path: root/libjulia/optimiser/UnusedPruner.h

/*
    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/>.
*/
/**
 * Optimisation stage that removes unused variables and functions.
 */

#pragma once

#include <libjulia/optimiser/ASTWalker.h>

#include <string>
#include <map>
#include <set>

namespace dev
{
namespace julia
{

/**
 * Optimisation stage that removes unused variables and functions.
 *
 * TODO: Also remove intermediate variable assignments from movable expressions
 * which are not referenced until after the next assignment to the same variable.
 *
 * Note that this does not remove circular references.
 *
 * Prerequisite: Disambiguator
 */
class UnusedPruner: public ASTModifier
{
public:
    explicit UnusedPruner(Block& _ast);

    using ASTModifier::operator();
    virtual void operator()(Block& _block) override;

    // @returns true iff the code changed in the previous run.
    bool shouldRunAgain() const { return m_shouldRunAgain; }

    // Run the pruner until the code does not change anymore.
    static void runUntilStabilised(Block& _ast);

private:
    bool used(std::string const& _name) const;
    void subtractReferences(std::map<std::string, size_t> const& _subtrahend);

    bool m_shouldRunAgain = false;
    std::map<std::string, size_t> m_references;
};

}
}