RFR: 8354242: VectorAPI: combine vector not operation with compare [v9]

[Emanuel Peter]

On Tue, 8 Jul 2025 05:56:58 GMT, erifan <duke at openjdk.org> wrote:

>> The current testing status for the conditions you listed:
>>> 1. Not MaskCmp.
>> 
>> **No test for it, tested locally**, Because I think this condition is too straightforward.
>> 
>>> 2. More than one use.
>> 
>> **Tested**, see `VectorMaskCompareNotTest.java line 1118`.
>> 
>>> predicate negatable and vector not all ones. 
>> 
>> **Tested**, see `VectorMaskCompareNotTest.java line 1126`.
>> 
>>> predicate not negatable and vector not all ones. 
>> 
>> **No test for it**, because we have tests for `predicate not negatable` or `vector not all ones`. If either is `false`, return nullptr.
>> 
>>> predicate negatable and vector all ones. 
>> 
>> **A lot of tests for it**. For example `VectorMaskCompareNotTest.java line 1014`.
>> 
>>> predicate not negatable and vectors all ones. 
>> 
>> **Tested**, see `VectorMaskCompareNotTest.java line 1222`.
>
>> Indentation for clarity.
> 
> Done.
> 
> I think we have enough negative tests. Please take a look at this PR, thanks~

Thanks for your answers @erifan !

Can you please answer these as well?

> predicate cannot be negated AND the vector is all ones. Can you explain this condition?

A code comment would be helpful for this case. I'm a little bit struggling to understand the bracket/negation here.

> Why do you guard against VectorNode::is_all_ones_vector(in2) at all?

Is this necessary? Why?

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PR Review Comment: https://git.openjdk.org/jdk/pull/24674#discussion_r2191900155