diff --git a/lib/CodeGen/MachineCSE.cpp b/lib/CodeGen/MachineCSE.cpp
index 92e2299ec62..272b54dea1f 100644
--- a/lib/CodeGen/MachineCSE.cpp
+++ b/lib/CodeGen/MachineCSE.cpp
@@ -54,6 +54,11 @@ namespace {
       AU.addPreserved<MachineDominatorTree>();
     }
 
+    virtual void releaseMemory() {
+      ScopeMap.clear();
+      Exps.clear();
+    }
+
   private:
     const unsigned LookAheadLimit;
     typedef ScopedHashTableScope<MachineInstr*, unsigned,
@@ -101,7 +106,7 @@ bool MachineCSE::PerformTrivialCoalescing(MachineInstr *MI,
     unsigned Reg = MO.getReg();
     if (!Reg || TargetRegisterInfo::isPhysicalRegister(Reg))
       continue;
-    if (!MRI->hasOneUse(Reg))
+    if (!MRI->hasOneNonDBGUse(Reg))
       // Only coalesce single use copies. This ensure the copy will be
       // deleted.
       continue;
@@ -469,6 +474,8 @@ bool MachineCSE::PerformCSE(MachineDomTreeNode *Node) {
   DenseMap<MachineDomTreeNode*, MachineDomTreeNode*> ParentMap;
   DenseMap<MachineDomTreeNode*, unsigned> OpenChildren;
 
+  CurrVN = 0;
+
   // Perform a DFS walk to determine the order of visit.
   WorkList.push_back(Node);
   do {