Optionally use 31-bits SMI value for 64-bit system

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 3324 matching lines @@
 
   bool IsCell() const {
     return is_cell_;
   }
 
   virtual Representation RequiredInputRepresentation(int index) {
     return Representation::None();
   }
 
   virtual Representation KnownOptimalRepresentation() {
-    if (HasSmiValue() && kSmiValueSize == 31) return Representation::Smi();
+    if (HasSmiValue() && SmiValuesAre31Bits()) return Representation::Smi();
     if (HasInteger32Value()) return Representation::Integer32();
     if (HasNumberValue()) return Representation::Double();
     if (HasExternalReferenceValue()) return Representation::External();
     return Representation::Tagged();
   }
 
   virtual bool EmitAtUses();
   virtual void PrintDataTo(StringStream* stream);
   bool IsInteger() { return handle()->IsSmi(); }
   HConstant* CopyToRepresentation(Representation r, Zone* zone) const;
@@ skipping 3498 matching lines @@
   virtual bool IsDeletable() const { return true; }
 };
 
 
 #undef DECLARE_INSTRUCTION
 #undef DECLARE_CONCRETE_INSTRUCTION
 
 } }  // namespace v8::internal
 
 #endif  // V8_HYDROGEN_INSTRUCTIONS_H_