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

[Sandhya Viswanathan]

On Fri, 1 Nov 2024 12:06:27 GMT, Jatin Bhateja <jbhateja 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.

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Marked as reviewed by sviswanathan (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/21821#pullrequestreview-2411015230