mirror of
https://github.com/ethereum/solidity
synced 2023-10-03 13:03:40 +00:00
127 lines
3.6 KiB
C++
127 lines
3.6 KiB
C++
/*
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This file is part of cpp-ethereum.
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cpp-ethereum is free software: you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation, either version 3 of the License, or
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(at your option) any later version.
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cpp-ethereum is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with cpp-ethereum. If not, see <http://www.gnu.org/licenses/>.
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*/
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/**
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* @file BlockDeduplicator.cpp
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* @author Christian <c@ethdev.com>
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* @date 2015
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* Unifies basic blocks that share content.
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*/
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#include <libevmasm/BlockDeduplicator.h>
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#include <functional>
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#include <libevmasm/AssemblyItem.h>
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#include <libevmasm/SemanticInformation.h>
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using namespace std;
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using namespace dev;
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using namespace dev::eth;
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bool BlockDeduplicator::deduplicate()
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{
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// Compares indices based on the suffix that starts there, ignoring tags and stopping at
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// opcodes that stop the control flow.
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// Virtual tag that signifies "the current block" and which is used to optimise loops.
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// We abort if this virtual tag actually exists.
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AssemblyItem pushSelf(PushTag, u256(-4));
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if (
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std::count(m_items.cbegin(), m_items.cend(), pushSelf.tag()) ||
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std::count(m_items.cbegin(), m_items.cend(), pushSelf.pushTag())
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)
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return false;
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function<bool(size_t, size_t)> comparator = [&](size_t _i, size_t _j)
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{
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if (_i == _j)
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return false;
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// To compare recursive loops, we have to already unify PushTag opcodes of the
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// block's own tag.
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AssemblyItem pushFirstTag(pushSelf);
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AssemblyItem pushSecondTag(pushSelf);
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if (_i < m_items.size() && m_items.at(_i).type() == Tag)
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pushFirstTag = m_items.at(_i).pushTag();
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if (_j < m_items.size() && m_items.at(_j).type() == Tag)
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pushSecondTag = m_items.at(_j).pushTag();
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BlockIterator first(m_items.begin() + _i, m_items.end(), &pushFirstTag, &pushSelf);
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BlockIterator second(m_items.begin() + _j, m_items.end(), &pushSecondTag, &pushSelf);
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BlockIterator end(m_items.end(), m_items.end());
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if (first != end && (*first).type() == Tag)
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++first;
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if (second != end && (*second).type() == Tag)
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++second;
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return std::lexicographical_compare(first, end, second, end);
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};
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size_t iterations = 0;
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for (; ; ++iterations)
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{
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//@todo this should probably be optimized.
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set<size_t, function<bool(size_t, size_t)>> blocksSeen(comparator);
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map<u256, u256> tagReplacement;
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for (size_t i = 0; i < m_items.size(); ++i)
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{
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if (m_items.at(i).type() != Tag)
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continue;
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auto it = blocksSeen.find(i);
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if (it == blocksSeen.end())
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blocksSeen.insert(i);
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else
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tagReplacement[m_items.at(i).data()] = m_items.at(*it).data();
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}
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bool changed = false;
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for (AssemblyItem& item: m_items)
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if (item.type() == PushTag && tagReplacement.count(item.data()))
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{
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changed = true;
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item.setData(tagReplacement.at(item.data()));
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}
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if (!changed)
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break;
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}
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return iterations > 0;
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}
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BlockDeduplicator::BlockIterator& BlockDeduplicator::BlockIterator::operator++()
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{
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if (it == end)
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return *this;
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if (SemanticInformation::altersControlFlow(*it) && *it != AssemblyItem(eth::Instruction::JUMPI))
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it = end;
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else
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{
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++it;
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while (it != end && it->type() == Tag)
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++it;
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}
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return *this;
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}
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AssemblyItem const& BlockDeduplicator::BlockIterator::operator*() const
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{
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if (replaceItem && replaceWith && *it == *replaceItem)
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return *replaceWith;
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else
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return *it;
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}
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