RFR: 8316694: Implement relocation of nmethod within CodeCache [v3]

[Dean Long]

On Fri, 30 May 2025 00:13:45 GMT, Vladimir Kozlov <kvn at openjdk.org> wrote:

>> @dean-long @vnkozlov I added `IMMUTABLE_DATA_REFERENCES` ([source](https://github.com/chadrako/jdk/blob/c5ff58f4e22cbbcdbe06997efe482f73fcee73f5/src/hotspot/share/code/nmethod.hpp#L577-L582)) to make the code more readable. Is that sufficient or would you like to see a struct to represent this instead?
>
> The more I look on it the more I like Dean's idea. I am withdrawing my previous objection.
> Let's have a  **NOT virtual** class similar to CodeBlob.
> Consider moving associated `*_offset` fields from `nmethod` to new class.

@vnkozlov , when I first proposed this [1], you had a concern about Leyden.  Is it still a concern?
[1] https://github.com/openjdk/jdk/pull/21276#discussion_r1853211488

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PR Review Comment: https://git.openjdk.org/jdk/pull/23573#discussion_r2114957912