In MIPS assembly write a program that calculates the nth Fibonacci number throug

Question

In MIPS assembly write a program that calculates the nth Fibonacci number through recursion. Use a main function to get the nth number from the user and print out the result.

Please use Mars to run the program.

Explanation / Answer

# The following is the program in MIPS assembly for nth Fibonacci number through recursion. .text main: li $a0, 10 jal fib #Calling fibonacci through recursion move $a0, $v0 # from n to $a0 li $v0, 1 # result syscall li $v0, 4 syscall li $a0, 1 # $a0 must be equal to 1 li $a1, 0 # $a1 must be equal to 0 li $a2, 10 # $a2 equal to n jal fib # Calling fibonacci move $a0, $v0 li $v0, 1 # result syscall li $v0, 4 syscall li $v0, 4 la $a0, exit_str # print: "Enter to exit" syscall li $v0, 8 la $a0, new_str # Wait for enter to exit li $a1, 32 syscall exit_main: lw $ra, 12($sp) # Restore return address lw $fp, 8($sp) # Restore frame pointer addiu $sp, $sp, 24 # Pop stack frame jr $ra #int fib(int n) #{ # if (n == 0) # return 0; # else if (n == 1) # return 1; # else # return fib(n - 1) + fib(n - 2); #} # # # a0 = n, we use s0 fib: subu $sp, $sp, 32 # Allocate stack frame of 32 btyes sw $ra, 20($sp) # Save return address sw $fp, 16($sp) # Save frame pointer sw $s0, 12($sp) # Save s0 addiu $fp, $sp, 28 # Setup stack frame # if (n == 0) then return 0 B1_fib: seq $t0, $a0, $zero beq $t0, $zero, B2_fib # if (n != 0) ==> goto B2 li $v0, 0 # else ==> return zero j exit_fib # if (n == 1) then return 1 B2_fib: seq $t0, $a0, 1 beq $t0, $zero, B3_fib # if (n != 1) ==> goto B3 li $v0, 1 # else ==> return 1 j exit_fib # else return fib(n-1) + fib(n-2); B3_fib: subu $s0, $a0, 1 # Save n - 1 in s0 move $a0, $s0 # arg1 = n -1 jal fib subu $a0, $s0, 1 # arg1 = n -2 move $s0, $v0 # Save fib(n-1) jal fib add $v0, $v0, $s0 # Return fib(n-1) + fib(n-2) exit_fib: lw $ra, 20($sp) # Restore return address lw $fp, 16($sp) # Restore frame pointer lw $s0, 12($sp) # Restore s0 addiu $sp, $sp, 32 # Pop stack frame jr $ra # Return to caller # a, b = two previos Fib numbers, n = Fib number to generate # Must be called: Fib(1, 0, n) # #int fib_iter(int a, int b, int count) #{ # if (count == 1) # return b; # else # return fib_iter(a + b, a, count - 1); #} # # a0 = a, a1 = b, a2 = count fib_iter: # if (count == 1) then return b start_fib_iter: seq $t0, $a2, $zero beq $t0, $zero, B1_fib_iter # if (count != 0) ==> goto B1 move $v0, $a1 j exit_fib_iter # else return fiber_iter(a + b, a, count - 1) B1_fib_iter: add $t0, $a0, $a1 # t0 = a + b move $a1, $a0 # arg2 = a move $a0, $t0 # arg1 = a + b subu $a2, $a2, 1 # arg3 = count - 1 j start_fib_iter exit_fib_iter: jr $ra

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