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      1 // Copyright 2014 the V8 project authors. All rights reserved.
      2 // Use of this source code is governed by a BSD-style license that can be
      3 // found in the LICENSE file.
      4 
      5 #ifndef V8_COMPILER_GRAPH_REDUCER_H_
      6 #define V8_COMPILER_GRAPH_REDUCER_H_
      7 
      8 #include "src/zone-containers.h"
      9 
     10 namespace v8 {
     11 namespace internal {
     12 namespace compiler {
     13 
     14 // Forward declarations.
     15 class Graph;
     16 class Node;
     17 
     18 
     19 // Represents the result of trying to reduce a node in the graph.
     20 class Reduction FINAL {
     21  public:
     22   explicit Reduction(Node* replacement = NULL) : replacement_(replacement) {}
     23 
     24   Node* replacement() const { return replacement_; }
     25   bool Changed() const { return replacement() != NULL; }
     26 
     27  private:
     28   Node* replacement_;
     29 };
     30 
     31 
     32 // A reducer can reduce or simplify a given node based on its operator and
     33 // inputs. This class functions as an extension point for the graph reducer for
     34 // language-specific reductions (e.g. reduction based on types or constant
     35 // folding of low-level operators) can be integrated into the graph reduction
     36 // phase.
     37 class Reducer {
     38  public:
     39   Reducer() {}
     40   virtual ~Reducer() {}
     41 
     42   // Try to reduce a node if possible.
     43   virtual Reduction Reduce(Node* node) = 0;
     44 
     45   // Helper functions for subclasses to produce reductions for a node.
     46   static Reduction NoChange() { return Reduction(); }
     47   static Reduction Replace(Node* node) { return Reduction(node); }
     48   static Reduction Changed(Node* node) { return Reduction(node); }
     49 
     50  private:
     51   DISALLOW_COPY_AND_ASSIGN(Reducer);
     52 };
     53 
     54 
     55 // Performs an iterative reduction of a node graph.
     56 class GraphReducer FINAL {
     57  public:
     58   explicit GraphReducer(Graph* graph);
     59 
     60   Graph* graph() const { return graph_; }
     61 
     62   void AddReducer(Reducer* reducer) { reducers_.push_back(reducer); }
     63 
     64   // Reduce a single node.
     65   void ReduceNode(Node* node);
     66   // Reduce the whole graph.
     67   void ReduceGraph();
     68 
     69  private:
     70   Graph* graph_;
     71   ZoneVector<Reducer*> reducers_;
     72 
     73   DISALLOW_COPY_AND_ASSIGN(GraphReducer);
     74 };
     75 
     76 }  // namespace compiler
     77 }  // namespace internal
     78 }  // namespace v8
     79 
     80 #endif  // V8_COMPILER_GRAPH_REDUCER_H_
     81