diff --git a/tgt-vvp/eval_expr.c b/tgt-vvp/eval_expr.c
index b3a9f3b99..46b916fbb 100644
--- a/tgt-vvp/eval_expr.c
+++ b/tgt-vvp/eval_expr.c
@@ -17,7 +17,7 @@
  *    Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
  */
 #ifdef HAVE_CVS_IDENT
-#ident "$Id: eval_expr.c,v 1.70 2002/08/22 03:38:40 steve Exp $"
+#ident "$Id: eval_expr.c,v 1.71 2002/08/27 05:39:57 steve Exp $"
 #endif
 
 # include  "vvp_priv.h"
@@ -1123,6 +1123,7 @@ void draw_memory_index_expr(ivl_memory_t mem, ivl_expr_t ae)
 		unsigned nbits = ivl_expr_width(ae);
 		const char*bits = ivl_expr_bits(ae);
 		unsigned long v = 0;
+		int unknown_flag = 0;
 		unsigned idx;
 		for (idx = 0 ;  idx < nbits ;  idx += 1) 
 		      switch (bits[idx]) {
@@ -1134,14 +1135,18 @@ void draw_memory_index_expr(ivl_memory_t mem, ivl_expr_t ae)
 			    break;
 			  default:
 			    v = ~0UL;
+			    unknown_flag = 1;
 			    break;
 		      }
 		fprintf(vvp_out, "    %%ix/load 3, %lu;\n", (v-root)*width);
+		fprintf(vvp_out, "    %%mov 4, %c, 1;\n",
+			unknown_flag?'1':'0');
 		break;
 	  }
 	  case IVL_EX_ULONG: {
 		unsigned v = ivl_expr_uvalue(ae); 
 		fprintf(vvp_out, "    %%ix/load 3, %u;\n", (v-root)*width);
+		fprintf(vvp_out, "    %%mov 4, 0, 1;\n");
 		break;
 	  }
 	  default: {
@@ -1745,6 +1750,13 @@ struct vector_info draw_eval_expr(ivl_expr_t exp)
 
 /*
  * $Log: eval_expr.c,v $
+ * Revision 1.71  2002/08/27 05:39:57  steve
+ *  Fix l-value indexing of memories and vectors so that
+ *  an unknown (x) index causes so cell to be addresses.
+ *
+ *  Fix tangling of label identifiers in the fork-join
+ *  code generator.
+ *
  * Revision 1.70  2002/08/22 03:38:40  steve
  *  Fix behavioral eval of x?a:b expressions.
  *
diff --git a/tgt-vvp/vvp_priv.h b/tgt-vvp/vvp_priv.h
index afb415a4e..c067d51a6 100644
--- a/tgt-vvp/vvp_priv.h
+++ b/tgt-vvp/vvp_priv.h
@@ -19,7 +19,7 @@
  *    Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
  */
 #ifdef HAVE_CVS_IDENT
-#ident "$Id: vvp_priv.h,v 1.18 2002/08/12 01:35:04 steve Exp $"
+#ident "$Id: vvp_priv.h,v 1.19 2002/08/27 05:39:57 steve Exp $"
 #endif
 
 # include  "ivl_target.h"
@@ -91,6 +91,13 @@ struct vector_info {
 
 extern struct vector_info draw_eval_expr(ivl_expr_t exp);
 extern struct vector_info draw_eval_expr_wid(ivl_expr_t exp, unsigned w);
+
+/*
+ * This function draws code to evaluate the index expression exp for
+ * the memory mem. The result is loaded into index register i3, and
+ * the flag bit 4 is set to 0 if the numerical value is defined, or 1
+ * if not.
+ */
 extern void draw_memory_index_expr(ivl_memory_t mem, ivl_expr_t exp);
 
 extern unsigned short allocate_vector(unsigned short wid);
@@ -108,6 +115,13 @@ extern unsigned thread_count;
 
 /*
  * $Log: vvp_priv.h,v $
+ * Revision 1.19  2002/08/27 05:39:57  steve
+ *  Fix l-value indexing of memories and vectors so that
+ *  an unknown (x) index causes so cell to be addresses.
+ *
+ *  Fix tangling of label identifiers in the fork-join
+ *  code generator.
+ *
  * Revision 1.18  2002/08/12 01:35:04  steve
  *  conditional ident string using autoconfig.
  *
diff --git a/tgt-vvp/vvp_process.c b/tgt-vvp/vvp_process.c
index efcb30245..98e70a25c 100644
--- a/tgt-vvp/vvp_process.c
+++ b/tgt-vvp/vvp_process.c
@@ -17,7 +17,7 @@
  *    Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
  */
 #ifdef HAVE_CVS_IDENT
-#ident "$Id: vvp_process.c,v 1.64 2002/08/19 00:06:12 steve Exp $"
+#ident "$Id: vvp_process.c,v 1.65 2002/08/27 05:39:57 steve Exp $"
 #endif
 
 # include  "vvp_priv.h"
@@ -125,6 +125,10 @@ static void assign_to_memory(ivl_memory_t mem, unsigned idx,
 	      vvp_memory_label(mem), delay, bit);
 }
 
+/*
+ * This function, in addition to setting the value into index 0, sets
+ * bit 4 to 1 if the value is unknown.
+ */
 static void calculate_into_x0(ivl_expr_t expr)
 {
       struct vector_info vec = draw_eval_expr(expr);
@@ -156,39 +160,58 @@ static int show_stmt_assign(ivl_statement_t net)
 	    unsigned cur_rbit = 0;
 
 	    for (lidx = 0 ;  lidx < ivl_stmt_lvals(net) ;  lidx += 1) {
+		  unsigned skip_set = transient_id++;
+		  unsigned skip_set_flag = 0;
 		  unsigned idx;
 		  unsigned bit_limit = wid - cur_rbit;
 		  lval = ivl_stmt_lval(net, lidx);
 
 		    /* If there is a mux for the lval, calculate the
 		       value and write it into index0. */
-		  if (ivl_lval_mux(lval))
+		  if (ivl_lval_mux(lval)) {
 			calculate_into_x0(ivl_lval_mux(lval));
+			fprintf(vvp_out, "    %%jmp/1 t_%u, 4;\n", skip_set);
+			skip_set_flag = 1;
+		  }
 
 		  mem = ivl_lval_mem(lval);
-		  if (mem) 
+		  if (mem) {
 			draw_memory_index_expr(mem, ivl_lval_idx(lval));
+			fprintf(vvp_out, "    %%jmp/1 t_%u, 4;\n", skip_set);
+			skip_set_flag = 1;
+		  }
 
 		  if (bit_limit > ivl_lval_pins(lval))
 			bit_limit = ivl_lval_pins(lval);
 
-		  for (idx = 0 ;  idx < bit_limit ;  idx += 1) {
-			if (mem)
+		  if (mem) {
+			for (idx = 0 ;  idx < bit_limit ;  idx += 1) {
 			      set_to_memory(mem, idx,
 					    bitchar_to_idx(bits[cur_rbit]));
-			else
+
+			      cur_rbit += 1;
+			}
+
+			for (idx = bit_limit
+				   ; idx < ivl_lval_pins(lval) ; idx += 1)
+			      set_to_memory(mem, idx, 0);
+
+
+		  } else {
+			for (idx = 0 ;  idx < bit_limit ;  idx += 1) {
 			      set_to_lvariable(lval, idx,
 					       bitchar_to_idx(bits[cur_rbit]));
 
-			cur_rbit += 1;
+			      cur_rbit += 1;
+			}
+
+			for (idx = bit_limit
+				   ; idx < ivl_lval_pins(lval) ; idx += 1)
+			      set_to_lvariable(lval, idx, 0);
 		  }
 
-		  for (idx = bit_limit ; idx < ivl_lval_pins(lval) ; idx += 1)
-			if (mem)
-			      set_to_memory(mem, idx, 0);
-			else
-			      set_to_lvariable(lval, idx, 0);
-
+		  if (skip_set_flag)
+			fprintf(vvp_out, "t_%u ;\n", skip_set);
 	    }
 
 	    return 0;
@@ -200,18 +223,26 @@ static int show_stmt_assign(ivl_statement_t net)
 	unsigned cur_rbit = 0;
 
 	for (lidx = 0 ;  lidx < ivl_stmt_lvals(net) ;  lidx += 1) {
+	      unsigned skip_set = transient_id++;
+	      unsigned skip_set_flag = 0;
 	      unsigned idx;
 	      unsigned bit_limit = wid - cur_rbit;
 	      lval = ivl_stmt_lval(net, lidx);
 
 		/* If there is a mux for the lval, calculate the
 		   value and write it into index0. */
-	      if (ivl_lval_mux(lval))
+	      if (ivl_lval_mux(lval)) {
 		    calculate_into_x0(ivl_lval_mux(lval));
+		    fprintf(vvp_out, "    %%jmp/1 t_%u, 4;\n", skip_set);
+		    skip_set_flag = 1;
+	      }
 
 	      mem = ivl_lval_mem(lval);
-	      if (mem) 
+	      if (mem) {
 		    draw_memory_index_expr(mem, ivl_lval_idx(lval));
+		    fprintf(vvp_out, "    %%jmp/1 t_%u, 4;\n", skip_set);
+		    skip_set_flag = 1;
+	      }
 
 	      if (bit_limit > ivl_lval_pins(lval))
 		    bit_limit = ivl_lval_pins(lval);
@@ -234,6 +265,9 @@ static int show_stmt_assign(ivl_statement_t net)
 		    else
 			  set_to_lvariable(lval, idx, 0);
 
+	      if (skip_set_flag)
+		    fprintf(vvp_out, "t_%u ;\n", skip_set);
+
 	}
 
 	clr_vector(res);
@@ -715,13 +749,16 @@ static int show_stmt_fork(ivl_statement_t net, ivl_scope_t sscope)
       unsigned cnt = ivl_stmt_block_count(net);
 
       unsigned out = transient_id++;
+      unsigned id_base = transient_id;
+      transient_id += cnt-1;
+
 
 	/* Draw a fork statement for all but one of the threads of the
 	   fork/join. Send the threads off to a bit of code where they
 	   are implemented. */
       for (idx = 0 ;  idx < cnt-1 ;  idx += 1) {
 	    fprintf(vvp_out, "    %%fork t_%u, S_%s;\n",
-		    transient_id+idx, 
+		    id_base+idx, 
 		    vvp_mangle_id(ivl_scope_name(sscope)));
       }
 
@@ -735,7 +772,7 @@ static int show_stmt_fork(ivl_statement_t net, ivl_scope_t sscope)
       fprintf(vvp_out, "    %%jmp t_%u;\n", out);
 
       for (idx = 0 ;  idx < cnt-1 ;  idx += 1) {
-	    fprintf(vvp_out, "t_%u ;\n", transient_id+idx);
+	    fprintf(vvp_out, "t_%u ;\n", id_base+idx);
 	    rc += show_statement(ivl_stmt_block_stmt(net, idx), sscope);
 	    fprintf(vvp_out, "    %%end;\n");
       }
@@ -744,8 +781,6 @@ static int show_stmt_fork(ivl_statement_t net, ivl_scope_t sscope)
 	   the implementations of all the child threads. */
       fprintf(vvp_out, "t_%u ;\n", out);
 
-      transient_id += cnt-1;
-
       return rc;
 }
 
@@ -1232,6 +1267,13 @@ int draw_func_definition(ivl_scope_t scope)
 
 /*
  * $Log: vvp_process.c,v $
+ * Revision 1.65  2002/08/27 05:39:57  steve
+ *  Fix l-value indexing of memories and vectors so that
+ *  an unknown (x) index causes so cell to be addresses.
+ *
+ *  Fix tangling of label identifiers in the fork-join
+ *  code generator.
+ *
  * Revision 1.64  2002/08/19 00:06:12  steve
  *  Allow release to handle removal of target net.
  *
diff --git a/vvp/opcodes.txt b/vvp/opcodes.txt
index c21751b5d..81fe55232 100644
--- a/vvp/opcodes.txt
+++ b/vvp/opcodes.txt
@@ -1,7 +1,7 @@
 /*
  * Copyright (c) 2001 Stephen Williams (steve@icarus.com)
  *
- *  $Id: opcodes.txt,v 1.37 2002/08/22 03:38:40 steve Exp $
+ *  $Id: opcodes.txt,v 1.38 2002/08/27 05:39:57 steve Exp $
  */
 
 
@@ -234,7 +234,16 @@ thread bit space, and <wid> is the width of the vector.
 
 The function converts the 4-value bits into a binary number, without
 sign extension. If any of the bits of the vector is x or z, then the
-index register gets the value (-1).
+index register gets the value 0.
+
+The function also writes into bit 4 a 1 if any of the bits of the
+input vector are x or z. This is a flag that the 0 value written into
+the index register is really the result of calculating from unknown
+bits.
+
+	4: unknown value
+	5: (reserved)
+	6: (reserved)
 
 
 * %ix/load <idx>, <value>
diff --git a/vvp/vthread.cc b/vvp/vthread.cc
index 11fc9c17a..54e97a271 100644
--- a/vvp/vthread.cc
+++ b/vvp/vthread.cc
@@ -17,7 +17,7 @@
  *    Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
  */
 #ifdef HAVE_CVS_IDENT
-#ident "$Id: vthread.cc,v 1.81 2002/08/22 03:38:40 steve Exp $"
+#ident "$Id: vthread.cc,v 1.82 2002/08/27 05:39:57 steve Exp $"
 #endif
 
 # include  "vthread.h"
@@ -1260,21 +1260,26 @@ bool of_IX_LOAD(vthread_t thr, vvp_code_t cp)
  * vector and <wid> is the width in bits.
  *
  * Index registers only hold binary values, so if any of the
- * bits of the vector are x or z, then set the value to 0
- * and give up.
+ * bits of the vector are x or z, then set the value to 0,
+ * set bit[4] to 1, and give up.
  */
 bool of_IX_GET(vthread_t thr, vvp_code_t cp)
 {
       unsigned long v = 0;
+      bool unknown_flag = false;
+
       for (unsigned i = 0; i<cp->number; i++) {
 	    unsigned char vv = thr_get_bit(thr, cp->bit_idx[1] + i);
 	    if (vv&2) {
 		  v = 0UL;
+		  unknown_flag = true;
 		  break;
 	    }
 	    v |= vv << i;
       }
       thr->index[cp->bit_idx[0] & 3] = v;
+	/* Set bit 4 as a flag if the input is unknown. */
+      thr_put_bit(thr, 4, unknown_flag? 1 : 0);
       return true;
 }
 
@@ -2243,6 +2248,13 @@ bool of_CALL_UFUNC(vthread_t thr, vvp_code_t cp)
 
 /*
  * $Log: vthread.cc,v $
+ * Revision 1.82  2002/08/27 05:39:57  steve
+ *  Fix l-value indexing of memories and vectors so that
+ *  an unknown (x) index causes so cell to be addresses.
+ *
+ *  Fix tangling of label identifiers in the fork-join
+ *  code generator.
+ *
  * Revision 1.81  2002/08/22 03:38:40  steve
  *  Fix behavioral eval of x?a:b expressions.
  *