RFR: 8303511: C2: assert(get_ctrl(n) == cle_out) during unrolling [v2]

[Tobias Hartmann]

On Fri, 3 Mar 2023 13:50:40 GMT, Roland Westrelin <roland at openjdk.org> wrote:

>> In the same round of loop optimizations:
>> 
>> - `PhaseIdealLoop::remix_address_expressions()` creates a new `AddP`
>>   out of loop. It sets it control to
>>   `n_loop->_head->in(LoopNode::EntryControl)` which, because the loop is
>>   strip mined, is an `OuterStripMinedLoop`.
>>   
>> - The `LoadI` for that `AddP` is found to only have uses outside the
>>   loop and is cloned out of the loop. It's referenced by the outer
>>   loop's safepoint.
>>   
>> - The loop is unrolled. Unrolling follows the safepoint's inputs and
>>   find the new `AddP` with control set to the `OuterStripMinedLoop`
>>   and the assert fires.
>>   
>> No control should be set to an `OuterStripMinedLoop`. The fix is
>> straightforward and sets the control to the `OuterStripMinedLoop`
>> entry control.
>
> Roland Westrelin has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Update test/hotspot/jtreg/compiler/loopstripmining/TestAddPAtOuterLoopHead.java
>   
>   Co-authored-by: Andrey Turbanov <turbanoff at gmail.com>

Looks good to me.

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Marked as reviewed by thartmann (Reviewer).

PR: https://git.openjdk.org/jdk/pull/12824