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[Bug tree-optimization/32183] [4.3 Regression] reassoc2 can more extra calculations into a loop
- From: "dberlin at dberlin dot org" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: 5 Jun 2007 00:12:15 -0000
- Subject: [Bug tree-optimization/32183] [4.3 Regression] reassoc2 can more extra calculations into a loop
- References: <bug-32183-682@http.gcc.gnu.org/bugzilla/>
- Reply-to: gcc-bugzilla at gcc dot gnu dot org
------- Comment #27 from dberlin at gcc dot gnu dot org 2007-06-05 00:12 -------
Subject: Re: [4.3 Regression] reassoc2 can more extra calculations into a loop
On 4 Jun 2007 23:35:19 -0000, rakdver at gcc dot gnu dot org
<gcc-bugzilla@gcc.gnu.org> wrote:
>
>
> ------- Comment #26 from rakdver at gcc dot gnu dot org 2007-06-04 23:35 -------
> Created an attachment (id=13656)
--> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=13656&action=view)
> --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=13656&action=view)
> patch preventing reassociation across loop boundaries
>
You may want to turn this on only for reassoc2.
For reassoc1, we get benefit from the identities and linearization it
performs, and PRE will move out what needs to be moved out.
It's only the reassoc after loop opts are being performed that
shouldn't be playing with calculations in loops.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=32183