Add monomorphic CompareNilICs and Crankshaft support

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 3916 matching lines @@
 
   HValue* left() { return OperandAt(0); }
   HValue* right() { return OperandAt(1); }
 
   virtual void PrintDataTo(StringStream* stream);
 
   virtual Representation RequiredInputRepresentation(int index) {
     return Representation::Tagged();
   }
 
+  virtual Representation observed_input_representation(int index) {
+    return Representation::Tagged();
+  }
+
   DECLARE_CONCRETE_INSTRUCTION(CompareObjectEqAndBranch)
 };
 
 
 class HCompareConstantEqAndBranch: public HUnaryControlInstruction {
  public:
   HCompareConstantEqAndBranch(HValue* left, int right, Token::Value op)
       : HUnaryControlInstruction(left, NULL, NULL), op_(op), right_(right) {
     ASSERT(op == Token::EQ_STRICT);
   }
@@ skipping 2544 matching lines @@
   virtual bool IsDeletable() const { return true; }
 };
 
 
 #undef DECLARE_INSTRUCTION
 #undef DECLARE_CONCRETE_INSTRUCTION
 
 } }  // namespace v8::internal
 
 #endif  // V8_HYDROGEN_INSTRUCTIONS_H_