Delay Slot Bug

The program can be made slightly shorter by removing the no-op instruction filling the first delay slot. The instruction following it (the sltiu) will always execute, sometimes uselessly, but never will do damage.

# Set range indicator to 1
        ori     $3,$0,1         #  set to 1

# Test  30 <= temp <= 55
        sltiu   $8,$2,56        #  $8=1 if temp <= 55
        beq     $8,$0,out       #  0? out of range
        sll     $0,$0,0         #  delay

        sltiu   $8,$2,30        #  $8=1 if  temp < 30
        beq     $8,$0,cont      #  0? in range
        sll     $0,$0,0         #  delay

# Out of Range: set range indicator to 0
out:
        ori     $3,$0,0         #  clear to 0

cont:   sll     $0,$0,0         #  target for the jump
## End of file

The second no-op, however, is essential. If it is missing, the next instruction, the ori sets the flag to zero regardless of the branch instruction. This is a common bug, and can be very frustrating because sometimes the result is correct.