RFR: 8370405: C2: mismatched store from MergeStores wrongly scalarized in allocation elimination [v2]

[Emanuel Peter]

On Wed, 29 Oct 2025 17:47:52 GMT, Vladimir Kozlov <kvn at openjdk.org> wrote:

>> Emanuel Peter 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 16 additional commits since the last revision:
>> 
>>  - Merge branch 'master' into JDK-8370405-alloc-elimination-and-MergeStores
>>  - only verify primitive types
>>  - Apply suggestions from code review
>>  - more assert adjustment
>>  - ignore debug flag
>>  - id for tests, and fix up the assert
>>  - pass int for short slot
>>  - another test
>>  - improve test
>>  - wip new IR test
>>  - ... and 6 more: https://git.openjdk.org/jdk/compare/57042cfd...b6e032c2
>
> And I am fine to do that in separate changes.

@vnkozlov I filed this:
[JDK-8370936](https://bugs.openjdk.org/browse/JDK-8370936) C2 MergeStores: move process_for_merge_stores_igvn after allocation elimination

I also fixed the `assert` that Graal would have tripped over, and refactored the code with `#if INCLUDE_JVMCI`.

Update: @merykitty assigned this to himself, thank you!
[JDK-8370901](https://bugs.openjdk.org/browse/JDK-8370901) C2: strenghten assert in create_scalarized_object_description after JDK-8370405

Is there anything else I can improve here?

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PR Comment: https://git.openjdk.org/jdk/pull/27997#issuecomment-3466959188