Add last use data flow information to the fast code generator....

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 44 matching lines @@
 
   // Traversal number for labelling AST nodes.
   int next_number_;
 
   CompilationInfo* info_;
 
   DISALLOW_COPY_AND_ASSIGN(AstLabeler);
 };
 
 
+class VarUseMap : public HashMap {
+ public:
+  VarUseMap() : HashMap(VarMatch) {}
+
+  ZoneList<Expression*>* Lookup(Variable* var);
+
+ private:
+  static bool VarMatch(void* key1, void* key2) { return key1 == key2; }
+};
+
+
+class DefinitionInfo : public ZoneObject {
+ public:
+  explicit DefinitionInfo() : last_use_(NULL) {}
+
+  Expression* last_use() { return last_use_; }
+  void set_last_use(Expression* expr) { last_use_ = expr; }
+
+ private:
+  Expression* last_use_;
+  Register location_;
+};
+
+
+class LivenessAnalyzer : public AstVisitor {
+ public:
+  LivenessAnalyzer() {}
+
+  void Analyze(FunctionLiteral* fun);
+
+ private:
+  void VisitStatements(ZoneList<Statement*>* stmts);
+
+  void RecordUse(Variable* var, Expression* expr);
+  void RecordDef(Variable* var, Expression* expr);
+
+
+  // AST node visit functions.
+#define DECLARE_VISIT(type) virtual void Visit##type(type* node);
+  AST_NODE_LIST(DECLARE_VISIT)
+#undef DECLARE_VISIT
+
+  // Map for tracking the live variables.
+  VarUseMap live_vars_;
+
+  DISALLOW_COPY_AND_ASSIGN(LivenessAnalyzer);
+};
+
+
 } }  // namespace v8::internal
 
+
 #endif  // V8_DATAFLOW_H_