Fix deopts caused by misplaced COW checks.

src/hydrogen-instructions.h

 // Copyright 2011 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 1880 matching lines @@
     return Representation::Tagged();
   }
 
   DECLARE_CONCRETE_INSTRUCTION(LoadExternalArrayPointer)
 
  protected:
   virtual bool DataEquals(HValue* other) { return true; }
 };
 
 
-class HCheckMap: public HUnaryOperation {
+class HCheckMap: public HTemplateInstruction<2> {
  public:
-  HCheckMap(HValue* value, Handle<Map> map)
-      : HUnaryOperation(value), map_(map) {
+  HCheckMap(HValue* value, Handle<Map> map, HValue* typecheck = NULL)
+      : map_(map) {
+    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);
     SetFlag(kDependsOnMaps);
   }
 
   virtual Representation RequiredInputRepresentation(int index) const {
     return Representation::Tagged();
   }
   virtual void PrintDataTo(StringStream* stream);
   virtual HType CalculateInferredType();
 
+  HValue* value() { return OperandAt(0); }
   Handle<Map> map() const { return map_; }
 
   DECLARE_CONCRETE_INSTRUCTION(CheckMap)
 
  protected:
   virtual bool DataEquals(HValue* other) {
     HCheckMap* b = HCheckMap::cast(other);
     return map_.is_identical_to(b->map());
   }
 
@@ skipping 2259 matching lines @@
 
   DECLARE_CONCRETE_INSTRUCTION(In)
 };
 
 #undef DECLARE_INSTRUCTION
 #undef DECLARE_CONCRETE_INSTRUCTION
 
 } }  // namespace v8::internal
 
 #endif  // V8_HYDROGEN_INSTRUCTIONS_H_