RFR: 8352675: Support Intel AVX10 converged vector ISA feature detection [v4]

[Vladimir Ivanov]

On Thu, 24 Apr 2025 18:39:04 GMT, Jatin Bhateja <jbhateja at openjdk.org> wrote:

> RegMask is part of opto code, and it may not be accessible to the JVMCI interface

I'm not suggesting to reuse RegMask, but introduce a separate class (e.g., VMFeatures) and embed its instances into Abstract_VM_Version (as `VMFeatures _features` and `VMFeatures _cpu_features`). You can keep all the accessors and bit manipulation logic on `VMFeatures` class. 

JVMCI can still operate on in-memory representation at `Abstract_VM_Version::_features`. But it now needs to query its size (which becomes platform-specific constant).

(BTW all CPU feature constants in `AMD64HotSpotVMConfig` change their meaning. I don't see any usages in JDK code. Should they go away now?)

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PR Comment: https://git.openjdk.org/jdk/pull/24329#issuecomment-2828981702