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[Bug tree-optimization/23619] Missed pre opportunity
- From: "dberlin at dberlin dot org" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: 29 Aug 2005 15:15:42 -0000
- Subject: [Bug tree-optimization/23619] Missed pre opportunity
- References: <20050829090219.23619.rakdver@gcc.gnu.org>
- Reply-to: gcc-bugzilla at gcc dot gnu dot org
------- Additional Comments From dberlin at gcc dot gnu dot org 2005-08-29 15:15 -------
Subject: Re: Missed pre opportunity
On Mon, 2005-08-29 at 12:46 +0000, rakdver at gcc dot gnu dot org wrote:
> ------- Additional Comments From rakdver at gcc dot gnu dot org 2005-08-29 12:46 -------
> Is it really a duplicate? I think that in 23286, VUSE at ii may be the problem;
> but in this testcase, there is nothing that can prevent p+q from being moved out
> of loop. Also, in the expression p + q is partially redundant over the back
> edge of the loop, so PRE should work for it.
>
Disabling reassoc, it knows that p + q is antic over the backedge.
Which means it knows it *could* insert it.
Why it's deciding not to do an insert is what i'm analyzing now.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23619