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-rw-r--r--libevmasm/PeepholeOptimiser.cpp146
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diff --git a/libevmasm/PeepholeOptimiser.cpp b/libevmasm/PeepholeOptimiser.cpp
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+/*
+ 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 PeepholeOptimiser.h
+ * Performs local optimising code changes to assembly.
+ */
+
+#include "PeepholeOptimiser.h"
+
+#include <libevmasm/AssemblyItem.h>
+#include <libevmasm/SemanticInformation.h>
+
+using namespace std;
+using namespace dev::eth;
+using namespace dev;
+
+// TODO: Extend this to use the tools from ExpressionClasses.cpp
+
+struct Identity
+{
+ static size_t windowSize() { return 1; }
+ static bool apply(AssemblyItems::const_iterator _in, std::back_insert_iterator<AssemblyItems> _out)
+ {
+ *_out = *_in;
+ return true;
+ }
+};
+
+struct PushPop
+{
+ static size_t windowSize() { return 2; }
+ static bool apply(AssemblyItems::const_iterator _in, std::back_insert_iterator<AssemblyItems>)
+ {
+ auto t = _in[0].type();
+ if (_in[1] == Instruction::POP && (
+ SemanticInformation::isDupInstruction(_in[0]) ||
+ t == Push || t == PushString || t == PushTag || t == PushSub ||
+ t == PushSubSize || t == PushProgramSize || t == PushData || t == PushLibraryAddress
+ ))
+ return true;
+ else
+ return false;
+ }
+};
+
+struct DoubleSwap
+{
+ static size_t windowSize() { return 2; }
+ static bool apply(AssemblyItems::const_iterator _in, std::back_insert_iterator<AssemblyItems>)
+ {
+ if (_in[0] == _in[1] && SemanticInformation::isSwapInstruction(_in[0]))
+ return true;
+ else
+ return false;
+ }
+};
+
+struct JumpToNext
+{
+ static size_t windowSize() { return 3; }
+ static bool apply(AssemblyItems::const_iterator _in, std::back_insert_iterator<AssemblyItems> _out)
+ {
+ if (
+ _in[0].type() == PushTag &&
+ (_in[1] == Instruction::JUMP || _in[1] == Instruction::JUMPI) &&
+ _in[2].type() == Tag &&
+ _in[0].data() == _in[2].data()
+ )
+ {
+ *_out = _in[2];
+ return true;
+ }
+ else
+ return false;
+ }
+};
+
+struct TagConjunctions
+{
+ static size_t windowSize() { return 3; }
+ static bool apply(AssemblyItems::const_iterator _in, std::back_insert_iterator<AssemblyItems> _out)
+ {
+ if (
+ _in[0].type() == PushTag &&
+ _in[2] == Instruction::AND &&
+ _in[1].type() == Push &&
+ (_in[1].data() & u256(0xFFFFFFFF)) == u256(0xFFFFFFFF)
+ )
+ {
+ *_out = _in[0];
+ return true;
+ }
+ else
+ return false;
+ }
+};
+
+struct OptimiserState
+{
+ AssemblyItems const& items;
+ size_t i;
+ std::back_insert_iterator<AssemblyItems> out;
+};
+
+void applyMethods(OptimiserState&)
+{
+ assertThrow(false, OptimizerException, "Peephole optimizer failed to apply identity.");
+}
+
+template <typename Method, typename... OtherMethods>
+void applyMethods(OptimiserState& _state, Method, OtherMethods... _other)
+{
+ if (_state.i + Method::windowSize() <= _state.items.size() && Method::apply(_state.items.begin() + _state.i, _state.out))
+ _state.i += Method::windowSize();
+ else
+ applyMethods(_state, _other...);
+}
+
+bool PeepholeOptimiser::optimise()
+{
+ OptimiserState state {m_items, 0, std::back_inserter(m_optimisedItems)};
+ while (state.i < m_items.size())
+ applyMethods(state, PushPop(), DoubleSwap(), JumpToNext(), TagConjunctions(), Identity());
+ if (m_optimisedItems.size() < m_items.size())
+ {
+ m_items = std::move(m_optimisedItems);
+ return true;
+ }
+ else
+ return false;
+
+}