RFR: 8347499: C2: Make `PhaseIdealLoop` eliminate more redundant safepoints in loops [v2]

[Emanuel Peter]

On Tue, 18 Mar 2025 03:22:22 GMT, Qizheng Xing <qxing at openjdk.org> wrote:

>> Qizheng Xing has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains three additional commits since the last revision:
>> 
>>  - Merge branch 'master' into enhance-loop-safepoint-elim
>>  - Add IR test and microbench.
>>  - Make `PhaseIdealLoop` eliminate more redundant safepoints in loops.
>
> Hi all,
> 
> This patch has now passed all GHA tests and is ready for further reviews.
> 
> If there are any other suggestions for this PR, please let me know.
> 
> Thanks!

@MaxXSoft I'm not an expert with SafePoints, but I'd be willing to review if you answer my questions above, and maybe some more I'll have later ;)

One question I just had now: Assume we now remove the SafePoint because there is that other call above. But what if later we inline that call - do we still have some SafePoint after that in the loop?

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PR Comment: https://git.openjdk.org/jdk/pull/23057#issuecomment-2732027766