Free memory when not in use

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@1618 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/Analysis/CallGraph.h

@@ -122,6 +122,11 @@ public:
     Provided.push_back(ID);
   }
 
+  // releaseMemory - Data structures can be large, so free memory agressively.
+  virtual void releaseMemory() {
+    destroy();
+  }
+
 private:   // Implementation of CallGraph construction
   void destroy();