RFR: 8338694: x86_64 intrinsic for tanh using libm [v3]

[Sandhya Viswanathan]

On Fri, 6 Sep 2024 21:15:07 GMT, Sandhya Viswanathan <sviswanathan at openjdk.org> wrote:

>> @vamsi-parasa  don't hesitate in adding as much and explicit information about the original source from where the algorithm has been picked up, even though the PR explicitly mentions libm. Adding the link to source references is a good practice.
>
> @jatin-bhateja This is based on Intel internal LIBM sources and so there is no public link available.

> Do you have a copy of this information? Should it be in the commit?

@theRealAph The accuracy of standard (non fast mode) LIBM functions ensures errors of < 1 ulp. LIBM is part of Intel C++ compiler. The documentation can be found here: https://www.intel.com/content/www/us/en/docs/cpp-compiler/developer-guide-reference/2021-8/programming-tradeoffs-floating-point-applications.html.

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PR Review Comment: https://git.openjdk.org/jdk/pull/20657#discussion_r1747742612