RFR: 8284960: Integration of JEP 426: Vector API (Fourth Incubator) [v4]

[Jatin Bhateja]

On Thu, 12 May 2022 22:48:26 GMT, Vladimir Ivanov <vlivanov at openjdk.org> wrote:

>> Jatin Bhateja has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   8284960: Review comments resolution.
>
> src/hotspot/cpu/x86/stubGenerator_x86_64.cpp line 7953:
> 
>> 7951:     StubRoutines::x86::_vector_iota_indices = generate_iota_indices("iota_indices");
>> 7952: 
>> 7953:     if (UsePopCountInstruction && VM_Version::supports_avx2() && !VM_Version::supports_avx512_vpopcntdq()) {
> 
> Why is the LUT unconditionally generated? `UsePopCountInstruction` still guides the usages.

LUT should be generated only if UsePopCountInsturction is false and iff target does not support necessary features, AVX512POPCNTDQ (for int/long vectors)  and AVX512_BITALG (for sub-word vectors).  Please refer to following discussion where it was suggested to restrict the scope of flag to only scalar popcount operation. 
https://github.com/openjdk/panama-vector/pull/185#discussion_r847758463

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PR: https://git.openjdk.java.net/jdk/pull/8425