RFR: 8365205: C2: Optimize popcount value computation using knownbits [v3]

[Jatin Bhateja]

On Fri, 5 Sep 2025 17:17:52 GMT, Jatin Bhateja <jbhateja at openjdk.org> wrote:

>> This patch optimizes PopCount value transforms using KnownBits information.
>> Following are the results of the micro-benchmark included with the patch
>> 
>> 
>> 
>> System: 13th Gen Intel(R) Core(TM) i3-1315U
>> 
>> Baseline:
>> Benchmark                                      Mode  Cnt       Score   Error  Units
>> PopCountValueTransform.LogicFoldingKerenLong  thrpt    2  215460.670          ops/s
>> PopCountValueTransform.LogicFoldingKerenlInt  thrpt    2  294014.826          ops/s
>> PopCountValueTransform.StockKernelInt         thrpt    2  409295.875          ops/s
>> PopCountValueTransform.StockKernelLong        thrpt    2  368025.608          ops/s
>> 
>> Withopt:
>> Benchmark                                      Mode  Cnt       Score   Error  Units
>> PopCountValueTransform.LogicFoldingKerenLong  thrpt    2  389978.082          ops/s
>> PopCountValueTransform.LogicFoldingKerenlInt  thrpt    2  417261.583          ops/s
>> PopCountValueTransform.StockKernelInt         thrpt    2  418649.269          ops/s
>> PopCountValueTransform.StockKernelLong        thrpt    2  381330.221          ops/s
>> 
>> 
>> Kindly review and share your feedback.
>> 
>> Best Regards,
>> Jatin
>
> Jatin Bhateja has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Update countbitsnode.cpp

Hi @TobiHartmann , @SirYwell , @eme64 , can you kindly verify the changes in the latest patch?

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PR Comment: https://git.openjdk.org/jdk/pull/27075#issuecomment-3268608172