[llvm-branch-commits] compiler-rt: Introduce runtime functions for emulated PAC. (PR #133530)

[Peter Collingbourne via llvm-branch-commits]

https://github.com/pcc created https://github.com/llvm/llvm-project/pull/133530

The emulated PAC runtime functions emulate the ARMv8.3a pointer
authentication instructions and are intended for use in heterogeneous
testing environments. For more information, see the associated RFC:
https://discourse.llvm.org/t/rfc-emulated-pac/85557

TODO:
- Add tests.