Merge pull request #762 from chriseth/optimizer

Optimizer

libevmasm/Assembly.cpp

@@ -322,7 +322,8 @@ Assembly& Assembly::optimise(bool _enable, bool _isCreation, size_t _runs)
 			count++;
 
 		{
-			ControlFlowGraph cfg(m_items);
+			// Control flow graph that resets knowledge at path joins.
+			ControlFlowGraph cfg(m_items, false);
 			AssemblyItems optimisedItems;
 			for (BasicBlock const& block: cfg.optimisedBlocks())
 			{

libevmasm/ControlFlowGraph.cpp

@@ -250,7 +250,10 @@ void ControlFlowGraph::gatherKnowledge()
 		KnownStatePointer state = item.state;
 		if (block.startState)
 		{
+			if (m_joinKnowledge)
 				state->reduceToCommonKnowledge(*block.startState, !item.blocksSeen.count(item.blockId));
+			else
+				state->reset();
 			if (*state == *block.startState)
 				continue;
 		}

libevmasm/ControlFlowGraph.h

@@ -94,7 +94,11 @@ class ControlFlowGraph
 public:
 	/// Initializes the control flow graph.
 	/// @a _items has to persist across the usage of this class.
-	ControlFlowGraph(AssemblyItems const& _items): m_items(_items) {}
+	/// @a _joinKnowledge if true, reduces state knowledge to common base at the join of two paths
+	explicit ControlFlowGraph(AssemblyItems const& _items, bool _joinKnowledge = true):
+		m_items(_items),
+		m_joinKnowledge(_joinKnowledge)
+	{}
 	/// @returns vector of basic blocks in the order they should be used in the final code.
 	/// Should be called only once.
 	BasicBlocks optimisedBlocks();
@@ -112,6 +116,7 @@ private:
 
 	unsigned m_lastUsedId = 0;
 	AssemblyItems const& m_items;
+	bool m_joinKnowledge;
 	std::map<BlockId, BasicBlock> m_blocks;
 };
 

test/libsolidity/SolidityOptimizer.cpp

@@ -1177,6 +1177,64 @@ BOOST_AUTO_TEST_CASE(computing_constants)
 	) == optimizedBytecode.cend());
 }
 
+BOOST_AUTO_TEST_CASE(inconsistency)
+{
+	// This is a test of a bug in the optimizer.
+	char const* sourceCode = R"(
+		contract Inconsistency {
+			struct Value {
+				uint badnum;
+				uint number;
+			}
+
+			struct Container {
+				uint[] valueIndices;
+				Value[] values;
+			}
+
+			Container[] containers;
+			uint[] valueIndices;
+			uint INDEX_ZERO = 0;
+			uint  debug;
+
+			// Called with params: containerIndex=0, valueIndex=0
+			function levelIII(uint containerIndex, uint valueIndex) private {
+				Container container = containers[containerIndex];
+				Value value = container.values[valueIndex];
+				debug = container.valueIndices[value.number];
+			}
+			function levelII() private {
+				for (uint i = 0; i < valueIndices.length; i++) {
+					levelIII(INDEX_ZERO, valueIndices[i]);
+				}
+			}
+
+			function trigger() public returns (uint) {
+				containers.length++;
+				Container container = containers[0];
+
+				container.values.push(Value({
+					badnum: 9000,
+					number: 0
+				}));
+
+				container.valueIndices.length++;
+				valueIndices.length++;
+
+				levelII();
+				return debug;
+			}
+
+			function DoNotCallButDoNotDelete() public {
+				levelII();
+				levelIII(1, 2);
+			}
+		}
+	)";
+	compileBothVersions(sourceCode);
+	compareVersions("trigger()");
+}
+
 BOOST_AUTO_TEST_SUITE_END()
 
 }