Stores a 64-bit integer value in an 8-byte aligned memory location. To minimize caching, the data is flagged as non-temporal (unlikely to be used again soon).

Intel's documentation

Safety of non-temporal stores

After using this intrinsic, but before any other access to the memory that this intrinsic mutates, a call to _mm_sfence must be performed by the thread that used the intrinsic. In particular, functions that call this intrinsic should generally call _mm_sfence before they return.

See _mm_sfence for details.