r305918 and "Bad machine code: Using an undefined physical register"

[Tim Northover via llvm-commits]

> I think what's actually happening is that parent code is forwarding from the second register in an STP, but r305918 is trying to get the kill flag from the first (unaware that a pair is involved at all). I'll ping the person who wrote it.

Sorry, that should be r305885.

Tim.