Recognize special comparisons via pattern matching on the hydrogen graph, 2nd attempt.

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 2269 matching lines @@
 
   virtual bool IsConvertibleToInteger() const {
     if (handle_->IsSmi()) return true;
     if (handle_->IsHeapNumber() &&
         (HeapNumber::cast(*handle_)->value() ==
          static_cast<double>(NumberToInt32(*handle_)))) return true;
     return false;
   }
 
   virtual bool EmitAtUses() { return !representation().IsDouble(); }
+  virtual HValue* Canonicalize();
   virtual void PrintDataTo(StringStream* stream);
   virtual HType CalculateInferredType();
   bool IsInteger() const { return handle_->IsSmi(); }
   HConstant* CopyToRepresentation(Representation r) const;
   HConstant* CopyToTruncatedInt32() const;
   bool HasInteger32Value() const { return has_int32_value_; }
   int32_t Integer32Value() const {
     ASSERT(HasInteger32Value());
     return int32_value_;
   }
@@ skipping 1852 matching lines @@
  public:
   explicit HTypeof(HValue* context, HValue* value) {
     SetOperandAt(0, context);
     SetOperandAt(1, value);
     set_representation(Representation::Tagged());
   }
 
   HValue* context() { return OperandAt(0); }
   HValue* value() { return OperandAt(1); }
 
+  virtual HValue* Canonicalize();
   virtual void PrintDataTo(StringStream* stream);
 
   virtual Representation RequiredInputRepresentation(int index) {
     return Representation::Tagged();
   }
 
   DECLARE_CONCRETE_INSTRUCTION(Typeof)
 };
 
 
@@ skipping 76 matching lines @@
 
   DECLARE_CONCRETE_INSTRUCTION(In)
 };
 
 #undef DECLARE_INSTRUCTION
 #undef DECLARE_CONCRETE_INSTRUCTION
 
 } }  // namespace v8::internal
 
 #endif  // V8_HYDROGEN_INSTRUCTIONS_H_