From f2d7a18756088f4167b91c5ec4735bb694f36567 Mon Sep 17 00:00:00 2001
From: whitequark <whitequark@whitequark.org>
Date: Mon, 8 Jun 2020 17:29:08 +0000
Subject: cxxrtl: emit debug information for constant wires.

Constant wires can represent a significant chunk of the design in
generic designs or after optimization. Emitting them in VCD files
significantly improves usability because gtkwave removes all traces
that are not present in the VCD file after reload, and iterative
development suffers if switching a varying signal to a constant
disrupts the workflow.
---
 backends/cxxrtl/cxxrtl.h | 11 +++++++++++
 1 file changed, 11 insertions(+)

(limited to 'backends/cxxrtl/cxxrtl.h')

diff --git a/backends/cxxrtl/cxxrtl.h b/backends/cxxrtl/cxxrtl.h
index 5f74899fd..30f4667c5 100644
--- a/backends/cxxrtl/cxxrtl.h
+++ b/backends/cxxrtl/cxxrtl.h
@@ -741,6 +741,17 @@ struct debug_item : ::cxxrtl_object {
 		next  = item.data;
 	}
 
+	template<size_t Bits>
+	debug_item(const value<Bits> &item) {
+		static_assert(sizeof(item) == value<Bits>::chunks * sizeof(chunk_t),
+		              "value<Bits> is not compatible with C layout");
+		type  = VALUE;
+		width = Bits;
+		depth = 1;
+		curr  = const_cast<uint32_t*>(item.data);
+		next  = nullptr;
+	}
+
 	template<size_t Bits>
 	debug_item(wire<Bits> &item) {
 		static_assert(sizeof(item.curr) == value<Bits>::chunks * sizeof(chunk_t) &&
-- 
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