Fix GVN for polymorphic loads....

src/hydrogen-instructions.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 2531 matching lines @@
     return cell_.is_identical_to(b->cell());
   }
 
  private:
   Handle<JSGlobalPropertyCell> cell_;
 };
 
 
 class HLoadNamedField: public HUnaryOperation {
  public:
   HLoadNamedField(HValue* object, bool is_in_object, int offset)

[Kevin Millikin (Chromium), 2010/12/20 12:34:34]

I'd rather pass is_polymorphic to the constructor and get rid of
set_is_polymorphic completely.

The way it's written, it's effectively a default parameter value (slightly worse
because it's artificially mutable), and more verbose too.

       : HUnaryOperation(object),
         is_in_object_(is_in_object),
-        offset_(offset) {
+        offset_(offset),
+        is_polymorphic_(false) {
     set_representation(Representation::Tagged());
     SetFlag(kUseGVN);
     if (is_in_object) {
       SetFlag(kDependsOnInobjectFields);
     } else {
       SetFlag(kDependsOnBackingStoreFields);
     }
   }
 
   HValue* object() const { return OperandAt(0); }
   bool is_in_object() const { return is_in_object_; }
   int offset() const { return offset_; }
 
+  bool is_polymorphic() const { return is_polymorphic_; }
+  void set_is_polymorphic(bool b) { is_polymorphic_ = b; }
+
   virtual Representation RequiredInputRepresentation(int index) const {
     return Representation::Tagged();
   }
   virtual void PrintDataTo(StringStream* stream) const;
 
   DECLARE_CONCRETE_INSTRUCTION(LoadNamedField, "load_named_field")
 
  protected:
   virtual bool DataEquals(HValue* other) const {
     HLoadNamedField* b = HLoadNamedField::cast(other);
     return is_in_object_ == b->is_in_object_ && offset_ == b->offset_;
   }
 
  private:
   bool is_in_object_;
   int offset_;
+  bool is_polymorphic_;
 };
 
 
 class HLoadNamedGeneric: public HUnaryOperation {
  public:
   HLoadNamedGeneric(HValue* object, Handle<Object> name)
       : HUnaryOperation(object), name_(name) {
     set_representation(Representation::Tagged());
     SetFlagMask(AllSideEffects());
   }
@@ skipping 345 matching lines @@
   HValue* object() const { return left(); }
   HValue* key() const { return right(); }
 };
 
 #undef DECLARE_INSTRUCTION
 #undef DECLARE_CONCRETE_INSTRUCTION
 
 } }  // namespace v8::internal
 
 #endif  // V8_HYDROGEN_INSTRUCTIONS_H_