[llvm] [PromoteMemToReg] Insert store undef when removing lifetime markers (PR #191909)

[Orlando Cazalet-Hyams via llvm-commits]

https://github.com/OCHyams commented:

Sorry to add to the mix - following up on one of Nikita's points, I think there's debug info implications that should probably be understood/explained and potentially improved (2 comments inline)

https://github.com/llvm/llvm-project/pull/191909