[clang] [Clang][CodeGen][CIR][NFC] Refactor CGCXXABI classes for code sharing (PR #165078)

[Bruno Cardoso Lopes via cfe-commits]

https://github.com/bcardosolopes commented:

Nice! I like the direction and excited to see more things moving to that level of abstraction. Some questions inline.

https://github.com/llvm/llvm-project/pull/165078