##Stratis Frangos
## Fib.asm - generates the Fibonacci series
##
## Program which generates the Fibonacci series F(n) = F(n-1) + F(n-2), 
## F(n) = 0 if n=0
## F(n) =1  if n=1
## It generates it element by element, and stores the elements in memory.
##
## Register Legend
##
## 	$s0 - points to the begininning of the array
## 	$t0 - points to the current element of the fibonacci sequence
## 	$t1 - contains the count of elements
## 	$t2 - contains the f(n-1)
##	$t3 - contains the f(n-2)
##      $t4 - contains the SUM
##

#------------------------------------------------------------------------------
#         Text Section (Program)
#------------------------------------------------------------------------------

	.text            #tells assember program code starts here
	.globl main      #defines label for execution start
main:                    #execution starts here
	la $s0, arrayF   #$s0 will to elements
	la $t0, arrayF   #$t0 contains a the current element of arrayF
	li $t1, 0

Fib:
	slti $s1,$t1, 2
	bne  $s1,$zero, True

	sub  $t7, $t0,4
	sub  $t8, $t0,8
	add  $t9, $t7, $t8

	bltz $t9,overflow	# If $s1 <= 0, this checks if an overflow occured.
	sw $t9, ($t0)		# If no overflow occured, save the sum into last node in arrayF
	addi $t0, $t0, 4	# Incriment array node
        addi $t1,$t1,1		# Increment the counter (i=i+1)

	b Fib		        # Go back to the begining of fib function
	
	
True:
	sw $t1, ($t0)		# save the counter into last node in arrayF (n<2)
	addi $t0, $t0, 4	# Incriment by 1 array node
	addi $t1,$t1,1		# Increment the counter (i=i+1)
	j Fib
	

	
overflow:
	la $a0, func_overflowed	#
	li $v0, 4		# Print "Function overflowed at:"
	syscall			#

		
	move $a0, $t1		#
	li $v0, 1		# Prints the value at which overflow occured.
	syscall			#



exit:
	li $v0, 10
	syscall 		#Exit the program.

#----------------------------------------------------------------------------------
#	Data Segment
#----------------------------------------------------------------------------------


			.data
func_overflowed:	.asciiz "Overflow occurred when adding element "
arrayF:			.word 0, 1