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

[Sandhya Viswanathan]

On Fri, 13 Sep 2024 22:30:25 GMT, Srinivas Vamsi Parasa <duke 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?
>
> Hi Joe (@jddarcy),
> 
> As suggested by Sandhya (@sviswa7), I added ~750 fixed point tests for tanh in `TanhTests.java` using the quad precision tanh implementation in libquadmath library from gcc. 
> 
> Please let me know if this looks good.

@vamsi-parasa In my thoughts the best way to do this is add the additional tests points to HyperbolicTests.java itself in the testcases array of testTanh() method. We should remove all the other changes from HyperbolicTests.java. Also no need for separate TanhTests.java file.

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PR Review Comment: https://git.openjdk.org/jdk/pull/20657#discussion_r1759602199