Optimize isFinite and isNaN.

src/ast.h

Index: src/ast.h
diff --git a/src/ast.h b/src/ast.h
index 3d53b5fb0e4c82708f3468a257ec79ecd24b0f54..e36eb9b32182e481fa8f91e749758e61e228c733 100644
--- a/src/ast.h
+++ b/src/ast.h
@@ -320,6 +320,20 @@ class Expression: public AstNode {
 };
 
 
+/**
+ * A sentinel used during pre parsing that represents some expression
+ * that is a valid left hand side without having to actually build
+ * the expression.
+ */
+class ValidLeftHandSideSentinel: public Expression {
+ public:
+  explicit ValidLeftHandSideSentinel(Isolate* isolate) : Expression(isolate) {}
+  virtual bool IsValidLeftHandSide() { return true; }
+  virtual void Accept(AstVisitor* v) { UNREACHABLE(); }
+  virtual bool IsInlineable() const;
+};
+
+
 class BreakableStatement: public Statement {
  public:
   enum Type {
@@ -1160,11 +1174,24 @@ class VariableProxy: public Expression {
                 bool is_this,
                 bool inside_with,
                 int position = RelocInfo::kNoPosition);
+  VariableProxy(Isolate* isolate, bool is_this);
 
   friend class Scope;
 };
 
 
+class VariableProxySentinel: public VariableProxy {
+ public:
+  virtual bool IsValidLeftHandSide() { return !is_this(); }
+
+ private:
+  VariableProxySentinel(Isolate* isolate, bool is_this)
+      : VariableProxy(isolate, is_this) { }
+
+  friend class AstSentinels;
+};
+
+
 class Slot: public Expression {
  public:
   enum Type {
@@ -1322,6 +1349,36 @@ class Call: public Expression {
 };
 
 
+class AstSentinels {
+ public:
+  ~AstSentinels() { }
+
+  // Returns a property singleton property access on 'this'.  Used
+  // during preparsing.
+  Property* this_property() { return &this_property_; }
+  VariableProxySentinel* this_proxy() { return &this_proxy_; }
+  VariableProxySentinel* identifier_proxy() { return &identifier_proxy_; }
+  ValidLeftHandSideSentinel* valid_left_hand_side_sentinel() {
+    return &valid_left_hand_side_sentinel_;
+  }
+  Call* call_sentinel() { return &call_sentinel_; }
+  EmptyStatement* empty_statement() { return &empty_statement_; }
+
+ private:
+  AstSentinels();
+  VariableProxySentinel this_proxy_;
+  VariableProxySentinel identifier_proxy_;
+  ValidLeftHandSideSentinel valid_left_hand_side_sentinel_;
+  Property this_property_;
+  Call call_sentinel_;
+  EmptyStatement empty_statement_;
+
+  friend class Isolate;
+
+  DISALLOW_COPY_AND_ASSIGN(AstSentinels);
+};
+
+
 class CallNew: public Expression {
  public:
   CallNew(Isolate* isolate,