RFR: 8372980: [VectorAPI] AArch64: Add intrinsic support for unsigned min/max reduction operations [v4]

[Eric Fang]

On Tue, 27 Jan 2026 18:38:40 GMT, Paul Sandoz <psandoz at openjdk.org> wrote:

>> Eric Fang has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Move helper functions into c2_MacroAssembler_aarch64.hpp
>
> The general way code flows right now, but not often, is from jdk/master to panama-vector/vectorIntrinsics, since most of the development work is in the mainline (exceptions to that are the float16 and Valhalla alignment work which are large efforts).
> 
> I am very reluctant to include all the auto-generated micro benchmarks in mainline. There is a huge number of them and i am not certain they provide as much value as they did now we have the IR test framework. In may cases, given the simplicity of what they measure, they were designed to ensure C2 generates the right instructions. The IR test framework is better at determining that by testing the right IR nodes are generated - and they get run as part of the existing HotSpot test suite.
> 
> The IR test framework is of course no substitute, in general, for performance tests. A better focus for Vector API performance tests is i think Emanuel's work [here](https://github.com/openjdk/jdk/pull/28639/) and use-cases/algorithms that can be implemented concisely.

@PaulSandoz thanks for your insight, this really makes sense to me.

Hi @theRealAph,  I've added a number of IR tests into this PR, and there are also numerous related tests in `test/jdk/jdk/incubator/vector/`, like [UMINByte128VectorTests()](https://github.com/openjdk/jdk/blob/fa1b1d677ac492dfdd3110b9303a4c2b009046c8/test/jdk/jdk/incubator/vector/Byte128VectorTests.java#L3283), which are sufficient to ensure the qulity of this PR.

I share your feeling that it's inconvenience to review the JMH test that isn't in the mainline. I should have included the JMH link in the commit message, which is here: [Byte128Vector.UMINLanes](https://github.com/openjdk/panama-vector/blob/2181a35d64762bb3ac3d7fb66212c2559b6b72b5/test/micro/org/openjdk/bench/jdk/incubator/vector/operation/Byte128Vector.java#L1542). Is it fine to you?

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PR Comment: https://git.openjdk.org/jdk/pull/28693#issuecomment-3808702684