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

[Jon Roelofs via llvm-commits]

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jroelofs wrote:

I think organizationally this would be a bit easier to reason about if the outer/inner if's were swapped for all of these, as in: first check for `if (FPDiff != 0)` and handle the three cases of pauth-lr, pacm, and pauth inside of each leg of that.

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