path: root/libyul/optimiser/VarDeclPropagator.cpp

/*
    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/>.
*/

#include <libyul/optimiser/VarDeclPropagator.h>
#include <libyul/AsmData.h>
#include <libdevcore/CommonData.h>
#include <boost/range/algorithm_ext/erase.hpp>
#include <algorithm>
#include <map>

using namespace std;
using namespace dev;
using namespace yul;

void VarDeclPropagator::operator()(Block& _block)
{
    map<YulString, TypedName> outerEmptyVarDecls;
    map<YulString, TypedName> outerLazyInitializedVarDecls;
    swap(m_emptyVarDecls, outerEmptyVarDecls);
    swap(m_lazyInitializedVarDecls, outerLazyInitializedVarDecls);

    ASTModifier::operator()(_block);

    iterateReplacing(
        _block.statements,
        [this](Statement& _stmt) -> boost::optional<vector<Statement>>
        {
            if (_stmt.type() == typeid(VariableDeclaration))
            {
                VariableDeclaration& varDecl = boost::get<VariableDeclaration>(_stmt);
                boost::remove_erase_if(
                    varDecl.variables,
                    [&](TypedName const& _typedName) { return m_lazyInitializedVarDecls.count(_typedName.name); }
                );
                if (varDecl.variables.empty())
                    return vector<Statement>{};
                else
                    return {};
            }
            else if (_stmt.type() == typeid(Assignment))
            {
                Assignment& assignment = boost::get<Assignment>(_stmt);
                if (isFullyLazyInitialized(assignment.variableNames))
                    return vector<Statement>{recreateVariableDeclaration(assignment)};
                else
                    return {};
            }
            else
                return {};
        }
    );

    swap(m_emptyVarDecls, outerEmptyVarDecls);
    swap(m_lazyInitializedVarDecls, outerLazyInitializedVarDecls);
}

void VarDeclPropagator::operator()(VariableDeclaration& _varDecl)
{
    if (_varDecl.value)
        visit(*_varDecl.value);
    else
        for (TypedName const& typedName: _varDecl.variables)
            m_emptyVarDecls[typedName.name] = typedName;
}

void VarDeclPropagator::operator()(Assignment& _assignment)
{
    visit(*_assignment.value);

    if (allVarNamesUninitialized(_assignment.variableNames))
        for (Identifier const& ident: _assignment.variableNames)
            m_lazyInitializedVarDecls[ident.name] = m_emptyVarDecls[ident.name];

    for (Identifier& name: _assignment.variableNames)
        (*this)(name);
}

void VarDeclPropagator::operator()(Identifier& _ident)
{
    m_emptyVarDecls.erase(_ident.name);
}

bool VarDeclPropagator::allVarNamesUninitialized(vector<Identifier> const& _variableNames) const
{
    return all_of(
        begin(_variableNames),
        end(_variableNames),
        [&](Identifier const& _ident) -> bool { return m_emptyVarDecls.count(_ident.name); }
    );
}

bool VarDeclPropagator::isFullyLazyInitialized(vector<Identifier> const& _variableNames) const
{
    return all_of(
        begin(_variableNames),
        end(_variableNames),
        [&](Identifier const& ident) -> bool { return m_lazyInitializedVarDecls.count(ident.name); }
    );
}

VariableDeclaration VarDeclPropagator::recreateVariableDeclaration(Assignment& _assignment)
{
    TypedNameList variables;

    for (Identifier const& varName: _assignment.variableNames)
    {
        variables.emplace_back(move(m_lazyInitializedVarDecls.at(varName.name)));
        m_lazyInitializedVarDecls.erase(varName.name);
    }

    return VariableDeclaration{move(_assignment.location), move(variables), std::move(_assignment.value)};
}