RFR: 8365570: C2 fails assert(false) failed: Unexpected node in SuperWord truncation: CastII [v2]

[Christian Hagedorn]

On Mon, 22 Sep 2025 03:00:18 GMT, Jasmine Karthikeyan <jkarthikeyan at openjdk.org> wrote:

>> test/hotspot/jtreg/compiler/vectorization/TestSubwordTruncation.java line 431:
>> 
>>> 429:     }
>>> 430: 
>>> 431:     @Test(compLevel = CompLevel.C2)
>> 
>> Any particular reason you've chosen `C2` here and not let the IR framework handle it? (by default it's `ANY` which will compile at the highest available tier). I'm also wondering if this test would fail if someone ran the test with a build without C2.
>
> Thanks for the comment! I used `CompLevel.C2` here to simulate an -Xcomp environment, since unfortunately I couldn't replicate the crash without it with the IR framework. I'll do some investigation to find a way to ensure that it won't fail without C2.

When you specify `@Warmup(0)`, the IR framework should directly compile it at the highest level which should be C2 if you are not running with a client build. So, I would have expected that it makes no difference. Can you double-check if you can reproduce it with `CompLevel.C2` but not without?

-------------

PR Review Comment: https://git.openjdk.org/jdk/pull/26827#discussion_r2366902189