Merge pull request #4379 from QuantamHD/fix_verific

frontend: Fixes verific import around range order

frontends/verific/verific.cc

@@ -2156,8 +2156,16 @@ void VerificImporter::import_netlist(RTLIL::Design *design, Netlist *nl, std::ma
 			int port_offset = 0;
 			if (pr->GetPort()->Bus()) {
 				port_name = pr->GetPort()->Bus()->Name();
-				port_offset = pr->GetPort()->Bus()->IndexOf(pr->GetPort()) -
-						min(pr->GetPort()->Bus()->LeftIndex(), pr->GetPort()->Bus()->RightIndex());
+				int msb_index = pr->GetPort()->Bus()->LeftIndex();
+				int lsb_index = pr->GetPort()->Bus()->RightIndex();
+				int index_of_port = pr->GetPort()->Bus()->IndexOf(pr->GetPort());
+				port_offset =  index_of_port - min(msb_index, lsb_index);
+				// In cases where the msb order is flipped we need to make sure
+				// that the indicies match LSB = 0 order to match the std::vector
+				// to SigSpec LSB = 0 precondition.
+				if (lsb_index > msb_index) {
+					port_offset = abs(port_offset - (lsb_index - min(msb_index, lsb_index)));
+				}
 			}
 			IdString port_name_id = RTLIL::escape_id(port_name);
 			auto &sigvec = cell_port_conns[port_name_id];