im in a class learning assembly using mips. I am working on sorting an array of numbers and i think that I have the method working correctly, but just a bit of trouble. I do not know how to check when im sorted fully. Im using a pretty rudimentary method for sorting, but that is all that we have learned thus far. Also, i do not know how to output the numbers to check to see if it is sorted. Im used to Java and such so assembly is kinda throwing me for a spin. Here is my code thus far:
.text
.globl main
main: la $a0, Array # sets the base address of the array to $a0
loop: lw $t0, 0($a0) # sets $t0 to the current element in array
lw $t1, 4($a0) # sets $t1 to the next element in array
blt $t1, $t0, swap # if the following value is greater, swap them
addi $a0, $a0, 4 # advance the array to start at the next location from last time
j loop # jump back to loop so we can compare next two elements
swap: sw $t0, 4($a0) # store the greater numbers contents in the higher position in array (swap)
sw $t1, 0($a0) # store the lesser numbers contents in the lower position in array (swap)
li $a0, 0 # resets the value of $a0 back to zero so we can start from beginning of array
j loop # jump back to the loop so we can go through and find next swap
.data
Array: .word 14, 12, 13, 5, 9, 11, 3, 6, 7, 10, 2, 4, 8, 1
thanks for any help guys!
This link explains how to print to the screen in a MIPS simulator like QTSPIM or MARS.
As for the code, there were a few bugs. The line li $a0, 0 is overwriting the work done by the initial la $a0, Array instruction because the li is setting the base address of your array to 0. Instead, you should move the la instruction into the loop so that $a0 is properly reset to the base address of Array after iterating over the entire array, and remove the li instruction. You also will need to add in a condition for when your program has completed the sort. I would suggest the following revisions (tested with SPIM):
main:
la $t0, Array # Copy the base address of your array into $t1
add $t0, $t0, 40 # 4 bytes per int * 10 ints = 40 bytes
outterLoop: # Used to determine when we are done iterating over the Array
add $t1, $0, $0 # $t1 holds a flag to determine when the list is sorted
la $a0, Array # Set $a0 to the base address of the Array
innerLoop: # The inner loop will iterate over the Array checking if a swap is needed
lw $t2, 0($a0) # sets $t0 to the current element in array
lw $t3, 4($a0) # sets $t1 to the next element in array
slt $t5, $t2, $t3 # $t5 = 1 if $t0 < $t1
beq $t5, $0, continue # if $t5 = 1, then swap them
add $t1, $0, 1 # if we need to swap, we need to check the list again
sw $t2, 4($a0) # store the greater numbers contents in the higher position in array (swap)
sw $t3, 0($a0) # store the lesser numbers contents in the lower position in array (swap)
continue:
addi $a0, $a0, 4 # advance the array to start at the next location from last time
bne $a0, $t0, innerLoop # If $a0 != the end of Array, jump back to innerLoop
bne $t1, $0, outterLoop # $t1 = 1, another pass is needed, jump back to outterLoop
Be sure to check out this link for additional examples and explanations on what each MIPS instruction does.
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