[llvm] [ARM] Add pass for handling undef early-clobber values (PR #77770)

[via llvm-commits]

ostannard wrote:

To make this pass target-independent, you could move the target-specific bits (`getVRLargestSuperClass`, `isVectorRegClass`, `getUndefInitOpcode`, ...) into `TargetRegisterInfo` and `TargetInstrInfo`, which already have a lot of virtual functions for querying target-specific information from target-independent classes.

https://github.com/llvm/llvm-project/pull/77770