path: root/libevmasm/BlockDeduplicator.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/>.
*/
/**
 * @file BlockDeduplicator.h
 * @author Christian <c@ethdev.com>
 * @date 2015
 * Unifies basic blocks that share content.
 */

#pragma once

#include <libdevcore/Common.h>

#include <cstddef>
#include <vector>
#include <functional>
#include <map>

namespace dev
{
namespace eth
{

class AssemblyItem;
using AssemblyItems = std::vector<AssemblyItem>;

/**
 * Optimizer class to be used to unify blocks that share content.
 * Modifies the passed vector in place.
 */
class BlockDeduplicator
{
public:
    BlockDeduplicator(AssemblyItems& _items): m_items(_items) {}
    /// @returns true if something was changed
    bool deduplicate();
    /// @returns the tags that were replaced.
    std::map<u256, u256> const& replacedTags() const { return m_replacedTags; }

    /// Replaces all PushTag operations insied @a _items that match a key in
    /// @a _replacements by the respective value. If @a _subID is not -1, only
    /// apply the replacement for foreign tags from this sub id.
    /// @returns true iff a replacement was performed.
    static bool applyTagReplacement(
        AssemblyItems& _items,
        std::map<u256, u256> const& _replacements,
        size_t _subID = size_t(-1)
    );

private:
    /// Iterator that skips tags and skips to the end if (all branches of) the control
    /// flow does not continue to the next instruction.
    /// If the arguments are supplied to the constructor, replaces items on the fly.
    struct BlockIterator: std::iterator<std::forward_iterator_tag, AssemblyItem const>
    {
    public:
        BlockIterator(
            AssemblyItems::const_iterator _it,
            AssemblyItems::const_iterator _end,
            AssemblyItem const* _replaceItem = nullptr,
            AssemblyItem const* _replaceWith = nullptr
        ):
            it(_it), end(_end), replaceItem(_replaceItem), replaceWith(_replaceWith) {}
        BlockIterator& operator++();
        bool operator==(BlockIterator const& _other) const { return it == _other.it; }
        bool operator!=(BlockIterator const& _other) const { return it != _other.it; }
        AssemblyItem const& operator*() const;
        AssemblyItems::const_iterator it;
        AssemblyItems::const_iterator end;
        AssemblyItem const* replaceItem;
        AssemblyItem const* replaceWith;
    };

    std::map<u256, u256> m_replacedTags;
    AssemblyItems& m_items;
};

}
}