RFR: 8334342: Add MergeStore JMH benchmarks [v7]

[Emanuel Peter]

On Wed, 24 Jul 2024 16:00:10 GMT, Shaojin Wen <duke at openjdk.org> wrote:

>> [8318446](https://github.com/openjdk/jdk/pull/16245)  brings MergeStore. We need a JMH Benchmark to evaluate the performance of various batch operations and the effect of MergeStore.
>
> Shaojin Wen 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 remote-tracking branch 'upstream/master' into merge_store_bench
>  - move to vm.compiler
>  - Merge remote-tracking branch 'upstream/master' into merge_store_bench
>  - Merge remote-tracking branch 'upstream/master' into merge_store_bench
>  - bug fix for `putChars4C`
>  - bug fix for `putChars4C` and `putChars4S`
>  - use VarHandler CHAR_L & CHAR_B
>  - copyright
>  - bug fix for putIntBU
>  - add cases for `getChar` & `putChar`
>  - ... and 6 more: https://git.openjdk.org/jdk/compare/1669617e...d00654ff

Looks good to me. Thanks for creating this benchmark! I'll definitely use it soon, when I try to extend MergeStores to more cases :)

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Marked as reviewed by epeter (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/19734#pullrequestreview-2198398556