cxxrtl: treat internal wires used only for debug as constants.

Fixes #2739 (again).

diff --git a/backends/cxxrtl/cxxrtl_backend.cc b/backends/cxxrtl/cxxrtl_backend.cc
index 7ff344e66edceb67be0efd8197075fc148623281..56305258a4a62f054d8d61064d7f0179e154320a 100644 (file)
--- a/backends/cxxrtl/cxxrtl_backend.cc
+++ b/backends/cxxrtl/cxxrtl_backend.cc
@@ -2881,6 +2881,12 @@ struct CxxrtlWorker {
                                                debug_live_nodes.erase(node);
                                        } else if (wire_type.is_local()) {
                                                debug_wire_type = {WireType::LOCAL}; // wire not inlinable
+                                       } else if (wire_type.type == WireType::UNUSED) {
+                                               if (wire_init.count(wire)) {
+                                                       debug_wire_type = {WireType::CONST, wire_init.at(wire)};
+                                               } else {
+                                                       debug_wire_type = {WireType::CONST, RTLIL::SigSpec(RTLIL::S0, wire->width)};
+                                               } // wire never modified
                                        } else {
                                                log_assert(wire_type.is_member());
                                                debug_wire_type = wire_type; // wire is a member