C语言 MIPS 程序集 - 数组？
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MIPS Assembly - Arrays?
提问by Shannon
I am absolutely brand new to assembly programming and am trying to implement the following function (in C) in MIPS:
我对汇编编程完全陌生，并且正在尝试在 MIPS 中实现以下函数（用 C 语言）：
int main()
{
int A[5]; // Empty memory region for 5 elements
int B[5] = {1,2,4,8,16};
int i;
for(i=0; i<5; i++) {
A[i] = B[i] - 1;
}
i--;
while(i >= 0) {
A[i]=(A[i]+B[i]) * 2;
i--;
}
}
So far what I have is this:
到目前为止，我所拥有的是：
main:
#Register Map
#i --> $s0
#A[0] --> $s1 address of start of A
#B[0] --> $s2 address of start of B
#A[i] --> $t0
#B[i] --> $t1
#(A[i] + B[i]) --> $t2
#((A[i] + B[i]) * 2) --> $t3
li $s0, 0 #Load immediate value 0 into i
#Begin for loop:
#for(i=0; i<5; i++){ A[i] = B[i] - 1; }
FOR_LOOP:
beq $s1, $t0, END_FOR #Branch if i == 5, go to END_FOR
addi $s0, $s0, 1 #Add immediate value 1 to i (i++)
j FOR_LOOP #Jump back to the top to loop again
END_FOR: #End for loop
addi $s0, $s0, -1 #Add immediate value -1 to i (i--)
#Begin while loop:
#while(i >= 0) { A[i] = (A[i] + B[i]) * 2; i--; }
WHILE_LOOP:
blt $s1, 0, END_WHILE #Branch END_WHILE when !(i > 0)
addi $s0, $s0, -1 #Add immediate value -1 to i (i--)
j WHILE_LOOP #Branch back to the while loop
END_WHILE:
sw $s0, i #Copy value in register to memory i
li $v0, 10 #Read integer from user, returned in $v0 (10=exit)
syscall #End program
#Store A, B in memory
.data
A: .word 0:5 #Allocate 20 consecutive bytes for 5-element integer word array A
B: .word 1, 2, 4, 8, 16 #Integer words stored in 5-element array B
i: .word 1 #Initial Value 1
My main questions are:
我的主要问题是：
How would I access the elements of the array, or where do I begin with
la?Did I declare the arrays correctly?
Does my register map make sense for what is trying to be accomplished?
我将如何访问数组的元素，或者从哪里开始
la？我是否正确声明了数组？
我的注册地图对要完成的工作有意义吗？
Thank you for any and all help.
感谢您的任何帮助。
回答by SkyMaster
.text
main:
#Register Map
#i --> $s0
#A[0] --> $s1 address of start of A
#B[0] --> $s2 address of start of B
#A[i] --> $t0
#B[i] --> $t1
#(A[i] + B[i]) --> $t3
#((A[i] + B[i]) * 2) --> $t3
li $s0, 0 #Load immediate value 0 into i
li $t4,5 #upper limit
la $s1,A #address of start of A
la $s2,B #address of start of B
#Begin for loop:
#for(i=0; i<5; i++){ A[i] = B[i] - 1; }
FOR_LOOP:
bge $s0, $t4, END_FOR #Branch if i >= 5, go to END_FOR
lw $t1,($s2) #$t1=B[i]
addi $t1, $t1, -1 #$t1=B[i]-1
sw $t1,($s1) #A[i]=B[i]-1
addi $s1, $s1,4 #next element A[i+1]
addi $s2, $s2,4 #next element B[i+1]
addi $s0, $s0, 1 #Add immediate value 1 to i (i++)
j FOR_LOOP #Jump back to the top to loop again
END_FOR: #End for loop
addi $s0, $s0, -1 #Add immediate value -1 to i (i--)
addi $s1, $s1,-4 #previous element A[i-1]
addi $s2, $s2,-4 #previous element B[i-1]
#Begin while loop:
#while(i >= 0) { A[i] = (A[i] + B[i]) * 2; i--; }
WHILE_LOOP:
blt $s0, 0, END_WHILE #Branch END_WHILE when (i < 0)
lw $t0,($s1) #$t0=A[i]
lw $t1,($s2) #$t1=B[i]
add $t3, $t0,$t1 #$t3=A[i] + B[i]
mul $t3, $t3, 2 #$t3=(A[i] + B[i]) * 2
sw $t3,($s1) #A[i] = (A[i] + B[i]) * 2
addi $s1, $s1,-4 #previous element A[i-1]
addi $s2, $s2,-4 #previous element B[i-1]
addi $s0, $s0, -1 #Add immediate value -1 to i (i--)
j WHILE_LOOP #Branch back to the while loop
END_WHILE:
PRINT: #print array A[i]
li $s0, 0 #i=0
la $s1, A #$s1=A[0]
LOOP:
bge $s0, $t4, END # if i >=5 goto END
lw $a0, ($s1) # $a0 = A[i]
li $v0, 1 #function print integers
syscall
la $a0, space #print separator (1 space)
li $v0, 4 #function print strings
syscall
addi $s1, $s1, 4 #next element A[i+1]
addi $s0, $s0, 1 #i++
b LOOP
END:
li $v0, 10 # $v0 (10=exit)
syscall #End program
#Store A, B in memory
.data
A: .word 0:5 #Allocate 20 consecutive bytes for 5-element integer word array A
B: .word 1, 2, 4, 8, 16 #Integer words stored in 5-element array B
space: .asciiz " " #space as separator
