RFR: 8365302: RISC-V: compiler/loopopts/superword/TestAlignVector.java fails when vlen=128

[Dingli Zhang]

On Tue, 12 Aug 2025 06:38:33 GMT, Dingli Zhang <dzhang at openjdk.org> wrote:

> Hi all,
> Please take a look and review this PR, thanks!
> 
> [JDK-8352529](https://bugs.openjdk.org/browse/JDK-8352529) enables this IR verification test for riscv. This test pass when vlen=256, but fail when vlen=128.
> 
> The error occurs because the test13aIL and test13bIL cases require ensuring that vectors are larger than what unrolling produces; otherwise, the corresponding vector IR will not be generated.
> 
> We can use `JTREG="JAVA_OPTIONS=-XX:+TraceSuperWordLoopUnrollAnalysis"` during testing. 
> The tips in the log:
> 
> 76844 1333 b 4 compiler.loopopts.superword.TestAlignVector::test13aIL (42 bytes)
> slp analysis fails: unroll limit greater than max vector
> 
> slp analysis: set max unroll to 4
> 
> 
> Therefore, we need to limit MaxVectorSize to greater than or equal to 32 bytes.
> 
> ### Test (fastdebug)
> - [x] Run compiler/loopopts/superword/TestAlignVector.java on qemu-system with RVV when vlen=128/256

Thanks all for the review!

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PR Comment: https://git.openjdk.org/jdk/pull/26738#issuecomment-3181863276