RFR: 8302906: AArch64: Add SVE backend support for vector unsigned comparison [v2]

[changpeng1997]

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> This patch implements unsigned vector comparison on SVE.
> 
> 1: Test:
> All vector API test cases[1][2] passed without new failure. Existing test cases can cover all unsigned comparison conditions for all kinds of vector.
> 
> 2: Performance:
> (1): Benchmark:
> As existing benchmarks in panama repo (such as [3]) have some issues [4] (We will fix them in a separate patch.), I collected performance data with a reduced jmh benchmark [5]. e.g. for ByteVector unsigned comparison:
> 
> 
> @Benchmark
>     public void byteVectorUnsignedCompare() {
>         for (int j = 0; j < 200; j++) {
>             for (int i = 0; i < bspecies.length(); i++) {
>                 ByteVector av = ByteVector.fromArray(bspecies, ba, i);
>                 ByteVector ca = ByteVector.fromArray(bspecies, bb, i);
>                 av.compare(VectorOperators.UNSIGNED_GT, ca).intoArray(br, i);
>             }
>         }
>     }
> 
> 
> (2): Performance data
> 
> Before:
> 
> 
> Benchmark                               Score(op/ms)     Error
> ByteVector.UNSIGNED_GT#size(1024)       4.846            3.419
> ShortVector.UNSIGNED_GE#size(1024)      3.055            1.369
> IntVector.UNSIGNED_LT#size(1024)        3.475            1.269
> LongVector.UNSIGNED_LE#size(1024)       4.515            1.812
> 
> 
> After:
> 
> 
> Benchmark                               Score(op/ms)     Error
> ByteVector.UNSIGNED_GT#size(1024)       493.937          1.389
> ShortVector.UNSIGNED_GE#size(1024)      5308.796         20.557
> IntVector.UNSIGNED_LT#size(1024)        4944.744         10.606
> LongVector.UNSIGNED_LE#size(1024)       8459.605         28.683
> 
> 
> [1] https://github.com/openjdk/jdk/tree/master/test/jdk/jdk/incubator/vector
> [2] https://github.com/openjdk/jdk/tree/master/test/hotspot/jtreg/compiler/vectorapi
> [3] https://github.com/openjdk/panama-vector/blob/2aade73adeabdf6a924136b17fd96ccc95c1d160/test/micro/org/openjdk/bench/jdk/incubator/vector/operation/ByteMaxVector.java#L1459
> [4] https://bugs.openjdk.org/browse/JDK-8282850
> [5] https://gist.github.com/changpeng1997/d311127e1015c107197f9b56a92b0fae

changpeng1997 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 two additional commits since the last revision:

 - Merge branch 'openjdk:master' into sve_cmpU
 - 8302906: AArch64: Add SVE backend support for vector unsigned comparison
   
   This patch implements unsigned vector comparison on SVE.
   
   1: Test:
   All vector API test cases[1][2] passed without new failure. Existing
   test cases can cover all unsigned comparison conditions for all
   kinds of vector.
   
   2: Performance:
   (1): Benchmark:
   As existing benchmarks in panama repo (such as [3]) have some
   issues [4] (We will fix them in a separate patch.), I collected
   performance data with a reduced jmh benchmark [5]. e.g. for
   ByteVector unsigned comparison:
   
   ```
   @Benchmark
       public void byteVectorUnsignedCompare() {
           for (int j = 0; j < 200; j++) {
               for (int i = 0; i < bspecies.length(); i++) {
                   ByteVector av = ByteVector.fromArray(bspecies, ba, i);
                   ByteVector ca = ByteVector.fromArray(bspecies, bb, i);
                   av.compare(VectorOperators.UNSIGNED_GT, ca).intoArray(br, i);
               }
           }
       }
   ```
   
   (2): Performance data
   
   Before:
   
   ```
   Benchmark                               Score(op/ms)     Error
   ByteVector.UNSIGNED_GT#size(1024)       4.846            3.419
   ShortVector.UNSIGNED_GE#size(1024)      3.055            1.369
   IntVector.UNSIGNED_LT#size(1024)        3.475            1.269
   LongVector.UNSIGNED_LE#size(1024)       4.515            1.812
   ```
   
   After:
   
   ```
   Benchmark                               Score(op/ms)     Error
   ByteVector.UNSIGNED_GT#size(1024)       493.937          1.389
   ShortVector.UNSIGNED_GE#size(1024)      5308.796         20.557
   IntVector.UNSIGNED_LT#size(1024)        4944.744         10.606
   LongVector.UNSIGNED_LE#size(1024)       8459.605         28.683
   ```
   
   [1] https://github.com/openjdk/jdk/tree/master/test/jdk/jdk/incubator/vector
   [2] https://github.com/openjdk/jdk/tree/master/test/hotspot/jtreg/compiler/vectorapi
   [3] https://github.com/openjdk/panama-vector/blob/2aade73adeabdf6a924136b17fd96ccc95c1d160/test/micro/org/openjdk/bench/jdk/incubator/vector/operation/ByteMaxVector.java#L1459
   [4] https://bugs.openjdk.org/browse/JDK-8282850
   [5] https://gist.github.com/changpeng1997/d311127e1015c107197f9b56a92b0fae
   
   TEST_CMD: true
   
   Jira: ENTLLT-6097
   Change-Id: I236cf4a7626af3aad04bf081b47849a00e77df15

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/12725/files
  - new: https://git.openjdk.org/jdk/pull/12725/files/599cf967..d210ae92

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=12725&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=12725&range=00-01

  Stats: 27315 lines in 984 files changed: 17946 ins; 5228 del; 4141 mod
  Patch: https://git.openjdk.org/jdk/pull/12725.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/12725/head:pull/12725

PR: https://git.openjdk.org/jdk/pull/12725