slide 15 of 23

Controlling Field Values

• 4 7-bit fields in 32-bit registers
• Partitioned addition:

  return(x + y);
  
  return((x + y) & 0x7f7f7f7f);
  

• Partitioned subtraction:

  return(a - b);
  
  return(((a | 0x80808080) - b) & 0x7f7f7f7f);
  

• Can optimize by tracking spacer values