Integrated: 8281375: Accelerate bitCount operation for AVX2 and AVX512 target.

[Jatin Bhateja]

On Mon, 7 Feb 2022 20:08:35 GMT, Jatin Bhateja <jbhateja at openjdk.org> wrote:

> Summary of changes:
> 
> - Patch extends existing vectorized bitCount optimization added with [JDK-8278868](https://bugs.openjdk.java.net/browse/JDK-8278868) and emits optimized JIT sequence for AVX2 and other AVX512 targets which do not support avx512_vpopcntdq feature.
> - Since PopCountVI/PopCountVL node emit different instruction sequence based on the target features hence a rudimentary cost mode has been added which influences the SLP unrolling factor to prevent generating bloated main loops.
> - Following are the performance results of an existing [JMH micro](https://github.com/jatin-bhateja/jdk/blob/master/test/micro/org/openjdk/bench/vm/compiler/VectorBitCount.java) over various X86 targets.
> 
> 
> Benchmark | SIZE | Baseline AVX2 (ns/op) | Withopt AVX2 (ns/op) | Gain % | Baseline AVX3 (ns/op) | Withopt AVX3 (ns/op) | Gain % | Baseline AVX3 (VPOPCOUNTDQ) | Withopt AVX3 (VPOCOUNTDQ) | Gain %
> -- | -- | -- | -- | -- | -- | -- | -- | -- | -- | --
> VectorBitCount.WithSuperword.intBitCount | 1024 | 1089.799 | 420.156 | 159.3796114 | 1083.92 | 203.958 | 431.442748 | 88.958 | 60.096 | 48.02649095
> VectorBitCount.WithSuperword.longBitCount | 1024 | 417.458 | 413.859 | 0.869619846 | 417.203 | 214.949 | 94.09394787 | 105.954 | 117.019 | -9.455729411
> 
> Please review and share your feedback.
> 
> Best Regards,
> Jatin

This pull request has now been integrated.

Changeset: fde31498
Author:    Jatin Bhateja <jbhateja at openjdk.org>
URL:       https://git.openjdk.java.net/jdk/commit/fde31498963d76630ada31bd0e0cf3035f87445b
Stats:     271 lines in 16 files changed: 259 ins; 3 del; 9 mod

8281375: Accelerate bitCount operation for AVX2 and AVX512 target.

Reviewed-by: sviswanathan, thartmann

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PR: https://git.openjdk.java.net/jdk/pull/7373