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

Fri Mar 1 19:17:12 UTC 2024

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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Commit messages:
 - 8327147: optimized implementation of round operation for x86_64 CPUs

Changes: https://git.openjdk.org/jdk/pull/18089/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=18089&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8327147
  Stats: 14 lines in 1 file changed: 14 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/18089.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/18089/head:pull/18089

PR: https://git.openjdk.org/jdk/pull/18089