Merge pull request #2397 from ethereum/doublepush

Peephole optimizer for double push.

1 files changed, 20 insertions, 3 deletions

diff --git a/libevmasm/PeepholeOptimiser.cpp b/libevmasm/PeepholeOptimiser.cpp
index 6c92d76b..e94a8ba4 100644
--- a/libevmasm/PeepholeOptimiser.cpp
+++ b/libevmasm/PeepholeOptimiser.cpp
@@ -136,6 +136,21 @@ struct DoubleSwap: SimplePeepholeOptimizerMethod<DoubleSwap, 2>
 	}
 };
 
+struct DoublePush: SimplePeepholeOptimizerMethod<DoublePush, 2>
+{
+	static bool applySimple(AssemblyItem const& _push1, AssemblyItem const& _push2, std::back_insert_iterator<AssemblyItems> _out)
+	{
+		if (_push1.type() == Push && _push2.type() == Push && _push1.data() == _push2.data())
+		{
+			*_out = _push1;
+			*_out = {Instruction::DUP1, _push2.location()};
+			return true;
+		}
+		else
+			return false;
+	}
+};
+
 struct JumpToNext: SimplePeepholeOptimizerMethod<JumpToNext, 3>
 {
 	static size_t applySimple(
@@ -235,13 +250,15 @@ bool PeepholeOptimiser::optimise()
 {
 	OptimiserState state {m_items, 0, std::back_inserter(m_optimisedItems)};
 	while (state.i < m_items.size())
-		applyMethods(state, PushPop(), OpPop(), DoubleSwap(), JumpToNext(), UnreachableCode(), TagConjunctions(), Identity());
-	if (m_optimisedItems.size() < m_items.size())
+		applyMethods(state, PushPop(), OpPop(), DoublePush(), DoubleSwap(), JumpToNext(), UnreachableCode(), TagConjunctions(), Identity());
+	if (m_optimisedItems.size() < m_items.size() || (
+		m_optimisedItems.size() == m_items.size() &&
+		eth::bytesRequired(m_optimisedItems, 3) < eth::bytesRequired(m_items, 3)
+	))
 	{
 		m_items = std::move(m_optimisedItems);
 		return true;
 	}
 	else
 		return false;
-
 }