backends/smv/smv.cc


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             LUFA Library
     Copyright (C) Dean Camera, 2017.

  dean [at] fourwalledcubicle [dot] com
           www.lufa-lib.org
*/

/*
  Copyright 2017  Dean Camera (dean [at] fourwalledcubicle [dot] com)
  Copyright 2012  Simon Foster (simon.foster [at] inbox [dot] com)

  Permission to use, copy, modify, distribute, and sell this
  software and its documentation for any purpose is hereby granted
  without fee, provided that the above copyright notice appear in
  all copies and that both that the copyright notice and this
  permission notice and warranty disclaimer appear in supporting
  documentation, and that the name of the author not be used in
  advertising or publicity pertaining to distribution of the
  software without specific, written prior permission.

  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, 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.
*/

/** \file
 *
 *  Header file for SerialToLCD.c.
 */

#ifndef _SERIALTOLCD_H_
#define _SERIALTOLCD_H_

	/* Includes: */
		#include <avr/io.h>
		#include <avr/wdt.h>
		#include <avr/interrupt.h>
		#include <avr/power.h>

		#include "Descriptors.h"
		#include "Lib/HD44780.h"

		#include <LUFA/Version.h>
		#include <LUFA/Drivers/Misc/RingBuffer.h>
		#include <LUFA/Drivers/USB/USB.h>
		#include <LUFA/Platform/Platform.h>

	/* Macros: */
		#define COMMAND_ESCAPE     0x1B

	/* Function Prototypes: */
		void SetupHardware(void);

		void EVENT_USB_Device_ConfigurationChanged(void);
		void EVENT_USB_Device_ControlRequest(void);

#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.
 *
 */

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

USING_YOSYS_NAMESPACE
PRIVATE_NAMESPACE_BEGIN

struct SmvWorker
{
	CellTypes ct;
	SigMap sigmap;
	RTLIL::Module *module;
	std::ostream &f;
	bool verbose;

	int idcounter;
	dict<IdString, shared_str> idcache;
	pool<shared_str> used_names;
	vector<shared_str> strbuf;

	pool<Wire*> partial_assignment_wires;
	dict<SigBit, std::pair<const char*, int>> partial_assignment_bits;
	vector<string> assignments, invarspecs;

	const char *cid()
	{
		while (true) {
			shared_str s(stringf("_%d", idcounter++));
			if (!used_names.count(s)) {
				used_names.insert(s);
				return s.c_str();
			}
		}
	}

	const char *cid(IdString id, bool precache = false)
	{
		if (!idcache.count(id))
		{
			string name = stringf("_%s", id.c_str());

			if (name.substr(0, 2) == "_\\")
				name = "_" + name.substr(2);

			for (auto &c : name) {
				if (c == '|' || c == '$' || c == '_') continue;
				if (c >= 'a' && c <='z') continue;
				if (c >= 'A' && c <='Z') continue;
				if (c >= '0' && c <='9') continue;
				if (precache) return nullptr;
				c = '#';
			}

			if (name == "_main")
				name = "main";

			while (used_names.count(name))
				name += "_";

			shared_str s(name);
			used_names.insert(s);
			idcache[id] = s;
		}

		return idcache.at(id).c_str();
	}

	SmvWorker(RTLIL::Module *module, bool verbose, std::ostream &f) :
			ct(module->design), sigmap(module), module(module), f(f), verbose(verbose), idcounter(0)
	{
		for (auto mod : module->design->modules())
			cid(mod->name, true);

		for (auto wire : module->wires())
			cid(wire->name, true);

		for (auto cell : module->cells()) {
			cid(cell->name, true);
			cid(cell->type, true);
			for (auto &conn : cell->connections())
				cid(conn.first, true);
		}
	}

	const char *rvalue(SigSpec sig, int width = -1, bool is_signed = false)
	{
		string s;
		int count_chunks = 0;
		sigmap.apply(sig);

		for (int i = 0; i < GetSize(sig); i++)
			if (partial_assignment_bits.count(sig[i]))
			{
				int width = 1;
				const auto &bit_a = partial_assignment_bits.at(sig[i]);

				while (i+width < GetSize(sig))
				{
					if (!partial_assignment_bits.count(sig[i+width]))
						break;

					const auto &bit_b = partial_assignment_bits.at(sig[i+width]);
					if (strcmp(bit_a.first, bit_b.first))
						break;
					if (bit_a.second+width != bit_b.second)
						break;

					width++;
				}

				if (i+width < GetSize(sig))
					s = stringf("%s :: ", rvalue(sig.extract(i+width, GetSize(sig)-(width+i))));

				s += stringf("%s[%d:%d]", bit_a.first, bit_a.second+width-1, bit_a.second);

				if (i > 0)
					s += stringf(" :: %s", rvalue(sig.extract(0, i)));

				count_chunks = 3;
				goto continue_with_resize;
			}

		for (auto &c : sig.chunks()) {
			count_chunks++;
			if (!s.empty())
				s = " :: " + s;
			if (c.wire) {
				if (c.offset != 0 || c.width != c.wire->width)
					s = stringf("%s[%d:%d]", cid(c.wire->name), c.offset+c.width-1, c.offset) + s;
				else
					s = cid(c.wire->name) + s;
			} else {
				string v = stringf("0ub%d_", c.width);
				for (int i = c.width-1; i >= 0; i--)
					v += c.data.at(i) == State::S1 ? '1' : '0';
				s = v + s;
			}
		}

	continue_with_resize:;
		if (width >= 0) {
			if (is_signed) {
				if (GetSize(sig) > width)
					s = stringf("signed(resize(%s, %d))", s.c_str(), width);
				else
					s = stringf("resize(signed(%s), %d)", s.c_str(), width);
			} else
				s = stringf("resize(%s, %d)", s.c_str(), width);
		} else if (is_signed)
			s = stringf("signed(%s)", s.c_str());
		else if (count_chunks > 1)
			s = stringf("(%s)", s.c_str());

		strbuf.push_back(s);
		return strbuf.back().c_str();
	}

	const char *rvalue_u(SigSpec sig, int width = -1)
	{
		return rvalue(sig, width, false);
	}

	const char *rvalue_s(SigSpec sig, int width = -1, bool is_signed = true)
	{
		return rvalue(sig, width, is_signed);
	}

	const char *lvalue(SigSpec sig)
	{
		sigmap.apply(sig);

		if (sig.is_wire())
			return rvalue(sig);

		const char *temp_id = cid();
		f << stringf("    %s : unsigned word[%d]; -- %s\n", temp_id, GetSize(sig), log_signal(sig));

		int offset = 0;
		for (auto bit : sig) {
			log_assert(bit.wire != nullptr);
			partial_assignment_wires.insert(bit.wire);
			partial_assignment_bits[bit] = std::pair<const char*, int>(temp_id, offset++);
		}

		return temp_id;
	}

	void run()
	{
		f << stringf("MODULE %s\n", cid(module->name));
		f << stringf("  VAR\n");

		for (auto wire : module->wires())
		{
			if (SigSpec(wire) != sigmap(wire))
				partial_assignment_wires.insert(wire);

			f << stringf("    %s : unsigned word[%d]; -- %s\n", cid(wire->name), wire->width, log_id(wire));

			if (wire->attributes.count("\\init"))
				assignments.push_back(stringf("init(%s) := %s;", lvalue(wire), rvalue(wire->attributes.at("\\init"))));
		}

		for (auto cell : module->cells())
		{
			// FIXME: $slice, $concat, $mem

			if (cell->type.in("$assert"))
			{
				SigSpec sig_a = cell->getPort("\\A");
				SigSpec sig_en = cell->getPort("\\EN");

				invarspecs.push_back(stringf("!bool(%s) | bool(%s);", rvalue(sig_en), rvalue(sig_a)));

				continue;
			}

			if (cell->type.in("$shl", "$shr", "$sshl", "$sshr", "$shift", "$shiftx"))
			{
				SigSpec sig_a = cell->getPort("\\A");
				SigSpec sig_b = cell->getPort("\\B");

				int width_y = GetSize(cell->getPort("\\Y"));
				int shift_b_width = GetSize(sig_b);
				int width_ay = max(GetSize(sig_a), width_y);
				int width = width_ay;

				for (int i = 1, j = 0;; i <<= 1, j++)
					if (width_ay < i) {
						width = i-1;
						shift_b_width = min(shift_b_width, j);
						break;
					}

				bool signed_a = cell->getParam("\\A_SIGNED").as_bool();
				bool signed_b = cell->getParam("\\B_SIGNED").as_bool();
				string op = cell->type.in("$shl", "$sshl") ? "<<" : ">>";
				string expr, expr_a;

				if (cell->type == "$sshr" && signed_a)
				{
					expr_a = rvalue_s(sig_a, width);
					expr = stringf("resize(unsigned(%s %s %s), %d)", expr_a.c_str(), op.c_str(), rvalue(sig_b.extract(0, shift_b_width)), width_y);
					if (shift_b_width < GetSize(sig_b))
						expr = stringf("%s != 0ud%d_0 ? (bool(%s) ? !0ud%d_0 : 0ud%d_0) : %s",
								rvalue(sig_b.extract(shift_b_width, GetSize(sig_b) - shift_b_width)), GetSize(sig_b) - shift_b_width,
								rvalue(sig_a[GetSize(sig_a)-1]), width_y, width_y, expr.c_str());
				}
				else if (cell->type.in("$shift", "$shiftx") && signed_b)
				{
					expr_a = rvalue_u(sig_a, width);

					const char *b_shr = rvalue_u(sig_b);
					const char *b_shl = cid();

					f << stringf("    %s : unsigned word[%d]; -- neg(%s)\n", b_shl, GetSize(sig_b), log_signal(sig_b));
					assignments.push_back(stringf("%s := unsigned(-%s);", b_shl, rvalue_s(sig_b)));

					string expr_shl = stringf("resize(%s << %s[%d:0], %d)", expr_a.c_str(), b_shl, shift_b_width-1, width_y);
					string expr_shr = stringf("resize(%s >> %s[%d:0], %d)", expr_a.c_str(), b_shr, shift_b_width-1, width_y);

					if (shift_b_width < GetSize(sig_b)) {
						expr_shl = stringf("%s[%d:%d] != 0ud%d_0 ? 0ud%d_0 : %s", b_shl, GetSize(sig_b)-1, shift_b_width,
								GetSize(sig_b)-shift_b_width, width_y, expr_shl.c_str());
						expr_shr = stringf("%s[%d:%d] != 0ud%d_0 ? 0ud%d_0 : %s", b_shr, GetSize(sig_b)-1, shift_b_width,
								GetSize(sig_b)-shift_b_width, width_y, expr_shr.c_str());
					}

					expr = stringf("bool(%s) ? %s : %s", rvalue(sig_b[GetSize(sig_b)-1]), expr_shl.c_str(), expr_shr.c_str());
				}
				else
				{
					if (cell->type.in("$shift", "$shiftx") || !signed_a)
						expr_a = rvalue_u(sig_a, width);
					else
						expr_a = stringf("resize(unsigned(%s), %d)", rvalue_s(sig_a, width_ay), width);

					expr = stringf("resize(%s %s %s[%d:0], %d)", expr_a.c_str(), op.c_str(), rvalue_u(sig_b), shift_b_width-1, width_y);
					if (shift_b_width < GetSize(sig_b))
						expr = stringf("%s[%d:%d] != 0ud%d_0 ? 0ud%d_0 : %s", rvalue_u(sig_b), GetSize(sig_b)-1, shift_b_width,
								GetSize(sig_b)-shift_b_width, width_y, expr.c_str());
				}

				assignments.push_back(stringf("%s := %s;", lvalue(cell->getPort("\\Y")), expr.c_str()));

				continue;
			}

			if (cell->type.in("$not", "$pos", "$neg"))
			{
				int width = GetSize(cell->getPort("\\Y"));
				string expr_a, op;

				if (cell->type == "$not")  op = "!";
				if (cell->type == "$pos")  op = "";
				if (cell->type == "$neg")  op = "-";

				if (cell->getParam("\\A_SIGNED").as_bool())
				{
					assignments.push_back(stringf("%s := unsigned(%s%s);", lvalue(cell->getPort("\\Y")),
							op.c_str(), rvalue_s(cell->getPort("\\A"), width)));
				}
				else
				{
					assignments.push_back(stringf("%s := %s%s;", lvalue(cell->getPort("\\Y")),
							op.c_str(), rvalue_u(cell->getPort("\\A"), width)));
				}

				continue;
			}

			if (cell->type.in("$add", "$sub", "$mul", "$and", "$or", "$xor", "$xnor"))
			{
				int width = GetSize(cell->getPort("\\Y"));
				string expr_a, expr_b, op;

				if (cell->type == "$add")  op = "+";
				if (cell->type == "$sub")  op = "-";
				if (cell->type == "$mul")  op = "*";
				if (cell->type == "$and")  op = "&";
				if (cell->type == "$or")   op = "|";
				if (cell->type == "$xor")  op = "xor";
				if (cell->type == "$xnor") op = "xnor";

				if (cell->getParam("\\A_SIGNED").as_bool())
				{
					assignments.push_back(stringf("%s := unsigned(%s %s %s);", lvalue(cell->getPort("\\Y")),
							rvalue_s(cell->getPort("\\A"), width), op.c_str(), rvalue_s(cell->getPort("\\B"), width)));
				}
				else
				{
					assignments.push_back(stringf("%s := %s %s %s;", lvalue(cell->getPort("\\Y")),
							rvalue_u(cell->getPort("\\A"), width), op.c_str(), rvalue_u(cell->getPort("\\B"), width)));
				}

				continue;
			}

			if (cell->type.in("$div", "$mod"))
			{
				int width_y = GetSize(cell->getPort("\\Y"));
				int width = max(width_y, GetSize(cell->getPort("\\A")));
				width = max(width, GetSize(cell->getPort("\\B")));
				string expr_a, expr_b, op;

				if (cell->type == "$div")  op = "/";
				if (cell->type == "$mod")  op = "mod";

				if (cell->getParam("\\A_SIGNED").as_bool())
				{
					assignments.push_back(stringf("%s := resize(unsigned(%s %s %s), %d);", lvalue(cell->getPort("\\Y")),
							rvalue_s(cell->getPort("\\A"), width), op.c_str(), rvalue_s(cell->getPort("\\B"), width), width_y));
				}
				else
				{
					assignments.push_back(stringf("%s := resize(%s %s %s, %d);", lvalue(cell->getPort("\\Y")),
							rvalue_u(cell->getPort("\\A"), width), op.c_str(), rvalue_u(cell->getPort("\\B"), width), width_y));
				}

				continue;
			}

			if (cell->type.in("$eq", "$ne", "$eqx", "$nex", "$lt", "$le", "$ge", "$gt"))
			{
				int width = max(GetSize(cell->getPort("\\A")), GetSize(cell->getPort("\\B")));
				string expr_a, expr_b, op;

				if (cell->type == "$eq")  op = "=";
				if (cell->type == "$ne")  op = "!=";
				if (cell->type == "$eqx") op = "=";
				if (cell->type == "$nex") op = "!=";
				if (cell->type == "$lt")  op = "<";
				if (cell->type == "$le")  op = "<=";
				if (cell->type == "$ge")  op = ">=";
				if (cell->type == "$gt")  op = ">";

				if (cell->getParam("\\A_SIGNED").as_bool())
				{
					expr_a = stringf("resize(signed(%s), %d)", rvalue(cell->getPort("\\A")), width);
					expr_b = stringf("resize(signed(%s), %d)", rvalue(cell->getPort("\\B")), width);
				}
				else
				{
					expr_a = stringf("resize(%s, %d)", rvalue(cell->getPort("\\A")), width);
					expr_b = stringf("resize(%s, %d)", rvalue(cell->getPort("\\B")), width);
				}

				assignments.push_back(stringf("%s := resize(word1(%s %s %s), %d);", lvalue(cell->getPort("\\Y")),
						expr_a.c_str(), op.c_str(), expr_b.c_str(), GetSize(cell->getPort("\\Y"))));

				continue;
			}

			if (cell->type.in("$reduce_and", "$reduce_or", "$reduce_bool"))
			{
				int width_a = GetSize(cell->getPort("\\A"));
				int width_y = GetSize(cell->getPort("\\Y"));
				const char *expr_a = rvalue(cell->getPort("\\A"));
				const char *expr_y = lvalue(cell->getPort("\\Y"));
				string expr;

				if (cell->type == "$reduce_and")  expr = stringf("%s = !0ub%d_0", expr_a, width_a);
				if (cell->type == "$reduce_or")   expr = stringf("%s != 0ub%d_0", expr_a, width_a);
				if (cell->type == "$reduce_bool") expr = stringf("%s != 0ub%d_0", expr_a, width_a);

				assignments.push_back(stringf("%s := resize(word1(%s), %d);", expr_y, expr.c_str(), width_y));
				continue;
			}

			if (cell->type.in("$reduce_xor", "$reduce_xnor"))
			{
				int width_y = GetSize(cell->getPort("\\Y"));
				const char *expr_y = lvalue(cell->getPort("\\Y"));
				string expr;

				for (auto bit : cell->getPort("\\A")) {
					if (!expr.empty())
						expr += " xor ";
					expr += rvalue(bit);
				}

				if (cell->type == "$reduce_xnor")
					expr = "!(" + expr + ")";

				assignments.push_back(stringf("%s := resize(%s, %d);", expr_y, expr.c_str(), width_y));
				continue;
			}

			if (cell->type.in("$logic_and", "$logic_or"))
			{
				int width_a = GetSize(cell->getPort("\\A"));
				int width_b = GetSize(cell->getPort("\\B"));
				int width_y = GetSize(cell->getPort("\\Y"));

				string expr_a = stringf("(%s != 0ub%d_0)", rvalue(cell->getPort("\\A")), width_a);
				string expr_b = stringf("(%s != 0ub%d_0)", rvalue(cell->getPort("\\B")), width_b);
				const char *expr_y = lvalue(cell->getPort("\\Y"));

				string expr;
				if (cell->type == "$logic_and") expr = expr_a + " & " + expr_b;
				if (cell->type == "$logic_or")  expr = expr_a + " | " + expr_b;

				assignments.push_back(stringf("%s := resize(word1(%s), %d);", expr_y, expr.c_str(), width_y));
				continue;
			}

			if (cell->type.in("$logic_not"))
			{
				int width_a = GetSize(cell->getPort("\\A"));
				int width_y = GetSize(cell->getPort("\\Y"));

				string expr_a = stringf("(%s = 0ub%d_0)", rvalue(cell->getPort("\\A")), width_a);
				const char *expr_y = lvalue(cell->getPort("\\Y"));

				assignments.push_back(stringf("%s := resize(word1(%s), %d);", expr_y, expr_a.c_str(), width_y));
				continue;
			}

			if (cell->type.in("$mux", "$pmux"))
			{
				int width = GetSize(cell->getPort("\\Y"));
				SigSpec sig_a = cell->getPort("\\A");
				SigSpec sig_b = cell->getPort("\\B");
				SigSpec sig_s = cell->getPort("\\S");

				string expr;
				for (int i = 0; i < GetSize(sig_s); i++)
					expr += stringf("bool(%s) ? %s : ", rvalue(sig_s[i]), rvalue(sig_b.extract(i*width, width)));
				expr += rvalue(sig_a);

				assignments.push_back(stringf("%s := %s;", lvalue(cell->getPort("\\Y")), expr.c_str()));
				continue;
			}

			if (cell->type == "$dff")
			{
				assignments.push_back(stringf("next(%s) := %s;", lvalue(cell->getPort("\\Q")), rvalue(cell->getPort("\\D"))));
				continue;
			}

			if (cell->type.in("$_BUF_", "$_NOT_"))
			{
				string op = cell->type == "$_NOT_" ? "!" : "";
				assignments.push_back(stringf("%s := %s%s;", lvalue(cell->getPort("\\Y")), op.c_str(), rvalue(cell->getPort("\\A"))));
				continue;
			}

			if (cell->type.in("$_AND_", "$_NAND_", "$_OR_", "$_NOR_", "$_XOR_", "$_XNOR_"))
			{
				string op;

				if (cell->type.in("$_AND_", "$_NAND_")) op = "&";
				if (cell->type.in("$_OR_", "$_NOR_")) op = "|";
				if (cell->type.in("$_XOR_"))  op = "xor";
				if (cell->type.in("$_XNOR_"))  op = "xnor";

				if (cell->type.in("$_NAND_", "$_NOR_"))
					assignments.push_back(stringf("%s := !(%s %s %s);", lvalue(cell->getPort("\\Y")),
							rvalue(cell->getPort("\\A")), op.c_str(), rvalue(cell->getPort("\\B"))));
				else
					assignments.push_back(stringf("%s := %s %s %s;", lvalue(cell->getPort("\\Y")),
							rvalue(cell->getPort("\\A")), op.c_str(), rvalue(cell->getPort("\\B"))));
				continue;
			}

			if (cell->type == "$_MUX_")
			{
				assignments.push_back(stringf("%s := bool(%s) ? %s : %s;", lvalue(cell->getPort("\\Y")),
						rvalue(cell->getPort("\\S")), rvalue(cell->getPort("\\B")), rvalue(cell->getPort("\\A"))));
				continue;
			}

			if (cell->type == "$_AOI3_")
			{
				assignments.push_back(stringf("%s := !((%s & %s) | %s);", lvalue(cell->getPort("\\Y")),
						rvalue(cell->getPort("\\A")), rvalue(cell->getPort("\\B")), rvalue(cell->getPort("\\C"))));
				continue;
			}

			if (cell->type == "$_OAI3_")
			{
				assignments.push_back(stringf("%s := !((%s | %s) & %s);", lvalue(cell->getPort("\\Y")),
						rvalue(cell->getPort("\\A")), rvalue(cell->getPort("\\B")), rvalue(cell->getPort("\\C"))));
				continue;
			}

			if (cell->type == "$_AOI4_")
			{
				assignments.push_back(stringf("%s := !((%s & %s) | (%s & %s));", lvalue(cell->getPort("\\Y")),
						rvalue(cell->getPort("\\A")), rvalue(cell->getPort("\\B")), rvalue(cell->getPort("\\C")), rvalue(cell->getPort("\\D"))));
				continue;
			}

			if (cell->type == "$_OAI4_")
			{
				assignments.push_back(stringf("%s := !((%s | %s) & (%s | %s));", lvalue(cell->getPort("\\Y")),
						rvalue(cell->getPort("\\A")), rvalue(cell->getPort("\\B")), rvalue(cell->getPort("\\C")), rvalue(cell->getPort("\\D"))));
				continue;
			}

			if (cell->type[0] == '$')
				log_error("Found currently unsupported cell type %s (%s.%s).\n", log_id(cell->type), log_id(module), log_id(cell));

			f << stringf("    %s : %s;\n", cid(cell->name), cid(cell->type));

			for (auto &conn : cell->connections())
				if (cell->output(conn.first))
					assignments.push_back(stringf("%s := %s.%s;", lvalue(conn.second), cid(cell->name), cid(conn.first)));
				else
					assignments.push_back(stringf("%s.%s := %s;", cid(cell->name), cid(conn.first), rvalue(conn.second)));
		}

		for (Wire *wire : partial_assignment_wires)
		{
			string expr;

			for (int i = 0; i < wire->width; i++)
			{
				if (!expr.empty())
					expr = " :: " + expr;

				if (partial_assignment_bits.count(sigmap(SigBit(wire, i))))
				{
					int width = 1;
					const auto &bit_a = partial_assignment_bits.at(sigmap(SigBit(wire, i)));

					while (i+1 < wire->width)
					{
						SigBit next_bit = sigmap(SigBit(wire, i+1));

						if (!partial_assignment_bits.count(next_bit))
							break;

						const auto &bit_b = partial_assignment_bits.at(next_bit);
						if (strcmp(bit_a.first, bit_b.first))
							break;
						if (bit_a.second+width != bit_b.second)
							break;

						width++, i++;
					}

					expr = stringf("%s[%d:%d]", bit_a.first, bit_a.second+width-1, bit_a.second) + expr;
				}
				else if (sigmap(SigBit(wire, i)).wire == nullptr)
				{
					string bits;
					SigSpec sig = sigmap(SigSpec(wire, i));

					while (i+1 < wire->width) {
						SigBit next_bit = sigmap(SigBit(wire, i+1));
						if (next_bit.wire != nullptr)
							break;
						sig.append(next_bit);
						i++;
					}

					for (int k = GetSize(sig)-1; k >= 0; k--)
						bits += sig[k] == State::S1 ? '1' : '0';

					expr = stringf("0ub%d_%s", GetSize(bits), bits.c_str()) + expr;
				}
				else if (sigmap(SigBit(wire, i)) == SigBit(wire, i))
				{
					int length = 1;

					while (i+1 < wire->width) {
						if (partial_assignment_bits.count(sigmap(SigBit(wire, i+1))))
							break;
						if (sigmap(SigBit(wire, i+1)) != SigBit(wire, i+1))
							break;
						i++, length++;
					}

					expr = stringf("0ub%d_0", length) + expr;
				}
				else
				{
					string bits;
					SigSpec sig = sigmap(SigSpec(wire, i));

					while (i+1 < wire->width) {
						SigBit next_bit = sigmap(SigBit(wire, i+1));
						if (next_bit.wire == nullptr || partial_assignment_bits.count(next_bit))
							break;
						sig.append(next_bit);
						i++;
					}

					expr = rvalue(sig) + expr;
				}
			}

			assignments.push_back(stringf("%s := %s;", cid(wire->name), expr.c_str()));
		}

		if (!assignments.empty()) {
			f << stringf("  ASSIGN\n");
			for (const string &line : assignments)
				f << stringf("    %s\n", line.c_str());
		}

		if (!invarspecs.empty()) {
			for (const string &line : invarspecs)
				f << stringf("  INVARSPEC %s\n", line.c_str());
		}
	}
};

struct SmvBackend : public Backend {
	SmvBackend() : Backend("smv", "write design to SMV file") { }
	virtual void help()
	{
		//   |---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|
		log("\n");
		log("    write_smv [options] [filename]\n");
		log("\n");
		log("Write an SMV description of the current design.\n");
		log("\n");
		log("    -verbose\n");
		log("        this will print the recursive walk used to export the modules.\n");
		log("\n");
		log("    -tpl <template_file>\n");
		log("        use the given template file. the line containing only the token '%%%%'\n");
		log("        is replaced with the regular output of this command.\n");
		log("\n");
		log("THIS COMMAND IS UNDER CONSTRUCTION\n");
		log("\n");
	}
	virtual void execute(std::ostream *&f, std::string filename, std::vector<std::string> args, RTLIL::Design *design)
	{
		std::ifstream template_f;
		bool verbose = false;

		log_header("Executing SMV backend.\n");

		size_t argidx;
		for (argidx = 1; argidx < args.size(); argidx++)
		{
			if (args[argidx] == "-tpl" && argidx+1 < args.size()) {
				template_f.open(args[++argidx]);
				if (template_f.fail())
					log_error("Can't open template file `%s'.\n", args[argidx].c_str());
				continue;
			}
			if (args[argidx] == "-verbose") {
				verbose = true;
				continue;
			}
			break;
		}
		extra_args(f, filename, args, argidx);

		pool<Module*> modules;

		for (auto module : design->modules())
			if (!module->get_bool_attribute("\\blackbox") && !module->has_memories_warn() && !module->has_processes_warn())
				modules.insert(module);

		if (template_f.is_open())
		{
			std::string line;
			while (std::getline(template_f, line))
			{
				int indent = 0;
				while (indent < GetSize(line) && (line[indent] == ' ' || line[indent] == '\t'))
					indent++;

				if (line[indent] == '%')
				{
					vector<string> stmt = split_tokens(line);

					if (GetSize(stmt) == 1 && stmt[0] == "%%")
						break;

					if (GetSize(stmt) == 2 && stmt[0] == "%module")
					{
						Module *module = design->module(RTLIL::escape_id(stmt[1]));
						modules.erase(module);

						if (module == nullptr)
							log_error("Module '%s' not found.\n", stmt[1].c_str());

						*f << stringf("-- SMV description generated by %s\n", yosys_version_str);

						log("Creating SMV representation of module %s.\n", log_id(module));
						SmvWorker worker(module, verbose, *f);
						worker.run();

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

					log_error("Unknown template statement: '%s'", line.c_str() + indent);
				}

				*f << line << std::endl;
			}
		}

		if (!modules.empty())
		{
			*f << stringf("-- SMV description generated by %s\n", yosys_version_str);

			for (auto module : modules) {
				log("Creating SMV representation of module %s.\n", log_id(module));
				SmvWorker worker(module, verbose, *f);
				worker.run();
			}

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

		if (template_f.is_open()) {
			std::string line;
			while (std::getline(template_f, line))
				*f << line << std::endl;
		}
	}
} SmvBackend;

PRIVATE_NAMESPACE_END