slide 21 of 23

Enable Masking

• Need to be able to "disable" PEs...
  but can't really turn them off
• Some partitioned compare instructions can be used to generate a bit mask...
• The basic "trick":

  where (c) a = b;
  
  t = (-!c);
  a = ((c & b) | ((~c) & a));
  

• Optimize by using masking only where:
  • Some PEs might be disabled
  • Not disabling could be observable