Add a simple clear() method

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@24543 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/Analysis/AliasSetTracker.h

@@ -290,6 +290,11 @@ public:
   bool remove(InvokeInst *II) { return remove(CallSite(II)); }
   bool remove(Instruction *I);
   void remove(AliasSet &AS);
+  
+  void clear() {
+    PointerMap.clear();
+    AliasSets.clear();
+  }
 
   /// getAliasSets - Return the alias sets that are active.
   ///