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

[Matt Arsenault via llvm-commits]

arsenm wrote:

> After the register inflation, some registers may be changed to a type that is not supported by DBG_VALUE. It may happen because MachineRegisterInfo::recomputeRegClass() doesn't take DBG_VALUEs into account.

I don't understand this; DBG_VALUE should have no register constraints. It should not be possible for it to not support a class, and recomputeRegClass would never need to consider constraints from it 

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