RFR: 8360192: C2: Make the type of count leading/trailing zero nodes more precise [v9]

[Qizheng Xing]

On Tue, 9 Sep 2025 08:40:35 GMT, Emanuel Peter <epeter at openjdk.org> wrote:

>> Hi @jatin-bhateja, I've added a micro benchmark that includes the `numberOfNibbles` implementation from this PR description and your micro kernel.
>> 
>> Here's my test results on an Intel(R) Xeon(R) Platinum:
>> 
>> 
>> # Baseline:
>> Benchmark                                  Mode  Cnt     Score   Error  Units
>> CountLeadingZeros.benchClzLongConstrained  avgt   15  1517.888 ± 5.691  ns/op
>> CountLeadingZeros.benchNumberOfNibbles     avgt   15  1094.422 ± 1.753  ns/op
>> 
>> # This patch:
>> Benchmark                                  Mode  Cnt    Score   Error  Units
>> CountLeadingZeros.benchClzLongConstrained  avgt   15    0.948 ± 0.002  ns/op
>> CountLeadingZeros.benchNumberOfNibbles     avgt   15  942.438 ± 1.742  ns/op
>
> @MaxXSoft Feel free to just ping me again when you want another review :)
> FYI: I'll be on a longer vacation starting in about a week, so don't expect me to respond then.

@eme64 Thank you for the review!

@merykitty @jatin-bhateja Do you have any other suggestions regarding the latest changes in this patch?

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PR Comment: https://git.openjdk.org/jdk/pull/25928#issuecomment-3460610149