RFR: 8338694: x86_64 intrinsic for tanh using libm

[Andrew Haley]

On 8/27/24 12:13, Jatin Bhateja wrote:
> Hi @vamsi-parasa ,  Kindly also add a JMH micro benchmark, I did a first
>   run and see around 4% performance drop with attached micro on Sapphire
> Rapids.
> [test.txt](https://github.com/user-attachments/files/16761142/test.txt)

If I had to guess, that's because there are no infinities and no NaNs
so HotSpot will perfectly predict .

Given that this "normal" execution is the expected use of tanh(), it
seems to me that this intrinsic won't help in the usual case, and may
make things worse.