Have the flow graph builder collect definitions.

src/data-flow.h

 // Copyright 2010 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 345 matching lines @@
   Node* successor_;
 
   DISALLOW_COPY_AND_ASSIGN(JoinNode);
 };
 
 
 // Construct a flow graph from a function literal.  Build pre- and postorder
 // traversal orders as a byproduct.
 class FlowGraphBuilder: public AstVisitor {
  public:
-  FlowGraphBuilder() : global_exit_(NULL), preorder_(4), postorder_(4) {}
+  FlowGraphBuilder()
+      : global_exit_(NULL),
+        preorder_(4),
+        postorder_(4),
+        definitions_(4) {
+  }
 
   void Build(FunctionLiteral* lit);
 
   FlowGraph* graph() { return &graph_; }
 
   ZoneList<Node*>* postorder() { return &postorder_; }
 
  private:
   ExitNode* global_exit() { return global_exit_; }
 
   // AST node visit functions.
 #define DECLARE_VISIT(type) virtual void Visit##type(type* node);
   AST_NODE_LIST(DECLARE_VISIT)
 #undef DECLARE_VISIT
 
   FlowGraph graph_;
   ExitNode* global_exit_;
   ZoneList<Node*> preorder_;
   ZoneList<Node*> postorder_;
 
+  // The flow graph builder collects a list of definitions (assignments and
+  // count operations) to stack-allocated variables to use for reaching
+  // definitions analysis.
+  ZoneList<AstNode*> definitions_;
+
   DISALLOW_COPY_AND_ASSIGN(FlowGraphBuilder);
 };
 
 
 // This class is used to number all expressions in the AST according to
 // their evaluation order (post-order left-to-right traversal).
 class AstLabeler: public AstVisitor {
  public:
   AstLabeler() : next_number_(0) {}
 
@@ skipping 65 matching lines @@
   VarUseMap live_vars_;
 
   DISALLOW_COPY_AND_ASSIGN(LivenessAnalyzer);
 };
 
 
 } }  // namespace v8::internal
 
 
 #endif  // V8_DATAFLOW_H_