RFR: 8353572: x86: AMD platforms miss the check for CLWB feature flag [v2]

[Aleksey Shipilev]

On Wed, 9 Apr 2025 17:37:33 GMT, Vladimir Ivanov <vlivanov at openjdk.org> wrote:

>> Aleksey Shipilev 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:
>> 
>>  - More feature flag commonning
>>  - Merge branch 'master' into JDK-8353572-amd-clwb
>>  - Fix
>
> src/hotspot/cpu/x86/vm_version_x86.cpp line 3118:
> 
>> 3116:     // We do not know if these are supported by ZX,
>> 3117:     // so we cannot trust common CPUID bit for it.
>> 3118:     result &= ~CPU_CLWB;
> 
> I'd prefer to completely drop this adjustment, but if you do want to keep it, I'd add an assert (and/or a warning?) to fire when CLWB bit is present on ZX CPUs.

Added assert. Whoever maintains ZX would need to fix that code if CLWB is actually supported.

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PR Review Comment: https://git.openjdk.org/jdk/pull/24385#discussion_r2035908038