Question

I want to convert those codes to assembler code

// Problem 1

// for loop

J=5

for(i=1; i<5; i++) {

        j--

}

// Problem 2

// if - then - else

i=4

if (i < 5) then

        j = 3

else

        j = 2

// Problem 3

//while loop

i = 0

j = 0

while(i==0) {

  j++

  if j = 5 then

        i = j

}

Answer 1

1) Simply we write mov instruction for assigning values to a variable.

Mov instruction : mov destination,source.

Given problem :
//for loop
j=5
for(i=1; i<5; i++) {
        j--
}

Given code can be converted to assembley code as follows :

pushq    %rbp
    movq    %rsp, %rbp
    movl    $5, -8(%rbp) ;j=5
    movl    $1, -4(%rbp) ;i=1
    jmp    .L2
.L3:
    subl    $1, -8(%rbp)
    addl    $1, -4(%rbp)
.L2:
    cmpl    $4, -4(%rbp) ;condition check - i<5
    jle    .L3
    popq    %rbp
    ret

2) Given problem :

i=4
if (i < 5) then
        j = 3
else
        j = 2

This code can be converted to assembley code as follows :

    pushq    %rbp
    movq    %rsp, %rbp
    movl    $4, -8(%rbp) ;assignment instruction which is equivalent to i =4i=4
    cmpl    $4, -8(%rbp) ;comparing whether i < 5 or not
    jg    .L2
    movl    $3, -4(%rbp)
    jmp    .L3
.L2:
    movl    $2, -4(%rbp)
.L3:
    popq    %rbp
    ret

3) Given code :

i = 0
j = 0
while(i==0) {
j++
if j = 5 then
        i = j
}

Above code can be converted to assembley code as follows :

    pushq   %rbp
   movq   %rsp, %rbp
   movl   $0, -8(%rbp)
   movl   $0, -4(%rbp)
   jmp   .L2
.L3:
   addl   $1, -4(%rbp) ;increment of j
   cmpl   $5, -4(%rbp)
   jne   .L2
   movl   -4(%rbp), %eax
   movl   %eax, -8(%rbp)
.L2:
   cmpl   $0, -8(%rbp) ;while condition check
   je   .L3
   popq   %rbp
   ret