This is my quick sort MIPS assembly code that runs in eclipse. However, when I r

ID: 3758416 • Letter: T

Question

This is my quick sort MIPS assembly code that runs in eclipse.
However, when I run this I get this error message

00000000: Failed to execute MI command:
-data-disassemble -s 0 -e 32 -- 3
Error message from debugger back end:
Cannot access memory at address 0x0

Would you tell me what's wrong here and whether there are any other erros?

.globl my_qsort
my_qsort:
# $a0=given array v, $a1=leftmost index, $a2= rightmost index
# $s3 = index 'last' $s4 = variabl 'i' for iteration

addi $sp, $sp, -24   # make room on stack for 6 registers
sw $ra, 20($sp)       # save $ra on stack
sw $s4, 16($sp)       # save $s4 on stack
sw $s3, 12($sp)       # save $s3 on stack
sw $s2, 8($sp)       # save $s2 on stack
sw $s1, 4($sp)       # save $s1 on stack
sw $s0, 0($sp)       # save $s0 on stack

move $s0, $a0       # copy parameter $a0 into $s0
move $s1, $a1       # copy parameter $a1 into $s1
move $s2, $a2       # copy parameter $a2 into $s2

                   # #if (left >= right) return
slt $t0, $s1, $s2   # set $t0 = 0 if $s1 >= $s2
beq $t0, $zero, exit1   # go to exit1 if $s1 >= $s2

add $t0, $s1, $s2 # $t0 is temporary value temp = left+right
srl $t0, $t0, 2 # $t0 = (left+right)/2

move $a2, $t0 # 3rd parameter of swap is (left+right)/2
jal swap # swap(v, left, (left+right)/2)

move $s3, $a1       # copy parameter $a1 into $s3, last = left
move $s4, $zero       # i = 0
addi $s4, $s1, 1   # i = left+1

loop:
slt $t0, $s2, $s4   # set $t0 = 1 if $s2 < $s4 that is (right < i)
bne $t0, $zero, L1     # if (right<i) return to L1
sll $t1, $s4, 2       # $t1 = i*4
add $t2, $s0, $t1   # $t2 = v+(i*4) = v[i]
sll $t1, $s1, 2       # $t1 = left*4
add $t3, $s0, $t1   # $t3 = v+(left*4) = v[left]

addi $s3, $s3, 1   # last= last+1
move $a1, $s3       # 2nd parameter of swap is last
move $a2, $s4       # 3rd parameter of swap is i

slt $t0, $t2, $t3   # set $t0 = 1 if v[i]<v[left]
bne $t0, $zero, swap   # if v[i]<v[left] go to swap
addi $s4, $s4, 1   # i = i+1
j loop

L1:
move $a1, $s1 # 2nd parameter of swap is left
move $a2, $s3 # 3rd parameter of swap is last
jal swap

addi $t0, $s3, -1 # $t0 = last-1
move $a2, $t0 # 3rd parameter of qsort is last-1
jal qsort

addi $t0, $s3, 1   # $t0 = last+1
move $a1, $t0       # 2nd parameter of qsort is last+1
move $a2, $s2       # 3rd parameter of qsort is right
jal qsort

j exit1 # jump to exit1

exit1: #return value and restore stacks, return to caller
lw $s0, 0($sp)       # restore $s0 from stack
lw $s1, 4($sp)       # restore $s1 from stack
lw $s2, 8($sp)       # restore $s2 from stack
lw $s3, 12($sp)       # restore $s3 from stack
lw $s4, 16($sp)       # restore $s4 from stack
lw $ra, 20($sp)       # restore $ra from stack
addi $sp, $sp, 24   # restore stack pointer
jr $ra           # return to calling routine

swap:
# $a0=v, $t1=index1, $t2=index2, $t0=temp
sll $t1, $a1, 2    # reg $t1 = index1*4
add $t1, $a0, $t1    # reg $t1 = v+(index1*4) = v[index1]
sll $t2, $a2, 2       # reg $t2 = k*4
add $t2, $a0, $t2    # reg $t2 = v+(index2*4) = v[index2]
lw $t0, 0($t1)       # temp = v[index1]
sw $t2, 0($t1)       # v[index1] = v[index2]
sw $t0, 0($t2)       # v[index2] = temp
jr $ra           # return to caller

Explanation / Answer

Code

# $a0=given array v, $a1=leftmost index, $a2= rightmost index
# $s3 = index 'last' $s4 = variabl 'i' for iteration