yosys/passes/opt/opt_merge.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.
 *
 */

#include "kernel/register.h"
#include "kernel/ffinit.h"
#include "kernel/sigtools.h"
#include "kernel/log.h"
#include "kernel/celltypes.h"
#include "libs/sha1/sha1.h"
#include <stdlib.h>
#include <stdio.h>
#include <algorithm>
#include <set>
#include <unordered_map>
#include <array>


USING_YOSYS_NAMESPACE
PRIVATE_NAMESPACE_BEGIN

template <typename T, typename U>
inline Hasher hash_pair(const T &t, const U &u) { return hash_ops<std::pair<T, U>>::hash(t, u); }

struct OptMergeWorker
{
	RTLIL::Design *design;
	RTLIL::Module *module;
	SigMap assign_map;
	FfInitVals initvals;
	bool mode_share_all;

	CellTypes ct;
	int total_count;

	static Hasher hash_pmux_in(const SigSpec& sig_s, const SigSpec& sig_b, Hasher h)
	{
		int s_width = GetSize(sig_s);
		int width = GetSize(sig_b) / s_width;

		hashlib::commutative_hash comm;
		for (int i = 0; i < s_width; i++)
			comm.eat(hash_pair(sig_s[i], sig_b.extract(i*width, width)));

		return comm.hash_into(h);
	}

	static void sort_pmux_conn(dict<RTLIL::IdString, RTLIL::SigSpec> &conn)
	{
		SigSpec sig_s = conn.at(ID::S);
		SigSpec sig_b = conn.at(ID::B);

		int s_width = GetSize(sig_s);
		int width = GetSize(sig_b) / s_width;

		vector<pair<SigBit, SigSpec>> sb_pairs;
		for (int i = 0; i < s_width; i++)
			sb_pairs.push_back(pair<SigBit, SigSpec>(sig_s[i], sig_b.extract(i*width, width)));

		std::sort(sb_pairs.begin(), sb_pairs.end());

		conn[ID::S] = SigSpec();
		conn[ID::B] = SigSpec();

		for (auto &it : sb_pairs) {
			conn[ID::S].append(it.first);
			conn[ID::B].append(it.second);
		}
	}

	Hasher hash_cell_inputs(const RTLIL::Cell *cell, Hasher h) const
	{
		// TODO: when implemented, use celltypes to match:
		// (builtin || stdcell) && (unary || binary) && symmetrical
		if (cell->type.in(ID($and), ID($or), ID($xor), ID($xnor), ID($add), ID($mul),
				ID($logic_and), ID($logic_or), ID($_AND_), ID($_OR_), ID($_XOR_))) {
			hashlib::commutative_hash comm;
			comm.eat(assign_map(cell->getPort(ID::A)));
			comm.eat(assign_map(cell->getPort(ID::B)));
			h = comm.hash_into(h);
		} else if (cell->type.in(ID($reduce_xor), ID($reduce_xnor))) {
			SigSpec a = assign_map(cell->getPort(ID::A));
			a.sort();
			h = a.hash_into(h);
		} else if (cell->type.in(ID($reduce_and), ID($reduce_or), ID($reduce_bool))) {
			SigSpec a = assign_map(cell->getPort(ID::A));
			a.sort_and_unify();
			h = a.hash_into(h);
		} else if (cell->type == ID($pmux)) {
			SigSpec sig_s = assign_map(cell->getPort(ID::S));
			SigSpec sig_b = assign_map(cell->getPort(ID::B));
			h = hash_pmux_in(sig_s, sig_b, h);
			h = assign_map(cell->getPort(ID::A)).hash_into(h);
		} else {
			hashlib::commutative_hash comm;
			for (const auto& [port, sig] : cell->connections()) {
				if (cell->output(port))
					continue;
				comm.eat(hash_pair(port, assign_map(sig)));
			}
			h = comm.hash_into(h);
			if (cell->is_builtin_ff())
				h = initvals(cell->getPort(ID::Q)).hash_into(h);
		}
		return h;
	}

	static Hasher hash_cell_parameters(const RTLIL::Cell *cell, Hasher h)
	{
		hashlib::commutative_hash comm;
		for (const auto& param : cell->parameters) {
			comm.eat(param);
		}
		return comm.hash_into(h);
	}

	Hasher hash_cell_function(const RTLIL::Cell *cell, Hasher h) const
	{
		h.eat(cell->type);
		h = hash_cell_inputs(cell, h);
		h = hash_cell_parameters(cell, h);
		return h;
	}

	bool compare_cell_parameters_and_connections(const RTLIL::Cell *cell1, const RTLIL::Cell *cell2) const
	{
		if (cell1 == cell2) return true;
		if (cell1->type != cell2->type) return false;

		if (cell1->parameters != cell2->parameters)
			return false;

		if (cell1->connections_.size() != cell2->connections_.size())
			return false;
		for (const auto &it : cell1->connections_)
			if (!cell2->connections_.count(it.first))
				return false;

		decltype(Cell::connections_) conn1, conn2;
		conn1.reserve(cell1->connections_.size());
		conn2.reserve(cell1->connections_.size());

		for (const auto &it : cell1->connections_) {
			if (cell1->output(it.first)) {
				if (it.first == ID::Q && cell1->is_builtin_ff()) {
					// For the 'Q' output of state elements,
					//   use the (* init *) attribute value
					conn1[it.first] = initvals(it.second);
					conn2[it.first] = initvals(cell2->getPort(it.first));
				}
				else {
					conn1[it.first] = RTLIL::SigSpec();
					conn2[it.first] = RTLIL::SigSpec();
				}
			}
			else {
				conn1[it.first] = assign_map(it.second);
				conn2[it.first] = assign_map(cell2->getPort(it.first));
			}
		}

		if (cell1->type.in(ID($and), ID($or), ID($xor), ID($xnor), ID($add), ID($mul),
				ID($logic_and), ID($logic_or), ID($_AND_), ID($_OR_), ID($_XOR_))) {
			if (conn1.at(ID::A) < conn1.at(ID::B)) {
				std::swap(conn1[ID::A], conn1[ID::B]);
			}
			if (conn2.at(ID::A) < conn2.at(ID::B)) {
				std::swap(conn2[ID::A], conn2[ID::B]);
			}
		} else
		if (cell1->type.in(ID($reduce_xor), ID($reduce_xnor))) {
			conn1[ID::A].sort();
			conn2[ID::A].sort();
		} else
		if (cell1->type.in(ID($reduce_and), ID($reduce_or), ID($reduce_bool))) {
			conn1[ID::A].sort_and_unify();
			conn2[ID::A].sort_and_unify();
		} else
		if (cell1->type == ID($pmux)) {
			sort_pmux_conn(conn1);
			sort_pmux_conn(conn2);
		}

		return conn1 == conn2;
	}

	bool has_dont_care_initval(const RTLIL::Cell *cell)
	{
		if (!cell->is_builtin_ff())
			return false;

		return !initvals(cell->getPort(ID::Q)).is_fully_def();
	}

	OptMergeWorker(RTLIL::Design *design, RTLIL::Module *module, bool mode_nomux, bool mode_share_all, bool mode_keepdc) :
		design(design), module(module), mode_share_all(mode_share_all)
	{
		total_count = 0;
		ct.setup_internals();
		ct.setup_internals_mem();
		ct.setup_stdcells();
		ct.setup_stdcells_mem();

		if (mode_nomux) {
			ct.cell_types.erase(ID($mux));
			ct.cell_types.erase(ID($pmux));
		}

		ct.cell_types.erase(ID($tribuf));
		ct.cell_types.erase(ID($_TBUF_));
		ct.cell_types.erase(ID($anyseq));
		ct.cell_types.erase(ID($anyconst));
		ct.cell_types.erase(ID($allseq));
		ct.cell_types.erase(ID($allconst));

		log("Finding identical cells in module `%s'.\n", module->name);
		assign_map.set(module);

		initvals.set(&assign_map, module);

		bool did_something = true;
		// A cell may have to go through a lot of collisions if the hash
		// function is performing poorly, but it's a symptom of something bad
		// beyond the user's control.
		while (did_something)
		{
			std::vector<RTLIL::Cell*> cells;
			cells.reserve(module->cells().size());
			for (auto cell : module->cells()) {
				if (!design->selected(module, cell))
					continue;
				if (cell->type.in(ID($meminit), ID($meminit_v2), ID($mem), ID($mem_v2))) {
					// Ignore those for performance: meminit can have an excessively large port,
					// mem can have an excessively large parameter holding the init data
					continue;
				}
				if (cell->type == ID($scopeinfo))
					continue;
				if (mode_keepdc && has_dont_care_initval(cell))
					continue;
				if (!cell->known())
					continue;
				if (!mode_share_all && !ct.cell_known(cell->type))
					continue;
				cells.push_back(cell);
			}

			did_something = false;

			// We keep a set of known cells. They're hashed with our hash_cell_function
			// and compared with our compare_cell_parameters_and_connections.
			// Both need to capture OptMergeWorker to access initvals
			struct CellPtrHash {
				const OptMergeWorker& worker;
				CellPtrHash(const OptMergeWorker& w) : worker(w) {}
				std::size_t operator()(const Cell* c) const {
					return (std::size_t)worker.hash_cell_function(c, Hasher()).yield();
				}
			};
			struct CellPtrEqual {
				const OptMergeWorker& worker;
				CellPtrEqual(const OptMergeWorker& w) : worker(w) {}
				bool operator()(const Cell* lhs, const Cell* rhs) const {
					return worker.compare_cell_parameters_and_connections(lhs, rhs);
				}
			};
			std::unordered_set<
				RTLIL::Cell*,
				CellPtrHash,
				CellPtrEqual> known_cells (0, CellPtrHash(*this), CellPtrEqual(*this));

			for (auto cell : cells)
			{
				auto [cell_in_map, inserted] = known_cells.insert(cell);
				if (!inserted) {
					// We've failed to insert since we already have an equivalent cell
					Cell* other_cell = *cell_in_map;
					if (cell->has_keep_attr()) {
						if (other_cell->has_keep_attr())
							continue;
						known_cells.erase(other_cell);
						known_cells.insert(cell);
						std::swap(other_cell, cell);
					}

					did_something = true;
					log_debug("  Cell `%s' is identical to cell `%s'.\n", cell->name, other_cell->name);
					for (auto &it : cell->connections()) {
						if (cell->output(it.first)) {
							RTLIL::SigSpec other_sig = other_cell->getPort(it.first);
							log_debug("    Redirecting output %s: %s = %s\n", it.first,
									log_signal(it.second), log_signal(other_sig));
							Const init = initvals(other_sig);
							initvals.remove_init(it.second);
							initvals.remove_init(other_sig);
							module->connect(RTLIL::SigSig(it.second, other_sig));
							assign_map.add(it.second, other_sig);
							initvals.set_init(other_sig, init);
						}
					}
					log_debug("    Removing %s cell `%s' from module `%s'.\n", cell->type, cell->name, module->name);
					module->remove(cell);
					total_count++;
				}
			}
		}

		log_suppressed();
	}
};

struct OptMergePass : public Pass {
	OptMergePass() : Pass("opt_merge", "consolidate identical cells") { }
	void help() override
	{
		//   |---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|
		log("\n");
		log("    opt_merge [options] [selection]\n");
		log("\n");
		log("This pass identifies cells with identical type and input signals. Such cells\n");
		log("are then merged to one cell.\n");
		log("\n");
		log("    -nomux\n");
		log("        Do not merge MUX cells.\n");
		log("\n");
		log("    -share_all\n");
		log("        Operate on all cell types, not just built-in types.\n");
		log("\n");
		log("    -keepdc\n");
		log("        Do not merge flipflops with don't-care bits in their initial value.\n");
		log("\n");
	}
	void execute(std::vector<std::string> args, RTLIL::Design *design) override
	{
		log_header(design, "Executing OPT_MERGE pass (detect identical cells).\n");

		bool mode_nomux = false;
		bool mode_share_all = false;
		bool mode_keepdc = false;

		size_t argidx;
		for (argidx = 1; argidx < args.size(); argidx++) {
			std::string arg = args[argidx];
			if (arg == "-nomux") {
				mode_nomux = true;
				continue;
			}
			if (arg == "-share_all") {
				mode_share_all = true;
				continue;
			}
			if (arg == "-keepdc") {
				mode_keepdc = true;
				continue;
			}
			break;
		}
		extra_args(args, argidx, design);

		int total_count = 0;
		for (auto module : design->selected_modules()) {
			OptMergeWorker worker(design, module, mode_nomux, mode_share_all, mode_keepdc);
			total_count += worker.total_count;
		}

		if (total_count)
			design->scratchpad_set_bool("opt.did_something", true);
		log("Removed a total of %d cells.\n", total_count);
	}
} OptMergePass;

PRIVATE_NAMESPACE_END