[llvm] [PAC][IR][AArch64] Add "ptrauth(...)" Constant to represent signed pointers. (PR #85738)

[Eli Friedman via llvm-commits]

efriedma-quic wrote:

> @efriedma-quic But it is Constant, not ConstantExpr. So in this sense it is not different from e.g. DSOLocalEquivalent or NoCFIValue that we are already having in tree. Or maybe I'm missing what do you mean?

Well, no, but those are both used pretty infrequently.  Actually, I forgot they already existed...

https://github.com/llvm/llvm-project/pull/85738