RFR: 8352675: Support Intel AVX10 converged vector ISA feature detection [v15]

[Yudi Zheng]

On Wed, 7 May 2025 11:40:05 GMT, Jatin Bhateja <jbhateja at openjdk.org> wrote:

>> - Intel AVX10[1] extends and enhances the capabilities of Intel AVX-512 to benefit all Intel® products and will be the vector ISA of choice moving into the future. 
>> - It supports a new ISA versioning scheme which simplifies the existing AVX512 feature enumeration scheme. Feature set supported by an AVX10 ISA version will be supported by all the versions above it.
>> - The initial, fully-featured version of Intel® AVX10 will be enumerated as Version 2 (denoted as Intel® AVX10.2). This will include the new ISA extension over the existing AVX512 instructions. 
>> - An early version of Intel® AVX10 (Version 1, or Intel® AVX10.1) that only enumerates the Intel® AVX-512 instruction set at 128, 256, and 512 bits will be enabled on the Granite Rapids Server for software pre-enabling.
>> 
>> This patch adds the necessary CPUID feature detection for AVX10 ISA version 1 and 2.  In terms of architectural state save restoration, AVX10 is isomorphic to AVX512 support up till Granite Rapids. State components affected by AVX10 extension include SSE, AVX, Opmask, ZMM_Hi256, and Hi16_ZMM registers. 
>> 
>> The patch has been regressed through tier1 and jvmci tests 
>> 
>> Please review and share your feedback.
>> 
>> Best Regards,
>> Jatin
>> 
>> [1] https://www.intel.com/content/www/us/en/content-details/844829/intel-advanced-vector-extensions-10-2-intel-avx10-2-architecture-specification.html
>
> Jatin Bhateja has updated the pull request incrementally with two additional commits since the last revision:
> 
>  - Making _features_bitmap size configurable
>  - cleanups & refactorings

JVMCI changes look good. Will run some Graal tests on this PR

src/jdk.internal.vm.ci/share/classes/jdk/vm/ci/hotspot/HotSpotJVMCIBackendFactory.java line 121:

> 119:                     long featureIndex = bitIndex >>> featuresElementShiftCount;
> 120:                     long featureBitMask = 1L << (bitIndex & featuresElementMask);
> 121:                     assert featureIndex < featuresBitMapSize;

`featuresBitMapSize` is size in bytes while `featureIndex` is index to long array

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PR Review: https://git.openjdk.org/jdk/pull/24329#pullrequestreview-2822266780
PR Review Comment: https://git.openjdk.org/jdk/pull/24329#discussion_r2077922290