Merge pull request #674 from rubund/feature/svinterface_at_top

Support for SystemVerilog interfaces as ports in the top level module + test case

frontends/ast/ast.cc

@@ -904,7 +904,7 @@ RTLIL::Const AstNode::realAsConst(int width)
 }
 
 // create a new AstModule from an AST_MODULE AST node
-static AstModule* process_module(AstNode *ast, bool defer)
+static AstModule* process_module(AstNode *ast, bool defer, AstNode *original_ast = NULL)
 {
 	log_assert(ast->type == AST_MODULE || ast->type == AST_INTERFACE);
 
@@ -920,7 +920,11 @@ static AstModule* process_module(AstNode *ast, bool defer)
 	current_module->set_bool_attribute("\\cells_not_processed");
 
 	current_ast_mod = ast;
-	AstNode *ast_before_simplify = ast->clone();
+	AstNode *ast_before_simplify;
+	if (original_ast != NULL)
+		ast_before_simplify = original_ast;
+	else
+		ast_before_simplify = ast->clone();
 
 	if (flag_dump_ast1) {
 		log("Dumping Verilog AST before simplification:\n");
@@ -1087,6 +1091,84 @@ AstModule::~AstModule()
 		delete ast;
 }
 
+
+// An interface port with modport is specified like this:
+//    <interface_name>.<modport_name>
+// This function splits the interface_name from the modport_name, and fails if it is not a valid combination
+std::pair<std::string,std::string> AST::split_modport_from_type(std::string name_type)
+{
+	std::string interface_type = "";
+	std::string interface_modport = "";
+	size_t ndots = std::count(name_type.begin(), name_type.end(), '.');
+	// Separate the interface instance name from any modports:
+	if (ndots == 0) { // Does not have modport
+		interface_type = name_type;
+	}
+	else {
+		std::stringstream name_type_stream(name_type);
+		std::string segment;
+		std::vector<std::string> seglist;
+		while(std::getline(name_type_stream, segment, '.')) {
+			seglist.push_back(segment);
+		}
+		if (ndots == 1) { // Has modport
+			interface_type = seglist[0];
+			interface_modport = seglist[1];
+		}
+		else { // Erroneous port type
+			log_error("More than two '.' in signal port type (%s)\n", name_type.c_str());
+		}
+	}
+	return std::pair<std::string,std::string>(interface_type, interface_modport);
+
+}
+
+AstNode * AST::find_modport(AstNode *intf, std::string name)
+{
+	for (auto &ch : intf->children)
+		if (ch->type == AST_MODPORT)
+			if (ch->str == name) // Modport found
+				return ch;
+	return NULL;
+}
+
+// Iterate over all wires in an interface and add them as wires in the AST module:
+void AST::explode_interface_port(AstNode *module_ast, RTLIL::Module * intfmodule, std::string intfname, AstNode *modport)
+{
+	for (auto &wire_it : intfmodule->wires_){
+		AstNode *wire = new AstNode(AST_WIRE, new AstNode(AST_RANGE, AstNode::mkconst_int(wire_it.second->width -1, true), AstNode::mkconst_int(0, true)));
+		std::string origname = log_id(wire_it.first);
+		std::string newname = intfname + "." + origname;
+		wire->str = newname;
+		if (modport != NULL) {
+			bool found_in_modport = false;
+			// Search for the current wire in the wire list for the current modport
+			for (auto &ch : modport->children) {
+				if (ch->type == AST_MODPORTMEMBER) {
+					std::string compare_name = "\\" + origname;
+					if (ch->str == compare_name) { // Found signal. The modport decides whether it is input or output
+						found_in_modport = true;
+						wire->is_input = ch->is_input;
+						wire->is_output = ch->is_output;
+						break;
+					}
+				}
+			}
+			if (found_in_modport) {
+				module_ast->children.push_back(wire);
+			}
+			else { // If not found in modport, do not create port
+				delete wire;
+			}
+		}
+		else { // If no modport, set inout
+			wire->is_input = true;
+			wire->is_output = true;
+			module_ast->children.push_back(wire);
+		}
+	}
+}
+
 // When an interface instance is found in a module, the whole RTLIL for the module will be rederived again
 // from AST. The interface members are copied into the AST module with the prefix of the interface.
 void AstModule::reprocess_module(RTLIL::Design *design, dict<RTLIL::IdString, RTLIL::Module*> local_interfaces)
@@ -1105,6 +1187,49 @@ void AstModule::reprocess_module(RTLIL::Design *design, dict<RTLIL::IdString, RT
 		}
 	}
 
+	AstNode *ast_before_replacing_interface_ports = new_ast->clone();
+
+	// Explode all interface ports. Note this will only have an effect on 'top
+	// level' modules. Other sub-modules will have their interface ports
+	// exploded via the derive(..) function
+	for (size_t i =0; i<new_ast->children.size(); i++)
+	{
+		AstNode *ch2 = new_ast->children[i];
+		if (ch2->type == AST_INTERFACEPORT) { // Is an interface port
+			std::string name_port = ch2->str; // Name of the interface port
+			if (ch2->children.size() > 0) {
+				for(size_t j=0; j<ch2->children.size();j++) {
+					AstNode *ch = ch2->children[j];
+					if(ch->type == AST_INTERFACEPORTTYPE) { // Found the AST node containing the type of the interface
+						std::pair<std::string,std::string> res = split_modport_from_type(ch->str);
+						std::string interface_type = res.first;
+						std::string interface_modport = res.second; // Is "", if no modport
+						if (design->modules_.count(interface_type) > 0) {
+							// Add a cell to the module corresponding to the interface port such that
+							// it can further propagated down if needed:
+							AstNode *celltype_for_intf = new AstNode(AST_CELLTYPE);
+							celltype_for_intf->str = interface_type;
+							AstNode *cell_for_intf = new AstNode(AST_CELL, celltype_for_intf);
+							cell_for_intf->str = name_port + "_inst_from_top_dummy";
+							new_ast->children.push_back(cell_for_intf);
+
+							// Get all members of this non-overridden dummy interface instance:
+							RTLIL::Module *intfmodule = design->modules_[interface_type]; // All interfaces should at this point in time (assuming
+							                                                              // reprocess_module is called from the hierarchy pass) be
+							                                                              // present in design->modules_
+							AstModule *ast_module_of_interface = (AstModule*)intfmodule;
+							std::string interface_modport_compare_str = "\\" + interface_modport;
+							AstNode *modport = find_modport(ast_module_of_interface->ast, interface_modport_compare_str); // modport == NULL if no modport
+							// Iterate over all wires in the interface and add them to the module:
+							explode_interface_port(new_ast, intfmodule, name_port, modport);
+						}
+						break;
+					}
+				}
+			}
+		}
+	}
+
 	// The old module will be deleted. Rename and mark for deletion:
 	std::string original_name = this->name.str();
 	std::string changed_name = original_name + "_before_replacing_local_interfaces";
@@ -1119,7 +1244,8 @@ void AstModule::reprocess_module(RTLIL::Design *design, dict<RTLIL::IdString, RT
 	}
 
 	// Generate RTLIL from AST for the new module and add to the design:
-	AstModule *newmod = process_module(new_ast, false);
+	AstModule *newmod = process_module(new_ast, false, ast_before_replacing_interface_ports);
+	delete(new_ast);
 	design->add(newmod);
 	RTLIL::Module* mod = design->module(original_name);
 	if (is_top)
@@ -1164,47 +1290,10 @@ RTLIL::IdString AstModule::derive(RTLIL::Design *design, dict<RTLIL::IdString, R
 				std::string interface_modport = modports.at(intfname).str();
 				AstModule *ast_module_of_interface = (AstModule*)intfmodule;
 				AstNode *ast_node_of_interface = ast_module_of_interface->ast;
-				for (auto &ch : ast_node_of_interface->children) {
+				modport = find_modport(ast_node_of_interface, interface_modport);
-					if (ch->type == AST_MODPORT) {
-						if (ch->str == interface_modport) { // Modport found
-							modport = ch;
-						}
-					}
-				}
 			}
 			// Iterate over all wires in the interface and add them to the module:
-			for (auto &wire_it : intfmodule->wires_){
+			explode_interface_port(new_ast, intfmodule, intfname, modport);
-				AstNode *wire = new AstNode(AST_WIRE, new AstNode(AST_RANGE, AstNode::mkconst_int(wire_it.second->width -1, true), AstNode::mkconst_int(0, true)));
-				std::string origname = log_id(wire_it.first);
-				std::string newname = intfname + "." + origname;
-				wire->str = newname;
-				if (modport != NULL) {
-					bool found_in_modport = false;
-					// Search for the current wire in the wire list for the current modport
-					for (auto &ch : modport->children) {
-						if (ch->type == AST_MODPORTMEMBER) {
-							std::string compare_name = "\\" + origname;
-							if (ch->str == compare_name) { // Found signal. The modport decides whether it is input or output
-								found_in_modport = true;
-								wire->is_input = ch->is_input;
-								wire->is_output = ch->is_output;
-								break;
-							}
-						}
-					}
-					if (found_in_modport) {
-						new_ast->children.push_back(wire);
-					}
-					else { // If not found in modport, do not create port
-						delete wire;
-					}
-				}
-				else { // If no modport, set inout
-					wire->is_input = true;
-					wire->is_output = true;
-					new_ast->children.push_back(wire);
-				}
-			}
 		}
 
 		design->add(process_module(new_ast, false));

frontends/ast/ast.h

@@ -308,6 +308,11 @@ namespace AST
 
 	// call a DPI function
 	AstNode *dpi_call(const std::string &rtype, const std::string &fname, const std::vector<std::string> &argtypes, const std::vector<AstNode*> &args);
+
+	// Helper functions related to handling SystemVerilog interfaces
+	std::pair<std::string,std::string> split_modport_from_type(std::string name_type);
+	AstNode * find_modport(AstNode *intf, std::string name);
+	void explode_interface_port(AstNode *module_ast, RTLIL::Module * intfmodule, std::string intfname, AstNode *modport);
 }
 
 namespace AST_INTERNAL

frontends/ast/genrtlil.cc

@@ -870,27 +870,10 @@ RTLIL::SigSpec AstNode::genRTLIL(int width_hint, bool sign_hint)
 		if (children.size() > 0) {
 			for(size_t i=0; i<children.size();i++) {
 				if(children[i]->type == AST_INTERFACEPORTTYPE) {
-					std::string name_type = children[i]->str;
+					std::pair<std::string,std::string> res = AST::split_modport_from_type(children[i]->str);
-					size_t ndots = std::count(name_type.begin(), name_type.end(), '.');
+					wire->attributes["\\interface_type"] = res.first;
-					// Separate the interface instance name from any modports:
+					if (res.second != "")
-					if (ndots == 0) { // Does not have modport
+						wire->attributes["\\interface_modport"] = res.second;
-						wire->attributes["\\interface_type"] = name_type;
-					}
-					else {
-						std::stringstream name_type_stream(name_type);
-						std::string segment;
-						std::vector<std::string> seglist;
-						while(std::getline(name_type_stream, segment, '.')) {
-							seglist.push_back(segment);
-						}
-						if (ndots == 1) { // Has modport
-							wire->attributes["\\interface_type"] = seglist[0];
-							wire->attributes["\\interface_modport"] = seglist[1];
-						}
-						else { // Erroneous port type
-							log_error("More than two '.' in signal port type (%s)\n", name_type.c_str());
-						}
-					}
 					break;
 				}
 			}

passes/hierarchy/hierarchy.cc

@@ -146,6 +146,17 @@ bool expand_module(RTLIL::Design *design, RTLIL::Module *module, bool flag_check
 	std::map<RTLIL::Cell*, std::pair<int, int>> array_cells;
 	std::string filename;
 
+	bool has_interface_ports = false;
+
+	// If any of the ports are actually interface ports, we will always need to
+	// reprocess the module:
+	if(!module->get_bool_attribute("\\interfaces_replaced_in_module")) {
+		for (auto &wire : module->wires_) {
+			if ((wire.second->port_input || wire.second->port_output) && wire.second->get_bool_attribute("\\is_interface"))
+				has_interface_ports = true;
+		}
+	}
+
 	// Always keep track of all derived interfaces available in the current module in 'interfaces_in_module':
 	dict<RTLIL::IdString, RTLIL::Module*> interfaces_in_module;
 	for (auto &cell_it : module->cells_)
@@ -244,8 +255,17 @@ bool expand_module(RTLIL::Design *design, RTLIL::Module *module, bool flag_check
 					RTLIL::IdString interface_name = interface_name_str;
 					bool not_found_interface = false;
 					if(module->get_bool_attribute("\\interfaces_replaced_in_module")) { // If 'interfaces' in the cell have not be been handled yet, there is no need to derive the sub-module either
-						if (interfaces_in_module.count(interface_name) > 0) { // Check if the interface instance is present in module
+						// Check if the interface instance is present in module:
-							RTLIL::Module *mod_replace_ports = interfaces_in_module.at(interface_name);
+						// Interface instances may either have the plain name or the name appended with '_inst_from_top_dummy'.
+						// Check for both of them here
+						int nexactmatch = interfaces_in_module.count(interface_name) > 0;
+						std::string interface_name_str2 =  interface_name_str + "_inst_from_top_dummy";
+						RTLIL::IdString interface_name2 = interface_name_str2;
+						int nmatch2 = interfaces_in_module.count(interface_name2) > 0;
+						if (nexactmatch > 0 || nmatch2 > 0) {
+							if (nexactmatch != 0) // Choose the one with the plain name if it exists
+								interface_name2 = interface_name;
+							RTLIL::Module *mod_replace_ports = interfaces_in_module.at(interface_name2);
 							for (auto &mod_wire : mod_replace_ports->wires_) { // Go over all wires in interface, and add replacements to lists.
 								std::string signal_name1 = conn.first.str() + "." + log_id(mod_wire.first);
 								std::string signal_name2 = interface_name.str() + "." + log_id(mod_wire.first);
@@ -259,7 +279,7 @@ bool expand_module(RTLIL::Design *design, RTLIL::Module *module, bool flag_check
 								}
 							}
 							connections_to_remove.push_back(conn.first);
-							interfaces_to_add_to_submodule[conn.first] = interfaces_in_module.at(interface_name);
+							interfaces_to_add_to_submodule[conn.first] = interfaces_in_module.at(interface_name2);
 
 							// Add modports to a dict which will be passed to AstModule::derive
 							if (interface_modport != "") {
@@ -363,8 +383,8 @@ bool expand_module(RTLIL::Design *design, RTLIL::Module *module, bool flag_check
 	module->attributes.erase("\\cells_not_processed");
 
 
-	// If any interface instances were found in the module, we need to rederive it completely:
+	// If any interface instances or interface ports were found in the module, we need to rederive it completely:
-	if (interfaces_in_module.size() > 0 && !module->get_bool_attribute("\\interfaces_replaced_in_module")) {
+	if ((interfaces_in_module.size() > 0 || has_interface_ports) && !module->get_bool_attribute("\\interfaces_replaced_in_module")) {
 		module->reprocess_module(design, interfaces_in_module);
 		return did_something;
 	}
@@ -438,6 +458,20 @@ void hierarchy_clean(RTLIL::Design *design, RTLIL::Module *top, bool purge_lib)
 	for (auto &it : design->modules_)
 		if (used.count(it.second) == 0)
 			del_modules.push_back(it.second);
+		else {
+			// Now all interface ports must have been exploded, and it is hence
+			// safe to delete all of the remaining dummy interface ports:
+			pool<RTLIL::Wire*> del_wires;
+			for(auto &wire : it.second->wires_) {
+				if ((wire.second->port_input || wire.second->port_output) && wire.second->get_bool_attribute("\\is_interface")) {
+					del_wires.insert(wire.second);
+				}
+			}
+			if (del_wires.size() > 0) {
+				it.second->remove(del_wires);
+				it.second->fixup_ports();
+			}
+		}
 
 	int del_counter = 0;
 	for (auto mod : del_modules) {

tests/svinterfaces/run-test.sh

@@ -3,3 +3,4 @@
 
 
 ./runone.sh  svinterface1
+./runone.sh  svinterface_at_top

tests/svinterfaces/runone.sh

@@ -22,11 +22,14 @@ iverilog -g2012 ${TESTNAME}_syn.v
 iverilog -g2012 ${TESTNAME}_ref_syn.v
 
 set +e
-
 iverilog -g2012 ${TESTNAME}_tb.v ${TESTNAME}_ref_syn.v
 ./a.out
 mv output.txt reference_result.txt
-iverilog -g2012 ${TESTNAME}_tb.v ${TESTNAME}_syn.v
+if [ -f ${TESTNAME}_wrapper.v ] ; then
+    iverilog -g2012 ${TESTNAME}_tb_wrapper.v ${TESTNAME}_syn.v
+else
+    iverilog -g2012 ${TESTNAME}_tb.v ${TESTNAME}_syn.v
+fi
 ./a.out
 mv output.txt dut_result.txt
 

tests/svinterfaces/svinterface_at_top.sv

@@ -0,0 +1,125 @@
+
+
+module TopModule(
+    input logic clk,
+    input logic rst,
+    output logic [21:0] outOther,
+    input logic [1:0] sig,
+    input logic flip,
+    output logic [1:0] sig_out,
+    MyInterface.submodule1 interfaceInstanceAtTop,
+    output logic [15:0] passThrough);
+
+  MyInterface #(.WIDTH(4)) MyInterfaceInstance();
+
+  SubModule1 u_SubModule1 (
+    .clk(clk),
+    .rst(rst),
+    .u_MyInterface(MyInterfaceInstance),
+    .u_MyInterfaceFromTop(interfaceInstanceAtTop),
+    .outOther(outOther),
+    .sig (sig)
+  );
+
+  assign sig_out = MyInterfaceInstance.mysig_out;
+
+
+  assign MyInterfaceInstance.setting = flip;
+
+  assign passThrough = MyInterfaceInstance.passThrough;
+
+endmodule
+
+interface MyInterface #(
+  parameter WIDTH = 3)(
+  );
+
+  logic setting;
+  logic [WIDTH-1:0] other_setting;
+
+  logic [1:0] mysig_out;
+
+  logic [15:0] passThrough;
+
+    modport submodule1 (
+        input  setting,
+        output other_setting,
+        output mysig_out,
+        output passThrough
+    );
+
+    modport submodule2 (
+        input  setting,
+        output other_setting,
+        input  mysig_out,
+        output passThrough
+    );
+
+endinterface
+
+
+module SubModule1(
+    input logic clk,
+    input logic rst,
+    MyInterface.submodule1 u_MyInterface,
+    MyInterface.submodule1 u_MyInterfaceFromTop,
+    input logic [1:0] sig,
+    output logic [21:0] outOther
+
+  );
+
+
+  always_ff @(posedge clk or posedge rst)
+    if(rst)
+      u_MyInterface.mysig_out <= 0;
+    else begin
+      if(u_MyInterface.setting)
+        u_MyInterface.mysig_out <= sig;
+      else
+        u_MyInterface.mysig_out <= ~sig;
+    end
+
+  MyInterface #(.WIDTH(22)) MyInterfaceInstanceInSub();
+
+  SubModule2 u_SubModule2 (
+    .clk(clk),
+    .rst(rst),
+    .u_MyInterfaceFromTopDown(u_MyInterfaceFromTop),
+    .u_MyInterfaceInSub2(u_MyInterface),
+    .u_MyInterfaceInSub3(MyInterfaceInstanceInSub)
+  );
+
+    assign outOther = MyInterfaceInstanceInSub.other_setting;
+
+    assign MyInterfaceInstanceInSub.setting = 0;
+    assign MyInterfaceInstanceInSub.mysig_out = sig;
+
+endmodule
+
+module SubModule2(
+
+    input logic clk,
+    input logic rst,
+    MyInterface.submodule2 u_MyInterfaceInSub2,
+    MyInterface.submodule1 u_MyInterfaceFromTopDown,
+    MyInterface.submodule2 u_MyInterfaceInSub3
+
+  );
+
+  assign u_MyInterfaceFromTopDown.mysig_out = u_MyInterfaceFromTop.setting ? 10 :  20;
+
+   always_comb begin
+      if (u_MyInterfaceInSub3.mysig_out == 2'b00)
+        u_MyInterfaceInSub3.other_setting[21:0] = 1000;
+      else if (u_MyInterfaceInSub3.mysig_out == 2'b01)
+        u_MyInterfaceInSub3.other_setting[21:0] = 2000;
+      else if (u_MyInterfaceInSub3.mysig_out == 2'b10)
+        u_MyInterfaceInSub3.other_setting[21:0] = 3000;
+      else
+        u_MyInterfaceInSub3.other_setting[21:0] = 4000;
+   end
+
+    assign u_MyInterfaceInSub2.passThrough[7:0] = 124;
+    assign u_MyInterfaceInSub2.passThrough[15:8] = 200;
+
+endmodule

tests/svinterfaces/svinterface_at_top_ref.v

@@ -0,0 +1,120 @@
+
+module TopModule(
+    input logic clk,
+    input logic rst,
+    input logic [1:0] sig,
+    input logic flip,
+    output logic [15:0] passThrough,
+    output logic [21:0] outOther,
+    input logic interfaceInstanceAtTop_setting,
+    output logic [2:0] interfaceInstanceAtTop_other_setting,
+    output logic [1:0] interfaceInstanceAtTop_mysig_out,
+    output logic [15:0] interfaceInstanceAtTop_passThrough,
+    output logic [1:0] sig_out);
+
+
+    logic MyInterfaceInstance_setting;
+    logic [3:0] MyInterfaceInstance_other_setting;
+    logic [1:0] MyInterfaceInstance_mysig_out;
+
+  SubModule1 u_SubModule1 (
+    .clk(clk),
+    .rst(rst),
+    .u_MyInterface_setting(MyInterfaceInstance_setting),
+    .u_MyInterface_mysig_out(MyInterfaceInstance_mysig_out),
+    .u_MyInterface_other_setting(MyInterfaceInstance_other_setting),
+    .u_MyInterfaceFromTop_setting(interfaceInstanceAtTop_setting),
+    .u_MyInterfaceFromTop_other_setting(interfaceInstanceAtTop_other_setting),
+    .u_MyInterfaceFromTop_mysig_out(interfaceInstanceAtTop_mysig_out),
+    .u_MyInterfaceFromTop_passThrough(interfaceInstanceAtTop_passThrough),
+    .outOther(outOther),
+    .passThrough (passThrough),
+    .sig (sig)
+  );
+
+  assign sig_out = MyInterfaceInstance_mysig_out;
+
+
+  assign MyInterfaceInstance_setting = flip;
+
+endmodule
+
+
+module SubModule1(
+    input logic clk,
+    input logic rst,
+    input logic u_MyInterface_setting,
+    output logic [3:0] u_MyInterface_other_setting,
+    output logic [1:0] u_MyInterface_mysig_out,
+    output logic [21:0] outOther,
+    input logic [1:0] sig,
+    input logic u_MyInterfaceFromTop_setting,
+    output logic [2:0]  u_MyInterfaceFromTop_other_setting,
+    output logic [1:0]  u_MyInterfaceFromTop_mysig_out,
+    output logic [14:0] u_MyInterfaceFromTop_passThrough,
+    output logic [15:0] passThrough
+  );
+
+  always @(posedge clk or posedge rst)
+    if(rst)
+      u_MyInterface_mysig_out <= 0;
+    else begin
+      if(u_MyInterface_setting)
+        u_MyInterface_mysig_out <= sig;
+      else
+        u_MyInterface_mysig_out <= ~sig;
+    end
+
+    logic MyInterfaceInstanceInSub_setting;
+    logic [21:0] MyInterfaceInstanceInSub_other_setting;
+    logic [1:0] MyInterfaceInstanceInSub_mysig_out;
+
+  assign u_MyInterfaceFromTop_mysig_out = u_MyInterfaceFromTop_setting ? 10 :  20;
+
+  SubModule2 u_SubModule2 (
+    .clk(clk),
+    .rst(rst),
+    .u_MyInterfaceInSub2_setting(u_MyInterface_setting),
+    .u_MyInterfaceInSub2_mysig_out(u_MyInterface_mysig_out),
+    .u_MyInterfaceInSub2_other_setting(u_MyInterface_other_setting),
+    .u_MyInterfaceInSub3_setting(MyInterfaceInstanceInSub_setting),
+    .u_MyInterfaceInSub3_mysig_out(MyInterfaceInstanceInSub_mysig_out),
+    .u_MyInterfaceInSub3_other_setting(MyInterfaceInstanceInSub_other_setting),
+    .passThrough (passThrough)
+  );
+    assign outOther = MyInterfaceInstanceInSub_other_setting;
+
+    assign MyInterfaceInstanceInSub_setting = 0;
+    assign MyInterfaceInstanceInSub_mysig_out = sig;
+
+endmodule
+
+module SubModule2(
+
+    input logic clk,
+    input logic rst,
+    input logic u_MyInterfaceInSub2_setting,
+    output logic [3:0] u_MyInterfaceInSub2_other_setting,
+    input  logic [1:0] u_MyInterfaceInSub2_mysig_out,
+    input logic u_MyInterfaceInSub3_setting,
+    output logic [21:0] u_MyInterfaceInSub3_other_setting,
+    input  logic [1:0] u_MyInterfaceInSub3_mysig_out,
+    output logic [15:0] passThrough
+
+  );
+
+    always @(u_MyInterfaceInSub3_mysig_out) begin
+      if (u_MyInterfaceInSub3_mysig_out == 2'b00)
+        u_MyInterfaceInSub3_other_setting[21:0] = 1000;
+      else if (u_MyInterfaceInSub3_mysig_out == 2'b01)
+        u_MyInterfaceInSub3_other_setting[21:0] = 2000;
+      else if (u_MyInterfaceInSub3_mysig_out == 2'b10)
+        u_MyInterfaceInSub3_other_setting[21:0] = 3000;
+      else
+        u_MyInterfaceInSub3_other_setting[21:0] = 4000;
+    end
+
+    assign passThrough[7:0] = 124;
+    assign passThrough[15:8] = 200;
+
+endmodule

tests/svinterfaces/svinterface_at_top_tb.v

@@ -0,0 +1,68 @@
+`timescale 1ns/10ps
+
+module svinterface_at_top_tb;
+
+
+  logic clk;
+  logic rst;
+  logic [21:0] outOther;
+  logic [1:0] sig;
+  logic [1:0] sig_out;
+  logic flip;
+  logic [15:0] passThrough;
+  integer outfile;
+
+  logic interfaceInstanceAtTop_setting;
+  logic [2:0] interfaceInstanceAtTop_other_setting;
+  logic [1:0] interfaceInstanceAtTop_mysig_out;
+  logic [15:0] interfaceInstanceAtTop_passThrough;
+
+
+  TopModule u_dut (
+    .clk(clk),
+    .rst(rst),
+    .outOther(outOther),
+    .sig(sig),
+    .flip(flip),
+    .passThrough(passThrough),
+    .interfaceInstanceAtTop_setting(interfaceInstanceAtTop_setting),
+    .interfaceInstanceAtTop_other_setting(interfaceInstanceAtTop_other_setting),
+    .interfaceInstanceAtTop_mysig_out(interfaceInstanceAtTop_mysig_out),
+    .interfaceInstanceAtTop_passThrough(interfaceInstanceAtTop_passThrough),
+    .sig_out(sig_out)
+  );
+
+  initial begin
+    clk = 0;
+    while(1) begin
+      clk = ~clk;
+      #50;
+    end
+  end
+
+  initial begin
+    outfile = $fopen("output.txt");
+    rst = 1;
+    interfaceInstanceAtTop_setting = 0;
+    sig = 0;
+    flip = 0;
+    @(posedge clk);
+    #(2);
+    rst = 0;
+    @(posedge clk);
+    for(int j=0;j<2;j++) begin
+      for(int i=0;i<20;i++) begin
+        #(2);
+        flip = j;
+        sig = i;
+        @(posedge clk);
+      end
+    end
+    $finish;
+  end
+
+  always @(negedge clk) begin
+    $fdisplay(outfile, "%d %d %d %d", outOther, sig_out, passThrough, interfaceInstanceAtTop_mysig_out);
+  end
+
+endmodule

tests/svinterfaces/svinterface_at_top_tb_wrapper.v

@@ -0,0 +1,68 @@
+`timescale 1ns/10ps
+
+module svinterface_at_top_tb_wrapper;
+
+
+  logic clk;
+  logic rst;
+  logic [21:0] outOther;
+  logic [1:0] sig;
+  logic [1:0] sig_out;
+  logic flip;
+  logic [15:0] passThrough;
+  integer outfile;
+
+  logic interfaceInstanceAtTop_setting;
+  logic [2:0] interfaceInstanceAtTop_other_setting;
+  logic [1:0] interfaceInstanceAtTop_mysig_out;
+  logic [15:0] interfaceInstanceAtTop_passThrough;
+
+
+  TopModule u_dut (
+    .clk(clk),
+    .rst(rst),
+    .outOther(outOther),
+    .sig(sig),
+    .flip(flip),
+    .passThrough(passThrough),
+    .\interfaceInstanceAtTop.setting (interfaceInstanceAtTop_setting),
+    .\interfaceInstanceAtTop.other_setting (interfaceInstanceAtTop_other_setting),
+    .\interfaceInstanceAtTop.mysig_out (interfaceInstanceAtTop_mysig_out),
+    .\interfaceInstanceAtTop.passThrough (interfaceInstanceAtTop_passThrough),
+    .sig_out(sig_out)
+  );
+
+  initial begin
+    clk = 0;
+    while(1) begin
+      clk = ~clk;
+      #50;
+    end
+  end
+
+  initial begin
+    outfile = $fopen("output.txt");
+    rst = 1;
+    sig = 0;
+    interfaceInstanceAtTop_setting = 0;
+    flip = 0;
+    @(posedge clk);
+    #(2);
+    rst = 0;
+    @(posedge clk);
+    for(int j=0;j<2;j++) begin
+      for(int i=0;i<20;i++) begin
+        #(2);
+        flip = j;
+        sig = i;
+        @(posedge clk);
+      end
+    end
+    $finish;
+  end
+
+  always @(negedge clk) begin
+    $fdisplay(outfile, "%d %d %d %d", outOther, sig_out, passThrough, interfaceInstanceAtTop_mysig_out);
+  end
+
+endmodule

tests/svinterfaces/svinterface_at_top_wrapper.v

@@ -0,0 +1,33 @@
+`timescale 1ns/10ps
+
+module svinterface_at_top_wrapper(
+  input logic clk,
+  input logic rst,
+  output logic [21:0] outOther,
+  input logic [1:0] sig,
+  output logic [1:0] sig_out,
+  input logic flip,
+  output logic [15:0] passThrough,
+
+    input logic interfaceInstanceAtTop_setting,
+    output logic [2:0] interfaceInstanceAtTop_other_setting,
+    output logic [1:0] interfaceInstanceAtTop_mysig_out,
+    output logic [15:0] interfaceInstanceAtTop_passThrough,
+  );
+
+
+  TopModule u_dut (
+    .clk(clk),
+    .rst(rst),
+    .outOther(outOther),
+    .sig(sig),
+    .flip(flip),
+    .passThrough(passThrough),
+    .\interfaceInstanceAtTop.setting(interfaceInstanceAtTop_setting),
+    .\interfaceInstanceAtTop.other_setting(interfaceInstanceAtTop_other_setting),
+    .\interfaceInstanceAtTop.mysig_out(interfaceInstanceAtTop_mysig_out),
+    .\interfaceInstanceAtTop.passThrough(interfaceInstanceAtTop_passThrough),
+    .sig_out(sig_out)
+  );
+
+endmodule