# signedOF.s
# MIPS program written to illustrate signed addition overflow detected manually
# Susan Haller 2/17/03
# Modified: Susan Lincke 2/20/05

	.data
a:	.word  0x7fffffff

	.text   
	.globl main   
main:
	la     $a0,  a                 # t1 = 0x7fffffff
	lw     $t1, 0($a0)             
	move   $t2,$t1                 # t2 = 0x7fffffff

	addu   $t0, $t1,   $t2         # t0 = t1 + t2
	xor    $t3, $t1,   $t2         # If (t1.sign != t2.sign ||
	blt    $t3, $zero, noOverflow  # 
	xor    $t3, $t0,   $t1         #   t0.sign == t1.sign)
	blt    $t3, $zero, overflow    

noOverflow:                            #   // No overflow occured 
	addi   $t0, $zero, 1           #   return = '1'    // no overflow
	b      end
overflow:	                       # Else // Overflowed occured
	addi   $t0, $zero, 2	       #   return = '2'    // overflow
end:	
	li     $v0, 10           
	syscall               # system call(exit)