[llvm] [AMDGPU] Avoid put implicit_def into bundle that break reg's liveness (PR #142563)

[via llvm-commits]

Shoreshen wrote:

Hi @jayfoad @arsenm , after read through `finalizeBundle` it seems like localdef cannot recognize that $vgpr2_vgpr3 was defined for their subreg $vgpr2 and $vgpr3.

I following the logic from MachineVerifier's liveness check for register that if 1 of the subreg is in localdef, then its locally defined.

This may cause problem that if we only define $vgpr2 but not $vgpr3. Currently I'm following the logic of MachineVerifier, but if needed, I think I can use regunit to avoid this problem.

Thanks for the kind help and illustration~~

https://github.com/llvm/llvm-project/pull/142563