The textbook's assembly code for problem 3.63 is indirect and potentially confusing.  Below is IA32 assembly code generated for the same C code with a different version of GCC, using two optimization levels.

[ -O1 ]

        movl    8(%ebp), %eax
        leal    (%eax,%eax), %edx
        leal    (%edx,%eax), %ecx
        leal    1(%edx), %eax
        movl    $0, %esi
        testl   %eax, %eax
        jle     L4
        leal    0(,%ecx,4), %ebx
        movl    16(%ebp), %eax
        movl    12(%ebp), %esi
        leal    (%esi,%eax,4), %ecx
        movl    $0, %eax
        movl    $0, %esi
        incl    %edx
L5:
        addl    (%ecx), %esi
        incl    %eax
        addl    %ebx, %ecx
        cmpl    %edx, %eax
        jne     L5
L4:
        movl    %esi, %eax



[ -O2 ]

        movl    8(%ebp), %edx
        leal    (%edx,%edx), %eax
        leal    1(%eax), %esi
        xorl    %ebx, %ebx
        testl   %esi, %esi
        jle     L4
        addl    %edx, %eax
        sall    $2, %eax
        movl    16(%ebp), %ecx
        movl    12(%ebp), %edi
        leal    (%edi,%ecx,4), %edx
        xorl    %ecx, %ecx
L5:
        addl    (%edx), %ebx
        incl    %ecx
        addl    %eax, %edx
        cmpl    %esi, %ecx
        jne     L5
L4:
        movl    %ebx, %eax