RFR: 8352675: Support Intel AVX10 converged vector ISA feature detection [v14]

[Quan Anh Mai]

On Tue, 6 May 2025 11:19:54 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 one additional commit since the last revision:
> 
>   build fixes for non-x86 targets

src/hotspot/cpu/x86/vm_version_x86.hpp line 44:

> 42:   // log2 of feature vector element size in bits, used by JVMCI to check enabled feature bits.
> 43:   // Refer HotSpotJVMCIBackendFactory::convertFeaturesVector.
> 44:   static uint32_t _features_vector_element_shift_count;

Making this `static constexpr` helps constant folding, too.

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PR Review Comment: https://git.openjdk.org/jdk/pull/24329#discussion_r2075301116