[turbofan] Smartify the GraphReducer.

src/compiler/graph-reducer.h

 // Copyright 2014 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_COMPILER_GRAPH_REDUCER_H_
 #define V8_COMPILER_GRAPH_REDUCER_H_
 
 #include "src/zone-containers.h"
 
 namespace v8 {
@@ skipping 38 matching lines @@
 
  private:
   DISALLOW_COPY_AND_ASSIGN(Reducer);
 };
 
 
 // Performs an iterative reduction of a node graph.
 class GraphReducer FINAL {
  public:
   explicit GraphReducer(Graph* graph);
+  GraphReducer(Graph* graph, Zone* zone);
 
   Graph* graph() const { return graph_; }
 
-  void AddReducer(Reducer* reducer) { reducers_.push_back(reducer); }
+  void AddReducer(Reducer* reducer);
 
   // Reduce a single node.
-  void ReduceNode(Node* node);
+  void ReduceNode(Node* const);
   // Reduce the whole graph.
   void ReduceGraph();
 
  private:
+  enum class State : uint8_t;
+
+  // Reduce a single node.
+  Reduction Reduce(Node* const);
+  // Reduce the node on top of the stack.
+  void ReduceTop();
+
+  // Node stack operations.
+  void Pop();
+  void Push(Node* const);
+  Node* Top() const;
+
+  // Revisit queue operations.
+  bool Recurse(Node* const);
+  void Revisit(Node* const);
+
   Graph* graph_;
   ZoneVector<Reducer*> reducers_;
+  ZoneStack<Node*> revisit_;
+  ZoneStack<Node*> stack_;
+  ZoneDeque<State> state_;
 
   DISALLOW_COPY_AND_ASSIGN(GraphReducer);
 };
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_COMPILER_GRAPH_REDUCER_H_