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

[Andrew Haley]

On Thu, 13 Nov 2025 20:41:56 GMT, Dhamoder Nalla <dhanalla at openjdk.org> wrote:

> 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).

src/hotspot/cpu/aarch64/macroAssembler_aarch64_log.cpp line 271:

> 269:     fmovd(rscratch1, v0); // rscratch1 = AS_LONG_BITS(X)
> 270:     lea(rscratch2, ExternalAddress((address)_L_tbl));
> 271:     movz(tmp5, 0x7F);

Comments are needed here.

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PR Review Comment: https://git.openjdk.org/jdk/pull/28306#discussion_r2533464197