[clang] [llvm] [SystemZ] Do not extend integer arguments in z/OS XPLINK64 ABI (PR #206833)

[Ulrich Weigand via llvm-commits]

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uweigand wrote:

Yes, I think we're moving in circles now.  If adding AExt fixes a test case, that is just luck - AExt does not guarantee this.   We need to understand what the actual requirements are.  Can you elaborate on exactly *why* that test case is failing?  What is that external `__class` routine doing?

https://github.com/llvm/llvm-project/pull/206833