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BSWAP

Reverses the byte order of a dword or qword.

The table after the description covers what the source and destinations can be.

DO NOT support LOCK

This instruction is available in 32-bit and 64-bit modes. In 64-bit mode, the instruction can operate on either a dword or a qword. In compatibility mode, the behavior is consistent with the 32-bit operation for dword operands.

When utilizing BSWAP on a memory operand, the result is loaded into a register; it cannot store the result directly back to memory. To swap bytes in memory, the value MUST be loaded into a register, processed with BSWAP, and then stored back to the memory location.