Writing nop for xchg %ax,%ax loses information. The xchg %ax,%ax is two bytes. If you write "nop", I'd assume that it's the one-byte version. Typically, you us

Writing nop for xchg %ax,%ax loses information. The xchg %ax,%ax is two bytes. If you write "nop", I'd assume that it's the one-byte version. Typically, you use xchg %ax,%ax because you can replace it with a jump if you want.