remove useless declaration, clone_nodes -> clone_data_nodes, add asse…

…rtion to prevent double-usage of clone()

src/hotspot/share/opto/loopnode.hpp

@@ -35,7 +35,6 @@
 class CmpNode;
 class BaseCountedLoopEndNode;
 class CountedLoopNode;
-class DataInputGraph;
 class IdealLoopTree;
 class LoopNode;
 class Node;
@@ -1906,14 +1905,15 @@ class DataNodeGraph : public StackObj {
 
  private:
   void clone(Node* node, Node* new_ctrl);
-  void clone_nodes(Node* new_ctrl);
+  void clone_data_nodes(Node* new_ctrl);
   void rewire_clones_to_cloned_inputs();
 
  public:
   // Clone the provided data node collection and rewire the clones in such a way to create an identical graph copy.
   // Set `new_ctrl` as ctrl for the cloned nodes.
   const OrigToNewHashtable& clone(Node* new_ctrl) {
-    clone_nodes(new_ctrl);
+    assert(_orig_to_new.number_of_entries() == 0, "should not call this method twice in a row");
+    clone_data_nodes(new_ctrl);
     rewire_clones_to_cloned_inputs();
     return _orig_to_new;
   }

src/hotspot/share/opto/loopopts.cpp

@@ -4496,8 +4496,7 @@ void PhaseIdealLoop::move_unordered_reduction_out_of_loop(IdealLoopTree* loop) {
   }
 }
 
-// Clone all nodes in _data_nodes.
-void DataNodeGraph::clone_nodes(Node* new_ctrl) {
+void DataNodeGraph::clone_data_nodes(Node* new_ctrl) {
   for (uint i = 0; i < _data_nodes.size(); i++) {
     clone(_data_nodes[i], new_ctrl);
   }