RFR: 8338023: Support two vector selectFrom API [v7]

[Emanuel Peter]

On Fri, 6 Sep 2024 18:08:04 GMT, Jatin Bhateja <jbhateja at openjdk.org> wrote:

>> test/jdk/jdk/incubator/vector/ShortMaxVectorTests.java line 1048:
>> 
>>> 1046:         return SHORT_GENERATOR_SELECT_FROM_TRIPLES.stream().map(List::toArray).
>>> 1047:                 toArray(Object[][]::new);
>>> 1048:     }
>> 
>> Just a control question: does this also occasionally generate examples with out-of-bounds indices? Negative out of bounds and positive out of bounds?
>
> Original API did throw IndexOutOfBoundsException, but later on we have moved away from exception throwing semantics to wrapping semantics.
> Please find details at following comment
> https://github.com/openjdk/jdk/pull/20508#issuecomment-2306344606

And do we test that the wrapping works correctly?

>> test/jdk/jdk/incubator/vector/ShortMaxVectorTests.java line 5812:
>> 
>>> 5810:                 ShortVector bv = ShortVector.fromArray(SPECIES, b, i);
>>> 5811:                 ShortVector idxv = ShortVector.fromArray(SPECIES, idx, i);
>>> 5812:                 idxv.selectFrom(av, bv).intoArray(r, i);
>> 
>> Would this test catch a bug where the backend would generate vectors that are too long or too short?
>
> Existing vectorAPI inline expansion entry points explicitly pass lane type and count as intrinsic arguments, this is used to create concrete ideal vector types.

That does not answer my question. If the backend operations you implemented would have the wrong vector-length: do we have any tests that would catch that? Often that requires not just going "up" with a loop but also "counting down" with the loop iv. Do you know what I mean?

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PR Review Comment: https://git.openjdk.org/jdk/pull/20508#discussion_r1758999902
PR Review Comment: https://git.openjdk.org/jdk/pull/20508#discussion_r1759002531