RFR: 8367689: Revert removal of several compilation-related vmStructs fields [v2]

[Albert Mingkun Yang]

On Tue, 16 Sep 2025 22:25:08 GMT, Francesco Andreuzzi <fandreuzzi at openjdk.org> wrote:

>> #23782 ([JDK-8315488](https://bugs.openjdk.org/browse/JDK-8315488)) removed several vmStructs fields. A small subset was used in Async-Profiler:
>> 
>> CiEnv* _env
>> CompileTask* _task
>> ciMethod* _method
>> 
>> 
>> I propose a small patch to bring them back. It helps third-party tools in building useful features on the JDK. For example, Async-Profiler uses these fields to display the current method being compiled in a compiler thread.
>
> Francesco Andreuzzi has updated the pull request incrementally with six additional commits since the last revision:
> 
>  - note
>  - nn
>  - nn
>  - cc
>  - nn
>  - nn

src/hotspot/share/runtime/vmStructs.cpp line 670:

> 668:                                                                                                                                      \
> 669:   /**************/                                                                                                                   \
> 670:   /* CI (NOTE: these fields should not be removed, they can be used by external tools) */                                            \

Can you also clarify what "external tools" are in the comment so that when/if those external tools stop using them, we can re-evaluate?

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PR Review Comment: https://git.openjdk.org/jdk/pull/27318#discussion_r2354737188