Page 159 - ARM 64 Bit Assembly Language

Structured programming 145

Listing 5.37 Initializing a structured data type in AArch64 assembly.
1 .data
2 sam: .asciz "Sam"
3 smith: .asciz "Smith"
4 .text
5 .equ s_first_name, 0
6 .equ s_last_name, 30
7 .equ s_class, 60
8 .equ s_grade, 64
9 .equ s_size, 68
10 .equ s_size_aligned, 80
11
12 .type main, %function
13 .global main
14 main:
15 stp x29, x30, [sp, #32]!
16 str x19, [sp, #16] // Callee-saved save
17
18 // struct student newstudent
19 sub sp, sp, #s_size_aligned
20 mov x19, sp // x19=pointer to struct
21 add x0, x19, #s_first_name // offset to first name
22 adr x1, sam // load pointer to "Sam"
23 bl strcpy // copy the string
24 add x0, x19, #s_last_name // offset to last name
25 adr x1, smith // load pointer to "Smith"
26 bl strcpy // copy the string
27 mov w1, #2 // load constant value of 2
28 strb w1, [x19, #s_class] // store with offset
29 mov w1, #88 // load value of 88
30 str w1, [x19, #s_grade] // store with offset
31
32 // use the struct
.
33 . .
34 // delete the struct
35 add sp, sp, #s_size_aligned
36
37 // return 0
38 mov w0, #0
39 ldr x19, [sp, #16] // Callee-saved restore
40 ldp x29, x30, [sp], #32
41 ret
42 .size main,(. - main)