RFR: 8292898: [vectorapi] Unify vector mask cast operation [v2]

[Quan Anh Mai]

On Thu, 15 Sep 2022 12:16:38 GMT, Jatin Bhateja <jbhateja at openjdk.org> wrote:

>> Xiaohong Gong has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains one commit:
>> 
>>   8292898: [vectorapi] Unify vector mask cast operation
>
> src/hotspot/cpu/x86/c2_MacroAssembler_x86.cpp line 4630:
> 
>> 4628:         } else {
>> 4629:           vpmovsxbw(dst, src, vlen_enc);
>> 4630:         }
> 
> if int/short == 2  and target == AVX512BW:  VPMOVSXBW looks incorrect, expectation is to wide cast each 16 bit lane to 32 bit and not 8 bit to 16 bit.

A mask element of type short can only be 0x0000 or 0xFFFF, in those cases both `vpmovsxbw` and `vpmovsxwd` transform it to 0x00000000 and 0xFFFFFFFF, respectively. The same logic applies to the below circumstances.

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PR: https://git.openjdk.org/jdk/pull/10192