Integrated: 8265491: Math Signum optimization for x86

[Marcus G K Williams]

On Mon, 19 Apr 2021 23:00:47 GMT, Marcus G K Williams <github.com+168222+mgkwill at openjdk.org> wrote:

> x86 Math.Signum() uses two floating point compares and a copy sign operation involving data movement to gpr and XMM.
> 
> We can optimize to one floating point compare and sign computation in XMM. We observe ~25% performance improvement with this optimization.
> 
> Base:
> 
> Benchmark                       Mode Cnt Score Error Units
> Signum._1_signumFloatTest avgt 5 4.660 ? 0.040 ns/op
> Signum._2_overheadFloat avgt 5 3.314 ? 0.023 ns/op
> Signum._3_signumDoubleTest avgt 5 4.809 ? 0.043 ns/op
> Signum._4_overheadDouble avgt 5 3.313 ? 0.015 ns/op
> 
>  
> Optimized:
> signum intrinsic patch
> 
> Benchmark                       Mode  Cnt  Score   Error  Units
> Signum._1_signumFloatTest       avgt    5  3.769 ? 0.015  ns/op
> Signum._2_overheadFloat         avgt    5  3.312 ? 0.025  ns/op
> Signum._3_signumDoubleTest      avgt    5  3.765 ? 0.005  ns/op
> Signum._4_overheadDouble        avgt    5  3.309 ? 0.010  ns/op
> 
> 
> Signed-off-by: Marcus G K Williams <marcus.williams at intel.com>

This pull request has now been integrated.

Changeset: ff65920c
Author:    Marcus G K Williams <marcus.williams at intel.com>
Committer: Sandhya Viswanathan <sviswanathan at openjdk.org>
URL:       https://git.openjdk.java.net/jdk/commit/ff65920cd17e7e862b182524e2151784e26a079c
Stats:     218 lines in 7 files changed: 212 ins; 1 del; 5 mod

8265491: Math Signum optimization for x86

Reviewed-by: jiefu, jbhateja, neliasso

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PR: https://git.openjdk.java.net/jdk/pull/3581