Copy array elements to another array in MIPS assembly - arrays

Question

i have to make a program that fills an array with 30 integers entered from keyboard.Then the user type 'c' to copy the array to an other array.i've done with the first step but i cant manage to copy the array to another.
Here is my code
.data
msg1: .asciiz "> "
msg2: .asciiz "type 'c' to copy \n>"
.align 2
array: .space 400
.text
main:
la $t3 array
loop:
la $a0, msg1 #output message 1
li $v0, 4
syscall
li $v0, 5 #read integer input
syscall
move $t0, $v0
beq $t0, -99, endloop #loop until user types -99
beq $t1,30,endloop #get user input up to 30 times
addi $t1, $t1, 1 #counter
sw $t0,($t3)
addi $t3,$t3,4
b loop #loop until it reaches 30
endloop:
la $a0, msg2 #output message 2
li $v0, 4
syscall
li $v0, 12 #read character input
syscall
beq $v0, 'c', COPY
j NEXT
COPY:
NEXT:

Answer 1

The most primitive way to do it is to
la $t1, dst_array
la $t3, src_array
addu $t0, $t3, 30*4 # setup a 'ceiling'
copy_loop:
lw $at, 0($t3)
sw $at, 0($t1)
addu $t1, $t1, 4
addu $t3, $t3, 4
blt $t1, $t0, copy_loop # if load pointer < src_array + 30*4
However, some implementations of MIPS don't use forwarding, and therefore you have to wait until $at is written back. For that purpose, there may be either a stall (which you could get rid off)
subu $t1, $t1, 4
copy_loop:
lw $at, 0($t3)
addu $t1, $t1, 4
addu $t3, $t3, 4
sw $at, 0($t1)
or a load delay slot, which usually takes 1 cycle, making it
copy_loop:
lw $at, 0($t3)
addu $t1, $t1, 4
sw $at, 0($t1)
addu $t3, $t3, 4
Generally speaking, it depends :)