yosys/passes/fsm/fsm_detect.cc

/*
 *  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/log.h"
#include "kernel/register.h"
#include "kernel/sigtools.h"
#include "kernel/consteval.h"
#include "kernel/celltypes.h"
#include "fsmdata.h"

static RTLIL::Module *module;
static SigMap assign_map;
typedef std::pair<RTLIL::Cell*,std::string> sig2driver_entry_t;
static SigSet<sig2driver_entry_t> sig2driver, sig2user;
static std::set<RTLIL::Cell*> muxtree_cells;
static SigPool sig_at_port;

static bool check_state_mux_tree(RTLIL::SigSpec old_sig, RTLIL::SigSpec sig, SigPool &recursion_monitor)
{
	if (sig_at_port.check_any(assign_map(sig)))
		return false;

	if (sig.is_fully_const() || old_sig == sig)
		return true;

	if (recursion_monitor.check_any(sig)) {
		log("Warning: logic loop in mux tree at signal %s in module %s.\n",
				log_signal(sig), RTLIL::id2cstr(module->name));
		return false;
	}

	recursion_monitor.add(sig);

	std::set<sig2driver_entry_t> cellport_list;
	sig2driver.find(sig, cellport_list);
	for (auto &cellport : cellport_list) {
		if ((cellport.first->type != "$mux" && cellport.first->type != "$pmux" && cellport.first->type != "$safe_pmux") || cellport.second != "\\Y")
			return false;
		RTLIL::SigSpec sig_a = assign_map(cellport.first->connections["\\A"]);
		RTLIL::SigSpec sig_b = assign_map(cellport.first->connections["\\B"]);
		if (!check_state_mux_tree(old_sig, sig_a, recursion_monitor))
			return false;
		for (int i = 0; i < sig_b.size(); i += sig_a.size())
			if (!check_state_mux_tree(old_sig, sig_b.extract(i, sig_a.size()), recursion_monitor))
				return false;
		muxtree_cells.insert(cellport.first);
	}

	recursion_monitor.del(sig);

	return true;
}

static bool check_state_users(RTLIL::SigSpec sig)
{
	if (sig_at_port.check_any(assign_map(sig)))
		return false;

	std::set<sig2driver_entry_t> cellport_list;
	sig2user.find(sig, cellport_list);
	for (auto &cellport : cellport_list) {
		RTLIL::Cell *cell = cellport.first;
		if (muxtree_cells.count(cell) > 0)
			continue;
		if (cellport.second != "\\A" && cellport.second != "\\B")
			return false;
		if (cell->connections.count("\\A") == 0 || cell->connections.count("\\B") == 0 || cell->connections.count("\\Y") == 0)
			return false;
		for (auto &port_it : cell->connections)
			if (port_it.first != "\\A" && port_it.first != "\\B" && port_it.first != "\\Y")
				return false;
		if (assign_map(cell->connections["\\A"]) == sig && cell->connections["\\B"].is_fully_const())
			continue;
		if (assign_map(cell->connections["\\B"]) == sig && cell->connections["\\A"].is_fully_const())
			continue;
		return false;
	}

	return true;
}

static void detect_fsm(RTLIL::Wire *wire)
{
	if (wire->attributes.count("\\fsm_encoding") > 0 || wire->width <= 1)
		return;
	if (sig_at_port.check_any(assign_map(RTLIL::SigSpec(wire))))
		return;

	std::set<sig2driver_entry_t> cellport_list;
	sig2driver.find(RTLIL::SigSpec(wire), cellport_list);
	for (auto &cellport : cellport_list) {
		if ((cellport.first->type != "$dff" && cellport.first->type != "$adff") || cellport.second != "\\Q")
			continue;
		muxtree_cells.clear();
		SigPool recursion_monitor;
		RTLIL::SigSpec sig_q = assign_map(cellport.first->connections["\\Q"]);
		RTLIL::SigSpec sig_d = assign_map(cellport.first->connections["\\D"]);
		if (sig_q == RTLIL::SigSpec(wire) && check_state_mux_tree(sig_q, sig_d, recursion_monitor) && check_state_users(sig_q)) {
			log("Found FSM state register %s in module %s.\n", wire->name.c_str(), module->name.c_str());
			wire->attributes["\\fsm_encoding"] = RTLIL::Const("auto");
			return;
		}
	}
}

struct FsmDetectPass : public Pass {
	FsmDetectPass() : Pass("fsm_detect", "finding FSMs in design") { }
	virtual void help()
	{
		//   |---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|
		log("\n");
		log("    fsm_detect [selection]\n");
		log("\n");
		log("This pass detects finite state machines by identifying the state signal.\n");
		log("The state signal is then marked by setting the attribute 'fsm_encoding'\n");
		log("on the state signal to \"auto\".\n");
		log("\n");
		log("Existing 'fsm_encoding' attributes are not changed by this pass.\n");
		log("\n");
		log("Signals can be protected from being detected by this pass by setting the\n");
		log("'fsm_encoding' attribute to \"none\".\n");
		log("\n");
	}
	virtual void execute(std::vector<std::string> args, RTLIL::Design *design)
	{
		log_header("Executing FSM_DETECT pass (finding FSMs in design).\n");
		extra_args(args, 1, design);

		CellTypes ct;
		ct.setup_internals();
		ct.setup_internals_mem();
		ct.setup_stdcells();
		ct.setup_stdcells_mem();

		for (auto &mod_it : design->modules)
		{
			if (!design->selected(mod_it.second))
				continue;

			module = mod_it.second;
			assign_map.set(module);

			sig2driver.clear();
			sig2user.clear();
			sig_at_port.clear();
			for (auto &cell_it : module->cells)
				for (auto &conn_it : cell_it.second->connections) {
					if (ct.cell_output(cell_it.second->type, conn_it.first) || !ct.cell_known(cell_it.second->type)) {
						RTLIL::SigSpec sig = conn_it.second;
						assign_map.apply(sig);
						sig2driver.insert(sig, sig2driver_entry_t(cell_it.second, conn_it.first));
					}
					if (!ct.cell_known(cell_it.second->type) || ct.cell_input(cell_it.second->type, conn_it.first)) {
						RTLIL::SigSpec sig = conn_it.second;
						assign_map.apply(sig);
						sig2user.insert(sig, sig2driver_entry_t(cell_it.second, conn_it.first));
					}
				}

			for (auto &wire_it : module->wires)
				if (wire_it.second->port_id != 0)
					sig_at_port.add(assign_map(RTLIL::SigSpec(wire_it.second)));

			for (auto &wire_it : module->wires)
				if (design->selected(module, wire_it.second))
					detect_fsm(wire_it.second);
		}

		assign_map.clear();
		sig2driver.clear();
		sig2user.clear();
		muxtree_cells.clear();
	}
} FsmDetectPass;