diff --git a/lib/CodeGen/MachineInstr.cpp b/lib/CodeGen/MachineInstr.cpp
index f7a0e10..99081bd 100644
--- a/lib/CodeGen/MachineInstr.cpp
+++ b/lib/CodeGen/MachineInstr.cpp
@@ -221,6 +221,7 @@
   case MachineOperand::MO_Metadata:
     return getMetadata() == Other.getMetadata();
   }
+  llvm_unreachable("Invalid machine operand type");
 }
 
 /// print - Print the specified machine operand.