[turbofan] Add TraversalState and GraphTraversal and use them in GraphReducer.

src/compiler/node.h

Index: src/compiler/node.h
diff --git a/src/compiler/node.h b/src/compiler/node.h
index 8a442cedbc7aed407eda1e7f88d6388df58cdba3..d7171cff4a5d32001129df4368c8245942e49335 100644
--- a/src/compiler/node.h
+++ b/src/compiler/node.h
@@ -21,6 +21,8 @@ namespace v8 {
 namespace internal {
 namespace compiler {
 
+typedef uint32_t TraversalState;
+
 class NodeData {
  public:
   const Operator* op() const { return op_; }
@@ -31,9 +33,13 @@ class NodeData {
     return static_cast<IrOpcode::Value>(op_->opcode());
   }
 
+  TraversalState traversal_state() { return traversal_state_; }
+  void set_traversal_state(TraversalState s) { traversal_state_ = s; }
+
  protected:
   const Operator* op_;
   Bounds bounds_;
+  TraversalState traversal_state_;
   explicit NodeData(Zone* zone) {}
 
   friend class NodeProperties;
@@ -51,7 +57,10 @@ class Node FINAL : public GenericNode<NodeData, Node> {
   Node(GenericGraphBase* graph, int input_count, int reserve_input_count)
       : GenericNode<NodeData, Node>(graph, input_count, reserve_input_count) {}
 
-  void Initialize(const Operator* op) { set_op(op); }
+  void Initialize(const Operator* op) {
+    set_op(op);
+    set_traversal_state(0);
+  }
 
   bool IsDead() const { return InputCount() > 0 && InputAt(0) == NULL; }
   void Kill();