wrapcell: Optionally track unused outputs

passes/cmds/wrapcell.cc

@@ -18,12 +18,37 @@
  */
 #include "kernel/yosys.h"
 #include "kernel/celltypes.h"
+#include "kernel/sigtools.h"
 #include "backends/rtlil/rtlil_backend.h"
 
 USING_YOSYS_NAMESPACE
 PRIVATE_NAMESPACE_BEGIN
 
-std::optional<std::string> format(std::string fmt, const dict<IdString, Const> &parameters)
+bool has_fmt_field(std::string fmt, std::string field_name)
+{
+	auto it = fmt.begin();
+	while (it != fmt.end()) {
+		if (*it == '{') {
+			it++;
+			auto beg = it;
+			while (it != fmt.end() && *it != '}') it++;
+			if (it == fmt.end())
+				return false;
+
+			if (std::string(beg, it) == field_name)
+				return true;
+		}
+		it++;
+	}
+	return false;
+}
+
+struct ContextData {
+	std::string unused_outputs;
+};
+
+std::optional<std::string> format(std::string fmt, const dict<IdString, Const> &parameters,
+								  const ContextData &context)
 {
 	std::stringstream result;
 
@@ -38,13 +63,19 @@ std::optional<std::string> format(std::string fmt, const dict<IdString, Const> &
 				return {};
 			}
 
-			auto id = RTLIL::escape_id(std::string(beg, it));
-			if (!parameters.count(id)) {
-				log("Parameter %s referenced in format string '%s' not found\n", log_id(id), fmt.c_str());
-				return {};
-			}
+			std::string param_name = {beg, it};
 
-			RTLIL_BACKEND::dump_const(result, parameters.at(id));
+			if (param_name == "%unused") {
+				result << context.unused_outputs;
+			} else {
+				auto id = RTLIL::escape_id(std::string(beg, it));
+				if (!parameters.count(id)) {
+					log("Parameter %s referenced in format string '%s' not found\n", log_id(id), fmt.c_str());
+					return {};
+				}
+
+				RTLIL_BACKEND::dump_const(result, parameters.at(id));
+			}
 		} else {
 			result << *it;
 		}
@@ -54,6 +85,45 @@ std::optional<std::string> format(std::string fmt, const dict<IdString, Const> &
 	return {result.str()};
 }
 
+struct Chunk {
+	IdString port;
+	int base, len;
+
+	Chunk(IdString id, int base, int len)
+		: port(id), base(base), len(len) {}
+
+	IdString format(Cell *cell)
+	{
+		if (len == cell->getPort(port).size())
+			return port;
+		else if (len == 1)
+			return stringf("%s[%d]", port.c_str(), base);
+		else
+			return stringf("%s[%d:%d]", port.c_str(), base + len - 1, base);
+	}
+
+	SigSpec sample(Cell *cell)
+	{
+		return cell->getPort(port).extract(base, len);
+	}
+};
+
+// Joins contiguous runs of bits into a 'Chunk'
+std::vector<Chunk> collect_chunks(std::vector<std::pair<IdString, int>> bits)
+{
+	std::vector<Chunk> ret;
+	std::sort(bits.begin(), bits.end());
+	for (auto it = bits.begin(); it != bits.end();) {
+		auto sep = it + 1;
+		for (; sep != bits.end() &&
+				sep->first == it->first &&
+				sep->second == (sep - 1)->second + 1; sep++);
+		ret.emplace_back(it->first, it->second, sep - it);
+		it = sep;
+	}
+	return ret;
+}
+
 struct WrapcellPass : Pass {
 	WrapcellPass() : Pass("wrapcell", "wrap individual cells into new modules") {}
 
@@ -68,6 +138,10 @@ struct WrapcellPass : Pass {
 		log("parameter values as specified in curly brackets. If the named module already\n");
 		log("exists, it is reused.\n");
 		log("\n");
+		log("If the template contains the special string '{%%unused}', the command tracks\n");
+		log("unused output ports -- specialized wrapper modules will be generated per every\n");
+		log("distinct set of unused port bits as appearing on any selected cell.\n");
+		log("\n");
 		log("    -setattr <attribute-name>\n");
 		log("        set the given boolean attribute on each created wrapper module\n");
 		log("\n");
@@ -114,43 +188,89 @@ struct WrapcellPass : Pass {
 		CellTypes ct;
 		ct.setup();
 
+		bool tracking_unused = has_fmt_field(name_fmt, "%unused");
+
 		for (auto module : d->selected_modules()) {
+			SigPool unused;
+
+			for (auto wire : module->wires())
+			if (wire->has_attribute(ID::unused_bits)) {
+				std::string str = wire->get_string_attribute(ID::unused_bits);
+				for (auto it = str.begin(); it != str.end();) {
+					auto sep = it;
+					for (; sep != str.end() && *sep != ' '; sep++);
+					unused.add(SigBit(wire, std::stoi(std::string(it, sep))));
+					for (it = sep; it != str.end() && *it == ' '; it++);
+				}
+			}
+
 			for (auto cell : module->selected_cells()) {
-				std::optional<std::string> unescaped_name = format(name_fmt, cell->parameters);
+				Module *subm;
+				Cell *subcell;
+
+				if (!ct.cell_known(cell->type))
+					log_error("Non-internal cell type '%s' on cell '%s' in module '%s' unsupported\n",
+							  log_id(cell->type), log_id(cell), log_id(module));
+
+				std::vector<std::pair<IdString, int>> unused_outputs, used_outputs;
+				for (auto conn : cell->connections()) {
+					if (ct.cell_output(cell->type, conn.first))
+					for (int i = 0; i < conn.second.size(); i++) {
+						if (tracking_unused && unused.check(conn.second[i]))
+							unused_outputs.emplace_back(conn.first, i);
+						else
+							used_outputs.emplace_back(conn.first, i);
+					}
+				}
+
+				ContextData context;
+				if (!unused_outputs.empty()) {
+					context.unused_outputs += "_unused";
+					for (auto chunk : collect_chunks(unused_outputs))
+						context.unused_outputs += "_" + RTLIL::unescape_id(chunk.format(cell));
+				}
+
+				std::optional<std::string> unescaped_name = format(name_fmt, cell->parameters, context);
 				if (!unescaped_name)
 					log_error("Formatting error when processing cell '%s' in module '%s'\n",
 							  log_id(cell), log_id(module));
 
 				IdString name = RTLIL::escape_id(unescaped_name.value());
+				if (d->module(name))
+					goto replace_cell;
 
-				if (d->module(name)) {
-					cell->type = name;
-					cell->parameters.clear();
-					continue;
+				subm = d->addModule(name);
+				subcell = subm->addCell("$1", cell->type);
+				for (auto conn : cell->connections()) {
+					if (ct.cell_output(cell->type, conn.first)) {
+						// Insert marker bits as placehodlers which need to be replaced
+						subcell->setPort(conn.first, SigSpec(RTLIL::Sm, conn.second.size()));
+					} else {
+						Wire *w = subm->addWire(conn.first, conn.second.size());
+						w->port_input = true;
+						subcell->setPort(conn.first, w);
+					}
 				}
 
-				if (!ct.cell_known(cell->type))
-					log_error("Non-internal cell type '%s' on cell '%s' in module '%s' unsupported\n",
-							  log_id(cell->type), log_id(cell), log_id(module));
+				for (auto chunk : collect_chunks(used_outputs)) {
+					Wire *w = subm->addWire(chunk.format(cell), chunk.len);
+					w->port_output = true;
+					subcell->connections_[chunk.port].replace(chunk.base, w);
+				}
 
-				Module *subm = d->addModule(name);
-				Cell *subcell = subm->addCell("$1", cell->type);
-				for (auto conn : cell->connections()) {
-					Wire *w = subm->addWire(conn.first, conn.second.size());
-					if (ct.cell_output(cell->type, w->name))
-						w->port_output = true;
-					else
-						w->port_input = true;
-					subcell->setPort(conn.first, w);
+				for (auto chunk : collect_chunks(unused_outputs)) {
+					Wire *w = subm->addWire(chunk.format(cell), chunk.len);
+					subcell->connections_[chunk.port].replace(chunk.base, w);
 				}
+
 				subcell->parameters = cell->parameters;
 				subm->fixup_ports();
 
 				for (auto rule : attributes) {
 					if (rule.value_fmt.empty()) {
 						subm->set_bool_attribute(rule.name);
 					} else {
-						std::optional<std::string> value = format(rule.value_fmt, cell->parameters);
+						std::optional<std::string> value = format(rule.value_fmt, cell->parameters, context);
 
 						if (!value)
 							log_error("Formatting error when processing cell '%s' in module '%s'\n",
@@ -160,8 +280,20 @@ struct WrapcellPass : Pass {
 					}
 				}
 
-				cell->type = name;
+			replace_cell:
 				cell->parameters.clear();
+
+				dict<IdString, SigSpec> new_connections;
+
+				for (auto conn : cell->connections())
+				if (!ct.cell_output(cell->type, conn.first))
+					new_connections[conn.first] = conn.second;
+
+				for (auto chunk : collect_chunks(used_outputs))
+					new_connections[chunk.format(cell)] = chunk.sample(cell);
+
+				cell->type = name;
+				cell->connections_ = new_connections;
 			}
 		}
 	}

tests/various/wrapcell.ys

@@ -18,8 +18,40 @@ EOF
 
 wreduce
 wrapcell -setattr foo -formatattr bar w{Y_WIDTH} -name OR_{A_WIDTH}_{B_WIDTH}_{Y_WIDTH}
+check -assert
 select -assert-count 2 top/t:OR_2_3_3
 select -assert-count 1 top/t:OR_3_4_4
 select -assert-none top/t:OR_2_3_3 top/t:OR_3_4_4 %% top/t:* %D
 select -assert-mod-count 2 OR_2_3_3 OR_3_4_4
 select -assert-mod-count 2 A:bar=w3 A:bar=w4
+
+design -reset
+read_verilog <<EOF
+module top(
+	input [1:0] a,
+	input [2:0] b,
+	output [2:0] y,
+	input [2:0] a2,
+	input [3:0] b2,
+	output [3:0] y2,
+ 	input [1:0] a3,
+ 	input [2:0] b3,
+ 	output [2:0] y3
+);
+	assign y = a | (*keep*) b;
+	assign y2 = a2 | (*keep*) b2;
+	wire [2:0] y3_ = a3 | (*keep*) b3;
+	assign y3 = {y3_[2], y3_[0]};
+endmodule
+EOF
+
+opt_clean
+wreduce
+wrapcell -setattr foo -formatattr bar w{Y_WIDTH} -name OR_{A_WIDTH}_{B_WIDTH}_{Y_WIDTH}{%unused}
+check -assert
+select -assert-count 1 top/t:OR_2_3_3
+select -assert-count 1 top/t:OR_2_3_3_unused_Y[1]
+select -assert-count 1 top/t:OR_3_4_4
+select -assert-none top/t:OR_2_3_3 top/t:OR_3_4_4 top/t:OR_2_3_3_unused_Y[1] %% top/t:* %D
+select -assert-mod-count 2 OR_2_3_3 OR_3_4_4
+select -assert-mod-count 3 A:bar=w3 A:bar=w4