RFR: 8334629: [BACKOUT] PhaseIdealLoop::conditional_move is too conservative [v2]

[Quan Anh Mai]

On Thu, 20 Jun 2024 13:55:32 GMT, Jasmine Karthikeyan <jkarthikeyan at openjdk.org> wrote:

>> Quan Anh Mai has refreshed the contents of this pull request, and previous commits have been removed. The incremental views will show differences compared to the previous content of the PR. The pull request contains one new commit since the last revision:
>> 
>>   Revert "8319451: PhaseIdealLoop::conditional_move is too conservative"
>>   
>>   This reverts commit ac968c36d7cc2e13270d28c9310178f6b654d7dc.
>
> Ah yep, looking at the log the main IfNode has `P=0.891189`, so it doesn't succeed the new check `prob > 0.18 && prob < 0.82`. I think this is fundementally the same problem as https://github.com/openjdk/jdk/pull/18734, and increasing the number of predetermined elements ([here](https://github.com/openjdk/jdk/blob/master/test/hotspot/jtreg/compiler/c2/irTests/TestIfMinMax.java#L184-L194)) should fix this. If it's important to get this patch in quickly though feel free to problemlist the test or disable the IR verification, I can take a look at it soon.

@jaskarth Thanks for your analysis, I added the test to the problem list and created a relevant issue for it.

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PR Comment: https://git.openjdk.org/jdk/pull/19650#issuecomment-2185673032