diff --git a/lib/CodeGen/LiveDebugVariables.cpp b/lib/CodeGen/LiveDebugVariables.cpp
index 900dc01..20e997a 100644
--- a/lib/CodeGen/LiveDebugVariables.cpp
+++ b/lib/CodeGen/LiveDebugVariables.cpp
@@ -101,6 +101,10 @@
   void insertDebugValue(MachineBasicBlock *MBB, SlotIndex Idx, unsigned LocNo,
                         LiveIntervals &LIS, const TargetInstrInfo &TII);
 
+  /// insertDebugKill - Insert an undef DBG_VALUE into MBB at Idx.
+  void insertDebugKill(MachineBasicBlock *MBB, SlotIndex Idx,
+                       LiveIntervals &LIS, const TargetInstrInfo &TII);
+
 public:
   /// UserValue - Create a new UserValue.
   UserValue(const MDNode *var, unsigned o, DebugLoc L, 
@@ -748,6 +752,13 @@
     .addOperand(Loc).addImm(offset).addMetadata(variable);
 }
 
+void UserValue::insertDebugKill(MachineBasicBlock *MBB, SlotIndex Idx,
+                               LiveIntervals &LIS, const TargetInstrInfo &TII) {
+  MachineBasicBlock::iterator I = findInsertLocation(MBB, Idx, LIS);
+  BuildMI(*MBB, I, findDebugLoc(), TII.get(TargetOpcode::DBG_VALUE)).addReg(0)
+    .addImm(offset).addMetadata(variable);
+}
+
 void UserValue::emitDebugValues(VirtRegMap *VRM, LiveIntervals &LIS,
                                 const TargetInstrInfo &TII) {
   MachineFunction::iterator MFEnd = VRM->getMachineFunction().end();
@@ -779,6 +790,12 @@
       break;
 
     ++I;
+    if (Stop == MBBEnd)
+      continue;
+    // The current interval ends before MBB.
+    // Insert a kill if there is a gap.
+    if (!I.valid() || I.start() > Stop)
+      insertDebugKill(MBB, Stop, LIS, TII);
   }
 }