[llvm] [CodeGen] Add code new pm code stubs for all backends (PR #78552)

[via llvm-commits]

paperchalice wrote:

> Not sure if it's a good idea to do every target at once until there's an effort to port that target's passes. If the interface changes again when bringing these up, it will just be a larger hassle to update all the implementations

Agreed, the interface may change in future, `MachineFunctionPassManager` may change to `ModulePassManager`.

https://github.com/llvm/llvm-project/pull/78552