foo(something *rdi) {
       int? rax = -1;
here:
       something tmp = (memory[1 + rdi + rax] != 0);
       rax = rax + 1;
       if (tmp) goto here;
       return rax;
}

strlen(char *rdi) {
       long rax = -1;
       do {
              char tmp = (memory[1 + rdi + rax] != 0);
              rax = rax + 1;
       } while (tmp);
       return rax;
}

foo("\0") -> 0
foo("") -> ??? 1 or 0 or crash or infinite loop
foo("h") -> 1
foo("hello") -> 5

"hi" -> {'h', 'i', '\0'}
movq    $-1, %rax
       %rax is a "register"
       rax = -1

here:
cmpb    $0, 1(%rdi,%rax)
       is 0 < memory[1 + rdi + rax]
       because rdi is new, it's probably a parameter of function
       rdi is probably a pointer

leaq    1(%rax), %rax
       rax = 1 + rax

jne     0x7 <foo+0x7>
       if last comparison was not ==, go to "here"

retq (rax)