diff --git a/lib/CodeGen/LiveDebugVariables.cpp b/lib/CodeGen/LiveDebugVariables.cpp
index 388f58f..7d5646b 100644
--- a/lib/CodeGen/LiveDebugVariables.cpp
+++ b/lib/CodeGen/LiveDebugVariables.cpp
@@ -329,12 +329,13 @@
   void computeIntervals();
 
 public:
-  LDVImpl(LiveDebugVariables *ps) : pass(*ps), EmitDone(false),
-                                    ModifiedMF(false) {}
+  LDVImpl(LiveDebugVariables *ps)
+      : pass(*ps), MF(nullptr), EmitDone(false), ModifiedMF(false) {}
   bool runOnMachineFunction(MachineFunction &mf);
 
   /// clear - Release all memory.
   void clear() {
+    MF = nullptr;
     userValues.clear();
     virtRegToEqClass.clear();
     userVarMap.clear();
@@ -693,11 +694,11 @@
 }
 
 bool LDVImpl::runOnMachineFunction(MachineFunction &mf) {
+  clear();
   MF = &mf;
   LIS = &pass.getAnalysis<LiveIntervals>();
   MDT = &pass.getAnalysis<MachineDominatorTree>();
   TRI = mf.getTarget().getRegisterInfo();
-  clear();
   LS.initialize(mf);
   DEBUG(dbgs() << "********** COMPUTING LIVE DEBUG VARIABLES: "
                << mf.getName() << " **********\n");
@@ -712,6 +713,8 @@
 bool LiveDebugVariables::runOnMachineFunction(MachineFunction &mf) {
   if (!EnableLDV)
     return false;
+  if (!FunctionDIs.count(mf.getFunction()))
+    return false;
   if (!pImpl)
     pImpl = new LDVImpl(this);
   return static_cast<LDVImpl*>(pImpl)->runOnMachineFunction(mf);
@@ -974,6 +977,8 @@
 
 void LDVImpl::emitDebugValues(VirtRegMap *VRM) {
   DEBUG(dbgs() << "********** EMITTING LIVE DEBUG VARIABLES **********\n");
+  if (!MF)
+    return;
   const TargetInstrInfo *TII = MF->getTarget().getInstrInfo();
   for (unsigned i = 0, e = userValues.size(); i != e; ++i) {
     DEBUG(userValues[i]->print(dbgs(), &MF->getTarget()));
@@ -988,6 +993,10 @@
     static_cast<LDVImpl*>(pImpl)->emitDebugValues(VRM);
 }
 
+bool LiveDebugVariables::doInitialization(Module &M) {
+  FunctionDIs = makeSubprogramMap(M);
+  return Pass::doInitialization(M);
+}
 
 #ifndef NDEBUG
 void LiveDebugVariables::dump() {