Shifting the Sign Bit

To determine if "A" is negative, check if its sign bit is one. To do this, logically shift the sign bit into bit position 0 of a register. The register will be zero if "A" is positive. The program assumes that integer values are represented with two's complement.

## absVal.asm
##
## Calculate the absolute value of A

      .text
      .globl  main

main: 
# Get A
        lui   $10,0x1000     #  Initialize the base register
        lw    $8,0($10)      #  Load A
        sll   $0,$0,0        #  no-op

# Is A negative?
        srl   $9,$8,_____       #  Shift sign bit to position 0
        beq   $___,$_____,done  #  sign bit == zero, done
        sll   $0,$0,0


# Store -A


done:   

      .data
A:    .word   -1

## End of file

The branch delay slot is filled with a no-op.