[llvm] [BOLT][AArch64] Support for pointer authentication (PR #117578)

[Gergely Bálint via llvm-commits]

bgergely0 wrote:

Hi @ayermolo 

After some discussion with @kbeyls we believe that it's not the best idea to rely on the CFG to find locations to insert OpNegateRAState CFIs. Partly because of the issue with noreturn functions, partly because of other possible issues.

Instead, I will try the following:
- save locations if .cfi_negate_ra_state-s in the input functions,
- work out the signedness of each MCInst,
- track that information in Annotations,
- after all optimizations, find where the state is changing and emit .cfi_negate_ra_state

Let me know if you have any comments on this approach. It seems more sound than what is in this PR currently, but it would require more memory because we would be tracking extra annotations on every MCInst.

https://github.com/llvm/llvm-project/pull/117578