sta: prima reports -INF slew for an uncrossed threshold since OpenSTA e419f88d; ORFS asap7 swerv_wrapper CTS stops on RSZ-1008 #12037

diff --git a/dcalc/PrimaDelayCalc.cc b/dcalc/PrimaDelayCalc.cc
index 52cea8ff..f40a5cba 100644
--- a/dcalc/PrimaDelayCalc.cc
+++ b/dcalc/PrimaDelayCalc.cc
@@ -214,7 +214,10 @@ PrimaDelayCalc::gateDelays(ArcDcalcArgSeq &dcalc_args,
     return tableDcalcResults();
   else {
     simulate();
-    return dcalcResults();
+    if (thresholdsMeasured())
+      return dcalcResults();
+    debugPrint(debug_, "prima", 1, "threshold not crossed, using table models.");
+    return tableDcalcResults();
   }
 }
 
@@ -1053,6 +1056,31 @@ measuredSlew(double time1,
   return slew;
 }
 
+// True when the simulation crossed every threshold dcalcResults reads.
+bool
+PrimaDelayCalc::thresholdsMeasured()
+{
+  auto measured = [this](const Pin *pin) {
+    const ThresholdTimes &times = threshold_times_[pin_node_map_[pin]];
+    return !isUnset(times[threshold_vl])
+      && !isUnset(times[threshold_vth])
+      && !isUnset(times[threshold_vh]);
+  };
+  const Net *drvr_net = drvr_arg_->drvrNet(network_);
+  for (size_t drvr_idx = 0; drvr_idx < drvr_count_; drvr_idx++) {
+    ArcDcalcArg &dcalc_arg = (*dcalc_args_)[drvr_idx];
+    if (dcalc_arg.drvrNet(network_) == drvr_net) {
+      if (!measured(dcalc_arg.drvrPin()))
+        return false;
+      for (const auto [load_pin, load_idx] : *load_pin_index_map_) {
+        if (!measured(load_pin))
+          return false;
+      }
+    }
+  }
+  return true;
+}
+
 ArcDcalcResultSeq
 PrimaDelayCalc::dcalcResults()
 {
diff --git a/dcalc/PrimaDelayCalc.hh b/dcalc/PrimaDelayCalc.hh
index 3af74a3f..df53b893 100644
--- a/dcalc/PrimaDelayCalc.hh
+++ b/dcalc/PrimaDelayCalc.hh
@@ -173,6 +173,7 @@ protected:
   double voltagePrev1(size_t node_idx);
   double voltagePrev2(size_t node_idx);
   bool loadWaveformsFinished();
+  bool thresholdsMeasured();
   ArcDcalcResultSeq dcalcResults();
 
   void recordWaveformStep(double time);