solidity/libsmtutil/Z3Interface.cpp

/*
	This file is part of solidity.

	solidity is free software: you can redistribute it and/or modify
	it under the terms of the GNU General Public License as published by
	the Free Software Foundation, either version 3 of the License, or
	(at your option) any later version.

	solidity is distributed in the hope that it will be useful,
	but WITHOUT ANY WARRANTY; without even the implied warranty of
	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
	GNU General Public License for more details.

	You should have received a copy of the GNU General Public License
	along with solidity.  If not, see <http://www.gnu.org/licenses/>.
*/
// SPDX-License-Identifier: GPL-3.0

#include <libsmtutil/Z3Interface.h>

#include <libsolutil/CommonData.h>
#include <libsolutil/CommonIO.h>

#ifdef HAVE_Z3_DLOPEN
#include <libsmtutil/Z3Loader.h>
#endif

using namespace std;
using namespace solidity::smtutil;
using namespace solidity::util;

bool Z3Interface::available()
{
#ifdef HAVE_Z3_DLOPEN
	return Z3Loader::get().available();
#else
	return true;
#endif
}

Z3Interface::Z3Interface(std::optional<unsigned> _queryTimeout):
	SolverInterface(_queryTimeout),
	m_solver(m_context)
{
	// These need to be set globally.
	z3::set_param("rewriter.pull_cheap_ite", true);

	if (m_queryTimeout)
		m_context.set("timeout", int(*m_queryTimeout));
	else
		z3::set_param("rlimit", resourceLimit);
}

void Z3Interface::reset()
{
	m_constants.clear();
	m_functions.clear();
	m_solver.reset();
}

void Z3Interface::push()
{
	m_solver.push();
}

void Z3Interface::pop()
{
	m_solver.pop();
}

void Z3Interface::declareVariable(string const& _name, SortPointer const& _sort)
{
	smtAssert(_sort, "");
	if (_sort->kind == Kind::Function)
		declareFunction(_name, *_sort);
	else if (m_constants.count(_name))
		m_constants.at(_name) = m_context.constant(_name.c_str(), z3Sort(*_sort));
	else
		m_constants.emplace(_name, m_context.constant(_name.c_str(), z3Sort(*_sort)));
}

void Z3Interface::declareFunction(string const& _name, Sort const& _sort)
{
	smtAssert(_sort.kind == Kind::Function, "");
	FunctionSort fSort = dynamic_cast<FunctionSort const&>(_sort);
	if (m_functions.count(_name))
		m_functions.at(_name) = m_context.function(_name.c_str(), z3Sort(fSort.domain), z3Sort(*fSort.codomain));
	else
		m_functions.emplace(_name, m_context.function(_name.c_str(), z3Sort(fSort.domain), z3Sort(*fSort.codomain)));
}

void Z3Interface::addAssertion(Expression const& _expr)
{
	m_solver.add(toZ3Expr(_expr));
}

pair<CheckResult, vector<string>> Z3Interface::check(vector<Expression> const& _expressionsToEvaluate)
{
	CheckResult result;
	vector<string> values;
	try
	{
		switch (m_solver.check())
		{
		case z3::check_result::sat:
			result = CheckResult::SATISFIABLE;
			break;
		case z3::check_result::unsat:
			result = CheckResult::UNSATISFIABLE;
			break;
		case z3::check_result::unknown:
			result = CheckResult::UNKNOWN;
			break;
		}

		if (result == CheckResult::SATISFIABLE && !_expressionsToEvaluate.empty())
		{
			z3::model m = m_solver.get_model();
			for (Expression const& e: _expressionsToEvaluate)
				values.push_back(util::toString(m.eval(toZ3Expr(e))));
		}
	}
	catch (z3::exception const& _err)
	{
		set<string> msgs{
			/// Resource limit (rlimit) exhausted.
			"max. resource limit exceeded",
			/// User given timeout exhausted.
			"canceled"
		};

		if (msgs.count(_err.msg()))
			result = CheckResult::UNKNOWN;
		else
			result = CheckResult::ERROR;
		values.clear();
	}

	return make_pair(result, values);
}

z3::expr Z3Interface::toZ3Expr(Expression const& _expr)
{
	if (_expr.arguments.empty() && m_constants.count(_expr.name))
		return m_constants.at(_expr.name);
	z3::expr_vector arguments(m_context);
	for (auto const& arg: _expr.arguments)
		arguments.push_back(toZ3Expr(arg));

	try
	{
		string const& n = _expr.name;
		if (m_functions.count(n))
			return m_functions.at(n)(arguments);
		else if (m_constants.count(n))
		{
			smtAssert(arguments.empty(), "");
			return m_constants.at(n);
		}
		else if (arguments.empty())
		{
			if (n == "true")
				return m_context.bool_val(true);
			else if (n == "false")
				return m_context.bool_val(false);
			else if (_expr.sort->kind == Kind::Sort)
			{
				auto sortSort = dynamic_pointer_cast<SortSort>(_expr.sort);
				smtAssert(sortSort, "");
				return m_context.constant(n.c_str(), z3Sort(*sortSort->inner));
			}
			else
				try
				{
					return m_context.int_val(n.c_str());
				}
				catch (z3::exception const& _e)
				{
					smtAssert(false, _e.msg());
				}
		}

		smtAssert(_expr.hasCorrectArity(), "");
		if (n == "ite")
			return z3::ite(arguments[0], arguments[1], arguments[2]);
		else if (n == "not")
			return !arguments[0];
		else if (n == "and")
			return arguments[0] && arguments[1];
		else if (n == "or")
			return arguments[0] || arguments[1];
		else if (n == "=>")
			return z3::implies(arguments[0], arguments[1]);
		else if (n == "=")
			return arguments[0] == arguments[1];
		else if (n == "<")
			return arguments[0] < arguments[1];
		else if (n == "<=")
			return arguments[0] <= arguments[1];
		else if (n == ">")
			return arguments[0] > arguments[1];
		else if (n == ">=")
			return arguments[0] >= arguments[1];
		else if (n == "+")
			return arguments[0] + arguments[1];
		else if (n == "-")
			return arguments[0] - arguments[1];
		else if (n == "*")
			return arguments[0] * arguments[1];
		else if (n == "div")
			return arguments[0] / arguments[1];
		else if (n == "mod")
			return z3::mod(arguments[0], arguments[1]);
		else if (n == "bvnot")
			return ~arguments[0];
		else if (n == "bvand")
			return arguments[0] & arguments[1];
		else if (n == "bvor")
			return arguments[0] | arguments[1];
		else if (n == "bvxor")
			return arguments[0] ^ arguments[1];
		else if (n == "bvshl")
			return z3::shl(arguments[0], arguments[1]);
		else if (n == "bvlshr")
			return z3::lshr(arguments[0], arguments[1]);
		else if (n == "bvashr")
			return z3::ashr(arguments[0], arguments[1]);
		else if (n == "int2bv")
		{
			size_t size = std::stoul(_expr.arguments[1].name);
			return z3::int2bv(static_cast<unsigned>(size), arguments[0]);
		}
		else if (n == "bv2int")
		{
			auto intSort = dynamic_pointer_cast<IntSort>(_expr.sort);
			smtAssert(intSort, "");
			return z3::bv2int(arguments[0], intSort->isSigned);
		}
		else if (n == "select")
			return z3::select(arguments[0], arguments[1]);
		else if (n == "store")
			return z3::store(arguments[0], arguments[1], arguments[2]);
		else if (n == "const_array")
		{
			shared_ptr<SortSort> sortSort = std::dynamic_pointer_cast<SortSort>(_expr.arguments[0].sort);
			smtAssert(sortSort, "");
			auto arraySort = dynamic_pointer_cast<ArraySort>(sortSort->inner);
			smtAssert(arraySort && arraySort->domain, "");
			return z3::const_array(z3Sort(*arraySort->domain), arguments[1]);
		}
		else if (n == "tuple_get")
		{
			size_t index = stoul(_expr.arguments[1].name);
			return z3::func_decl(m_context, Z3_get_tuple_sort_field_decl(m_context, z3Sort(*_expr.arguments[0].sort), static_cast<unsigned>(index)))(arguments[0]);
		}
		else if (n == "tuple_constructor")
		{
			auto constructor = z3::func_decl(m_context, Z3_get_tuple_sort_mk_decl(m_context, z3Sort(*_expr.sort)));
			smtAssert(constructor.arity() == arguments.size(), "");
			z3::expr_vector args(m_context);
			for (auto const& arg: arguments)
				args.push_back(arg);
			return constructor(args);
		}

		smtAssert(false, "");
	}
	catch (z3::exception const& _e)
	{
		smtAssert(false, _e.msg());
	}

	smtAssert(false, "");
}

Expression Z3Interface::fromZ3Expr(z3::expr const& _expr)
{
	auto sort = fromZ3Sort(_expr.get_sort());
	if (_expr.is_const() || _expr.is_var())
		return Expression(_expr.to_string(), {}, sort);

	if (_expr.is_quantifier())
	{
		string quantifierName;
		if (_expr.is_exists())
			quantifierName = "exists";
		else if (_expr.is_forall())
			quantifierName = "forall";
		else if (_expr.is_lambda())
			quantifierName = "lambda";
		else
			smtAssert(false, "");
		return Expression(quantifierName, {fromZ3Expr(_expr.body())}, sort);
	}
	smtAssert(_expr.is_app(), "");
	vector<Expression> arguments;
	for (unsigned i = 0; i < _expr.num_args(); ++i)
		arguments.push_back(fromZ3Expr(_expr.arg(i)));

	auto kind = _expr.decl().decl_kind();

	if (_expr.is_ite())
		return Expression::ite(arguments[0], arguments[1], arguments[2]);
	else if (_expr.is_not())
		return !arguments[0];
	else if (_expr.is_and())
		return Expression::mkAnd(arguments);
	else if (_expr.is_or())
		return Expression::mkOr(arguments);
	else if (_expr.is_implies())
		return Expression::implies(arguments[0], arguments[1]);
	else if (_expr.is_eq())
	{
		smtAssert(arguments.size() == 2, "");
		return arguments[0] == arguments[1];
	}
	else if (kind == Z3_OP_ULT || kind == Z3_OP_SLT)
		return arguments[0] < arguments[1];
	else if (kind == Z3_OP_LE || kind == Z3_OP_ULEQ || kind == Z3_OP_SLEQ)
		return arguments[0] <= arguments[1];
	else if (kind == Z3_OP_GT || kind == Z3_OP_SGT)
		return arguments[0] > arguments[1];
	else if (kind == Z3_OP_GE || kind == Z3_OP_UGEQ || kind == Z3_OP_SGEQ)
		return arguments[0] >= arguments[1];
	else if (kind == Z3_OP_ADD)
		return Expression::mkPlus(arguments);
	else if (kind == Z3_OP_SUB)
	{
		smtAssert(arguments.size() == 2, "");
		return arguments[0] - arguments[1];
	}
	else if (kind == Z3_OP_MUL)
		return Expression::mkMul(arguments);
	else if (kind == Z3_OP_DIV)
	{
		smtAssert(arguments.size() == 2, "");
		return arguments[0] / arguments[1];
	}
	else if (kind == Z3_OP_MOD)
		return arguments[0] % arguments[1];
	else if (kind == Z3_OP_XOR)
		return arguments[0] ^ arguments[1];
	else if (kind == Z3_OP_BNOT)
		return !arguments[0];
	else if (kind == Z3_OP_BSHL)
		return arguments[0] << arguments[1];
	else if (kind == Z3_OP_BLSHR)
		return arguments[0] >> arguments[1];
	else if (kind == Z3_OP_BASHR)
		return Expression::ashr(arguments[0], arguments[1]);
	else if (kind == Z3_OP_INT2BV)
		return Expression::int2bv(arguments[0], _expr.get_sort().bv_size());
	else if (kind == Z3_OP_BV2INT)
		return Expression::bv2int(arguments[0]);
	else if (kind == Z3_OP_EXTRACT)
		return Expression("extract", arguments, sort);
	else if (kind == Z3_OP_SELECT)
		return Expression::select(arguments[0], arguments[1]);
	else if (kind == Z3_OP_STORE)
		return Expression::store(arguments[0], arguments[1], arguments[2]);
	else if (kind == Z3_OP_CONST_ARRAY)
	{
		auto sortSort = make_shared<SortSort>(fromZ3Sort(_expr.get_sort()));
		return Expression::const_array(Expression(sortSort), arguments[0]);
	}
	else if (kind == Z3_OP_DT_CONSTRUCTOR)
	{
		auto sortSort = make_shared<SortSort>(fromZ3Sort(_expr.get_sort()));
		return Expression::tuple_constructor(Expression(sortSort), arguments);
	}
	else if (kind == Z3_OP_DT_ACCESSOR)
		return Expression("dt_accessor_" + _expr.decl().name().str(), arguments, sort);
	else if (kind == Z3_OP_DT_IS)
		return Expression("dt_is", {arguments.at(0)}, sort);
	else if (
		kind == Z3_OP_UNINTERPRETED ||
		kind == Z3_OP_RECURSIVE
	)
		return Expression(_expr.decl().name().str(), arguments, fromZ3Sort(_expr.get_sort()));

	smtAssert(false, "");
}

z3::sort Z3Interface::z3Sort(Sort const& _sort)
{
	switch (_sort.kind)
	{
	case Kind::Bool:
		return m_context.bool_sort();
	case Kind::Int:
		return m_context.int_sort();
	case Kind::BitVector:
		return m_context.bv_sort(dynamic_cast<BitVectorSort const&>(_sort).size);
	case Kind::Array:
	{
		auto const& arraySort = dynamic_cast<ArraySort const&>(_sort);
		return m_context.array_sort(z3Sort(*arraySort.domain), z3Sort(*arraySort.range));
	}
	case Kind::Tuple:
	{
		auto const& tupleSort = dynamic_cast<TupleSort const&>(_sort);
		vector<char const*> cMembers;
		for (auto const& member: tupleSort.members)
			cMembers.emplace_back(member.c_str());
		/// Using this instead of the function below because with that one
		/// we can't use `&sorts[0]` here.
		vector<z3::sort> sorts;
		for (auto const& sort: tupleSort.components)
			sorts.push_back(z3Sort(*sort));
		z3::func_decl_vector projs(m_context);
		z3::func_decl tupleConstructor = m_context.tuple_sort(
			tupleSort.name.c_str(),
			static_cast<unsigned>(tupleSort.members.size()),
			cMembers.data(),
			sorts.data(),
			projs
		);
		return tupleConstructor.range();
	}

	default:
		break;
	}
	smtAssert(false, "");
	// Cannot be reached.
	return m_context.int_sort();
}

z3::sort_vector Z3Interface::z3Sort(vector<SortPointer> const& _sorts)
{
	z3::sort_vector z3Sorts(m_context);
	for (auto const& _sort: _sorts)
		z3Sorts.push_back(z3Sort(*_sort));
	return z3Sorts;
}

SortPointer Z3Interface::fromZ3Sort(z3::sort const& _sort)
{
	if (_sort.is_bool())
		return SortProvider::boolSort;
	if (_sort.is_int())
		return SortProvider::sintSort;
	if (_sort.is_bv())
		return make_shared<BitVectorSort>(_sort.bv_size());
	if (_sort.is_array())
		return make_shared<ArraySort>(fromZ3Sort(_sort.array_domain()), fromZ3Sort(_sort.array_range()));
	if (_sort.is_datatype())
	{
		auto name = _sort.name().str();
		auto constructor = z3::func_decl(m_context, Z3_get_tuple_sort_mk_decl(m_context, _sort));
		vector<string> memberNames;
		vector<SortPointer> memberSorts;
		for (unsigned i = 0; i < constructor.arity(); ++i)
		{
			auto accessor = z3::func_decl(m_context, Z3_get_tuple_sort_field_decl(m_context, _sort, i));
			memberNames.push_back(accessor.name().str());
			memberSorts.push_back(fromZ3Sort(accessor.range()));
		}
		return make_shared<TupleSort>(name, memberNames, memberSorts);
	}
	smtAssert(false, "");
}

vector<SortPointer> Z3Interface::fromZ3Sort(z3::sort_vector const& _sorts)
{
	return applyMap(_sorts, [this](auto const& sort) { return fromZ3Sort(sort); });
}