RFR: 8375653: C2: CmpUNode::sub is not monotonic [v3]

[Quan Anh Mai]

On Thu, 22 Jan 2026 12:19:01 GMT, Christian Hagedorn <chagedorn at openjdk.org> wrote:

>> Quan Anh Mai has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Test Long::compareUnsigned
>
> Otherwise, the fix looks good and is nicely solved with unsigned types!
> 
> I agree with @eme64 that we should have better coverage either with IR tests and/or gtests. Since gtests are out of question for JDK 26, I suggest to have some basic IR test coverage for your improvement using unsigned types. We can then still come back in JDK 27 with gtests.

@chhagedorn @eme64 I have added an IR test to verify that the folding happens as expected.

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PR Comment: https://git.openjdk.org/jdk/pull/29308#issuecomment-3784479722