RFR: 8343218: Disable allocating interface and abstract classes in non-class metaspace [v2]

[Coleen Phillimore]

On Wed, 30 Oct 2024 07:09:31 GMT, Thomas Stuefe <stuefe at openjdk.org> wrote:

> So this is just disabling [JDK-8338526](https://bugs.openjdk.org/browse/JDK-8338526) until other C2 changes are in place. Are they coming soon? If not shouldn't [JDK-8338526](https://bugs.openjdk.org/browse/JDK-8338526) be backed out?

The changes for JDK-8338526 were minor refactoring and then there were nice follow up changes to test if klass pointers were encodable, as Thomas said above. The refactoring doesn't hurt anything and setting this way allows the opportunity for a comment explaining why, so we can repeat this change in the future.

> FTR, I had a look at [JDK-8343206](https://bugs.openjdk.org/browse/JDK-8343206) and I don't think it's an issue in current code.

Thank you Tobias for looking at this.  I'll answer in the bug report but I would feel better if the c2 code hit an assert or something if we tried to encode a Klass pointer that isn't in class-metaspace, so I think we should have my change to disable the allocation for now.

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PR Comment: https://git.openjdk.org/jdk/pull/21769#issuecomment-2446901596