yosys/backends/verilog/verilog_backend.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.
 *
 *  ---
 *
 *  A simple and straightforward Verilog backend.
 *
 */

#include "kernel/register.h"
#include "kernel/celltypes.h"
#include "kernel/log.h"
#include "kernel/sigtools.h"
#include "kernel/ff.h"
#include "kernel/mem.h"
#include "kernel/fmt.h"
#include <string>
#include <sstream>
#include <set>
#include <map>

USING_YOSYS_NAMESPACE
PRIVATE_NAMESPACE_BEGIN

bool verbose, norename, noattr, attr2comment, noexpr, nodec, nohex, nostr, extmem, defparam, decimal, siminit, systemverilog, simple_lhs, noparallelcase;
int auto_name_counter, auto_name_offset, auto_name_digits, extmem_counter;
dict<RTLIL::IdString, int> auto_name_map;
std::set<RTLIL::IdString> reg_wires;
std::string auto_prefix, extmem_prefix;

RTLIL::Module *active_module;
dict<RTLIL::SigBit, RTLIL::State> active_initdata;
SigMap active_sigmap;
IdString initial_id;

void reset_auto_counter_id(RTLIL::IdString id, bool may_rename)
{
	const char *str = id.c_str();

	if (*str == '$' && may_rename && !norename)
		auto_name_map[id] = auto_name_counter++;

	if (str[0] != '\\' || str[1] != '_' || str[2] == 0)
		return;

	for (int i = 2; str[i] != 0; i++) {
		if (str[i] == '_' && str[i+1] == 0)
			continue;
		if (str[i] < '0' || str[i] > '9')
			return;
	}

	int num = atoi(str+2);
	if (num >= auto_name_offset)
		auto_name_offset = num + 1;
}

void reset_auto_counter(RTLIL::Module *module)
{
	auto_name_map.clear();
	auto_name_counter = 0;
	auto_name_offset = 0;

	reset_auto_counter_id(module->name, false);

	for (auto w : module->wires())
		reset_auto_counter_id(w->name, true);

	for (auto cell : module->cells()) {
		reset_auto_counter_id(cell->name, true);
		reset_auto_counter_id(cell->type, false);
	}

	for (auto it = module->processes.begin(); it != module->processes.end(); ++it)
		reset_auto_counter_id(it->second->name, false);

	auto_name_digits = 1;
	for (size_t i = 10; i < auto_name_offset + auto_name_map.size(); i = i*10)
		auto_name_digits++;

	if (verbose)
		for (auto it = auto_name_map.begin(); it != auto_name_map.end(); ++it)
			log("  renaming `%s' to `%s_%0*d_'.\n", it->first.c_str(), auto_prefix.c_str(), auto_name_digits, auto_name_offset + it->second);
}

std::string next_auto_id()
{
	return stringf("%s_%0*d_", auto_prefix.c_str(), auto_name_digits, auto_name_offset + auto_name_counter++);
}

std::string id(RTLIL::IdString internal_id, bool may_rename = true)
{
	const char *str = internal_id.c_str();
	bool do_escape = false;

	if (may_rename && auto_name_map.count(internal_id) != 0)
		return stringf("%s_%0*d_", auto_prefix.c_str(), auto_name_digits, auto_name_offset + auto_name_map[internal_id]);

	if (*str == '\\')
		str++;

	if ('0' <= *str && *str <= '9')
		do_escape = true;

	for (int i = 0; str[i]; i++)
	{
		if ('0' <= str[i] && str[i] <= '9')
			continue;
		if ('a' <= str[i] && str[i] <= 'z')
			continue;
		if ('A' <= str[i] && str[i] <= 'Z')
			continue;
		if (str[i] == '_')
			continue;
		do_escape = true;
		break;
	}

	static const pool<string> keywords = {
		// IEEE 1800-2017 Annex B
		"accept_on", "alias", "always", "always_comb", "always_ff", "always_latch", "and", "assert", "assign", "assume", "automatic", "before",
		"begin", "bind", "bins", "binsof", "bit", "break", "buf", "bufif0", "bufif1", "byte", "case", "casex", "casez", "cell", "chandle",
		"checker", "class", "clocking", "cmos", "config", "const", "constraint", "context", "continue", "cover", "covergroup", "coverpoint",
		"cross", "deassign", "default", "defparam", "design", "disable", "dist", "do", "edge", "else", "end", "endcase", "endchecker",
		"endclass", "endclocking", "endconfig", "endfunction", "endgenerate", "endgroup", "endinterface", "endmodule", "endpackage",
		"endprimitive", "endprogram", "endproperty", "endsequence", "endspecify", "endtable", "endtask", "enum", "event", "eventually",
		"expect", "export", "extends", "extern", "final", "first_match", "for", "force", "foreach", "forever", "fork", "forkjoin", "function",
		"generate", "genvar", "global", "highz0", "highz1", "if", "iff", "ifnone", "ignore_bins", "illegal_bins", "implements", "implies",
		"import", "incdir", "include", "initial", "inout", "input", "inside", "instance", "int", "integer", "interconnect", "interface",
		"intersect", "join", "join_any", "join_none", "large", "let", "liblist", "library", "local", "localparam", "logic", "longint",
		"macromodule", "matches", "medium", "modport", "module", "nand", "negedge", "nettype", "new", "nexttime", "nmos", "nor",
		"noshowcancelled", "not", "notif0", "notif1", "null", "or", "output", "package", "packed", "parameter", "pmos", "posedge", "primitive",
		"priority", "program", "property", "protected", "pull0", "pull1", "pulldown", "pullup", "pulsestyle_ondetect", "pulsestyle_onevent",
		"pure", "rand", "randc", "randcase", "randsequence", "rcmos", "real", "realtime", "ref", "reg", "reject_on", "release", "repeat",
		"restrict", "return", "rnmos", "rpmos", "rtran", "rtranif0", "rtranif1", "s_always", "s_eventually", "s_nexttime", "s_until",
		"s_until_with", "scalared", "sequence", "shortint", "shortreal", "showcancelled", "signed", "small", "soft", "solve", "specify",
		"specparam", "static", "string", "strong", "strong0", "strong1", "struct", "super", "supply0", "supply1", "sync_accept_on",
		"sync_reject_on", "table", "tagged", "task", "this", "throughout", "time", "timeprecision", "timeunit", "tran", "tranif0", "tranif1",
		"tri", "tri0", "tri1", "triand", "trior", "trireg", "type", "typedef", "union", "unique", "unique0", "unsigned", "until", "until_with",
		"untyped", "use", "uwire", "var", "vectored", "virtual", "void", "wait", "wait_order", "wand", "weak", "weak0", "weak1", "while",
		"wildcard", "wire", "with", "within", "wor", "xnor", "xor",
	};
	if (keywords.count(str))
		do_escape = true;

	if (do_escape)
		return "\\" + std::string(str) + " ";
	return std::string(str);
}

bool is_reg_wire(RTLIL::SigSpec sig, std::string &reg_name)
{
	if (!sig.is_chunk() || sig.as_chunk().wire == NULL)
		return false;

	RTLIL::SigChunk chunk = sig.as_chunk();

	if (reg_wires.count(chunk.wire->name) == 0)
		return false;

	reg_name = id(chunk.wire->name);
	if (sig.size() != chunk.wire->width) {
		if (sig.size() == 1)
			reg_name += stringf("[%d]", chunk.wire->start_offset +  chunk.offset);
		else if (chunk.wire->upto)
			reg_name += stringf("[%d:%d]", (chunk.wire->width - (chunk.offset + chunk.width - 1) - 1) + chunk.wire->start_offset,
					(chunk.wire->width - chunk.offset - 1) + chunk.wire->start_offset);
		else
			reg_name += stringf("[%d:%d]", chunk.wire->start_offset +  chunk.offset + chunk.width - 1,
					chunk.wire->start_offset +  chunk.offset);
	}

	return true;
}

void dump_const(std::ostream &f, const RTLIL::Const &data, int width = -1, int offset = 0, bool no_decimal = false, bool escape_comment = false)
{
	bool set_signed = (data.flags & RTLIL::CONST_FLAG_SIGNED) != 0;
	if (width < 0)
		width = data.bits.size() - offset;
	if (width == 0) {
		// See IEEE 1364-2005 Clause 5.1.14.
		f << "{0{1'b0}}";
		return;
	}
	if (nostr)
		goto dump_hex;
	if ((data.flags & RTLIL::CONST_FLAG_STRING) == 0 || width != (int)data.bits.size()) {
		if (width == 32 && !no_decimal && !nodec) {
			int32_t val = 0;
			for (int i = offset+width-1; i >= offset; i--) {
				log_assert(i < (int)data.bits.size());
				if (data.bits[i] != State::S0 && data.bits[i] != State::S1)
					goto dump_hex;
				if (data.bits[i] == State::S1)
					val |= 1 << (i - offset);
			}
			if (decimal)
				f << stringf("%d", val);
			else if (set_signed && val < 0)
				f << stringf("-32'sd%u", -val);
			else
				f << stringf("32'%sd%u", set_signed ? "s" : "", val);
		} else {
	dump_hex:
			if (nohex)
				goto dump_bin;
			vector<char> bin_digits, hex_digits;
			for (int i = offset; i < offset+width; i++) {
				log_assert(i < (int)data.bits.size());
				switch (data.bits[i]) {
				case State::S0: bin_digits.push_back('0'); break;
				case State::S1: bin_digits.push_back('1'); break;
				case RTLIL::Sx: bin_digits.push_back('x'); break;
				case RTLIL::Sz: bin_digits.push_back('z'); break;
				case RTLIL::Sa: bin_digits.push_back('?'); break;
				case RTLIL::Sm: log_error("Found marker state in final netlist.");
				}
			}
			if (GetSize(bin_digits) == 0)
				goto dump_bin;
			while (GetSize(bin_digits) % 4 != 0)
				if (bin_digits.back() == '1')
					bin_digits.push_back('0');
				else
					bin_digits.push_back(bin_digits.back());
			for (int i = 0; i < GetSize(bin_digits); i += 4)
			{
				char bit_3 = bin_digits[i+3];
				char bit_2 = bin_digits[i+2];
				char bit_1 = bin_digits[i+1];
				char bit_0 = bin_digits[i+0];
				if (bit_3 == 'x' || bit_2 == 'x' || bit_1 == 'x' || bit_0 == 'x') {
					if (bit_3 != 'x' || bit_2 != 'x' || bit_1 != 'x' || bit_0 != 'x')
						goto dump_bin;
					hex_digits.push_back('x');
					continue;
				}
				if (bit_3 == 'z' || bit_2 == 'z' || bit_1 == 'z' || bit_0 == 'z') {
					if (bit_3 != 'z' || bit_2 != 'z' || bit_1 != 'z' || bit_0 != 'z')
						goto dump_bin;
					hex_digits.push_back('z');
					continue;
				}
				if (bit_3 == '?' || bit_2 == '?' || bit_1 == '?' || bit_0 == '?') {
					if (bit_3 != '?' || bit_2 != '?' || bit_1 != '?' || bit_0 != '?')
						goto dump_bin;
					hex_digits.push_back('?');
					continue;
				}
				int val = 8*(bit_3 - '0') + 4*(bit_2 - '0') + 2*(bit_1 - '0') + (bit_0 - '0');
				hex_digits.push_back(val < 10 ? '0' + val : 'a' + val - 10);
			}
			f << stringf("%d'%sh", width, set_signed ? "s" : "");
			for (int i = GetSize(hex_digits)-1; i >= 0; i--)
				f << hex_digits[i];
		}
		if (0) {
	dump_bin:
			f << stringf("%d'%sb", width, set_signed ? "s" : "");
			if (width == 0)
				f << stringf("0");
			for (int i = offset+width-1; i >= offset; i--) {
				log_assert(i < (int)data.bits.size());
				switch (data.bits[i]) {
				case State::S0: f << stringf("0"); break;
				case State::S1: f << stringf("1"); break;
				case RTLIL::Sx: f << stringf("x"); break;
				case RTLIL::Sz: f << stringf("z"); break;
				case RTLIL::Sa: f << stringf("?"); break;
				case RTLIL::Sm: log_error("Found marker state in final netlist.");
				}
			}
		}
	} else {
		if ((data.flags & RTLIL::CONST_FLAG_REAL) == 0)
			f << stringf("\"");
		std::string str = data.decode_string();
		for (size_t i = 0; i < str.size(); i++) {
			if (str[i] == '\n')
				f << stringf("\\n");
			else if (str[i] == '\t')
				f << stringf("\\t");
			else if (str[i] < 32)
				f << stringf("\\%03o", str[i]);
			else if (str[i] == '"')
				f << stringf("\\\"");
			else if (str[i] == '\\')
				f << stringf("\\\\");
			else if (str[i] == '/' && escape_comment && i > 0 && str[i-1] == '*')
				f << stringf("\\/");
			else
				f << str[i];
		}
		if ((data.flags & RTLIL::CONST_FLAG_REAL) == 0)
			f << stringf("\"");
	}
}

void dump_reg_init(std::ostream &f, SigSpec sig)
{
	Const initval;
	bool gotinit = false;

	for (auto bit : active_sigmap(sig)) {
		if (active_initdata.count(bit)) {
			initval.bits.push_back(active_initdata.at(bit));
			gotinit = true;
		} else {
			initval.bits.push_back(State::Sx);
		}
	}

	if (gotinit) {
		f << " = ";
		dump_const(f, initval);
	}
}

void dump_sigchunk(std::ostream &f, const RTLIL::SigChunk &chunk, bool no_decimal = false)
{
	if (chunk.wire == NULL) {
		dump_const(f, chunk.data, chunk.width, chunk.offset, no_decimal);
	} else {
		if (chunk.width == chunk.wire->width && chunk.offset == 0) {
			f << stringf("%s", id(chunk.wire->name).c_str());
		} else if (chunk.width == 1) {
			if (chunk.wire->upto)
				f << stringf("%s[%d]", id(chunk.wire->name).c_str(), (chunk.wire->width - chunk.offset - 1) + chunk.wire->start_offset);
			else
				f << stringf("%s[%d]", id(chunk.wire->name).c_str(), chunk.offset + chunk.wire->start_offset);
		} else {
			if (chunk.wire->upto)
				f << stringf("%s[%d:%d]", id(chunk.wire->name).c_str(),
						(chunk.wire->width - (chunk.offset + chunk.width - 1) - 1) + chunk.wire->start_offset,
						(chunk.wire->width - chunk.offset - 1) + chunk.wire->start_offset);
			else
				f << stringf("%s[%d:%d]", id(chunk.wire->name).c_str(),
						(chunk.offset + chunk.width - 1) + chunk.wire->start_offset,
						chunk.offset + chunk.wire->start_offset);
		}
	}
}

void dump_sigspec(std::ostream &f, const RTLIL::SigSpec &sig)
{
	if (GetSize(sig) == 0) {
		// See IEEE 1364-2005 Clause 5.1.14.
		f << "{0{1'b0}}";
		return;
	}
	if (sig.is_chunk()) {
		dump_sigchunk(f, sig.as_chunk());
	} else {
		f << stringf("{ ");
		for (auto it = sig.chunks().rbegin(); it != sig.chunks().rend(); ++it) {
			if (it != sig.chunks().rbegin())
				f << stringf(", ");
			dump_sigchunk(f, *it, true);
		}
		f << stringf(" }");
	}
}

void dump_attributes(std::ostream &f, std::string indent, dict<RTLIL::IdString, RTLIL::Const> &attributes, std::string term = "\n", bool modattr = false, bool regattr = false, bool as_comment = false)
{
	if (noattr)
		return;
	if (attr2comment)
		as_comment = true;
	for (auto it = attributes.begin(); it != attributes.end(); ++it) {
		if (it->first == ID::init && regattr) continue;
		f << stringf("%s" "%s %s", indent.c_str(), as_comment ? "/*" : "(*", id(it->first).c_str());
		f << stringf(" = ");
		if (modattr && (it->second == State::S0 || it->second == Const(0)))
			f << stringf(" 0 ");
		else if (modattr && (it->second == State::S1 || it->second == Const(1)))
			f << stringf(" 1 ");
		else
			dump_const(f, it->second, -1, 0, false, as_comment);
		f << stringf(" %s%s", as_comment ? "*/" : "*)", term.c_str());
	}
}

void dump_wire(std::ostream &f, std::string indent, RTLIL::Wire *wire)
{
	dump_attributes(f, indent, wire->attributes, "\n", /*modattr=*/false, /*regattr=*/reg_wires.count(wire->name));
#if 0
	if (wire->port_input && !wire->port_output)
		f << stringf("%s" "input %s", indent.c_str(), reg_wires.count(wire->name) ? "reg " : "");
	else if (!wire->port_input && wire->port_output)
		f << stringf("%s" "output %s", indent.c_str(), reg_wires.count(wire->name) ? "reg " : "");
	else if (wire->port_input && wire->port_output)
		f << stringf("%s" "inout %s", indent.c_str(), reg_wires.count(wire->name) ? "reg " : "");
	else
		f << stringf("%s" "%s ", indent.c_str(), reg_wires.count(wire->name) ? "reg" : "wire");
	if (wire->width != 1)
		f << stringf("[%d:%d] ", wire->width - 1 + wire->start_offset, wire->start_offset);
	f << stringf("%s;\n", id(wire->name).c_str());
#else
	// do not use Verilog-2k "output reg" syntax in Verilog export
	std::string range = "";
	if (wire->width != 1) {
		if (wire->upto)
			range = stringf(" [%d:%d]", wire->start_offset, wire->width - 1 + wire->start_offset);
		else
			range = stringf(" [%d:%d]", wire->width - 1 + wire->start_offset, wire->start_offset);
	}
	if (wire->port_input && !wire->port_output)
		f << stringf("%s" "input%s %s;\n", indent.c_str(), range.c_str(), id(wire->name).c_str());
	if (!wire->port_input && wire->port_output)
		f << stringf("%s" "output%s %s;\n", indent.c_str(), range.c_str(), id(wire->name).c_str());
	if (wire->port_input && wire->port_output)
		f << stringf("%s" "inout%s %s;\n", indent.c_str(), range.c_str(), id(wire->name).c_str());
	if (reg_wires.count(wire->name)) {
		f << stringf("%s" "reg%s %s", indent.c_str(), range.c_str(), id(wire->name).c_str());
		if (wire->attributes.count(ID::init)) {
			f << stringf(" = ");
			dump_const(f, wire->attributes.at(ID::init));
		}
		f << stringf(";\n");
	} else
		f << stringf("%s" "wire%s %s;\n", indent.c_str(), range.c_str(), id(wire->name).c_str());
#endif
}

void dump_memory(std::ostream &f, std::string indent, Mem &mem)
{
	std::string mem_id = id(mem.memid);

	dump_attributes(f, indent, mem.attributes);
	f << stringf("%s" "reg [%d:0] %s [%d:%d];\n", indent.c_str(), mem.width-1, mem_id.c_str(), mem.size+mem.start_offset-1, mem.start_offset);

	// for memory block make something like:
	//  reg [7:0] memid [3:0];
	//  initial begin
	//    memid[0] = ...
	//  end
	if (!mem.inits.empty())
	{
		if (extmem)
		{
			std::string extmem_filename = stringf("%s-%d.mem", extmem_prefix.c_str(), extmem_counter++);

			std::string extmem_filename_esc;
			for (auto c : extmem_filename)
			{
				if (c == '\n')
					extmem_filename_esc += "\\n";
				else if (c == '\t')
					extmem_filename_esc += "\\t";
				else if (c < 32)
					extmem_filename_esc += stringf("\\%03o", c);
				else if (c == '"')
					extmem_filename_esc += "\\\"";
				else if (c == '\\')
					extmem_filename_esc += "\\\\";
				else
					extmem_filename_esc += c;
			}
			f << stringf("%s" "initial $readmemb(\"%s\", %s);\n", indent.c_str(), extmem_filename_esc.c_str(), mem_id.c_str());

			std::ofstream extmem_f(extmem_filename, std::ofstream::trunc);
			if (extmem_f.fail())
				log_error("Can't open file `%s' for writing: %s\n", extmem_filename.c_str(), strerror(errno));
			else
			{
				Const data = mem.get_init_data();
				for (int i=0; i<mem.size; i++)
				{
					RTLIL::Const element = data.extract(i*mem.width, mem.width);
					for (int j=0; j<element.size(); j++)
					{
						switch (element[element.size()-j-1])
						{
							case State::S0: extmem_f << '0'; break;
							case State::S1: extmem_f << '1'; break;
							case State::Sx: extmem_f << 'x'; break;
							case State::Sz: extmem_f << 'z'; break;
							case State::Sa: extmem_f << '_'; break;
							case State::Sm: log_error("Found marker state in final netlist.");
						}
					}
					extmem_f << '\n';
				}
			}
		}
		else
		{
			f << stringf("%s" "initial begin\n", indent.c_str());
			for (auto &init : mem.inits) {
				int words = GetSize(init.data) / mem.width;
				int start = init.addr.as_int();
				for (int i=0; i<words; i++)
				{
					for (int j = 0; j < mem.width; j++)
					{
						if (init.en[j] != State::S1)
							continue;

						int start_j = j, width = 1;

						while (j+1 < mem.width && init.en[j+1] == State::S1)
							j++, width++;

						if (width == mem.width) {
							f << stringf("%s" "  %s[%d] = ", indent.c_str(), mem_id.c_str(), i + start);
						} else {
							f << stringf("%s" "  %s[%d][%d:%d] = ", indent.c_str(), mem_id.c_str(), i + start, j, start_j);
						}
						dump_const(f, init.data.extract(i*mem.width+start_j, width));
						f << stringf(";\n");
					}
				}
			}
			f << stringf("%s" "end\n", indent.c_str());
		}
	}

	// create a map : "edge clk" -> expressions within that clock domain
	dict<std::string, std::vector<std::string>> clk_to_lof_body;
	dict<std::string, std::string> clk_to_arst_cond;
	dict<std::string, std::vector<std::string>> clk_to_arst_body;
	clk_to_lof_body[""] = std::vector<std::string>();
	std::string clk_domain_str;
	// create a list of reg declarations
	std::vector<std::string> lof_reg_declarations;

	// read ports
	for (auto &port : mem.rd_ports)
	{
		if (port.clk_enable)
		{
			{
				std::ostringstream os;
				dump_sigspec(os, port.clk);
				clk_domain_str = stringf("%sedge %s", port.clk_polarity ? "pos" : "neg", os.str().c_str());
				if (port.arst != State::S0) {
					std::ostringstream os2;
					dump_sigspec(os2, port.arst);
					clk_domain_str += stringf(", posedge %s", os2.str().c_str());
					clk_to_arst_cond[clk_domain_str] = os2.str();
				}
			}

			// Decide how to represent the transparency; same idea as Mem::extract_rdff.
			bool trans_use_addr = true;
			for (auto bit : port.transparency_mask)
				if (!bit)
					trans_use_addr = false;

			if (GetSize(mem.wr_ports) == 0)
				trans_use_addr = false;

			if (port.en != State::S1 || port.srst != State::S0 || port.arst != State::S0 || !port.init_value.is_fully_undef())
				trans_use_addr = false;

			if (!trans_use_addr)
			{
				// for clocked read ports make something like:
				//   reg [..] temp_id;
				//   always @(posedge clk)
				//      if (rd_en) temp_id <= array_reg[r_addr];
				//   assign r_data = temp_id;
				std::string temp_id = next_auto_id();
				lof_reg_declarations.push_back( stringf("reg [%d:0] %s;\n", port.data.size() - 1, temp_id.c_str()) );

				bool has_indent = false;

				if (port.arst != State::S0) {
					std::ostringstream os;
					os << stringf("%s <= ", temp_id.c_str());
					dump_sigspec(os, port.arst_value);
					os << ";\n";
					clk_to_arst_body[clk_domain_str].push_back(os.str());
				}

				if (port.srst != State::S0 && !port.ce_over_srst) {
					std::ostringstream os;
					os << stringf("if (");
					dump_sigspec(os, port.srst);
					os << stringf(")\n");
					clk_to_lof_body[clk_domain_str].push_back(os.str());
					std::ostringstream os2;
					os2 << stringf("%s" "%s <= ", indent.c_str(), temp_id.c_str());
					dump_sigspec(os2, port.srst_value);
					os2 << ";\n";
					clk_to_lof_body[clk_domain_str].push_back(os2.str());
					std::ostringstream os3;
					if (port.en == State::S1) {
						os3 << "else begin\n";
					} else {
						os3 << "else if (";
						dump_sigspec(os3, port.en);
						os3 << ") begin\n";
					}
					clk_to_lof_body[clk_domain_str].push_back(os3.str());
					has_indent = true;
				} else if (port.en != State::S1) {
					std::ostringstream os;
					os << stringf("if (");
					dump_sigspec(os, port.en);
					os << stringf(") begin\n");
					clk_to_lof_body[clk_domain_str].push_back(os.str());
					has_indent = true;
				}

				for (int sub = 0; sub < (1 << port.wide_log2); sub++)
				{
					SigSpec addr = port.sub_addr(sub);
					std::ostringstream os;
					if (has_indent)
						os << indent;
					os << temp_id;
					if (port.wide_log2)
						os << stringf("[%d:%d]", (sub + 1) * mem.width - 1, sub * mem.width);
					os << stringf(" <= %s[", mem_id.c_str());
					dump_sigspec(os, addr);
					os << stringf("];\n");
					clk_to_lof_body[clk_domain_str].push_back(os.str());
				}

				for (int i = 0; i < GetSize(mem.wr_ports); i++) {
					auto &wport = mem.wr_ports[i];
					if (!port.transparency_mask[i] && !port.collision_x_mask[i])
						continue;
					int min_wide_log2 = std::min(port.wide_log2, wport.wide_log2);
					int max_wide_log2 = std::max(port.wide_log2, wport.wide_log2);
					bool wide_write = wport.wide_log2 > port.wide_log2;
					for (int sub = 0; sub < (1 << max_wide_log2); sub += (1 << min_wide_log2)) {
						SigSpec raddr = port.addr;
						SigSpec waddr = wport.addr;
						if (wide_write)
							waddr = wport.sub_addr(sub);
						else
							raddr = port.sub_addr(sub);
						int pos = 0;
						int ewidth = mem.width << min_wide_log2;
						int wsub = wide_write ? sub : 0;
						int rsub = wide_write ? 0 : sub;
						while (pos < ewidth) {
							int epos = pos;
							while (epos < ewidth && wport.en[epos + wsub * mem.width] == wport.en[pos + wsub * mem.width])
								epos++;

							std::ostringstream os;
							if (has_indent)
								os << indent;
							os << "if (";
							dump_sigspec(os, wport.en[pos + wsub * mem.width]);
							if (raddr != waddr) {
								os << " && ";
								dump_sigspec(os, raddr);
								os << " == ";
								dump_sigspec(os, waddr);
							}
							os << ")\n";
							clk_to_lof_body[clk_domain_str].push_back(os.str());

							std::ostringstream os2;
							if (has_indent)
								os2 << indent;
							os2 << indent;
							os2 << temp_id;
							if (epos-pos != GetSize(port.data))
								os2 << stringf("[%d:%d]", rsub * mem.width + epos-1, rsub * mem.width + pos);
							os2 << " <= ";
							if (port.transparency_mask[i])
								dump_sigspec(os2, wport.data.extract(wsub * mem.width + pos, epos-pos));
							else
								dump_sigspec(os2, Const(State::Sx, epos - pos));
							os2 << ";\n";
							clk_to_lof_body[clk_domain_str].push_back(os2.str());

							pos = epos;
						}
					}
				}

				if (port.srst != State::S0 && port.ce_over_srst)
				{
					std::ostringstream os;
					if (has_indent)
						os << indent;
					os << stringf("if (");
					dump_sigspec(os, port.srst);
					os << stringf(")\n");
					clk_to_lof_body[clk_domain_str].push_back(os.str());
					std::ostringstream os2;
					if (has_indent)
						os2 << indent;
					os2 << stringf("%s" "%s <= ", indent.c_str(), temp_id.c_str());
					dump_sigspec(os2, port.srst_value);
					os2 << ";\n";
					clk_to_lof_body[clk_domain_str].push_back(os2.str());
				}

				if (has_indent)
					clk_to_lof_body[clk_domain_str].push_back("end\n");

				if (!port.init_value.is_fully_undef())
				{
					std::ostringstream os;
					dump_sigspec(os, port.init_value);
					std::string line = stringf("initial %s = %s;\n", temp_id.c_str(), os.str().c_str());
					clk_to_lof_body[""].push_back(line);
				}

				{
					std::ostringstream os;
					dump_sigspec(os, port.data);
					std::string line = stringf("assign %s = %s;\n", os.str().c_str(), temp_id.c_str());
					clk_to_lof_body[""].push_back(line);
				}
			}
			else
			{
				// for rd-transparent read-ports make something like:
				//   reg [..] temp_id;
				//   always @(posedge clk)
				//     temp_id <= r_addr;
				//   assign r_data = array_reg[temp_id];
				std::string temp_id = next_auto_id();
				lof_reg_declarations.push_back( stringf("reg [%d:0] %s;\n", port.addr.size() - 1 - port.wide_log2, temp_id.c_str()) );
				{
					std::ostringstream os;
					dump_sigspec(os, port.addr.extract_end(port.wide_log2));
					std::string line = stringf("%s <= %s;\n", temp_id.c_str(), os.str().c_str());
					clk_to_lof_body[clk_domain_str].push_back(line);
				}
				for (int sub = 0; sub < (1 << port.wide_log2); sub++)
				{
					std::ostringstream os;
					os << "assign ";
					dump_sigspec(os, port.data.extract(sub * mem.width, mem.width));
					os << stringf(" = %s[", mem_id.c_str());;
					if (port.wide_log2) {
						Const addr_lo;
						for (int i = 0; i < port.wide_log2; i++)
							addr_lo.bits.push_back(State(sub >> i & 1));
						os << "{";
						os << temp_id;
						os << ", ";
						dump_const(os, addr_lo);
						os << "}";
					} else {
						os << temp_id;
					}
					os << "];\n";
					clk_to_lof_body[""].push_back(os.str());
				}
			}
		} else {
			// for non-clocked read-ports make something like:
			//   assign r_data = array_reg[r_addr];
			for (int sub = 0; sub < (1 << port.wide_log2); sub++)
			{
				SigSpec addr = port.sub_addr(sub);

				std::ostringstream os, os2;
				dump_sigspec(os, port.data.extract(sub * mem.width, mem.width));
				dump_sigspec(os2, addr);
				std::string line = stringf("assign %s = %s[%s];\n", os.str().c_str(), mem_id.c_str(), os2.str().c_str());
				clk_to_lof_body[""].push_back(line);
			}
		}
	}

	// Write ports.  Those are messy because we try to preserve priority, as much as we can:
	//
	// 1. We split all ports into several disjoint processes.
	// 2. If a port has priority over another port, the two ports need to share
	//    a process, so that priority can be reconstructed on the other end.
	// 3. We want each process to be as small as possible, to avoid extra
	//    priorities inferred on the other end.
	pool<int> wr_ports_done;
	for (int ridx = 0; ridx < GetSize(mem.wr_ports); ridx++)
	{
		if (wr_ports_done.count(ridx))
			continue;

		auto &root = mem.wr_ports[ridx];

		// Start from a root.
		pool<int> wr_ports_now;
		wr_ports_now.insert(ridx);

		// Transitively fill list of ports in this process by following priority edges.
		while (true)
		{
			bool changed = false;

			for (int i = 0; i < GetSize(mem.wr_ports); i++)
			for (int j = 0; j < i; j++)
			if (mem.wr_ports[i].priority_mask[j])
			{
				if (wr_ports_now.count(i) && !wr_ports_now.count(j)) {
					wr_ports_now.insert(j);
					changed = true;
				}
				if (!wr_ports_now.count(i) && wr_ports_now.count(j)) {
					wr_ports_now.insert(i);
					changed = true;
				}
			}

			if (!changed)
				break;
		}

		if (root.clk_enable) {
			f << stringf("%s" "always%s @(%sedge ", indent.c_str(), systemverilog ? "_ff" : "", root.clk_polarity ? "pos" : "neg");
			dump_sigspec(f, root.clk);
			f << ") begin\n";
		} else {
			f << stringf("%s" "always%s begin\n", indent.c_str(), systemverilog ? "_latch" : " @*");
		}

		for (int pidx = 0; pidx < GetSize(mem.wr_ports); pidx++)
		{
			if (!wr_ports_now.count(pidx))
				continue;
			wr_ports_done.insert(pidx);

			auto &port = mem.wr_ports[pidx];
			log_assert(port.clk_enable == root.clk_enable);
			if (port.clk_enable) {
				log_assert(port.clk == root.clk);
				log_assert(port.clk_polarity == root.clk_polarity);
			}

			//   make something like:
			//   always @(posedge clk)
			//      if (wr_en_bit) memid[w_addr][??] <= w_data[??];
			//   ...
			for (int sub = 0; sub < (1 << port.wide_log2); sub++)
			{
				SigSpec addr = port.sub_addr(sub);
				for (int i = 0; i < mem.width; i++)
				{
					int start_i = i, width = 1;
					SigBit wen_bit = port.en[sub * mem.width + i];

					while (i+1 < mem.width && active_sigmap(port.en[sub * mem.width + i+1]) == active_sigmap(wen_bit))
						i++, width++;

					if (wen_bit == State::S0)
						continue;

					f << stringf("%s%s", indent.c_str(), indent.c_str());
					if (wen_bit != State::S1)
					{
						f << stringf("if (");
						dump_sigspec(f, wen_bit);
						f << stringf(")\n");
						f << stringf("%s%s%s", indent.c_str(), indent.c_str(), indent.c_str());
					}
					f << stringf("%s[", mem_id.c_str());
					dump_sigspec(f, addr);
					if (width == GetSize(port.en))
						f << stringf("] <= ");
					else
						f << stringf("][%d:%d] <= ", i, start_i);
					dump_sigspec(f, port.data.extract(sub * mem.width + start_i, width));
					f << stringf(";\n");
				}
			}
		}

		f << stringf("%s" "end\n", indent.c_str());
	}
	// Output Verilog that looks something like this:
	// reg [..] _3_;
	// always @(posedge CLK2) begin
	//   _3_ <= memory[D1ADDR];
	//   if (A1EN)
	//     memory[A1ADDR] <= A1DATA;
	//   if (A2EN)
	//     memory[A2ADDR] <= A2DATA;
	//   ...
	// end
	// always @(negedge CLK1) begin
	//   if (C1EN)
	//     memory[C1ADDR] <= C1DATA;
	// end
	// ...
	// assign D1DATA = _3_;
	// assign D2DATA <= memory[D2ADDR];

	// the reg ... definitions
	for(auto &reg : lof_reg_declarations)
	{
		f << stringf("%s" "%s", indent.c_str(), reg.c_str());
	}
	// the block of expressions by clock domain
	for(auto &pair : clk_to_lof_body)
	{
		std::string clk_domain = pair.first;
		std::vector<std::string> lof_lines = pair.second;
		if( clk_domain != "")
		{
			f << stringf("%s" "always%s @(%s) begin\n", indent.c_str(), systemverilog ? "_ff" : "", clk_domain.c_str());
			bool has_arst = clk_to_arst_cond.count(clk_domain) != 0;
			if (has_arst) {
				f << stringf("%s%s" "if (%s) begin\n", indent.c_str(), indent.c_str(), clk_to_arst_cond[clk_domain].c_str());
				for(auto &line : clk_to_arst_body[clk_domain])
					f << stringf("%s%s%s" "%s", indent.c_str(), indent.c_str(), indent.c_str(), line.c_str());
				f << stringf("%s%s" "end else begin\n", indent.c_str(), indent.c_str());
				for(auto &line : lof_lines)
					f << stringf("%s%s%s" "%s", indent.c_str(), indent.c_str(), indent.c_str(), line.c_str());
				f << stringf("%s%s" "end\n", indent.c_str(), indent.c_str());
			} else {
				for(auto &line : lof_lines)
					f << stringf("%s%s" "%s", indent.c_str(), indent.c_str(), line.c_str());
			}
			f << stringf("%s" "end\n", indent.c_str());
		}
		else
		{
			// the non-clocked assignments
			for(auto &line : lof_lines)
				f << stringf("%s" "%s", indent.c_str(), line.c_str());
		}
	}
}

void dump_cell_expr_port(std::ostream &f, RTLIL::Cell *cell, std::string port, bool gen_signed = true)
{
	if (gen_signed && cell->parameters.count("\\" + port + "_SIGNED") > 0 && cell->parameters["\\" + port + "_SIGNED"].as_bool()) {
		f << stringf("$signed(");
		dump_sigspec(f, cell->getPort("\\" + port));
		f << stringf(")");
	} else
		dump_sigspec(f, cell->getPort("\\" + port));
}

std::string cellname(RTLIL::Cell *cell)
{
	if (!norename && cell->name[0] == '$' && RTLIL::builtin_ff_cell_types().count(cell->type) && cell->hasPort(ID::Q) && !cell->type.in(ID($ff), ID($_FF_)))
	{
		RTLIL::SigSpec sig = cell->getPort(ID::Q);
		if (GetSize(sig) != 1 || sig.is_fully_const())
			goto no_special_reg_name;

		RTLIL::Wire *wire = sig[0].wire;

		if (wire->name[0] != '\\')
			goto no_special_reg_name;

		std::string cell_name = wire->name.str();

		size_t pos = cell_name.find('[');
		if (pos != std::string::npos)
			cell_name = cell_name.substr(0, pos) + "_reg" + cell_name.substr(pos);
		else
			cell_name = cell_name + "_reg";

		if (wire->width != 1)
			cell_name += stringf("[%d]", wire->start_offset + sig[0].offset);

		if (active_module && active_module->count_id(cell_name) > 0)
				goto no_special_reg_name;

		return id(cell_name);
	}
	else
	{
no_special_reg_name:
		return id(cell->name).c_str();
	}
}

void dump_cell_expr_uniop(std::ostream &f, std::string indent, RTLIL::Cell *cell, std::string op)
{
	f << stringf("%s" "assign ", indent.c_str());
	dump_sigspec(f, cell->getPort(ID::Y));
	f << stringf(" = %s ", op.c_str());
	dump_attributes(f, "", cell->attributes, " ");
	dump_cell_expr_port(f, cell, "A", true);
	f << stringf(";\n");
}

void dump_cell_expr_binop(std::ostream &f, std::string indent, RTLIL::Cell *cell, std::string op)
{
	f << stringf("%s" "assign ", indent.c_str());
	dump_sigspec(f, cell->getPort(ID::Y));
	f << stringf(" = ");
	dump_cell_expr_port(f, cell, "A", true);
	f << stringf(" %s ", op.c_str());
	dump_attributes(f, "", cell->attributes, " ");
	dump_cell_expr_port(f, cell, "B", true);
	f << stringf(";\n");
}

void dump_cell_expr_print(std::ostream &f, std::string indent, const RTLIL::Cell *cell)
{
	Fmt fmt = {};
	fmt.parse_rtlil(cell);
	std::vector<VerilogFmtArg> args = fmt.emit_verilog();

	f << stringf("%s" "$write(", indent.c_str());
	bool first = true;
	for (auto &arg : args) {
		if (first) {
			first = false;
		} else {
			f << ", ";
		}
		switch (arg.type) {
			case VerilogFmtArg::STRING:
				dump_const(f, RTLIL::Const(arg.str));
				break;
			case VerilogFmtArg::INTEGER:
				f << (arg.signed_ ? "$signed(" : "$unsigned(");
				dump_sigspec(f, arg.sig);
				f << ")";
				break;
			case VerilogFmtArg::TIME:
				if (arg.realtime)
					f << "$realtime";
				else
					f << "$time";
				break;
			default: log_abort();
		}
	}
	f << stringf(");\n");
}

bool dump_cell_expr(std::ostream &f, std::string indent, RTLIL::Cell *cell)
{
	if (cell->type == ID($_NOT_)) {
		f << stringf("%s" "assign ", indent.c_str());
		dump_sigspec(f, cell->getPort(ID::Y));
		f << stringf(" = ");
		f << stringf("~");
		dump_attributes(f, "", cell->attributes, " ");
		dump_cell_expr_port(f, cell, "A", false);
		f << stringf(";\n");
		return true;
	}

	if (cell->type.in(ID($_AND_), ID($_NAND_), ID($_OR_), ID($_NOR_), ID($_XOR_), ID($_XNOR_), ID($_ANDNOT_), ID($_ORNOT_))) {
		f << stringf("%s" "assign ", indent.c_str());
		dump_sigspec(f, cell->getPort(ID::Y));
		f << stringf(" = ");
		if (cell->type.in(ID($_NAND_), ID($_NOR_), ID($_XNOR_)))
			f << stringf("~(");
		dump_cell_expr_port(f, cell, "A", false);
		f << stringf(" ");
		if (cell->type.in(ID($_AND_), ID($_NAND_), ID($_ANDNOT_)))
			f << stringf("&");
		if (cell->type.in(ID($_OR_), ID($_NOR_), ID($_ORNOT_)))
			f << stringf("|");
		if (cell->type.in(ID($_XOR_), ID($_XNOR_)))
			f << stringf("^");
		dump_attributes(f, "", cell->attributes, " ");
		f << stringf(" ");
		if (cell->type.in(ID($_ANDNOT_), ID($_ORNOT_)))
			f << stringf("~(");
		dump_cell_expr_port(f, cell, "B", false);
		if (cell->type.in(ID($_NAND_), ID($_NOR_), ID($_XNOR_), ID($_ANDNOT_), ID($_ORNOT_)))
			f << stringf(")");
		f << stringf(";\n");
		return true;
	}

	if (cell->type == ID($_MUX_)) {
		f << stringf("%s" "assign ", indent.c_str());
		dump_sigspec(f, cell->getPort(ID::Y));
		f << stringf(" = ");
		dump_cell_expr_port(f, cell, "S", false);
		f << stringf(" ? ");
		dump_attributes(f, "", cell->attributes, " ");
		dump_cell_expr_port(f, cell, "B", false);
		f << stringf(" : ");
		dump_cell_expr_port(f, cell, "A", false);
		f << stringf(";\n");
		return true;
	}

	if (cell->type == ID($_NMUX_)) {
		f << stringf("%s" "assign ", indent.c_str());
		dump_sigspec(f, cell->getPort(ID::Y));
		f << stringf(" = !(");
		dump_cell_expr_port(f, cell, "S", false);
		f << stringf(" ? ");
		dump_attributes(f, "", cell->attributes, " ");
		dump_cell_expr_port(f, cell, "B", false);
		f << stringf(" : ");
		dump_cell_expr_port(f, cell, "A", false);
		f << stringf(");\n");
		return true;
	}

	if (cell->type.in(ID($_AOI3_), ID($_OAI3_))) {
		f << stringf("%s" "assign ", indent.c_str());
		dump_sigspec(f, cell->getPort(ID::Y));
		f << stringf(" = ~((");
		dump_cell_expr_port(f, cell, "A", false);
		f << stringf(cell->type == ID($_AOI3_) ? " & " : " | ");
		dump_cell_expr_port(f, cell, "B", false);
		f << stringf(cell->type == ID($_AOI3_) ? ") |" : ") &");
		dump_attributes(f, "", cell->attributes, " ");
		f << stringf(" ");
		dump_cell_expr_port(f, cell, "C", false);
		f << stringf(");\n");
		return true;
	}

	if (cell->type.in(ID($_AOI4_), ID($_OAI4_))) {
		f << stringf("%s" "assign ", indent.c_str());
		dump_sigspec(f, cell->getPort(ID::Y));
		f << stringf(" = ~((");
		dump_cell_expr_port(f, cell, "A", false);
		f << stringf(cell->type == ID($_AOI4_) ? " & " : " | ");
		dump_cell_expr_port(f, cell, "B", false);
		f << stringf(cell->type == ID($_AOI4_) ? ") |" : ") &");
		dump_attributes(f, "", cell->attributes, " ");
		f << stringf(" (");
		dump_cell_expr_port(f, cell, "C", false);
		f << stringf(cell->type == ID($_AOI4_) ? " & " : " | ");
		dump_cell_expr_port(f, cell, "D", false);
		f << stringf("));\n");
		return true;
	}

#define HANDLE_UNIOP(_type, _operator) \
	if (cell->type ==_type) { dump_cell_expr_uniop(f, indent, cell, _operator); return true; }
#define HANDLE_BINOP(_type, _operator) \
	if (cell->type ==_type) { dump_cell_expr_binop(f, indent, cell, _operator); return true; }

	HANDLE_UNIOP(ID($not), "~")
	HANDLE_UNIOP(ID($pos), "+")
	HANDLE_UNIOP(ID($neg), "-")

	HANDLE_BINOP(ID($and),  "&")
	HANDLE_BINOP(ID($or),   "|")
	HANDLE_BINOP(ID($xor),  "^")
	HANDLE_BINOP(ID($xnor), "~^")

	HANDLE_UNIOP(ID($reduce_and),  "&")
	HANDLE_UNIOP(ID($reduce_or),   "|")
	HANDLE_UNIOP(ID($reduce_xor),  "^")
	HANDLE_UNIOP(ID($reduce_xnor), "~^")
	HANDLE_UNIOP(ID($reduce_bool), "|")

	HANDLE_BINOP(ID($shl),  "<<")
	HANDLE_BINOP(ID($shr),  ">>")
	HANDLE_BINOP(ID($sshl), "<<<")
	HANDLE_BINOP(ID($sshr), ">>>")

	HANDLE_BINOP(ID($lt),  "<")
	HANDLE_BINOP(ID($le),  "<=")
	HANDLE_BINOP(ID($eq),  "==")
	HANDLE_BINOP(ID($ne),  "!=")
	HANDLE_BINOP(ID($eqx), "===")
	HANDLE_BINOP(ID($nex), "!==")
	HANDLE_BINOP(ID($ge),  ">=")
	HANDLE_BINOP(ID($gt),  ">")

	HANDLE_BINOP(ID($add), "+")
	HANDLE_BINOP(ID($sub), "-")
	HANDLE_BINOP(ID($mul), "*")
	HANDLE_BINOP(ID($div), "/")
	HANDLE_BINOP(ID($mod), "%")
	HANDLE_BINOP(ID($pow), "**")

	HANDLE_UNIOP(ID($logic_not), "!")
	HANDLE_BINOP(ID($logic_and), "&&")
	HANDLE_BINOP(ID($logic_or),  "||")

#undef HANDLE_UNIOP
#undef HANDLE_BINOP

	if (cell->type == ID($divfloor))
	{
		// wire [MAXLEN+1:0] _0_, _1_, _2_;
		// assign _0_ = $signed(A);
		// assign _1_ = $signed(B);
		// assign _2_ = (A[-1] == B[-1]) || A == 0 ? _0_ : $signed(_0_ - (B[-1] ? _1_ + 1 : _1_ - 1));
		// assign Y = $signed(_2_) / $signed(_1_);

		if (cell->getParam(ID::A_SIGNED).as_bool() && cell->getParam(ID::B_SIGNED).as_bool()) {
			SigSpec sig_a = cell->getPort(ID::A);
			SigSpec sig_b = cell->getPort(ID::B);

			std::string buf_a = next_auto_id();
			std::string buf_b = next_auto_id();
			std::string buf_num = next_auto_id();
			int size_a = GetSize(sig_a);
			int size_b = GetSize(sig_b);
			int size_y = GetSize(cell->getPort(ID::Y));
			int size_max = std::max(size_a, std::max(size_b, size_y));

			// intentionally one wider than maximum width
			f << stringf("%s" "wire [%d:0] %s, %s, %s;\n", indent.c_str(), size_max, buf_a.c_str(), buf_b.c_str(), buf_num.c_str());
			f << stringf("%s" "assign %s = ", indent.c_str(), buf_a.c_str());
			dump_cell_expr_port(f, cell, "A", true);
			f << stringf(";\n");
			f << stringf("%s" "assign %s = ", indent.c_str(), buf_b.c_str());
			dump_cell_expr_port(f, cell, "B", true);
			f << stringf(";\n");

			f << stringf("%s" "assign %s = ", indent.c_str(), buf_num.c_str());
			f << stringf("(");
			dump_sigspec(f, sig_a.extract(sig_a.size()-1));
			f << stringf(" == ");
			dump_sigspec(f, sig_b.extract(sig_b.size()-1));
			f << stringf(") || ");
			dump_sigspec(f, sig_a);
			f << stringf(" == 0 ? %s : ", buf_a.c_str());
			f << stringf("$signed(%s - (", buf_a.c_str());
			dump_sigspec(f, sig_b.extract(sig_b.size()-1));
			f << stringf(" ? %s + 1 : %s - 1));\n", buf_b.c_str(), buf_b.c_str());


			f << stringf("%s" "assign ", indent.c_str());
			dump_sigspec(f, cell->getPort(ID::Y));
			f << stringf(" = $signed(%s) / ", buf_num.c_str());
			dump_attributes(f, "", cell->attributes, " ");
			f << stringf("$signed(%s);\n", buf_b.c_str());
			return true;
		} else {
			// same as truncating division
			dump_cell_expr_binop(f, indent, cell, "/");
			return true;
		}
	}

	if (cell->type == ID($modfloor))
	{
		// wire truncated = $signed(A) % $signed(B);
		// assign Y = (A[-1] == B[-1]) || truncated == 0 ? $signed(truncated) : $signed(B) + $signed(truncated);

		if (cell->getParam(ID::A_SIGNED).as_bool() && cell->getParam(ID::B_SIGNED).as_bool()) {
			SigSpec sig_a = cell->getPort(ID::A);
			SigSpec sig_b = cell->getPort(ID::B);

			std::string temp_id = next_auto_id();
			f << stringf("%s" "wire [%d:0] %s = ", indent.c_str(), GetSize(cell->getPort(ID::A))-1, temp_id.c_str());
			dump_cell_expr_port(f, cell, "A", true);
			f << stringf(" %% ");
			dump_attributes(f, "", cell->attributes, " ");
			dump_cell_expr_port(f, cell, "B", true);
			f << stringf(";\n");

			f << stringf("%s" "assign ", indent.c_str());
			dump_sigspec(f, cell->getPort(ID::Y));
			f << stringf(" = (");
			dump_sigspec(f, sig_a.extract(sig_a.size()-1));
			f << stringf(" == ");
			dump_sigspec(f, sig_b.extract(sig_b.size()-1));
			f << stringf(") || %s == 0 ? $signed(%s) : ", temp_id.c_str(), temp_id.c_str());
			dump_cell_expr_port(f, cell, "B", true);
			f << stringf(" + $signed(%s);\n", temp_id.c_str());
			return true;
		} else {
			// same as truncating modulo
			dump_cell_expr_binop(f, indent, cell, "%");
			return true;
		}
	}

	if (cell->type == ID($shift))
	{
		f << stringf("%s" "assign ", indent.c_str());
		dump_sigspec(f, cell->getPort(ID::Y));
		f << stringf(" = ");
		if (cell->getParam(ID::B_SIGNED).as_bool())
		{
			dump_cell_expr_port(f, cell, "B", true);
			f << stringf(" < 0 ? ");
			dump_cell_expr_port(f, cell, "A", true);
			f << stringf(" << - ");
			dump_sigspec(f, cell->getPort(ID::B));
			f << stringf(" : ");
			dump_cell_expr_port(f, cell, "A", true);
			f << stringf(" >> ");
			dump_sigspec(f, cell->getPort(ID::B));
		}
		else
		{
			dump_cell_expr_port(f, cell, "A", true);
			f << stringf(" >> ");
			dump_sigspec(f, cell->getPort(ID::B));
		}
		f << stringf(";\n");
		return true;
	}

	if (cell->type == ID($shiftx))
	{
		std::string temp_id = next_auto_id();
		f << stringf("%s" "wire [%d:0] %s = ", indent.c_str(), GetSize(cell->getPort(ID::A))-1, temp_id.c_str());
		dump_sigspec(f, cell->getPort(ID::A));
		f << stringf(";\n");

		f << stringf("%s" "assign ", indent.c_str());
		dump_sigspec(f, cell->getPort(ID::Y));
		f << stringf(" = %s[", temp_id.c_str());
		if (cell->getParam(ID::B_SIGNED).as_bool())
			f << stringf("$signed(");
		dump_sigspec(f, cell->getPort(ID::B));
		if (cell->getParam(ID::B_SIGNED).as_bool())
			f << stringf(")");
		f << stringf(" +: %d", cell->getParam(ID::Y_WIDTH).as_int());
		f << stringf("];\n");
		return true;
	}

	if (cell->type == ID($mux))
	{
		f << stringf("%s" "assign ", indent.c_str());
		dump_sigspec(f, cell->getPort(ID::Y));
		f << stringf(" = ");
		dump_sigspec(f, cell->getPort(ID::S));
		f << stringf(" ? ");
		dump_attributes(f, "", cell->attributes, " ");
		dump_sigspec(f, cell->getPort(ID::B));
		f << stringf(" : ");
		dump_sigspec(f, cell->getPort(ID::A));
		f << stringf(";\n");
		return true;
	}

	if (cell->type == ID($pmux))
	{
		int width = cell->parameters[ID::WIDTH].as_int();
		int s_width = cell->getPort(ID::S).size();
		std::string func_name = cellname(cell);

		f << stringf("%s" "function [%d:0] %s;\n", indent.c_str(), width-1, func_name.c_str());
		f << stringf("%s" "  input [%d:0] a;\n", indent.c_str(), width-1);
		f << stringf("%s" "  input [%d:0] b;\n", indent.c_str(), s_width*width-1);
		f << stringf("%s" "  input [%d:0] s;\n", indent.c_str(), s_width-1);

		dump_attributes(f, indent + "  ", cell->attributes);
		if (noparallelcase)
			f << stringf("%s" "  case (s)\n", indent.c_str());
		else {
			if (!noattr)
				f << stringf("%s" "  (* parallel_case *)\n", indent.c_str());
			f << stringf("%s" "  casez (s)", indent.c_str());
			f << stringf(noattr ? " // synopsys parallel_case\n" : "\n");
		}

		for (int i = 0; i < s_width; i++)
		{
			f << stringf("%s" "    %d'b", indent.c_str(), s_width);

			for (int j = s_width-1; j >= 0; j--)
				f << stringf("%c", j == i ? '1' : noparallelcase ? '0' : '?');

			f << stringf(":\n");
			f << stringf("%s" "      %s = b[%d:%d];\n", indent.c_str(), func_name.c_str(), (i+1)*width-1, i*width);
		}

		if (noparallelcase) {
			f << stringf("%s" "    %d'b", indent.c_str(), s_width);
			for (int j = s_width-1; j >= 0; j--)
				f << '0';
			f << stringf(":\n");
		} else
			f << stringf("%s" "    default:\n", indent.c_str());
		f << stringf("%s" "      %s = a;\n", indent.c_str(), func_name.c_str());
		if (noparallelcase) {
			f << stringf("%s" "    default:\n", indent.c_str());
			f << stringf("%s" "      %s = %d'bx;\n", indent.c_str(), func_name.c_str(), width);
		}

		f << stringf("%s" "  endcase\n", indent.c_str());
		f << stringf("%s" "endfunction\n", indent.c_str());

		f << stringf("%s" "assign ", indent.c_str());
		dump_sigspec(f, cell->getPort(ID::Y));
		f << stringf(" = %s(", func_name.c_str());
		dump_sigspec(f, cell->getPort(ID::A));
		f << stringf(", ");
		dump_sigspec(f, cell->getPort(ID::B));
		f << stringf(", ");
		dump_sigspec(f, cell->getPort(ID::S));
		f << stringf(");\n");
		return true;
	}

	if (cell->type == ID($tribuf))
	{
		f << stringf("%s" "assign ", indent.c_str());
		dump_sigspec(f, cell->getPort(ID::Y));
		f << stringf(" = ");
		dump_sigspec(f, cell->getPort(ID::EN));
		f << stringf(" ? ");
		dump_sigspec(f, cell->getPort(ID::A));
		f << stringf(" : %d'bz;\n", cell->parameters.at(ID::WIDTH).as_int());
		return true;
	}

	if (cell->type == ID($slice))
	{
		f << stringf("%s" "assign ", indent.c_str());
		dump_sigspec(f, cell->getPort(ID::Y));
		f << stringf(" = ");
		dump_sigspec(f, cell->getPort(ID::A));
		f << stringf(" >> %d;\n", cell->parameters.at(ID::OFFSET).as_int());
		return true;
	}

	if (cell->type == ID($concat))
	{
		f << stringf("%s" "assign ", indent.c_str());
		dump_sigspec(f, cell->getPort(ID::Y));
		f << stringf(" = { ");
		dump_sigspec(f, cell->getPort(ID::B));
		f << stringf(" , ");
		dump_sigspec(f, cell->getPort(ID::A));
		f << stringf(" };\n");
		return true;
	}

	if (cell->type == ID($lut))
	{
		f << stringf("%s" "assign ", indent.c_str());
		dump_sigspec(f, cell->getPort(ID::Y));
		f << stringf(" = ");
		dump_const(f, cell->parameters.at(ID::LUT));
		f << stringf(" >> ");
		dump_attributes(f, "", cell->attributes, " ");
		dump_sigspec(f, cell->getPort(ID::A));
		f << stringf(";\n");
		return true;
	}

	if (RTLIL::builtin_ff_cell_types().count(cell->type))
	{
		FfData ff(nullptr, cell);

		// $ff / $_FF_ cell: not supported.
		if (ff.has_gclk)
			return false;

		std::string reg_name = cellname(cell);
		bool out_is_reg_wire = is_reg_wire(ff.sig_q, reg_name);

		if (!out_is_reg_wire) {
			if (ff.width == 1)
				f << stringf("%s" "reg %s", indent.c_str(), reg_name.c_str());
			else
				f << stringf("%s" "reg [%d:0] %s", indent.c_str(), ff.width-1, reg_name.c_str());
			dump_reg_init(f, ff.sig_q);
			f << ";\n";
		}

		// If the FF has CLR/SET inputs, emit every bit slice separately.
		int chunks = ff.has_sr ? ff.width : 1;
		bool chunky = ff.has_sr && ff.width != 1;

		for (int i = 0; i < chunks; i++)
		{
			SigSpec sig_d, sig_ad;
			Const val_arst, val_srst;
			std::string reg_bit_name, sig_set_name, sig_clr_name, sig_arst_name, sig_aload_name;
			if (chunky) {
				reg_bit_name = stringf("%s[%d]", reg_name.c_str(), i);
				if (ff.has_gclk || ff.has_clk)
					sig_d = ff.sig_d[i];
				if (ff.has_aload)
					sig_ad = ff.sig_ad[i];
			} else {
				reg_bit_name = reg_name;
				sig_d = ff.sig_d;
				sig_ad = ff.sig_ad;
			}
			if (ff.has_arst)
				val_arst = chunky ? ff.val_arst[i] : ff.val_arst;
			if (ff.has_srst)
				val_srst = chunky ? ff.val_srst[i] : ff.val_srst;

			// If there are constants in the sensitivity list, replace them with an intermediate wire
			if (ff.has_clk) {
				if (ff.has_sr) {
					if (ff.sig_set[i].wire == NULL)
					{
						sig_set_name = next_auto_id();
						f << stringf("%s" "wire %s = ", indent.c_str(), sig_set_name.c_str());
						dump_const(f, ff.sig_set[i].data);
						f << stringf(";\n");
					}
					if (ff.sig_clr[i].wire == NULL)
					{
						sig_clr_name = next_auto_id();
						f << stringf("%s" "wire %s = ", indent.c_str(), sig_clr_name.c_str());
						dump_const(f, ff.sig_clr[i].data);
						f << stringf(";\n");
					}
				} else if (ff.has_arst) {
					if (ff.sig_arst[0].wire == NULL)
					{
						sig_arst_name = next_auto_id();
						f << stringf("%s" "wire %s = ", indent.c_str(), sig_arst_name.c_str());
						dump_const(f, ff.sig_arst[0].data);
						f << stringf(";\n");
					}
				} else if (ff.has_aload) {
					if (ff.sig_aload[0].wire == NULL)
					{
						sig_aload_name = next_auto_id();
						f << stringf("%s" "wire %s = ", indent.c_str(), sig_aload_name.c_str());
						dump_const(f, ff.sig_aload[0].data);
						f << stringf(";\n");
					}
				}
			}

			dump_attributes(f, indent, cell->attributes);
			if (ff.has_clk)
			{
				// FFs.
				f << stringf("%s" "always%s @(%sedge ", indent.c_str(), systemverilog ? "_ff" : "", ff.pol_clk ? "pos" : "neg");
				dump_sigspec(f, ff.sig_clk);
				if (ff.has_sr) {
					f << stringf(", %sedge ", ff.pol_set ? "pos" : "neg");
					if (ff.sig_set[i].wire == NULL)
						f << stringf("%s", sig_set_name.c_str());
					else
						dump_sigspec(f, ff.sig_set[i]);

					f << stringf(", %sedge ", ff.pol_clr ? "pos" : "neg");
					if (ff.sig_clr[i].wire == NULL)
						f << stringf("%s", sig_clr_name.c_str());
					else
						dump_sigspec(f, ff.sig_clr[i]);
				} else if (ff.has_arst) {
					f << stringf(", %sedge ", ff.pol_arst ? "pos" : "neg");
					if (ff.sig_arst[0].wire == NULL)
						f << stringf("%s", sig_arst_name.c_str());
					else
						dump_sigspec(f, ff.sig_arst);
				} else if (ff.has_aload) {
					f << stringf(", %sedge ", ff.pol_aload ? "pos" : "neg");
					if (ff.sig_aload[0].wire == NULL)
						f << stringf("%s", sig_aload_name.c_str());
					else
						dump_sigspec(f, ff.sig_aload);
				}
				f << stringf(")\n");

				f << stringf("%s" "  ", indent.c_str());
				if (ff.has_sr) {
					f << stringf("if (%s", ff.pol_clr ? "" : "!");
					if (ff.sig_clr[i].wire == NULL)
						f << stringf("%s", sig_clr_name.c_str());
					else
						dump_sigspec(f, ff.sig_clr[i]);
					f << stringf(") %s <= 1'b0;\n", reg_bit_name.c_str());
					f << stringf("%s" "  else if (%s", indent.c_str(), ff.pol_set ? "" : "!");
					if (ff.sig_set[i].wire == NULL)
						f << stringf("%s", sig_set_name.c_str());
					else
						dump_sigspec(f, ff.sig_set[i]);
					f << stringf(") %s <= 1'b1;\n", reg_bit_name.c_str());
					f << stringf("%s" "  else ", indent.c_str());
				} else if (ff.has_arst) {
					f << stringf("if (%s", ff.pol_arst ? "" : "!");
					if (ff.sig_arst[0].wire == NULL)
						f << stringf("%s", sig_arst_name.c_str());
					else
						dump_sigspec(f, ff.sig_arst);
					f << stringf(") %s <= ", reg_bit_name.c_str());
					dump_sigspec(f, val_arst);
					f << stringf(";\n");
					f << stringf("%s" "  else ", indent.c_str());
				} else if (ff.has_aload) {
					f << stringf("if (%s", ff.pol_aload ? "" : "!");
					if (ff.sig_aload[0].wire == NULL)
						f << stringf("%s", sig_aload_name.c_str());
					else
						dump_sigspec(f, ff.sig_aload);
					f << stringf(") %s <= ", reg_bit_name.c_str());
					dump_sigspec(f, sig_ad);
					f << stringf(";\n");
					f << stringf("%s" "  else ", indent.c_str());
				}

				if (ff.has_srst && ff.has_ce && ff.ce_over_srst) {
					f << stringf("if (%s", ff.pol_ce ? "" : "!");
					dump_sigspec(f, ff.sig_ce);
					f << stringf(")\n");
					f << stringf("%s" "    if (%s", indent.c_str(), ff.pol_srst ? "" : "!");
					dump_sigspec(f, ff.sig_srst);
					f << stringf(") %s <= ", reg_bit_name.c_str());
					dump_sigspec(f, val_srst);
					f << stringf(";\n");
					f << stringf("%s" "    else ", indent.c_str());
				} else {
					if (ff.has_srst) {
						f << stringf("if (%s", ff.pol_srst ? "" : "!");
						dump_sigspec(f, ff.sig_srst);
						f << stringf(") %s <= ", reg_bit_name.c_str());
						dump_sigspec(f, val_srst);
						f << stringf(";\n");
						f << stringf("%s" "  else ", indent.c_str());
					}
					if (ff.has_ce) {
						f << stringf("if (%s", ff.pol_ce ? "" : "!");
						dump_sigspec(f, ff.sig_ce);
						f << stringf(") ");
					}
				}

				f << stringf("%s <= ", reg_bit_name.c_str());
				dump_sigspec(f, sig_d);
				f << stringf(";\n");
			}
			else
			{
				// Latches.
				f << stringf("%s" "always%s\n", indent.c_str(), systemverilog ? "_latch" : " @*");

				f << stringf("%s" "  ", indent.c_str());
				if (ff.has_sr) {
					f << stringf("if (%s", ff.pol_clr ? "" : "!");
					dump_sigspec(f, ff.sig_clr[i]);
					f << stringf(") %s = 1'b0;\n", reg_bit_name.c_str());
					f << stringf("%s" "  else if (%s", indent.c_str(), ff.pol_set ? "" : "!");
					dump_sigspec(f, ff.sig_set[i]);
					f << stringf(") %s = 1'b1;\n", reg_bit_name.c_str());
					if (ff.has_aload)
						f << stringf("%s" "  else ", indent.c_str());
				} else if (ff.has_arst) {
					f << stringf("if (%s", ff.pol_arst ? "" : "!");
					dump_sigspec(f, ff.sig_arst);
					f << stringf(") %s = ", reg_bit_name.c_str());
					dump_sigspec(f, val_arst);
					f << stringf(";\n");
					if (ff.has_aload)
						f << stringf("%s" "  else ", indent.c_str());
				}
				if (ff.has_aload) {
					f << stringf("if (%s", ff.pol_aload ? "" : "!");
					dump_sigspec(f, ff.sig_aload);
					f << stringf(") %s = ", reg_bit_name.c_str());
					dump_sigspec(f, sig_ad);
					f << stringf(";\n");
				}
			}
		}

		if (!out_is_reg_wire) {
			f << stringf("%s" "assign ", indent.c_str());
			dump_sigspec(f, ff.sig_q);
			f << stringf(" = %s;\n", reg_name.c_str());
		}

		return true;
	}

	if (cell->type.in(ID($assert), ID($assume), ID($cover)))
	{
		f << stringf("%s" "always%s if (", indent.c_str(), systemverilog ? "_comb" : " @*");
		dump_sigspec(f, cell->getPort(ID::EN));
		f << stringf(") %s(", cell->type.c_str()+1);
		dump_sigspec(f, cell->getPort(ID::A));
		f << stringf(");\n");
		return true;
	}

	if (cell->type.in(ID($specify2), ID($specify3)))
	{
		f << stringf("%s" "specify\n%s  ", indent.c_str(), indent.c_str());

		SigSpec en = cell->getPort(ID::EN);
		if (en != State::S1) {
			f << stringf("if (");
			dump_sigspec(f, cell->getPort(ID::EN));
			f << stringf(") ");
		}

		f << "(";
		if (cell->type == ID($specify3) && cell->getParam(ID::EDGE_EN).as_bool())
			f << (cell->getParam(ID::EDGE_POL).as_bool() ? "posedge ": "negedge ");

		dump_sigspec(f, cell->getPort(ID::SRC));

		f << " ";
		if (cell->getParam(ID::SRC_DST_PEN).as_bool())
			f << (cell->getParam(ID::SRC_DST_POL).as_bool() ? "+": "-");
		f << (cell->getParam(ID::FULL).as_bool() ? "*> ": "=> ");

		if (cell->type == ID($specify3)) {
			f << "(";
			dump_sigspec(f, cell->getPort(ID::DST));
			f << " ";
			if (cell->getParam(ID::DAT_DST_PEN).as_bool())
				f << (cell->getParam(ID::DAT_DST_POL).as_bool() ? "+": "-");
			f << ": ";
			dump_sigspec(f, cell->getPort(ID::DAT));
			f << ")";
		} else {
			dump_sigspec(f, cell->getPort(ID::DST));
		}

		bool bak_decimal = decimal;
		decimal = 1;

		f << ") = (";
		dump_const(f, cell->getParam(ID::T_RISE_MIN));
		f << ":";
		dump_const(f, cell->getParam(ID::T_RISE_TYP));
		f << ":";
		dump_const(f, cell->getParam(ID::T_RISE_MAX));
		f << ", ";
		dump_const(f, cell->getParam(ID::T_FALL_MIN));
		f << ":";
		dump_const(f, cell->getParam(ID::T_FALL_TYP));
		f << ":";
		dump_const(f, cell->getParam(ID::T_FALL_MAX));
		f << ");\n";

		decimal = bak_decimal;

		f << stringf("%s" "endspecify\n", indent.c_str());
		return true;
	}

	if (cell->type == ID($specrule))
	{
		f << stringf("%s" "specify\n%s  ", indent.c_str(), indent.c_str());

		IdString spec_type = cell->getParam(ID::TYPE).decode_string();
		f << stringf("%s(", spec_type.c_str());

		if (cell->getParam(ID::SRC_PEN).as_bool())
			f << (cell->getParam(ID::SRC_POL).as_bool() ? "posedge ": "negedge ");
		dump_sigspec(f, cell->getPort(ID::SRC));

		if (cell->getPort(ID::SRC_EN) != State::S1) {
			f << " &&& ";
			dump_sigspec(f, cell->getPort(ID::SRC_EN));
		}

		f << ", ";
		if (cell->getParam(ID::DST_PEN).as_bool())
			f << (cell->getParam(ID::DST_POL).as_bool() ? "posedge ": "negedge ");
		dump_sigspec(f, cell->getPort(ID::DST));

		if (cell->getPort(ID::DST_EN) != State::S1) {
			f << " &&& ";
			dump_sigspec(f, cell->getPort(ID::DST_EN));
		}

		bool bak_decimal = decimal;
		decimal = 1;

		f << ", ";
		dump_const(f, cell->getParam(ID::T_LIMIT_MIN));
		f << ": ";
		dump_const(f, cell->getParam(ID::T_LIMIT_TYP));
		f << ": ";
		dump_const(f, cell->getParam(ID::T_LIMIT_MAX));

		if (spec_type.in(ID($setuphold), ID($recrem), ID($fullskew))) {
			f << ", ";
			dump_const(f, cell->getParam(ID::T_LIMIT2_MIN));
			f << ": ";
			dump_const(f, cell->getParam(ID::T_LIMIT2_TYP));
			f << ": ";
			dump_const(f, cell->getParam(ID::T_LIMIT2_MAX));
		}

		f << ");\n";
		decimal = bak_decimal;

		f << stringf("%s" "endspecify\n", indent.c_str());
		return true;
	}

	if (cell->type == ID($print))
	{
		// Sync $print cells are accumulated and handled in dump_module.
		if (cell->getParam(ID::TRG_ENABLE).as_bool())
			return true;

		f << stringf("%s" "always @*\n", indent.c_str());

		f << stringf("%s" "  if (", indent.c_str());
		dump_sigspec(f, cell->getPort(ID::EN));
		f << stringf(")\n");

		dump_cell_expr_print(f, indent + "    ", cell);
		return true;
	}

	// FIXME: $fsm

	return false;
}

void dump_cell(std::ostream &f, std::string indent, RTLIL::Cell *cell)
{
	// Handled by dump_memory
	if (cell->is_mem_cell())
		return;

	if (cell->type[0] == '$' && !noexpr) {
		if (dump_cell_expr(f, indent, cell))
			return;
	}

	dump_attributes(f, indent, cell->attributes);
	f << stringf("%s" "%s", indent.c_str(), id(cell->type, false).c_str());

	if (!defparam && cell->parameters.size() > 0) {
		f << stringf(" #(");
		for (auto it = cell->parameters.begin(); it != cell->parameters.end(); ++it) {
			if (it != cell->parameters.begin())
				f << stringf(",");
			f << stringf("\n%s  .%s(", indent.c_str(), id(it->first).c_str());
			dump_const(f, it->second);
			f << stringf(")");
		}
		f << stringf("\n%s" ")", indent.c_str());
	}

	std::string cell_name = cellname(cell);
	if (cell_name != id(cell->name))
		f << stringf(" %s /* %s */ (", cell_name.c_str(), id(cell->name).c_str());
	else
		f << stringf(" %s (", cell_name.c_str());

	bool first_arg = true;
	std::set<RTLIL::IdString> numbered_ports;
	for (int i = 1; true; i++) {
		char str[16];
		snprintf(str, 16, "$%d", i);
		for (auto it = cell->connections().begin(); it != cell->connections().end(); ++it) {
			if (it->first != str)
				continue;
			if (!first_arg)
				f << stringf(",");
			first_arg = false;
			f << stringf("\n%s  ", indent.c_str());
			dump_sigspec(f, it->second);
			numbered_ports.insert(it->first);
			goto found_numbered_port;
		}
		break;
	found_numbered_port:;
	}
	for (auto it = cell->connections().begin(); it != cell->connections().end(); ++it) {
		if (numbered_ports.count(it->first))
			continue;
		if (!first_arg)
			f << stringf(",");
		first_arg = false;
		f << stringf("\n%s  .%s(", indent.c_str(), id(it->first).c_str());
		if (it->second.size() > 0)
			dump_sigspec(f, it->second);
		f << stringf(")");
	}
	f << stringf("\n%s" ");\n", indent.c_str());

	if (defparam && cell->parameters.size() > 0) {
		for (auto it = cell->parameters.begin(); it != cell->parameters.end(); ++it) {
			f << stringf("%sdefparam %s.%s = ", indent.c_str(), cell_name.c_str(), id(it->first).c_str());
			dump_const(f, it->second);
			f << stringf(";\n");
		}
	}

	if (siminit && RTLIL::builtin_ff_cell_types().count(cell->type) && cell->hasPort(ID::Q) && !cell->type.in(ID($ff), ID($_FF_))) {
		std::stringstream ss;
		dump_reg_init(ss, cell->getPort(ID::Q));
		if (!ss.str().empty()) {
			f << stringf("%sinitial %s.Q", indent.c_str(), cell_name.c_str());
			f << ss.str();
			f << ";\n";
		}
	}
}

void dump_sync_print(std::ostream &f, std::string indent, const RTLIL::SigSpec &trg, const RTLIL::Const &polarity, std::vector<const RTLIL::Cell*> &cells)
{
	f << stringf("%s" "always @(", indent.c_str());
	for (int i = 0; i < trg.size(); i++) {
		if (i != 0)
			f << " or ";
		if (polarity[i])
			f << "posedge ";
		else
			f << "negedge ";
		dump_sigspec(f, trg[i]);
	}
	f << ") begin\n";

	std::sort(cells.begin(), cells.end(), [](const RTLIL::Cell *a, const RTLIL::Cell *b) {
		return a->getParam(ID::PRIORITY).as_int() > b->getParam(ID::PRIORITY).as_int();
	});
	for (auto cell : cells) {
		f << stringf("%s" "  if (", indent.c_str());
		dump_sigspec(f, cell->getPort(ID::EN));
		f << stringf(")\n");

		dump_cell_expr_print(f, indent + "    ", cell);
	}

	f << stringf("%s" "end\n", indent.c_str());
}

void dump_conn(std::ostream &f, std::string indent, const RTLIL::SigSpec &left, const RTLIL::SigSpec &right)
{
	if (simple_lhs) {
		int offset = 0;
		for (auto &chunk : left.chunks()) {
			f << stringf("%s" "assign ", indent.c_str());
			dump_sigspec(f, chunk);
			f << stringf(" = ");
			dump_sigspec(f, right.extract(offset, GetSize(chunk)));
			f << stringf(";\n");
			offset += GetSize(chunk);
		}
	} else {
		f << stringf("%s" "assign ", indent.c_str());
		dump_sigspec(f, left);
		f << stringf(" = ");
		dump_sigspec(f, right);
		f << stringf(";\n");
	}
}

void dump_proc_switch(std::ostream &f, std::string indent, RTLIL::SwitchRule *sw);

void dump_case_body(std::ostream &f, std::string indent, RTLIL::CaseRule *cs, bool omit_trailing_begin = false)
{
	int number_of_stmts = cs->switches.size() + cs->actions.size();

	if (!omit_trailing_begin && number_of_stmts >= 2)
		f << stringf("%s" "begin\n", indent.c_str());

	for (auto it = cs->actions.begin(); it != cs->actions.end(); ++it) {
		if (it->first.size() == 0)
			continue;
		f << stringf("%s  ", indent.c_str());
		dump_sigspec(f, it->first);
		f << stringf(" = ");
		dump_sigspec(f, it->second);
		f << stringf(";\n");
	}

	for (auto it = cs->switches.begin(); it != cs->switches.end(); ++it)
		dump_proc_switch(f, indent + "  ", *it);

	if (!omit_trailing_begin && number_of_stmts == 0)
		f << stringf("%s  /* empty */;\n", indent.c_str());

	if (omit_trailing_begin || number_of_stmts >= 2)
		f << stringf("%s" "end\n", indent.c_str());
}

bool dump_proc_switch_ifelse(std::ostream &f, std::string indent, RTLIL::SwitchRule *sw)
{
	for (auto it = sw->cases.begin(); it != sw->cases.end(); ++it) {
		if ((*it)->compare.size() == 0) {
			break;
		} else if ((*it)->compare.size() == 1) {
			int case_index = it - sw->cases.begin();
			SigSpec compare = (*it)->compare.at(0);
			if (case_index >= compare.size())
				return false;
			if (compare[case_index] != State::S1)
				return false;
			for (int bit_index = 0; bit_index < compare.size(); bit_index++)
				if (bit_index != case_index && compare[bit_index] != State::Sa)
					return false;
		} else {
			return false;
		}
	}

	f << indent;
	auto sig_it = sw->signal.begin();
	for (auto it = sw->cases.begin(); it != sw->cases.end(); ++it, ++sig_it) {
		bool had_newline = true;
		if (it != sw->cases.begin()) {
			if ((*it)->compare.empty()) {
				f << indent << "else\n";
				had_newline = true;
			} else {
				f << indent << "else ";
				had_newline = false;
			}
		}
		if (!(*it)->compare.empty()) {
			if (!(*it)->attributes.empty()) {
				if (!had_newline)
					f << "\n" << indent;
				dump_attributes(f, "", (*it)->attributes, "\n" + indent);
			}
			f << stringf("if (");
			dump_sigspec(f, *sig_it);
			f << stringf(")\n");
		}
		dump_case_body(f, indent, *it);
		if ((*it)->compare.empty())
			break;
	}
	return true;
}

void dump_proc_switch(std::ostream &f, std::string indent, RTLIL::SwitchRule *sw)
{
	if (sw->signal.size() == 0) {
		f << stringf("%s" "begin\n", indent.c_str());
		for (auto it = sw->cases.begin(); it != sw->cases.end(); ++it) {
			if ((*it)->compare.size() == 0)
				dump_case_body(f, indent + "  ", *it);
		}
		f << stringf("%s" "end\n", indent.c_str());
		return;
	}

	if (dump_proc_switch_ifelse(f, indent, sw))
		return;

	dump_attributes(f, indent, sw->attributes);
	f << stringf("%s" "casez (", indent.c_str());
	dump_sigspec(f, sw->signal);
	f << stringf(")\n");

	for (auto it = sw->cases.begin(); it != sw->cases.end(); ++it) {
		bool got_default = false;
		dump_attributes(f, indent + "  ", (*it)->attributes, "\n", /*modattr=*/false, /*regattr=*/false, /*as_comment=*/true);
		if ((*it)->compare.size() == 0) {
			f << stringf("%s  default", indent.c_str());
			got_default = true;
		} else {
			f << stringf("%s  ", indent.c_str());
			for (size_t i = 0; i < (*it)->compare.size(); i++) {
				if (i > 0)
					f << stringf(", ");
				dump_sigspec(f, (*it)->compare[i]);
			}
		}
		f << stringf(":\n");
		dump_case_body(f, indent + "    ", *it);

		if (got_default) {
			// If we followed up the default with more cases the Verilog
			// semantics would be to match those *before* the default, but
			// the RTLIL semantics are to match those *after* the default
			// (so they can never be selected). Exit now.
			break;
		}
	}

	if (sw->cases.empty()) {
		// Verilog does not allow empty cases.
		f << stringf("%s  default: ;\n", indent.c_str());
	}

	f << stringf("%s" "endcase\n", indent.c_str());
}

void case_body_find_regs(RTLIL::CaseRule *cs)
{
	for (auto it = cs->switches.begin(); it != cs->switches.end(); ++it)
	for (auto it2 = (*it)->cases.begin(); it2 != (*it)->cases.end(); it2++)
		case_body_find_regs(*it2);

	for (auto it = cs->actions.begin(); it != cs->actions.end(); ++it) {
		for (auto &c : it->first.chunks())
			if (c.wire != NULL)
				reg_wires.insert(c.wire->name);
	}
}

void dump_process(std::ostream &f, std::string indent, RTLIL::Process *proc, bool find_regs = false)
{
	if (find_regs) {
		case_body_find_regs(&proc->root_case);
		for (auto it = proc->syncs.begin(); it != proc->syncs.end(); ++it)
		for (auto it2 = (*it)->actions.begin(); it2 != (*it)->actions.end(); it2++) {
			for (auto &c : it2->first.chunks())
				if (c.wire != NULL)
					reg_wires.insert(c.wire->name);
		}
		return;
	}

	f << stringf("%s" "always%s begin\n", indent.c_str(), systemverilog ? "_comb" : " @*");
	if (!systemverilog)
		f << indent + "  " << "if (" << id(initial_id) << ") begin end\n";
	dump_case_body(f, indent, &proc->root_case, true);

	std::string backup_indent = indent;

	for (size_t i = 0; i < proc->syncs.size(); i++)
	{
		RTLIL::SyncRule *sync = proc->syncs[i];
		indent = backup_indent;

		if (sync->type == RTLIL::STa) {
			f << stringf("%s" "always%s begin\n", indent.c_str(), systemverilog ? "_comb" : " @*");
		} else if (sync->type == RTLIL::STi) {
			f << stringf("%s" "initial begin\n", indent.c_str());
		} else {
			f << stringf("%s" "always%s @(", indent.c_str(), systemverilog ? "_ff" : "");
			if (sync->type == RTLIL::STp || sync->type == RTLIL::ST1)
				f << stringf("posedge ");
			if (sync->type == RTLIL::STn || sync->type == RTLIL::ST0)
				f << stringf("negedge ");
			dump_sigspec(f, sync->signal);
			f << stringf(") begin\n");
		}
		std::string ends = indent + "end\n";
		indent += "  ";

		if (sync->type == RTLIL::ST0 || sync->type == RTLIL::ST1) {
			f << stringf("%s" "if (%s", indent.c_str(), sync->type == RTLIL::ST0 ? "!" : "");
			dump_sigspec(f, sync->signal);
			f << stringf(") begin\n");
			ends = indent + "end\n" + ends;
			indent += "  ";
		}

		if (sync->type == RTLIL::STp || sync->type == RTLIL::STn) {
			for (size_t j = 0; j < proc->syncs.size(); j++) {
				RTLIL::SyncRule *sync2 = proc->syncs[j];
				if (sync2->type == RTLIL::ST0 || sync2->type == RTLIL::ST1) {
					f << stringf("%s" "if (%s", indent.c_str(), sync2->type == RTLIL::ST1 ? "!" : "");
					dump_sigspec(f, sync2->signal);
					f << stringf(") begin\n");
					ends = indent + "end\n" + ends;
					indent += "  ";
				}
			}
		}

		for (auto it = sync->actions.begin(); it != sync->actions.end(); ++it) {
			if (it->first.size() == 0)
				continue;
			f << stringf("%s  ", indent.c_str());
			dump_sigspec(f, it->first);
			f << stringf(" <= ");
			dump_sigspec(f, it->second);
			f << stringf(";\n");
		}

		f << stringf("%s", ends.c_str());
	}
}

void dump_module(std::ostream &f, std::string indent, RTLIL::Module *module)
{
	std::map<std::pair<RTLIL::SigSpec, RTLIL::Const>, std::vector<const RTLIL::Cell*>> sync_print_cells;

	reg_wires.clear();
	reset_auto_counter(module);
	active_module = module;
	active_sigmap.set(module);
	active_initdata.clear();

	for (auto wire : module->wires())
		if (wire->attributes.count(ID::init)) {
			SigSpec sig = active_sigmap(wire);
			Const val = wire->attributes.at(ID::init);
			for (int i = 0; i < GetSize(sig) && i < GetSize(val); i++)
				if (val[i] == State::S0 || val[i] == State::S1)
					active_initdata[sig[i]] = val[i];
		}

	if (!module->processes.empty())
		log_warning("Module %s contains unmapped RTLIL processes. RTLIL processes\n"
				"can't always be mapped directly to Verilog always blocks. Unintended\n"
				"changes in simulation behavior are possible! Use \"proc\" to convert\n"
				"processes to logic networks and registers.\n", log_id(module));

	f << stringf("\n");
	for (auto it = module->processes.begin(); it != module->processes.end(); ++it)
		dump_process(f, indent + "  ", it->second, true);

	if (!noexpr)
	{
		std::set<std::pair<RTLIL::Wire*,int>> reg_bits;
		for (auto cell : module->cells())
		{
			if (cell->type == ID($print) && cell->getParam(ID::TRG_ENABLE).as_bool()) {
				sync_print_cells[make_pair(cell->getPort(ID::TRG), cell->getParam(ID::TRG_POLARITY))].push_back(cell);
				continue;
			}

			if (!RTLIL::builtin_ff_cell_types().count(cell->type) || !cell->hasPort(ID::Q) || cell->type.in(ID($ff), ID($_FF_)))
				continue;

			RTLIL::SigSpec sig = cell->getPort(ID::Q);

			if (sig.is_chunk()) {
				RTLIL::SigChunk chunk = sig.as_chunk();
				if (chunk.wire != NULL)
					for (int i = 0; i < chunk.width; i++)
						reg_bits.insert(std::pair<RTLIL::Wire*,int>(chunk.wire, chunk.offset+i));
			}
		}
		for (auto wire : module->wires())
		{
			for (int i = 0; i < wire->width; i++)
				if (reg_bits.count(std::pair<RTLIL::Wire*,int>(wire, i)) == 0)
					goto this_wire_aint_reg;
			if (wire->width)
				reg_wires.insert(wire->name);
		this_wire_aint_reg:;
		}
	}

	dump_attributes(f, indent, module->attributes, "\n", /*modattr=*/true);
	f << stringf("%s" "module %s(", indent.c_str(), id(module->name, false).c_str());
	bool keep_running = true;
	int cnt = 0;
	for (int port_id = 1; keep_running; port_id++) {
		keep_running = false;
		for (auto wire : module->wires()) {
			if (wire->port_id == port_id) {
				if (port_id != 1)
					f << stringf(", ");
				f << stringf("%s", id(wire->name).c_str());
				keep_running = true;
				if (cnt==20) { f << stringf("\n"); cnt = 0; } else cnt++;
				continue;
			}
		}
	}
	f << stringf(");\n");
	if (!systemverilog && !module->processes.empty()) {
		initial_id = NEW_ID;
		f << indent + "  " << "reg " << id(initial_id) << " = 0;\n";
	}

	for (auto w : module->wires())
		dump_wire(f, indent + "  ", w);

	for (auto &mem : Mem::get_all_memories(module))
		dump_memory(f, indent + "  ", mem);

	for (auto cell : module->cells())
		dump_cell(f, indent + "  ", cell);

	for (auto &it : sync_print_cells)
		dump_sync_print(f, indent + "  ", it.first.first, it.first.second, it.second);

	for (auto it = module->processes.begin(); it != module->processes.end(); ++it)
		dump_process(f, indent + "  ", it->second);

	for (auto it = module->connections().begin(); it != module->connections().end(); ++it)
		dump_conn(f, indent + "  ", it->first, it->second);

	f << stringf("%s" "endmodule\n", indent.c_str());
	active_module = NULL;
	active_sigmap.clear();
	active_initdata.clear();
}

struct VerilogBackend : public Backend {
	VerilogBackend() : Backend("verilog", "write design to Verilog file") { }
	void help() override
	{
		//   |---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|
		log("\n");
		log("    write_verilog [options] [filename]\n");
		log("\n");
		log("Write the current design to a Verilog file.\n");
		log("\n");
		log("    -sv\n");
		log("        with this option, SystemVerilog constructs like always_comb are used\n");
		log("\n");
		log("    -norename\n");
		log("        without this option all internal object names (the ones with a dollar\n");
		log("        instead of a backslash prefix) are changed to short names in the\n");
		log("        format '_<number>_'.\n");
		log("\n");
		log("    -renameprefix <prefix>\n");
		log("        insert this prefix in front of auto-generated instance names\n");
		log("\n");
		log("    -noattr\n");
		log("        with this option no attributes are included in the output\n");
		log("\n");
		log("    -attr2comment\n");
		log("        with this option attributes are included as comments in the output\n");
		log("\n");
		log("    -noexpr\n");
		log("        without this option all internal cells are converted to Verilog\n");
		log("        expressions.\n");
		log("\n");
		log("    -noparallelcase\n");
		log("        With this option no parallel_case attributes are used. Instead, a case\n");
		log("        statement that assigns don't-care values for priority dependent inputs\n");
		log("        is generated.\n");
		log("\n");
		log("    -siminit\n");
		log("        add initial statements with hierarchical refs to initialize FFs when\n");
		log("        in -noexpr mode.\n");
		log("\n");
		log("    -nodec\n");
		log("        32-bit constant values are by default dumped as decimal numbers,\n");
		log("        not bit pattern. This option deactivates this feature and instead\n");
		log("        will write out all constants in binary.\n");
		log("\n");
		log("    -decimal\n");
		log("        dump 32-bit constants in decimal and without size and radix\n");
		log("\n");
		log("    -nohex\n");
		log("        constant values that are compatible with hex output are usually\n");
		log("        dumped as hex values. This option deactivates this feature and\n");
		log("        instead will write out all constants in binary.\n");
		log("\n");
		log("    -nostr\n");
		log("        Parameters and attributes that are specified as strings in the\n");
		log("        original input will be output as strings by this back-end. This\n");
		log("        deactivates this feature and instead will write string constants\n");
		log("        as binary numbers.\n");
		log("\n");
		log("    -simple-lhs\n");
		log("        Connection assignments with simple left hand side without\n");
		log("        concatenations.\n");
		log("\n");
		log("    -extmem\n");
		log("        instead of initializing memories using assignments to individual\n");
		log("        elements, use the '$readmemh' function to read initialization data\n");
		log("        from a file. This data is written to a file named by appending\n");
		log("        a sequential index to the Verilog filename and replacing the extension\n");
		log("        with '.mem', e.g. 'write_verilog -extmem foo.v' writes 'foo-1.mem',\n");
		log("        'foo-2.mem' and so on.\n");
		log("\n");
		log("    -defparam\n");
		log("        use 'defparam' statements instead of the Verilog-2001 syntax for\n");
		log("        cell parameters.\n");
		log("\n");
		log("    -blackboxes\n");
		log("        usually modules with the 'blackbox' attribute are ignored. with\n");
		log("        this option set only the modules with the 'blackbox' attribute\n");
		log("        are written to the output file.\n");
		log("\n");
		log("    -selected\n");
		log("        only write selected modules. modules must be selected entirely or\n");
		log("        not at all.\n");
		log("\n");
		log("    -v\n");
		log("        verbose output (print new names of all renamed wires and cells)\n");
		log("\n");
		log("Note that RTLIL processes can't always be mapped directly to Verilog\n");
		log("always blocks. This frontend should only be used to export an RTLIL\n");
		log("netlist, i.e. after the \"proc\" pass has been used to convert all\n");
		log("processes to logic networks and registers. A warning is generated when\n");
		log("this command is called on a design with RTLIL processes.\n");
		log("\n");
	}
	void execute(std::ostream *&f, std::string filename, std::vector<std::string> args, RTLIL::Design *design) override
	{
		log_header(design, "Executing Verilog backend.\n");

		verbose = false;
		norename = false;
		noattr = false;
		attr2comment = false;
		noexpr = false;
		nodec = false;
		nohex = false;
		nostr = false;
		extmem = false;
		defparam = false;
		decimal = false;
		siminit = false;
		simple_lhs = false;
		noparallelcase = false;
		auto_prefix = "";

		bool blackboxes = false;
		bool selected = false;

		auto_name_map.clear();
		reg_wires.clear();

		size_t argidx;
		for (argidx = 1; argidx < args.size(); argidx++) {
			std::string arg = args[argidx];
			if (arg == "-sv") {
				systemverilog = true;
				continue;
			}
			if (arg == "-norename") {
				norename = true;
				continue;
			}
			if (arg == "-renameprefix" && argidx+1 < args.size()) {
				auto_prefix = args[++argidx];
				continue;
			}
			if (arg == "-noattr") {
				noattr = true;
				continue;
			}
			if (arg == "-attr2comment") {
				attr2comment = true;
				continue;
			}
			if (arg == "-noexpr") {
				noexpr = true;
				continue;
			}
			if (arg == "-noparallelcase") {
				noparallelcase = true;
				continue;
			}
			if (arg == "-nodec") {
				nodec = true;
				continue;
			}
			if (arg == "-nohex") {
				nohex = true;
				continue;
			}
			if (arg == "-nostr") {
				nostr = true;
				continue;
			}
			if (arg == "-extmem") {
				extmem = true;
				extmem_counter = 1;
				continue;
			}
			if (arg == "-defparam") {
				defparam = true;
				continue;
			}
			if (arg == "-decimal") {
				decimal = true;
				continue;
			}
			if (arg == "-siminit") {
				siminit = true;
				continue;
			}
			if (arg == "-blackboxes") {
				blackboxes = true;
				continue;
			}
			if (arg == "-selected") {
				selected = true;
				continue;
			}
			if (arg == "-simple-lhs") {
				simple_lhs = true;
				continue;
			}
			if (arg == "-v") {
				verbose = true;
				continue;
			}
			break;
		}
		extra_args(f, filename, args, argidx);
		if (extmem)
		{
			if (filename == "<stdout>")
				log_cmd_error("Option -extmem must be used with a filename.\n");
			extmem_prefix = filename.substr(0, filename.rfind('.'));
		}

		log_push();
		if (!noexpr) {
			Pass::call(design, "bmuxmap");
			Pass::call(design, "demuxmap");
		}
		Pass::call(design, "clean_zerowidth");
		log_pop();

		design->sort();

		*f << stringf("/* Generated by %s */\n", yosys_version_str);
		for (auto module : design->modules()) {
			if (module->get_blackbox_attribute() != blackboxes)
				continue;
			if (selected && !design->selected_whole_module(module->name)) {
				if (design->selected_module(module->name))
					log_cmd_error("Can't handle partially selected module %s!\n", log_id(module->name));
				continue;
			}
			log("Dumping module `%s'.\n", module->name.c_str());
			dump_module(*f, "", module);
		}

		auto_name_map.clear();
		reg_wires.clear();
	}
} VerilogBackend;

PRIVATE_NAMESPACE_END