[jdk17] RFR: 8268672: C2: assert(!loop->is_member(u_loop)) failed: can be in outer loop or out of both loops only

[Roland Westrelin]

On Thu, 17 Jun 2021 16:21:59 GMT, Vladimir Kozlov <kvn at openjdk.org> wrote:

>> This is caused by the fix for 8263303 in which I changed the code of
>> loop cloning of a strip mined loop so nodes that are pinned in the
>> outer loop but not referenced by the loop's safepoint are moved out of
>> the loop before cloning:
>> 
>> https://github.com/openjdk/jdk/commit/d4377afb999f4f03d384ded97771c83ea1c1f513#diff-7b82624b78127158abbce6835eeba196bd062aee59512ec2d4e4c8c7d681573bR1980
>> 
>> The assert failure here is caused by a node that has its control input
>> set to the inner loop but is assigned control by PhaseIdealLoop out of
>> the inner loop. The assert fires because the change from 8263303
>> affects the condition that the assert checks. I still think, in
>> principle, the fix from 8263303 is the good one so I propose to simply
>> reorganize the change from 8263303 so the assert doesn't wrongly fire.
>
> Looks good.

@vnkozlov @neliasso thanks for the reviews

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PR: https://git.openjdk.java.net/jdk17/pull/88