MEMBAR for VC

    // Note From MSDN:
    //    In past versions of the Visual C++ compiler, the _ReadWriteBarrier
    //    and _WriteBarrier functions were enforced only locally and did not
    //    affect functions up the call tree. In Visual C++ 2005 and later,
    //    these functions are enforced all the way up the call tree.


// Intel and AMD (x86 and AMD64) enforces strong ordering (program ordering)
// except a store followed by a load (the store becomes visible before
// the load executes) http://en.wikipedia.org/wiki/Memory_ordering
// x86 and x64: Just use compiler fence (no need for hardware fence)
#define MEMBAR                                          \
    #if defined (_M_IX86) || defined (_M_X64)           \
        _ReadWriteBarrier();                            \
    #elif defined (_M_IA64)                             \
        MemoryBarrier();                                \
    #else                                               \
    #error "Need to write code for this architecture"   \
    #endif