RFR: 8338694: x86_64 intrinsic for tanh using libm [v6]

[Scott Gibbons]

On Fri, 13 Sep 2024 22:36:45 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
>
> Srinivas Vamsi Parasa has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Update test/jdk/java/lang/Math/HyperbolicTests.java
>   
>   Co-authored-by: Andrey Turbanov <turbanoff at gmail.com>

I hand-verified the code.

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Marked as reviewed by sgibbons (Committer).

PR Review: https://git.openjdk.org/jdk/pull/20657#pullrequestreview-2307159316