diff --git a/lib/CodeGen/MachineCSE.cpp b/lib/CodeGen/MachineCSE.cpp
index 39a50d2078f..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,
@@ -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 {