RFR: 8305898: Alternative self-forwarding mechanism

[Roman Kennke]

On Thu, 22 Aug 2024 08:29:38 GMT, Albert Mingkun Yang <ayang at openjdk.org> wrote:

>> Because I'd like self-forwarded marks not to be init-ed. Otherwise we'd have to preserve/restore them. Simply unset_self_forwarded() is enough to get them back to the original state.
>
>> Otherwise we'd have to preserve/restore them.
> 
> OK, then it's incorrect to use `init_mark()` for self-fwd objs.
> 
> This method is for self-fwd objs only. Can we remove the `else if` part? The non-self-fwd objs are essentially dead, right?

I wasn't sure about this. What happens to successfully-promoted objects? Are we sure that no references point to their from-space parts? If yes, then I'd remove the else-if part and place an assert there instead.

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PR Review Comment: https://git.openjdk.org/jdk/pull/20603#discussion_r1726683296