#$a0 = n
#$v0 = retval
main:  nop;
       addi $a0, $0, 3;
       jal fib;
       #quit
       li $v0, 10
       syscall
fib:   nop;
       beq $a0, $0, returnZero;
       addi $t0, $0, 1;
       beq $a0, $t0, returnOne;

       #push $ra		# save return address
       sub $sp, $sp, 4;
       sw $ra, 0($sp);

       #push $a0		# save n
       sub $sp, $sp, 4;
       sw $a0, 0($sp);

       addi $a0, $a0, -1;
       jal fib;
       add $t0, $0, $v1;	# t0 = retval
       addi $a0, $a0, -1;

       #push $t0		# save first retval
       sub $sp, $sp, 4;
       sw $t0, 0($sp);

       jal fib;

       #pop $t0			# get the first retval back
       lw $t0, 0($sp);
       addi $sp, $sp, 4;

       add $v1, $t0, $v1	# retval = retval1 + retval2

       #pop $a0			# restore n
       lw $a0, 0($sp);
       add $sp, $sp, 4;

       #pop $ra			# restore return address
       lw $ra, 0($sp);
       addi $sp, $sp, 4;

       jr $ra;			# return

returnZero:
	add $v1, $0, $0;
	jr $ra;			# return
returnOne:
	add $v1, $t0, $0;	# retval = 1 + 0 = 1
	jr $ra;			# return