RFR: 8369456: [TESTBUG] Fix the test failure of TestSelectFromTwoVectorOp.java on sve2 platforms [v2]

[Emanuel Peter]

On Wed, 29 Oct 2025 06:24:46 GMT, erifan <duke at openjdk.org> wrote:

>> According the AD file, partial cases where `vector_length_in_bytes > 8` of the vector API `selectFrom` are not supported on the AArch64 SVE2 platform. But the test `TestSelectFromTwoVectorOp.java` didn't rule out these cases, leading to test faiulres on sve2 plaftforms where `MaxVectorSize > 16`.
>> 
>> This test problem was discovered by simulating a 512-bit sve2 environment using qemu.
>> 
>> This PR fixes these test failures.
>
> erifan has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains two additional commits since the last revision:
> 
>  - Merge branch 'master' into JDK-8369456-select-from-two-vectors-failure
>  - 8369456: [TESTBUG] Fix the test failure of TestSelectFromTwoVectorOp.java on sve2 platforms
>    
>    According the AD file, partial cases where `vector_length_in_bytes > 8`
>    of the vector API `selectFrom` are not supported on the AArch64 SVE2
>    platform. But the test `TestSelectFromTwoVectorOp.java` didn't rule out
>    these cases, leading to test faiulres on sve2 plaftforms where
>    `MaxVectorSize > 16`.
>    
>    This test problem was discovered by simulating a 512-bit sve2
>    environment using qemu.
>    
>    This PR fixes these test failures.

Drive-by comment.

test/hotspot/jtreg/compiler/vectorapi/TestSelectFromTwoVectorOp.java line 221:

> 219:     @IR(counts = {IRNode.SELECT_FROM_TWO_VECTOR_VB, IRNode.VECTOR_SIZE_64, ">0"},
> 220:         applyIfCPUFeature = {"sve2", "true"},
> 221:         applyIf = {"MaxVectorSize", "64"})

Would it make sense to add some IR rule for cases with `MaxVectorSize > 64`? Because now you just weakened the test, rather than ensuring that there is a test for larger sizes.

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PR Review: https://git.openjdk.org/jdk/pull/27723#pullrequestreview-3392525780
PR Review Comment: https://git.openjdk.org/jdk/pull/27723#discussion_r2472393201