[llvm] [DebugInfo][RegisterCoalescer] Drop DBG_VALUEs with unsupported register class (PR #143132)

[Matt Arsenault via llvm-commits]

https://github.com/arsenm commented:

What does DBG_VALUE do with the register value? How is it encoded? Can we relax the verifier for these fake uses, or alternatively drop the subregister index from the debug use? Is there a way to express a bit extract directly in the debug info? 

https://github.com/llvm/llvm-project/pull/143132