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MIPS Runtime Error?

  1. Sep 27, 2012 #1
    Hi there,

    Not sure if this is the right place to post, but I seem to get a runtime error that says: address out of range 0x00000000. I think that it's probably in the first three lines of my code, but any idea as to what else it may be? Thanks so much!
    Code (Text):

        .data
    save:   .word 1,2,4
    size:   .word 3
        .text
       
    swap:   sll $t1, $a1, 2 #shift bits by 2
        add $t1, $a1, $t1 #set $t1 address to v[k]
        lw $t0, 0($t1) #load v[k] into t1 <--- ERROR
        #lw $t2, 4($t1) #load v[k+1] into t1
        #sw $t2, 0($t1) #swap addresses
        #sw $t0, 4($t1) #swap addresses
        jr $ra #return

    sort:   addi $sp, $sp, -20 #make enough room on the stack for five registers
        sw $ra, 16($sp) #save the return address on the stack
        sw $s3, 12($sp) #save $s3 on the stack
        sw $s2, 8($sp) #save Ss2 on the stack
        sw $s1, 4($sp) #save $s1 on the stack
        sw $s0, 0($sp) #save $s0 on the stack
       
        move $s2, $a0 #copy the parameter $a0 into $s2 (save $a0)
        move $s3, $a1 #copy the parameter $a1 into $s3 (save $a1)
        move $s0, $zero #start of for loop, i = 0
    for1tst: slt $t0, $s0, $s3 #$t0 = 0 if $s0 S $s3 (i S n)
        beq $t0, $zero, exit1 #go to exit1 if $s0 S $s3 (i S n)
        addi $s1, $s0, -1 #j - i - 1
    for2tst: slti $t0, $s1, 0 #$t0 = 1 if $s1 < 0 (j < 0)
        bne $t0, $zero, exit2 #$t0 = 1 if $s1 < 0 (j < 0)
        sll $t1, $s1, 2 #$t1 = j * 4 (shift by 2 bits)
        add $t2, $s2, $t1 #$t2 = v + (j*4)
        lw $t3, 0($t2) #$t3 = v[j]
        lw $t4, 4($t2) #$t4 = v[j+1]
        slt $t0, $t4, $t3 #$t0 = 0 if $t4 S $t3
        beq $t0, $zero, exit2 #go to exit2 if $t4 S $t3
        move $a0, $s2 #1st parameter of swap is v(old $a0)
        move $a1, $s1 #2nd parameter of swap is j
        jal swap #swap
        addi $s1, $s1, -1
        j for2tst #jump to test of inner loop
        j print
    exit2:
        addi $s0, $s0, 1 #i = i + 1
        j for1tst #jump to test of outer loop
       
    exit1:
        lw $s0, 0($sp) #restore $s0 from stack
        lw $s1, 4($sp) #resture $s1 from stack
        lw $s2, 8($sp) #restore $s2 from stack
        lw $s3, 12($sp) #restore $s3 from stack
        lw $ra, 16($sp) #restore $ra from stack
        addi $sp, $sp, 20 #restore stack pointer
        jr $ra #return to calling routine
       
        .data
    space:.asciiz  " "          # space to insert between numbers
    head: .asciiz  "The sorted numbers are:\n"
          .text
    print:add  $t0, $zero, $a0  # starting address of array
          add  $t1, $zero, $a1  # initialize loop counter to array size
          la   $a0, head        # load address of print heading
          li   $v0, 4           # specify Print String service
          syscall               # print heading
    out:
          li   $v0, 1           # specify Print Integer service
          la   $a0, space       # load address of spacer for syscall
          li   $v0, 4           # specify Print String service
          syscall               # output string
          addi $t0, $t0, 4      # increment address
          addi $t1, $t1, -1     # decrement loop counter
          bgtz $t1, out         # repeat if not finished
          jr   $ra              # return
     
     
  2. jcsd
  3. Sep 28, 2012 #2

    chiro

    User Avatar
    Science Advisor

    Hey m00nbeam360.

    Just out of curiosity, have you run this code through a low level debugger where you get access to the register values? (Even if you have to use some sort of emulator program)

    I can't really speculate what it's in the values, but if you for example over-writing a value or trying to load in the contents at address 0x0 when something has been cleared then the register contents will reflect that.

    Also are those numbers in your mneumonics some kind of offset you provide with the register?
     
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