safe. This can happen we a subreg_to_reg 0 has been coalesced. One
exception is when the instruction that folds the load is a move, then we
can simply turn it into a 32-bit load from the stack slot.
rdar://7170444
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@81494 91177308-0d34-0410-b5e6-96231b3b80d8