limited sizeup match to single fanouts only

Signed-off-by: Cho Moon <cmoon@precisioninno.com>

Author: precisionmoon

src/rsz/src/SizeUpMove.cc

@@ -10,6 +10,7 @@
 #include "CloneMove.hh"
 #include "sta/ArcDelayCalc.hh"
 #include "sta/Delay.hh"
+#include "sta/Graph.hh"
 #include "sta/Liberty.hh"
 #include "sta/NetworkClass.hh"
 #include "sta/Path.hh"
@@ -35,6 +36,7 @@ using sta::PathExpanded;
 using sta::Pin;
 using sta::Slack;
 using sta::Slew;
+using sta::VertexOutEdgeIterator;
 
 bool SizeUpMove::doMove(const Path* drvr_path,
                         int drvr_index,
@@ -140,11 +142,26 @@ bool SizeUpMatchMove::doMove(const Path* drvr_path,
     if (prev_drvr_pin == nullptr) {
       return false;
     }
+    Vertex* prev_drvr_vertex = graph_->pinDrvrVertex(prev_drvr_pin);
+    if (prev_drvr_vertex == nullptr) {
+      return false;
+    }
+    // Skip if the previous driver has multi fanout
+    int fanout = 0;
+    VertexOutEdgeIterator edge_iter(prev_drvr_vertex, graph_);
+    while (edge_iter.hasNext()) {
+      (void) edge_iter.next();
+      fanout++;
+      if (fanout > 1) {
+        return false;
+      }
+    }
+
     LibertyPort* prev_drvr_port = network_->libertyPort(prev_drvr_pin);
     if (prev_drvr_port == nullptr) {
       return false;
     }
-    const LibertyCell* prev_cell = prev_drvr_port->libertyCell();
+    LibertyCell* prev_cell = prev_drvr_port->libertyCell();
     if (prev_cell == nullptr) {
       return false;
     }

src/rsz/test/repair_fanout6.ok

@@ -25,9 +25,9 @@ fanout1/X                                20     20      0 (MET)
           | Buffers |  Gates  | Buffers  |  Gates | Swaps |          |          |            | Endpts | Endpt
 --------------------------------------------------------------------------------------------------------------
         0 |       0 |       0 |        0 |      0 |     0 |    +0.0% |  -32.280 |  -188759.2 |   8000 | sink7689/D
-    final |       0 |     232 |       28 |      0 |     0 |    +0.3% |   -5.818 |   -11716.7 |   5340 | sink7534/D
+    final |       0 |     232 |       28 |      0 |     0 |    +0.3% |   -5.740 |   -11564.6 |   5340 | sink7534/D
 --------------------------------------------------------------------------------------------------------------
 [INFO RSZ-0040] Inserted 28 buffers.
-[INFO RSZ-0051] Resized 232 instances: 231 up, 1 up match, 0 down, 0 VT
+[INFO RSZ-0051] Resized 232 instances: 232 up, 0 up match, 0 down, 0 VT
 [WARNING RSZ-0062] Unable to repair all setup violations.
-worst slack max -5.82
+worst slack max -5.74

src/rsz/test/repair_fanout7.ok

@@ -13,11 +13,11 @@ tns max -6.294
           | Buffers |  Gates  | Buffers  |  Gates | Swaps |          |          |            | Endpts | Endpt
 --------------------------------------------------------------------------------------------------------------
         0 |       0 |       0 |        0 |      0 |     0 |    +0.0% |   -1.954 |       -6.3 |      6 | r2/D
-    final |       5 |      13 |        7 |      0 |     0 |   +20.1% |   -0.326 |       -1.8 |      6 | r7/D
+    final |       5 |      11 |        7 |      0 |     0 |   +20.1% |   -0.326 |       -1.8 |      6 | r7/D
 --------------------------------------------------------------------------------------------------------------
 [INFO RSZ-0059] Removed 5 buffers.
 [INFO RSZ-0040] Inserted 7 buffers.
-[INFO RSZ-0051] Resized 13 instances: 11 up, 2 up match, 0 down, 0 VT
+[INFO RSZ-0051] Resized 11 instances: 11 up, 0 up match, 0 down, 0 VT
 [WARNING RSZ-0062] Unable to repair all setup violations.
 Repair timing output passed/skipped equivalence test
 worst slack max -0.33