[llvm] [BOLT][AArch64] Add minimal support for liveness analysis. (PR #183298)

[Paschalis Mpeis via llvm-commits]

https://github.com/paschalis-mpeis commented:

Hey Alexandre,

Thanks for working in this area!
It looks good overall, but since this is a new pass for AArch64, so we need to study the surrounding code too.

I did a first pass over the changes / relevant code.
Not all of my comments specific to this PR.

Regarding the discussion around the scavenge function, it's reasonable to:
- add both functions (scavengeRegAfter/scavengeRegBefore)
- or rename to scavengeRegAt to be consistent with the base class.

https://github.com/llvm/llvm-project/pull/183298