RFR: 8308776: [AArch64] Math.log is 10% slower than StrictMath.log on aarch64 [v2]

Tue Nov 25 22:23:36 UTC 2025

> This PR Introduces an optimized AArch64 intrinsic for Math.log using reciprocal refinement and a table-driven polynomial.
> Improves throughput for double logarithms while preserving IEEE-754 corner case behavior (±0, subnormals, negatives, NaN).
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> The micro-benchmark results from MathBench and StrictMathBench below show the performance improvement of Math.log:
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> **Before change**
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> Benchmark | Mode | Cnt | Score | Error | Units
> -- | -- | -- | -- | -- | --
> MathBench.logDouble | thrpt | 10 | **15549.705** | ±357.439 | ops/ms
> StrictMathBench.logDouble | thrpt | 10 | 219408.158 | ±16484.680 | ops/ms
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> **After adding Math.log intrinsic**
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> Benchmark | Mode | Cnt | Score | Error | Units
> -- | -- | -- | -- | -- | --
> MathBench.logDouble | thrpt | 10 | **300086.773** | ±6675.936 | ops/ms
> StrictMathBench.logDouble | thrpt | 10 | 226521.817 | ±4038.975 | ops/ms
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Dhamoder Nalla has updated the pull request incrementally with one additional commit since the last revision:

  [AArch64] Math.log is 10% slower than StrictMath.log on aarch64

-------------

Changes:
  - all: https://git.openjdk.org/jdk/pull/28306/files
  - new: https://git.openjdk.org/jdk/pull/28306/files/e8fac776..06b3dd4d

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=28306&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=28306&range=00-01

  Stats: 184 lines in 4 files changed: 66 ins; 114 del; 4 mod
  Patch: https://git.openjdk.org/jdk/pull/28306.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/28306/head:pull/28306

PR: https://git.openjdk.org/jdk/pull/28306