RFR: 8338694: x86_64 intrinsic for tanh using libm [v8]

[Srinivas Vamsi Parasa]

> 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 with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains 12 additional commits since the last revision:

 - update tanh additional tests
 - Merge branch 'master' of https://git.openjdk.java.net/jdk into onetanh
 - Update HyperbolicTests.java
   
   Remove the path to random library
 - update copyright year and remove unused random from HyperbolicTests
 - remove tanh tests in seprate file
 - Update test/jdk/java/lang/Math/HyperbolicTests.java
   
   Co-authored-by: Andrey Turbanov <turbanoff at gmail.com>
 - quad precision tanh tests
 - c1 and template generator fixes
 - update libm tanh reference test with code review suggestions
 - Add stub initialization and extra tanh tests
 - ... and 2 more: https://git.openjdk.org/jdk/compare/7110935c...3664be15

-------------

Changes:
  - all: https://git.openjdk.org/jdk/pull/20657/files
  - new: https://git.openjdk.org/jdk/pull/20657/files/e908eb44..3664be15

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=20657&range=07
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=20657&range=06-07

  Stats: 111889 lines in 2917 files changed: 66503 ins; 28786 del; 16600 mod
  Patch: https://git.openjdk.org/jdk/pull/20657.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/20657/head:pull/20657

PR: https://git.openjdk.org/jdk/pull/20657