RFR: 8305895: Implement JEP 450: Compact Object Headers (Experimental) [v21]

[Stefan Karlsson]

On Thu, 19 Sep 2024 12:35:30 GMT, Coleen Phillimore <coleenp at openjdk.org> wrote:

>> Note that if we go with my KLUT proposal for post-Lilliput (the GC oop iteration improvements), this will not matter anymore and can be simplified to a fixed shift of 10.
>
> Yes, please, not having this code would be really nice.  This is difficult code.

Do you seen any effects of this in anything other than special-crafted micro benchmarks? I wonder if it would be good enough to hard-code this to be 10 for the first integration of Lilliput.

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PR Review Comment: https://git.openjdk.org/jdk/pull/20677#discussion_r1766804699