Add a comment about DepthFirstIterator's skipchildren behavior

llvm-svn: 236904

llvm/include/llvm/ADT/DepthFirstIterator.h

@@ -159,8 +159,10 @@ public:
     return *this;
   }
 
-  // skips all children of the current node and traverses to next node
-  //
+  /// \brief Skips all children of the current node and traverses to next node
+  ///
+  /// Note: This function takes care of incrementing the iterator. If you
+  /// always increment and call this function, you risk walking off the end.
   df_iterator &skipChildren() {
     VisitStack.pop_back();
     if (!VisitStack.empty())