RFR: 8322770: Implement C2 VectorizedHashCode on AArch64 [v2]

[Mikhail Ablakatov]

On Tue, 20 Aug 2024 13:11:17 GMT, Andrew Haley <aph at openjdk.org> wrote:

>> Mikhail Ablakatov 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 one additional commit since the last revision:
>> 
>>   8322770: AArch64: C2: Implement VectorizedHashCode
>>   
>>   The code to calculate a hash code consists of two parts: a stub method that
>>   implements a vectorized loop using Neon instruction which processes 16 or 32
>>   elements per iteration depending on the data type; and an unrolled inlined
>>   scalar loop that processes remaining tail elements.
>>   
>>   [Performance]
>>   
>>   [[Neoverse V2]]
>>   ```
>>                                                               |  328a053 (master) |  dc2909f (this)  |
>>   ----------------------------------------------------------------------------------------------------------
>>     Benchmark                               (size)  Mode  Cnt |    Score    Error |    Score   Error | Units
>>   ----------------------------------------------------------------------------------------------------------
>>     ArraysHashCode.bytes                         1  avgt   15 |    0.805 ?  0.206 |    0.815 ? 0.141 | ns/op
>>     ArraysHashCode.bytes                        10  avgt   15 |    4.362 ?  0.013 |    3.522 ? 0.124 | ns/op
>>     ArraysHashCode.bytes                       100  avgt   15 |   78.374 ?  0.136 |   12.935 ? 0.016 | ns/op
>>     ArraysHashCode.bytes                     10000  avgt   15 | 9247.335 ? 13.691 | 1344.770 ? 1.898 | ns/op
>>     ArraysHashCode.chars                         1  avgt   15 |    0.731 ?  0.035 |    0.723 ? 0.046 | ns/op
>>     ArraysHashCode.chars                        10  avgt   15 |    4.359 ?  0.007 |    3.385 ? 0.004 | ns/op
>>     ArraysHashCode.chars                       100  avgt   15 |   78.374 ?  0.117 |   11.903 ? 0.023 | ns/op
>>     ArraysHashCode.chars                     10000  avgt   15 | 9248.328 ? 13.644 | 1344.007 ? 1.795 | ns/op
>>     ArraysHashCode.ints                          1  avgt   15 |    0.746 ?  0.083 |    0.631 ? 0.020 | ns/op
>>     ArraysHashCode.ints                         10  avgt   15 |    4.357 ?  0.009 |    3.387 ? 0.005 | ns/op
>>     ArraysHashCode.ints                        100  avgt   15 |   78.391 ?  0.103 |   10.934 ? 0.015 | ns/op
>>     ArraysHashCode.ints                      10000  avgt   15 | 9248.125 ? 12.583 | 1340.644 ? 1.869 | ns/op
>>     ArraysHashCode.multibytes                    1  av...
>
> src/hotspot/cpu/aarch64/stubGenerator_aarch64.cpp line 5342:
> 
>> 5340:     __ align(CodeEntryAlignment);
>> 5341: 
>> 5342:     auto unreachable_mark_name = [this](BasicType eltype) -> const char * {
> 
> What's going on here? `eltype` is unused.

Yeah, `eltype` looks like something I forgot to remove, will do.

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PR Review Comment: https://git.openjdk.org/jdk/pull/18487#discussion_r1723296582