path: root/libyul/optimiser/VarDeclPropagator.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/>.
*/

#pragma once

#include <libyul/ASTDataForward.h>
#include <libyul/optimiser/ASTWalker.h>
#include <libyul/Exceptions.h>
#include <libsolidity/inlineasm/AsmDataForward.h>
#include <vector>
#include <set>
#include <map>

namespace dev
{
namespace yul
{

/**
 * Rewrites Assignment statements into VariableDeclaration when the assignment's LHS
 * variables had no value yet.
 *
 * It recursively walks through the AST and moves each declaration of variables to
 * the first assignment within the same block (if possible)..
 */
class VarDeclPropagator: public ASTModifier
{
public:
    using ASTModifier::operator();
    void operator()(Block& _block) override;
    void operator()(VariableDeclaration& _varDecl) override;
    void operator()(Assignment& _assignment) override;
    void operator()(Identifier& _ident) override;

private:
    bool allVarNamesUninitialized(std::vector<Identifier> const& _variableNames) const;
    bool isFullyLazyInitialized(std::vector<Identifier> const& _variableNames) const;
    VariableDeclaration recreateVariableDeclaration(Assignment& _assignment);

private:
    /// Holds a list of variables from current Block that have no value assigned yet.
    std::map<YulString, TypedName> m_emptyVarDecls;

    /// Holds a list variables (and their TypedName) within the current block.
    std::map<YulString, TypedName> m_lazyInitializedVarDecls;
};

}
}