From dd284ee582503377c3025c14ca892652e60cf5cd Mon Sep 17 00:00:00 2001
From: Martin Whitaker <icarus@martin-whitaker.me.uk>
Date: Fri, 13 Jul 2012 19:28:16 +0100
Subject: [PATCH] Additional support for $countdrivers.

This patch extends the implementation of $countdrivers to handle wires
connected to islands.
---
 vvp/island_tran.cc | 75 ++++++++++++++++++++++++++++++++++++++++++----
 vvp/vvp_island.cc  |  7 -----
 vvp/vvp_island.h   | 15 +++++++++-
 3 files changed, 84 insertions(+), 13 deletions(-)

diff --git a/vvp/island_tran.cc b/vvp/island_tran.cc
index a3dee08ea..ac9a96604 100644
--- a/vvp/island_tran.cc
+++ b/vvp/island_tran.cc
@@ -106,16 +106,81 @@ void vvp_island_tran::run_island()
       }
 }
 
-static bool warn_count_drivers = true;
+static void count_drivers_(vvp_branch_ptr_t cur, bool other_side_visited,
+                           unsigned bit_idx, unsigned counts[3])
+{
+        // First count any value driven into the port associated with
+        // the current endpoint.
+      vvp_net_t*net = cur.port() ? cur.ptr()->b : cur.ptr()->a;
+      vvp_scalar_t bit = island_get_value(net).value(bit_idx);
+      update_driver_counts(bit.value(), counts);
+
+        // Now handle all the branches attached to that port.
+      vvp_branch_ptr_t idx = cur;
+      do {
+            vvp_island_branch_tran*tmp = BRANCH_TRAN(idx.ptr());
+
+              // If this branch represents a tran gate, we count the
+              // value on the other side of the tran (providing it is
+              // enabled) as a single driver.
+            if (tmp->width == 0) {
+                  if (tmp->state == tran_enabled) {
+                        net = idx.port() ? idx.ptr()->a : idx.ptr()->b;
+                        bit = island_get_sent_value(net).value(bit_idx);
+                        update_driver_counts(bit.value(), counts);
+                  }
+                  continue;
+            }
+
+              // If we get here, this branch is a part select. If we've
+              // just come from the other end of the branch, we're done.
+            if ((idx == cur) && other_side_visited)
+                  continue;
+
+              // If this is the narrow end of the part select, the other
+              // end must include the bit we are interested in. Follow
+              // the branch to collect any drivers on the other side.
+            if (idx.port() == 1) {
+                  vvp_branch_ptr_t a_side(tmp, 0);
+                  count_drivers_(a_side, true, tmp->offset + bit_idx, counts);
+                  continue;
+            }
+
+              // If we get here, this branch is the wide end of a part
+              // select. If the bit we are interested in is within the
+              // selected part, follow the branch to collect any drivers
+              // on the other side.
+            if ((bit_idx >= tmp->offset) && (bit_idx < tmp->offset+tmp->part)) {
+                  vvp_branch_ptr_t b_side(tmp, 1);
+                  count_drivers_(b_side, true, bit_idx - tmp->offset, counts);
+                  continue;
+            }
+      } while ((idx = next(idx)) != cur);
+}
 
 void vvp_island_tran::count_drivers(vvp_island_port*port, unsigned bit_idx,
                                     unsigned counts[3])
 {
-      if (warn_count_drivers) {
-            cerr << "sorry: $countdrivers is not yet fully implemented." << endl;
-            cerr << "       Some driver counts will not be correct." << endl;
-            warn_count_drivers = false;
+        // First we need to find a branch that is attached to the specified
+        // port. Unfortunately there's no quick way to do this.
+      vvp_island_branch*branch = branches_;
+      unsigned side = 0;
+      while (branch) {
+            if (branch->a->fun == port) {
+                  side = 0;
+                  break;
+            }
+            if (branch->b->fun == port) {
+                  side = 1;
+                  break;
+            }
+            branch = branch->next_branch;
       }
+      assert(branch);
+
+        // Now count the drivers, pushing through the network as necessary.
+      vvp_branch_ptr_t endpoint(branch, side);
+      count_drivers_(endpoint, false, bit_idx, counts);
 }
 
 bool vvp_island_branch_tran::run_test_enabled()
diff --git a/vvp/vvp_island.cc b/vvp/vvp_island.cc
index f799d9809..78358e8e2 100644
--- a/vvp/vvp_island.cc
+++ b/vvp/vvp_island.cc
@@ -226,13 +226,6 @@ vvp_island_branch::~vvp_island_branch()
 {
 }
 
-static vvp_branch_ptr_t next(vvp_branch_ptr_t cur)
-{
-      vvp_island_branch*ptr = cur.ptr();
-      unsigned ab = cur.port();
-      return ptr->link[ab];
-}
-
 void island_collect_node(list<vvp_branch_ptr_t>&conn, vvp_branch_ptr_t cur)
 {
       conn .push_back(cur);
diff --git a/vvp/vvp_island.h b/vvp/vvp_island.h
index 0e20f2c2f..9b7226872 100644
--- a/vvp/vvp_island.h
+++ b/vvp/vvp_island.h
@@ -1,7 +1,7 @@
 #ifndef __vvp_island_H
 #define __vvp_island_H
 /*
- * Copyright (c) 2008-2011 Stephen Williams (steve@icarus.com)
+ * Copyright (c) 2008-2012 Stephen Williams (steve@icarus.com)
  *
  *    This source code is free software; you can redistribute it
  *    and/or modify it in source code form under the terms of the GNU
@@ -182,6 +182,12 @@ inline vvp_vector8_t island_get_value(vvp_net_t*net)
       }
 }
 
+inline vvp_vector8_t island_get_sent_value(vvp_net_t*net)
+{
+      vvp_island_port*fun = dynamic_cast<vvp_island_port*>(net->fun);
+      return fun->outvalue;
+}
+
 extern void island_send_value(vvp_net_t*net, const vvp_vector8_t&val);
 
 /*
@@ -206,6 +212,13 @@ struct vvp_island_branch {
       vvp_net_t*b;
 };
 
+static inline vvp_branch_ptr_t next(vvp_branch_ptr_t cur)
+{
+      vvp_island_branch*ptr = cur.ptr();
+      unsigned ab = cur.port();
+      return ptr->link[ab];
+}
+
 /*
  * This function collects into the conn list all the branch ends
  * that are connected together with the reference branch endpoint