Add an assigned variables analysis....

src/ast.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 119 matching lines @@
   virtual Expression* AsExpression() { return NULL; }
   virtual Literal* AsLiteral() { return NULL; }
   virtual Slot* AsSlot() { return NULL; }
   virtual VariableProxy* AsVariableProxy() { return NULL; }
   virtual Property* AsProperty() { return NULL; }
   virtual Call* AsCall() { return NULL; }
   virtual TargetCollector* AsTargetCollector() { return NULL; }
   virtual BreakableStatement* AsBreakableStatement() { return NULL; }
   virtual IterationStatement* AsIterationStatement() { return NULL; }
   virtual UnaryOperation* AsUnaryOperation() { return NULL; }
+  virtual CountOperation* AsCountOperation() { return NULL; }
   virtual BinaryOperation* AsBinaryOperation() { return NULL; }
   virtual Assignment* AsAssignment() { return NULL; }
   virtual FunctionLiteral* AsFunctionLiteral() { return NULL; }
   virtual MaterializedLiteral* AsMaterializedLiteral() { return NULL; }
   virtual ObjectLiteral* AsObjectLiteral() { return NULL; }
   virtual ArrayLiteral* AsArrayLiteral() { return NULL; }
   virtual CompareOperation* AsCompareOperation() { return NULL; }
 
   int num() { return num_; }
   void set_num(int n) { num_ = n; }
 
  private:
   // Support for ast node numbering.
   int num_;
 };
 
 
 class Statement: public AstNode {
  public:
   Statement() : statement_pos_(RelocInfo::kNoPosition) {}
 
   virtual Statement* AsStatement()  { return this; }
   virtual ReturnStatement* AsReturnStatement() { return NULL; }
 
+  virtual Assignment* StatementAsSimpleAssignment() { return NULL; }
+  virtual CountOperation* StatementAsCountOperation() { return NULL; }
+
   bool IsEmpty() { return AsEmptyStatement() != NULL; }
 
   void set_statement_pos(int statement_pos) { statement_pos_ = statement_pos; }
   int statement_pos() const { return statement_pos_; }
 
  private:
   int statement_pos_;
 };
 
 
@@ skipping 140 matching lines @@
 
 class Block: public BreakableStatement {
  public:
   Block(ZoneStringList* labels, int capacity, bool is_initializer_block)
       : BreakableStatement(labels, TARGET_FOR_NAMED_ONLY),
         statements_(capacity),
         is_initializer_block_(is_initializer_block) { }
 
   virtual void Accept(AstVisitor* v);
 
+  virtual Assignment* StatementAsSimpleAssignment() {
+    if (statements_.length() != 1) return NULL;
+    return statements_[0]->StatementAsSimpleAssignment();
+  }
+
+  virtual CountOperation* StatementAsCountOperation() {
+    if (statements_.length() != 1) return NULL;
+    return statements_[0]->StatementAsCountOperation();
+  }
+
   void AddStatement(Statement* statement) { statements_.Add(statement); }
 
   ZoneList<Statement*>* statements() { return &statements_; }
   bool is_initializer_block() const  { return is_initializer_block_; }
 
  private:
   ZoneList<Statement*> statements_;
   bool is_initializer_block_;
 };
 
@@ skipping 101 matching lines @@
 };
 
 
 class ForStatement: public IterationStatement {
  public:
   explicit ForStatement(ZoneStringList* labels)
       : IterationStatement(labels),
         init_(NULL),
         cond_(NULL),
         next_(NULL),
-        may_have_function_literal_(true) {
-  }
+        may_have_function_literal_(true),
+        loop_variable_(NULL) {}
 
   void Initialize(Statement* init,
                   Expression* cond,
                   Statement* next,
                   Statement* body) {
     IterationStatement::Initialize(body);
     init_ = init;
     cond_ = cond;
     next_ = next;
   }
 
   virtual void Accept(AstVisitor* v);
 
   Statement* init() const  { return init_; }
   Expression* cond() const  { return cond_; }
   Statement* next() const  { return next_; }
   bool may_have_function_literal() const {
     return may_have_function_literal_;
   }
 
+  bool is_fast_smi_loop() { return loop_variable_ != NULL; }
+  Variable* loop_variable() { return loop_variable_; }
+  void set_loop_variable(Variable* var) { loop_variable_ = var; }
+
  private:
   Statement* init_;
   Expression* cond_;
   Statement* next_;
   // True if there is a function literal subexpression in the condition.
   bool may_have_function_literal_;
+  Variable* loop_variable_;
 
   friend class AstOptimizer;
 };
 
 
 class ForInStatement: public IterationStatement {
  public:
   explicit ForInStatement(ZoneStringList* labels)
       : IterationStatement(labels), each_(NULL), enumerable_(NULL) { }
 
@@ skipping 17 matching lines @@
 class ExpressionStatement: public Statement {
  public:
   explicit ExpressionStatement(Expression* expression)
       : expression_(expression) { }
 
   virtual void Accept(AstVisitor* v);
 
   // Type testing & conversion.
   virtual ExpressionStatement* AsExpressionStatement() { return this; }
 
+  virtual Assignment* StatementAsSimpleAssignment();
+  virtual CountOperation* StatementAsCountOperation();
+
   void set_expression(Expression* e) { expression_ = e; }
   Expression* expression() { return expression_; }
 
  private:
   Expression* expression_;
 };
 
 
 class ContinueStatement: public Statement {
  public:
@@ skipping 437 matching lines @@
     return var_ == NULL ? true : var_->IsValidLeftHandSide();
   }
 
   virtual bool IsLeaf() {
     ASSERT(var_ != NULL);  // Variable must be resolved.
     return var()->is_global() || var()->rewrite()->IsLeaf();
   }
 
   // Reading from a mutable variable is a side effect, but 'this' is
   // immutable.
-  virtual bool IsTrivial() { return is_this(); }
+  virtual bool IsTrivial() { return is_trivial_; }
 
   bool IsVariable(Handle<String> n) {
     return !is_this() && name().is_identical_to(n);
   }
 
   bool IsArguments() {
     Variable* variable = AsVariable();
     return (variable == NULL) ? false : variable->is_arguments();
   }
 
   Handle<String> name() const  { return name_; }
   Variable* var() const  { return var_; }
   bool is_this() const  { return is_this_; }
   bool inside_with() const  { return inside_with_; }
+  bool is_trivial() { return is_trivial_; }
+  void set_is_trivial(bool b) { is_trivial_ = b; }
 
   // Bind this proxy to the variable var.
   void BindTo(Variable* var);
 
  protected:
   Handle<String> name_;
   Variable* var_;  // resolved variable, or NULL
   bool is_this_;
   bool inside_with_;
+  bool is_trivial_;
 
   VariableProxy(Handle<String> name, bool is_this, bool inside_with);
   explicit VariableProxy(bool is_this);
 
   friend class Scope;
 };
 
 
 class VariableProxySentinel: public VariableProxy {
  public:
@@ skipping 238 matching lines @@
 
 class CountOperation: public Expression {
  public:
   CountOperation(bool is_prefix, Token::Value op, Expression* expression)
       : is_prefix_(is_prefix), op_(op), expression_(expression) {
     ASSERT(Token::IsCountOp(op));
   }
 
   virtual void Accept(AstVisitor* v);
 
+  virtual CountOperation* AsCountOperation() { return this; }
+
   bool is_prefix() const { return is_prefix_; }
   bool is_postfix() const { return !is_prefix_; }
   Token::Value op() const { return op_; }
   Token::Value binary_op() {
     return op_ == Token::INC ? Token::ADD : Token::SUB;
   }
   Expression* expression() const { return expression_; }
 
   virtual void MarkAsStatement() { is_prefix_ = true; }
 
@@ skipping 58 matching lines @@
  public:
   Assignment(Token::Value op, Expression* target, Expression* value, int pos)
       : op_(op), target_(target), value_(value), pos_(pos),
         block_start_(false), block_end_(false) {
     ASSERT(Token::IsAssignmentOp(op));
   }
 
   virtual void Accept(AstVisitor* v);
   virtual Assignment* AsAssignment() { return this; }
 
+  Assignment* AsSimpleAssignment() { return !is_compound() ? this : NULL; }
+
   Token::Value binary_op() const;
 
   Token::Value op() const { return op_; }
   Expression* target() const { return target_; }
   Expression* value() const { return value_; }
   int position() { return pos_; }
   // This check relies on the definition order of token in token.h.
   bool is_compound() const { return op() > Token::ASSIGN; }
 
   // An initialization block is a series of statments of the form
@@ skipping 539 matching lines @@
 #undef DEF_VISIT
 
  private:
   bool stack_overflow_;
 };
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_AST_H_