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:
replacement_(replacement)22   explicit Reduction(Node* replacement = NULL) : replacement_(replacement) {}
23 
replacement()24   Node* replacement() const { return replacement_; }
Changed()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:
Reducer()39   Reducer() {}
~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.
NoChange()46   static Reduction NoChange() { return Reduction(); }
Replace(Node * node)47   static Reduction Replace(Node* node) { return Reduction(node); }
Changed(Node * 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 
graph()60   Graph* graph() const { return graph_; }
61 
AddReducer(Reducer * reducer)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