Unweaken vtables as per http://llvm.org/docs/CodingStandards.html#ll_virtual_anch

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@146960 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/Transforms/Utils/SimplifyIndVar.h

@@ -33,6 +33,7 @@ class ScalarEvolution;
 /// Interface for visiting interesting IV users that are recognized but not
 /// simplified by this utility.
 class IVVisitor {
+  virtual void anchor();
 public:
   virtual ~IVVisitor() {}
   virtual void visitCast(CastInst *Cast) = 0;