arrays - ARM 汇编数组

Question

我试图弄清楚数组在 ARM 汇编中是如何工作的，但我只是不知所措。我想将一个大小为 20 的数组初始化为 0、1、2 等。

A[0] = 0
A[1] = 1

我什至不知道如何打印我必须看到的内容，如果我做得正确的话。这是我到目前为止所拥有的:

.data
.balign 4       @ Memory location divisible by 4
        string: .asciz "a[%d] = %d\n"
        a:      .skip   80      @ allocates 20
.text
.global main
.extern printf

main:
        push    {ip, lr}        @ return address + dummy register
        ldr     r1, =a          @ set r1 to index point of array
        mov     r2, #0          @ index r2 = 0
loop:
        cmp     r2, #20         @ 20 elements?
        beq     end             @ Leave loop if 20 elements
        add     r3, r1, r2, LSL #2      @ r3 = r1 + (r2*4)
        str     r2, [r3]        @ r3 = r2
        add     r2, r2, #1      @ r2 = r2 + 1
        b       loop            @ branch to next loop iteration
print:
        push    {lr}            @ store return address
        ldr     r0, =string     @ format
        bl      printf          @ c printf
        pop     {pc}            @ return address

ARM 让我很困惑，我不知道我做错了什么。如果有人可以帮助我更好地理解它是如何工作的，我将不胜感激。

Answer 1

这可能有助于其他想要了解如何使用 arm 汇编 语言为数组分配内存的人这是一个添加相应数组元素并存储在第三个数组中的简单示例。

.global  _start

_start:
      MOV R0, #5              
      LDR R1,=first_array     @ loading the address of first_array[0]
      LDR R2,=second_array    @ loading the address of second_array[0]
      LDR R7,=final_array     @ loading the address of final_array[0]
      MOV R3,#5               @ len of array
      MOV R4,#0               @ to store sum
check: 
      cmp R3,#1               @ like condition in for loop for i>1
      BNE loop                @ if R3 is not equal to 1 jump to the loop label
      B _exit                 @ else exit
loop:
      LDR R5,[R1],#4          @ loading the values and storing in registers and base register gets updated automatically R1 = R1 + 4 
      LDR R6,[R2],#4          @ similarly
      add R4,R5,R6         
      STR R4,[R7],#4          @ storing the values back to the final array 
      SUB R3,R3,#1            @ decrment value just like i-- in for loop
      B check
_exit:
      LDR R7,=final_array     @ before exiting checking the values stored 
      LDR R1, [R7]            @ R1 = 60 
      LDR R2, [R7,#4]         @ R2 = 80
      LDR R3, [R7,#8]         @ R3 = 100
      LDR R4, [R7,#12]        @ R4 = 120
      MOV R7, #1              @ terminate syscall, 1
      SWI 0                   @ execute syscall

.data
first_array:  .word 10,20,30,40  
second_array: .word 50,60,70,80 
final_array:  .word 0,0,0,0,0