RFR: 8322770: Implement C2 VectorizedHashCode on AArch64 [v6]
Andrew Haley
aph at openjdk.org
Tue Sep 17 14:36:13 UTC 2024
On Mon, 16 Sep 2024 17:11:05 GMT, Mikhail Ablakatov <duke at openjdk.org> wrote:
>> Hello,
>>
>> Please review the following PR for [JDK-8322770 Implement C2 VectorizedHashCode on AArch64](https://bugs.openjdk.org/browse/JDK-8322770). It follows previous work done in https://github.com/openjdk/jdk/pull/16629 and https://github.com/openjdk/jdk/pull/10847 for RISC-V and x86 respectively.
>>
>> The code to calculate a hash code consists of two parts: a vectorized loop of Neon instruction that process 4 or 8 elements per iteration depending on the data type and a fully unrolled scalar "loop" that processes up to 7 tail elements.
>>
>> At the time of writing this I don't see potential benefits from providing SVE/SVE2 implementation, but it could be added as a follow-up or independently later if required.
>>
>> # Performance
>>
>> ## Neoverse N1
>>
>>
>> --------------------------------------------------------------------------------------------
>> Version Baseline This patch
>> --------------------------------------------------------------------------------------------
>> Benchmark (size) Mode Cnt Score Error Score Error Units
>> --------------------------------------------------------------------------------------------
>> ArraysHashCode.bytes 1 avgt 15 1.249 ? 0.060 1.247 ? 0.062 ns/op
>> ArraysHashCode.bytes 10 avgt 15 8.754 ? 0.028 4.387 ? 0.015 ns/op
>> ArraysHashCode.bytes 100 avgt 15 98.596 ? 0.051 26.655 ? 0.097 ns/op
>> ArraysHashCode.bytes 10000 avgt 15 10150.578 ? 1.352 2649.962 ? 216.744 ns/op
>> ArraysHashCode.chars 1 avgt 15 1.286 ? 0.062 1.246 ? 0.054 ns/op
>> ArraysHashCode.chars 10 avgt 15 8.731 ? 0.002 5.344 ? 0.003 ns/op
>> ArraysHashCode.chars 100 avgt 15 98.632 ? 0.048 23.023 ? 0.142 ns/op
>> ArraysHashCode.chars 10000 avgt 15 10150.658 ? 3.374 2410.504 ? 8.872 ns/op
>> ArraysHashCode.ints 1 avgt 15 1.189 ? 0.005 1.187 ? 0.001 ns/op
>> ArraysHashCode.ints 10 avgt 15 8.730 ? 0.002 5.676 ? 0.001 ns/op
>> ArraysHashCode.ints 100 avgt 15 98.559 ? 0.016 24.378 ? 0.006 ns/op
>> ArraysHashCode.ints 10000 avgt 15 10148.752 ? 1.336 2419.015 ? 0.492 ns/op
>> ArraysHashCode.multibytes 1 avgt 15 1.037 ? 0.001 1.037 ? 0.001 ...
>
> Mikhail Ablakatov has updated the pull request incrementally with three additional commits since the last revision:
>
> - Optimize both the stub and inlined parts of the implementation
>
> Process T_CHAR/T_SHORT elements using T8H arrangement instead of T4H.
> Add a non-unrolled vectorized loop to the stub to handle vectorizable
> tail portions of arrays multiple to 4/8 elements (for ints / other
> types). Make the stub process array as a whole instead of relying on
> the inlined part to process an unvectorizable tail.
> - cleanup: add comments and simplify the orr ins
> - cleanup: remove redundant copyright notice
src/hotspot/cpu/aarch64/stubGenerator_aarch64.cpp line 5420:
> 5418:
> 5419: // Put 0-3'th powers of 31 into a single SIMD register together. The register will be used in
> 5420: // the SMALL and LARGE LOOPS' EPILOQUES. The initialization is hoisted here and the register's
Suggestion:
// the SMALL and LARGE LOOPS' epilogues. The initialization is hoisted here and the register's
-------------
PR Review Comment: https://git.openjdk.org/jdk/pull/18487#discussion_r1763363838
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