RFR: 8343419: Assertion failure in long vector unsigned min/max with -XX:+UseKNLSetting

[Jatin Bhateja]

On Sat, 2 Nov 2024 00:08:21 GMT, Sandhya Viswanathan <sviswanathan at openjdk.org> wrote:

>> KNL only supports AVX512F but not AVX512VL feature, thus vector operations with vector size less than or equal to 256 bits are generally emulated using AVX2 instructions.
>> 
>> This bugfix patch covers the following scenarios for LongVector unsigned min/ max over KNL targets:-
>> 1.   Long species < 512 bits and non-predicated operation.
>>        - Operate at full vector width of 512 bits using VPMINUQ/VPMAXUQ instructions.
>> 2.  Long species < 512 bits with memory operands and non-predicated operations.
>>        -  Load memory into exactly matching vector size.
>>        - Operate at full vector width of 512 bits
>> 3.  Long species < 512 bits and predicated operation.
>>        - Emulate operation using AVX2 instructions 
>>        - Blend the result with the first source vector using the predication mask.
>>        - Existing opmask population mechanism expects the existence of AVX512BW/DQ features missing on KNL target.
>> 4. Long species  == 512 bits,  both predicated and non-predicated operations.
>>     - Directly uses 512  bits VPMINUQ/VPMAXUQ instructions.
>> 
>> All existing jtreg regressions are passing with -XX:+UseKNLSetting and -Xcomp flags.
>> 
>> Kindly review.
>> 
>> Best Regards,
>> Jatin
>
> Looks good to me.

Thanks @sviswa7

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PR Comment: https://git.openjdk.org/jdk/pull/21821#issuecomment-2452777794