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author | Dimitry <winsvega@mail.ru> | 2016-03-21 16:55:45 +0800 |
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committer | Dimitry <winsvega@mail.ru> | 2016-03-21 16:55:45 +0800 |
commit | b50e65437ebad535af29e84156b8b1af71f61c3d (patch) | |
tree | f2594fc7b539e5848f4fc08ebcfafedab90e00b5 /libevmasm/BlockDeduplicator.cpp | |
parent | 2fe6037b9bc42946dafbf0f870ca59546712d14c (diff) | |
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move libevmasm
Diffstat (limited to 'libevmasm/BlockDeduplicator.cpp')
-rw-r--r-- | libevmasm/BlockDeduplicator.cpp | 126 |
1 files changed, 126 insertions, 0 deletions
diff --git a/libevmasm/BlockDeduplicator.cpp b/libevmasm/BlockDeduplicator.cpp new file mode 100644 index 00000000..d930ea22 --- /dev/null +++ b/libevmasm/BlockDeduplicator.cpp @@ -0,0 +1,126 @@ +/* + This file is part of cpp-ethereum. + + cpp-ethereum 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. + + cpp-ethereum 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 cpp-ethereum. If not, see <http://www.gnu.org/licenses/>. +*/ +/** + * @file BlockDeduplicator.cpp + * @author Christian <c@ethdev.com> + * @date 2015 + * Unifies basic blocks that share content. + */ + +#include <libevmasm/BlockDeduplicator.h> +#include <functional> +#include <libevmasm/AssemblyItem.h> +#include <libevmasm/SemanticInformation.h> + +using namespace std; +using namespace dev; +using namespace dev::eth; + + +bool BlockDeduplicator::deduplicate() +{ + // Compares indices based on the suffix that starts there, ignoring tags and stopping at + // opcodes that stop the control flow. + + // Virtual tag that signifies "the current block" and which is used to optimise loops. + // We abort if this virtual tag actually exists. + AssemblyItem pushSelf(PushTag, u256(-4)); + if ( + std::count(m_items.cbegin(), m_items.cend(), pushSelf.tag()) || + std::count(m_items.cbegin(), m_items.cend(), pushSelf.pushTag()) + ) + return false; + + function<bool(size_t, size_t)> comparator = [&](size_t _i, size_t _j) + { + if (_i == _j) + return false; + + // To compare recursive loops, we have to already unify PushTag opcodes of the + // block's own tag. + AssemblyItem pushFirstTag(pushSelf); + AssemblyItem pushSecondTag(pushSelf); + + if (_i < m_items.size() && m_items.at(_i).type() == Tag) + pushFirstTag = m_items.at(_i).pushTag(); + if (_j < m_items.size() && m_items.at(_j).type() == Tag) + pushSecondTag = m_items.at(_j).pushTag(); + + BlockIterator first(m_items.begin() + _i, m_items.end(), &pushFirstTag, &pushSelf); + BlockIterator second(m_items.begin() + _j, m_items.end(), &pushSecondTag, &pushSelf); + BlockIterator end(m_items.end(), m_items.end()); + + if (first != end && (*first).type() == Tag) + ++first; + if (second != end && (*second).type() == Tag) + ++second; + + return std::lexicographical_compare(first, end, second, end); + }; + + size_t iterations = 0; + for (; ; ++iterations) + { + //@todo this should probably be optimized. + set<size_t, function<bool(size_t, size_t)>> blocksSeen(comparator); + map<u256, u256> tagReplacement; + for (size_t i = 0; i < m_items.size(); ++i) + { + if (m_items.at(i).type() != Tag) + continue; + auto it = blocksSeen.find(i); + if (it == blocksSeen.end()) + blocksSeen.insert(i); + else + tagReplacement[m_items.at(i).data()] = m_items.at(*it).data(); + } + + bool changed = false; + for (AssemblyItem& item: m_items) + if (item.type() == PushTag && tagReplacement.count(item.data())) + { + changed = true; + item.setData(tagReplacement.at(item.data())); + } + if (!changed) + break; + } + return iterations > 0; +} + +BlockDeduplicator::BlockIterator& BlockDeduplicator::BlockIterator::operator++() +{ + if (it == end) + return *this; + if (SemanticInformation::altersControlFlow(*it) && *it != AssemblyItem(eth::Instruction::JUMPI)) + it = end; + else + { + ++it; + while (it != end && it->type() == Tag) + ++it; + } + return *this; +} + +AssemblyItem const& BlockDeduplicator::BlockIterator::operator*() const +{ + if (replaceItem && replaceWith && *it == *replaceItem) + return *replaceWith; + else + return *it; +} |