RFR: 8370454: C2 SuperWord: unsigned comparison information is lost for VectorMaskCmp [v2]

[Hamlin Li]

On Thu, 23 Oct 2025 10:17:32 GMT, Hamlin Li <mli at openjdk.org> wrote:

>> @Hamlin-Li That looks like a great improvement :)
>> 
>> All I am missing are some test cases. And if possible: IR rules 😉
>
>> @Hamlin-Li That looks like a great improvement :)
> 
> Thank you for having a look! :)
>  
>> All I am missing are some test cases. And if possible: IR rules 😉
> 
> Yes, I also added some tests and IR rules of course. :)

> @Hamlin-Li I just looked at your Bug report [JDK-8370481](https://bugs.openjdk.org/browse/JDK-8370481). Can you add a reproducer, and on what platforms you have experienced the failure?

Please check the added test cases, if it's run with JDK master, the test cases will fail on x86.

> If you are fixing a bug here, we should focus on the bug only. After all, we may want to backport the bugfix.

Yes. In fact at first I did not realise the existence of the bug. After read your previous question, I did more investigation and found out that I'm working a bug fix at the same time. I can change the title of this pr to "8370481: C2 SuperWord: Long/Integer.compareUnsigned return wrong value in SLP" if you wish.
Maybe I should close [JDK-8370454](https://bugs.openjdk.org/browse/JDK-8370454) at the same time?
Please let me know.

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PR Comment: https://git.openjdk.org/jdk/pull/27942#issuecomment-3436256229