From 243cf9416562380282e82bb885b81bb7b7e9132e Mon Sep 17 00:00:00 2001
From: steve <steve>
Date: Thu, 1 Mar 2007 06:19:38 +0000
Subject: [PATCH]  Add support for conditional specify delay paths.

---
 elaborate.cc        | 39 ++++++++++++++++++++++++++++----
 ivl.def             |  4 ++++
 ivl_target.h        | 11 +++++++--
 netlist.cc          | 54 ++++++++++++++++++++++++++++++++++++++++++---
 netlist.h           | 17 ++++++++++++--
 parse.y             |  7 ++++--
 t-dll-api.cc        | 11 ++++++++-
 t-dll.cc            | 21 +++++++++++++-----
 t-dll.h             |  6 ++++-
 tgt-stub/stub.c     |  7 +++++-
 tgt-vvp/vvp_scope.c | 21 ++++++++++++++++--
 vvp/README.txt      |  4 ++--
 vvp/compile.cc      | 28 +++++++++++++++++++----
 vvp/compile.h       |  9 +++++++-
 vvp/delay.cc        | 23 +++++++++++++++----
 vvp/delay.h         | 14 +++++++++++-
 vvp/parse.y         |  7 +++++-
 17 files changed, 247 insertions(+), 36 deletions(-)

diff --git a/elaborate.cc b/elaborate.cc
index f050ce33e..357e3db1c 100644
--- a/elaborate.cc
+++ b/elaborate.cc
@@ -17,7 +17,7 @@
  *    Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
  */
 #ifdef HAVE_CVS_IDENT
-#ident "$Id: elaborate.cc,v 1.359 2007/02/12 01:52:21 steve Exp $"
+#ident "$Id: elaborate.cc,v 1.360 2007/03/01 06:19:38 steve Exp $"
 #endif
 
 # include "config.h"
@@ -2916,7 +2916,7 @@ void PSpecPath::elaborate(Design*des, NetScope*scope) const
 	    return;
 
 	/* Check for various path types that are not supported. */
-
+#if 0
       if (conditional) {
 	    cerr << get_line() << ": sorry: Conditional specify paths"
 		 << " are not supported." << endl;
@@ -2924,6 +2924,14 @@ void PSpecPath::elaborate(Design*des, NetScope*scope) const
 		 << " specify blocks." << endl;
 	    des->errors += 1;
       }
+#endif
+      if (conditional && !condition) {
+	    cerr << get_line() << ": sorry: ifnone specify paths"
+		 << " are not supported." << endl;
+	    cerr << get_line() << ":      : Use -g no-specify to ignore"
+		 << " specify blocks." << endl;
+	    des->errors += 1;
+      }
 
       ivl_assert(*this, conditional || (condition==0));
 
@@ -2981,13 +2989,30 @@ void PSpecPath::elaborate(Design*des, NetScope*scope) const
 	    break;
       }
 
+      NetNet*condit_sig = 0;
+      if (conditional) {
+	    ivl_assert(*this, condition);
+
+	    NetExpr*tmp = elab_and_eval(des, scope, condition, -1);
+	    ivl_assert(*condition, tmp);
+
+	      // FIXME: Look for constant expressions here?
+
+	      // Get a net form.
+	    condit_sig = tmp->synthesize(des);
+	    ivl_assert(*condition, condit_sig);
+      }
+
 	/* Create all the various paths from the path specifier. */
       typedef std::vector<perm_string>::const_iterator str_vector_iter;
       for (str_vector_iter cur = dst.begin()
 		 ; cur != dst.end() ;  cur ++) {
 
 	    if (debug_elaborate) {
-		  cerr << get_line() << ": debug: Path to " << (*cur) << endl;
+		  cerr << get_line() << ": debug: Path to " << (*cur);
+		  if (condit_sig)
+			cerr << " if " << condit_sig->name();
+		  cerr << endl;
 	    }
 
 	    NetNet*dst_sig = scope->find_signal(*cur);
@@ -2999,7 +3024,7 @@ void PSpecPath::elaborate(Design*des, NetScope*scope) const
 	    }
 
 	    NetDelaySrc*path = new NetDelaySrc(scope, scope->local_symbol(),
-					       src.size());
+					       src.size(), condit_sig);
 	    path->set_line(*this);
 
 	    switch (ndelays) {
@@ -3038,6 +3063,9 @@ void PSpecPath::elaborate(Design*des, NetScope*scope) const
 		  idx += 1;
 	    }
 
+	    if (condit_sig)
+		  connect(condit_sig->pin(0), path->pin(idx));
+
 	    dst_sig->add_delay_path(path);
       }
 
@@ -3366,6 +3394,9 @@ Design* elaborate(list<perm_string>roots)
 
 /*
  * $Log: elaborate.cc,v $
+ * Revision 1.360  2007/03/01 06:19:38  steve
+ *  Add support for conditional specify delay paths.
+ *
  * Revision 1.359  2007/02/12 01:52:21  steve
  *  Parse all specify paths to pform.
  *
diff --git a/ivl.def b/ivl.def
index d8f35ee90..9e34244ca 100644
--- a/ivl.def
+++ b/ivl.def
@@ -109,6 +109,10 @@ ivl_nexus_ptr_sig
 ivl_parameter_basename
 ivl_parameter_expr
 
+ivl_path_condit
+ivl_path_delay
+ivl_path_source
+
 ivl_scope_attr_cnt
 ivl_scope_attr_val
 ivl_scope_basename
diff --git a/ivl_target.h b/ivl_target.h
index 7410c4f37..bfe01f1f7 100644
--- a/ivl_target.h
+++ b/ivl_target.h
@@ -19,7 +19,7 @@
  *    Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
  */
 #ifdef HAVE_CVS_IDENT
-#ident "$Id: ivl_target.h,v 1.178 2007/02/26 19:49:49 steve Exp $"
+#ident "$Id: ivl_target.h,v 1.179 2007/03/01 06:19:38 steve Exp $"
 #endif
 
 # include  <inttypes.h>
@@ -387,10 +387,14 @@ typedef const struct ivl_attribute_s*ivl_attribute_t;
  *    This returns the nexus that is the source end of the delay
  *    path. Transitions on the source are the start of the delay time
  *    for this path.
+*
+* ivl_path_condit
+*     This returns the nexus that tracks the condition for the
+*     delay. If the delay path is unconditional, this returns nil.
  */
 extern ivl_nexus_t ivl_path_source(ivl_delaypath_t obj);
 extern uint64_t ivl_path_delay(ivl_delaypath_t obj, ivl_path_edge_t pt);
-
+extern ivl_nexus_t ivl_path_condit(ivl_delaypath_t obj);
 
 /* DESIGN
  * When handed a design (ivl_design_t) there are a few things that you
@@ -1768,6 +1772,9 @@ _END_DECL
 
 /*
  * $Log: ivl_target.h,v $
+ * Revision 1.179  2007/03/01 06:19:38  steve
+ *  Add support for conditional specify delay paths.
+ *
  * Revision 1.178  2007/02/26 19:49:49  steve
  *  Spelling fixes (larry doolittle)
  *
diff --git a/netlist.cc b/netlist.cc
index 97effa90c..7eeaebb3f 100644
--- a/netlist.cc
+++ b/netlist.cc
@@ -17,7 +17,7 @@
  *    Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
  */
 #ifdef HAVE_CVS_IDENT
-#ident "$Id: netlist.cc,v 1.254 2007/02/20 05:58:36 steve Exp $"
+#ident "$Id: netlist.cc,v 1.255 2007/03/01 06:19:38 steve Exp $"
 #endif
 
 # include "config.h"
@@ -237,13 +237,21 @@ NetBus::~NetBus()
 {
 }
 
-NetDelaySrc::NetDelaySrc(NetScope*s, perm_string n, unsigned npins)
-: NetObj(s, n, npins)
+NetDelaySrc::NetDelaySrc(NetScope*s, perm_string n,
+			 unsigned npins, bool condit_src)
+: NetObj(s, n, npins + (condit_src?1:0))
 {
+      condit_flag_ = false;
       for (unsigned idx = 0 ;  idx < npins ;  idx += 1) {
 	    pin(idx).set_name(perm_string::literal("I"), idx);
 	    pin(idx).set_dir(Link::INPUT);
       }
+
+      if (condit_src) {
+	    condit_flag_ = true;
+	    pin(npins).set_name(perm_string::literal("COND"), 0);
+	    pin(npins).set_dir(Link::INPUT);
+      }
 }
 
 NetDelaySrc::~NetDelaySrc()
@@ -330,6 +338,43 @@ uint64_t NetDelaySrc::get_delay(unsigned idx) const
       return transition_delays_[idx];
 }
 
+unsigned NetDelaySrc::src_count() const
+{
+      if (condit_flag_)
+	    return pin_count() - 1;
+      else
+	    return pin_count();
+}
+
+Link& NetDelaySrc::src_pin(unsigned idx)
+{
+      ivl_assert(*this, idx < src_count());
+      return pin(idx);
+}
+
+const Link& NetDelaySrc::src_pin(unsigned idx) const
+{
+      ivl_assert(*this, idx < src_count());
+      return pin(idx);
+}
+
+bool NetDelaySrc::is_condit() const
+{
+      return condit_flag_;
+}
+
+Link& NetDelaySrc::condit_pin()
+{
+      ivl_assert(*this, condit_flag_);
+      return pin(pin_count()-1);
+}
+
+const Link& NetDelaySrc::condit_pin() const
+{
+      ivl_assert(*this, condit_flag_);
+      return pin(pin_count()-1);
+}
+
 NetNet::NetNet(NetScope*s, perm_string n, Type t, unsigned npins)
 : NetObj(s, n, 1), sig_next_(0), sig_prev_(0),
     type_(t), port_type_(NOT_A_PORT), data_type_(IVL_VT_NO_TYPE),
@@ -2220,6 +2265,9 @@ const NetProc*NetTaskDef::proc() const
 
 /*
  * $Log: netlist.cc,v $
+ * Revision 1.255  2007/03/01 06:19:38  steve
+ *  Add support for conditional specify delay paths.
+ *
  * Revision 1.254  2007/02/20 05:58:36  steve
  *  Handle unary minus of real valued expressions.
  *
diff --git a/netlist.h b/netlist.h
index ca018b961..4ad593f87 100644
--- a/netlist.h
+++ b/netlist.h
@@ -19,7 +19,7 @@
  *    Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
  */
 #ifdef HAVE_CVS_IDENT
-#ident "$Id: netlist.h,v 1.369 2007/02/20 05:58:36 steve Exp $"
+#ident "$Id: netlist.h,v 1.370 2007/03/01 06:19:38 steve Exp $"
 #endif
 
 /*
@@ -379,7 +379,8 @@ class NetNode  : public NetObj {
 class NetDelaySrc  : public NetObj {
 
     public:
-      explicit NetDelaySrc(NetScope*s, perm_string n, unsigned npins);
+      explicit NetDelaySrc(NetScope*s, perm_string n,
+			   unsigned nsrc, bool condit_src);
       ~NetDelaySrc();
 
 	// These functions set the delays from the values in the
@@ -401,10 +402,19 @@ class NetDelaySrc  : public NetObj {
 
       uint64_t get_delay(unsigned pe) const;
 
+      unsigned src_count() const;
+      Link&src_pin(unsigned);
+      const Link&src_pin(unsigned) const;
+
+      bool is_condit() const;
+      Link&condit_pin();
+      const Link&condit_pin() const;
+
       void dump(ostream&, unsigned ind) const;
 
     private:
       uint64_t transition_delays_[12];
+      bool condit_flag_;
 
     private: // Not implemented
       NetDelaySrc(const NetDelaySrc&);
@@ -3475,6 +3485,9 @@ extern ostream& operator << (ostream&, NetNet::Type);
 
 /*
  * $Log: netlist.h,v $
+ * Revision 1.370  2007/03/01 06:19:38  steve
+ *  Add support for conditional specify delay paths.
+ *
  * Revision 1.369  2007/02/20 05:58:36  steve
  *  Handle unary minus of real valued expressions.
  *
diff --git a/parse.y b/parse.y
index 1bd801886..83fe00eaf 100644
--- a/parse.y
+++ b/parse.y
@@ -19,7 +19,7 @@
  *    Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
  */
 #ifdef HAVE_CVS_IDENT
-#ident "$Id: parse.y,v 1.228 2007/02/27 06:10:16 steve Exp $"
+#ident "$Id: parse.y,v 1.229 2007/03/01 06:19:39 steve Exp $"
 #endif
 
 # include "config.h"
@@ -2529,7 +2529,10 @@ specify_item
 		}
 	| K_if '(' expression ')' specify_simple_path_decl ';'
                 { PSpecPath*tmp = $5;
-		  if (tmp) tmp->condition = $3;
+		  if (tmp) {
+			tmp->conditional = true;
+			tmp->condition = $3;
+		  }
 		  pform_module_specify_path(tmp);
 		}
 	| K_if '(' expression ')' specify_edge_path_decl ';'
diff --git a/t-dll-api.cc b/t-dll-api.cc
index 183dbaad2..54b5873d1 100644
--- a/t-dll-api.cc
+++ b/t-dll-api.cc
@@ -17,7 +17,7 @@
  *    Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
  */
 #ifdef HAVE_CVS_IDENT
-#ident "$Id: t-dll-api.cc,v 1.140 2007/01/17 05:00:12 steve Exp $"
+#ident "$Id: t-dll-api.cc,v 1.141 2007/03/01 06:19:39 steve Exp $"
 #endif
 
 # include "config.h"
@@ -1242,6 +1242,12 @@ extern "C" ivl_scope_t ivl_parameter_scope(ivl_parameter_t net)
       return net->scope;
 }
 
+extern "C" ivl_nexus_t ivl_path_condit(ivl_delaypath_t obj)
+{
+      assert(obj);
+      return obj->condit;
+}
+
 extern uint64_t ivl_path_delay(ivl_delaypath_t obj, ivl_path_edge_t edg)
 {
       assert(obj);
@@ -1934,6 +1940,9 @@ extern "C" ivl_statement_t ivl_stmt_sub_stmt(ivl_statement_t net)
 
 /*
  * $Log: t-dll-api.cc,v $
+ * Revision 1.141  2007/03/01 06:19:39  steve
+ *  Add support for conditional specify delay paths.
+ *
  * Revision 1.140  2007/01/17 05:00:12  steve
  *  Dead code for memories in scopes.
  *
diff --git a/t-dll.cc b/t-dll.cc
index 63ce0c277..1c5a42028 100644
--- a/t-dll.cc
+++ b/t-dll.cc
@@ -17,7 +17,7 @@
  *    Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
  */
 #ifdef HAVE_CVS_IDENT
-#ident "$Id: t-dll.cc,v 1.164 2007/01/29 01:52:51 steve Exp $"
+#ident "$Id: t-dll.cc,v 1.165 2007/03/01 06:19:39 steve Exp $"
 #endif
 
 # include "config.h"
@@ -2153,7 +2153,7 @@ bool dll_target::signal_paths(const NetNet*net)
          /* Figure out how many paths there really are. */
       for (unsigned idx = 0 ;  idx < net->delay_paths() ;  idx += 1) {
 	    const NetDelaySrc*src = net->delay_path(idx);
-	    obj->npath += src->pin_count();
+	    obj->npath += src->src_count();
       }
 
       obj->path = new struct ivl_delaypath_s[obj->npath];
@@ -2162,8 +2162,15 @@ bool dll_target::signal_paths(const NetNet*net)
       for (unsigned idx = 0 ;  idx < net->delay_paths() ;  idx += 1) {
 	    const NetDelaySrc*src = net->delay_path(idx);
 
-	    for (unsigned pin = 0; pin < src->pin_count(); pin += 1) {
-		  const Nexus*nex = src->pin(pin).nexus();
+	      /* If this path has a condition, then hook it up. */
+	    ivl_nexus_t path_condit = 0;
+	    if (src->is_condit()) {
+		  const Nexus*nt = src->condit_pin().nexus();
+		  path_condit = (ivl_nexus_t) nt->t_cookie();
+	    }
+
+	    for (unsigned pin = 0; pin < src->src_count(); pin += 1) {
+		  const Nexus*nex = src->src_pin(pin).nexus();
 		  if (! nex->t_cookie()) {
 			cerr << src->get_line() << ": internal error: "
 			     << "No signal connected to pin " << pin
@@ -2172,13 +2179,14 @@ bool dll_target::signal_paths(const NetNet*net)
 		  }
 		  assert(nex->t_cookie());
 		  obj->path[ptr].src = (ivl_nexus_t) nex->t_cookie();
-
+		  obj->path[ptr].condit = path_condit;
 		  for (unsigned pe = 0 ;  pe < 12 ;  pe += 1) {
 			obj->path[ptr].delay[pe] = src->get_delay(pe);
 		  }
 
 		  ptr += 1;
 	    }
+
       }
 
       return true;
@@ -2189,6 +2197,9 @@ extern const struct target tgt_dll = { "dll", &dll_target_obj };
 
 /*
  * $Log: t-dll.cc,v $
+ * Revision 1.165  2007/03/01 06:19:39  steve
+ *  Add support for conditional specify delay paths.
+ *
  * Revision 1.164  2007/01/29 01:52:51  steve
  *  Clarify the use of ivl_scope_def for not-functions.
  *
diff --git a/t-dll.h b/t-dll.h
index d811d0ac1..629a86eef 100644
--- a/t-dll.h
+++ b/t-dll.h
@@ -19,7 +19,7 @@
  *    Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
  */
 #ifdef HAVE_CVS_IDENT
-#ident "$Id: t-dll.h,v 1.137 2007/01/17 05:00:12 steve Exp $"
+#ident "$Id: t-dll.h,v 1.138 2007/03/01 06:19:39 steve Exp $"
 #endif
 
 # include  "target.h"
@@ -175,6 +175,7 @@ struct dll_target  : public target_t, public expr_scan_t {
 
 struct ivl_delaypath_s {
       ivl_nexus_t src;
+      ivl_nexus_t condit;
       uint64_t delay[12];
 };
 
@@ -666,6 +667,9 @@ struct ivl_statement_s {
 
 /*
  * $Log: t-dll.h,v $
+ * Revision 1.138  2007/03/01 06:19:39  steve
+ *  Add support for conditional specify delay paths.
+ *
  * Revision 1.137  2007/01/17 05:00:12  steve
  *  Dead code for memories in scopes.
  *
diff --git a/tgt-stub/stub.c b/tgt-stub/stub.c
index 7fdcff493..f1fa0d9dd 100644
--- a/tgt-stub/stub.c
+++ b/tgt-stub/stub.c
@@ -17,7 +17,7 @@
  *    Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
  */
 #ifdef HAVE_CVS_IDENT
-#ident "$Id: stub.c,v 1.145 2007/01/29 01:52:51 steve Exp $"
+#ident "$Id: stub.c,v 1.146 2007/03/01 06:19:39 steve Exp $"
 #endif
 
 /*
@@ -1130,8 +1130,10 @@ static void show_signal(ivl_signal_t net)
       for (idx = 0 ;  idx < ivl_signal_npath(net) ;  idx += 1) {
 	    ivl_delaypath_t path = ivl_signal_path(net,idx);
 	    ivl_nexus_t nex = ivl_path_source(path);
+	    ivl_nexus_t con = ivl_path_condit(path);
 
 	    fprintf(out, "      path %s", ivl_nexus_name(nex));
+	    if (con) fprintf(out, " (if %s)", ivl_nexus_name(con));
 	    fprintf(out, " %" PRIu64 ",%" PRIu64 ",%" PRIu64
 		         " %" PRIu64 ",%" PRIu64 ",%" PRIu64
 		         " %" PRIu64 ",%" PRIu64 ",%" PRIu64
@@ -1485,6 +1487,9 @@ int target_design(ivl_design_t des)
 
 /*
  * $Log: stub.c,v $
+ * Revision 1.146  2007/03/01 06:19:39  steve
+ *  Add support for conditional specify delay paths.
+ *
  * Revision 1.145  2007/01/29 01:52:51  steve
  *  Clarify the use of ivl_scope_def for not-functions.
  *
diff --git a/tgt-vvp/vvp_scope.c b/tgt-vvp/vvp_scope.c
index 546a3f534..ab7d4c69a 100644
--- a/tgt-vvp/vvp_scope.c
+++ b/tgt-vvp/vvp_scope.c
@@ -17,7 +17,7 @@
  *    Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
  */
 #ifdef HAVE_CVS_IDENT
-#ident "$Id: vvp_scope.c,v 1.153 2007/02/26 19:49:50 steve Exp $"
+#ident "$Id: vvp_scope.c,v 1.154 2007/03/01 06:19:39 steve Exp $"
 #endif
 
 # include  "vvp_priv.h"
@@ -674,12 +674,19 @@ static void draw_modpath(const char*label, const char*driver,
       unsigned idx;
       typedef const char*ccharp;
       ccharp*src_drivers;
+      ccharp*con_drivers;
 
       src_drivers = calloc(ivl_signal_npath(path_sig), sizeof(ccharp));
+      con_drivers = calloc(ivl_signal_npath(path_sig), sizeof(ccharp));
       for (idx = 0 ;  idx < ivl_signal_npath(path_sig) ;  idx += 1) {
 	    ivl_delaypath_t path = ivl_signal_path(path_sig, idx);
 	    ivl_nexus_t src = ivl_path_source(path);
+	    ivl_nexus_t con = ivl_path_condit(path);
+
 	    src_drivers[idx] = draw_net_input(src);
+
+	    if (con) con_drivers[idx] = draw_net_input(con);
+	    else con_drivers[idx] = 0;
       }
 
       fprintf(vvp_out, "%s .modpath %s", label, driver);
@@ -691,7 +698,7 @@ static void draw_modpath(const char*label, const char*driver,
 		    " (%"PRIu64",%"PRIu64",%"PRIu64
 		    ", %"PRIu64",%"PRIu64",%"PRIu64
 		    ", %"PRIu64",%"PRIu64",%"PRIu64
-		    ", %"PRIu64",%"PRIu64",%"PRIu64")",
+		    ", %"PRIu64",%"PRIu64",%"PRIu64,
 		    ivl_path_delay(path, IVL_PE_01),
 		    ivl_path_delay(path, IVL_PE_10),
 		    ivl_path_delay(path, IVL_PE_0z),
@@ -704,11 +711,18 @@ static void draw_modpath(const char*label, const char*driver,
 		    ivl_path_delay(path, IVL_PE_x0),
 		    ivl_path_delay(path, IVL_PE_xz),
 		    ivl_path_delay(path, IVL_PE_zx));
+
+	    if (con_drivers[idx]) {
+		  fprintf(vvp_out, " ? %s", con_drivers[idx]);
+	    }
+
+	    fprintf(vvp_out, ")");
       }
 
       fprintf(vvp_out, ";\n");
 
       free(src_drivers);
+      free(con_drivers);
 }
 
 /*
@@ -2352,6 +2366,9 @@ int draw_scope(ivl_scope_t net, ivl_scope_t parent)
 
 /*
  * $Log: vvp_scope.c,v $
+ * Revision 1.154  2007/03/01 06:19:39  steve
+ *  Add support for conditional specify delay paths.
+ *
  * Revision 1.153  2007/02/26 19:49:50  steve
  *  Spelling fixes (larry doolittle)
  *
diff --git a/vvp/README.txt b/vvp/README.txt
index d872ad80d..1a81edc1f 100644
--- a/vvp/README.txt
+++ b/vvp/README.txt
@@ -1,7 +1,7 @@
 /*
  * Copyright (c) 2001 Stephen Williams (steve@icarus.com)
  *
- *  $Id: README.txt,v 1.80 2007/01/16 05:44:16 steve Exp $
+ *  $Id: README.txt,v 1.81 2007/03/01 06:19:39 steve Exp $
  */
 
 VVP SIMULATION ENGINE
@@ -368,7 +368,7 @@ A module path delay takes data from its input, then a list of module
 path delays. The <src> for each possible delay set is a trigger that
 activates the delay.
 
-        .modpath <input> , [ <src> (<delays>) ] ;
+        .modpath <input> , [ <src> (<delays> [? <condition>]) ] ;
 
 ARRAY INDEX STATEMENTS:
 
diff --git a/vvp/compile.cc b/vvp/compile.cc
index ef4b91f55..93eb7d793 100644
--- a/vvp/compile.cc
+++ b/vvp/compile.cc
@@ -17,7 +17,7 @@
  *    Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
  */
 #ifdef HAVE_CVS_IDENT
-#ident "$Id: compile.cc,v 1.228 2007/02/14 05:58:14 steve Exp $"
+#ident "$Id: compile.cc,v 1.229 2007/03/01 06:19:39 steve Exp $"
 #endif
 
 # include  "arith.h"
@@ -1099,9 +1099,9 @@ vvp_fun_modpath* compile_modpath(char*label, struct symb_s src)
       return obj;
 }
 
-void compile_modpath_src(vvp_fun_modpath*dst,
-			 struct symb_s src,
-			 struct numbv_s vals)
+static vvp_net_t*make_modpath_src(vvp_fun_modpath*dst,
+					    struct symb_s src,
+					    struct numbv_s vals)
 {
       vvp_time64_t use_delay[12];
 
@@ -1120,6 +1120,23 @@ void compile_modpath_src(vvp_fun_modpath*dst,
       input_connect(net, 0, src.text);
 
       dst->add_modpath_src(obj);
+      return net;
+}
+
+void compile_modpath_src(vvp_fun_modpath*dst,
+			 struct symb_s src,
+			 struct numbv_s vals)
+{
+      make_modpath_src(dst, src, vals);
+}
+
+void compile_modpath_src(vvp_fun_modpath*dst,
+			 struct symb_s src,
+			 struct numbv_s vals,
+			 struct symb_s condit_src)
+{
+      vvp_net_t*net = make_modpath_src(dst, src, vals);
+      input_connect(net, 1, condit_src.text);
 }
 
 /*
@@ -1580,6 +1597,9 @@ void compile_param_string(char*label, char*name, char*value)
 
 /*
  * $Log: compile.cc,v $
+ * Revision 1.229  2007/03/01 06:19:39  steve
+ *  Add support for conditional specify delay paths.
+ *
  * Revision 1.228  2007/02/14 05:58:14  steve
  *  Add the mov/wr opcode.
  *
diff --git a/vvp/compile.h b/vvp/compile.h
index 7f2da0183..827b31986 100644
--- a/vvp/compile.h
+++ b/vvp/compile.h
@@ -19,7 +19,7 @@
  *    Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
  */
 #ifdef HAVE_CVS_IDENT
-#ident "$Id: compile.h,v 1.85 2007/01/16 05:44:16 steve Exp $"
+#ident "$Id: compile.h,v 1.86 2007/03/01 06:19:39 steve Exp $"
 #endif
 
 # include  <stdio.h>
@@ -166,6 +166,10 @@ extern vvp_fun_modpath* compile_modpath(char*label, struct symb_s src);
 extern void compile_modpath_src(vvp_fun_modpath*dst,
 				struct symb_s input,
 				struct numbv_s d);
+extern void compile_modpath_src(vvp_fun_modpath*dst,
+				struct symb_s input,
+				struct numbv_s d,
+				struct symb_s condit_input);
 
 extern void compile_reduce_and(char*label, struct symb_s arg);
 extern void compile_reduce_or(char*label, struct symb_s arg);
@@ -362,6 +366,9 @@ extern void compile_alias_real(char*label, char*name,
 
 /*
  * $Log: compile.h,v $
+ * Revision 1.86  2007/03/01 06:19:39  steve
+ *  Add support for conditional specify delay paths.
+ *
  * Revision 1.85  2007/01/16 05:44:16  steve
  *  Major rework of array handling. Memories are replaced with the
  *  more general concept of arrays. The NetMemory and NetEMemory
diff --git a/vvp/delay.cc b/vvp/delay.cc
index 447d0dca5..401c4bf76 100644
--- a/vvp/delay.cc
+++ b/vvp/delay.cc
@@ -17,7 +17,7 @@
  *    Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
  */
 #ifdef HAVE_CVS_IDENT
-#ident "$Id: delay.cc,v 1.16 2007/01/26 05:15:41 steve Exp $"
+#ident "$Id: delay.cc,v 1.17 2007/03/01 06:19:39 steve Exp $"
 #endif
 
 #include "delay.h"
@@ -375,6 +375,10 @@ void vvp_fun_modpath::recv_vec4(vvp_net_ptr_t port, const vvp_vector4_t&bit)
 	/* Select a time delay source that applies. */
       vvp_fun_modpath_src*src = 0;
       for (vvp_fun_modpath_src*cur = src_list_ ;  cur ;  cur=cur->next_) {
+	      /* Skip paths that are disabled by conditions. */
+	    if (cur->condition_flag_ == false)
+		  continue;
+
 	    if (src == 0) {
 		  src = cur;
 	    } else if (cur->wake_time_ > src->wake_time_) {
@@ -425,6 +429,7 @@ vvp_fun_modpath_src::vvp_fun_modpath_src(vvp_time64_t del[12])
 
       next_ = 0;
       wake_time_ = 0;
+      condition_flag_ = true;
 }
 
 vvp_fun_modpath_src::~vvp_fun_modpath_src()
@@ -433,14 +438,24 @@ vvp_fun_modpath_src::~vvp_fun_modpath_src()
 
 void vvp_fun_modpath_src::recv_vec4(vvp_net_ptr_t port, const vvp_vector4_t&bit)
 {
-      if (port.port() != 0)
-	    return;
+      if (port.port() == 0) {
+	      // The modpath input...
+	    wake_time_ = schedule_simtime();
 
-      wake_time_ = schedule_simtime();
+      } else if (port.port() == 1) {
+	      // The modpath condition input...
+	    if (bit.value(0) == BIT4_1)
+		  condition_flag_ = true;
+	    else
+		  condition_flag_ = false;
+      }
 }
 
 /*
  * $Log: delay.cc,v $
+ * Revision 1.17  2007/03/01 06:19:39  steve
+ *  Add support for conditional specify delay paths.
+ *
  * Revision 1.16  2007/01/26 05:15:41  steve
  *  More literal implementation of inertial delay model.
  *
diff --git a/vvp/delay.h b/vvp/delay.h
index c3202664a..5875f066e 100644
--- a/vvp/delay.h
+++ b/vvp/delay.h
@@ -19,7 +19,7 @@
  *    Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
  */
 #ifdef HAVE_CVS_IDENT
-#ident "$Id: delay.h,v 1.13 2007/01/26 05:15:41 steve Exp $"
+#ident "$Id: delay.h,v 1.14 2007/03/01 06:19:39 steve Exp $"
 #endif
 
 /*
@@ -138,6 +138,14 @@ class vvp_fun_delay  : public vvp_net_fun_t, private vvp_gen_event_s {
       void clean_pulse_events_(vvp_time64_t use_delay);
 };
 
+/*
+* These objects inplement module delay paths. The fun_modpath functor
+* is the output of the modpath, and the vvp_fun_modpath_src is the
+* source of the modpath. The modpath source tracks events on the
+* inputs to enable delays, and the vvp_fun_modpath, when it's time to
+* schedule, looks at the associated modpath_src objects for which
+* paths are active.
+*/
 class vvp_fun_modpath;
 class vvp_fun_modpath_src;
 
@@ -185,6 +193,7 @@ class vvp_fun_modpath_src  : public vvp_net_fun_t {
       vvp_fun_modpath_src*next_;
 
       vvp_time64_t wake_time_;
+      bool condition_flag_;
 
     private:
       vvp_fun_modpath_src(const vvp_fun_modpath_src&);
@@ -193,6 +202,9 @@ class vvp_fun_modpath_src  : public vvp_net_fun_t {
 
 /*
  * $Log: delay.h,v $
+ * Revision 1.14  2007/03/01 06:19:39  steve
+ *  Add support for conditional specify delay paths.
+ *
  * Revision 1.13  2007/01/26 05:15:41  steve
  *  More literal implementation of inertial delay model.
  *
diff --git a/vvp/parse.y b/vvp/parse.y
index e72bd9142..5d5bafa22 100644
--- a/vvp/parse.y
+++ b/vvp/parse.y
@@ -19,7 +19,7 @@
  *    Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
  */
 #ifdef HAVE_CVS_IDENT
-#ident "$Id: parse.y,v 1.87 2007/01/16 05:44:16 steve Exp $"
+#ident "$Id: parse.y,v 1.88 2007/03/01 06:19:39 steve Exp $"
 #endif
 
 # include  "parse_misc.h"
@@ -746,6 +746,8 @@ modpath_src_list
 modpath_src
         : symbol '(' numbers ')'
                 { compile_modpath_src(modpath_dst, $1, $3); }
+        | symbol '(' numbers '?' symbol ')'
+                { compile_modpath_src(modpath_dst, $1, $3, $5); }
         ;
 
 udp_table
@@ -803,6 +805,9 @@ int compile_design(const char*path)
 
 /*
  * $Log: parse.y,v $
+ * Revision 1.88  2007/03/01 06:19:39  steve
+ *  Add support for conditional specify delay paths.
+ *
  * Revision 1.87  2007/01/16 05:44:16  steve
  *  Major rework of array handling. Memories are replaced with the
  *  more general concept of arrays. The NetMemory and NetEMemory