Write the following subroutine in x86 assembly: int f(int v1, int v2, int v3) {i

Question

Write the following subroutine in x86 assembly: int f(int v1, int v2, int v3) {int x = v1 + v2; return (x + v3) * (x - v3);} Recall that: Subroutine arguments are passed on the stack, and can be accessed within the body of the subroutine starting at address EBP+8. At the start of each subroutine: i. Save EBP on the stack ii. Copy the current value of the stack pointer (ESP) to EBP iii. Create space within the stack for each local variable by subtracting the appropriate value from ESP. For example, if your function uses four integer local variables, each of which contains four bytes, subtract 16 from ESP. Local variables can then be accessed starting at the address EBP-4. iv. Save any registers the function uses other than EAX, ECX, and EDX. A subroutine's return value is typically stored in EAX.

Explanation / Answer

Full program for given subroutine---->

#include <iostream>
using namespace std;
int f(int num1, int num2, int num3);
int main () {
    int a,b,c;
    a=100;b=200;c=300;
   int ret;
   ret = f(a, b, c);
   cout << "Return value is : " << ret << endl;
   return 0;
}
int f(int v1, int v2, int v3)
{
    int x=v1+v2;
    return (x+v3)*(x-v3);
}

x86 assembly language code for above given program --------->

.LC0:
        .string "Return value is : "
main:
        push    rbp
        mov     rbp, rsp
        sub     rsp, 16
        mov     DWORD PTR [rbp-4], 100
        mov     DWORD PTR [rbp-8], 200
        mov     DWORD PTR [rbp-12], 300
        mov     edx, DWORD PTR [rbp-12]
        mov     ecx, DWORD PTR [rbp-8]
        mov     eax, DWORD PTR [rbp-4]
        mov     esi, ecx
        mov     edi, eax
        call    f(int, int, int)
        mov     DWORD PTR [rbp-16], eax
        mov     esi, OFFSET FLAT:.LC0
        mov     edi, OFFSET FLAT:std::cout
        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
        mov     eax, DWORD PTR [rbp-16]
        mov     esi, eax
        mov     rdi, rdx
        call    std::basic_ostream<char, std::char_traits<char> >::operator<<(int)
        mov     esi, OFFSET FLAT:std::basic_ostream<char, std::char_traits<char> >& std::endl<char, std::char_traits<char> >(std::basic_ostream<char, std::char_traits<char> >&)
        mov     rdi, rax
        call    std::basic_ostream<char, std::char_traits<char> >::operator<<(std::basic_ostream<char, std::char_traits<char> >& (*)(std::basic_ostream<char, std::char_traits<char> >&))
        mov     eax, 0
        leave
        ret
f(int, int, int):
        push    rbp
        mov     rbp, rsp
        mov     DWORD PTR [rbp-20], edi
        mov     DWORD PTR [rbp-24], esi
        mov     DWORD PTR [rbp-28], edx
        mov     edx, DWORD PTR [rbp-20]
        mov     eax, DWORD PTR [rbp-24]
        add     eax, edx
        mov     DWORD PTR [rbp-4], eax
        mov     edx, DWORD PTR [rbp-4]
        mov     eax, DWORD PTR [rbp-28]
        add     edx, eax
        mov     eax, DWORD PTR [rbp-4]
        sub     eax, DWORD PTR [rbp-28]
        imul    eax, edx
        pop     rbp
        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     .L7
        cmp     DWORD PTR [rbp-8], 65535
        jne     .L7
        mov     edi, OFFSET FLAT:std::__ioinit
        call    std::ios_base::Init::Init()
        mov     edx, OFFSET FLAT:__dso_handle
        mov     esi, OFFSET FLAT:std::__ioinit
        mov     edi, OFFSET FLAT:std::ios_base::Init::~Init()
        call    __cxa_atexit
.L7:
        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

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