RFR: 8350463: AArch64: Add vector rearrange support for small lane count vectors [v3]

[Xiaohong Gong]

On Mon, 17 Mar 2025 07:18:22 GMT, Emanuel Peter <epeter at openjdk.org> wrote:

> Thanks for adding the IR test!
> 
> Actually I just checked, and it seems we don't really have many tests for `rearrange`, and that's not great. The only test I could find was: `test/hotspot/jtreg/compiler/vectorapi/TestTwoVectorPermute.java` But the coverage here is not sufficient at all. I think it only covers 256 bit vectors.
> 
> Your test now covers 64 bit and 128 bit cases, but not for all types. I guess you are only targetting small types, so I don't want to burden you with writing tests for all sizes now. But we should definitely file an RFE that tests `rearrange` more thoroughly.
> 
> Maybe I just didn't find the tests, so please check again yourself first ;)
> 
> I have not reviewed the actual aarch64 code, I'll leave that to experts in that field ;)

Thanks for looking at this PR again @eme64 ! Vector API has its own jtreg tests under `test/jdk/jdk/incubator/vector/`. I double checked that it has the `rearrange` test for all vector species. Please see one of the test here: https://github.com/openjdk/jdk/blob/master/test/jdk/jdk/incubator/vector/Long128VectorTests.java#L4954  That's also way I did not add the correct tests in the IR test file.

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PR Comment: https://git.openjdk.org/jdk/pull/23790#issuecomment-2728437681