RFR: 8327147: optimized implementation of round operation for x86_64 CPUs

Fri Mar 1 21:51:00 UTC 2024

On Fri, 1 Mar 2024 19:11:58 GMT, Srinivas Vamsi Parasa <duke at openjdk.org> wrote:

> The goal of this PR is to provide ~4x faster implementation of Math.ceil, Math.floor and Math.rint for x86_64 CPUs.
> 
> Below is the performance data on an Intel Tiger Lake machine. 
> 
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> 
> Benchmark | Stock JDK   (ops/ms) | This PR (ops/ms) | Speedup
> -- | -- | -- | --
> MathBench.ceilDouble | 547979 | 2170198 | 3.96
> MathBench.floorDouble | 547979 | 2167459 | 3.96
> MathBench.rintDouble | 547962 | 2130499 | 3.89
> 
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src/hotspot/cpu/x86/x86.ad line 3895:

> 3893: 
> 3894: /*
> 3895: instruct roundD_mem(legRegD dst, memory src, immU8 rmode) %{

Don't we want roundD_mem enabled, for both roundsd (UseAVX == 0) and vroundsd (UseAVX > 0)?

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PR Review Comment: https://git.openjdk.org/jdk/pull/18089#discussion_r1509586262