RFR: 8338694: x86_64 intrinsic for tanh using libm

[Joe Darcy]

On Wed, 21 Aug 2024 00:25:03 GMT, Srinivas Vamsi Parasa <duke at openjdk.org> wrote:

> The goal of this PR is to implement an x86_64 intrinsic for java.lang.Math.tanh() using libm
> 
> Benchmark (ops/ms) | Stock JDK | Tanh intrinsic | Speedup
> -- | -- | -- | --
> MathBench.tanhDouble | 70900 | 95618 | 1.35x

This PR doesn't include any additional tests. It is often appropriate to add more regression testing when introducing a new implementation of a method.

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PR Comment: https://git.openjdk.org/jdk/pull/20657#issuecomment-2310523202