RFR: 8303762: Optimize vector slice operation with constant index using VPALIGNR instruction [v8]

[erifan]

On Wed, 20 Aug 2025 10:11:47 GMT, Jatin Bhateja <jbhateja at openjdk.org> wrote:

>> Patch optimizes Vector. slice operation with constant index using x86 ALIGNR instruction.
>> It also adds a new hybrid call generator to facilitate lazy intrinsification or else perform procedural inlining to prevent call overhead and boxing penalties in case the fallback implementation expects to operate over vectors. The existing vector API-based slice implementation is now the fallback code that gets inlined in case intrinsification fails.
>> 
>>  Idea here is to add infrastructure support to enable intrinsification of fast path for selected vector APIs, else enable inlining of fall-back implementation if it's based on vector APIs. Existing call generators like PredictedCallGenerator, used to handle bi-morphic inlining, already make use of multiple call generators to handle hit/miss scenarios for a particular receiver type. The newly added hybrid call generator is lazy and called during incremental inlining optimization. It also relieves the inline expander to handle slow paths, which can easily be implemented library side (Java).
>> 
>> Vector API jtreg tests pass at AVX level 2, remaining validation in progress.
>> 
>> Performance numbers:
>> 
>> 
>> System : 13th Gen Intel(R) Core(TM) i3-1315U
>> 
>> Baseline:
>> Benchmark                                                (size)   Mode  Cnt      Score   Error   Units
>> VectorSliceBenchmark.byteVectorSliceWithConstantIndex1     1024  thrpt    2   9444.444          ops/ms
>> VectorSliceBenchmark.byteVectorSliceWithConstantIndex2     1024  thrpt    2  10009.319          ops/ms
>> VectorSliceBenchmark.byteVectorSliceWithVariableIndex      1024  thrpt    2   9081.926          ops/ms
>> VectorSliceBenchmark.intVectorSliceWithConstantIndex1      1024  thrpt    2   6085.825          ops/ms
>> VectorSliceBenchmark.intVectorSliceWithConstantIndex2      1024  thrpt    2   6505.378          ops/ms
>> VectorSliceBenchmark.intVectorSliceWithVariableIndex       1024  thrpt    2   6204.489          ops/ms
>> VectorSliceBenchmark.longVectorSliceWithConstantIndex1     1024  thrpt    2   1651.334          ops/ms
>> VectorSliceBenchmark.longVectorSliceWithConstantIndex2     1024  thrpt    2   1642.784          ops/ms
>> VectorSliceBenchmark.longVectorSliceWithVariableIndex      1024  thrpt    2   1474.808          ops/ms
>> VectorSliceBenchmark.shortVectorSliceWithConstantIndex1    1024  thrpt    2  10399.394          ops/ms
>> VectorSliceBenchmark.shortVectorSliceWithConstantIndex2    1024  thrpt    2  10502.894          ops/ms
>> VectorSliceB...
>
> Jatin Bhateja has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Update callGenerator.hpp copyright year

src/hotspot/share/classfile/vmIntrinsics.hpp line 1178:

> 1176:                                    "Ljdk/internal/vm/vector/VectorSupport$Vector;"                                                             \
> 1177:                                    "Ljdk/internal/vm/vector/VectorSupport$VectorSliceOp;)"                                                     \
> 1178:                                    "Ljdk/internal/vm/vector/VectorSupport$Vector;")                                                     \

Seems this `` is not aligned ?

src/hotspot/share/classfile/vmIntrinsics.hpp line 1179:

> 1177:                                    "Ljdk/internal/vm/vector/VectorSupport$VectorSliceOp;)"                                                     \
> 1178:                                    "Ljdk/internal/vm/vector/VectorSupport$Vector;")                                                     \
> 1179:    do_name(vector_slice_name, "sliceOp")                                                                                                         \

ditto

test/hotspot/jtreg/compiler/vectorapi/TestSliceOptValueTransforms.java line 45:

> 43:     public static final VectorSpecies<Short> SSP = ShortVector.SPECIES_PREFERRED;
> 44:     public static final VectorSpecies<Integer> ISP = IntVector.SPECIES_PREFERRED;
> 45:     public static final VectorSpecies<Long> LSP = LongVector.SPECIES_PREFERRED;

The implementation supports floating point types, but why doesn't the test include fp types?

test/hotspot/jtreg/compiler/vectorapi/TestSliceOptValueTransforms.java line 122:

> 120:                       .intoArray(bdst, i);
> 121:         }
> 122:     }

Since this optimization also benefits the slice variant with mask, could you add some tests for it as well?

test/micro/org/openjdk/bench/jdk/incubator/vector/VectorSliceBenchmark.java line 59:

> 57:     static final VectorSpecies<Short> sspecies   = ShortVector.SPECIES_PREFERRED;
> 58:     static final VectorSpecies<Integer> ispecies = IntVector.SPECIES_PREFERRED;
> 59:     static final VectorSpecies<Long> lspecies    = LongVector.SPECIES_PREFERRED;

Ditto, no fp types ?

test/micro/org/openjdk/bench/jdk/incubator/vector/VectorSliceBenchmark.java line 133:

> 131:                       .intoArray(bdst, i);
> 132:         }
> 133:     }

Ditto, add a benchmark for the slice variant with mask ?

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

PR Review Comment: https://git.openjdk.org/jdk/pull/24104#discussion_r2378092410
PR Review Comment: https://git.openjdk.org/jdk/pull/24104#discussion_r2378093047
PR Review Comment: https://git.openjdk.org/jdk/pull/24104#discussion_r2378310217
PR Review Comment: https://git.openjdk.org/jdk/pull/24104#discussion_r2378337340
PR Review Comment: https://git.openjdk.org/jdk/pull/24104#discussion_r2378312763
PR Review Comment: https://git.openjdk.org/jdk/pull/24104#discussion_r2378342519