RFR(S): 8199784: PhaseIdealLoop::place_near_use() might return wrong control with loop strip mining

[Aleksey Shipilev]

On 03/20/2018 10:25 AM, Roland Westrelin wrote:
> 
> http://cr.openjdk.java.net/~roland/8199784/webrev.00/
> 
> When a Load is sunk out of a loop, if one of the uses is a Phi of a
> strip mined CountedLoop, PhaseIdealLoop::place_near_use() should return
> the entry control of the OuterStripMinedLoop.
> 
> I couldn't write a test case that would trigger this and I'm not even
> sure it's even possible. We're seeing this with some graph patterns that
> are specific to Shenandoah but I think it's better to have this fixed
> anyway.

Yes. Also, the patch in this form was in Shenandoah repos for a while, and survived the testing we
threw on it.

Thanks,
-Aleksey


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