[clang] [AArch64][PAC] Support ptrauth builtins and -fptrauth-intrinsics. (PR #65996)

[Kristof Beyls via cfe-commits]

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@@ -0,0 +1,265 @@
+Pointer Authentication
+======================
+
+.. contents::
+   :local:
+
+Introduction
+------------
+
+Pointer authentication is a technology which offers strong probabilistic protection against exploiting a broad class of memory bugs to take control of program execution.  When adopted consistently in a language ABI, it provides a form of relatively fine-grained control flow integrity (CFI) check that resists both return-oriented programming (ROP) and jump-oriented programming (JOP) attacks.
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kbeyls wrote:

I *think* that for documentation, we also tend to stick to maximum 80-char line length. Might be worthwhile to reformat before landing if that is indeed the case?

https://github.com/llvm/llvm-project/pull/65996