Add TruthyAnd Peephole optimization

3 files changed, 31 insertions, 1 deletions

diff --git a/Changelog.md b/Changelog.md
index 4389fbd9..b48433d6 100644
--- a/Changelog.md
+++ b/Changelog.md
@@ -15,6 +15,7 @@ Breaking Changes:
    ``implements``, ``macro``, ``mutable``, ``override``, ``partial``, ``promise``, ``reference``, ``sealed``,
    ``sizeof``, ``supports``, ``typedef`` and ``unchecked``.
  * General: Remove assembly instruction aliases ``sha3`` and ``suicide``
+ * Optimizer: Remove the no-op ``PUSH1 0 NOT AND`` sequence.
  * Parser: Disallow trailing dots that are not followed by a number.
  * Type Checker: Disallow arithmetic operations for boolean variables.
  * Type Checker: Disallow conversions between ``bytesX`` and ``uintY`` of different size.
diff --git a/libevmasm/PeepholeOptimiser.cpp b/libevmasm/PeepholeOptimiser.cpp
index 8a39de24..6d8e1df6 100644
--- a/libevmasm/PeepholeOptimiser.cpp
+++ b/libevmasm/PeepholeOptimiser.cpp
@@ -249,6 +249,23 @@ struct TagConjunctions: SimplePeepholeOptimizerMethod<TagConjunctions, 3>
 	}
 };
 
+struct TruthyAnd: SimplePeepholeOptimizerMethod<TruthyAnd, 3>
+{
+	static bool applySimple(
+		AssemblyItem const& _push,
+		AssemblyItem const& _not,
+		AssemblyItem const& _and,
+		std::back_insert_iterator<AssemblyItems>
+	)
+	{
+		return (
+			_push.type() == Push && _push.data() == 0 &&
+			_not == Instruction::NOT &&
+			_and == Instruction::AND
+		);
+	}
+};
+
 /// Removes everything after a JUMP (or similar) until the next JUMPDEST.
 struct UnreachableCode
 {
@@ -305,7 +322,7 @@ 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(), SwapComparison(), JumpToNext(), UnreachableCode(), TagConjunctions(), Identity());
+		applyMethods(state, PushPop(), OpPop(), DoublePush(), DoubleSwap(), CommutativeSwap(), SwapComparison(), JumpToNext(), UnreachableCode(), TagConjunctions(), TruthyAnd(), Identity());
 	if (m_optimisedItems.size() < m_items.size() || (
 		m_optimisedItems.size() == m_items.size() && (
 			eth::bytesRequired(m_optimisedItems, 3) < eth::bytesRequired(m_items, 3) ||
diff --git a/test/libevmasm/Optimiser.cpp b/test/libevmasm/Optimiser.cpp
index 4b399a14..8e4946c3 100644
--- a/test/libevmasm/Optimiser.cpp
+++ b/test/libevmasm/Optimiser.cpp
@@ -967,6 +967,18 @@ BOOST_AUTO_TEST_CASE(peephole_swap_comparison)
 	}
 }
 
+BOOST_AUTO_TEST_CASE(peephole_truthy_and)
+{
+  AssemblyItems items{
+    u256(0),
+    Instruction::NOT,
+    Instruction::AND
+  };
+  PeepholeOptimiser peepOpt(items);
+  BOOST_REQUIRE(peepOpt.optimise());
+  BOOST_CHECK(items.empty());
+}
+
 BOOST_AUTO_TEST_CASE(jumpdest_removal)
 {
 	AssemblyItems items{