yosys/backends/btor/btor.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.
 *
 */

// [[CITE]] Btor2 , BtorMC and Boolector 3.0
// Aina Niemetz, Mathias Preiner, C. Wolf, Armin Biere
// Computer Aided Verification - 30th International Conference, CAV 2018
// https://cs.stanford.edu/people/niemetz/publication/2018/niemetzpreinerwolfbiere-cav18/

#include "kernel/rtlil.h"
#include "kernel/register.h"
#include "kernel/sigtools.h"
#include "kernel/celltypes.h"
#include "kernel/log.h"
#include "kernel/mem.h"
#include "kernel/json.h"
#include "kernel/yw.h"
#include <string>

USING_YOSYS_NAMESPACE
PRIVATE_NAMESPACE_BEGIN

struct BtorWorker
{
	std::ostream &f;
	SigMap sigmap;
	RTLIL::Module *module;
	bool verbose;
	bool single_bad;
	bool cover_mode;
	bool print_internal_names;

	int next_nid = 1;
	int initstate_nid = -1;

	// <width> => <sid>
	dict<int, int> sorts_bv;

	// (<address-width>, <data-width>) => <sid>
	dict<pair<int, int>, int> sorts_mem;

	// SigBit => (<nid>, <bitidx>)
	dict<SigBit, pair<int, int>> bit_nid;

	// <nid> => <bvwidth>
	dict<int, int> nid_width;

	// SigSpec => <nid>
	dict<SigSpec, int> sig_nid;

	// bit to driving cell
	dict<SigBit, Cell*> bit_cell;

	// nids for constants
	dict<Const, int> consts;

	// ff inputs that need to be evaluated (<nid>, <ff_cell>)
	vector<pair<int, Cell*>> ff_todo;
	vector<pair<int, Mem*>> mem_todo;

	pool<Cell*> cell_recursion_guard;
	vector<int> bad_properties;
	dict<SigBit, bool> initbits;
	pool<Wire*> statewires;
	pool<string> srcsymbols;
	vector<Mem> memories;
	dict<Cell*, Mem*> mem_cells;

	string indent, info_filename;
	vector<string> info_lines;
	dict<int, int> info_clocks;

	struct ywmap_btor_sig {
		SigSpec sig;
		Cell *cell = nullptr;

		ywmap_btor_sig(const SigSpec &sig) : sig(sig) {}
		ywmap_btor_sig(Cell *cell) : cell(cell) {}
	};

	vector<ywmap_btor_sig> ywmap_inputs;
	vector<ywmap_btor_sig> ywmap_states;
	dict<SigBit, int> ywmap_clock_bits;
	dict<SigBit, int> ywmap_clock_inputs;


	PrettyJson ywmap_json;

	void btorf(const char *fmt, ...) YS_ATTRIBUTE(format(printf, 2, 3))
	{
		va_list ap;
		va_start(ap, fmt);
		f << indent << vstringf(fmt, ap);
		va_end(ap);
	}

	void infof(const char *fmt, ...) YS_ATTRIBUTE(format(printf, 2, 3))
	{
		va_list ap;
		va_start(ap, fmt);
		info_lines.push_back(vstringf(fmt, ap));
		va_end(ap);
	}

	template<typename T>
	string getinfo(T *obj, bool srcsym = false)
	{
		string infostr = log_id(obj);
		if (!srcsym && !print_internal_names && infostr[0] == '$') return "";
		if (obj->attributes.count(ID::src)) {
			string src = obj->attributes.at(ID::src).decode_string().c_str();
			if (srcsym && infostr[0] == '$') {
				std::replace(src.begin(), src.end(), ' ', '_');
				if (srcsymbols.count(src) || module->count_id("\\" + src)) {
					for (int i = 1;; i++) {
						string s = stringf("%s-%d", src.c_str(), i);
						if (!srcsymbols.count(s) && !module->count_id("\\" + s)) {
							src = s;
							break;
						}
					}
				}
				srcsymbols.insert(src);
				infostr = src;
			} else {
				infostr += " ; " + src;
			}
		}
		return " " + infostr;
	}

	void ywmap_state(const SigSpec &sig) {
		if (ywmap_json.active())
			ywmap_states.emplace_back(sig);
	}

	void ywmap_state(Cell *cell) {
		if (ywmap_json.active())
			ywmap_states.emplace_back(cell);
	}

	void ywmap_input(const SigSpec &sig) {
		if (ywmap_json.active())
			ywmap_inputs.emplace_back(sig);
	}

	void emit_ywmap_btor_sig(const ywmap_btor_sig &btor_sig) {
		if (btor_sig.cell == nullptr) {
			if (btor_sig.sig.empty()) {
				ywmap_json.value(nullptr);
				return;
			}
			ywmap_json.begin_array();
			ywmap_json.compact();
			for (auto &chunk : btor_sig.sig.chunks()) {
				log_assert(chunk.is_wire());

				ywmap_json.begin_object();
				ywmap_json.entry("path", witness_path(chunk.wire));
				ywmap_json.entry("width", chunk.width);
				ywmap_json.entry("offset", chunk.offset);
				ywmap_json.end_object();
			}
			ywmap_json.end_array();
		} else {
			ywmap_json.begin_object();
			ywmap_json.compact();
			ywmap_json.entry("path", witness_path(btor_sig.cell));
			Mem *mem = mem_cells[btor_sig.cell];
			ywmap_json.entry("width", mem->width);
			ywmap_json.entry("size", mem->size);
			ywmap_json.end_object();
		}
	}

	void btorf_push(const string &id)
	{
		if (verbose) {
			f << indent << stringf("  ; begin %s\n", id.c_str());
			indent += "    ";
		}
	}

	void btorf_pop(const string &id)
	{
		if (verbose) {
			indent = indent.substr(4);
			f << indent << stringf("  ; end %s\n", id.c_str());
		}
	}

	int get_bv_sid(int width)
	{
		if (sorts_bv.count(width) == 0) {
			int nid = next_nid++;
			btorf("%d sort bitvec %d\n", nid, width);
			sorts_bv[width] = nid;
		}
		return sorts_bv.at(width);
	}

	int get_mem_sid(int abits, int dbits)
	{
		pair<int, int> key(abits, dbits);
		if (sorts_mem.count(key) == 0) {
			int addr_sid = get_bv_sid(abits);
			int data_sid = get_bv_sid(dbits);
			int nid = next_nid++;
			btorf("%d sort array %d %d\n", nid, addr_sid, data_sid);
			sorts_mem[key] = nid;
		}
		return sorts_mem.at(key);
	}

	void add_nid_sig(int nid, const SigSpec &sig)
	{
		if (verbose)
			f << indent << stringf("; %d %s\n", nid, log_signal(sig));

		for (int i = 0; i < GetSize(sig); i++)
			bit_nid[sig[i]] = make_pair(nid, i);

		sig_nid[sig] = nid;
		nid_width[nid] = GetSize(sig);
	}

	void export_cell(Cell *cell)
	{
		if (cell_recursion_guard.count(cell)) {
			string cell_list;
			for (auto c : cell_recursion_guard)
				cell_list += stringf("\n    %s", log_id(c));
			log_error("Found topological loop while processing cell %s. Active cells:%s\n", log_id(cell), cell_list.c_str());
		}

		cell_recursion_guard.insert(cell);
		btorf_push(log_id(cell));

		if (cell->type.in(ID($add), ID($sub), ID($mul), ID($and), ID($or), ID($xor), ID($xnor), ID($shl), ID($sshl), ID($shr), ID($sshr), ID($shift), ID($shiftx),
				ID($concat), ID($_AND_), ID($_NAND_), ID($_OR_), ID($_NOR_), ID($_XOR_), ID($_XNOR_)))
		{
			string btor_op;
			if (cell->type == ID($add)) btor_op = "add";
			if (cell->type == ID($sub)) btor_op = "sub";
			if (cell->type == ID($mul)) btor_op = "mul";
			if (cell->type.in(ID($shl), ID($sshl))) btor_op = "sll";
			if (cell->type == ID($shr)) btor_op = "srl";
			if (cell->type == ID($sshr)) btor_op = "sra";
			if (cell->type.in(ID($shift), ID($shiftx))) btor_op = "shift";
			if (cell->type.in(ID($and), ID($_AND_))) btor_op = "and";
			if (cell->type.in(ID($or), ID($_OR_))) btor_op = "or";
			if (cell->type.in(ID($xor), ID($_XOR_))) btor_op = "xor";
			if (cell->type == ID($concat)) btor_op = "concat";
			if (cell->type == ID($_NAND_)) btor_op = "nand";
			if (cell->type == ID($_NOR_)) btor_op = "nor";
			if (cell->type.in(ID($xnor), ID($_XNOR_))) btor_op = "xnor";
			log_assert(!btor_op.empty());

			int width_ay = std::max(GetSize(cell->getPort(ID::A)), GetSize(cell->getPort(ID::Y)));
			int width = std::max(width_ay, GetSize(cell->getPort(ID::B)));

			bool a_signed = cell->hasParam(ID::A_SIGNED) ? cell->getParam(ID::A_SIGNED).as_bool() : false;
			bool b_signed = cell->hasParam(ID::B_SIGNED) ? cell->getParam(ID::B_SIGNED).as_bool() : false;

			if (btor_op == "shift" && !b_signed)
				btor_op = "srl";

			if (cell->type.in(ID($shl), ID($sshl), ID($shr), ID($sshr)))
				b_signed = false;

			if (cell->type == ID($sshr) && !a_signed)
				btor_op = "srl";

			int sid = get_bv_sid(width);
			int nid;

			int nid_a;
			if (cell->type.in(ID($shl), ID($shr), ID($shift), ID($shiftx)) && a_signed && width_ay < width) {
				// sign-extend A up to the width of Y
				int nid_a_padded = get_sig_nid(cell->getPort(ID::A), width_ay, a_signed);

				// zero-extend the rest
				int zeroes = get_sig_nid(Const(0, width-width_ay));
				nid_a = next_nid++;
				btorf("%d concat %d %d %d\n", nid_a, sid, zeroes, nid_a_padded);
			} else {
				nid_a = get_sig_nid(cell->getPort(ID::A), width, a_signed);
			}

			int nid_b = get_sig_nid(cell->getPort(ID::B), width, b_signed);

			if (btor_op == "shift")
			{
				int nid_r = next_nid++;
				btorf("%d srl %d %d %d\n", nid_r, sid, nid_a, nid_b);

				int nid_b_neg = next_nid++;
				btorf("%d neg %d %d\n", nid_b_neg, sid, nid_b);

				int nid_l = next_nid++;
				btorf("%d sll %d %d %d\n", nid_l, sid, nid_a, nid_b_neg);

				int sid_bit = get_bv_sid(1);
				int nid_zero = get_sig_nid(Const(0, width));
				int nid_b_ltz = next_nid++;
				btorf("%d slt %d %d %d\n", nid_b_ltz, sid_bit, nid_b, nid_zero);

				nid = next_nid++;
				btorf("%d ite %d %d %d %d%s\n", nid, sid, nid_b_ltz, nid_l, nid_r, getinfo(cell).c_str());
			}
			else
			{
				nid = next_nid++;
				btorf("%d %s %d %d %d%s\n", nid, btor_op.c_str(), sid, nid_a, nid_b, getinfo(cell).c_str());
			}

			SigSpec sig = sigmap(cell->getPort(ID::Y));

			if (GetSize(sig) < width) {
				int sid = get_bv_sid(GetSize(sig));
				int nid2 = next_nid++;
				btorf("%d slice %d %d %d 0\n", nid2, sid, nid, GetSize(sig)-1);
				nid = nid2;
			}

			add_nid_sig(nid, sig);
			goto okay;
		}

		if (cell->type.in(ID($div), ID($mod), ID($modfloor)))
		{
			bool a_signed = cell->hasParam(ID::A_SIGNED) ? cell->getParam(ID::A_SIGNED).as_bool() : false;
			bool b_signed = cell->hasParam(ID::B_SIGNED) ? cell->getParam(ID::B_SIGNED).as_bool() : false;

			string btor_op;
			if (cell->type == ID($div)) btor_op = "div";
			// "rem" = truncating modulo
			if (cell->type == ID($mod)) btor_op = "rem";
			// "mod" = flooring modulo
			if (cell->type == ID($modfloor)) {
				// "umod" doesn't exist because it's the same as "urem"
				btor_op = a_signed || b_signed ? "mod" : "rem";
			}
			log_assert(!btor_op.empty());

			int width = GetSize(cell->getPort(ID::Y));
			width = std::max(width, GetSize(cell->getPort(ID::A)));
			width = std::max(width, GetSize(cell->getPort(ID::B)));

			int nid_a = get_sig_nid(cell->getPort(ID::A), width, a_signed);
			int nid_b = get_sig_nid(cell->getPort(ID::B), width, b_signed);

			int sid = get_bv_sid(width);
			int nid = next_nid++;
			btorf("%d %c%s %d %d %d%s\n", nid, a_signed || b_signed ? 's' : 'u', btor_op.c_str(), sid, nid_a, nid_b, getinfo(cell).c_str());

			SigSpec sig = sigmap(cell->getPort(ID::Y));

			if (GetSize(sig) < width) {
				int sid = get_bv_sid(GetSize(sig));
				int nid2 = next_nid++;
				btorf("%d slice %d %d %d 0\n", nid2, sid, nid, GetSize(sig)-1);
				nid = nid2;
			}

			add_nid_sig(nid, sig);
			goto okay;
		}

		if (cell->type.in(ID($_ANDNOT_), ID($_ORNOT_)))
		{
			int sid = get_bv_sid(1);
			int nid_a = get_sig_nid(cell->getPort(ID::A));
			int nid_b = get_sig_nid(cell->getPort(ID::B));

			int nid1 = next_nid++;
			int nid2 = next_nid++;

			if (cell->type == ID($_ANDNOT_)) {
				btorf("%d not %d %d\n", nid1, sid, nid_b);
				btorf("%d and %d %d %d%s\n", nid2, sid, nid_a, nid1, getinfo(cell).c_str());
			}

			if (cell->type == ID($_ORNOT_)) {
				btorf("%d not %d %d\n", nid1, sid, nid_b);
				btorf("%d or %d %d %d%s\n", nid2, sid, nid_a, nid1, getinfo(cell).c_str());
			}

			SigSpec sig = sigmap(cell->getPort(ID::Y));
			add_nid_sig(nid2, sig);
			goto okay;
		}

		if (cell->type.in(ID($_OAI3_), ID($_AOI3_)))
		{
			int sid = get_bv_sid(1);
			int nid_a = get_sig_nid(cell->getPort(ID::A));
			int nid_b = get_sig_nid(cell->getPort(ID::B));
			int nid_c = get_sig_nid(cell->getPort(ID::C));

			int nid1 = next_nid++;
			int nid2 = next_nid++;
			int nid3 = next_nid++;

			if (cell->type == ID($_OAI3_)) {
				btorf("%d or %d %d %d\n", nid1, sid, nid_a, nid_b);
				btorf("%d and %d %d %d\n", nid2, sid, nid1, nid_c);
				btorf("%d not %d %d%s\n", nid3, sid, nid2, getinfo(cell).c_str());
			}

			if (cell->type == ID($_AOI3_)) {
				btorf("%d and %d %d %d\n", nid1, sid, nid_a, nid_b);
				btorf("%d or %d %d %d\n", nid2, sid, nid1, nid_c);
				btorf("%d not %d %d%s\n", nid3, sid, nid2, getinfo(cell).c_str());
			}

			SigSpec sig = sigmap(cell->getPort(ID::Y));
			add_nid_sig(nid3, sig);
			goto okay;
		}

		if (cell->type.in(ID($_OAI4_), ID($_AOI4_)))
		{
			int sid = get_bv_sid(1);
			int nid_a = get_sig_nid(cell->getPort(ID::A));
			int nid_b = get_sig_nid(cell->getPort(ID::B));
			int nid_c = get_sig_nid(cell->getPort(ID::C));
			int nid_d = get_sig_nid(cell->getPort(ID::D));

			int nid1 = next_nid++;
			int nid2 = next_nid++;
			int nid3 = next_nid++;
			int nid4 = next_nid++;

			if (cell->type == ID($_OAI4_)) {
				btorf("%d or %d %d %d\n", nid1, sid, nid_a, nid_b);
				btorf("%d or %d %d %d\n", nid2, sid, nid_c, nid_d);
				btorf("%d and %d %d %d\n", nid3, sid, nid1, nid2);
				btorf("%d not %d %d%s\n", nid4, sid, nid3, getinfo(cell).c_str());
			}

			if (cell->type == ID($_AOI4_)) {
				btorf("%d and %d %d %d\n", nid1, sid, nid_a, nid_b);
				btorf("%d and %d %d %d\n", nid2, sid, nid_c, nid_d);
				btorf("%d or %d %d %d\n", nid3, sid, nid1, nid2);
				btorf("%d not %d %d%s\n", nid4, sid, nid3, getinfo(cell).c_str());
			}

			SigSpec sig = sigmap(cell->getPort(ID::Y));
			add_nid_sig(nid4, sig);
			goto okay;
		}

		if (cell->type.in(ID($lt), ID($le), ID($eq), ID($eqx), ID($ne), ID($nex), ID($ge), ID($gt)))
		{
			string btor_op;
			if (cell->type == ID($lt)) btor_op = "lt";
			if (cell->type == ID($le)) btor_op = "lte";
			if (cell->type.in(ID($eq), ID($eqx))) btor_op = "eq";
			if (cell->type.in(ID($ne), ID($nex))) btor_op = "neq";
			if (cell->type == ID($ge)) btor_op = "gte";
			if (cell->type == ID($gt)) btor_op = "gt";
			log_assert(!btor_op.empty());

			int width = 1;
			width = std::max(width, GetSize(cell->getPort(ID::A)));
			width = std::max(width, GetSize(cell->getPort(ID::B)));

			bool a_signed = cell->hasParam(ID::A_SIGNED) ? cell->getParam(ID::A_SIGNED).as_bool() : false;
			bool b_signed = cell->hasParam(ID::B_SIGNED) ? cell->getParam(ID::B_SIGNED).as_bool() : false;

			int sid = get_bv_sid(1);
			int nid_a = get_sig_nid(cell->getPort(ID::A), width, a_signed);
			int nid_b = get_sig_nid(cell->getPort(ID::B), width, b_signed);

			int nid = next_nid++;
			if (cell->type.in(ID($lt), ID($le), ID($ge), ID($gt))) {
				btorf("%d %c%s %d %d %d%s\n", nid, a_signed || b_signed ? 's' : 'u', btor_op.c_str(), sid, nid_a, nid_b, getinfo(cell).c_str());
			} else {
				btorf("%d %s %d %d %d%s\n", nid, btor_op.c_str(), sid, nid_a, nid_b, getinfo(cell).c_str());
			}

			SigSpec sig = sigmap(cell->getPort(ID::Y));

			if (GetSize(sig) > 1) {
				int sid = get_bv_sid(GetSize(sig));
				int nid2 = next_nid++;
				btorf("%d uext %d %d %d\n", nid2, sid, nid, GetSize(sig) - 1);
				nid = nid2;
			}

			add_nid_sig(nid, sig);
			goto okay;
		}

		if (cell->type.in(ID($not), ID($neg), ID($_NOT_), ID($pos)))
		{
			string btor_op;
			if (cell->type.in(ID($not), ID($_NOT_))) btor_op = "not";
			if (cell->type == ID($neg)) btor_op = "neg";

			int width = std::max(GetSize(cell->getPort(ID::A)), GetSize(cell->getPort(ID::Y)));

			bool a_signed = cell->hasParam(ID::A_SIGNED) ? cell->getParam(ID::A_SIGNED).as_bool() : false;
			int nid_a = get_sig_nid(cell->getPort(ID::A), width, a_signed);
			SigSpec sig = sigmap(cell->getPort(ID::Y));

			// the $pos cell just passes through, all other cells need an actual operation applied
			int nid = nid_a;
			if (cell->type != ID($pos))
			{
				log_assert(!btor_op.empty());
				int sid = get_bv_sid(width);
				nid = next_nid++;
				btorf("%d %s %d %d%s\n", nid, btor_op.c_str(), sid, nid_a, getinfo(cell).c_str());
			}

			if (GetSize(sig) < width) {
				int sid = get_bv_sid(GetSize(sig));
				int nid2 = next_nid++;
				btorf("%d slice %d %d %d 0\n", nid2, sid, nid, GetSize(sig)-1);
				nid = nid2;
			}

			add_nid_sig(nid, sig);
			goto okay;
		}

		if (cell->type.in(ID($logic_and), ID($logic_or), ID($logic_not)))
		{
			string btor_op;
			if (cell->type == ID($logic_and)) btor_op = "and";
			if (cell->type == ID($logic_or))  btor_op = "or";
			if (cell->type == ID($logic_not)) btor_op = "not";
			log_assert(!btor_op.empty());

			int sid = get_bv_sid(1);
			int nid_a = get_sig_nid(cell->getPort(ID::A));
			int nid_b = btor_op != "not" ? get_sig_nid(cell->getPort(ID::B)) : 0;

			if (GetSize(cell->getPort(ID::A)) > 1) {
				int nid_red_a = next_nid++;
				btorf("%d redor %d %d\n", nid_red_a, sid, nid_a);
				nid_a = nid_red_a;
			}

			if (btor_op != "not" && GetSize(cell->getPort(ID::B)) > 1) {
				int nid_red_b = next_nid++;
				btorf("%d redor %d %d\n", nid_red_b, sid, nid_b);
				nid_b = nid_red_b;
			}

			int nid = next_nid++;
			if (btor_op != "not")
				btorf("%d %s %d %d %d%s\n", nid, btor_op.c_str(), sid, nid_a, nid_b, getinfo(cell).c_str());
			else
				btorf("%d %s %d %d%s\n", nid, btor_op.c_str(), sid, nid_a, getinfo(cell).c_str());

			SigSpec sig = sigmap(cell->getPort(ID::Y));

			if (GetSize(sig) > 1) {
				int sid = get_bv_sid(GetSize(sig));
				int zeros_nid = get_sig_nid(Const(0, GetSize(sig)-1));
				int nid2 = next_nid++;
				btorf("%d concat %d %d %d\n", nid2, sid, zeros_nid, nid);
				nid = nid2;
			}

			add_nid_sig(nid, sig);
			goto okay;
		}

		if (cell->type.in(ID($reduce_and), ID($reduce_or), ID($reduce_bool), ID($reduce_xor), ID($reduce_xnor)))
		{
			string btor_op;
			if (cell->type == ID($reduce_and)) btor_op = "redand";
			if (cell->type.in(ID($reduce_or), ID($reduce_bool))) btor_op = "redor";
			if (cell->type.in(ID($reduce_xor), ID($reduce_xnor))) btor_op = "redxor";
			log_assert(!btor_op.empty());

			int sid = get_bv_sid(1);
			int nid_a = get_sig_nid(cell->getPort(ID::A));

			int nid = next_nid++;

			if (cell->type == ID($reduce_xnor)) {
				int nid2 = next_nid++;
				btorf("%d %s %d %d%s\n", nid, btor_op.c_str(), sid, nid_a, getinfo(cell).c_str());
				btorf("%d not %d %d\n", nid2, sid, nid);
				nid = nid2;
			} else {
				btorf("%d %s %d %d%s\n", nid, btor_op.c_str(), sid, nid_a, getinfo(cell).c_str());
			}

			SigSpec sig = sigmap(cell->getPort(ID::Y));

			if (GetSize(sig) > 1) {
				int sid = get_bv_sid(GetSize(sig));
				int zeros_nid = get_sig_nid(Const(0, GetSize(sig)-1));
				int nid2 = next_nid++;
				btorf("%d concat %d %d %d\n", nid2, sid, zeros_nid, nid);
				nid = nid2;
			}

			add_nid_sig(nid, sig);
			goto okay;
		}

		if (cell->type.in(ID($mux), ID($_MUX_), ID($_NMUX_)))
		{
			SigSpec sig_a = sigmap(cell->getPort(ID::A));
			SigSpec sig_b = sigmap(cell->getPort(ID::B));
			SigSpec sig_s = sigmap(cell->getPort(ID::S));
			SigSpec sig_y = sigmap(cell->getPort(ID::Y));

			int nid_a = get_sig_nid(sig_a);
			int nid_b = get_sig_nid(sig_b);
			int nid_s = get_sig_nid(sig_s);

			int sid = get_bv_sid(GetSize(sig_y));
			int nid = next_nid++;

			if (cell->type == ID($_NMUX_)) {
				int tmp = nid;
				nid = next_nid++;
				btorf("%d ite %d %d %d %d\n", tmp, sid, nid_s, nid_b, nid_a);
				btorf("%d not %d %d%s\n", nid, sid, tmp, getinfo(cell).c_str());
			} else {
				btorf("%d ite %d %d %d %d%s\n", nid, sid, nid_s, nid_b, nid_a, getinfo(cell).c_str());
			}

			add_nid_sig(nid, sig_y);
			goto okay;
		}

		if (cell->type == ID($pmux))
		{
			SigSpec sig_a = sigmap(cell->getPort(ID::A));
			SigSpec sig_b = sigmap(cell->getPort(ID::B));
			SigSpec sig_s = sigmap(cell->getPort(ID::S));
			SigSpec sig_y = sigmap(cell->getPort(ID::Y));

			int width = GetSize(sig_a);
			int sid = get_bv_sid(width);
			int nid = get_sig_nid(sig_a);

			for (int i = 0; i < GetSize(sig_s); i++) {
				int nid_b = get_sig_nid(sig_b.extract(i*width, width));
				int nid_s = get_sig_nid(sig_s.extract(i));
				int nid2 = next_nid++;
				if (i == GetSize(sig_s)-1)
					btorf("%d ite %d %d %d %d%s\n", nid2, sid, nid_s, nid_b, nid, getinfo(cell).c_str());
				else
					btorf("%d ite %d %d %d %d\n", nid2, sid, nid_s, nid_b, nid);
				nid = nid2;
			}

			add_nid_sig(nid, sig_y);
			goto okay;
		}

		if (cell->type.in(ID($dff), ID($ff), ID($anyinit), ID($_DFF_P_), ID($_DFF_N), ID($_FF_)))
		{
			SigSpec sig_d = sigmap(cell->getPort(ID::D));
			SigSpec sig_q = sigmap(cell->getPort(ID::Q));

			if ((!info_filename.empty() || ywmap_json.active()) && cell->type.in(ID($dff), ID($_DFF_P_), ID($_DFF_N_)))
			{
				SigSpec sig_c = sigmap(cell->getPort(cell->type == ID($dff) ? ID::CLK : ID::C));
				int nid = get_sig_nid(sig_c);
				bool negedge = false;

				if (cell->type == ID($_DFF_N_))
					negedge = true;

				if (cell->type == ID($dff) && !cell->getParam(ID::CLK_POLARITY).as_bool())
					negedge = true;

				if (!info_filename.empty())
					info_clocks[nid] |= negedge ? 2 : 1;

				if (ywmap_json.active())
					ywmap_clock_bits[sig_c] |= negedge ? 2 : 1;
			}

			IdString symbol;

			if (sig_q.is_wire()) {
				Wire *w = sig_q.as_wire();
				if (w->port_id == 0) {
					statewires.insert(w);
					symbol = w->name;
				}
			}

			Const initval;
			for (int i = 0; i < GetSize(sig_q); i++)
				if (initbits.count(sig_q[i]))
					initval.bits().push_back(initbits.at(sig_q[i]) ? State::S1 : State::S0);
				else
					initval.bits().push_back(State::Sx);

			int nid_init_val = -1;

			if (!initval.is_fully_undef())
				nid_init_val = get_sig_nid(initval, -1, false, true);

			int sid = get_bv_sid(GetSize(sig_q));
			int nid = next_nid++;

			if (symbol.empty() || (!print_internal_names && symbol[0] == '$'))
				btorf("%d state %d\n", nid, sid);
			else
				btorf("%d state %d %s\n", nid, sid, log_id(symbol));

			if (cell->get_bool_attribute(ID(clk2fflogic)))
				ywmap_state(cell->getPort(ID::D)); // For a clk2fflogic FF the named signal is the D input not the Q output
			else
				ywmap_state(sig_q);

			if (nid_init_val >= 0) {
				int nid_init = next_nid++;
				if (verbose)
					btorf("; initval = %s\n", log_signal(initval));
				btorf("%d init %d %d %d\n", nid_init, sid, nid, nid_init_val);
			}

			ff_todo.push_back(make_pair(nid, cell));
			add_nid_sig(nid, sig_q);
			goto okay;
		}

		if (cell->type.in(ID($anyconst), ID($anyseq)))
		{
			SigSpec sig_y = sigmap(cell->getPort(ID::Y));

			int sid = get_bv_sid(GetSize(sig_y));
			int nid = next_nid++;

			btorf("%d state %d%s\n", nid, sid, getinfo(cell).c_str());

			ywmap_state(sig_y);

			if (cell->type == ID($anyconst)) {
				int nid2 = next_nid++;
				btorf("%d next %d %d %d\n", nid2, sid, nid, nid);
			}

			add_nid_sig(nid, sig_y);
			goto okay;
		}

		if (cell->type == ID($initstate))
		{
			SigSpec sig_y = sigmap(cell->getPort(ID::Y));

			if (initstate_nid < 0)
			{
				int sid = get_bv_sid(1);
				int one_nid = get_sig_nid(State::S1);
				int zero_nid = get_sig_nid(State::S0);
				initstate_nid = next_nid++;
				btorf("%d state %d%s\n", initstate_nid, sid, getinfo(cell).c_str());
				btorf("%d init %d %d %d\n", next_nid++, sid, initstate_nid, one_nid);
				btorf("%d next %d %d %d\n", next_nid++, sid, initstate_nid, zero_nid);

				ywmap_state(sig_y);
			}

			add_nid_sig(initstate_nid, sig_y);
			goto okay;
		}

		if (cell->is_mem_cell())
		{
			Mem *mem = mem_cells[cell];

			int abits = ceil_log2(mem->size);

			bool asyncwr = false;
			bool syncwr = false;

			for (auto &port : mem->wr_ports) {
				if (port.clk_enable)
					syncwr = true;
				else
					asyncwr = true;
			}

			if (asyncwr && syncwr)
				log_error("Memory %s.%s has mixed async/sync write ports.\n",
						log_id(module), log_id(mem->memid));

			for (auto &port : mem->rd_ports) {
				if (port.clk_enable)
					log_error("Memory %s.%s has sync read ports.  Please use memory_nordff to convert them first.\n",
							log_id(module), log_id(mem->memid));
			}

			int data_sid = get_bv_sid(mem->width);
			int bool_sid = get_bv_sid(1);
			int sid = get_mem_sid(abits, mem->width);

			int nid_init_val = -1;

			if (!mem->inits.empty())
			{
				Const initdata = mem->get_init_data();
				bool constword = true;
				Const firstword = initdata.extract(0, mem->width);

				for (int i = 1; i < mem->size; i++) {
					Const thisword = initdata.extract(i*mem->width, mem->width);
					if (thisword != firstword) {
						constword = false;
						break;
					}
				}

				// If not fully defined, undef bits should be able to take a
				// different value for each address so we can't initialise from
				// one value (and btor2parser doesn't like it)
				if (constword && firstword.is_fully_def())
				{
					if (verbose)
						btorf("; initval = %s\n", log_signal(firstword));
					nid_init_val = get_sig_nid(firstword, -1, false, true);
				}
				else
				{
					nid_init_val = next_nid++;
					btorf("%d state %d\n", nid_init_val, sid);

					ywmap_state(nullptr);

					for (int i = 0; i < mem->size; i++) {
						Const thisword = initdata.extract(i*mem->width, mem->width);
						if (thisword.is_fully_undef())
							continue;
						Const thisaddr(i, abits);
						int nid_thisword = get_sig_nid(thisword, -1, false, true);
						int nid_thisaddr = get_sig_nid(thisaddr, -1, false, true);
						int last_nid_init_val = nid_init_val;
						nid_init_val = next_nid++;
						if (verbose)
							btorf("; initval[%d] = %s\n", i, log_signal(thisword));
						btorf("%d write %d %d %d %d\n", nid_init_val, sid, last_nid_init_val, nid_thisaddr, nid_thisword);
					}
				}
			}


			int nid = next_nid++;
			int nid_head = nid;

			if (mem->memid[0] == '$')
				btorf("%d state %d\n", nid, sid);
			else
				btorf("%d state %d %s\n", nid, sid, log_id(mem->memid));

			ywmap_state(cell);

			if (nid_init_val >= 0)
			{
				int nid_init = next_nid++;
				btorf("%d init %d %d %d\n", nid_init, sid, nid, nid_init_val);
			}

			if (asyncwr)
			{
				for (auto &port : mem->wr_ports)
				{
					SigSpec wa = port.addr;
					wa.extend_u0(abits);

					int wa_nid = get_sig_nid(wa);
					int wd_nid = get_sig_nid(port.data);
					int we_nid = get_sig_nid(port.en);

					int nid2 = next_nid++;
					btorf("%d read %d %d %d\n", nid2, data_sid, nid_head, wa_nid);

					int nid3 = next_nid++;
					btorf("%d not %d %d\n", nid3, data_sid, we_nid);

					int nid4 = next_nid++;
					btorf("%d and %d %d %d\n", nid4, data_sid, nid2, nid3);

					int nid5 = next_nid++;
					btorf("%d and %d %d %d\n", nid5, data_sid, wd_nid, we_nid);

					int nid6 = next_nid++;
					btorf("%d or %d %d %d\n", nid6, data_sid, nid5, nid4);

					int nid7 = next_nid++;
					btorf("%d write %d %d %d %d\n", nid7, sid, nid_head, wa_nid, nid6);

					int nid8 = next_nid++;
					btorf("%d redor %d %d\n", nid8, bool_sid, we_nid);

					int nid9 = next_nid++;
					btorf("%d ite %d %d %d %d\n", nid9, sid, nid8, nid7, nid_head);

					nid_head = nid9;
				}
			}

			for (auto &port : mem->rd_ports)
			{
				SigSpec ra = port.addr;
				ra.extend_u0(abits);

				int ra_nid = get_sig_nid(ra);
				int rd_nid = next_nid++;

				btorf("%d read %d %d %d\n", rd_nid, data_sid, nid_head, ra_nid);

				add_nid_sig(rd_nid, port.data);
			}

			if (!asyncwr)
			{
				mem_todo.push_back(make_pair(nid, mem));
			}
			else
			{
				int nid2 = next_nid++;
				btorf("%d next %d %d %d\n", nid2, sid, nid, nid_head);
			}

			goto okay;
		}

		if (cell->type.in(ID($dffe), ID($sdff), ID($sdffe), ID($sdffce)) || cell->type.str().substr(0, 6) == "$_SDFF" || (cell->type.str().substr(0, 6) == "$_DFFE" && cell->type.str().size() == 10)) {
			log_error("Unsupported cell type %s for cell %s.%s -- please run `dffunmap` before `write_btor`.\n",
					log_id(cell->type), log_id(module), log_id(cell));
		}
		if (cell->type.in(ID($adff), ID($adffe), ID($aldff), ID($aldffe), ID($dffsr), ID($dffsre)) || cell->type.str().substr(0, 5) == "$_DFF" || cell->type.str().substr(0, 7) == "$_ALDFF") {
			log_error("Unsupported cell type %s for cell %s.%s -- please run `async2sync; dffunmap` or `clk2fflogic` before `write_btor`.\n",
					log_id(cell->type), log_id(module), log_id(cell));
		}
		if (cell->type.in(ID($sr), ID($dlatch), ID($adlatch), ID($dlatchsr)) || cell->type.str().substr(0, 8) == "$_DLATCH" || cell->type.str().substr(0, 5) == "$_SR_") {
			log_error("Unsupported cell type %s for cell %s.%s -- please run `clk2fflogic` before `write_btor`.\n",
					log_id(cell->type), log_id(module), log_id(cell));
		}
		log_error("Unsupported cell type %s for cell %s.%s.\n",
				log_id(cell->type), log_id(module), log_id(cell));

	okay:
		btorf_pop(log_id(cell));
		cell_recursion_guard.erase(cell);
	}

	int get_sig_nid(SigSpec sig, int to_width = -1, bool is_signed = false, bool is_init = false)
	{
		int nid = -1;
		sigmap.apply(sig);

		for (auto bit : sig)
			if (bit == State::Sx)
				goto has_undef_bits;

		if (0)
		{
	has_undef_bits:
			SigSpec sig_mask_undef, sig_noundef;
			int first_undef = -1;

			for (int i = 0; i < GetSize(sig); i++)
				if (sig[i] == State::Sx) {
					if (first_undef < 0)
						first_undef = i;
					sig_mask_undef.append(State::S1);
					sig_noundef.append(State::S0);
				} else {
					sig_mask_undef.append(State::S0);
					sig_noundef.append(sig[i]);
				}

			if (to_width < 0 || first_undef < to_width)
			{
				int sid = get_bv_sid(GetSize(sig));

				int nid_input = next_nid++;
				if (is_init) {
					btorf("%d state %d\n", nid_input, sid);
					ywmap_state(sig);
				} else {
					btorf("%d input %d\n", nid_input, sid);
					ywmap_input(sig);
				}

				int nid_masked_input;
				if (sig_mask_undef.is_fully_ones()) {
					nid_masked_input = nid_input;
				} else {
					int nid_mask_undef = get_sig_nid(sig_mask_undef);
					nid_masked_input = next_nid++;
					btorf("%d and %d %d %d\n", nid_masked_input, sid, nid_input, nid_mask_undef);
				}

				if (sig_noundef.is_fully_zero()) {
					nid = nid_masked_input;
				} else {
					int nid_noundef = get_sig_nid(sig_noundef);
					nid = next_nid++;
					btorf("%d or %d %d %d\n", nid, sid, nid_masked_input, nid_noundef);
				}

				goto extend_or_trim;
			}

			sig = sig_noundef;
		}

		if (sig_nid.count(sig) == 0)
		{
			// <nid>, <bitidx>
			vector<pair<int, int>> nidbits;

			// collect all bits
			for (int i = 0; i < GetSize(sig); i++)
			{
				SigBit bit = sig[i];

				if (bit_nid.count(bit) == 0)
				{
					if (bit.wire == nullptr)
					{
						Const c(bit.data);

						while (i+GetSize(c) < GetSize(sig) && sig[i+GetSize(c)].wire == nullptr)
							c.bits().push_back(sig[i+GetSize(c)].data);

						if (consts.count(c) == 0) {
							int sid = get_bv_sid(GetSize(c));
							int nid = next_nid++;
							btorf("%d const %d %s\n", nid, sid, c.as_string().c_str());
							consts[c] = nid;
							nid_width[nid] = GetSize(c);
						}

						int nid = consts.at(c);

						for (int j = 0; j < GetSize(c); j++)
							nidbits.push_back(make_pair(nid, j));

						i += GetSize(c)-1;
						continue;
					}
					else
					{
						if (bit_cell.count(bit) == 0)
						{
							SigSpec s = bit;

							while (i+GetSize(s) < GetSize(sig) && sig[i+GetSize(s)].wire != nullptr &&
									bit_cell.count(sig[i+GetSize(s)]) == 0)
								s.append(sig[i+GetSize(s)]);

							log_warning("No driver for signal %s.\n", log_signal(s));

							int sid = get_bv_sid(GetSize(s));
							int nid = next_nid++;
							btorf("%d input %d\n", nid, sid);
							ywmap_input(s);
							nid_width[nid] = GetSize(s);
							add_nid_sig(nid, s);

							for (int j = 0; j < GetSize(s); j++)
								nidbits.push_back(make_pair(nid, j));

							i += GetSize(s)-1;
							continue;
						}
						else
						{
							export_cell(bit_cell.at(bit));
							log_assert(bit_nid.count(bit));
						}
					}
				}

				nidbits.push_back(bit_nid.at(bit));
			}

			int width = 0;
			int nid = -1;

			// group bits and emit slice-concat chain
			for (int i = 0; i < GetSize(nidbits); i++)
			{
				int nid2 = nidbits[i].first;
				int lower =  nidbits[i].second;
				int upper = lower;

				while (i+1 < GetSize(nidbits) && nidbits[i+1].first == nidbits[i].first &&
						nidbits[i+1].second == nidbits[i].second+1)
					upper++, i++;

				int nid3 = nid2;

				if (lower != 0 || upper+1 != nid_width.at(nid2)) {
					int sid = get_bv_sid(upper-lower+1);
					nid3 = next_nid++;
					btorf("%d slice %d %d %d %d\n", nid3, sid, nid2, upper, lower);
				}

				int nid4 = nid3;

				if (nid >= 0) {
					int sid = get_bv_sid(width+upper-lower+1);
					nid4 = next_nid++;
					btorf("%d concat %d %d %d\n", nid4, sid, nid3, nid);
				}

				width += upper-lower+1;
				nid = nid4;
			}

			sig_nid[sig] = nid;
			nid_width[nid] = width;
		}

		nid = sig_nid.at(sig);

	extend_or_trim:
		if (to_width >= 0 && to_width != GetSize(sig))
		{
			if (to_width < GetSize(sig))
			{
				int sid = get_bv_sid(to_width);
				int nid2 = next_nid++;
				btorf("%d slice %d %d %d 0\n", nid2, sid, nid, to_width-1);
				nid = nid2;
			}
			else
			{
				int sid = get_bv_sid(to_width);
				int nid2 = next_nid++;
				btorf("%d %s %d %d %d\n", nid2, is_signed ? "sext" : "uext",
						sid, nid, to_width - GetSize(sig));
				nid = nid2;
			}
		}

		return nid;
	}

	BtorWorker(std::ostream &f, RTLIL::Module *module, bool verbose, bool single_bad, bool cover_mode, bool print_internal_names, string info_filename, string ywmap_filename) :
			f(f), sigmap(module), module(module), verbose(verbose), single_bad(single_bad), cover_mode(cover_mode), print_internal_names(print_internal_names), info_filename(info_filename)
	{
		if (!info_filename.empty())
			infof("name %s\n", log_id(module));

		if (!ywmap_filename.empty())
			ywmap_json.write_to_file(ywmap_filename);

		memories = Mem::get_all_memories(module);

		dict<IdString, Mem*> mem_dict;
		for (auto &mem : memories) {
			mem.narrow();
			mem_dict[mem.memid] = &mem;
		}
		for (auto cell : module->cells())
			if (cell->is_mem_cell())
				mem_cells[cell] = mem_dict[cell->parameters.at(ID::MEMID).decode_string()];

		btorf_push("inputs");

		if (ywmap_json.active()) {
			for (auto wire : module->wires())
			{
				auto gclk_attr = wire->attributes.find(ID::replaced_by_gclk);
				if (gclk_attr == wire->attributes.end())
					continue;
				SigSpec sig = sigmap(wire);
				if (gclk_attr->second == State::S1)
					ywmap_clock_bits[sig] |= 1;
				else if (gclk_attr->second == State::S0)
					ywmap_clock_bits[sig] |= 2;
			}
		}

		for (auto wire : module->wires())
		{
			if (wire->attributes.count(ID::init)) {
				Const attrval = wire->attributes.at(ID::init);
				for (int i = 0; i < GetSize(wire) && i < GetSize(attrval); i++)
					if (attrval[i] == State::S0 || attrval[i] == State::S1)
						initbits[sigmap(SigBit(wire, i))] = (attrval[i] == State::S1);
			}

			if (!wire->port_id || !wire->port_input)
				continue;

			SigSpec sig = sigmap(wire);
			int sid = get_bv_sid(GetSize(sig));
			int nid = next_nid++;

			btorf("%d input %d%s\n", nid, sid, getinfo(wire).c_str());
			ywmap_input(wire);
			add_nid_sig(nid, sig);

			if (!info_filename.empty()) {
				auto gclk_attr = wire->attributes.find(ID::replaced_by_gclk);
				if (gclk_attr != wire->attributes.end()) {
					if (gclk_attr->second == State::S1)
						info_clocks[nid] |= 1;
					else if (gclk_attr->second == State::S0)
						info_clocks[nid] |= 2;
				}
			}

			if (ywmap_json.active()) {
				for (int i = 0; i < GetSize(sig); i++) {
					auto input_bit = SigBit(wire, i);
					auto bit = sigmap(input_bit);
					if (!ywmap_clock_bits.count(bit))
						continue;
					ywmap_clock_inputs[input_bit] = ywmap_clock_bits[bit];
				}
			}
		}

		btorf_pop("inputs");

		for (auto cell : module->cells())
		for (auto &conn : cell->connections())
		{
			if (!cell->output(conn.first))
				continue;

			for (auto bit : sigmap(conn.second))
				bit_cell[bit] = cell;
		}

		for (auto wire : module->wires())
		{
			if (!wire->port_id || !wire->port_output)
				continue;

			btorf_push(stringf("output %s", log_id(wire)));

			int nid = get_sig_nid(wire);
			btorf("%d output %d%s\n", next_nid++, nid, getinfo(wire).c_str());

			btorf_pop(stringf("output %s", log_id(wire)));
		}

		for (auto cell : module->cells())
		{
			if (cell->type == ID($assume))
			{
				btorf_push(log_id(cell));

				int sid = get_bv_sid(1);
				int nid_a = get_sig_nid(cell->getPort(ID::A));
				int nid_en = get_sig_nid(cell->getPort(ID::EN));
				int nid_not_en = next_nid++;
				int nid_a_or_not_en = next_nid++;
				int nid = next_nid++;

				btorf("%d not %d %d\n", nid_not_en, sid, nid_en);
				btorf("%d or %d %d %d\n", nid_a_or_not_en, sid, nid_a, nid_not_en);
				btorf("%d constraint %d\n", nid, nid_a_or_not_en);

				btorf_pop(log_id(cell));
			}

			if (cell->type == ID($assert))
			{
				btorf_push(log_id(cell));

				int sid = get_bv_sid(1);
				int nid_a = get_sig_nid(cell->getPort(ID::A));
				int nid_en = get_sig_nid(cell->getPort(ID::EN));
				int nid_not_a = next_nid++;
				int nid_en_and_not_a = next_nid++;

				btorf("%d not %d %d\n", nid_not_a, sid, nid_a);
				btorf("%d and %d %d %d\n", nid_en_and_not_a, sid, nid_en, nid_not_a);

				if (single_bad && !cover_mode) {
					bad_properties.push_back(nid_en_and_not_a);
				} else {
					if (cover_mode) {
						infof("bad %d%s\n", nid_en_and_not_a, getinfo(cell, true).c_str());
					} else {
						int nid = next_nid++;
						btorf("%d bad %d%s\n", nid, nid_en_and_not_a, getinfo(cell, true).c_str());
					}
				}

				btorf_pop(log_id(cell));
			}

			if (cell->type == ID($cover) && cover_mode)
			{
				btorf_push(log_id(cell));

				int sid = get_bv_sid(1);
				int nid_a = get_sig_nid(cell->getPort(ID::A));
				int nid_en = get_sig_nid(cell->getPort(ID::EN));
				int nid_en_and_a = next_nid++;

				btorf("%d and %d %d %d\n", nid_en_and_a, sid, nid_en, nid_a);

				if (single_bad) {
					bad_properties.push_back(nid_en_and_a);
				} else {
					int nid = next_nid++;
					btorf("%d bad %d%s\n", nid, nid_en_and_a, getinfo(cell, true).c_str());
				}

				btorf_pop(log_id(cell));
			}
		}

		for (auto wire : module->wires())
		{
			if (wire->port_id || wire->name[0] == '$')
				continue;

			btorf_push(stringf("wire %s", log_id(wire)));

			int sid = get_bv_sid(GetSize(wire));
			int nid = get_sig_nid(sigmap(wire));

			if (statewires.count(wire))
				continue;

			int this_nid = next_nid++;
			btorf("%d uext %d %d %d%s\n", this_nid, sid, nid, 0, getinfo(wire).c_str());
			if (info_clocks.count(nid))
				info_clocks[this_nid] |= info_clocks[nid];

			btorf_pop(stringf("wire %s", log_id(wire)));
			continue;
		}

		while (!ff_todo.empty() || !mem_todo.empty())
		{
			vector<pair<int, Cell*>> todo;
			todo.swap(ff_todo);

			for (auto &it : todo)
			{
				int nid = it.first;
				Cell *cell = it.second;

				btorf_push(stringf("next %s", log_id(cell)));

				SigSpec sig = sigmap(cell->getPort(ID::D));
				int nid_q = get_sig_nid(sig);
				int sid = get_bv_sid(GetSize(sig));
				btorf("%d next %d %d %d%s\n", next_nid++, sid, nid, nid_q, getinfo(cell).c_str());

				btorf_pop(stringf("next %s", log_id(cell)));
			}

			vector<pair<int, Mem*>> mtodo;
			mtodo.swap(mem_todo);

			for (auto &it : mtodo)
			{
				int nid = it.first;
				Mem *mem = it.second;

				btorf_push(stringf("next %s", log_id(mem->memid)));

				int abits = ceil_log2(mem->size);

				int data_sid = get_bv_sid(mem->width);
				int bool_sid = get_bv_sid(1);
				int sid = get_mem_sid(abits, mem->width);
				int nid_head = nid;

				for (auto &port : mem->wr_ports)
				{
					SigSpec wa = port.addr;
					wa.extend_u0(abits);

					int wa_nid = get_sig_nid(wa);
					int wd_nid = get_sig_nid(port.data);
					int we_nid = get_sig_nid(port.en);

					int nid2 = next_nid++;
					btorf("%d read %d %d %d\n", nid2, data_sid, nid_head, wa_nid);

					int nid3 = next_nid++;
					btorf("%d not %d %d\n", nid3, data_sid, we_nid);

					int nid4 = next_nid++;
					btorf("%d and %d %d %d\n", nid4, data_sid, nid2, nid3);

					int nid5 = next_nid++;
					btorf("%d and %d %d %d\n", nid5, data_sid, wd_nid, we_nid);

					int nid6 = next_nid++;
					btorf("%d or %d %d %d\n", nid6, data_sid, nid5, nid4);

					int nid7 = next_nid++;
					btorf("%d write %d %d %d %d\n", nid7, sid, nid_head, wa_nid, nid6);

					int nid8 = next_nid++;
					btorf("%d redor %d %d\n", nid8, bool_sid, we_nid);

					int nid9 = next_nid++;
					btorf("%d ite %d %d %d %d\n", nid9, sid, nid8, nid7, nid_head);

					nid_head = nid9;
				}

				int nid2 = next_nid++;
				btorf("%d next %d %d %d%s\n", nid2, sid, nid, nid_head, (mem->cell ? getinfo(mem->cell) : getinfo(mem->mem)).c_str());

				btorf_pop(stringf("next %s", log_id(mem->memid)));
			}
		}

		while (!bad_properties.empty())
		{
			vector<int> todo;
			bad_properties.swap(todo);

			int sid = get_bv_sid(1);
			int cursor = 0;

			while (cursor+1 < GetSize(todo))
			{
				int nid_a = todo[cursor++];
				int nid_b = todo[cursor++];
				int nid = next_nid++;

				bad_properties.push_back(nid);
				btorf("%d or %d %d %d\n", nid, sid, nid_a, nid_b);
			}

			if (!bad_properties.empty()) {
				if (cursor < GetSize(todo))
					bad_properties.push_back(todo[cursor++]);
				log_assert(cursor == GetSize(todo));
			} else {
				int nid = next_nid++;
				log_assert(cursor == 0);
				log_assert(GetSize(todo) == 1);
				btorf("%d bad %d\n", nid, todo[cursor]);
			}
		}

		if (!info_filename.empty())
		{
			for (auto &it : info_clocks)
			{
				switch (it.second)
				{
				case 1:
					infof("posedge %d\n", it.first);
					break;
				case 2:
					infof("negedge %d\n", it.first);
					break;
				case 3:
					infof("event %d\n", it.first);
					break;
				default:
					log_abort();
				}
			}

			std::ofstream f;
			f.open(info_filename.c_str(), std::ofstream::trunc);
			if (f.fail())
				log_error("Can't open file `%s' for writing: %s\n", info_filename.c_str(), strerror(errno));
			for (auto &it : info_lines)
				f << it;
			f.close();
		}

		if (ywmap_json.active())
		{
			ywmap_json.begin_object();
			ywmap_json.entry("version", "Yosys Witness BTOR map");
			ywmap_json.entry("generator", yosys_version_str);

			ywmap_json.name("clocks");
			ywmap_json.begin_array();
			for (auto &entry : ywmap_clock_inputs) {
				if (entry.second != 1 && entry.second != 2)
					continue;
				log_assert(entry.first.is_wire());
				ywmap_json.begin_object();
				ywmap_json.compact();
				ywmap_json.entry("path", witness_path(entry.first.wire));
				ywmap_json.entry("offset", entry.first.offset);
				ywmap_json.entry("edge", entry.second == 1 ? "posedge" : "negedge");
				ywmap_json.end_object();
			}
			ywmap_json.end_array();

			ywmap_json.name("inputs");
			ywmap_json.begin_array();
			for (auto &entry : ywmap_inputs)
				emit_ywmap_btor_sig(entry);
			ywmap_json.end_array();

			ywmap_json.name("states");
			ywmap_json.begin_array();
			for (auto &entry : ywmap_states)
				emit_ywmap_btor_sig(entry);
			ywmap_json.end_array();

			ywmap_json.end_object();
		}
	}
};

struct BtorBackend : public Backend {
	BtorBackend() : Backend("btor", "write design to BTOR file") { }
	void help() override
	{
		//   |---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|
		log("\n");
		log("    write_btor [options] [filename]\n");
		log("\n");
		log("Write a BTOR description of the current design.\n");
		log("\n");
		log("  -v\n");
		log("    Add comments and indentation to BTOR output file\n");
		log("\n");
		log("  -s\n");
		log("    Output only a single bad property for all asserts\n");
		log("\n");
		log("  -c\n");
		log("    Output cover properties using 'bad' statements instead of asserts\n");
		log("\n");
		log("  -i <filename>\n");
		log("    Create additional info file with auxiliary information\n");
		log("\n");
		log("  -x\n");
		log("    Output symbols for internal netnames (starting with '$')\n");
		log("\n");
		log("  -ywmap <filename>\n");
		log("    Create a map file for conversion to and from Yosys witness traces\n");
		log("\n");
	}
	void execute(std::ostream *&f, std::string filename, std::vector<std::string> args, RTLIL::Design *design) override
	{
		bool verbose = false, single_bad = false, cover_mode = false, print_internal_names = false;
		string info_filename;
		string ywmap_filename;

		log_header(design, "Executing BTOR backend.\n");

		log_push();
		Pass::call(design, "bmuxmap");
		Pass::call(design, "demuxmap");
		Pass::call(design, "bwmuxmap");
		log_pop();

		size_t argidx;
		for (argidx = 1; argidx < args.size(); argidx++)
		{
			if (args[argidx] == "-v") {
				verbose = true;
				continue;
			}
			if (args[argidx] == "-s") {
				single_bad = true;
				continue;
			}
			if (args[argidx] == "-c") {
				cover_mode = true;
				continue;
			}
			if (args[argidx] == "-i" && argidx+1 < args.size()) {
				info_filename = args[++argidx];
				continue;
			}
			if (args[argidx] == "-x") {
				print_internal_names = true;
				continue;
			}
			if (args[argidx] == "-ywmap" && argidx+1 < args.size()) {
				ywmap_filename = args[++argidx];
				continue;
			}
			break;
		}
		extra_args(f, filename, args, argidx);

		RTLIL::Module *topmod = design->top_module();

		if (topmod == nullptr)
			log_cmd_error("No top module found.\n");

		*f << stringf("; BTOR description generated by %s for module %s.\n",
				yosys_version_str, log_id(topmod));

		BtorWorker(*f, topmod, verbose, single_bad, cover_mode, print_internal_names, info_filename, ywmap_filename);

		*f << stringf("; end of yosys output\n");
	}
} BtorBackend;

PRIVATE_NAMESPACE_END