Using QtSPIM write and test a program that calculates the fa

Using QtSPIM, write and test a program that calculates the factorial of N.

Solution

.data

print:

  

   .asciiz \"Odd: \"

    .text

    

fact:

   # ALLOCATE A FRAME FOR THE DYNAMIC LINK, RETURN ADDRESS,

    # AND STATIC LINK (TOTAL: 3*4 = 12 BYTES)

sw $fp, ($sp) # PUSH OLD FRAME POINTER (DYNAMIC LINK)

move    $fp, $sp    # FRAME POINTER NOW POINTS TO THE TOP OF STACK

    subu    $sp, $sp, 12    # ALLOCATE TWELVE BYTES IN THE STACK

# SAVE RETURN ADDRESS IN FRAME

   sw $ra, -4($fp)

   # SAVE STATIC LINK IN FRAME

    sw $v0, -8($fp)

   

# IF n>0 GOTO recurs (THE ARGUMENT n IS LOCATED AT 4($fp))

   lw $a0, 4($fp)

bgt $a0, 1, recurs

    # OTHERWISE RETURN 1

    li $v0, 1

    b   return

   

recurs:

    # PUSH n-1 AS THE ARGUMENT TO fact

    lw $a0, 4($fp)

    subu    $a0, $a0, 1

    sw $a0, ($sp)

subu    $sp, $sp, 4

    # LOAD STATIC LINK

    lw $v0, -8($fp)

   # CALL fact

    jal fact

    # MULTIPLY THE RESULT OF fact(n-1) BY n

   lw $a0, 4($fp)

   mul $v0, $v0, $a0

   

   addi $t0, 2

   lw $t2, 4($fp)

   div $t2, $t0

   mfhi $t1

   

    beq $t1, 0, return

   

    li $v0, 4

   la $a0, print

   syscall

   

    # PRINT res

    li $v0, 1

    lw $a0, answer

   syscall

return:

   # RETURN FROM fact (RESTORE REGISTERS AND POP FRAME)

    lw $ra, -4($fp)

    move    $sp, $fp

   lw $fp, ($sp) # RESTORE OLD FRAME POINTER

jr $ra

#

# The main program

#

   .text

   # main MUST BE GLOBAL

   .globl main

       

main:

   # ALLOCATE A FRAME FOR THE DYNAMIC LINK, RETURN ADDRESS, STATIC LINK,

    # AND FOR THE INTEGERS i AND res (TOTAL: 5*4 = 20 BYTES)

    sw $fp, ($sp) # PUSH OLD FRAME POINTER (DYNAMIC LINK)

    move    $fp, $sp    # FRAME POINTER NOW POINTS TO THE TOP OF STACK

    subu    $sp, $sp, 20    # ALLOCATE TWENTY BYTES IN THE STACK

   # SAVE RETURN ADDRESS IN FRAME

    sw $ra, -4($fp)

    # SAVE STATIC LINK IN FRAME

   sw $v0, -8($fp)

   

loop:

   # PRINT prompt

   .data

   

prompt:

   .asciiz \"Number? \"

    .text

    li $v0, 4

    la $a0, prompt

    syscall

    

    # READ i (i IS LOCATED AT -12($fp))

    li $v0, 5

    syscall

   sw $v0, -12($fp)

   

# IF i <= 0 GOTO EXIT

   blez    $v0, prompt

   # PUSH i

     lw $a0, -12($fp)

   sw $a0, ($sp)

    subu    $sp, $sp, 4

    # THE STATIC LINK OF fact IS THE FRAME POINTER OF main

    move    $v0, $fp

   # CALL fact

   jal fact

   # STORE THE RESULT OF fact(i) INTO res (res IS LOCATED AT -16($fp))

    sw $v0, -16($fp)

  

   # PRINT answer

    .data

   

answer:

    .asciiz \"The factorial is: \"

    .text

    li $v0, 4

    la $a0, answer

    syscall

   

    # PRINT res

    li $v0, 1

    lw $a0, -16($fp)

   syscall

    # PRINT END OF LINE

    .data

  

endl:

    .asciiz \"\ \"

    .text

    li $v0, 4

    la $a0, endl

    syscall

    # LOOP BACK

    b   loop

    

exit:

    # RETURN FROM main (RESTORE REGISTERS AND POP FRAME)

    lw $ra, -4($fp)

    move    $sp, $fp

    lw $fp, ($sp) # RESTORE OLD FRAME POINTER

    jr $ra