segment .data a: db "This is fun" b: db "This is not" segment .text global main global memcmp memcmp: mov rcx, rdx repe cmpsb cmp rcx, 0 jz equal movzx eax, byte [rdi-1] movzx ecx, byte [rsi-1] sub rax, rcx ret equal: xor eax, eax ret main: push rbp mov rbp, rsp lea rdi, [a] lea rsi, [b] mov edx, 11 call memcmp xor eax, eax leave ret