Fixed Spice reader: must not use Netlist::purge_nets to remove dummy nets. Updated golden test data.

src/db/db/dbCircuit.cc

@@ -575,7 +575,17 @@ void Circuit::connect_pin (size_t pin_id, Net *net)
   }
 }
 
+void Circuit::purge_nets_keep_pins ()
+{
+  do_purge_nets (true);
+}
+
 void Circuit::purge_nets ()
+{
+  do_purge_nets (false);
+}
+
+void Circuit::do_purge_nets (bool keep_pins)
 {
   std::vector<db::Net *> nets_to_be_purged;
   for (net_iterator n = begin_nets (); n != end_nets (); ++n) {
@@ -587,29 +597,35 @@ void Circuit::purge_nets ()
   std::set<size_t> pins_to_delete;
 
   for (std::vector<db::Net *>::const_iterator n = nets_to_be_purged.begin (); n != nets_to_be_purged.end (); ++n) {
-    for (db::Net::pin_iterator p = (*n)->begin_pins (); p != (*n)->end_pins (); ++p) {
-      pins_to_delete.insert (p->pin_id ());
+    if (! keep_pins) {
+      for (db::Net::pin_iterator p = (*n)->begin_pins (); p != (*n)->end_pins (); ++p) {
+        pins_to_delete.insert (p->pin_id ());
+      }
     }
     delete *n;
   }
 
-  //  remove the pin references of the pins we're going to delete
-  for (refs_iterator r = begin_refs (); r != end_refs (); ++r) {
-    db::SubCircuit *subcircuit = r.operator-> ();
-    for (std::set<size_t>::const_iterator p = pins_to_delete.begin (); p != pins_to_delete.end (); ++p) {
-      db::Net *net = subcircuit->net_for_pin (*p);
-      for (db::Net::subcircuit_pin_iterator sp = net->begin_subcircuit_pins (); sp != net->end_subcircuit_pins (); ++sp) {
-        if (sp->pin_id () == *p && sp->subcircuit () == subcircuit) {
-          net->erase_subcircuit_pin (sp);
-          break;
+  if (! pins_to_delete.empty ()) {
+
+    //  remove the pin references of the pins we're going to delete
+    for (refs_iterator r = begin_refs (); r != end_refs (); ++r) {
+      db::SubCircuit *subcircuit = r.operator-> ();
+      for (std::set<size_t>::const_iterator p = pins_to_delete.begin (); p != pins_to_delete.end (); ++p) {
+        db::Net *net = subcircuit->net_for_pin (*p);
+        for (db::Net::subcircuit_pin_iterator sp = net->begin_subcircuit_pins (); sp != net->end_subcircuit_pins (); ++sp) {
+          if (sp->pin_id () == *p && sp->subcircuit () == subcircuit) {
+            net->erase_subcircuit_pin (sp);
+            break;
+          }
         }
       }
     }
-  }
 
-  //  and actually remove those pins
-  for (std::set<size_t>::const_iterator p = pins_to_delete.begin (); p != pins_to_delete.end (); ++p) {
-    remove_pin (*p);
+    //  and actually remove those pins
+    for (std::set<size_t>::const_iterator p = pins_to_delete.begin (); p != pins_to_delete.end (); ++p) {
+      remove_pin (*p);
+    }
+
   }
 }
 

src/db/db/dbCircuit.h

@@ -713,10 +713,19 @@ public:
   /**
    *  @brief Purge unused nets
    *
-   *  This method will purge all nets which return "floating".
+   *  This method will purge all nets which return "is_passive".
+   *  Pins on these nets will also be removed.
    */
   void purge_nets ();
 
+  /**
+   *  @brief Purge unused nets but
+   *
+   *  This method will purge all nets which return "is_passive".
+   *  Pins on these nets will be kept but their net will be 0.
+   */
+  void purge_nets_keep_pins ();
+
   /**
    *  @brief Combine devices
    *
@@ -786,6 +795,7 @@ private:
   void set_netlist (Netlist *netlist);
   bool combine_parallel_devices (const db::DeviceClass &cls);
   bool combine_serial_devices (const db::DeviceClass &cls);
+  void do_purge_nets (bool keep_pins);
 
   void devices_changed ();
   void subcircuits_changed ();

src/db/db/dbNetlistSpiceReader.cc

@@ -282,15 +282,37 @@ void NetlistSpiceReader::read (tl::InputStream &stream, db::Netlist &netlist)
   }
 }
 
+/**
+ *  @brief Removes dummy nets which are just there to define a pin for a subcircuit
+ */
+static void
+remove_dummy_nets (db::Circuit &circuit)
+{
+  std::vector<db::Net *> nets_to_be_purged;
+  for (db::Circuit::net_iterator n = circuit.begin_nets (); n != circuit.end_nets (); ++n) {
+    if (n->subcircuit_pin_count () == 1 && (n->terminal_count () + n->pin_count ()) == 0) {
+      nets_to_be_purged.push_back (n.operator-> ());
+    }
+  }
+
+  for (std::vector<db::Net *>::const_iterator n = nets_to_be_purged.begin (); n != nets_to_be_purged.end (); ++n) {
+    delete *n;
+  }
+}
+
 void NetlistSpiceReader::finish ()
 {
   while (! m_streams.empty ()) {
     pop_stream ();
   }
 
-  //  purge nets with single connections (this way unconnected pins can be realized)
   if (mp_netlist) {
-    mp_netlist->purge_nets ();
+    //  purge nets with single connections (this way unconnected pins can be realized)
+    //  NOTE: we don't use Netlist::purge_nets as this method has too many side effects
+    db::NetlistLocker locker (mp_netlist);
+    for (db::Netlist::bottom_up_circuit_iterator c = mp_netlist->begin_bottom_up (); c != mp_netlist->end_bottom_up (); ++c) {
+      remove_dummy_nets (*c);
+    }
   }
 
   mp_stream.reset (0);

src/db/db/gsiDeclDbNetlist.cc

@@ -1316,8 +1316,16 @@ Class<db::Circuit> decl_dbCircuit (decl_dbNetlistObject, "db", "Circuit",
   ) +
   gsi::method ("purge_nets", &db::Circuit::purge_nets,
     "@brief Purges floating nets.\n"
-    "Floating nets can be created as effect of reconnections of devices or pins. "
-    "This method will eliminate all nets that make less than two connections."
+    "Floating nets are nets with no device or subcircuit attached to. Such floating "
+    "nets are removed in this step. If these nets are connected outward to a circuit pin, this "
+    "circuit pin is also removed."
+  ) +
+  gsi::method ("purge_nets_keep_pins", &db::Circuit::purge_nets_keep_pins,
+    "@brief Purges floating nets but keep pins.\n"
+    "This method will remove floating nets like \\purge_nets, but if these nets are attached "
+    "to a pin, the pin will be left disconnected from any net.\n"
+    "\n"
+    "This method has been introduced in version 0.26.2.\n"
   ),
   "@brief Circuits are the basic building blocks of the netlist\n"
   "A circuit has pins by which it can connect to the outside. Pins are "

testdata/algo/lvs_test2_au.lvsdb.1

@@ -951,11 +951,8 @@ reference(
   net(4 name('4'))
   net(5 name('6'))
   net(6 name('5'))
-  net(7 name('101'))
-  net(8 name('8'))
-  net(9 name('102'))
-  net(10 name('7'))
-  net(11 name('103'))
+  net(7 name('8'))
+  net(8 name('7'))
 
   # Outgoing pins and their connections to nets
   pin(1 name('1'))
@@ -986,26 +983,23 @@ reference(
    pin(0 4)
    pin(1 3)
    pin(2 4)
-   pin(3 7)
    pin(4 6)
-   pin(5 8)
+   pin(5 7)
    pin(6 3)
   )
   circuit(4 INV2PAIR name($4)
    pin(0 4)
    pin(1 3)
    pin(2 4)
-   pin(3 9)
-   pin(4 8)
-   pin(5 10)
+   pin(4 7)
+   pin(5 8)
    pin(6 3)
   )
   circuit(5 INV2PAIR name($5)
    pin(0 4)
    pin(1 3)
    pin(2 4)
-   pin(3 11)
-   pin(4 10)
+   pin(4 8)
    pin(5 5)
    pin(6 3)
   )
@@ -1090,11 +1084,8 @@ xref(
  )
  circuit(RINGO RINGO nomatch
   xref(
-   net(() 7 mismatch)
-   net(() 9 mismatch)
-   net(() 11 mismatch)
    net(() 6 mismatch)
-   net(() 8 mismatch)
+   net(() 7 mismatch)
    net(5 () mismatch)
    net(6 () mismatch)
    net(7 () mismatch)
@@ -1102,7 +1093,7 @@ xref(
    net(11 () mismatch)
    net(12 () mismatch)
    net(10 1 mismatch)
-   net(8 10 mismatch)
+   net(8 8 mismatch)
    net(1 5 mismatch)
    net(2 2 match)
    net(3 3 match)
@@ -1120,7 +1111,7 @@ xref(
    circuit(3 () mismatch)
    circuit(4 () mismatch)
    circuit(5 () mismatch)
-   circuit(1 1 mismatch)
+   circuit(1 1 match)
   )
  )
 )