1 or 2 uops, 1 or 2 cycles (depending on data size). So quite fast. There's also the newish MOVBE (load/store big endian), which currently performs fairly simil

1 or 2 uops, 1 or 2 cycles (depending on data size). So quite fast. There's also the newish MOVBE (load/store big endian), which currently performs fairly similarly to MOV + BSWAP per Agner, but could be made into a single uop in the future.