I have made the inner loop which is doing comparison and swapping but i am having a difficulty in implementing outer loop which will run according to the number of elements.
.data
Arr: .word 5, 4, 3, 2, 1
.text
.globl main
main:
la $a0, Arr # Pass the base address of the array Arr to input argument register $a0
addi $a1, $zero, 5 # initialze the value of sorting loop ($al=5)
li $t1, 0 # initialize the value of outer loop (t1=0)
sort:
lw $s1, 0($a0) # Load first element in s1
lw $s2, 4($a0) # Load second element in s2
bgt $s1, $s2, swap # if (s1 > s2) go to swap
sorting_loop:
addiu $a0, $a0, 4 # move pointer to next element
subiu $a1, $a1, 1 # decrement the value of inner loop ($a1)
bgtz $a1, sort # loop till value of inner loop is not equal to zero
j end
swap:
sw $s1, 4($a0) # put value of [i+1] in s1
sw $s2, 0($a0) # put value of [i] in s2
j sorting_loop
end: # End the program
li $v0, 10
syscall
Your inner pass looked pretty good, but [I think] it was going one past the end with the 4($a0) (e.g. for an array of 5, the loop count must be 4). I've fixed that.
I've added the outer loop. Please excuse the gratuitous style cleanup, but it's how I could understand your logic before adding to it. I renamed some of your labels so they would make more sense to me.
When I added the outer loop, I converted your inner one into a function called by the outer loop [seemed cleaner that way].
I added two optimizations: decrementing the pass count and the "early escape" flag [if a given pass makes no swaps].
I've also added a number of annotations. The code may not be perfect, but I think it will help get you closer.
# bubble sort
.data
Arr: .word 5,4,3,2,1
.text
.globl main
main:
li $t1,5 # get total number of array elements
# main_loop -- do multiple passes through array
main_loop:
subi $a1,$t1,1 # get count for this pass (must be one less)
blez $a1,main_done # are we done? if yes, fly
la $a0,Arr # get address of array
li $t2,0 # clear the "did swap" flag
jal pass_loop # do a single sort pass
# NOTES:
# (1) if we make no swaps on a given pass, everything is in sort and we
# can stop
# (2) after a pass the last element is now highest, so there is no need
# to compare it again
# (3) a standard optimization is that each subsequent pass shortens the
# pass count by 1
# (4) by bumping down the outer loop count here, this serves both _us_ and
# the single pass routine [with a single register]
beqz $t2,main_done # if no swaps on current pass, we are done
subi $t1,$t1,1 # bump down number of remaining passes
b main_loop
# everything is sorted
# do whatever with the sorted data ...
main_done:
j end # terminate program
# pass_loop -- do single pass through array
# a0 -- address of array
# a1 -- number of loops to perform (must be one less than array size because
# of the 4($a0) below)
pass_loop:
lw $s1,0($a0) # Load first element in s1
lw $s2,4($a0) # Load second element in s2
bgt $s1,$s2,pass_swap # if (s1 > s2) swap elements
pass_next:
addiu $a0,$a0,4 # move pointer to next element
subiu $a1,$a1,1 # decrement number of loops remaining
bgtz $a1,pass_loop # swap pass done? if no, loop
jr $ra # yes, return
pass_swap:
sw $s1,4($a0) # put value of [i+1] in s1
sw $s2,0($a0) # put value of [i] in s2
li $t2,1 # tell main loop that we did a swap
j pass_next
# End the program
end:
li $v0,10
syscall