1 ; ifint_64.asm code ifint_64.c for nasm
2 ; /* ifint_64.c an 'if' statement that will be coded for nasm */
3 ; #include <stdio.h>
4 ; int main()
5 ; {
6 ; long int a=1;
7 ; long int b=2;
8 ; long int c=3;
9 ; if(a<b)
10 ; printf("true a < b \n");
11 ; else
12 ; printf("wrong on a < b \n");
13 ; if(b>c)
14 ; printf("wrong on b > c \n");
15 ; else
16 ; printf("false b > c \n");
17 ; return 0;
18 ;}
19 ; result of executing both "C" and assembly is:
20 ; true a < b
21 ; false b > c
22
23 global main ; define for linker
24 extern printf ; tell linker we need this C function
25 section .data ; Data section, initialized variables
26 00000000 0100000000000000 a: dq 1
27 00000008 0200000000000000 b: dq 2
28 00000010 0300000000000000 c: dq 3
29 00000018 747275652061203C20- fmt1: db "true a < b ",10,0
30 00000021 62200A00
31 00000025 77726F6E67206F6E20- fmt2: db "wrong on a < b ",10,0
32 0000002E 61203C2062200A00
33 00000036 77726F6E67206F6E20- fmt3: db "wrong on b > c ",10,0
34 0000003F 62203E2063200A00
35 00000047 66616C73652062203E- fmt4: db "false b > c ",10,0
36 00000050 2063200A00
37
38 section .text
39 00000000 55 main: push rbp ; set up stack
40 00000001 488B0425[00000000] mov rax,[a] ; a
41 00000009 483B0425[08000000] cmp rax,[b] ; compare a to b
42 00000011 7D11 jge false1 ; choose jump to false part
43 ; a < b sign is set
44 00000013 48BF- mov rdi, fmt1 ; printf("true a < b \n");
45 00000015 [1800000000000000]
46 0000001D E8(00000000) call printf
47 00000022 EB0F jmp exit1 ; jump over false part
48 false1: ; a < b is false
49 00000024 48BF- mov rdi, fmt2 ; printf("wrong on a < b \n");
50 00000026 [2500000000000000]
51 0000002E E8(00000000) call printf
52 exit1: ; finished 'if' statement
53
54 00000033 488B0425[08000000] mov rax,[b] ; b
55 0000003B 483B0425[10000000] cmp rax,[c] ; compare b to c
56 00000043 7E11 jle false2 ; choose jump to false part
57 ; b > c sign is not set
58 00000045 48BF- mov rdi, fmt3 ; printf("wrong on b > c \n");
59 00000047 [3600000000000000]
60 0000004F E8(00000000) call printf
61 00000054 EB0F jmp exit2 ; jump over false part
62 false2: ; a < b is false
63 00000056 48BF- mov rdi, fmt4 ; printf("false b > c \n");
64 00000058 [4700000000000000]
65 00000060 E8(00000000) call printf
66 exit2: ; finished 'if' statement
67
68 00000065 5D pop rbp ; restore stack
69 00000066 B800000000 mov rax,0 ; normal, no error, return value
70 0000006B C3 ret ; return 0;