RFR: 8347499: C2: Make `PhaseIdealLoop` eliminate more redundant safepoints in loops [v3]

[Roland Westrelin]

On Wed, 29 Oct 2025 08:59:28 GMT, Qizheng Xing <qxing at openjdk.org> wrote:

>> It would be nice to make sure all cases here have an IR test which is not the case AFAICT. Can you open a JBS issue for that?
>
> @rwestrel @eme64 Do IR tests in `TestRedundantSafepointElimination.java` in this patch cover all these cases? Specifically:
> 
> * Case A: `testTopLevelCountedLoop`, `testTopLevelCountedLoopWithDomCall`
> * Case B: tests containing nested loops
> * Case C: `testOuterLoopWithDomCall`
> * Case D: `testOuterLoopWithLocalNonCallSafepoint`
> * Case E: `testLoopNeedsToPreserveSafepoint`

I didn't realize case E was covered. Good then.

-------------

PR Review Comment: https://git.openjdk.org/jdk/pull/23057#discussion_r2482066789