RouterHelper.invertPossibleGndPinsToVccPins() to invert static LUT inputs

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

@@ -482,7 +482,8 @@ protected void routeStaticNets() {
 
         List<SitePinInst> gndPins = staticNetAndRoutingTargets.get(design.getGndNet());
         if (gndPins != null) {
-            Set<SitePinInst> newVccPins = RouterHelper.invertPossibleGndPinsToVccPins(design, gndPins);
+            boolean invertGndToVccForLutInputs = config.isInvertGndToVccForLutInputs();
+            Set<SitePinInst> newVccPins = RouterHelper.invertPossibleGndPinsToVccPins(design, gndPins, invertGndToVccForLutInputs);
             if (!newVccPins.isEmpty()) {
                 gndPins.removeAll(newVccPins);
                 staticNetAndRoutingTargets.computeIfAbsent(design.getVccNet(), (net) -> new ArrayList<>())

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

@@ -1,7 +1,7 @@
 /*
  *
  * Copyright (c) 2021 Ghent University.
- * Copyright (c) 2022-2023, Advanced Micro Devices, Inc.
+ * Copyright (c) 2022-2024, Advanced Micro Devices, Inc.
  * All rights reserved.
  *
  * Author: Yun Zhou, Ghent University.
@@ -92,6 +92,8 @@ public class RWRouteConfig {
     private boolean lutPinSwapping;
     /* true to enable LUT routethru */
     private boolean lutRoutethru;
+    /* true to enable GND -> VCC optimization for LUT inputs */
+    private boolean invertGndToVccForLutInputs;
 
     /** Constructs a Configuration Object */
     public RWRouteConfig(String[] arguments) {
@@ -122,6 +124,7 @@ public RWRouteConfig(String[] arguments) {
         printConnectionSpan = false;
         lutPinSwapping = false;
         lutRoutethru = false;
+        invertGndToVccForLutInputs = true;
         if (arguments != null) {
             parseArguments(arguments);
         }
@@ -227,6 +230,9 @@ private void parseArguments(String[] arguments) {
             case "--lutRoutethru":
                 setLutRoutethru(true);
                 break;
+            case "--noInvertGndToVccForLutInputs":
+                setInvertGndToVccForLutInputs(false);
+                break;
             default:
                 throw new IllegalArgumentException("ERROR: RWRoute argument '" + arg + "' not recognized.");
             }
@@ -737,6 +743,16 @@ public boolean isLutRoutethru() {
         return lutRoutethru;
     }
 
+    /**
+     * Gets the flag indicating if GND to VCC inversion for LUT inputs is enabled.
+     * Default: true.
+     *
+     * @return True if the flag is set, false otherwise.
+     */
+    public boolean isInvertGndToVccForLutInputs() {
+        return invertGndToVccForLutInputs;
+    }
+
     /**
      * Sets critical path delay pessimism factor b. It should be greater than 0.
      * Default: 100. Can be modified by using "--pessimismB" option, e.g.
@@ -850,6 +866,16 @@ public void setLutRoutethru(boolean lutRoutethru) {
         this.lutRoutethru = lutRoutethru;
     }
 
+    /**
+     * Sets the flag for enabling GND to VCC inversion for LUT inputs.
+     * Default: true.
+     *
+     * @param invertGndToVccForLutInputs true to enableGND to VCC inversion for LUT inputs.
+     */
+    public void setInvertGndToVccForLutInputs(boolean invertGndToVccForLutInputs) {
+        this.invertGndToVccForLutInputs = invertGndToVccForLutInputs;
+    }
+
     /**
      * Sets verbose.
      * If true, there will be more info in the routing log file regarding design netlist, routing statistics, and timing report.

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

@@ -1,7 +1,7 @@
 /*
  *
  * Copyright (c) 2021 Ghent University.
- * Copyright (c) 2022-2023, Advanced Micro Devices, Inc.
+ * Copyright (c) 2022-2024, Advanced Micro Devices, Inc.
  * All rights reserved.
  *
  * Author: Yun Zhou, Ghent University.
@@ -39,17 +39,22 @@
 import java.util.Queue;
 import java.util.Set;
 
+import com.xilinx.rapidwright.design.Cell;
 import com.xilinx.rapidwright.design.Design;
 import com.xilinx.rapidwright.design.DesignTools;
 import com.xilinx.rapidwright.design.Net;
+import com.xilinx.rapidwright.design.SiteInst;
 import com.xilinx.rapidwright.design.SitePinInst;
+import com.xilinx.rapidwright.design.tools.LUTTools;
+import com.xilinx.rapidwright.device.BEL;
 import com.xilinx.rapidwright.device.BELPin;
 import com.xilinx.rapidwright.device.IntentCode;
 import com.xilinx.rapidwright.device.Node;
 import com.xilinx.rapidwright.device.PIP;
 import com.xilinx.rapidwright.device.Tile;
 import com.xilinx.rapidwright.device.TileTypeEnum;
 import com.xilinx.rapidwright.device.Wire;
+import com.xilinx.rapidwright.edif.EDIFHierCellInst;
 import com.xilinx.rapidwright.timing.TimingEdge;
 import com.xilinx.rapidwright.timing.TimingManager;
 import com.xilinx.rapidwright.timing.delayestimator.DelayEstimatorBase;
@@ -366,43 +371,121 @@ private static boolean isInvertibleDSPBELPin(BELPin belPin) {
     /**
      * Inverts all possible GND sink pins to VCC pins.
      * @param design The target design.
-     * @param pins The static net pins.
+     * @param pins The GND net pins.
      */
     public static Set<SitePinInst> invertPossibleGndPinsToVccPins(Design design, List<SitePinInst> pins) {
-        Net staticNet = design.getGndNet();
+        return invertPossibleGndPinsToVccPins(design, pins, true);
+    }
+
+    /**
+     * Inverts all possible GND sink pins to VCC pins.
+     * @param design The target design.
+     * @param pins The GND net pins.
+     * @param invertLutInputs True to invert LUT inputs.
+     */
+    public static Set<SitePinInst> invertPossibleGndPinsToVccPins(Design design,
+                                                                  List<SitePinInst> pins,
+                                                                  boolean invertLutInputs) {
+        Net gndNet = design.getGndNet();
         Set<SitePinInst> toInvertPins = new HashSet<>();
-        for (SitePinInst currSitePinInst : pins) {
-            if (!currSitePinInst.getNet().equals(staticNet))
-                throw new RuntimeException(currSitePinInst.toString());
-            BELPin[] belPins = currSitePinInst.getSiteInst().getSiteWirePins(currSitePinInst.getName());
-            if (belPins.length != 2) {
-                continue;
-            }
-            for (BELPin belPin : belPins) {
-                if (belPin.isSitePort()) {
-                    continue;
+        nextSitePin: for (SitePinInst spi : pins) {
+            if (!spi.getNet().equals(gndNet))
+                throw new RuntimeException(spi.toString());
+            SiteInst si = spi.getSiteInst();
+            String siteWireName = spi.getSiteWireName();
+            if (invertLutInputs && spi.isLUTInputPin()) {
+                Collection<Cell> connectedCells = DesignTools.getConnectedCells(spi);
+                if (connectedCells.isEmpty()) {
+                    for (BELPin belPin : si.getSiteWirePins(siteWireName)) {
+                        if (belPin.isSitePort()) {
+                            continue;
+                        }
+                        BEL bel = belPin.getBEL();
+                        Cell cell = si.getCell(bel);
+                        if (cell == null) {
+                            continue;
+                        }
+                        if (cell.getType().equals("SRL16E") && siteWireName.endsWith("6")) {
+                            // SRL16Es that have been transformed from SRLC32E (assume so here,
+                            // since we don't always have the logical netlist to check)
+                            // require GND on their A6 pin
+                            // See DesignTools.createMissingStaticSitePins(BELPin, SiteInst, Cell)
+                            continue nextSitePin;
+                        }
+                    }
+                    throw new RuntimeException("ERROR: " + gndNet.getName() + " not connected to any Cells");
                 }
-                if (!belPin.getBEL().canInvert()) {
+                for (Cell cell : connectedCells) {
+                    if (!LUTTools.isCellALUT(cell)) {
+                        continue nextSitePin;
+                    }
+
+                    EDIFHierCellInst ehci = cell.getEDIFHierCellInst();
+                    if (ehci == null) {
+                        // No logical cell (likely encrypted)
+                        continue nextSitePin;
+                    }
+
+                    if (!ehci.getParent().isUniquified()) {
+                        // Parent cell (instantiating this LUT) is not unique
+                        // This parent may be a LUT6_2 macro cell that has been expanded into LUT6+LUT5,
+                        // and which does not get uniquified by EDIFTools.uniqueifyNetlist().
+                        // Thus, LUT6/LUT5 inside expanded LUT6_2 macros are not eligible for inversion.
+                        continue nextSitePin;
+                    }
+                }
+
+                toInvertPins.add(spi);
+
+                for (Cell cell : connectedCells) {
+                    // Find the logical pin name
+                    String physicalPinName = "A" + spi.getName().charAt(1);
+                    String logicalPinName = cell.getLogicalPinMapping(physicalPinName);
+
+                    // Get the LUT equation
+                    String lutEquation = LUTTools.getLUTEquation(cell);
+                    assert(lutEquation.contains(logicalPinName));
+
+                    // Compute a new LUT equation with that logical input inverted
+                    String newLutEquation = lutEquation.replace(logicalPinName, "!" + logicalPinName)
+                            // Cancel out double inversions
+                            // (Note: LUTTools.getLUTEquation() only produces equations with '!' instead of '~')
+                            .replace("!!", "");
+                    LUTTools.configureLUT(cell, newLutEquation);
+                }
+            } else {
+                BELPin[] belPins = si.getSiteWirePins(siteWireName);
+                if (belPins.length != 2) {
                     continue;
                 }
-                if (currSitePinInst.getSite().getName().startsWith("RAM")) {
-                    if (belPin.getBELName().startsWith("CLK")) {
+                for (BELPin belPin : belPins) {
+                    if (belPin.isSitePort()) {
+                        continue;
+                    }
+                    if (!belPin.getBEL().canInvert()) {
                         continue;
                     }
+                    if (spi.getSite().getName().startsWith("RAM")) {
+                        if (belPin.getBELName().startsWith("CLK")) {
+                            continue;
+                        }
+                    }
+                    toInvertPins.add(spi);
                 }
-                toInvertPins.add(currSitePinInst);
-           }
+            }
         }
 
         // Unroute all pins in a batch fashion
-        DesignTools.unroutePins(staticNet, toInvertPins);
+        DesignTools.unroutePins(gndNet, toInvertPins);
         // Manually remove pins from net, because using DesignTools.batchRemoveSitePins()
         // will cause SitePinInst.detachSiteInst() to be called, which we do not want
         // as we are simply moving the SPI from one net to another
-        staticNet.getPins().removeAll(toInvertPins);
+        gndNet.getPins().removeAll(toInvertPins);
+
+        Net vccNet = design.getVccNet();
         for (SitePinInst toinvert:toInvertPins) {
             assert(toinvert.getSiteInst() != null);
-            if (!design.getVccNet().addPin(toinvert)) {
+            if (!vccNet.addPin(toinvert)) {
                   throw new RuntimeException("ERROR: Couldn't invert site pin " +
                           toinvert);
             }

test/shared/com/xilinx/rapidwright/support/rwroute/RouterHelperSupport.java

@@ -0,0 +1,60 @@
+/*
+ * Copyright (c) 2024, Advanced Micro Devices, Inc.
+ * All rights reserved.
+ *
+ * Author: Eddie Hung, Advanced Micro Devices, Inc.
+ *
+ * This file is part of RapidWright.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+package com.xilinx.rapidwright.support.rwroute;
+
+import com.xilinx.rapidwright.design.Cell;
+import com.xilinx.rapidwright.design.Design;
+import com.xilinx.rapidwright.design.SiteInst;
+import com.xilinx.rapidwright.design.SitePinInst;
+import com.xilinx.rapidwright.design.tools.LUTTools;
+import com.xilinx.rapidwright.device.BELPin;
+
+import java.util.Set;
+
+public class RouterHelperSupport {
+    public static void invertVccLutPinsToGndPins(Design design, Set<SitePinInst> pins) {
+        for (SitePinInst spi : pins) {
+            assert (spi.getNet() == design.getVccNet());
+            SiteInst si = spi.getSiteInst();
+            for (BELPin bp : spi.getSiteWireBELPins()) {
+                if (bp.isSitePort() || bp.getName().charAt(0) != 'A')
+                    continue;
+                if (bp.getBEL().isLUT()) {
+                    Cell lut = si.getCell(bp.getBEL());
+                    if (lut != null) {
+                        String eq = LUTTools.getLUTEquation(lut);
+                        String logInput = lut.getLogicalPinMapping(bp.getName());
+                        if (logInput != null) {
+                            LUTTools.configureLUT(lut, eq.replace(logInput, "(~" + logInput + ")"));
+                        } else {
+                            // Doesn't look like this pin is used by this [65]LUT,
+                            // could be used by the other [56]LUT
+                        }
+                    }
+                }
+            }
+            spi.getNet().removePin(spi, true);
+            design.getGndNet().addPin(spi, true);
+        }
+    }
+}

test/src/com/xilinx/rapidwright/edif/TestEDIFCellInst.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2023, Advanced Micro Devices, Inc.
+ * Copyright (c) 2023-2024, Advanced Micro Devices, Inc.
  * All rights reserved.
  *
  * Author: Eddie Hung, Advanced Micro Devices, Inc.
@@ -78,7 +78,7 @@ public void testIsUniquifiedFalse() {
         )) {
             EDIFCellInst eci = picoblazeTop.getCellInst(name);
             // Only checks that this cell instance is unique (e.g. that there is only
-            // one instantiation) but does not check that any parents on a full
+            // one instantiation) but does not check that all parents on a full
             // hierarchical path (e.g. "picoblaze_{0,1}_{12,13}/processor") is also
             // unique --- use EDIFHierCellInst.isUniquified() for that
             Assertions.assertTrue(eci.isUniquified());

test/src/com/xilinx/rapidwright/rwroute/TestRWRoute.java

@@ -336,7 +336,7 @@ public void testRWRouteDeviceSupport(Series series) {
     public void testBug701() {
         Design design = RapidWrightDCP.loadDCP("bug701.dcp");
 
-        RWRoute.routeDesignFullNonTimingDriven(design);
+        RWRoute.routeDesignWithUserDefinedArguments(design, new String[] {"--nonTimingDriven", "--noInvertGndToVccForLutInputs"});
 
         Net vcc = design.getVccNet();
         Assertions.assertEquals(1, vcc.getPins().size());