RFR: 8354242: VectorAPI: combine vector not operation with compare [v2]

[Emanuel Peter]

On Mon, 28 Apr 2025 07:46:14 GMT, erifan <duke at openjdk.org> wrote:

>> I would also prefer if you added the IR restrictions rather than the JTREG requires.
>> The benefit is that we can still run the tests on all platforms, at least for result verification.
>> 
>> Imagine someone adds optimizations to a new platform, but does not know about this test here. They make a mistake, and there is a bug, leading either to a crash or wrong result. With the requires, you test would never even run, and we would not catch it. With the IR applyIf, we would catch the bug.
>
> I can make the change, it's not complex, but it is different from what I thought before.
> 
> I thought that supporting vector was the default behavior, is it right? So when I was doing an architecture-independent feature or optimization, I should just exclude those unsupported cases from the test, so that all potential environments would be tested. If I was doing an architecture- or feature-dependent optimization, then I should limit the test to run only in supported environments.
> 
> For this case, **the current meaning of @requires is "skip this test when -XX:UseAVX=0 is specified on the x86 architecture, otherwise run the tests".** So if a new architecture (say s390) supports related vector operations in the future, then this test will be run on that platform by default.
> 
> If all architecture-independent tests are restricted with applyIfCPUFeatureOr, then when we support a new architecture, we will need to modify all tests, otherwise no test will run on this architecture.

Hmm, I'm not convinced that vector operations are supported by default. Every platform supports a different set.

In your case, you so far only have negative rules, i.e. you expect certain nodes NOT to be generated / in the final IR. I suppose in that case you can assert that you NEVER get those nodes, because if you have vectors not supported, they will not show up because of that, and if you do support vectors, they should be optimized away.

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PR Review Comment: https://git.openjdk.org/jdk/pull/24674#discussion_r2063752141