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

include/v8.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 5329 matching lines @@
     // CAUTION: The original code below:
     // bool result = ((value + 0x40000000) & 0x80000000) == 0;
     // may lead to incorrect results according to the C language spec, and
     // in fact doesn't work correctly with gcc4.1.1 in some cases: The
     // compiler may produce undefined results in case of signed integer
     // overflow. The computation must be done w/ unsigned ints.
     return static_cast<uintptr_t>(value + 0x40000000U) < 0x80000000U;
   }
 };
 
+#if !V8_USE_31_BITS_SMI_VALUE

[danno, 2013/07/29 13:02:23]

I also see no reason to put the SmiTagging<8> definition in a #ifdef

Also, reverse the sense of the #ifdef


#if V8_USE_31_BIT_SMI_VALUE
typedef SmiTagging<4> PlatformSmiTagging;
#else
typedef SmiTagging<kApiPointerSize> PlatformSmiTagging;
#endif

[haitao.feng, 2013/07/30 08:56:43]

Done.

 // Smi constants for 64-bit systems.
 template <> struct SmiTagging<8> {
   static const int kSmiShiftSize = 31;
   static const int kSmiValueSize = 32;
   V8_INLINE(static int SmiToInt(internal::Object* value)) {
     int shift_bits = kSmiTagSize + kSmiShiftSize;
     // Shift down and throw away top 32 bits.
     return static_cast<int>(reinterpret_cast<intptr_t>(value) >> shift_bits);
   }
   V8_INLINE(static internal::Object* IntToSmi(int value)) {
     return internal::IntToSmi<kSmiShiftSize>(value);
   }
   V8_INLINE(static bool IsValidSmi(intptr_t value)) {
     // To be representable as a long smi, the value must be a 32-bit integer.
     return (value == static_cast<int32_t>(value));
   }
 };
 
 typedef SmiTagging<kApiPointerSize> PlatformSmiTagging;
+#else
+typedef SmiTagging<4> PlatformSmiTagging;
+#endif
+
 const int kSmiShiftSize = PlatformSmiTagging::kSmiShiftSize;
 const int kSmiValueSize = PlatformSmiTagging::kSmiValueSize;
 
 /**
  * This class exports constants and functionality from within v8 that
  * is necessary to implement inline functions in the v8 api.  Don't
  * depend on functions and constants defined here.
  */
 class Internals {
  public:
@@ skipping 1102 matching lines @@
 
 
 }  // namespace v8
 
 
 #undef V8EXPORT
 #undef TYPE_CHECK
 
 
 #endif  // V8_H_