/*

  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

/**

 * Component that collects variables that are never assigned to and their

 * initial values.

 */

#pragma once

#include <libyul/optimiser/ASTWalker.h>

#include <libyul/AST.h> // Needed for m_zero below.

#include <map>

#include <set>

namespace solidity::yul

{

/**

 * Class that walks the AST and stores the initial value of each variable

 * that is never assigned to.

 *

 * A special zero constant expression is used for the default value of variables.

 *

 * Prerequisite: Disambiguator

 */

class SSAValueTracker: public ASTWalker

{

public:

  using ASTWalker::operator();

  void operator()(FunctionDefinition const& _funDef) override;

  void operator()(VariableDeclaration const& _varDecl) override;

  void operator()(Assignment const& _assignment) override;

  std::map<YulString, Expression const*> const& values() const { return m_values; }

  Expression const* value(YulString _name) const { return m_values.at(_name); }

  static std::set<YulString> ssaVariables(Block const& _ast);

private:

  void setValue(YulString _name, Expression const* _value);

  /// Special expression whose address will be used in m_values.

  /// YulString does not need to be reset because SSAValueTracker is short-lived.

  Expression const m_zero{Literal{{}, LiteralKind::Number, YulString{"0"}, {}}};

  std::map<YulString, Expression const*> m_values;

};

}