Question

Convert the following C code to assembler:

a) unsigned char A, B, C;

if (A > B) C = A;

elseif (A == B) C = 0;

else C = B;

b) unsigned char A, B;

A = 228;

B = A/4;

c) unsigned char A, B;

A = 228;

B = A/5;

Answer 1

Below is he solution:

A)

main:
push rbp
mov rbp, rsp
movzx eax, BYTE PTR [rbp-1]
cmp al, BYTE PTR [rbp-2]
jbe .L2
movzx eax, BYTE PTR [rbp-1]
mov BYTE PTR [rbp-3], al
jmp .L3
.L2:
movzx eax, BYTE PTR [rbp-1]
cmp al, BYTE PTR [rbp-2]
jne .L4
movzx eax, BYTE PTR [rbp-1]
mov BYTE PTR [rbp-3,0
jmp .L3
.L4:
movzx eax, BYTE PTR [rbp-1]
mov BYTE PTR [rbp-3], al
.L3:
mov eax,0
pop rbp
ret

B)

main:
push rbp
mov rbp, rsp
mov BYTE PTR [rbp-1], -28
movzx eax, BYTE PTR [rbp-1]
shr al,2
mov BYTE PTR [rbp-2],al
mov eax,0
pop rbp
ret

C)