Dmp cleanup

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

dcalc/CcsCeffDelayCalc.cc

@@ -445,14 +445,13 @@ CcsCeffDelayCalc::findVlTime(double v,
 {
   double t_init = region_ramp_times_[0];
   double t_final = region_ramp_times_[region_count_];
-  bool root_fail = false;
-  double time = findRoot(
-      [&](double t, double &y, double &dy) {
-        vl(t, elmore, y, dy);
-        y -= v;
-      },
-      t_init, t_final + elmore * 3.0, .001, 20, root_fail);
-  vl_fail_ |= root_fail;
+  auto [time, failed] =
+    findRoot([&](double t, double &y, double &dy) {
+      vl(t, elmore, y, dy);
+      y -= v;
+    },
+      t_init, t_final + elmore * 3.0, .001, 20);
+  vl_fail_ |= failed;
   return time;
 }
 

dcalc/DmpCeff.hh

@@ -24,6 +24,9 @@
 
 #pragma once
 
+#include <optional>
+#include <utility>
+
 #include "LibertyClass.hh"
 #include "LumpedCapDelayCalc.hh"
 
@@ -71,13 +74,10 @@ protected:
                              // Return values.
                              double &wire_delay,
                              double &load_slew) = 0;
-  void gateDelaySlew(// Return values.
-                     double &delay,
-                     double &slew);
-  void loadDelaySlewElmore(const Pin *load_pin,
-                           double elmore,
-                           double &delay,
-                           double &slew);
+  std::pair<double, double> gateDelaySlew();
+  std::optional<std::pair<double, double>>
+  loadDelaySlewElmore(const Pin *load_pin,
+                      double elmore);
   // Select the appropriate special case Dartu/Menezes/Pileggi algorithm.
   void setCeffAlgorithm(const LibertyLibrary *library,
                         const LibertyCell *cell,

dcalc/DmpDelayCalc.cc

@@ -125,8 +125,12 @@ DmpCeffElmoreDelayCalc::loadDelaySlew(const Pin *load_pin,
   float elmore = 0.0;
   if (parasitic)
     parasitics_->findElmore(parasitic, load_pin, elmore, elmore_exists);
-  if (elmore_exists)
-    loadDelaySlewElmore(load_pin, elmore, wire_delay, load_slew);
+  if (elmore_exists) {
+    if (auto r = loadDelaySlewElmore(load_pin, elmore)) {
+      wire_delay = r->first;
+      load_slew = r->second;
+    }
+  }
   thresholdAdjust(load_pin, drvr_library, rf, wire_delay, load_slew);
 }
 

dcalc/FindRoot.cc

@@ -28,47 +28,38 @@
 
 namespace sta {
 
-double
+std::pair<double, bool>
 findRoot(FindRootFunc func,
          double x1,
          double x2,
          double x_tol,
-         int max_iter,
-         // Return value.
-         bool &fail)
+         int max_iter)
 {
   double y1, y2, dy1;
   func(x1, y1, dy1);
   func(x2, y2, dy1);
-  return findRoot(func, x1, y1, x2, y2, x_tol, max_iter, fail);
+  return findRoot(func, x1, y1, x2, y2, x_tol, max_iter);
 }
 
-double
+std::pair<double, bool>
 findRoot(FindRootFunc func,
          double x1,
          double y1,
          double x2,
          double y2,
          double x_tol,
-         int max_iter,
-         // Return value.
-         bool &fail)
+         int max_iter)
 {
   if ((y1 > 0.0 && y2 > 0.0) || (y1 < 0.0 && y2 < 0.0)) {
     // Initial bounds do not surround a root.
-    fail = true;
-    return 0.0;
+    return {0.0, true};
   }
 
-  if (y1 == 0.0) {
-    fail = false;
-    return x1;
-  }
+  if (y1 == 0.0)
+    return {x1, false};
 
-  if (y2 == 0.0) {
-    fail = false;
-    return x2;
-  }
+  if (y2 == 0.0)
+    return {x2, false};
 
   if (y1 > 0.0)
     // Swap x1/x2 so func(x1) < 0.
@@ -95,8 +86,7 @@ findRoot(FindRootFunc func,
     }
     if (std::abs(dx) <= x_tol * std::abs(root)) {
       // Converged.
-      fail = false;
-      return root;
+      return {root, false};
     }
 
     func(root, y, dy);
@@ -105,8 +95,7 @@ findRoot(FindRootFunc func,
     else
       x2 = root;
   }
-  fail = true;
-  return root;
+  return {root, true};
 }
 
 } // namespace

dcalc/FindRoot.hh

@@ -25,6 +25,7 @@
 #pragma once
 
 #include <functional>
+#include <utility>
 
 namespace sta {
 
@@ -33,24 +34,22 @@ using FindRootFunc = const std::function<void (double x,
                                                  double &y,
                                                  double &dy)>;
 
-double
+// first: root estimate; second: true if the search failed.
+std::pair<double, bool>
 findRoot(FindRootFunc func,
          double x1,
          double x2,
          double x_tol,
-         int max_iter,
-         // Return value.
-         bool &fail);
+         int max_iter);
 
-double
+// first: root estimate; second: true if the search failed.
+std::pair<double, bool>
 findRoot(FindRootFunc func,
          double x1,
          double y1,
          double x2,
          double y2,
          double x_tol,
-         int max_iter,
-         // Return value.
-         bool &fail);
+         int max_iter);
 
 } // namespace