What does xchg eax, eax do? Is it a NOP?

Question

What is the effect of:

xchgl %eax, %eax

xchg is for swapping data, but if src and dst are the same, then it has basically no effect?

Answer 1

xchg eax, eax, or in binary the one-byte instruction 0x90, is also known as nop. It does nothing.