visual 2013下的原子商店运营实施

Question

var_.store(value, std::memory_order_relaxed);

inline void _Store_relaxed_4(volatile _Uint4_t *_Tgt, _Uint4_t _Value)
    {   /* store _Value atomically with relaxed memory order */
 #if defined(_M_ARM)
    __iso_volatile_store32((volatile int *)_Tgt, _Value);

 #else
    *_Tgt = _Value;
 #endif
    }

* _ Tgt = _Value; 如何可以是原子的？