RFR: 8366424: Missing type profiling in generated Record Object methods [v2]

[Chen Liang]

On Mon, 20 Oct 2025 21:09:45 GMT, Chen Liang <liach at openjdk.org> wrote:

>> Hotspot profiles by bytecode; as a result, some shared methods become polluted and suffer in type profiling, as described in depth in [this essay](https://cr.openjdk.org/~jrose/jvm/equals-profile.html) by John Rose. The record methods generated by `ObjectMethods::bootstrap` just proved itself another victim in this RFE.
>> 
>> To bypass this issue, I naively generated distinct bytecode to allow distinct profiles for now. If hotspot adds any kind of split profiles exposed via internal APIs, we can migrate to such split profile and throw away these extra copies of bytecode.
>> 
>> In particular, in a method handle tree, each leaf method handle seems not separately profiled - for example, all DMH to Object.hashCode share the same profile regardless of their position in a MH tree, making MH trees less useful than explicitly rolled bytecode, unfortunately.
>> 
>> The attached benchmark should be a good demonstration of the effect of type profiling.
>
> Chen Liang 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 seven additional commits since the last revision:
> 
>  - Extract method type desc
>  - Reviews
>  - Merge branch 'master' of https://github.com/openjdk/jdk into fix/object-methods-profile
>  - Merge branch 'master' of https://github.com/openjdk/jdk into fix/object-methods-profile
>  - Improve bench, add comment
>  - Fix profiling issue with record shared code
>  - Unsuccessful attempt to fix record regression

Reran tier1-3.

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PR Comment: https://git.openjdk.org/jdk/pull/27533#issuecomment-3424134705