diff --git a/lib/CodeGen/MachineInstr.cpp b/lib/CodeGen/MachineInstr.cpp
index e54cd5c..ce0c5e6 100644
--- a/lib/CodeGen/MachineInstr.cpp
+++ b/lib/CodeGen/MachineInstr.cpp
@@ -111,6 +111,25 @@
   Contents.Reg.RegNo = Reg;
 }
 
+void MachineOperand::substVirtReg(unsigned Reg, unsigned SubIdx,
+                                  const TargetRegisterInfo &TRI) {
+  assert(TargetRegisterInfo::isVirtualRegister(Reg));
+  if (SubIdx && getSubReg())
+    SubIdx = TRI.composeSubRegIndices(SubIdx, getSubReg());
+  setReg(Reg);
+  setSubReg(SubIdx);
+}
+
+void MachineOperand::substPhysReg(unsigned Reg, const TargetRegisterInfo &TRI) {
+  assert(TargetRegisterInfo::isPhysicalRegister(Reg));
+  if (getSubReg()) {
+    Reg = TRI.getSubReg(Reg, getSubReg());
+    assert(Reg && "Invalid SubReg for physical register");
+    setSubReg(0);
+  }
+  setReg(Reg);
+}
+
 /// ChangeToImmediate - Replace this operand with a new immediate operand of
 /// the specified value.  If an operand is known to be an immediate already,
 /// the setImm method should be used.