Merge pull request #1065 from steveicarus/vvp-undriven-net-initialisation

vvp undriven net initialisation

Author: steveicarus

ivtest/vpi/br_gh1041.c

@@ -0,0 +1,52 @@
+#include <vpi_user.h>
+
+static PLI_INT32 start_cb(struct t_cb_data *cb)
+{
+    static struct t_vpi_value val;
+    vpiHandle wire;
+
+    (void)cb;  // suppress unused parameter warning
+
+    wire = vpi_handle_by_name("test.w4", NULL);
+    if (wire) {
+        val.format = vpiIntVal;
+        val.value.integer = 1;
+        vpi_put_value(wire, &val, NULL, vpiNoDelay);
+    } else {
+        vpi_printf("Failed to get handle for w4\n");
+    }
+
+    wire = vpi_handle_by_name("test.w8", NULL);
+    if (wire) {
+        val.format = vpiIntVal;
+        val.value.integer = 1;
+        vpi_put_value(wire, &val, NULL, vpiNoDelay);
+    } else {
+        vpi_printf("Failed to get handle for w8\n");
+    }
+
+    wire = vpi_handle_by_name("test.wr", NULL);
+    if (wire) {
+        val.format = vpiRealVal;
+        val.value.real = 1.0;
+        vpi_put_value(wire, &val, NULL, vpiNoDelay);
+    } else {
+        vpi_printf("Failed to get handle for wr\n");
+    }
+
+    return 0;
+}
+
+static void register_cb(void)
+{
+    struct t_cb_data         cbd = {};
+
+    cbd.reason = cbStartOfSimulation;
+    cbd.cb_rtn = start_cb;
+    vpi_register_cb(&cbd);
+}
+
+void (*vlog_startup_routines[])(void) = {
+    register_cb,
+    0
+};

ivtest/vpi/br_gh1041.v

@@ -0,0 +1,20 @@
+module test;
+  wire w4;
+  tri0 w8;
+  wire real wr;
+
+  reg failed = 0;
+
+  initial begin
+    #0;
+    $display("w4 %b w8 %b wr %f", w4, w8, wr);
+    if (w4 !== 1'b1) failed = 1;
+    if (w8 !== 1'b1) failed = 1;
+    if (wr != 1.0)   failed = 1;
+
+    if (failed)
+      $display("FAILED");
+    else
+      $display("PASSED");
+  end
+endmodule

ivtest/vpi/br_gh1041b.c

@@ -0,0 +1,74 @@
+#include <vpi_user.h>
+
+static void step(void);
+
+static vpiHandle w;
+
+static PLI_INT32 tick_cb(struct t_cb_data *cb)
+{
+    static struct t_vpi_value val = { .format = vpiIntVal };
+    static int                idx;
+
+    (void)cb;
+
+    ++idx;
+    val.value.integer = idx & 1;
+    vpi_put_value(w, &val, NULL, vpiNoDelay);
+    step();
+    return 0;
+}
+
+/* Request a callback after a delay. */
+
+static void step(void)
+{
+    static struct t_vpi_time now = { .type = vpiSimTime, .low = 2 };
+    static struct t_cb_data  cbd =
+        { .reason = cbAfterDelay, .cb_rtn = tick_cb, .time = &now };
+
+    /* Callback after delay. */
+
+    vpi_register_cb(&cbd);
+}
+
+/* Callback function - simulation is starting. */
+
+static PLI_INT32 start_cb(struct t_cb_data *cb)
+{
+    static struct t_vpi_value val = { .format = vpiIntVal };
+
+    (void)cb;
+
+    w = vpi_handle_by_name("test.w", NULL);
+    if (!w)
+        vpi_printf("No handle!\n");
+    vpi_printf("Got handle for %s\n", vpi_get_str(vpiFullName, w));
+    val.value.integer = 0;
+    vpi_put_value(w, &val, NULL, vpiNoDelay);
+    step();
+    return 0;
+}
+
+/* VPI initialisation. */
+
+static void start(void)
+{
+    static struct t_vpi_time now = { .type = vpiSimTime };
+    static struct t_cb_data  cbd = { .reason = cbStartOfSimulation,
+                                     .time = &now, .cb_rtn = start_cb };
+
+    /* At this point VPI objects do not exist,
+     * so request a callback once they do.
+     */
+
+    vpi_register_cb(&cbd);
+}
+
+/* This is a table of registration functions. This table is the external
+ * symbol that the VVP simulator looks for when loading this .vpi module.
+ */
+
+void (*vlog_startup_routines[])(void) = {
+      start,
+      0
+};

ivtest/vpi/br_gh1041b.v

@@ -0,0 +1,18 @@
+module test(w);
+   input wire w;
+   wire a, b;
+
+   
+   initial begin
+      #11 $finish;
+   end
+
+   assign b = 0;
+   
+   assign a = !w | b;
+   
+   always @(a) begin
+      $display($time, ": Wire a is now ", a);
+   end
+endmodule
+   

ivtest/vpi_gold/br_gh1041.gold

@@ -0,0 +1,4 @@
+Compiling vpi/br_gh1041.c...
+Making br_gh1041.vpi from  br_gh1041.o...
+w4 1 w8 1 wr 1.000000
+PASSED

ivtest/vpi_gold/br_gh1041b.gold

@@ -0,0 +1,10 @@
+Compiling vpi/br_gh1041b.c...
+Making br_gh1041b.vpi from  br_gh1041b.o...
+Got handle for test.w
+                   0: Wire a is now 1
+                   2: Wire a is now 0
+                   4: Wire a is now 1
+                   6: Wire a is now 0
+                   8: Wire a is now 1
+                  10: Wire a is now 0
+vpi/br_gh1041b.v:7: $finish called at 11 (1s)

ivtest/vpi_regress.list

@@ -71,6 +71,8 @@ br_gh308		normal			br_gh308.c		br_gh308.gold
 br_gh317		normal			br_gh317.c		br_gh317.gold
 br_gh496		normal,-g2009		br_gh496.c		br_gh496.gold
 br_gh1037		normal,-g2009		br_gh1037.c		br_gh1037.gold
+br_gh1041		normal			br_gh1041.c		br_gh1041.gold
+br_gh1041b		normal			br_gh1041b.c		br_gh1041b.gold
 br_ml20191013		normal			br_ml20191013.c		br_ml20191013.gold
 by_index		normal			by_index.c		by_index.gold
 by_name			normal			by_name.c		by_name.log

tgt-vvp/draw_net_input.c

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2001-2022 Stephen Williams ([email protected])
+ * Copyright (c) 2001-2024 Stephen Williams ([email protected])
  *
  *    This source code is free software; you can redistribute it
  *    and/or modify it in source code form under the terms of the GNU
@@ -651,18 +651,20 @@ static void draw_net_input_x(ivl_nexus_t nex,
       nex_data->flags |= nex_flags;
 
 	/* If the nexus has no drivers, then send a constant HiZ or
-	   0.0 into the net. */
+	   0.0 into the net. Use a lower case 'c' prefix for the
+	   constant to inform vvp that this is an undriven value. */
       if (ndrivers == 0) {
 	    unsigned wid = width_of_nexus(nex);
 	    int pull = (res == IVL_SIT_TRI0) || (res == IVL_SIT_TRI1);
 	      /* For real nets put 0.0. */
 	    if (signal_data_type_of_nexus(nex) == IVL_VT_REAL) {
 		  nex_private = draw_Cr_to_string(0.0);
+		  nex_private[0] = 'c';
 	    } else {
 		  unsigned jdx;
 		  char*tmp = malloc((pull ? 3 : 1) * wid + 5);
 		  nex_private = tmp;
-		  strcpy(tmp, pull ? "C8<" : "C4<");
+		  strcpy(tmp, pull ? "c8<" : "c4<");
 		  tmp += strlen(tmp);
 		  switch (res) {
 		      case IVL_SIT_TRI:

vvp/compile.cc

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2001-2021 Stephen Williams ([email protected])
+ * Copyright (c) 2001-2024 Stephen Williams ([email protected])
  *
  *    This source code is free software; you can redistribute it
  *    and/or modify it in source code form under the terms of the GNU
@@ -891,9 +891,20 @@ void compile_vpi_time_precision(long pre)
  *
  * The real value is sign * (mant ** exp).
  */
+static bool crstring_header_test(const char*str)
+{
+      if ((str[0] != 'C') && (str[0] != 'c'))
+	    return false;
+      if ((str[1] != 'r') || (str[2] != '<'))
+	    return false;
+
+      return true;
+}
+
 bool crstring_test(const char*str)
 {
-      if (strncmp(str, "Cr<", 3) != 0) return false;
+      if (!crstring_header_test(str))
+	    return false;
       const char*tp = strchr(str, '>');
       if (tp == 0) return false;
       if (tp[1] != 0) return false;
@@ -906,6 +917,8 @@ bool crstring_test(const char*str)
 
 double crstring_to_double(const char*label)
 {
+      assert(crstring_header_test(label));
+
       const char*cp = label+3;
       assert(*cp == 'm');
       cp += 1;
@@ -956,14 +969,21 @@ void input_connect(vvp_net_t*fdx, unsigned port, char*label)
 
 	    vvp_vector4_t tmp = c4string_to_vector4(label);
 
-	      // Inputs that are constants are schedule to execute as
+	      // Inputs that are constants are scheduled to execute as
 	      // soon at the simulation starts. In Verilog, constants
 	      // start propagating when the simulation starts, just
 	      // like any other signal value. But letting the
 	      // scheduler distribute the constant value has the
 	      // additional advantage that the constant is not
 	      // propagated until the network is fully linked.
-	    schedule_set_vector(ifdx, tmp);
+	      // For constants that initialise an undriven net, we
+	      // schedule execution before time 0, to make sure it
+	      // occurs before any sensitive processes are started
+	      // or VPI callbacks are executed.
+	    if (label[0] == 'c')
+		  schedule_init_vector(ifdx, tmp);
+	    else
+		  schedule_set_vector(ifdx, tmp);
 
 	    free(label);
 	    return;
@@ -973,7 +993,10 @@ void input_connect(vvp_net_t*fdx, unsigned port, char*label)
       if (c8string_test(label)) {
 
 	    vvp_vector8_t tmp = c8string_to_vector8(label);
-	    schedule_set_vector(ifdx, tmp);
+	    if (label[0] == 'c')
+		  schedule_init_vector(ifdx, tmp);
+	    else
+		  schedule_set_vector(ifdx, tmp);
 
 	    free(label);
 	    return;
@@ -985,7 +1008,10 @@ void input_connect(vvp_net_t*fdx, unsigned port, char*label)
 
 	    double tmp = crstring_to_double(label);
 
-	    schedule_set_vector(ifdx, tmp);
+	    if (label[0] == 'c')
+		  schedule_init_vector(ifdx, tmp);
+	    else
+		  schedule_set_vector(ifdx, tmp);
 	    free(label);
 	    return;
       }

vvp/lexor.lex

@@ -4,7 +4,7 @@
 
 %{
 /*
- * Copyright (c) 2001-2018 Stephen Williams ([email protected])
+ * Copyright (c) 2001-2024 Stephen Williams ([email protected])
  *
  *    This source code is free software; you can redistribute it
  *    and/or modify it in source code form under the terms of the GNU
@@ -263,17 +263,17 @@ static char* strdupnew(char const *str)
 
   /* Handle some specialized constant/literals as symbols. */
 
-"C4<"[01xz]*">" {
+[Cc]"4<"[01xz]*">" {
       yylval.text = strdup(yytext);
       assert(yylval.text);
       return T_SYMBOL; }
 
-"C8<"[01234567xz]*">" {
+[Cc]"8<"[01234567xz]*">" {
       yylval.text = strdup(yytext);
       assert(yylval.text);
       return T_SYMBOL; }
 
-"Cr<m"[a-f0-9]*"g"[a-f0-9]*">" {
+[Cc]"r<m"[a-f0-9]*"g"[a-f0-9]*">" {
       yylval.text = strdup(yytext);
       assert(yylval.text);
       return T_SYMBOL; }