title: What are PIP alternative in arachne-pnr?
body: <p>While going through the <code>router.cc</code> the file of <code>arcahne-pnr</code>, I am unable to understand, how are the programmable interconnect pins PIPs routed? Does it seem PLL is representing the PIPs in the code? Could somebody help to make me clear, what corresponds to PIP in <code>arachne-pnr</code>?
  Thanks</p>