RFR: 8329254: optimize integral reverse operations on x86 GFNI target. [v2]

[Jatin Bhateja]

> - Efficient GFNI based instruction sequence to compute integral reverse operation was added along with JEP-426 (VectorAPI 4th Incubation). https://bugs.openjdk.org/browse/JDK-8284960
> 
> - However, the CPUID based feature detection for GFNI was incorrectly performed under AVX512 check, fixing it shows roughly 2X performance improvement for Integer/Long.reverse APIs on E-core targets (MTL+).
> 
> 
> BaseLine:
> Benchmark              (size)  Mode  Cnt  Score   Error  Units
> Integers.reverse          500  avgt    2  0.120          us/op
> Longs.reverse             500  avgt    2  0.221          us/op
> 
> Withopt:
> Benchmark              (size)  Mode  Cnt  Score   Error  Units
> Integers.reverse          500  avgt    2  0.050          us/op
> Longs.reverse             500  avgt    2  0.086          us/op
> 
> 
> Kindly review.
> 
> Best Regards,
> Jatin

Jatin Bhateja has updated the pull request incrementally with one additional commit since the last revision:

  Review comment resolution.

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/18530/files
  - new: https://git.openjdk.org/jdk/pull/18530/files/08e83564..3f18ba84

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=18530&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=18530&range=00-01

  Stats: 2 lines in 1 file changed: 0 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/18530.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/18530/head:pull/18530

PR: https://git.openjdk.org/jdk/pull/18530