[clang] [llvm] [AArch64] Support for 9.5-A PAuthLR (PR #75947)

[Tomas Matheson via cfe-commits]

tmatheson-arm wrote:

Manually merged to avoid squashing the commits:
92dc23c0e054183e8adf41aad2a2609cefc392c0
934b1099cbf14fa3f86a269dff957da8e5fb619f
5992ce90b8c0fac06436c3c86621fbf6d5398ee5


https://github.com/llvm/llvm-project/pull/75947