RFR: 8305895: Implement JEP 450: Compact Object Headers (Experimental) [v6]

[Chris Plummer]

On Wed, 18 Sep 2024 12:35:28 GMT, Roman Kennke <rkennke at openjdk.org> wrote:

>> Thinking about this a bit more, maybe _mark needs to be a MetadataField rather than CInt. This is a kind of odd situation. Basically we have a CInt field that is more than just simple bits used as flags or small integers. It also gets you to the Klass*. Possibly SA should treat _mark is two separate fields; one that remains a CInt as it currently is and another that treats it as an encoded Klass* like the NarrowKlassField case.
>
> Do you think this needs to be addressed before integration? And if so, could you help with implementation? Or could we do it after intergration? Then please file a follow-up issue.

Ok. I filed [JDK-8340396](https://bugs.openjdk.org/browse/JDK-8340396).

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PR Review Comment: https://git.openjdk.org/jdk/pull/20677#discussion_r1765387764