diff --git a/include/llvm/CodeGen/LivePhysRegs.h b/include/llvm/CodeGen/LivePhysRegs.h
index f44d627d717..6ffd3eeea35 100644
--- a/include/llvm/CodeGen/LivePhysRegs.h
+++ b/include/llvm/CodeGen/LivePhysRegs.h
@@ -93,7 +93,8 @@ public:
   }
 
   /// \brief Removes physical registers clobbered by the regmask operand @p MO.
-  void removeRegsInMask(const MachineOperand &MO);
+  void removeRegsInMask(const MachineOperand &MO,
+        SmallVectorImpl<std::pair<unsigned, const MachineOperand*>> *Clobbers);
 
   /// \brief Returns true if register @p Reg is contained in the set. This also
   /// works if only the super register of @p Reg has been defined, because we
@@ -109,7 +110,11 @@ public:
   /// instruction(bundle): Remove killed-uses, add defs. This is the not
   /// recommended way, because it depends on accurate kill flags. If possible
   /// use stepBackwards() instead of this function.
-  void stepForward(const MachineInstr &MI);
+  /// The clobbers set will be the list of registers either defined or clobbered
+  /// by a regmask.  The operand will identify whether this is a regmask or
+  /// register operand.
+  void stepForward(const MachineInstr &MI,
+        SmallVectorImpl<std::pair<unsigned, const MachineOperand*>> &Clobbers);
 
   /// \brief Adds all live-in registers of basic block @p MBB.
   void addLiveIns(const MachineBasicBlock *MBB) {
diff --git a/lib/CodeGen/IfConversion.cpp b/lib/CodeGen/IfConversion.cpp
index b8799a563fc..938c9cf6039 100644
--- a/lib/CodeGen/IfConversion.cpp
+++ b/lib/CodeGen/IfConversion.cpp
@@ -975,26 +975,18 @@ void IfConverter::RemoveExtraEdges(BBInfo &BBI) {
 /// Behaves like LiveRegUnits::StepForward() but also adds implicit uses to all
 /// values defined in MI which are not live/used by MI.
 static void UpdatePredRedefs(MachineInstr *MI, LivePhysRegs &Redefs) {
-  for (ConstMIBundleOperands Ops(MI); Ops.isValid(); ++Ops) {
-    if (!Ops->isReg() || !Ops->isKill())
-      continue;
-    unsigned Reg = Ops->getReg();
-    if (Reg == 0)
-      continue;
-    Redefs.removeReg(Reg);
-  }
-  for (MIBundleOperands Ops(MI); Ops.isValid(); ++Ops) {
-    if (!Ops->isReg() || !Ops->isDef())
-      continue;
-    unsigned Reg = Ops->getReg();
-    if (Reg == 0 || Redefs.contains(Reg))
-      continue;
-    Redefs.addReg(Reg);
+  SmallVector<std::pair<unsigned, const MachineOperand*>, 4> Clobbers;
+  Redefs.stepForward(*MI, Clobbers);
 
-    MachineOperand &Op = *Ops;
-    MachineInstr *MI = Op.getParent();
-    MachineInstrBuilder MIB(*MI->getParent()->getParent(), MI);
-    MIB.addReg(Reg, RegState::Implicit | RegState::Undef);
+  // Now add the implicit uses for each of the clobbered values.
+  for (auto Reg : Clobbers) {
+    const MachineOperand &Op = *Reg.second;
+    // FIXME: Const cast here is nasty, but better than making StepForward
+    // take a mutable instruction instead of const.
+    MachineInstr *OpMI = const_cast<MachineInstr*>(Op.getParent());
+    MachineInstrBuilder MIB(*OpMI->getParent()->getParent(), OpMI);
+    assert(Op.isReg() && "Register operand required");
+    MIB.addReg(Reg.first, RegState::Implicit | RegState::Undef);
   }
 }
 
@@ -1374,7 +1366,8 @@ bool IfConverter::IfConvertDiamond(BBInfo &BBI, IfcvtKind Kind,
 
   for (MachineBasicBlock::const_iterator I = BBI1->BB->begin(), E = DI1; I != E;
        ++I) {
-    Redefs.stepForward(*I);
+    SmallVector<std::pair<unsigned, const MachineOperand*>, 4> IgnoredClobbers;
+    Redefs.stepForward(*I, IgnoredClobbers);
   }
   BBI.BB->splice(BBI.BB->end(), BBI1->BB, BBI1->BB->begin(), DI1);
   BBI2->BB->erase(BBI2->BB->begin(), DI2);
diff --git a/lib/CodeGen/LivePhysRegs.cpp b/lib/CodeGen/LivePhysRegs.cpp
index 89567eff517..b6369275051 100644
--- a/lib/CodeGen/LivePhysRegs.cpp
+++ b/lib/CodeGen/LivePhysRegs.cpp
@@ -22,12 +22,17 @@ using namespace llvm;
 
 /// \brief Remove all registers from the set that get clobbered by the register
 /// mask.
-void LivePhysRegs::removeRegsInMask(const MachineOperand &MO) {
+/// The clobbers set will be the list of live registers clobbered
+/// by the regmask.
+void LivePhysRegs::removeRegsInMask(const MachineOperand &MO,
+        SmallVectorImpl<std::pair<unsigned, const MachineOperand*>> *Clobbers) {
   SparseSet<unsigned>::iterator LRI = LiveRegs.begin();
   while (LRI != LiveRegs.end()) {
-    if (MO.clobbersPhysReg(*LRI))
+    if (MO.clobbersPhysReg(*LRI)) {
+      if (Clobbers)
+        Clobbers->push_back(std::make_pair(*LRI, &MO));
       LRI = LiveRegs.erase(LRI);
-    else
+    } else
       ++LRI;
   }
 }
@@ -45,7 +50,7 @@ void LivePhysRegs::stepBackward(const MachineInstr &MI) {
         continue;
       removeReg(Reg);
     } else if (O->isRegMask())
-      removeRegsInMask(*O);
+      removeRegsInMask(*O, nullptr);
   }
 
   // Add uses to the set.
@@ -63,8 +68,8 @@ void LivePhysRegs::stepBackward(const MachineInstr &MI) {
 /// killed-uses, add defs. This is the not recommended way, because it depends
 /// on accurate kill flags. If possible use stepBackwards() instead of this
 /// function.
-void LivePhysRegs::stepForward(const MachineInstr &MI) {
-  SmallVector<unsigned, 4> Defs;
+void LivePhysRegs::stepForward(const MachineInstr &MI,
+        SmallVectorImpl<std::pair<unsigned, const MachineOperand*>> &Clobbers) {
   // Remove killed registers from the set.
   for (ConstMIBundleOperands O(&MI); O.isValid(); ++O) {
     if (O->isReg()) {
@@ -73,7 +78,7 @@ void LivePhysRegs::stepForward(const MachineInstr &MI) {
         continue;
       if (O->isDef()) {
         if (!O->isDead())
-          Defs.push_back(Reg);
+          Clobbers.push_back(std::make_pair(Reg, &*O));
       } else {
         if (!O->isKill())
           continue;
@@ -81,12 +86,12 @@ void LivePhysRegs::stepForward(const MachineInstr &MI) {
         removeReg(Reg);
       }
     } else if (O->isRegMask())
-      removeRegsInMask(*O);
+      removeRegsInMask(*O, &Clobbers);
   }
 
   // Add defs to the set.
-  for (unsigned i = 0, e = Defs.size(); i != e; ++i)
-    addReg(Defs[i]);
+  for (auto Reg : Clobbers)
+    addReg(Reg.first);
 }
 
 /// Prin the currently live registers to OS.