Question

Assembly Language Programming

1. Construct an assembly language program fragment equivalent to the following C/C++ statement:

if (M <= N + 3 && (C == ‘N’ || C == ‘n’))

C = ‘0’;

else

C = ‘1’;

Assume that M and N are 32-bit signed integer variables, and C is an 8-bit ASCII character variable. All variables are stored in memory, and all general-purpose registers are available for use.

Answer 1

C++ program code

#include <iostream>

using namespace std;

int main()
{
    int M=10,N=20;
    char C[5]={'N','n'};
if (M <= N + 3 && (C == "N" || C == "n"))
{

char C = '0';
cout<<"The value of C is :"<<C;
}

else{

char C = '1';
cout<<"The value of C is :"<<C;
}
    return 0;
}

The Output:

Converted Assembly Language Code:

Please note( x86-64 gcc 10.2 )

.LC0:
        .string "The value of C is :"
main:
        push    rbp
        mov     rbp, rsp
        sub     rsp, 16
        mov     DWORD PTR [rbp-4], 10
        mov     DWORD PTR [rbp-8], 20
        mov     DWORD PTR [rbp-14], 28238
        mov     BYTE PTR [rbp-10], 0
        mov     BYTE PTR [rbp-9], 49
        mov     esi, OFFSET FLAT:.LC0
        mov     edi, OFFSET FLAT:_ZSt4cout
        call    std::basic_ostream<char, std::char_traits<char> >& std::operator<< <std::char_traits<char> >(std::basic_ostream<char, std::char_traits<char> >&, char const*)
        mov     rdx, rax
        movsx   eax, BYTE PTR [rbp-9]
        mov     esi, eax
        mov     rdi, rdx
        call    std::basic_ostream<char, std::char_traits<char> >& std::operator<< <std::char_traits<char> >(std::basic_ostream<char, std::char_traits<char> >&, char)
        mov     eax, 0
        leave
        ret
__static_initialization_and_destruction_0(int, int):
        push    rbp
        mov     rbp, rsp
        sub     rsp, 16
        mov     DWORD PTR [rbp-4], edi
        mov     DWORD PTR [rbp-8], esi
        cmp     DWORD PTR [rbp-4], 1
        jne     .L5
        cmp     DWORD PTR [rbp-8], 65535
        jne     .L5
        mov     edi, OFFSET FLAT:_ZStL8__ioinit
        call    std::ios_base::Init::Init() [complete object constructor]
        mov     edx, OFFSET FLAT:__dso_handle
        mov     esi, OFFSET FLAT:_ZStL8__ioinit
        mov     edi, OFFSET FLAT:_ZNSt8ios_base4InitD1Ev
        call    __cxa_atexit
.L5:
        nop
        leave
        ret
_GLOBAL__sub_I_main:
        push    rbp
        mov     rbp, rsp
        mov     esi, 65535
        mov     edi, 1
        call    __static_initialization_and_destruction_0(int, int)
        pop     rbp
        ret