mirror of
https://github.com/ethereum/solidity
synced 2023-10-03 13:03:40 +00:00
133 lines
4.5 KiB
C++
133 lines
4.5 KiB
C++
/*
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This file is part of solidity.
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solidity is free software: you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation, either version 3 of the License, or
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(at your option) any later version.
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solidity is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with solidity. If not, see <http://www.gnu.org/licenses/>.
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*/
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// SPDX-License-Identifier: GPL-3.0
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#pragma once
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#include <libsmtutil/SolverInterface.h>
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#include <libsolutil/LP.h>
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#include <libsolutil/CDCL.h>
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#include <boost/rational.hpp>
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#include <vector>
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#include <variant>
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#include <stack>
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namespace solidity::util
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{
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struct State
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{
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bool infeasible = false;
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std::map<std::string, size_t> variables;
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std::vector<bool> isBooleanVariable;
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// Potential constraints, referenced through clauses
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std::map<size_t, Constraint> conditionalConstraints;
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std::vector<Clause> clauses;
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// Unconditional bounds on variables
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std::map<size_t, SolvingState::Bounds> bounds;
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// Unconditional constraints
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std::vector<Constraint> fixedConstraints;
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};
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/**
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* Component that satisfies the SMT SolverInterface and uses an LP solver plus the CDCL
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* algorithm internally.
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* It uses a rational relaxation of the integer program and thus will not be able to answer
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* "satisfiable", but its answers are still correct.
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*
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* Contrary to the usual SMT type system, it adds an implicit constraint for all variables
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* and sub-expressions to be non-negative.
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* TODO this does not apply to e.g. `x + y - something`
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*
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* Integers are unbounded.
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*/
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class BooleanLPSolver: public smtutil::SolverInterface
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{
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public:
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void reset() override;
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void push() override;
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void pop() override;
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void declareVariable(std::string const& _name, smtutil::SortPointer const& _sort) override;
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void addAssertion(smtutil::Expression const& _expr) override;
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std::pair<smtutil::CheckResult, std::vector<std::string>>
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check(std::vector<smtutil::Expression> const& _expressionsToEvaluate) override;
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std::pair<smtutil::CheckResult, std::map<std::string, boost::rational<bigint>>> check();
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std::string toString() const;
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private:
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using rational = boost::rational<bigint>;
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smtutil::Expression declareInternalVariable(bool _boolean);
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void declareVariable(std::string const& _name, bool _boolean);
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/// Parses an expression of sort bool and returns a literal.
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std::optional<Literal> parseLiteral(smtutil::Expression const& _expr);
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Literal negate(Literal const& _lit);
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Literal parseLiteralOrReturnEqualBoolean(smtutil::Expression const& _expr);
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/// Parses the expression and expects a linear sum of variables.
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/// Returns a vector with the first element being the constant and the
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/// other elements the factors for the respective variables.
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/// If the expression cannot be properly parsed or is not linear,
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/// returns an empty vector.
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std::optional<LinearExpression> parseLinearSum(smtutil::Expression const& _expression);
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std::optional<LinearExpression> parseProduct(smtutil::Expression const& _expression) const;
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std::optional<LinearExpression> parseFactor(smtutil::Expression const& _expression) const;
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bool tryAddDirectBounds(Constraint const& _constraint);
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void addUpperBound(size_t _index, rational _value);
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void addLowerBound(size_t _index, rational _value);
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size_t addConditionalConstraint(Constraint _constraint);
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void addBooleanEquality(Literal const& _left, smtutil::Expression const& _right);
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//std::string toString(std::vector<SolvingState::Bounds> const& _bounds) const;
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std::string toString(Clause const& _clause) const;
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std::string toString(Constraint const& _constraint) const;
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Constraint const& conditionalConstraint(size_t _index) const;
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std::string variableName(size_t _index) const;
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bool isBooleanVariable(std::string const& _name) const;
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bool isBooleanVariable(size_t _index) const;
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bool isConditionalConstraint(size_t _index) const { return state().conditionalConstraints.count(_index); }
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State& state() { return m_state.back(); }
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State const& state() const { return m_state.back(); }
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/// Stack of state, to allow for push()/pop().
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std::vector<State> m_state{{State{}}};
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// TODO this is only here so that it can keep its cache.
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// It might be better to just have the cache here.
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// Although its stote is only the cache in the end...
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LPSolver m_lpSolver{false};
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};
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}
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