/*

  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 unused variables and functions.

 */

#pragma once

#include <libyul/optimiser/ASTWalker.h>

#include <libyul/YulName.h>

#include <libyul/ControlFlowSideEffects.h>

#include <map>

#include <set>

namespace solidity::yul

{

class Dialect;

struct OptimiserStepContext;

/**

 * Optimisation stage that removes unreachable code

 *

 * Unreachable code is any code within a block which is preceded by a

 * leave, return, invalid, break, continue, selfdestruct or revert or

 * a call to a user-defined function that never returns (either due to

 * recursion or a call to return / revert / stop).

 *

 * Function definitions are retained as they might be called by earlier

 * code and thus are considered reachable.

 *

 * Because variables declared in a for loop's init block have their scope extended to the loop body,

 * we require ForLoopInitRewriter to run before this step.

 *

 * Prerequisite: ForLoopInitRewriter, Function Hoister, Function Grouper

 */

class DeadCodeEliminator: public ASTModifier

{

public:

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

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

  using ASTModifier::operator();

  void operator()(ForLoop& _for) override;

  void operator()(Block& _block) override;

private:

  DeadCodeEliminator(

    Dialect const& _dialect,

    std::map<YulName, ControlFlowSideEffects> _sideEffects

  ): m_dialect(_dialect), m_functionSideEffects(std::move(_sideEffects)) {}

  Dialect const& m_dialect;

  std::map<YulName, ControlFlowSideEffects> m_functionSideEffects;

};

}