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src/compiler/graph-reducer.h

Index: src/compiler/graph-reducer.h
diff --git a/src/compiler/graph-reducer.h b/src/compiler/graph-reducer.h
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+// 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 <list>
+
+#include "src/zone-allocator.h"
+
+namespace v8 {
+namespace internal {
+namespace compiler {
+
+// Forward declarations.
+class Graph;
+class Node;
+
+
+// Represents the result of trying to reduce a node in the graph.
+class Reduction V8_FINAL {
+ public:
+  explicit Reduction(Node* replacement = NULL) : replacement_(replacement) {}
+
+  Node* replacement() const { return replacement_; }
+  bool Changed() const { return replacement() != NULL; }
+
+ private:
+  Node* replacement_;
+};
+
+
+// A reducer can reduce or simplify a given node based on its operator and
+// inputs. This class functions as an extension point for the graph reducer for
+// language-specific reductions (e.g. reduction based on types or constant
+// folding of low-level operators) can be integrated into the graph reduction
+// phase.
+class Reducer {
+ public:
+  virtual ~Reducer() {}
+
+  // Try to reduce a node if possible.
+  virtual Reduction Reduce(Node* node) = 0;
+
+  // Helper functions for subclasses to produce reductions for a node.
+  static Reduction NoChange() { return Reduction(); }
+  static Reduction Replace(Node* node) { return Reduction(node); }
+  static Reduction Changed(Node* node) { return Reduction(node); }
+};
+
+
+// Performs an iterative reduction of a node graph.
+class GraphReducer V8_FINAL {
+ public:
+  explicit GraphReducer(Graph* graph);
+
+  Graph* graph() const { return graph_; }
+
+  void AddReducer(Reducer* reducer) { reducers_.push_back(reducer); }
+
+  // Reduce a single node.
+  void ReduceNode(Node* node);
+  // Reduce the whole graph.
+  void ReduceGraph();
+
+ private:
+  typedef std::list<Reducer*, zone_allocator<Reducer*> > Reducers;
+
+  Graph* graph_;
+  Reducers reducers_;
+};
+}
+}
+}  // namespace v8::internal::compiler
+
+#endif  // V8_COMPILER_GRAPH_REDUCER_H_