As constant nets could start from many possible locations (e.g. every interconnect tile), the backwards estimate to some arbitrary location is largely meaningless in this mode, so just set it to zero so it doesn't cause problems.
Fixes the router2 performance issue raised in #1235.
As constant nets could start from many possible locations (e.g. every interconnect tile), the backwards estimate to some arbitrary location is largely meaningless in this mode, so just set it to zero so it doesn't cause problems.
Fixes the router2 performance issue raised in #1235.