/*

  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

/**

 * Optimisation stage that removes mstore and sstore operations if they store the same

 * value that is already known to be in that slot.

 */

#pragma once

#include <libyul/optimiser/DataFlowAnalyzer.h>

#include <libyul/optimiser/OptimiserStep.h>

namespace solidity::yul

{

/**

 * Optimisation stage that removes mstore and sstore operations if they store the same

 * value that is already known to be in that slot.

 *

 * Works best if the code is in SSA form - without literal arguments.

 *

 * Prerequisite: Disambiguator, ForLoopInitRewriter.

 */

class EqualStoreEliminator: public DataFlowAnalyzer

{

public:

  static constexpr char const* name{"EqualStoreEliminator"};

  static void run(OptimiserStepContext const&, Block& _ast);

private:

  EqualStoreEliminator(

    Dialect const& _dialect,

    std::map<FunctionHandle, SideEffects> _functionSideEffects

  ):

    DataFlowAnalyzer(_dialect, MemoryAndStorage::Analyze, std::move(_functionSideEffects))

  {}

protected:

  using ASTModifier::visit;

  void visit(Statement& _statement) override;

  std::set<Statement const*> m_pendingRemovals;

};

}