RFR: 8351414: C2: MergeStores must happen after RangeCheck smearing

[Quan Anh Mai]

On Fri, 7 Mar 2025 15:07:37 GMT, Emanuel Peter <epeter at openjdk.org> wrote:

> With [JDK-8348959](https://bugs.openjdk.org/browse/JDK-8348959) we see that there can be some issues when RangeCheck smearing happens in the same IGVN phase as MergeStores. It means that some RangeChecks are still around as we do MergeStores, and then we cannot merge as many stores as we would like. We should ensure that RangeCheck smearing happens during post-loop-opts, and then MergeStores happens in a separate dedicated IGVN round afterwards.

Thanks for the elaboration. LGTM.

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Marked as reviewed by qamai (Committer).

PR Review: https://git.openjdk.org/jdk/pull/23944#pullrequestreview-2670878613