RFR: 8279508: Auto-vectorize Math.round API [v5]

[Jatin Bhateja]

> Summary of changes:
> - Intrinsify Math.round(float) and Math.round(double) APIs.
> - Extend auto-vectorizer to infer vector operations on encountering scalar IR nodes for above intrinsics.
> - Test creation using new IR testing framework.
> 
> Following are the performance number of a JMH micro included with the patch 
> 
> Test System: Intel(R) Xeon(R) Platinum 8380 CPU @ 2.30GHz (Icelake Server)
> 
> 
> Benchmark | TESTSIZE | Baseline AVX3 (ops/ms) | Withopt AVX3 (ops/ms) | Gain ratio | Baseline AVX2 (ops/ms) | Withopt AVX2 (ops/ms) | Gain ratio
> -- | -- | -- | -- | -- | -- | -- | --
> FpRoundingBenchmark.test_round_double | 1024.00 | 584.99 | 1870.70 | 3.20 | 510.35 | 548.60 | 1.07
> FpRoundingBenchmark.test_round_double | 2048.00 | 257.17 | 965.33 | 3.75 | 293.60 | 273.15 | 0.93
> FpRoundingBenchmark.test_round_float | 1024.00 | 825.69 | 3592.54 | 4.35 | 825.32 | 1836.42 | 2.23
> FpRoundingBenchmark.test_round_float | 2048.00 | 388.55 | 1895.77 | 4.88 | 412.31 | 945.82 | 2.29
> 
> 
> Kindly review and share your feedback.
> 
> Best Regards,
> Jatin

Jatin Bhateja has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains seven commits:

 - 8279508: Adding few descriptive comments.
 - Merge branch 'master' of http://github.com/openjdk/jdk into JDK-8279508
 - 8279508: Replacing by efficient instruction sequence based on MXCSR.RC mode.
 - 8279508: Adding vectorized algorithms to match the semantics of rounding operations.
 - Merge branch 'master' of http://github.com/openjdk/jdk into JDK-8279508
 - 8279508: Adding a test for scalar intrinsification.
 - 8279508: Auto-vectorize Math.round API

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Changes: https://git.openjdk.java.net/jdk/pull/7094/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=7094&range=04
  Stats: 739 lines in 23 files changed: 648 ins; 29 del; 62 mod
  Patch: https://git.openjdk.java.net/jdk/pull/7094.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/7094/head:pull/7094

PR: https://git.openjdk.java.net/jdk/pull/7094