RFR: 8290322: Optimize Vector.rearrange over byte vectors for AVX512BW targets. [v4]

[Sandhya Viswanathan]

On Fri, 19 Aug 2022 18:55:02 GMT, Jatin Bhateja <jbhateja at openjdk.org> wrote:

>> Hi All,
>> 
>> Currently re-arrange over 512bit bytevector is optimized for targets supporting AVX512_VBMI feature, this patch generates efficient JIT sequence to handle it for AVX512BW targets.  Following performance results with newly added benchmark shows
>> significant speedup.
>> 
>> System:  Intel(R) Xeon(R) Platinum 8280 CPU @ 2.70GHz (CascadeLake 28C 2S)
>> 
>> 
>> Baseline:
>> =========
>> Benchmark                                     (size)   Mode  Cnt      Score   Error   Units
>> RearrangeBytesBenchmark.testRearrangeBytes16     512  thrpt    2  16350.330          ops/ms
>> RearrangeBytesBenchmark.testRearrangeBytes32     512  thrpt    2  15991.346          ops/ms
>> RearrangeBytesBenchmark.testRearrangeBytes64     512  thrpt    2     34.423          ops/ms
>> RearrangeBytesBenchmark.testRearrangeBytes8      512  thrpt    2  10873.348          ops/ms
>> 
>> 
>> With-opt:
>> =========
>> Benchmark                                     (size)   Mode  Cnt      Score   Error   Units
>> RearrangeBytesBenchmark.testRearrangeBytes16     512  thrpt    2  16062.624          ops/ms
>> RearrangeBytesBenchmark.testRearrangeBytes32     512  thrpt    2  16028.494          ops/ms
>> RearrangeBytesBenchmark.testRearrangeBytes64     512  thrpt    2   8741.901          ops/ms
>> RearrangeBytesBenchmark.testRearrangeBytes8      512  thrpt    2  10983.226          ops/ms
>> 
>> 
>> Kindly review and share your feedback.
>> 
>> Best Regards,
>> Jatin
>
> Jatin Bhateja has updated the pull request incrementally with one additional commit since the last revision:
> 
>   8290322: Review comments resolution.

src/hotspot/cpu/x86/c2_MacroAssembler_x86.cpp line 5710:

> 5708:   vpsllq(xtmp2, xtmp1, 0x1, vlen_enc);
> 5709:   evpcmpb(ktmp2, k0, shuffle, xtmp2, Assembler::lt, true, vlen_enc);
> 5710:   kandql(ktmp2, ktmp1, ktmp2);

This sequence could be replaced by:
evpcmpb(ktmp2, ktmp1, shuffle, xtmp2, Assembler::lt, true, vlen_enc);

It could also be further improved to:
evpcmpb(ktmp1, ktmp1, shuffle, xtmp2, Assembler::lt, true, vlen_enc);

Thereby removing the need for ktmp2 altogether.

There are three instances of this in the algorithm.

Rest of the changes look good to me.

-------------

PR: https://git.openjdk.org/jdk/pull/9498