循环遍历阵列 MIPS 程序集 [英] Loop through an array MIPS Assembly

问题描述

我正在编写一个程序，它循环遍历 10 个数字的数组.前 9 个元素的值大于 0，第 10 个元素的值为 0.当遇到 0 时，循环应该中断.

I'm working on a program which loops through an array of 10 numbers. The first 9 elements have values higher than 0, the 10th has a value of 0. The loop should break when the 0 is encountered.

i=0;
while(A[i]!=0)
{
    A[i]=A[i]+1;
    i++;
}

我知道如果寄存器的值等于 0，我可以使用 'beq' 来中断循环.但是我对操作内存中的值知之甚少.

I know I can use 'beq' to break the loop if the value of the register is equal to 0. However I don't know enough about manipulating values in the memory.

这是我第一次使用 MIPS，你会发现它很混乱.如果你不能为我修复它，你能给我一些指点吗?

It's my first time using MIPS and you'll see it's a mess. If you can't fix it for me, can you give me some pointers?

.data  #by default, the "data segment" starts at address 0x10010000
.word 1
.word 2
.word 3
.word 4
.word 5
.word 6
.word 7
.word 8
.word 9
.word 0

.text #instructions start below

# MIPS assembly code

lui  $a0, 0x1001           # $a0 = 0x10010000
addi $a1, $zero, 0         # i = 0
jal increment              # call the procedure

这是我最迷失的地方:

increment:
lui $a0, 0x1001           # $a0 = 0x10010000
beq $a0, $zero, else      # if $a0 holds 0 goto 'else'
addi $a0, $a0, 2          # +2
addi $a1, $zero, 1        # i = i + 1

jr $ra                   #jump to caller

$v0 应该保存所有递增值的总和.

$v0 should hold the sum of all the incremented values.

else: 
add $a0, $v0, $zero #copy result as input to syscall
addi $v0,$zero,1 #service 1 for syscall is print integer
syscall

以无限循环结束.

infinite: j infinite

推荐答案

要从内存中加载一个值，需要调用加载指令之一，(lw, lh 或 lb 用于字、半字和字节).例如:

To load a value from a memory, you need to call one of the load instructions, (lw, lh or lb for word, half-word and byte). for example:

lw $a1, 0($a2) # load a word from the address in $a2 + offset 0 to $a1

要在内存中写入一个值，您可以使用 store 命令之一，例如:

to write a value in memory, you use one of the store commands, for example:

sw $a1, 0($a2) # store the word in $a1 into the address in $a2 + offset

例如使用 la 将地址加载到寄存器中

loading an address into a register is done using la, for example

la $a2, label_of_array # load the address of the label 'label_of_array' into $a2

现在，要操作数组中的值，您需要结合上面的三个指令:

Now, to manipulate the value in the array, you need to combine the three instructions from above:

la $a1, label_of_array   # load the address of the array into $a1
lb $a2, 0($a1)           # load a byte from the array into $a2
addi $a2, $a2, 1         # increment $a2 by 1
sb $a2, 0($a1)           # store the new value into memory
addi $a1, $a1, 1         # increment $a1 by one, to point to the next element in the array

还有一点:

你写了 addi $a1, $zero, 1 # i = i + 1 但这是错误的.您所做的是将 $zero + 1 的结果存储到 $a1 中，即 1.为了增加$a1，你需要写addi $a1, $a1, 1 即存储$a1 + 1 进入$a1.

You wrote addi $a1, $zero, 1 # i = i + 1 but this is wrong. What you did is to store the result of $zero + 1 which is 1 into $a1. In order to increment $a1, you need to write addi $a1, $a1, 1 which is "store the result of $a1 + 1 into $a1.

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