RFR: 8334629: [BACKOUT] PhaseIdealLoop::conditional_move is too conservative [v3]

[Tobias Hartmann]

On Mon, 24 Jun 2024 06:00:39 GMT, Quan Anh Mai <qamai at openjdk.org> wrote:

>> Hi,
>> 
>> I cannot explain the regression, comparing the current mainline to JDK-21 reveals a decrease in performance, yet it is only for some combinations of OS-GC and perfasm shows that the hot regions (>99% of execution time) do not contain differences that can explain the results.
>> 
>> Consequently, with the advice of @TobiHartmann , I propose to effectively revert JDK-8319451 for the generation of `CMove`s inside loops. For those outside, the before-JDK-8319451 probability threshold is 0.001 and the current value is 0.01. I think the current value is more reasonable as evidenced by the benchmark added in JDK-8319451.
>> 
>> Please kindly review, thank you very much.
>> Quan Anh
>
> Quan Anh Mai has updated the pull request incrementally with one additional commit since the last revision:
> 
>   ProblemList

Looks good to me too.

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Marked as reviewed by thartmann (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/19650#pullrequestreview-2135623293