RFR: 8366488: JVM_FindClassFromClass should assert that from class is never null

[David Holmes]

On Thu, 23 Oct 2025 15:55:41 GMT, Paul Hübner <phubner at openjdk.org> wrote:

> Hi all,
> 
> The `from_class` nullcheck  in `JVM_FindClassFromClass` is redundant, as the this is the Java mirror which cannot be null during class linking/verification [1]. Therefore, it has been refactored to be an assertion instead.
> 
> Testing: tiers 1-4 Linux (x64, AArch64), macOS (x64, AArch64), Windows (x64). As part of a separate experiment, I've also run tiers 1-6 on x64 Linux with a non-null assertion before we call `Verifier::inference_verify` (which in turn, eventually, calls this code).
> 
> [1] For reasoning, see https://bugs.openjdk.org/browse/JDK-8366488

I agree with the analysis - the value can never be null based on the current code paths.

Thanks

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Marked as reviewed by dholmes (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/27957#pullrequestreview-3374595739