RFR: 8289186: Support predicated vector load/store operations over X86 AVX2 targets.

[Jatin Bhateja]

Hi All,

[JDK-8283667](https://bugs.openjdk.org/browse/JDK-8283667) added the support to handle masked loads on non-predicated targets by blending the loaded contents with zero vector iff unmasked portion of load does not span beyond array bounds.

X86 AVX2 offers direct predicated vector loads/store instruction for non-sub word type.

This patch adds the efficient backend implementation for predicated memory operations over int/long/float/double vectors.

Please find below the JMH micro stats with and without patch.



System : Intel(R) Xeon(R) Platinum 8280 CPU @ 2.70GHz [28C 2S Cascadelake Server]

Baseline:
Benchmark                                          (inSize)  (outSize)   Mode  Cnt    Score   Error   Units
LoadMaskedIOOBEBenchmark.byteLoadArrayMaskIOOBE        1026       1152  thrpt    2  712.218          ops/ms
LoadMaskedIOOBEBenchmark.doubleLoadArrayMaskIOOBE      1026       1152  thrpt    2  156.912          ops/ms
LoadMaskedIOOBEBenchmark.floatLoadArrayMaskIOOBE       1026       1152  thrpt    2  255.814          ops/ms
LoadMaskedIOOBEBenchmark.intLoadArrayMaskIOOBE         1026       1152  thrpt    2  267.688          ops/ms
LoadMaskedIOOBEBenchmark.longLoadArrayMaskIOOBE        1026       1152  thrpt    2  140.957          ops/ms
LoadMaskedIOOBEBenchmark.shortLoadArrayMaskIOOBE       1026       1152  thrpt    2  474.009          ops/ms


With Opt:
Benchmark                                          (inSize)  (outSize)   Mode  Cnt     Score   Error   Units
LoadMaskedIOOBEBenchmark.byteLoadArrayMaskIOOBE        1026       1152  thrpt    2   742.781          ops/ms
LoadMaskedIOOBEBenchmark.doubleLoadArrayMaskIOOBE      1026       1152  thrpt    2  1241.021          ops/ms
LoadMaskedIOOBEBenchmark.floatLoadArrayMaskIOOBE       1026       1152  thrpt    2  2333.311          ops/ms
LoadMaskedIOOBEBenchmark.intLoadArrayMaskIOOBE         1026       1152  thrpt    2  3258.754          ops/ms
LoadMaskedIOOBEBenchmark.longLoadArrayMaskIOOBE        1026       1152  thrpt    2  1757.192          ops/ms
LoadMaskedIOOBEBenchmark.shortLoadArrayMaskIOOBE       1026       1152  thrpt    2   472.590          ops/ms


Predicated memory operation over sub-word type will be handled in a subsequent patch. 

Kindly review and share your feedback.

Best Regards,
Jatin

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

Commit messages:
 - 8289186: Support predicated vector load/store operations over X86 AVX2 targets.

Changes: https://git.openjdk.org/jdk/pull/9324/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=9324&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8289186
  Stats: 226 lines in 15 files changed: 180 ins; 38 del; 8 mod
  Patch: https://git.openjdk.org/jdk/pull/9324.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/9324/head:pull/9324

PR: https://git.openjdk.org/jdk/pull/9324