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

[Jatin Bhateja]

On Tue, 18 Mar 2025 20:51:46 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
> VectorSliceBenchmark.shortVectorSliceWithVariableIndex     1024 ...

Performance after AVX2 backend modifications


Benchmark                                                (size)   Mode  Cnt      Score   Error   Units
VectorSliceBenchmark.byteVectorSliceWithConstantIndex1     1024  thrpt    2  51644.530          ops/ms
VectorSliceBenchmark.byteVectorSliceWithConstantIndex2     1024  thrpt    2  48171.079          ops/ms
VectorSliceBenchmark.byteVectorSliceWithVariableIndex      1024  thrpt    2   9662.306          ops/ms
VectorSliceBenchmark.intVectorSliceWithConstantIndex1      1024  thrpt    2  14358.347          ops/ms
VectorSliceBenchmark.intVectorSliceWithConstantIndex2      1024  thrpt    2  14619.920          ops/ms
VectorSliceBenchmark.intVectorSliceWithVariableIndex       1024  thrpt    2   6675.824          ops/ms
VectorSliceBenchmark.longVectorSliceWithConstantIndex1     1024  thrpt    2    818.911          ops/ms
VectorSliceBenchmark.longVectorSliceWithConstantIndex2     1024  thrpt    2   4778.321          ops/ms
VectorSliceBenchmark.longVectorSliceWithVariableIndex      1024  thrpt    2   1612.264          ops/ms
VectorSliceBenchmark.shortVectorSliceWithConstantIndex1    1024  thrpt    2  35961.146          ops/ms
VectorSliceBenchmark.shortVectorSliceWithConstantIndex2    1024  thrpt    2  39072.170          ops/ms
VectorSliceBenchmark.shortVectorSliceWithVariableIndex     1024  thrpt    2  11209.685          ops/ms

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PR Comment: https://git.openjdk.org/jdk/pull/24104#issuecomment-3116214722