RFR: 8342393: Promote commutative vector IR node sharing [v10]

[Emanuel Peter]

On Thu, 16 Jan 2025 15:04:56 GMT, Jatin Bhateja <jbhateja at openjdk.org> wrote:

>> Patch promotes the sharing of commutative vector IR with the same inputs but different input ordering.
>> Unlike scalar IR where we perform edge swapping by [sorting inputs](https://github.com/openjdk/jdk/blob/master/src/hotspot/share/opto/addnode.cpp#L122) based on node indices during IR idealization, for vector IR we chose a simpler approach to decorate commutative operations with a special node-level flag during IR construction thus
>> obviating any dependency on explicit idealization routines. This flag is later used during GVN hashing to enable node sharing.  
>> 
>> Following are the performance stats for JMH micro included with the patch.
>> 
>> 
>> Granite Rapids (P-core Xeon Server)
>> Baseline : 
>> Benchmark                                                                (size)   Mode  Cnt      Score   Error   Units
>> VectorCommutativeOperSharingBenchmark.commutativeByteOperationShairing     1024  thrpt    2   8982.549          ops/ms
>> VectorCommutativeOperSharingBenchmark.commutativeIntOperationShairing      1024  thrpt    2   6072.773          ops/ms
>> VectorCommutativeOperSharingBenchmark.commutativeLongOperationShairing     1024  thrpt    2   2368.856          ops/ms
>> VectorCommutativeOperSharingBenchmark.commutativeShortOperationShairing    1024  thrpt    2  15215.087          ops/ms
>> 
>> Withopt:
>> Benchmark                                                                (size)   Mode  Cnt      Score   Error   Units
>> VectorCommutativeOperSharingBenchmark.commutativeByteOperationShairing     1024  thrpt    2  11963.554          ops/ms
>> VectorCommutativeOperSharingBenchmark.commutativeIntOperationShairing      1024  thrpt    2   7036.088          ops/ms
>> VectorCommutativeOperSharingBenchmark.commutativeLongOperationShairing     1024  thrpt    2   2906.731          ops/ms
>> VectorCommutativeOperSharingBenchmark.commutativeShortOperationShairing    1024  thrpt    2  17148.131          ops/ms
>> 
>> Sierra Forest (E-core Xeon Server)
>> Baseline:
>> Benchmark                                                                (size)   Mode  Cnt     Score   Error   Units
>> VectorCommutativeOperSharingBenchmark.commutativeByteOperationShairing     1024  thrpt    2  2444.359          ops/ms
>> VectorCommutativeOperSharingBenchmark.commutativeIntOperationShairing      1024  thrpt    2  1710.256          ops/ms
>> VectorCommutativeOperSharingBenchmark.commutativeLongOperationShairing     1024  thrpt    2   308.766          ops/ms
>> VectorCommutativeOperSharingBenc...
>
> Jatin Bhateja has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Review suggestions incorporated

@vnkozlov @jatin-bhateja Ok, then we can leave it at the current `Flag_is_commutative_vector_op`. @jatin-bhateja please file a follow-up RFE and link it with this issue. You can assign it to me if you want - I will try to find someone to take care of the scalar refactoring.

Please add some result verification to the tests, as commented separately.

Once that is done, I can run testing and approve the PR.

test/hotspot/jtreg/compiler/vectorapi/VectorCommutativeOperSharingTest.java line 123:

> 121:     public void testVectorIRSharingDriver2() {
> 122:         for (int i = 0; i < I_SPECIES.loopBound(LENGTH); i += I_SPECIES.length()) {
> 123:             testVectorIRSharing2(i);

Adding some result verification would be nice. Because now you only check that you get the right number of instructions - but that does not mean that they are connected correctly. Result verification could help here.

See:
https://github.com/openjdk/jdk/blob/master/test/hotspot/jtreg/compiler/lib/verify/Verify.java
https://github.com/openjdk/jdk/blob/master/test/hotspot/jtreg/testlibrary_tests/verify/examples/TestVerifyInCheckMethod.java

Also, for random value generation we hope to use this in the future:
https://github.com/openjdk/jdk/blob/master/test/hotspot/jtreg/compiler/lib/generators/Generators.java

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PR Review: https://git.openjdk.org/jdk/pull/22863#pullrequestreview-2558073506
PR Review Comment: https://git.openjdk.org/jdk/pull/22863#discussion_r1919627031