yosys/frontends/liberty/liberty.cc

/*
 *  yosys -- Yosys Open SYnthesis Suite
 *
 *  Copyright (C) 2012  Claire Xenia Wolf <claire@yosyshq.com>
 *
 *  Permission to use, copy, modify, and/or distribute this software for any
 *  purpose with or without fee is hereby granted, provided that the above
 *  copyright notice and this permission notice appear in all copies.
 *
 *  THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 *  WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 *  MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 *  ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 *  WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 *  ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 *  OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 *
 */

#include "passes/techmap/libparse.h"
#include "kernel/register.h"
#include "kernel/log.h"

YOSYS_NAMESPACE_BEGIN

struct token_t {
	char type;
	RTLIL::SigSpec sig;
	token_t (char t) : type(t) { }
	token_t (char t, RTLIL::SigSpec s) : type(t), sig(s) { }
};

static RTLIL::SigSpec parse_func_identifier(RTLIL::Module *module, const char *&expr)
{
	log_assert(*expr != 0);

	int id_len = 0;
	while (('a' <= expr[id_len] && expr[id_len] <= 'z') || ('A' <= expr[id_len] && expr[id_len] <= 'Z') ||
			('0' <= expr[id_len] && expr[id_len] <= '9') || expr[id_len] == '.' ||
			expr[id_len] == '_' || expr[id_len] == '[' || expr[id_len] == ']') id_len++;

	if (id_len == 0)
		log_error("Expected identifier at `%s'.\n", expr);

	if (id_len == 1 && (*expr == '0' || *expr == '1'))
		return *(expr++) == '0' ? RTLIL::State::S0 : RTLIL::State::S1;

	std::string id = RTLIL::escape_id(std::string(expr, id_len));
	if (!module->wires_.count(id))
		log_error("Can't resolve wire name %s.\n", RTLIL::unescape_id(id).c_str());

	expr += id_len;
	return module->wires_.at(id);
}

static bool parse_func_reduce(RTLIL::Module *module, std::vector<token_t> &stack, token_t next_token)
{
	int top = int(stack.size())-1;

	if (0 <= top-1 && stack[top].type == 0 && stack[top-1].type == '!') {
		token_t t = token_t(0, module->NotGate(NEW_ID, stack[top].sig));
		stack.pop_back();
		stack.pop_back();
		stack.push_back(t);
		return true;
	}

	if (0 <= top-1 && stack[top].type == '\'' && stack[top-1].type == 0) {
		token_t t = token_t(0, module->NotGate(NEW_ID, stack[top-1].sig));
		stack.pop_back();
		stack.pop_back();
		stack.push_back(t);
		return true;
	}

	if (0 <= top && stack[top].type == 0) {
		if (next_token.type == '\'')
			return false;
		stack[top].type = 1;
		return true;
	}

	if (0 <= top-2 && stack[top-2].type == 1 && stack[top-1].type == '^' && stack[top].type == 1) {
		token_t t = token_t(1, module->XorGate(NEW_ID, stack[top-2].sig, stack[top].sig));
		stack.pop_back();
		stack.pop_back();
		stack.pop_back();
		stack.push_back(t);
		return true;
	}

	if (0 <= top && stack[top].type == 1) {
		if (next_token.type == '^')
			return false;
		stack[top].type = 2;
		return true;
	}

	if (0 <= top-1 && stack[top-1].type == 2 && stack[top].type == 2) {
		token_t t = token_t(2, module->AndGate(NEW_ID, stack[top-1].sig, stack[top].sig));
		stack.pop_back();
		stack.pop_back();
		stack.push_back(t);
		return true;
	}

	if (0 <= top-2 && stack[top-2].type == 2 && (stack[top-1].type == '*' || stack[top-1].type == '&') && stack[top].type == 2) {
		token_t t = token_t(2, module->AndGate(NEW_ID, stack[top-2].sig, stack[top].sig));
		stack.pop_back();
		stack.pop_back();
		stack.pop_back();
		stack.push_back(t);
		return true;
	}

	if (0 <= top && stack[top].type == 2) {
		if (next_token.type == '*' || next_token.type == '&' || next_token.type == 0 || next_token.type == '(' || next_token.type == '!')
			return false;
		stack[top].type = 3;
		return true;
	}

	if (0 <= top-2 && stack[top-2].type == 3 && (stack[top-1].type == '+' || stack[top-1].type == '|') && stack[top].type == 3) {
		token_t t = token_t(3, module->OrGate(NEW_ID, stack[top-2].sig, stack[top].sig));
		stack.pop_back();
		stack.pop_back();
		stack.pop_back();
		stack.push_back(t);
		return true;
	}

	if (0 <= top-2 && stack[top-2].type == '(' && stack[top-1].type == 3 && stack[top].type == ')') {
		token_t t = token_t(0, stack[top-1].sig);
		stack.pop_back();
		stack.pop_back();
		stack.pop_back();
		stack.push_back(t);
		return true;
	}

	return false;
}

static RTLIL::SigSpec parse_func_expr(RTLIL::Module *module, const char *expr)
{
	const char *orig_expr = expr;
	std::vector<token_t> stack;

	while (*expr)
	{
		if (*expr == ' ' || *expr == '\t' || *expr == '\r' || *expr == '\n' || *expr == '"') {
			expr++;
			continue;
		}

		token_t next_token(0);
		if (*expr == '(' || *expr == ')' || *expr == '\'' || *expr == '!' || *expr == '^' || *expr == '*' || *expr == '+' || *expr == '|' || *expr == '&')
			next_token = token_t(*(expr++));
		else
			next_token = token_t(0, parse_func_identifier(module, expr));

		while (parse_func_reduce(module, stack, next_token)) {}
		stack.push_back(next_token);
	}

	while (parse_func_reduce(module, stack, token_t('.'))) {}

#if 0
	for (size_t i = 0; i < stack.size(); i++)
		if (stack[i].type < 16)
			log("%3d: %d %s\n", int(i), stack[i].type, log_signal(stack[i].sig));
		else
			log("%3d: %c\n", int(i), stack[i].type);
#endif

	if (stack.size() != 1 || stack.back().type != 3)
		log_error("Parser error in function expr `%s'.\n", orig_expr);

	return stack.back().sig;
}

static RTLIL::SigSpec create_tristate(RTLIL::Module *module, RTLIL::SigSpec func, const char *three_state_expr)
{
	RTLIL::SigSpec three_state = parse_func_expr(module, three_state_expr);

	RTLIL::Cell *cell = module->addCell(NEW_ID, ID($tribuf));
	cell->setParam(ID::WIDTH, GetSize(func));
	cell->setPort(ID::A, func);
	cell->setPort(ID::EN, module->NotGate(NEW_ID, three_state));
	cell->setPort(ID::Y, module->addWire(NEW_ID));
	return cell->getPort(ID::Y);
}

static void create_ff(RTLIL::Module *module, const LibertyAst *node)
{
	RTLIL::SigSpec iq_sig(module->addWire(RTLIL::escape_id(node->args.at(0))));
	RTLIL::SigSpec iqn_sig(module->addWire(RTLIL::escape_id(node->args.at(1))));

	RTLIL::SigSpec clk_sig, data_sig, clear_sig, preset_sig;
	bool clk_polarity = true, clear_polarity = true, preset_polarity = true;

	for (auto child : node->children) {
		if (child->id == "clocked_on")
			clk_sig = parse_func_expr(module, child->value.c_str());
		if (child->id == "next_state")
			data_sig = parse_func_expr(module, child->value.c_str());
		if (child->id == "clear")
			clear_sig = parse_func_expr(module, child->value.c_str());
		if (child->id == "preset")
			preset_sig = parse_func_expr(module, child->value.c_str());
	}

	if (clk_sig.size() == 0 || data_sig.size() == 0)
		log_error("FF cell %s has no next_state and/or clocked_on attribute.\n", log_id(module->name));

	for (bool rerun_invert_rollback = true; rerun_invert_rollback;)
	{
		rerun_invert_rollback = false;

		for (auto &it : module->cells_) {
			if (it.second->type == ID($_NOT_) && it.second->getPort(ID::Y) == clk_sig) {
				clk_sig = it.second->getPort(ID::A);
				clk_polarity = !clk_polarity;
				rerun_invert_rollback = true;
			}
			if (it.second->type == ID($_NOT_) && it.second->getPort(ID::Y) == clear_sig) {
				clear_sig = it.second->getPort(ID::A);
				clear_polarity = !clear_polarity;
				rerun_invert_rollback = true;
			}
			if (it.second->type == ID($_NOT_) && it.second->getPort(ID::Y) == preset_sig) {
				preset_sig = it.second->getPort(ID::A);
				preset_polarity = !preset_polarity;
				rerun_invert_rollback = true;
			}
		}
	}

	RTLIL::Cell *cell = module->addCell(NEW_ID, ID($_NOT_));
	cell->setPort(ID::A, iq_sig);
	cell->setPort(ID::Y, iqn_sig);

	cell = module->addCell(NEW_ID, "");
	cell->setPort(ID::D, data_sig);
	cell->setPort(ID::Q, iq_sig);
	cell->setPort(ID::C, clk_sig);

	if (clear_sig.size() == 0 && preset_sig.size() == 0) {
		cell->type = stringf("$_DFF_%c_", clk_polarity ? 'P' : 'N');
	}

	if (clear_sig.size() == 1 && preset_sig.size() == 0) {
		cell->type = stringf("$_DFF_%c%c0_", clk_polarity ? 'P' : 'N', clear_polarity ? 'P' : 'N');
		cell->setPort(ID::R, clear_sig);
	}

	if (clear_sig.size() == 0 && preset_sig.size() == 1) {
		cell->type = stringf("$_DFF_%c%c1_", clk_polarity ? 'P' : 'N', preset_polarity ? 'P' : 'N');
		cell->setPort(ID::R, preset_sig);
	}

	if (clear_sig.size() == 1 && preset_sig.size() == 1) {
		cell->type = stringf("$_DFFSR_%c%c%c_", clk_polarity ? 'P' : 'N', preset_polarity ? 'P' : 'N', clear_polarity ? 'P' : 'N');
		cell->setPort(ID::S, preset_sig);
		cell->setPort(ID::R, clear_sig);
	}

	log_assert(!cell->type.empty());
}

static bool create_latch(RTLIL::Module *module, const LibertyAst *node, bool flag_ignore_miss_data_latch)
{
	RTLIL::SigSpec iq_sig(module->addWire(RTLIL::escape_id(node->args.at(0))));
	RTLIL::SigSpec iqn_sig(module->addWire(RTLIL::escape_id(node->args.at(1))));

	RTLIL::SigSpec enable_sig, data_sig, clear_sig, preset_sig;
	bool enable_polarity = true, clear_polarity = true, preset_polarity = true;

	for (auto child : node->children) {
		if (child->id == "enable")
			enable_sig = parse_func_expr(module, child->value.c_str());
		if (child->id == "data_in")
			data_sig = parse_func_expr(module, child->value.c_str());
		if (child->id == "clear")
			clear_sig = parse_func_expr(module, child->value.c_str());
		if (child->id == "preset")
			preset_sig = parse_func_expr(module, child->value.c_str());
	}

	if (enable_sig.size() == 0 || data_sig.size() == 0) {
		if (!flag_ignore_miss_data_latch)
			log_error("Latch cell %s has no data_in and/or enable attribute.\n", log_id(module->name));
		else
			log("Ignored latch cell %s with no data_in and/or enable attribute.\n", log_id(module->name));

		return false;
	}

	for (bool rerun_invert_rollback = true; rerun_invert_rollback;)
	{
		rerun_invert_rollback = false;

		for (auto &it : module->cells_) {
			if (it.second->type == ID($_NOT_) && it.second->getPort(ID::Y) == enable_sig) {
				enable_sig = it.second->getPort(ID::A);
				enable_polarity = !enable_polarity;
				rerun_invert_rollback = true;
			}
			if (it.second->type == ID($_NOT_) && it.second->getPort(ID::Y) == clear_sig) {
				clear_sig = it.second->getPort(ID::A);
				clear_polarity = !clear_polarity;
				rerun_invert_rollback = true;
			}
			if (it.second->type == ID($_NOT_) && it.second->getPort(ID::Y) == preset_sig) {
				preset_sig = it.second->getPort(ID::A);
				preset_polarity = !preset_polarity;
				rerun_invert_rollback = true;
			}
		}
	}

	RTLIL::Cell *cell = module->addCell(NEW_ID, ID($_NOT_));
	cell->setPort(ID::A, iq_sig);
	cell->setPort(ID::Y, iqn_sig);

	if (clear_sig.size() == 1)
	{
		RTLIL::SigSpec clear_negative = clear_sig;
		RTLIL::SigSpec clear_enable = clear_sig;

		if (clear_polarity == true || clear_polarity != enable_polarity)
		{
			RTLIL::Cell *inv = module->addCell(NEW_ID, ID($_NOT_));
			inv->setPort(ID::A, clear_sig);
			inv->setPort(ID::Y, module->addWire(NEW_ID));

			if (clear_polarity == true)
				clear_negative = inv->getPort(ID::Y);
			if (clear_polarity != enable_polarity)
				clear_enable = inv->getPort(ID::Y);
		}

		RTLIL::Cell *data_gate = module->addCell(NEW_ID, ID($_AND_));
		data_gate->setPort(ID::A, data_sig);
		data_gate->setPort(ID::B, clear_negative);
		data_gate->setPort(ID::Y, data_sig = module->addWire(NEW_ID));

		RTLIL::Cell *enable_gate = module->addCell(NEW_ID, enable_polarity ? ID($_OR_) : ID($_AND_));
		enable_gate->setPort(ID::A, enable_sig);
		enable_gate->setPort(ID::B, clear_enable);
		enable_gate->setPort(ID::Y, data_sig = module->addWire(NEW_ID));
	}

	if (preset_sig.size() == 1)
	{
		RTLIL::SigSpec preset_positive = preset_sig;
		RTLIL::SigSpec preset_enable = preset_sig;

		if (preset_polarity == false || preset_polarity != enable_polarity)
		{
			RTLIL::Cell *inv = module->addCell(NEW_ID, ID($_NOT_));
			inv->setPort(ID::A, preset_sig);
			inv->setPort(ID::Y, module->addWire(NEW_ID));

			if (preset_polarity == false)
				preset_positive = inv->getPort(ID::Y);
			if (preset_polarity != enable_polarity)
				preset_enable = inv->getPort(ID::Y);
		}

		RTLIL::Cell *data_gate = module->addCell(NEW_ID, ID($_OR_));
		data_gate->setPort(ID::A, data_sig);
		data_gate->setPort(ID::B, preset_positive);
		data_gate->setPort(ID::Y, data_sig = module->addWire(NEW_ID));

		RTLIL::Cell *enable_gate = module->addCell(NEW_ID, enable_polarity ? ID($_OR_) : ID($_AND_));
		enable_gate->setPort(ID::A, enable_sig);
		enable_gate->setPort(ID::B, preset_enable);
		enable_gate->setPort(ID::Y, data_sig = module->addWire(NEW_ID));
	}

	cell = module->addCell(NEW_ID, stringf("$_DLATCH_%c_", enable_polarity ? 'P' : 'N'));
	cell->setPort(ID::D, data_sig);
	cell->setPort(ID::Q, iq_sig);
	cell->setPort(ID::E, enable_sig);

	return true;
}

void parse_type_map(std::map<std::string, std::tuple<int, int, bool>> &type_map, const LibertyAst *ast)
{
	for (auto type_node : ast->children)
	{
		if (type_node->id != "type" || type_node->args.size() != 1)
			continue;

		std::string type_name = type_node->args.at(0);
		int bit_width = -1, bit_from = -1, bit_to = -1;
		bool upto = false;

		for (auto child : type_node->children)
		{
			if (child->id == "base_type" && child->value != "array")
				goto next_type;

			if (child->id == "data_type" && child->value != "bit")
				goto next_type;

			if (child->id == "bit_width")
				bit_width = atoi(child->value.c_str());

			if (child->id == "bit_from")
				bit_from = atoi(child->value.c_str());

			if (child->id == "bit_to")
				bit_to = atoi(child->value.c_str());

			if (child->id == "downto" && (child->value == "0" || child->value == "false" || child->value == "FALSE"))
				upto = true;
		}

		if (bit_width != (std::max(bit_from, bit_to) - std::min(bit_from, bit_to) + 1))
			log_error("Incompatible array type '%s': bit_width=%d, bit_from=%d, bit_to=%d.\n",
					type_name.c_str(), bit_width, bit_from, bit_to);

		type_map[type_name] = std::tuple<int, int, bool>(bit_width, std::min(bit_from, bit_to), upto);
	next_type:;
	}
}

struct LibertyFrontend : public Frontend {
	LibertyFrontend() : Frontend("liberty", "read cells from liberty file") { }
	void help() override
	{
		//   |---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|
		log("\n");
		log("    read_liberty [filename]\n");
		log("\n");
		log("Read cells from liberty file as modules into current design.\n");
		log("\n");
		log("    -lib\n");
		log("        only create empty blackbox modules\n");
		log("\n");
		log("    -wb\n");
		log("        mark imported cells as whiteboxes\n");
		log("\n");
		log("    -nooverwrite\n");
		log("        ignore re-definitions of modules. (the default behavior is to\n");
		log("        create an error message if the existing module is not a blackbox\n");
		log("        module, and overwrite the existing module if it is  a blackbox module.)\n");
		log("\n");
		log("    -overwrite\n");
		log("        overwrite existing modules with the same name\n");
		log("\n");
		log("    -ignore_miss_func\n");
		log("        ignore cells with missing function specification of outputs\n");
		log("\n");
		log("    -ignore_miss_dir\n");
		log("        ignore cells with a missing or invalid direction\n");
		log("        specification on a pin\n");
		log("\n");
		log("    -ignore_miss_data_latch\n");
		log("        ignore latches with missing data and/or enable pins\n");
		log("\n");
		log("    -setattr <attribute_name>\n");
		log("        set the specified attribute (to the value 1) on all loaded modules\n");
		log("\n");
		log("    -unit_delay\n");
		log("        import combinational timing arcs under the unit delay model\n");
		log("\n");
	}
	void execute(std::istream *&f, std::string filename, std::vector<std::string> args, RTLIL::Design *design) override
	{
		bool flag_lib = false;
		bool flag_wb = false;
		bool flag_nooverwrite = false;
		bool flag_overwrite = false;
		bool flag_ignore_miss_func = false;
		bool flag_ignore_miss_dir  = false;
		bool flag_ignore_miss_data_latch = false;
		bool flag_unit_delay = false;
		std::vector<std::string> attributes;

		size_t argidx;
		for (argidx = 1; argidx < args.size(); argidx++) {
			std::string arg = args[argidx];
			if (arg == "-lib") {
				flag_lib = true;
				continue;
			}
			if (arg == "-wb") {
				flag_wb = true;
				continue;
			}
			if (arg == "-ignore_redef" || arg == "-nooverwrite") {
				flag_nooverwrite = true;
				flag_overwrite = false;
				continue;
			}
			if (arg == "-overwrite") {
				flag_nooverwrite = false;
				flag_overwrite = true;
				continue;
			}
			if (arg == "-ignore_miss_func") {
				flag_ignore_miss_func = true;
				continue;
			}
			if (arg == "-ignore_miss_dir") {
				flag_ignore_miss_dir = true;
				continue;
			}
			if (arg == "-ignore_miss_data_latch") {
				flag_ignore_miss_data_latch = true;
				continue;
			}
			if (arg == "-setattr" && argidx+1 < args.size()) {
				attributes.push_back(RTLIL::escape_id(args[++argidx]));
				continue;
			}
			if (arg == "-unit_delay") {
				flag_unit_delay = true;
				continue;
			}
			break;
		}
		extra_args(f, filename, args, argidx);

		if (flag_wb && flag_lib)
			log_error("-wb and -lib cannot be specified together!\n");

		log_header(design, "Executing Liberty frontend: %s\n", filename.c_str());

		LibertyParser parser(*f);
		int cell_count = 0;

		std::map<std::string, std::tuple<int, int, bool>> global_type_map;
		parse_type_map(global_type_map, parser.ast);

		for (auto cell : parser.ast->children)
		{
			if (cell->id != "cell" || cell->args.size() != 1)
				continue;

			// log("Processing cell type %s.\n", RTLIL::unescape_id(cell_name).c_str());

			std::map<std::string, std::tuple<int, int, bool>> type_map = global_type_map;
			parse_type_map(type_map, cell);

			RTLIL::Module *module = new RTLIL::Module;
			std::string cell_name = RTLIL::escape_id(cell->args.at(0));
			module->name = cell_name;

			if (flag_lib)
				module->set_bool_attribute(ID::blackbox);

			if (flag_wb)
				module->set_bool_attribute(ID::whitebox);

			const LibertyAst *area = cell->find("area");
			if (area)
				module->attributes[ID::area] = area->value;

			for (auto &attr : attributes)
				module->attributes[attr] = 1;

			for (auto node : cell->children)
			{
				if (node->id == "pin" && node->args.size() == 1) {
					const LibertyAst *dir = node->find("direction");
					if (!dir || (dir->value != "input" && dir->value != "output" && dir->value != "inout" && dir->value != "internal"))
					{
						if (!flag_ignore_miss_dir)
						{
							log_error("Missing or invalid direction for pin %s on cell %s.\n", node->args.at(0).c_str(), log_id(module->name));
						} else {
							log("Ignoring cell %s with missing or invalid direction for pin %s.\n", log_id(module->name), node->args.at(0).c_str());
							delete module;
							goto skip_cell;
						}
					}
					if (!flag_lib || dir->value != "internal")
						module->addWire(RTLIL::escape_id(node->args.at(0)));
				}

				if (node->id == "bus" && node->args.size() == 1)
				{
					if (!flag_lib)
						log_error("Error in cell %s: bus interfaces are only supported in -lib mode.\n", log_id(cell_name));

					const LibertyAst *dir = node->find("direction");

					if (dir == nullptr) {
						const LibertyAst *pin = node->find("pin");
						if (pin != nullptr)
							dir = pin->find("direction");
					}

					if (!dir || (dir->value != "input" && dir->value != "output" && dir->value != "inout" && dir->value != "internal"))
						log_error("Missing or invalid direction for bus %s on cell %s.\n", node->args.at(0).c_str(), log_id(module->name));

					if (dir->value == "internal")
						continue;

					const LibertyAst *bus_type_node = node->find("bus_type");

					if (!bus_type_node || !type_map.count(bus_type_node->value))
						log_error("Unknown or unsupported type for bus interface %s on cell %s.\n",
								node->args.at(0).c_str(), log_id(cell_name));

					int bus_type_width = std::get<0>(type_map.at(bus_type_node->value));
					int bus_type_offset = std::get<1>(type_map.at(bus_type_node->value));
					bool bus_type_upto = std::get<2>(type_map.at(bus_type_node->value));

					Wire *wire = module->addWire(RTLIL::escape_id(node->args.at(0)), bus_type_width);
					wire->start_offset = bus_type_offset;
					wire->upto = bus_type_upto;

					if (dir->value == "input" || dir->value == "inout")
						wire->port_input = true;

					if (dir->value == "output" || dir->value == "inout")
						wire->port_output = true;
				}
			}

			if (!flag_lib)
			{
				// some liberty files do not put ff/latch at the beginning of a cell
				// try to find "ff" or "latch" and create FF/latch _before_ processing all other nodes
				for (auto node : cell->children)
				{
					if (node->id == "ff" && node->args.size() == 2)
						create_ff(module, node);
					if (node->id == "latch" && node->args.size() == 2)
						if (!create_latch(module, node, flag_ignore_miss_data_latch)) {
							delete module;
							goto skip_cell;
						}
				}
			}

			for (auto node : cell->children)
			{
				if (node->id == "pin" && node->args.size() == 1)
				{
					const LibertyAst *dir = node->find("direction");

					if (flag_lib && dir->value == "internal")
						continue;

					RTLIL::Wire *wire = module->wires_.at(RTLIL::escape_id(node->args.at(0)));
					log_assert(wire);

					const LibertyAst *capacitance = node->find("capacitance");
					if (capacitance)
						wire->attributes[ID::capacitance] = capacitance->value;

					if (dir && dir->value == "inout") {
						wire->port_input = true;
						wire->port_output = true;
					}

					if (dir && dir->value == "input") {
						wire->port_input = true;
						continue;
					}

					if (dir && dir->value == "output")
						wire->port_output = true;

					if (flag_lib)
						continue;

					const LibertyAst *func = node->find("function");
					if (func == NULL)
					{
						if (dir->value != "inout") { // allow inout with missing function, can be used for power pins
							if (!flag_ignore_miss_func)
							{
								log_error("Missing function on output %s of cell %s.\n", log_id(wire->name), log_id(module->name));
							} else {
								log("Ignoring cell %s with missing function on output %s.\n", log_id(module->name), log_id(wire->name));
								delete module;
								goto skip_cell;
							}
						}
					} else {
						RTLIL::SigSpec out_sig = parse_func_expr(module, func->value.c_str());
						const LibertyAst *three_state = node->find("three_state");
						if (three_state) {
							out_sig = create_tristate(module, out_sig, three_state->value.c_str());
						}
						module->connect(RTLIL::SigSig(wire, out_sig));
					}

					if (flag_unit_delay) {
						pool<Wire *> done;

						for (auto timing : node->children)
						if (timing->id == "timing" && timing->args.empty()) {
							auto type = timing->find("timing_type");
							auto related_pin = timing->find("related_pin");
							if (!type || type->value != "combinational" || !related_pin)
								continue;

							Wire *related = module->wire(RTLIL::escape_id(related_pin->value));
							if (!related)
								log_error("Failed to find related pin %s for timing of pin %s on %s\n",
										  related_pin->value.c_str(), log_id(wire), log_id(module));

							if (done.count(related))
								continue;

							RTLIL::Cell *spec = module->addCell(NEW_ID, ID($specify2));
							spec->setParam(ID::SRC_WIDTH, 1);
							spec->setParam(ID::DST_WIDTH, 1);
							spec->setParam(ID::T_FALL_MAX, 1000);
							spec->setParam(ID::T_FALL_TYP, 1000);
							spec->setParam(ID::T_FALL_MIN, 1000);
							spec->setParam(ID::T_RISE_MAX, 1000);
							spec->setParam(ID::T_RISE_TYP, 1000);
							spec->setParam(ID::T_RISE_MIN, 1000);
							spec->setParam(ID::SRC_DST_POL, false);
							spec->setParam(ID::SRC_DST_PEN, false);
							spec->setParam(ID::FULL, false);
							spec->setPort(ID::EN, Const(1, 1));
							spec->setPort(ID::SRC, related);
							spec->setPort(ID::DST, wire);
							done.insert(related);
						}
					}
				}
			}

			if (design->has(cell_name)) {
				Module *existing_mod = design->module(cell_name);
				if (!flag_nooverwrite && !flag_overwrite && !existing_mod->get_bool_attribute(ID::blackbox)) {
					log_error("Re-definition of cell/module %s!\n", log_id(cell_name));
				} else if (flag_nooverwrite) {
					log("Ignoring re-definition of module %s.\n", log_id(cell_name));
					delete module;
					goto skip_cell;
				} else {
					log("Replacing existing%s module %s.\n", existing_mod->get_bool_attribute(ID::blackbox) ? " blackbox" : "", log_id(cell_name));
					design->remove(existing_mod);
				}
			}

			module->fixup_ports();
			design->add(module);
			cell_count++;
skip_cell:;
		}

		log("Imported %d cell types from liberty file.\n", cell_count);
	}
} LibertyFrontend;

YOSYS_NAMESPACE_END