Merge revision 3813 to 3930 from bleeding_edge to partial snapshots branch.

src/ast.h

Index: src/ast.h
===================================================================
--- src/ast.h	(revision 3935)
+++ src/ast.h	(working copy)
@@ -1,4 +1,4 @@
-// Copyright 2006-2008 the V8 project authors. All rights reserved.
+// 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:
@@ -102,6 +102,7 @@
 // Forward declarations
 class TargetCollector;
 class MaterializedLiteral;
+class DefinitionInfo;
 
 #define DEF_FORWARD_DECLARATION(type) class type;
 AST_NODE_LIST(DEF_FORWARD_DECLARATION)
@@ -182,7 +183,7 @@
 
   static const int kNoLabel = -1;
 
-  Expression() : num_(kNoLabel) {}
+  Expression() : num_(kNoLabel), def_(NULL), defined_vars_(NULL) {}
 
   virtual Expression* AsExpression()  { return this; }
 
@@ -193,6 +194,15 @@
   // names because [] for string objects is handled only by keyed ICs.
   virtual bool IsPropertyName() { return false; }
 
+  // True if the expression does not have (evaluated) subexpressions.
+  // Function literals are leaves because their subexpressions are not
+  // evaluated.
+  virtual bool IsLeaf() { return false; }
+
+  // True if the expression has no side effects and is safe to
+  // evaluate out of order.
+  virtual bool IsTrivial() { return false; }
+
   // Mark the expression as being compiled as an expression
   // statement. This is used to transform postfix increments to
   // (faster) prefix increments.
@@ -206,9 +216,20 @@
   // AST node numbering ordered by evaluation order.
   void set_num(int n) { num_ = n; }
 
+  // Data flow information.
+  DefinitionInfo* var_def() { return def_; }
+  void set_var_def(DefinitionInfo* def) { def_ = def; }
+
+  ZoneList<DefinitionInfo*>* defined_vars() { return defined_vars_; }
+  void set_defined_vars(ZoneList<DefinitionInfo*>* defined_vars) {
+    defined_vars_ = defined_vars;
+  }
+
  private:
   StaticType type_;
   int num_;
+  DefinitionInfo* def_;
+  ZoneList<DefinitionInfo*>* defined_vars_;
 };
 
 
@@ -720,6 +741,9 @@
     return false;
   }
 
+  virtual bool IsLeaf() { return true; }
+  virtual bool IsTrivial() { return true; }
+
   // Identity testers.
   bool IsNull() const { return handle_.is_identical_to(Factory::null_value()); }
   bool IsTrue() const { return handle_.is_identical_to(Factory::true_value()); }
@@ -802,6 +826,8 @@
   virtual ObjectLiteral* AsObjectLiteral() { return this; }
   virtual void Accept(AstVisitor* v);
 
+  virtual bool IsLeaf() { return properties()->is_empty(); }
+
   Handle<FixedArray> constant_properties() const {
     return constant_properties_;
   }
@@ -825,6 +851,8 @@
 
   virtual void Accept(AstVisitor* v);
 
+  virtual bool IsLeaf() { return true; }
+
   Handle<String> pattern() const { return pattern_; }
   Handle<String> flags() const { return flags_; }
 
@@ -849,6 +877,8 @@
   virtual void Accept(AstVisitor* v);
   virtual ArrayLiteral* AsArrayLiteral() { return this; }
 
+  virtual bool IsLeaf() { return values()->is_empty(); }
+
   Handle<FixedArray> constant_elements() const { return constant_elements_; }
   ZoneList<Expression*>* values() const { return values_; }
 
@@ -896,6 +926,15 @@
     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(); }
+
   bool IsVariable(Handle<String> n) {
     return !is_this() && name().is_identical_to(n);
   }
@@ -981,6 +1020,8 @@
   // Type testing & conversion
   virtual Slot* AsSlot() { return this; }
 
+  virtual bool IsLeaf() { return true; }
+
   // Accessors
   Variable* var() const { return var_; }
   Type type() const { return type_; }
@@ -1337,6 +1378,8 @@
   // Type testing & conversion
   virtual FunctionLiteral* AsFunctionLiteral()  { return this; }
 
+  virtual bool IsLeaf() { return true; }
+
   Handle<String> name() const  { return name_; }
   Scope* scope() const  { return scope_; }
   ZoneList<Statement*>* body() const  { return body_; }
@@ -1403,6 +1446,8 @@
 
   Handle<JSFunction> boilerplate() const { return boilerplate_; }
 
+  virtual bool IsLeaf() { return true; }
+
   virtual void Accept(AstVisitor* v);
 
  private:
@@ -1413,6 +1458,7 @@
 class ThisFunction: public Expression {
  public:
   virtual void Accept(AstVisitor* v);
+  virtual bool IsLeaf() { return true; }
 };