RFR: 8363996: Obsolete UseCompressedClassPointers [v5]

[Thomas Stuefe]

On Tue, 10 Feb 2026 05:40:28 GMT, David Holmes <dholmes at openjdk.org> wrote:

>> Thomas Stuefe has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains 62 commits:
>> 
>>  - Replace Klass::_metadata union with narrowKlass member
>>  - Ivan: fix various instances of ObjLayout::undefined should assert
>>  - Ivan: Update src/hotspot/share/oops/instanceKlass.cpp
>>    
>>    Co-authored-by: Ivan Walulya <ivan.walulya at oracle.com>
>>  - David: reduce diff in ObjectCountEventVerifier.java
>>  - David: minimize change in GetObjectSizeIntrinsicsTest.java
>>  - David: minimize diffs in TestZGCWithCDS.java
>>  - David: minimize diffs for runtime/ErrorHandling/TestVMConfigInHsErrFile.java
>>  - David: revert type change in arguments.cpp
>>  - David: fix comment in metaspace
>>  - Merge branch 'master' into JDK-8363996-Obsolete-UseCompressedClassPointers
>>  - ... and 52 more: https://git.openjdk.org/jdk/compare/ffb6279c...642604ac
>
> A couple of minor follow up comments below, but otherwise this all seems okay. Thanks

@dholmes-ora Thanks for your review. I hope I addressed your issues. You are right, its better to use a compile-time constant; that also pointed me to one or two simplifications that were possible.

I built and tested on x64 and arm32, did a quick test on arm32 to see that 32-bit comes up and runs.

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PR Comment: https://git.openjdk.org/jdk/pull/28366#issuecomment-3877067086