bswap

Swaps bytes in a 4 byte uint end-to-end, i.e. byte 0 becomes byte 3, byte 1 becomes byte 2, byte 2 becomes byte 1, byte 3 becomes byte 0.

Swaps bytes in an 8 byte ulong end-to-end, i.e. byte 0 becomes byte 7, byte 1 becomes byte 6, etc. This is meant to be recognized by the compiler as an intrinsic.