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From: "rguenth at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug middle-end/47298] -O3 destroys beautifully vectorized code obtained at -O2
Date: Thu, 05 Jul 2012 10:10:00 -0000	[thread overview]
Message-ID: <bug-47298-4-htOUY4YQMf@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-47298-4@http.gcc.gnu.org/bugzilla/>

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=47298

--- Comment #9 from Richard Guenther <rguenth at gcc dot gnu.org> 2012-07-05 10:10:28 UTC ---
I have a few patches that try to estimate CSE opportunities exposed by
complete unrolling.  In this case the CSE opportunity is the reduction
into C(i,j) (possibly also detected by store motion later).

Adding a patch to enable disabling of cunrolli (and cunroll - which you
also cannot disable) would be fine, but we should keep "unrolling"
once rolling loops early at least.

Note that we should still try to fix

"(and are not good at seeing we run at most once there)"

so we avoid messing up things here.  In theory the vectorizer should be
fully capable of vectorizing even the unrolled loop (in this particular
case) via SLP or basic-block vectorization.


  parent reply	other threads:[~2012-07-05 10:10 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2011-01-14 20:53 [Bug middle-end/47298] New: " Joost.VandeVondele at pci dot uzh.ch
2011-01-14 21:02 ` [Bug middle-end/47298] " rguenth at gcc dot gnu.org
2011-01-14 21:11 ` Joost.VandeVondele at pci dot uzh.ch
2011-01-14 21:27 ` Joost.VandeVondele at pci dot uzh.ch
2012-06-29 14:44 ` Joost.VandeVondele at mat dot ethz.ch
2012-06-29 15:01 ` rguenth at gcc dot gnu.org
2012-07-05  7:36 ` ebotcazou at gcc dot gnu.org
2012-07-05  8:38 ` rguenth at gcc dot gnu.org
2012-07-05  8:48 ` ebotcazou at gcc dot gnu.org
2012-07-05 10:10 ` rguenth at gcc dot gnu.org [this message]
2012-07-05 10:12 ` rguenth at gcc dot gnu.org
2012-07-05 10:30 ` ebotcazou at gcc dot gnu.org
2013-03-27 13:02 ` rguenth at gcc dot gnu.org

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