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 "src/zone-containers.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 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:
  Reducer() {}
  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); }
 
 private:
  DISALLOW_COPY_AND_ASSIGN(Reducer);
};
 
 
// Performs an iterative reduction of a node graph.
class GraphReducer 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:
  Graph* graph_;
  ZoneVector<Reducer*> reducers_;
 
  DISALLOW_COPY_AND_ASSIGN(GraphReducer);
};
 
}  // namespace compiler
}  // namespace internal
}  // namespace v8
 
#endif  // V8_COMPILER_GRAPH_REDUCER_H_