[llvm] [AArch64] Fix return address auth in swiftasync epilogues (PR #189484)

[Jon Roelofs via llvm-commits]

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jroelofs wrote:

I don't know of any non-swift asymmetric calling conventions like this.

> Also title does seem to indicate swiftasync right now, was that just updated for clarity?

Yes, I changed that on behalf of the author in response to this. I haven't touched the body description.

https://github.com/llvm/llvm-project/pull/189484