[llvm] [AArch64] Handle inttoptr+add+ptrtoint pattern in lowerConstantPtrAuth (PR #189474)

[Eli Friedman via llvm-commits]

https://github.com/efriedma-quic commented:

Please add an appropriate reportFatalUsageError() call for the case where the `dyn_cast<GlobalValue>()` fails.  I'm concerned that we're going to find more forms of constant expressions getting miscompiled.

https://github.com/llvm/llvm-project/pull/189474