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[Bug middle-end/44297] Big spec cpu2006 prefetch regressions on gcc 4.6 on x86
- From: "changpeng dot fang at amd dot com" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: 28 May 2010 16:46:58 -0000
- Subject: [Bug middle-end/44297] Big spec cpu2006 prefetch regressions on gcc 4.6 on x86
- References: <bug-44297-18740@http.gcc.gnu.org/bugzilla/>
- Reply-to: gcc-bugzilla at gcc dot gnu dot org
------- Comment #6 from changpeng dot fang at amd dot com 2010-05-28 16:46 -------
(In reply to comment #4)
> Created an attachment (id=20767)
--> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=20767&action=view) [edit]
> Patch that makes loop invariant prefetches backend specfic
>
Actually, I am the one who would like the invariant step prefetch to
be backend independent. However, the current implementation seems a bit
aggressive: The fundamental assumption of the implementation is that
the invariant step is big enough so that there is no spatial reuse
and we don't need to unroll the loop (preprech_mod == 1). This assumption
may be OK for c code (or integer code), and may not be appropriate for
fortran programs.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44297