RFR: 8305895: Implement JEP 450: Compact Object Headers (Experimental) [v8]

[Thomas Stuefe]

On Mon, 9 Sep 2024 15:58:29 GMT, Coleen Phillimore <coleenp at openjdk.org> wrote:

>> Roman Kennke has updated the pull request incrementally with two additional commits since the last revision:
>> 
>>  - Try to avoid lea in loadNklass (aarch64)
>>  - Fix release build error
>
> src/hotspot/cpu/aarch64/compressedKlass_aarch64.cpp line 147:
> 
>> 145: #endif
>> 146: 
>> 147:   return true;
> 
> This should only be in the compressedKlass.cpp file.

Okay. I will remove the whole `CompressedKlassPointers::pd_initialize` logic. We only need it for one architecture (aarch) and one case (+UseCCP -UseCOH), so maybe its not worth fanning out across all platforms, including Zero. Instead, I will add a short `ifdef` section to `CompressedKlassPointers::initialize`.

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PR Review Comment: https://git.openjdk.org/jdk/pull/20677#discussion_r1757169570