Page 161 - ARM 64 Bit Assembly Language

Structured programming 147

Listing 5.39 Initializing an array of structured data in assembly.

1 .equ i_red, 0
2 .equ i_green, 1
3 .equ i_blue, 2
4 .equ i_size, 3
5 .equ width, 100
6 .equ height, 100
7
8 .text
9 .type main, %function
10 .global main
11 main: stp x29, x30, [sp, #-16]!
12 // Call malloc to allocate the array of pixels
13 mov x0, #(100*100*3) // precompute w*h*size
14 bl malloc // allocate storage.
15 cmp x0, xzr // if (image != NULL)
16 bne endif // goto endif
17 mov w0, #1 // else return 1
18 b return
19 endif: mov w3, #100 // w3 = width
20 mov w4, #100 // w4 = height
21 mov w5, #0 // w5 = 0
22 mov w1, #0 // intj=0
23 loop1: mov w2, #0 // inti=0
24 loop2: madd x9, x1, x3, x2 // x9 = j * width + i
25 add x9, x9, x0 // x9 += image address
26 strb w5, [x9, #i_red] // image[j*w+i].red = 0
27 strb w5, [x9, #i_green] // image[j*w+i].green = 0
28 strb w5, [x9, #i_blue] // image[j*w+i].blue = 0
29 add w2, w2, #1 // i++
30 cmp w2, w3 // if (i < width) goto loop2
31 ble loop2 // end of loop2
32
33 add w1, w1, #1 // j++
34 cmp w1, w4 //if (j < height) goto loop1
35 ble loop1 // end of loop1
36
37 bl free // free(image)
38 mov w0, #0 // return 0
39 return: ldp x29, x30, [sp], #16
40 ret
41 .size main,(. - main)