The mask generated from the most significant bits section of the pointer includes bits corresponding to {HEAD ~ various regions} of {TAIL ~ the output mask} 
The mask generated from the most significant bits section of the pointer includes bits corresponding to { HEAD ~ various regions } of { TAIL ~ the output mask }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL