RFR: 8303279: C2 Compiler crash (triggered by Kotlin 1.8.10) [v2]

[Roland Westrelin]

On Tue, 27 Jun 2023 13:17:38 GMT, Roland Westrelin <roland at openjdk.org> wrote:

>> Volker Simonis has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Added Roland's new test
>
> FWIW, I propose an alternate fix here. https://github.com/openjdk/jdk/compare/master...rwestrel:jdk:JDK-8303279
> Seeing null or a nullable value at a `SubTypeCheck` could be a bug as the expectation is that inputs are null checked and the implementation of `SubTypeCheck` would crash with a null input. So I added an assert to `SubTypeCheckNode::sub` to catch a nullable input. The assert fires with the test because split if runs with a non yet fully collapsed dead path. So I tweak split if so it's delayed until the path is collapsed. When running testing I found that the assert would fire in other cases because of values known to be non null be not marked as such. The end result is a bigger patch.

> Thanks @rwestrel. I'm fine with your patch. Do you want to take JDK-8303279 and propose your fix as PR? I will then close mine.

Let me open the PR. I will away for a week though starting later today.

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PR Comment: https://git.openjdk.org/jdk/pull/14600#issuecomment-1609593728