RFR: 8305895: Implement JEP 450: Compact Object Headers (Experimental) [v26]

[Roberto Castañeda Lozano]

On Fri, 13 Sep 2024 06:43:34 GMT, Roberto Castañeda Lozano <rcastanedalo at openjdk.org> wrote:

>> I don't remember if this change was a reaction to an error or if I just guarded `CompressedKlassPointers::shift()` with +UseCCP because that is the prerequisite now. Probably the latter. I can remove this. Probably should assert then for +UseCCP.
>
> I see, thanks. In that case, I would suggest removing the explicit `UseCompressedClassPointers` test, since it should be implied by `t->isa_narrowklass()`. `check_init()` within `CompressedKlassPointers::shift()` would already fail for the unexpected case where `t->isa_narrowklass() && !UseCompressedClassPointers`, no?

I think it would be good to remove the explicit `UseCompressedClassPointers` test as argued above (i.e. revert this change), unless there is any other reason to keep it that I am missing out?

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PR Review Comment: https://git.openjdk.org/jdk/pull/20677#discussion_r1775277784