Sta::findSlewLimit

Signed-off-by: James Cherry <cherry@parallaxsw.com>

sdc/Sdc.cc

@@ -779,7 +779,8 @@ Sdc::haveClkSlewLimits() const
 }
 
 void
-Sdc::slewLimit(Clock *clk, const RiseFall *rf,
+Sdc::slewLimit(Clock *clk,
+               const RiseFall *rf,
 	       const PathClkOrData clk_data,
 	       const MinMax *min_max,
 	       float &slew,
@@ -794,7 +795,7 @@ Sdc::slewLimit(Port *port,
 	       float &slew,
 	       bool &exists)
 {
-  slew = 0.0;
+  slew = INF;
   MinMaxFloatValues values;
   port_slew_limit_map_.findKey(port, values, exists);
   if (exists)
@@ -816,7 +817,7 @@ Sdc::slewLimit(Cell *cell,
 	       float &slew,
 	       bool &exists)
 {
-  slew = 0.0;
+  slew = INF;
   MinMaxFloatValues values;
   cell_slew_limit_map_.findKey(cell, values, exists);
   if (exists)

search/CheckSlewLimits.cc

@@ -255,18 +255,23 @@ CheckSlewLimits::findLimit(const LibertyPort *port,
 
   const Network *network = sta_->network();
   Sdc *sdc = sta_->sdc();
+  float limit1;
+  bool exists1;
 
   // Default to top ("design") limit.
   Cell *top_cell = network->cell(network->topInstance());
   sdc->slewLimit(top_cell, min_max,
-		 limit, exists);
+		 limit1, exists1);
+  if (exists1) {
+    limit = limit1;
+    exists = true;
+  }
 
   if (port) {
     const LibertyPort *corner_port = port->cornerPort(corner->libertyIndex(min_max));
-    float limit1;
-    bool exists1;
     corner_port->slewLimit(min_max, limit1, exists1);
     if (!exists1
+        // default_max_transition only applies to outputs.
         && corner_port->direction()->isAnyOutput()
         && min_max == MinMax::max())
       corner_port->libertyLibrary()->defaultMaxSlew(limit1, exists1);

search/Sta.cc

@@ -5219,7 +5219,8 @@ Sta::findSlewLimit(const LibertyPort *port,
                    float &limit,
                    bool &exists)
 {
-  checkSlewLimitPreamble();
+  if (check_slew_limits_ == nullptr)
+    makeCheckSlewLimits();
   check_slew_limits_->findLimit(port, corner, min_max,
                                 limit, exists);
 }