Speed up the connect(Nexus*,Link&) function somewhat.

This simplifies and reorganizes this function in order to improve
the performance of this function by a constant factor. I think we
really need to improve this by an entire order (and not just a
simple factor) but this helps.

net_link.cc

@@ -30,30 +30,39 @@
 # include  <malloc.h>
 #endif
 
-void connect(Nexus*l, Link&r)
+void Nexus::connect(Link&r)
 {
-      assert(l);
-
-      if (l == r.nexus_)
+      if (this == r.nexus_)
 	    return;
 
+      if (name_) {
+	    delete[]name_;
+	    name_ = 0;
+      }
+
 	// Special case: The "r" link is connected to nothing. The
 	// connect becomes trivially easy.
       if (r.nexus_ == 0) {
-	    l->relink(&r);
+	    if (r.get_dir() != Link::INPUT)
+		  driven_ = NO_GUESS;
+
+	    r.nexus_ = this;
+	    r.next_ = list_;
+	    list_ = &r;
 	    return;
       }
 
       Nexus*tmp = r.nexus_;
+      if (tmp->driven_ != Vz)
+	    driven_ = NO_GUESS;
+
       while (Link*cur = tmp->list_) {
 	    tmp->list_ = cur->next_;
-	    cur->nexus_ = 0;
-	    cur->next_  = 0;
-	    l->relink(cur);
+	    cur->nexus_ = this;
+	    cur->next_  = list_;
+	    list_ = cur;
       }
 
-      l->driven_ = Nexus::NO_GUESS;
-
       assert(tmp->list_ == 0);
       delete tmp;
 }
@@ -67,8 +76,8 @@ void connect(Link&l, Link&r)
 	    connect(r.nexus_, l);
       } else {
 	    Nexus*tmp = new Nexus;
-	    connect(tmp, l);
-	    connect(tmp, r);
+	    tmp->connect(l);
+	    tmp->connect(r);
       }
 }
 
@@ -89,8 +98,10 @@ Link::~Link()
 
 Nexus* Link::nexus()
 {
-      if (nexus_ == 0)
-	    (new Nexus()) ->relink(this);
+      if (nexus_ == 0) {
+	    Nexus*tmp = new Nexus;
+	    tmp->relink_(this);
+      }
       return nexus_;
 }
 
@@ -373,13 +384,8 @@ void Nexus::unlink(Link*that)
       that->next_ = 0;
 }
 
-void Nexus::relink(Link*that)
+void Nexus::relink_(Link*that)
 {
-      if (name_) {
-	    delete[] name_;
-	    name_ = 0;
-      }
-
 	/* If the link I'm adding is a driver for this nexus, then
 	   cancel my guess of the driven value. */
       if (that->get_dir() != Link::INPUT)

netlist.h

@@ -81,7 +81,6 @@ extern void join_island(NetPins*obj);
 class Link {
 
       friend void connect(Link&, Link&);
-      friend void connect(Nexus*, Link&);
       friend class NetPins;
       friend class Nexus;
 
@@ -325,13 +324,14 @@ class NetBranch  : public NetPins, public IslandBranch {
 class Nexus {
 
       friend void connect(Link&, Link&);
-      friend void connect(Nexus*, Link&);
       friend class Link;
 
     public:
       explicit Nexus();
       ~Nexus();
 
+      void connect(Link&r);
+
       const char* name() const;
       verinum::V get_init() const;
 
@@ -371,7 +371,7 @@ class Nexus {
     private:
       Link*list_;
       void unlink(Link*);
-      void relink(Link*);
+      void relink_(Link*);
 
       mutable char* name_; /* Cache the calculated name for the Nexus. */
       mutable ivl_nexus_t t_cookie_;
@@ -384,6 +384,8 @@ class Nexus {
       Nexus& operator= (const Nexus&);
 };
 
+inline void connect(Nexus*l, Link&r) { l->connect(r); }
+
 class NexusSet {
 
     public: