RFR: 8279508: Auto-vectorize Math.round API [v3]

[Quan Anh Mai]

On Sun, 13 Feb 2022 03:09:43 GMT, Jatin Bhateja <jbhateja at openjdk.org> wrote:

>> Summary of changes:
>> - Intrinsify Math.round(float) and Math.round(double) APIs.
>> - Extend auto-vectorizer to infer vector operations on encountering scalar IR nodes for above intrinsics.
>> - Test creation using new IR testing framework.
>> 
>> Following are the performance number of a JMH micro included with the patch 
>> 
>> Test System: Intel(R) Xeon(R) Platinum 8380 CPU @ 2.30GHz (Icelake Server)
>> 
>> 
>> Benchmark | TESTSIZE | Baseline AVX3 (ops/ms) | Withopt AVX3 (ops/ms) | Gain ratio | Baseline AVX2 (ops/ms) | Withopt AVX2 (ops/ms) | Gain ratio
>> -- | -- | -- | -- | -- | -- | -- | --
>> FpRoundingBenchmark.test_round_double | 1024.00 | 584.99 | 1870.70 | 3.20 | 510.35 | 548.60 | 1.07
>> FpRoundingBenchmark.test_round_double | 2048.00 | 257.17 | 965.33 | 3.75 | 293.60 | 273.15 | 0.93
>> FpRoundingBenchmark.test_round_float | 1024.00 | 825.69 | 3592.54 | 4.35 | 825.32 | 1836.42 | 2.23
>> FpRoundingBenchmark.test_round_float | 2048.00 | 388.55 | 1895.77 | 4.88 | 412.31 | 945.82 | 2.29
>> 
>> 
>> Kindly review and share your feedback.
>> 
>> Best Regards,
>> Jatin
>
> Jatin Bhateja has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains four additional commits since the last revision:
> 
>  - 8279508: Adding vectorized algorithms to match the semantics of rounding operations.
>  - Merge branch 'master' of http://github.com/openjdk/jdk into JDK-8279508
>  - 8279508: Adding a test for scalar intrinsification.
>  - 8279508: Auto-vectorize Math.round API

Also, it seems you have tried using `roundss/sd/ps/pd` followed by a cast to correct the rounding behaviour but decided to take another approach. Some comments around the functions explaining why that is so would be preferable. Thanks.

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PR: https://git.openjdk.java.net/jdk/pull/7094