetches, for which we
 prefetch only the cache lines containing data that will be used rather
 than every cache line within the section of the array being used.  I had
 asked Jan Hubicka to take a look at it, but that was when he was in the
 middle of lots of other things and I never heard anything from him.
 
 If you're interested in this optimization, please take a look at
 http://gcc.gnu.org/ml/gcc-patches/2002-06/msg00660.html.
 I can update the patch to apply to the current CVS tree, which I've been
 meaning to do anyway; I've been distracted by other things lately.  I've
 also got some other tweaks locally that help some of the SPEC CPU2000
 floating point tests.  The new code as written can't be used because
 it's much slower, but it's meant to demonstrate changes to how
 prefetches are used; once that looks OK it can be changed to do the
 same work more quickly.
 
 Janis Johnson
 IBM Linux Technology Center