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

[Kevin Walls]

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

We should clarify:
These fields are not a public interface, but the JVM has to maintain them around due to other software's expectation?

Async-Profiler is great, but is this change the right solution? Are there other fields which other software would have liked to stay around, and what else can not be removed?

Curious how did Async-Profiler break when these are removed?  Is it a crash that Async-Profiler needs to workaround, or is there less information in the collected profile.

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PR Comment: https://git.openjdk.org/jdk/pull/27318#issuecomment-3302169803