diff --git a/llvm/lib/CodeGen/MachineInstr.cpp b/llvm/lib/CodeGen/MachineInstr.cpp
index 79939d0..e3df010 100644
--- a/llvm/lib/CodeGen/MachineInstr.cpp
+++ b/llvm/lib/CodeGen/MachineInstr.cpp
@@ -993,6 +993,54 @@
   return NULL;
 }
 
+const TargetRegisterClass *MachineInstr::getRegClassConstraintEffectForVReg(
+    unsigned Reg, const TargetRegisterClass *CurRC, const TargetInstrInfo *TII,
+    const TargetRegisterInfo *TRI, bool ExploreBundle) const {
+  // Check every operands inside the bundle if we have
+  // been asked to.
+  if (ExploreBundle)
+    for (ConstMIBundleOperands OpndIt(this); OpndIt.isValid() && CurRC;
+         ++OpndIt)
+      CurRC = OpndIt->getParent()->getRegClassConstraintEffectForVRegImpl(
+          OpndIt.getOperandNo(), Reg, CurRC, TII, TRI);
+  else
+    // Otherwise, just check the current operands.
+    for (ConstMIOperands OpndIt(this); OpndIt.isValid() && CurRC; ++OpndIt)
+      CurRC = getRegClassConstraintEffectForVRegImpl(OpndIt.getOperandNo(), Reg,
+                                                     CurRC, TII, TRI);
+  return CurRC;
+}
+
+const TargetRegisterClass *MachineInstr::getRegClassConstraintEffectForVRegImpl(
+    unsigned OpIdx, unsigned Reg, const TargetRegisterClass *CurRC,
+    const TargetInstrInfo *TII, const TargetRegisterInfo *TRI) const {
+  assert(CurRC && "Invalid initial register class");
+  // Check if Reg is constrained by some of its use/def from MI.
+  const MachineOperand &MO = getOperand(OpIdx);
+  if (!MO.isReg() || MO.getReg() != Reg)
+    return CurRC;
+  // If yes, accumulate the constraints through the operand.
+  return getRegClassConstraintEffect(OpIdx, CurRC, TII, TRI);
+}
+
+const TargetRegisterClass *MachineInstr::getRegClassConstraintEffect(
+    unsigned OpIdx, const TargetRegisterClass *CurRC,
+    const TargetInstrInfo *TII, const TargetRegisterInfo *TRI) const {
+  const TargetRegisterClass *OpRC = getRegClassConstraint(OpIdx, TII, TRI);
+  const MachineOperand &MO = getOperand(OpIdx);
+  assert(MO.isReg() &&
+         "Cannot get register constraints for non-register operand");
+  assert(CurRC && "Invalid initial register class");
+  if (unsigned SubIdx = MO.getSubReg()) {
+    if (OpRC)
+      CurRC = TRI->getMatchingSuperRegClass(CurRC, OpRC, SubIdx);
+    else
+      CurRC = TRI->getSubClassWithSubReg(CurRC, SubIdx);
+  } else if (OpRC)
+    CurRC = TRI->getCommonSubClass(CurRC, OpRC);
+  return CurRC;
+}
+
 /// Return the number of instructions inside the MI bundle, not counting the
 /// header instruction.
 unsigned MachineInstr::getBundleSize() const {