Unify blocks with shared code.

1 files changed, 93 insertions, 0 deletions

diff --git a/BlockDeduplicator.cpp b/BlockDeduplicator.cpp
new file mode 100644
index 00000000..ca4f7e21
--- /dev/null
+++ b/BlockDeduplicator.cpp
@@ -0,0 +1,93 @@
+/*
+	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>
+
+#include <libdevcore/CommonIO.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.
+	function<bool(size_t, size_t)> comparator = [&](size_t _i, size_t _j)
+	{
+		if (_i == _j)
+			return false;
+
+		BlockIterator first(m_items.begin() + _i, m_items.end());
+		BlockIterator second(m_items.begin() + _j, m_items.end());
+		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);
+	};
+
+	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 ret = false;
+	for (AssemblyItem& item: m_items)
+		if (item.type() == PushTag && tagReplacement.count(item.data()))
+		{
+			ret = true;
+			item.setData(tagReplacement.at(item.data()));
+		}
+	return ret;
+}
+
+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;
+}