Use the property load IC for accessing the array length.

src/hydrogen-instructions.h

 // Copyright 2012 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 2149 matching lines @@
   virtual bool DataEquals(HValue* other) { return true; }
 
  private:
   virtual bool IsDeletable() const { return true; }
 };
 
 
 class HCheckMaps: public HTemplateInstruction<2> {
  public:
   HCheckMaps(HValue* value, Handle<Map> map, Zone* zone,
-             HValue* typecheck = NULL) {
+             HValue* typecheck = NULL,
+             CompareMapMode mode = REQUIRE_EXACT_MAP) : mode_(mode) {
     SetOperandAt(0, value);
     // If callers don't depend on a typecheck, they can pass in NULL. In that
     // case we use a copy of the |value| argument as a dummy value.
     SetOperandAt(1, typecheck != NULL ? typecheck : value);
     set_representation(Representation::Tagged());
     SetFlag(kUseGVN);
     SetGVNFlag(kDependsOnMaps);
     SetGVNFlag(kDependsOnElementsKind);
     map_set()->Add(map, zone);
   }
-  HCheckMaps(HValue* value, SmallMapList* maps, Zone* zone) {
+  HCheckMaps(HValue* value, SmallMapList* maps, Zone* zone,
+             CompareMapMode mode = REQUIRE_EXACT_MAP) : mode_(mode) {
     SetOperandAt(0, value);
     SetOperandAt(1, value);
     set_representation(Representation::Tagged());
     SetFlag(kUseGVN);
     SetGVNFlag(kDependsOnMaps);
     SetGVNFlag(kDependsOnElementsKind);
     for (int i = 0; i < maps->length(); i++) {
       map_set()->Add(maps->at(i), zone);
     }
     map_set()->Sort();
@@ skipping 23 matching lines @@
   }
 
   virtual Representation RequiredInputRepresentation(int index) {
     return Representation::Tagged();
   }
   virtual void PrintDataTo(StringStream* stream);
   virtual HType CalculateInferredType();
 
   HValue* value() { return OperandAt(0); }
   SmallMapList* map_set() { return &map_set_; }
+  CompareMapMode mode() { return mode_; }
 
   DECLARE_CONCRETE_INSTRUCTION(CheckMaps)
 
  protected:
   virtual bool DataEquals(HValue* other) {
     HCheckMaps* b = HCheckMaps::cast(other);
     // Relies on the fact that map_set has been sorted before.
     if (map_set()->length() != b->map_set()->length()) return false;
     for (int i = 0; i < map_set()->length(); i++) {
       if (!map_set()->at(i).is_identical_to(b->map_set()->at(i))) return false;
     }
     return true;
   }
 
  private:
   SmallMapList map_set_;
+  CompareMapMode mode_;
 };
 
 
 class HCheckFunction: public HUnaryOperation {
  public:
   HCheckFunction(HValue* value, Handle<JSFunction> function)
       : HUnaryOperation(value), target_(function) {
     set_representation(Representation::Tagged());
     SetFlag(kUseGVN);
   }
@@ skipping 3031 matching lines @@
   virtual bool IsDeletable() const { return true; }
 };
 
 
 #undef DECLARE_INSTRUCTION
 #undef DECLARE_CONCRETE_INSTRUCTION
 
 } }  // namespace v8::internal
 
 #endif  // V8_HYDROGEN_INSTRUCTIONS_H_