RFR: 8350753: Deprecate UseCompressedClassPointers [v2]

[David Holmes]

On Sun, 6 Apr 2025 09:08:34 GMT, Thomas Stuefe <stuefe at openjdk.org> wrote:

>> Deprecates UseCompressedClassPointers. For the lengthy description of why and how we do this, please read the lengthy [CSR](https://bugs.openjdk.org/browse/JDK-8350754).
>> 
>> Testing:
>> 
>> I ran all jtreg tests manually on Linux-x64 that used the flag in some form (55 tests) to ensure they don't trip over the added deprecation output.
>> 
>> I also tested the JVM on arm32 to verify that UseCompressedClassPointers had never been available there, and that we don't start printing a confusing deprecation message now.
>
> Thomas Stuefe has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains three additional commits since the last revision:
> 
>  - Merge branch 'openjdk:master' into JDK-8350753-Deprecate-UseCompressedClassPointers
>  - not on 32-bit
>  - Deprecate UseCompressedClassPointers

Changes requested by dholmes (Reviewer).

src/hotspot/share/runtime/arguments.cpp line 532:

> 530:   { "CreateMinidumpOnCrash",        JDK_Version::jdk(9),  JDK_Version::undefined(), JDK_Version::undefined() },
> 531: #ifdef _LP64
> 532:   // Note: on 32-bit, the option is not available; therefore a deprecation notice makes no sense.

No need for the comment - the ifdef tells you this is something only for 64-bit

src/hotspot/share/runtime/arguments.cpp line 533:

> 531: #ifdef _LP64
> 532:   // Note: on 32-bit, the option is not available; therefore a deprecation notice makes no sense.
> 533:   { "UseCompressedClassPointers",   JDK_Version::jdk(25),  JDK_Version::jdk(26), JDK_Version::undefined() },

This is in the wrong section - this is not an aliased flag

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PR Review: https://git.openjdk.org/jdk/pull/24436#pullrequestreview-2745627858
PR Review Comment: https://git.openjdk.org/jdk/pull/24436#discussion_r2030522933
PR Review Comment: https://git.openjdk.org/jdk/pull/24436#discussion_r2030524880