aboutsummaryrefslogtreecommitdiffstats
path: root/libevmasm/BlockDeduplicator.cpp
diff options
context:
space:
mode:
authorDimitry <winsvega@mail.ru>2016-03-21 16:55:45 +0800
committerDimitry <winsvega@mail.ru>2016-03-21 16:55:45 +0800
commitb50e65437ebad535af29e84156b8b1af71f61c3d (patch)
treef2594fc7b539e5848f4fc08ebcfafedab90e00b5 /libevmasm/BlockDeduplicator.cpp
parent2fe6037b9bc42946dafbf0f870ca59546712d14c (diff)
downloaddexon-solidity-b50e65437ebad535af29e84156b8b1af71f61c3d.tar
dexon-solidity-b50e65437ebad535af29e84156b8b1af71f61c3d.tar.gz
dexon-solidity-b50e65437ebad535af29e84156b8b1af71f61c3d.tar.bz2
dexon-solidity-b50e65437ebad535af29e84156b8b1af71f61c3d.tar.lz
dexon-solidity-b50e65437ebad535af29e84156b8b1af71f61c3d.tar.xz
dexon-solidity-b50e65437ebad535af29e84156b8b1af71f61c3d.tar.zst
dexon-solidity-b50e65437ebad535af29e84156b8b1af71f61c3d.zip
move libevmasm
Diffstat (limited to 'libevmasm/BlockDeduplicator.cpp')
-rw-r--r--libevmasm/BlockDeduplicator.cpp126
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;
+}