From 6564f5521934ba6d5a0f166e71b6d86011a23fcb Mon Sep 17 00:00:00 2001
From: Stephen Williams <steve@icarus.com>
Date: Sat, 21 May 2022 10:13:27 -0700
Subject: [PATCH] Fix vcd dump of real value parameters

Parameters with real values are possible in Verilog, but not in the VCD
format, so lie a little and call them "real" objects. Otherwise, we can
treat them like constants and it works out, at least for gtkwave.
---
 ivtest/gold/br_gh156.vcd.gold | 14 +++++++++-----
 ivtest/ivltests/br_gh156.v    |  2 ++
 vpi/sys_fst.c                 | 12 +++++++++++-
 vpi/sys_vcd.c                 | 13 ++++++++++++-
 4 files changed, 34 insertions(+), 7 deletions(-)

diff --git a/ivtest/gold/br_gh156.vcd.gold b/ivtest/gold/br_gh156.vcd.gold
index ccac9620e..328241847 100644
--- a/ivtest/gold/br_gh156.vcd.gold
+++ b/ivtest/gold/br_gh156.vcd.gold
@@ -1,5 +1,5 @@
 $date
-	Sun May 15 09:20:23 2022
+	Sat May 21 10:00:47 2022
 $end
 $version
 	Icarus Verilog
@@ -9,17 +9,21 @@ $timescale
 $end
 $scope module main $end
 $var wire 4 ! bat [3:0] $end
-$var parameter 4 " bar $end
-$var parameter 4 # foo $end
+$var real 1 " PI $end
+$var parameter 4 # bar $end
+$var parameter 4 $ foo $end
+$var real 1 % tau $end
 $upscope $end
 $enddefinitions $end
 $comment Show the parameter values. $end
 $dumpall
-b101 #
-b111 "
+b101 $
+b111 #
+r3.14 "
 $end
 #0
 $dumpvars
+r6.28 %
 b1100 !
 $end
 #1
diff --git a/ivtest/ivltests/br_gh156.v b/ivtest/ivltests/br_gh156.v
index 296711232..e31febf92 100644
--- a/ivtest/ivltests/br_gh156.v
+++ b/ivtest/ivltests/br_gh156.v
@@ -5,7 +5,9 @@
 module main;
    parameter [3:0] foo = 4'd5;
    localparam [3:0] bar = 7;
+   parameter real   PI = 3.14;
    wire [3:0] bat = foo + bar;
+   wire real tau = 2.0 * PI;
 
    initial begin
       $dumpfile("work/br_gh156.vcd");
diff --git a/vpi/sys_fst.c b/vpi/sys_fst.c
index ea471a5c4..f01771629 100644
--- a/vpi/sys_fst.c
+++ b/vpi/sys_fst.c
@@ -74,6 +74,10 @@ static void show_this_item(struct vcd_info*info)
 	    value.format = vpiRealVal;
 	    vpi_get_value(info->item, &value);
 	    fstWriterEmitValueChange(dump_file, info->ident, &value.value.real);
+      } else if (type == vpiParameter && vpi_get(vpiConstType, info->item) == vpiRealConst) {
+	    value.format = vpiRealVal;
+	    vpi_get_value(info->item, &value);
+	    fstWriterEmitValueChange(dump_file, info->ident, &value.value.real);
       } else {
 	    value.format = vpiBinStrVal;
 	    vpi_get_value(info->item, &value);
@@ -483,7 +487,13 @@ static void scan_item(unsigned depth, vpiHandle item, int skip)
 	  case vpiNamedEvent: type = FST_VT_VCD_EVENT; break;
 	  case vpiIntVar:
 	  case vpiIntegerVar: type = FST_VT_VCD_INTEGER; break;
-	  case vpiParameter:  type = FST_VT_VCD_PARAMETER; break;
+	    /* FST (gtkwave) assumes PARAMETER are bit, so handle other cases */
+	  case vpiParameter:
+	    switch (vpi_get(vpiConstType, item)) {
+		case vpiRealConst: type = FST_VT_VCD_REAL; break;
+		default: type = FST_VT_VCD_PARAMETER; break;
+	    }
+	    break;
 	    /* Icarus converts realtime to real. */
 	  case vpiRealVar:    type = FST_VT_VCD_REAL; break;
 	  case vpiMemoryWord:
diff --git a/vpi/sys_vcd.c b/vpi/sys_vcd.c
index 0a72e9ea0..13eea5e5d 100644
--- a/vpi/sys_vcd.c
+++ b/vpi/sys_vcd.c
@@ -115,6 +115,11 @@ static void show_this_item(struct vcd_info*info)
 	    fprintf(dump_file, "r%.16g %s\n", value.value.real, info->ident);
       } else if (type == vpiNamedEvent) {
 	    fprintf(dump_file, "1%s\n", info->ident);
+      } else if (type == vpiParameter && vpi_get(vpiConstType, info->item) == vpiRealConst) {
+
+	    value.format = vpiRealVal;
+	    vpi_get_value(info->item, &value);
+	    fprintf(dump_file, "r%.16g %s\n", value.value.real, info->ident);
       } else if (vpi_get(vpiSize, info->item) == 1) {
 	    value.format = vpiBinStrVal;
 	    vpi_get_value(info->item, &value);
@@ -533,7 +538,13 @@ static void scan_item(unsigned depth, vpiHandle item, int skip)
 	  case vpiNamedEvent: type = "event"; break;
 	  case vpiIntVar:
 	  case vpiIntegerVar: type = "integer"; break;
-	  case vpiParameter:  type = "parameter"; break;
+	    /* VCD doesn't support real parameters, so lie. */
+	  case vpiParameter:
+	    switch (vpi_get(vpiConstType, item)) {
+		case vpiRealConst: type = "real"; break;
+		default: type = "parameter"; break;
+	    }
+	    break;
 	    /* Icarus converts realtime to real. */
 	  case vpiRealVar:    type = "real"; break;
 	  case vpiMemoryWord: