kernel/consteval.h - third_party/yosys - Git at Google

 /*
  *  yosys -- Yosys Open SYnthesis Suite
  *
  *  Copyright (C) 2012  Clifford Wolf <clifford@clifford.at>
  *
  *  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.
  *
  */

 #ifndef CONSTEVAL_H
 #define CONSTEVAL_H

 #include "kernel/rtlil.h"
 #include "kernel/sigtools.h"
 #include "kernel/celltypes.h"
 #include "kernel/macc.h"

 YOSYS_NAMESPACE_BEGIN

 struct ConstEval
 {
 	RTLIL::Module *module;
 	SigMap assign_map;
 	SigMap values_map;
 	SigPool stop_signals;
 	SigSet<RTLIL::Cell*> sig2driver;
 	std::set<RTLIL::Cell*> busy;
 	std::vector<SigMap> stack;
 	RTLIL::State defaultval;

 	ConstEval(RTLIL::Module *module, RTLIL::State defaultval = RTLIL::State::Sm) : module(module), assign_map(module), defaultval(defaultval)
 	{
 		CellTypes ct;
 		ct.setup_internals();
 		ct.setup_stdcells();

 		for (auto &it : module->cells_) {
 			if (!ct.cell_known(it.second->type))
 				continue;
 			for (auto &it2 : it.second->connections())
 				if (ct.cell_output(it.second->type, it2.first))
 					sig2driver.insert(assign_map(it2.second), it.second);
 		}
 	}

 	void clear()
 	{
 		values_map.clear();
 		stop_signals.clear();
 	}

 	void push()
 	{
 		stack.push_back(values_map);
 	}

 	void pop()
 	{
 		values_map.swap(stack.back());
 		stack.pop_back();
 	}

 	void set(RTLIL::SigSpec sig, RTLIL::Const value)
 	{
 		assign_map.apply(sig);
 #ifndef NDEBUG
 		RTLIL::SigSpec current_val = values_map(sig);
 		for (int i = 0; i < GetSize(current_val); i++)
 			log_assert(current_val[i].wire != NULL || current_val[i] == value.bits[i]);
 #endif
 		values_map.add(sig, RTLIL::SigSpec(value));
 	}

 	void stop(RTLIL::SigSpec sig)
 	{
 		assign_map.apply(sig);
 		stop_signals.add(sig);
 	}

 	bool eval(RTLIL::Cell *cell, RTLIL::SigSpec &undef)
 	{
 		if (cell->type == "$lcu")
 		{
 			RTLIL::SigSpec sig_p = cell->getPort("\\P");
 			RTLIL::SigSpec sig_g = cell->getPort("\\G");
 			RTLIL::SigSpec sig_ci = cell->getPort("\\CI");
 			RTLIL::SigSpec sig_co = values_map(assign_map(cell->getPort("\\CO")));

 			if (sig_co.is_fully_const())
 				return true;

 			if (!eval(sig_p, undef, cell))
 				return false;

 			if (!eval(sig_g, undef, cell))
 				return false;

 			if (!eval(sig_ci, undef, cell))
 				return false;

 			if (sig_p.is_fully_def() && sig_g.is_fully_def() && sig_ci.is_fully_def())
 			{
 				RTLIL::Const coval(RTLIL::Sx, GetSize(sig_co));
 				bool carry = sig_ci.as_bool();

 				for (int i = 0; i < GetSize(coval); i++) {
 					carry = (sig_g[i] == RTLIL::S1) || (sig_p[i] == RTLIL::S1 && carry);
 					coval.bits[i] = carry ? RTLIL::S1 : RTLIL::S0;
 				}

 				set(sig_co, coval);
 			}
 			else
 				set(sig_co, RTLIL::Const(RTLIL::Sx, GetSize(sig_co)));

 			return true;
 		}

 		RTLIL::SigSpec sig_a, sig_b, sig_s, sig_y;

 		log_assert(cell->hasPort("\\Y"));
 		sig_y = values_map(assign_map(cell->getPort("\\Y")));
 		if (sig_y.is_fully_const())
 			return true;

 		if (cell->hasPort("\\S")) {
 			sig_s = cell->getPort("\\S");
 			if (!eval(sig_s, undef, cell))
 				return false;
 		}

 		if (cell->hasPort("\\A"))
 			sig_a = cell->getPort("\\A");

 		if (cell->hasPort("\\B"))
 			sig_b = cell->getPort("\\B");

 		if (cell->type == "$mux" || cell->type == "$pmux" || cell->type == "$_MUX_")
 		{
 			std::vector<RTLIL::SigSpec> y_candidates;
 			int count_maybe_set_s_bits = 0;
 			int count_set_s_bits = 0;

 			for (int i = 0; i < sig_s.size(); i++)
 			{
 				RTLIL::State s_bit = sig_s.extract(i, 1).as_const().bits.at(0);
 				RTLIL::SigSpec b_slice = sig_b.extract(sig_y.size()*i, sig_y.size());

 				if (s_bit == RTLIL::State::Sx || s_bit == RTLIL::State::S1)
 					y_candidates.push_back(b_slice);

 				if (s_bit == RTLIL::State::S1 || s_bit == RTLIL::State::Sx)
 					count_maybe_set_s_bits++;

 				if (s_bit == RTLIL::State::S1)
 					count_set_s_bits++;
 			}

 			if (count_set_s_bits == 0)
 				y_candidates.push_back(sig_a);

 			std::vector<RTLIL::Const> y_values;

 			log_assert(y_candidates.size() > 0);
 			for (auto &yc : y_candidates) {
 				if (!eval(yc, undef, cell))
 					return false;
 				y_values.push_back(yc.as_const());
 			}

 			if (y_values.size() > 1)
 			{
 				std::vector<RTLIL::State> master_bits = y_values.at(0).bits;

 				for (size_t i = 1; i < y_values.size(); i++) {
 					std::vector<RTLIL::State> &slave_bits = y_values.at(i).bits;
 					log_assert(master_bits.size() == slave_bits.size());
 					for (size_t j = 0; j < master_bits.size(); j++)
 						if (master_bits[j] != slave_bits[j])
 							master_bits[j] = RTLIL::State::Sx;
 				}

 				set(sig_y, RTLIL::Const(master_bits));
 			}
 			else
 				set(sig_y, y_values.front());
 		}
 		else if (cell->type == "$fa")
 		{
 			RTLIL::SigSpec sig_c = cell->getPort("\\C");
 			RTLIL::SigSpec sig_x = cell->getPort("\\X");
 			int width = GetSize(sig_c);

 			if (!eval(sig_a, undef, cell))
 				return false;

 			if (!eval(sig_b, undef, cell))
 				return false;

 			if (!eval(sig_c, undef, cell))
 				return false;

 			RTLIL::Const t1 = const_xor(sig_a.as_const(), sig_b.as_const(), false, false, width);
 			RTLIL::Const val_y = const_xor(t1, sig_c.as_const(), false, false, width);

 			RTLIL::Const t2 = const_and(sig_a.as_const(), sig_b.as_const(), false, false, width);
 			RTLIL::Const t3 = const_and(sig_c.as_const(), t1, false, false, width);
 			RTLIL::Const val_x = const_or(t2, t3, false, false, width);

 			for (int i = 0; i < GetSize(val_y); i++)
 				if (val_y.bits[i] == RTLIL::Sx)
 					val_x.bits[i] = RTLIL::Sx;

 			set(sig_y, val_y);
 			set(sig_x, val_x);
 		}
 		else if (cell->type == "$alu")
 		{
 			bool signed_a = cell->parameters.count("\\A_SIGNED") > 0 && cell->parameters["\\A_SIGNED"].as_bool();
 			bool signed_b = cell->parameters.count("\\B_SIGNED") > 0 && cell->parameters["\\B_SIGNED"].as_bool();

 			RTLIL::SigSpec sig_ci = cell->getPort("\\CI");
 			RTLIL::SigSpec sig_bi = cell->getPort("\\BI");

 			if (!eval(sig_a, undef, cell))
 				return false;

 			if (!eval(sig_b, undef, cell))
 				return false;

 			if (!eval(sig_ci, undef, cell))
 				return false;

 			if (!eval(sig_bi, undef, cell))
 				return false;

 			RTLIL::SigSpec sig_x = cell->getPort("\\X");
 			RTLIL::SigSpec sig_co = cell->getPort("\\CO");

 			bool any_input_undef = !(sig_a.is_fully_def() && sig_b.is_fully_def() && sig_ci.is_fully_def() && sig_bi.is_fully_def());
 			sig_a.extend_u0(GetSize(sig_y), signed_a);
 			sig_b.extend_u0(GetSize(sig_y), signed_b);

 			bool carry = sig_ci[0] == RTLIL::S1;
 			bool b_inv = sig_bi[0] == RTLIL::S1;

 			for (int i = 0; i < GetSize(sig_y); i++)
 			{
 				RTLIL::SigSpec x_inputs = { sig_a[i], sig_b[i], sig_bi[0] };

 				if (!x_inputs.is_fully_def()) {
 					set(sig_x[i], RTLIL::Sx);
 				} else {
 					bool bit_a = sig_a[i] == RTLIL::S1;
 					bool bit_b = (sig_b[i] == RTLIL::S1) != b_inv;
 					bool bit_x = bit_a != bit_b;
 					set(sig_x[i], bit_x ? RTLIL::S1 : RTLIL::S0);
 				}

 				if (any_input_undef) {
 					set(sig_y[i], RTLIL::Sx);
 					set(sig_co[i], RTLIL::Sx);
 				} else {
 					bool bit_a = sig_a[i] == RTLIL::S1;
 					bool bit_b = (sig_b[i] == RTLIL::S1) != b_inv;
 					bool bit_y = (bit_a != bit_b) != carry;
 					carry = (bit_a && bit_b) || (bit_a && carry) || (bit_b && carry);
 					set(sig_y[i], bit_y ? RTLIL::S1 : RTLIL::S0);
 					set(sig_co[i], carry ? RTLIL::S1 : RTLIL::S0);
 				}
 			}
 		}
 		else if (cell->type == "$macc")
 		{
 			Macc macc;
 			macc.from_cell(cell);

 			if (!eval(macc.bit_ports, undef, cell))
 				return false;

 			for (auto &port : macc.ports) {
 				if (!eval(port.in_a, undef, cell))
 					return false;
 				if (!eval(port.in_b, undef, cell))
 					return false;
 			}

 			RTLIL::Const result(0, GetSize(cell->getPort("\\Y")));
 			if (!macc.eval(result))
 				log_abort();

 			set(cell->getPort("\\Y"), result);
 		}
 		else
 		{
 			RTLIL::SigSpec sig_c, sig_d;

 			if (cell->type.in("$_AOI3_", "$_OAI3_", "$_AOI4_", "$_OAI4_")) {
 				if (cell->hasPort("\\C"))
 					sig_c = cell->getPort("\\C");
 				if (cell->hasPort("\\D"))
 					sig_d = cell->getPort("\\D");
 			}

 			if (sig_a.size() > 0 && !eval(sig_a, undef, cell))
 				return false;
 			if (sig_b.size() > 0 && !eval(sig_b, undef, cell))
 				return false;
 			if (sig_c.size() > 0 && !eval(sig_c, undef, cell))
 				return false;
 			if (sig_d.size() > 0 && !eval(sig_d, undef, cell))
 				return false;

 			bool eval_err = false;
 			RTLIL::Const eval_ret = CellTypes::eval(cell, sig_a.as_const(), sig_b.as_const(), sig_c.as_const(), sig_d.as_const(), &eval_err);

 			if (eval_err)
 				return false;

 			set(sig_y, eval_ret);
 		}

 		return true;
 	}

 	bool eval(RTLIL::SigSpec &sig, RTLIL::SigSpec &undef, RTLIL::Cell *busy_cell = NULL)
 	{
 		assign_map.apply(sig);
 		values_map.apply(sig);

 		if (sig.is_fully_const())
 			return true;

 		if (stop_signals.check_any(sig)) {
 			undef = stop_signals.extract(sig);
 			return false;
 		}

 		if (busy_cell) {
 			if (busy.count(busy_cell) > 0) {
 				undef = sig;
 				return false;
 			}
 			busy.insert(busy_cell);
 		}

 		std::set<RTLIL::Cell*> driver_cells;
 		sig2driver.find(sig, driver_cells);
 		for (auto cell : driver_cells) {
 			if (!eval(cell, undef)) {
 				if (busy_cell)
 					busy.erase(busy_cell);
 				return false;
 			}
 		}

 		if (busy_cell)
 			busy.erase(busy_cell);

 		values_map.apply(sig);
 		if (sig.is_fully_const())
 			return true;

 		if (defaultval != RTLIL::State::Sm) {
 			for (auto &bit : sig)
 				if (bit.wire) bit = defaultval;
 			return true;
 		}

 		for (auto &c : sig.chunks())
 			if (c.wire != NULL)
 				undef.append(c);
 		return false;
 	}

 	bool eval(RTLIL::SigSpec &sig)
 	{
 		RTLIL::SigSpec undef;
 		return eval(sig, undef);
 	}
 };

 YOSYS_NAMESPACE_END

 #endif
	/*
	* yosys -- Yosys Open SYnthesis Suite
	*
	* Copyright (C) 2012 Clifford Wolf <clifford@clifford.at>
	*
	* 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.
	*
	*/

	#ifndef CONSTEVAL_H
	#define CONSTEVAL_H

	#include "kernel/rtlil.h"
	#include "kernel/sigtools.h"
	#include "kernel/celltypes.h"
	#include "kernel/macc.h"

	YOSYS_NAMESPACE_BEGIN

	struct ConstEval
	{
	RTLIL::Module *module;
	SigMap assign_map;
	SigMap values_map;
	SigPool stop_signals;
	SigSet<RTLIL::Cell*> sig2driver;
	std::set<RTLIL::Cell*> busy;
	std::vector<SigMap> stack;
	RTLIL::State defaultval;

	ConstEval(RTLIL::Module *module, RTLIL::State defaultval = RTLIL::State::Sm) : module(module), assign_map(module), defaultval(defaultval)
	{
	CellTypes ct;
	ct.setup_internals();
	ct.setup_stdcells();

	for (auto &it : module->cells_) {
	if (!ct.cell_known(it.second->type))
	continue;
	for (auto &it2 : it.second->connections())
	if (ct.cell_output(it.second->type, it2.first))
	sig2driver.insert(assign_map(it2.second), it.second);
	}
	}

	void clear()
	{
	values_map.clear();
	stop_signals.clear();
	}

	void push()
	{
	stack.push_back(values_map);
	}

	void pop()
	{
	values_map.swap(stack.back());
	stack.pop_back();
	}

	void set(RTLIL::SigSpec sig, RTLIL::Const value)
	{
	assign_map.apply(sig);
	#ifndef NDEBUG
	RTLIL::SigSpec current_val = values_map(sig);
	for (int i = 0; i < GetSize(current_val); i++)
	log_assert(current_val[i].wire != NULL \|\| current_val[i] == value.bits[i]);
	#endif
	values_map.add(sig, RTLIL::SigSpec(value));
	}

	void stop(RTLIL::SigSpec sig)
	{
	assign_map.apply(sig);
	stop_signals.add(sig);
	}

	bool eval(RTLIL::Cell *cell, RTLIL::SigSpec &undef)
	{
	if (cell->type == "$lcu")
	{
	RTLIL::SigSpec sig_p = cell->getPort("\\P");
	RTLIL::SigSpec sig_g = cell->getPort("\\G");
	RTLIL::SigSpec sig_ci = cell->getPort("\\CI");
	RTLIL::SigSpec sig_co = values_map(assign_map(cell->getPort("\\CO")));

	if (sig_co.is_fully_const())
	return true;

	if (!eval(sig_p, undef, cell))
	return false;

	if (!eval(sig_g, undef, cell))
	return false;

	if (!eval(sig_ci, undef, cell))
	return false;

	if (sig_p.is_fully_def() && sig_g.is_fully_def() && sig_ci.is_fully_def())
	{
	RTLIL::Const coval(RTLIL::Sx, GetSize(sig_co));
	bool carry = sig_ci.as_bool();

	for (int i = 0; i < GetSize(coval); i++) {
	carry = (sig_g[i] == RTLIL::S1) \|\| (sig_p[i] == RTLIL::S1 && carry);
	coval.bits[i] = carry ? RTLIL::S1 : RTLIL::S0;
	}

	set(sig_co, coval);
	}
	else
	set(sig_co, RTLIL::Const(RTLIL::Sx, GetSize(sig_co)));

	return true;
	}

	RTLIL::SigSpec sig_a, sig_b, sig_s, sig_y;

	log_assert(cell->hasPort("\\Y"));
	sig_y = values_map(assign_map(cell->getPort("\\Y")));
	if (sig_y.is_fully_const())
	return true;

	if (cell->hasPort("\\S")) {
	sig_s = cell->getPort("\\S");
	if (!eval(sig_s, undef, cell))
	return false;
	}

	if (cell->hasPort("\\A"))
	sig_a = cell->getPort("\\A");

	if (cell->hasPort("\\B"))
	sig_b = cell->getPort("\\B");

	if (cell->type == "$mux" \|\| cell->type == "$pmux" \|\| cell->type == "$_MUX_")
	{
	std::vector<RTLIL::SigSpec> y_candidates;
	int count_maybe_set_s_bits = 0;
	int count_set_s_bits = 0;

	for (int i = 0; i < sig_s.size(); i++)
	{
	RTLIL::State s_bit = sig_s.extract(i, 1).as_const().bits.at(0);
	RTLIL::SigSpec b_slice = sig_b.extract(sig_y.size()*i, sig_y.size());

	if (s_bit == RTLIL::State::Sx \|\| s_bit == RTLIL::State::S1)
	y_candidates.push_back(b_slice);

	if (s_bit == RTLIL::State::S1 \|\| s_bit == RTLIL::State::Sx)
	count_maybe_set_s_bits++;

	if (s_bit == RTLIL::State::S1)
	count_set_s_bits++;
	}

	if (count_set_s_bits == 0)
	y_candidates.push_back(sig_a);

	std::vector<RTLIL::Const> y_values;

	log_assert(y_candidates.size() > 0);
	for (auto &yc : y_candidates) {
	if (!eval(yc, undef, cell))
	return false;
	y_values.push_back(yc.as_const());
	}

	if (y_values.size() > 1)
	{
	std::vector<RTLIL::State> master_bits = y_values.at(0).bits;

	for (size_t i = 1; i < y_values.size(); i++) {
	std::vector<RTLIL::State> &slave_bits = y_values.at(i).bits;
	log_assert(master_bits.size() == slave_bits.size());
	for (size_t j = 0; j < master_bits.size(); j++)
	if (master_bits[j] != slave_bits[j])
	master_bits[j] = RTLIL::State::Sx;
	}

	set(sig_y, RTLIL::Const(master_bits));
	}
	else
	set(sig_y, y_values.front());
	}
	else if (cell->type == "$fa")
	{
	RTLIL::SigSpec sig_c = cell->getPort("\\C");
	RTLIL::SigSpec sig_x = cell->getPort("\\X");
	int width = GetSize(sig_c);

	if (!eval(sig_a, undef, cell))
	return false;

	if (!eval(sig_b, undef, cell))
	return false;

	if (!eval(sig_c, undef, cell))
	return false;

	RTLIL::Const t1 = const_xor(sig_a.as_const(), sig_b.as_const(), false, false, width);
	RTLIL::Const val_y = const_xor(t1, sig_c.as_const(), false, false, width);

	RTLIL::Const t2 = const_and(sig_a.as_const(), sig_b.as_const(), false, false, width);
	RTLIL::Const t3 = const_and(sig_c.as_const(), t1, false, false, width);
	RTLIL::Const val_x = const_or(t2, t3, false, false, width);

	for (int i = 0; i < GetSize(val_y); i++)
	if (val_y.bits[i] == RTLIL::Sx)
	val_x.bits[i] = RTLIL::Sx;

	set(sig_y, val_y);
	set(sig_x, val_x);
	}
	else if (cell->type == "$alu")
	{
	bool signed_a = cell->parameters.count("\\A_SIGNED") > 0 && cell->parameters["\\A_SIGNED"].as_bool();
	bool signed_b = cell->parameters.count("\\B_SIGNED") > 0 && cell->parameters["\\B_SIGNED"].as_bool();

	RTLIL::SigSpec sig_ci = cell->getPort("\\CI");
	RTLIL::SigSpec sig_bi = cell->getPort("\\BI");

	if (!eval(sig_a, undef, cell))
	return false;

	if (!eval(sig_b, undef, cell))
	return false;

	if (!eval(sig_ci, undef, cell))
	return false;

	if (!eval(sig_bi, undef, cell))
	return false;

	RTLIL::SigSpec sig_x = cell->getPort("\\X");
	RTLIL::SigSpec sig_co = cell->getPort("\\CO");

	bool any_input_undef = !(sig_a.is_fully_def() && sig_b.is_fully_def() && sig_ci.is_fully_def() && sig_bi.is_fully_def());
	sig_a.extend_u0(GetSize(sig_y), signed_a);
	sig_b.extend_u0(GetSize(sig_y), signed_b);

	bool carry = sig_ci[0] == RTLIL::S1;
	bool b_inv = sig_bi[0] == RTLIL::S1;

	for (int i = 0; i < GetSize(sig_y); i++)
	{
	RTLIL::SigSpec x_inputs = { sig_a[i], sig_b[i], sig_bi[0] };

	if (!x_inputs.is_fully_def()) {
	set(sig_x[i], RTLIL::Sx);
	} else {
	bool bit_a = sig_a[i] == RTLIL::S1;
	bool bit_b = (sig_b[i] == RTLIL::S1) != b_inv;
	bool bit_x = bit_a != bit_b;
	set(sig_x[i], bit_x ? RTLIL::S1 : RTLIL::S0);
	}

	if (any_input_undef) {
	set(sig_y[i], RTLIL::Sx);
	set(sig_co[i], RTLIL::Sx);
	} else {
	bool bit_a = sig_a[i] == RTLIL::S1;
	bool bit_b = (sig_b[i] == RTLIL::S1) != b_inv;
	bool bit_y = (bit_a != bit_b) != carry;
	carry = (bit_a && bit_b) \|\| (bit_a && carry) \|\| (bit_b && carry);
	set(sig_y[i], bit_y ? RTLIL::S1 : RTLIL::S0);
	set(sig_co[i], carry ? RTLIL::S1 : RTLIL::S0);
	}
	}
	}
	else if (cell->type == "$macc")
	{
	Macc macc;
	macc.from_cell(cell);

	if (!eval(macc.bit_ports, undef, cell))
	return false;

	for (auto &port : macc.ports) {
	if (!eval(port.in_a, undef, cell))
	return false;
	if (!eval(port.in_b, undef, cell))
	return false;
	}

	RTLIL::Const result(0, GetSize(cell->getPort("\\Y")));
	if (!macc.eval(result))
	log_abort();

	set(cell->getPort("\\Y"), result);
	}
	else
	{
	RTLIL::SigSpec sig_c, sig_d;

	if (cell->type.in("$_AOI3_", "$_OAI3_", "$_AOI4_", "$_OAI4_")) {
	if (cell->hasPort("\\C"))
	sig_c = cell->getPort("\\C");
	if (cell->hasPort("\\D"))
	sig_d = cell->getPort("\\D");
	}

	if (sig_a.size() > 0 && !eval(sig_a, undef, cell))
	return false;
	if (sig_b.size() > 0 && !eval(sig_b, undef, cell))
	return false;
	if (sig_c.size() > 0 && !eval(sig_c, undef, cell))
	return false;
	if (sig_d.size() > 0 && !eval(sig_d, undef, cell))
	return false;

	bool eval_err = false;
	RTLIL::Const eval_ret = CellTypes::eval(cell, sig_a.as_const(), sig_b.as_const(), sig_c.as_const(), sig_d.as_const(), &eval_err);

	if (eval_err)
	return false;

	set(sig_y, eval_ret);
	}

	return true;
	}

	bool eval(RTLIL::SigSpec &sig, RTLIL::SigSpec &undef, RTLIL::Cell *busy_cell = NULL)
	{
	assign_map.apply(sig);
	values_map.apply(sig);

	if (sig.is_fully_const())
	return true;

	if (stop_signals.check_any(sig)) {
	undef = stop_signals.extract(sig);
	return false;
	}

	if (busy_cell) {
	if (busy.count(busy_cell) > 0) {
	undef = sig;
	return false;
	}
	busy.insert(busy_cell);
	}

	std::set<RTLIL::Cell*> driver_cells;
	sig2driver.find(sig, driver_cells);
	for (auto cell : driver_cells) {
	if (!eval(cell, undef)) {
	if (busy_cell)
	busy.erase(busy_cell);
	return false;
	}
	}

	if (busy_cell)
	busy.erase(busy_cell);

	values_map.apply(sig);
	if (sig.is_fully_const())
	return true;

	if (defaultval != RTLIL::State::Sm) {
	for (auto &bit : sig)
	if (bit.wire) bit = defaultval;
	return true;
	}

	for (auto &c : sig.chunks())
	if (c.wire != NULL)
	undef.append(c);
	return false;
	}

	bool eval(RTLIL::SigSpec &sig)
	{
	RTLIL::SigSpec undef;
	return eval(sig, undef);
	}
	};

	YOSYS_NAMESPACE_END

	#endif