mergesort recursion in mips - mips

Question

I am working with mergesort mips operating on Mars
i run it, the array is arranged but it has some troubles and it announces that error in : invalid program counter value: 0x00000000
Go: execution terminated with errors
please help me
thank you very much
.data # Data declaration section
text1: .asciiz "My array"
text2: .asciiz "Sorted Array"
newline: .asciiz "\n"
space: .asciiz " "
Myarray: .word 9 5 6 8 7 2
mangx: .word 0:20
mangy: .word 0:20
.text
main:
la $a0, Myarray # load dia chi myarray $a1
addi $t1, $zero,4 # size=20
and $a1, $zero, $zero # l=0 a1
addi $a3,$zero,3 #r=19
li $v0, 4
la $a0, text1 #in text1
syscall
li $v0, 4
la $a0, newline #in newline
syscall
and $t4, $zero, $zero # khoi tao i=0 $t4
j LoopPrintUn # nhay den ham in myarray
LoopPrintUn:
la $a0, Myarray # load dia chi myarray $a1
#While (i < length)
slt $t6, $t4, $t1 # neu i < size thi $t6=1, neu khong thi $t6=0
beq $t6, $zero, call # neu $t6=0 thi re qua ham in Sortedarray
# Load Array[i] and print it
sll $t0, $t4, 2 # i * 4
add $t6, $a0, $t0 # chuyen den dia chi phan tu thu i
li $v0, 1 # ham in integer
lw $a0, 0($t6) # load gia tri tai dia chi thu i
syscall # in
li $v0, 4
la $a0, space
syscall #in khoang trang
addi $t4, $t4, 1 # i ++
j LoopPrintUn # lap ham in myarray
MergeSort:
addi $sp, $sp, -20
sw $ra,0($sp)
sw $a3, 12($sp) # r
sw $a1, 8($sp) # l
sw $a0, 4($sp) # a[]
slt $t6, $a1, $a3 # neu l < r $t6=1 neu khong $t6=0
beq $t6, $zero, Exit2 # $t6=0 thi exit2
add $t1, $a1, $a3 # temp1 = l + r
div $t1, $t1, 2 # temp1 = temp1 / 2
add $a3,$t1,$zero
sw $t1,16($sp)
# add $a3, $a2, $zero # m=(l+r)/2 (m thay cho cho r trong mergesort(arr,l,r))
jal MergeSort # mergesort(arr,l,m)
lw $a1,16($sp) #load m
addi $a1,$a1,1
lw $a3,12($sp)#load r
#addi $sp, $sp, 24
jal MergeSort # mergesort(arr,m+1,r)
lw $a0, 4($sp)
lw $a1, 8($sp)
lw $a2, 16($sp)
lw $a3, 12($sp)
jal merge # merge(a,l,m,r)
Exit2:
lw $ra,0($sp)
lw $a0, 4($sp)
lw $a1, 8($sp)
lw $a2, 16($sp)
lw $a3, 12($sp)
addi $sp, $sp, 20
jr $ra
merge:
addi $sp,$sp,-32
sw $ra,0($sp)
sw $s0,4($sp) # bien i
sw $s1,8($sp) # bien j
sw $s2,12($sp) # bien k
sw $s3,16($sp) # bien n1
sw $s4,20($sp) # bien n2
sw $s5,24($sp) # mang X
sw $s6,28($sp) # mang y
la $s5,mangx
la $s6,mangy
sub $s3,$a2,$a1 # m-l
addi $s3,$s3,1 #m-l+1
sub $s4,$a3,$a2 # r-m
move $t0,$0 # bien dem o
move $t1,$0 # bien dem p
loop1:
slt $t3,$t0,$s3 # so sanh o<n1
beq $t3,$0,loop2 # go to toi loop 2 neu $t3=0
sll $t2,$t0,2 # o*4
add $t2,$s5,$t2 # X[0]
add $t5,$a1,$t0 # l+o
sll $t5,$t5,2 # (l+o)*4
add $t5,$a0,$t5 # arr[l+o]
lw $t5,0($t5)
sw $t5,0($t2) # x[o]=arr[l+o]
addi $t0,$t0,1 #o++
j loop1
loop2:
# xuly
slt $t4,$t1,$s4 # so sanh o<n1
beq $t4,$0,exit # go to toi exit neu $tt4=0
addi $t6,$a2,1 # m+1
add $t6,$t6,$t1 #m+1+p
sll $t6,$t6,2 #(m+1+p)*4
sll $t7,$t1,2 # p*4
add $t6,$a0,$t6 # arr[m+1+p]
lw $t6,0($t6)
add $t7,$s6,$t7 # y[p]
sw $t6,0($t7) # y[p]=arr[m+1+p]
addi $t1,$t1,1 #o++
j loop2
#-------------
exit:
move $s0,$0 #i=0
move $s1,$0 # j=0
add $s2,$a1,$0 #k=l
while:
slt $t0,$s0,$s3 #i<n1
beq $t0,$0,loop3
slt $t1,$s1,$s4 #j<n2
beq $t1,$0,loop3
sll $t2,$s0,2 #i*4
sll $t3,$s1,2 #j*4
add $t2,$s5,$t2 #x[i]
lw $t2,0($t2)
add $t3,$s6,$t3 #y[j]
lw $t3,0($t3)
slt $t6,$t2,$t3 # x[i]<y[j]
beq $t6,$0,else #x[i] >y[j] thì làm else còn x[i] <= y[j] lam if
sll $t7,$s2,2 #k*4
add $t7,$a0,$t7 #arr[k]
sw $t2,0($t7) #arr[k]=x[i]
addi $s0,$s0,1 #i++
addi $s2,$s2,1 #k++
else:
sll $t7,$s2,2 #k*4
add $t7,$a0,$t7 #arr[k]
sw $t3,0($t7) #arr[k]=y[j]
addi $s1,$s1,1 #j++
addi $s2,$s2,1 #k++
j while
loop3:
slt $t0,$s0,$s3 #i<n1
beq $t0,$0,loop4
sll $t1,$s2,2 #k*4
add $t1,$a0,$t1 #arr[k]
sll $t2,$s0,2 #i*4
add $t2,$s5,$t2 #x[i]
lw $t2,0($t2)
sw $t2,0($t1) #arr[k]=x[i]
addi $s0,$s0,1 #i++
addi $s2,$s2,1 #k++
j loop3
loop4:
slt $t0,$s1,$s4 #j<n2
beq $t0,$0,exit1
sll $t1,$s2,2 #k*4
add $t1,$a0,$t1 #arr[k]
sll $t2,$s1,2 #j*4
add $t2,$s6,$t2 #y[j]
lw $t2,0($t2)
sw $t2,0($t1) #arr[k]=y[j]
addi $s1,$s1,1 #j++
addi $s2,$s2,1 #k++
j loop4
exit1:
lw $ra,0($sp)
addi $sp,$sp,32
jr $ra
call:
jal MergeSort