CODEWITHSUNDEEP
assemblymips
zipzapzoop45
zipzapzoop45

Reputation: 49

adding all digits up to 10 in MIPS

i thought i had an idea how to do it using only add,sub,mult,addi,and,or,andi,ori,lw,sw,beq,bne,slt,slti,mflo.

i have to make sure every detail is in there, the stack pointer is clear etc.

any help solving this please? not for homework, just for studying for a test. i tried working it out and got it wrong, and just want to see a correct solution so i can see what i did wrong. i would ask my professor but he doesn't have office hours today and i need to figure this out tonight since i'm busy for the rest of the week

Upvotes: 0

Views: 1887

Answers (1)

Wiz
Wiz

Reputation: 2143

There is no real reason to do anything with the stack pointer unless we want to keep something on the stack. However in such a simple program, it's easier to work exclusively with registers. (using only add,sub,mult,addi,and,or,andi,ori,lw,sw,beq,bne,slt,slti,mflo.)

    .text
    .global main
main:
    addi    $t0, $zero, 10          # (counter) we will start with 10 and go down to zero
    add     $t1, $zero, $zero       # (sum) our sum, 0
count:
    add     $t1, $t1, $t0           # sum += counter
    addi    $t0, $t0, -1            # counter -= 1
    bne     $t0, $zero, count       # if (counter) goto count
    add     $v0, $zero, $t1         # return value, our sum
    #jr     $ra                     # return (jr not allowed?)

If you really wanted to utilize the stack to store the local variables (count and sum), you could do something like this. However, as you can see, it's a quite extensive and unnecessary.

    .text
    .global main
main:
    addi    $sp, $sp, -12       # Make room on the stack ($ra, sum, counter)
    sw      $ra, 0($sp)         # save the return address (not really needed)
    sw      $zero, 4($sp)       # sum variable, set to 0
    addi    $t0, $zero, 10
    sw      $t0, 8($sp)         # counter variable, set to 10
count:
    lw      $t0, 4($sp)         # load sum
    lw      $t1, 8($sp)         # load counter
    add     $t0, $t0, $t1       # sum += counter
    addi    $t1, $t1, -1        # counter -= 1
    sw      $t0, 4($sp)         # save the sum value
    sw      $t1, 8($sp)         # save the counter
    bne     $t1, $zero, count   # if (counter) goto count

    lw      $v0, 4($sp)         # return value, the sum
    lw      $ra, 0($sp)         # restore caller's address
    addi    $sp, $sp, 12        # pop the stack
    #jr     $ra                 # return to caller (jr not allowed?)

Upvotes: 1

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