RFR: 8283726: x86_64 intrinsics for compareUnsigned method in Integer and Long

[Sandhya Viswanathan]

On Wed, 8 Jun 2022 09:39:04 GMT, Quan Anh Mai <duke at openjdk.java.net> wrote:

>> Hi,
>> 
>> This patch implements intrinsics for `Integer/Long::compareUnsigned` using the same approach as the JVM does for long and floating-point comparisons. This allows efficient and reliable usage of unsigned comparison in Java, which is a basic operation and is important for range checks such as discussed in #8620 .
>> 
>> Thank you very much.
>
> I have added a benchmark for the intrinsic. The result is as follows, thanks a lot:
> 
>                                                     Before          After
>     Benchmark                 (size)  Mode  Cnt  Score   Error  Score   Error  Units
>     Integers.compareUnsigned     500  avgt   15  0.527 ± 0.002  0.498 ± 0.011  us/op
>     Longs.compareUnsigned        500  avgt   15  0.677 ± 0.014  0.561 ± 0.006  us/op

@merykitty Could you please also add the micro benchmark where compareUnsigned result is stored directly in an integer and show the performance of that?

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PR: https://git.openjdk.org/jdk/pull/9068