From 17bcabb6cfb42a3983ecb79768d44622507ce292 Mon Sep 17 00:00:00 2001
From: Alex Beregszaszi <alex@rtfs.hu>
Date: Thu, 29 Mar 2018 12:10:39 +0100
Subject: Remove useless SWAP1 in front of commutative operations

---
 libevmasm/PeepholeOptimiser.cpp | 21 ++++++++++++++++++++-
 1 file changed, 20 insertions(+), 1 deletion(-)

(limited to 'libevmasm/PeepholeOptimiser.cpp')

diff --git a/libevmasm/PeepholeOptimiser.cpp b/libevmasm/PeepholeOptimiser.cpp
index 168d1109..30646545 100644
--- a/libevmasm/PeepholeOptimiser.cpp
+++ b/libevmasm/PeepholeOptimiser.cpp
@@ -154,6 +154,25 @@ struct DoublePush: SimplePeepholeOptimizerMethod<DoublePush, 2>
 	}
 };
 
+struct CommutativeSwap: SimplePeepholeOptimizerMethod<CommutativeSwap, 2>
+{
+	static bool applySimple(AssemblyItem const& _swap, AssemblyItem const& _op, std::back_insert_iterator<AssemblyItems> _out)
+	{
+		// Remove SWAP1 if following instruction is commutative
+		if (
+			_swap.type() == Operation &&
+			_swap.instruction() == Instruction::SWAP1 &&
+			SemanticInformation::isCommutativeOperation(_op)
+		)
+		{
+			*_out = _op;
+			return true;
+		}
+		else
+			return false;
+	}
+};
+
 struct JumpToNext: SimplePeepholeOptimizerMethod<JumpToNext, 3>
 {
 	static size_t applySimple(
@@ -260,7 +279,7 @@ bool PeepholeOptimiser::optimise()
 {
 	OptimiserState state {m_items, 0, std::back_inserter(m_optimisedItems)};
 	while (state.i < m_items.size())
-		applyMethods(state, PushPop(), OpPop(), DoublePush(), DoubleSwap(), JumpToNext(), UnreachableCode(), TagConjunctions(), Identity());
+		applyMethods(state, PushPop(), OpPop(), DoublePush(), DoubleSwap(), CommutativeSwap(), 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) ||
-- 
cgit v1.2.3


From 02ea0e547f3faa687f9c986ca9a0201b995846c0 Mon Sep 17 00:00:00 2001
From: Alex Beregszaszi <alex@rtfs.hu>
Date: Wed, 4 Apr 2018 15:28:15 +0200
Subject: Replace comparison operators with opposites if preceded by SWAP1

---
 libevmasm/PeepholeOptimiser.cpp | 28 +++++++++++++++++++++++++++-
 1 file changed, 27 insertions(+), 1 deletion(-)

(limited to 'libevmasm/PeepholeOptimiser.cpp')

diff --git a/libevmasm/PeepholeOptimiser.cpp b/libevmasm/PeepholeOptimiser.cpp
index 30646545..8a39de24 100644
--- a/libevmasm/PeepholeOptimiser.cpp
+++ b/libevmasm/PeepholeOptimiser.cpp
@@ -173,6 +173,32 @@ struct CommutativeSwap: SimplePeepholeOptimizerMethod<CommutativeSwap, 2>
 	}
 };
 
+struct SwapComparison: SimplePeepholeOptimizerMethod<SwapComparison, 2>
+{
+	static bool applySimple(AssemblyItem const& _swap, AssemblyItem const& _op, std::back_insert_iterator<AssemblyItems> _out)
+	{
+		map<Instruction, Instruction> swappableOps{
+			{ Instruction::LT, Instruction::GT },
+			{ Instruction::GT, Instruction::LT },
+			{ Instruction::SLT, Instruction::SGT },
+			{ Instruction::SGT, Instruction::SLT }
+		};
+
+		if (
+			_swap.type() == Operation &&
+			_swap.instruction() == Instruction::SWAP1 &&
+			_op.type() == Operation &&
+			swappableOps.count(_op.instruction())
+		)
+		{
+			*_out = swappableOps.at(_op.instruction());
+			return true;
+		}
+		else
+			return false;
+	}
+};
+
 struct JumpToNext: SimplePeepholeOptimizerMethod<JumpToNext, 3>
 {
 	static size_t applySimple(
@@ -279,7 +305,7 @@ bool PeepholeOptimiser::optimise()
 {
 	OptimiserState state {m_items, 0, std::back_inserter(m_optimisedItems)};
 	while (state.i < m_items.size())
-		applyMethods(state, PushPop(), OpPop(), DoublePush(), DoubleSwap(), CommutativeSwap(), JumpToNext(), UnreachableCode(), TagConjunctions(), Identity());
+		applyMethods(state, PushPop(), OpPop(), DoublePush(), DoubleSwap(), CommutativeSwap(), SwapComparison(), 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) ||
-- 
cgit v1.2.3