[RWRoute] Preserve nodes of Laguna sinks

Signed-off-by: Eddie Hung <[email protected]>

src/com/xilinx/rapidwright/rwroute/RWRoute.java

@@ -56,6 +56,7 @@
 import com.xilinx.rapidwright.util.Pair;
 import com.xilinx.rapidwright.util.RuntimeTracker;
 import com.xilinx.rapidwright.util.RuntimeTrackerTree;
+import com.xilinx.rapidwright.util.Utils;
 
 import java.util.ArrayList;
 import java.util.Arrays;
@@ -616,6 +617,16 @@ protected NetWrapper createNetWrapperAndConnections(Net net) {
                 }
                 connection.setSinkRnode(sinkRnode);
 
+                if (sinkINTNode.getTile() != sink.getTile()) {
+                    TileTypeEnum sinkTileType = sink.getTile().getTileTypeEnum();
+                    if (Utils.isLaguna(sinkTileType)) {
+                        // Sinks in Laguna tiles must be Laguna registers (but will be projected into the INT tile)
+                        // however, it's possible for another net to use the sink node as a bounce -- prevent that here
+                        assert(sinkINTNode.getTile().getTileTypeEnum() == TileTypeEnum.INT);
+                        routingGraph.preserve(sink.getConnectedNode(), net);
+                    }
+                }
+
                 // Where appropriate, allow all 6 LUT pins to be swapped to begin with
                 char lutLetter = sink.getName().charAt(0);
                 int numberOfSwappablePins = (lutPinSwapping && sink.isLUTInputPin())