diff --git a/include/llvm/CodeGen/MachineInstrBuilder.h b/include/llvm/CodeGen/MachineInstrBuilder.h
index 06f5bf06d9e..51900603ac9 100644
--- a/include/llvm/CodeGen/MachineInstrBuilder.h
+++ b/include/llvm/CodeGen/MachineInstrBuilder.h
@@ -84,11 +84,6 @@ public:
     return *this;
   }
 
-  const MachineInstrBuilder &addUndef() const {
-    MI->addOperand(MachineOperand::CreateUndef());
-    return *this;
-  }
-
   /// addMemOperand - Add a memory operand to the machine instruction.
   const MachineInstrBuilder &addMemOperand(const MemOperand &MO) const {
     MI->addMemOperand(MO);
diff --git a/include/llvm/CodeGen/MachineOperand.h b/include/llvm/CodeGen/MachineOperand.h
index b4601e18fa7..d62c8f8b474 100644
--- a/include/llvm/CodeGen/MachineOperand.h
+++ b/include/llvm/CodeGen/MachineOperand.h
@@ -33,16 +33,15 @@ class MachineRegisterInfo;
 class MachineOperand {
 public:
   enum MachineOperandType {
-    MO_Register,                // Register operand
-    MO_Immediate,               // Immediate operand
-    MO_FPImmediate,             // FP immediate operand
+    MO_Register,                // Register operand.
+    MO_Immediate,               // Immediate Operand
+    MO_FPImmediate,
     MO_MachineBasicBlock,       // MachineBasicBlock reference
     MO_FrameIndex,              // Abstract Stack Frame Index
     MO_ConstantPoolIndex,       // Address of indexed Constant in Constant Pool
     MO_JumpTableIndex,          // Address of indexed Jump Table for switch
     MO_ExternalSymbol,          // Name of external global symbol
-    MO_GlobalAddress,           // Address of a global value
-    MO_Undef                    // Undef
+    MO_GlobalAddress            // Address of a global value
   };
 
 private:
@@ -131,7 +130,6 @@ public:
   bool isJumpTableIndex() const { return OpKind == MO_JumpTableIndex; }
   bool isGlobalAddress() const { return OpKind == MO_GlobalAddress; }
   bool isExternalSymbol() const { return OpKind == MO_ExternalSymbol; }
-  bool isUndef() const { return OpKind == MO_Undef; }
 
   bool isReg() const { return OpKind == MO_Register; }
   bool isImm() const { return OpKind == MO_Immediate; }
@@ -377,11 +375,6 @@ public:
     Op.setOffset(Offset);
     return Op;
   }
-  static MachineOperand CreateUndef() {
-    MachineOperand Op(MachineOperand::MO_Undef);
-    return Op;
-  }
-
   const MachineOperand &operator=(const MachineOperand &MO) {
     OpKind   = MO.OpKind;
     IsDef    = MO.IsDef;