RFR: 8338694: x86_64 intrinsic for tanh using libm [v2]

[Srinivas Vamsi Parasa]

On Wed, 11 Sep 2024 17:21:36 GMT, Sandhya Viswanathan <sviswanathan at openjdk.org> wrote:

>> So far, this will be the only intrinsic implementation of tanh. Therefore, at the moment it is just checking the consistency of the intrinsic implementation with StrictMath/FDLIBM tanh. If the intrinsic has a ~1 ulp accuracy, it would be expected to often be within 2.5 ulps of FDLIBM tanh. However, as written the regression test would not necessarily pass against any allowable Math.tanh implementation, which is the usual criteria for java.lang.Math tests that aren't otherwise constrained (such as by being limited to a given subset of platforms).
>> 
>> If there was a correctly rounded tanh to compare against, then this style of testing would be valid.
>> 
>> Are there any plan to intrinsify sinh or cosh?
>
> I think instead of random we should generate offline additional correctly rounded fixed test points to cater to new algorithm using high precision arithmetic library and then simply extend the HyperbolicTests.java with these new fixed test points using existing ulp testing mechanism in the test.

Thank you Sandhya(@sviswa7) for the suggestion! Will update the existing HyperbolicTests.java with new fixed point tests with quad precision reference values.

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PR Review Comment: https://git.openjdk.org/jdk/pull/20657#discussion_r1755258108