RFR: 8322726: C2: Unloaded signature class kills argument value

[Dean Long]

On Fri, 26 Apr 2024 11:35:25 GMT, Vladimir Ivanov <vlivanov at openjdk.org> wrote:

> For MethodHandle linkers all arguments are casted to signature classes when target method is known.
> 
> It causes problems when target method signature contains unloaded classes: when loaded class meets unloaded class it turns into a TOP. It effectively kills argument values which correspond to unloaded signature types.
> 
> Proposed fix avoids casts when signature class is unloaded. 
> 
> Testing: hs-tier1 - hs-tier4

Marked as reviewed by dlong (Reviewer).

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PR Review: https://git.openjdk.org/jdk/pull/18973#pullrequestreview-2025945190