Question

Write an arm assembly program that will multiply two arrays (index by index) and store the result in a third array.

Declare an array:

.data

Arr1: .quad 10    #index 0

            .quad 4      #index 1

         …..

Arr2: .quad 2,5,6….

Arr3: .quad 0,0,0….

To load array pointer address:

     Movq $Arr1, %rdx   #stores address of Arr1 index 0 in rdx

To move to the next index of an array:

    Addq $8,%rdx

To retrieve data:

Movq (%rdx), %rcx         # will have data at address in rdx

We can also use LEA instruction.

Xorq %rbx,%rbx

LEAQ (%rdx, %rbx,8), %<reg>     #address if index 0 in reg

Movq(%<reg>) , %<reg>     #data at index 0

Inc %rbx

To store data:

Movq %<reg>, (%<reg that has address>)

.global main

.text

main:

movq $arr, %rcx            #load address of index 0

movq (%rcx), %rax          #retrieve data at index 0

addq $8, %rcx              #go to next index 8 bytes over

movq (%rcx), %rax          #get data at index 1

#or

xorq %rcx,%rcx

movq $arr, %rbx

leaq (%rbx,%rcx,8), %rax   #ADDRESS OF INDEX 0

movq (%rax),%rax           #content at index 0

incq %rcx

leaq (%rbx,%rcx,8), %rax   #address of index 1

# or

xorq %rcx, %rcx

movq arr(,%rcx,8), %rax    #move content at index 0 to rax

#or

xorq %rcx,%rcx

movq $arr,%rbx

movq (%rbx,%rcx,8), %rdx    #move content at index 0

# exiting

movq $60, %rax # sys_exit syscall number: 60

xorq %Rdi, %Rdi # set exit status to 0

syscall     

.data

arr: .quad 10,11,12

Answer 1

.data
    x: .word 4,5,2
    y: .word 1,8,3  
    z: .space 12
main:
    .text

     la $a0 x #loads contents into $a0
     la $a1 y
     la $a2 z
     jal addArray #function call
     li $v0, 4
     syscall


addArray:
    addi $sp, $sp, -4 # make room for 1 saved register
   [b] sw $s0, 0($sp) # save $s0 onto frame stack[/b]
    add $s0, $zero, $zero # initialize i=0
    add $s1, $zero, 12  #for the loop condition
L1:
    add $t1, $s0, $a0 # compute x[i] as $a0[$s0]
    add $t2, $s0, $a1
    lbu $t3, 0($t1)  # load byte at x[i] (x+i) into $t3
    lbu $t4, 0($t2)   # load byte at y[i] (y+i) into $t3
    add $t5, $t3, $t4 #adding elements x+y and putting it in $t5 
    add $t6, $s0, $a2 
    sb  $t5, 0($t6) #adds to the third array
    beq $s0, $s1, L2 # $s0 >=$s1                 
    addi $s0, $s0, 4 # increment array
    j L1 # jump unconditionally to L1 (beginning of loop)   

L2:
    lw $s0, 0($sp) # restore $sp
    addi $sp, $sp, 1 # pop 1 word off the stack
    jr $ra # return to sender