yosys/backends/functional/smtlib.cc

/*
 *  yosys -- Yosys Open SYnthesis Suite
 *
 *  Copyright (C) 2024  Emily Schmidt <emily@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/functionalir.h"
#include "kernel/yosys.h"

USING_YOSYS_NAMESPACE
PRIVATE_NAMESPACE_BEGIN

const char illegal_characters[] = "$\\";
const char *reserved_keywords[] = {};

struct SmtScope {
	pool<std::string> used_names;
	dict<IdString, std::string> name_map;
	FunctionalTools::Scope scope;
	SmtScope() : scope(illegal_characters, reserved_keywords) {}

	void reserve(const std::string &name) { used_names.insert(name); }

	std::string insert(IdString id)
	{
		std::string name = RTLIL::unescape_id(id);
		if (used_names.count(name) == 0) {
			used_names.insert(name);
			name_map[id] = name;
			return name;
		}
		for (int idx = 0;; ++idx) {
			std::string new_name = name + "_" + std::to_string(idx);
			if (used_names.count(new_name) == 0) {
				used_names.insert(new_name);
				name_map[id] = new_name;
				return new_name;
			}
		}
	}

	std::string operator[](IdString id)
	{
		if (name_map.count(id)) {
			return name_map[id];
		} else {
			return insert(id);
		}
	}
};

struct SmtWriter {
	std::ostream &stream;

	SmtWriter(std::ostream &out) : stream(out) {}

	void print(const char *fmt, ...)
	{
		va_list args;
		va_start(args, fmt);
		stream << vstringf(fmt, args);
		va_end(args);
	}
};

template <class NodeNames> struct SmtPrintVisitor {
	using Node = FunctionalIR::Node;
	NodeNames np;
	SmtScope &scope;

	SmtPrintVisitor(NodeNames np, SmtScope &scope) : np(np), scope(scope) {}

	template <class T> std::string arg_to_string(T n) { return std::to_string(n); }

	std::string arg_to_string(std::string n) { return n; }

	std::string arg_to_string(Node n) { return np(n); }

	template <typename... Args> std::string format(std::string fmt, Args &&...args)
	{
		std::vector<std::string> arg_strings = {arg_to_string(std::forward<Args>(args))...};
		for (size_t i = 0; i < arg_strings.size(); ++i) {
			std::string placeholder = "%" + std::to_string(i);
			size_t pos = 0;
			while ((pos = fmt.find(placeholder, pos)) != std::string::npos) {
				fmt.replace(pos, placeholder.length(), arg_strings[i]);
				pos += arg_strings[i].length();
			}
		}
		return fmt;
	}
	std::string buf(Node, Node n) { return np(n); }

	std::string slice(Node, Node a, int, int offset, int out_width)
	{
		return format("(_ extract %1 %2 %0)", np(a), offset, offset + out_width - 1);
	}

	std::string zero_extend(Node, Node a, int, int out_width) { return format("((_ zero_extend %1) %0)", np(a), out_width - a.width()); }

	std::string sign_extend(Node, Node a, int, int out_width) { return format("((_ sign_extend %1) %0)", np(a), out_width - a.width()); }

	std::string concat(Node, Node a, int, Node b, int) { return format("(concat %0 %1)", np(a), np(b)); }

	std::string add(Node, Node a, Node b, int) { return format("(bvadd %0 %1)", np(a), np(b)); }

	std::string sub(Node, Node a, Node b, int) { return format("(bvsub %0 %1)", np(a), np(b)); }

	std::string bitwise_and(Node, Node a, Node b, int) { return format("(bvand %0 %1)", np(a), np(b)); }

	std::string bitwise_or(Node, Node a, Node b, int) { return format("(bvor %0 %1)", np(a), np(b)); }

	std::string bitwise_xor(Node, Node a, Node b, int) { return format("(bvxor %0 %1)", np(a), np(b)); }

	std::string bitwise_not(Node, Node a, int) { return format("(bvnot %0)", np(a)); }

	std::string unary_minus(Node, Node a, int) { return format("(bvneg %0)", np(a)); }

	std::string reduce_and(Node, Node a, int) { return format("(= %0 #b1)", np(a)); }

	std::string reduce_or(Node, Node a, int)
	{
		std::stringstream ss;
		// We use ite to set the result to bit vector, to ensure appropriate type
		ss << "(ite (= " << np(a) << " #b" << std::string(a.width(), '0') << ") #b0 #b1)";
		return ss.str();
	}

	std::string reduce_xor(Node, Node a, int) { return format("(bvxor_reduce %0)", np(a)); }

	std::string equal(Node, Node a, Node b, int) { return format("(= %0 %1)", np(a), np(b)); }

	std::string not_equal(Node, Node a, Node b, int) { return format("(distinct %0 %1)", np(a), np(b)); }

	std::string signed_greater_than(Node, Node a, Node b, int) { return format("(bvsgt %0 %1)", np(a), np(b)); }

	std::string signed_greater_equal(Node, Node a, Node b, int) { return format("(bvsge %0 %1)", np(a), np(b)); }

	std::string unsigned_greater_than(Node, Node a, Node b, int) { return format("(bvugt %0 %1)", np(a), np(b)); }

	std::string unsigned_greater_equal(Node, Node a, Node b, int) { return format("(bvuge %0 %1)", np(a), np(b)); }

	std::string logical_shift_left(Node, Node a, Node b, int, int) { return format("(bvshl %0 %1)", np(a), np(b)); }

	std::string logical_shift_right(Node, Node a, Node b, int, int) { return format("(bvlshr %0 %1)", np(a), np(b)); }

	std::string arithmetic_shift_right(Node, Node a, Node b, int, int) { return format("(bvashr %0 %1)", np(a), np(b)); }

	std::string mux(Node, Node a, Node b, Node s, int) { return format("(ite %2 %0 %1)", np(a), np(b), np(s)); }

	std::string pmux(Node, Node a, Node b, Node s, int, int)
	{
		// Assume s is a bit vector, combine a and b based on the selection bits
		return format("(pmux %0 %1 %2)", np(a), np(b), np(s));
	}

	std::string constant(Node, RTLIL::Const value) { return format("#b%1", value.as_string()); }

	std::string input(Node, IdString name) { return format("%0", scope[name]); }

	std::string state(Node, IdString name) { return format("%0", scope[name]); }

	std::string memory_read(Node, Node mem, Node addr, int, int) { return format("(select %0 %1)", np(mem), np(addr)); }

	std::string memory_write(Node, Node mem, Node addr, Node data, int, int) { return format("(store %0 %1 %2)", np(mem), np(addr), np(data)); }

	std::string undriven(Node, int width) { return format("#b%0", std::string(width, '0')); }
};

struct SmtModule {
	std::string name;
	SmtScope scope;
	FunctionalIR ir;

	SmtModule(const std::string &module_name, FunctionalIR ir) : name(module_name), ir(std::move(ir)) {}

	void write(std::ostream &out)
	{
		SmtWriter writer(out);

		writer.print("(declare-fun %s () Bool)\n", name.c_str());
		writer.print("(declare-datatypes () ((Inputs (mk_inputs");
		for (const auto &input : ir.inputs()) {
			std::string input_name = scope[input.first];
			writer.print(" (%s (_ BitVec %d))", input_name.c_str(), input.second.width());
		}
		writer.print("))))\n");

		writer.print("(declare-datatypes () ((Outputs (mk_outputs");
		for (const auto &output : ir.outputs()) {
			std::string output_name = scope[output.first];
			writer.print(" (%s (_ BitVec %d))", output_name.c_str(), output.second.width());
		}
		writer.print("))))\n");

		writer.print("(declare-fun state () (_ BitVec 1))\n");

		writer.print("(define-fun %s_step ((state (_ BitVec 1)) (inputs Inputs)) Outputs", name.c_str());
		writer.print("  (let (");
		for (const auto &input : ir.inputs()) {
			std::string input_name = scope[input.first];
			writer.print("    (%s (%s inputs))", input_name.c_str(), input_name.c_str());
		}
		writer.print("  )");

		auto node_to_string = [&](FunctionalIR::Node n) { return scope[n.name()]; };
		SmtPrintVisitor<decltype(node_to_string)> visitor(node_to_string, scope);

		for (auto it = ir.begin(); it != ir.end(); ++it) {
			const FunctionalIR::Node &node = *it;

			if (ir.inputs().count(node.name()) > 0)
				continue;

			std::string node_name = scope[node.name()];
			std::string node_expr = node.visit(visitor);

			writer.print("  (let (      (%s %s))", node_name.c_str(), node_expr.c_str());
		}

		writer.print("    (let (");
		for (const auto &output : ir.outputs()) {
			std::string output_name = scope[output.first];
			const std::string output_assignment = ir.get_output_node(output.first).name().c_str();
			writer.print("      (%s %s)", output_name.c_str(), output_assignment.substr(1).c_str());
		}
		writer.print("    )");
		writer.print("      (mk_outputs");
		for (const auto &output : ir.outputs()) {
			std::string output_name = scope[output.first];
			writer.print("        %s", output_name.c_str());
		}
		writer.print("      )");
		writer.print("    )");

		// Close the nested lets
		for (size_t i = 0; i < ir.size() - ir.inputs().size(); ++i) {
			writer.print("  )");
		}

		writer.print("  )");
		writer.print(")\n");
	}
};

struct FunctionalSmtBackend : public Backend {
	FunctionalSmtBackend() : Backend("functional_smt2", "Generate SMT-LIB from Functional IR") {}

	void help() override { log("\nFunctional SMT Backend.\n\n"); }

	void execute(std::ostream *&f, std::string filename, std::vector<std::string> args, RTLIL::Design *design) override
	{
		log_header(design, "Executing Functional SMT Backend.\n");

		size_t argidx = 1;
		extra_args(f, filename, args, argidx, design);

		for (auto module : design->selected_modules()) {
			log("Processing module `%s`.\n", module->name.c_str());
			auto ir = FunctionalIR::from_module(module);
			SmtModule smt(RTLIL::unescape_id(module->name), ir);
			smt.write(*f);
		}
	}
} FunctionalSmtBackend;

PRIVATE_NAMESPACE_END