[Bug tree-optimization/23619] Missed pre opportunity

[dberlin at dberlin 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.




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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23619