/*

  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

/**

 * @author Alex Beregszaszi

 * Removes unused JUMPDESTs.

 */

#include <libevmasm/JumpdestRemover.h>

#include <libevmasm/AssemblyItem.h>

#include <limits>

using namespace std;

using namespace solidity;

using namespace solidity::util;

using namespace solidity::evmasm;

bool JumpdestRemover::optimise(set<size_t> const& _tagsReferencedFromOutside)

{

  set<size_t> references{referencedTags(m_items, numeric_limits<size_t>::max())};

  references.insert(_tagsReferencedFromOutside.begin(), _tagsReferencedFromOutside.end());

  size_t initialSize = m_items.size();

  /// Remove tags which are never referenced.

  auto pend = remove_if(

    m_items.begin(),

    m_items.end(),

    [&](AssemblyItem const& _item)

    {

      if (_item.type() != Tag)

        return false;

      auto asmIdAndTag = _item.splitForeignPushTag();

      assertThrow(asmIdAndTag.first == numeric_limits<size_t>::max(), OptimizerException, "Sub-assembly tag used as label.");

      size_t tag = asmIdAndTag.second;

      return !references.count(tag);

    }

  );

  m_items.erase(pend, m_items.end());

  return m_items.size() != initialSize;

}

set<size_t> JumpdestRemover::referencedTags(AssemblyItems const& _items, size_t _subId)

{

  set<size_t> ret;

  for (auto const& item: _items)

    if (item.type() == PushTag)

    {

      auto subAndTag = item.splitForeignPushTag();

      if (subAndTag.first == _subId)

        ret.insert(subAndTag.second);

    }

  return ret;

}