main:
        pushq   %rbp
        movq    %rsp, %rbp
        subq    $16, %rsp
        movq    $1000, -8(%rbp)
        movq    -8(%rbp), %rax
        movq    %rax, %rdi          ; <---
        call    pass(unsigned long) ; <---
        movl    $0, %eax
        leave
        ret