CFG returns vector of blocks instead of assembly items.

Assembly.cpp

@@ -318,7 +318,10 @@ Assembly& Assembly::optimise(bool _enable)
 		copt << "Performing control flow analysis...";
 		{
 			ControlFlowGraph cfg(m_items);
-			AssemblyItems optItems = cfg.optimisedItems();
+			AssemblyItems optItems;
+			for (BasicBlock const& block: cfg.optimisedBlocks())
+				copy(m_items.begin() + block.begin, m_items.begin() + block.end,
+					 back_inserter(optItems));
 			if (optItems.size() < m_items.size())
 			{
 				copt << "Old size: " << m_items.size() << ", new size: " << optItems.size();

ControlFlowGraph.cpp

@@ -38,10 +38,10 @@ BlockId::BlockId(u256 const& _id): m_id(_id)
 	assertThrow( _id < initial().m_id, OptimizerException, "Tag number too large.");
 }
 
-AssemblyItems ControlFlowGraph::optimisedItems()
+BasicBlocks ControlFlowGraph::optimisedBlocks()
 {
 	if (m_items.empty())
-		return m_items;
+		return BasicBlocks();
 
 	findLargestTag();
 	splitBlocks();
@@ -216,17 +216,17 @@ void ControlFlowGraph::gatherKnowledge()
 {
 	// @todo actually we know that memory is filled with zeros at the beginning,
 	// we could make use of that.
-	shared_ptr<KnownState> emptyState = make_shared<KnownState>();
+	KnownStatePointer emptyState = make_shared<KnownState>();
 	ExpressionClasses& expr = emptyState->expressionClasses();
 	bool unknownJumpEncountered = false;
 
-	vector<pair<BlockId, shared_ptr<KnownState>>> workQueue({make_pair(BlockId::initial(), emptyState->copy())});
+	vector<pair<BlockId, KnownStatePointer>> workQueue({make_pair(BlockId::initial(), emptyState->copy())});
 	while (!workQueue.empty())
 	{
 		//@todo we might have to do something like incrementing the sequence number for each JUMPDEST
 		assertThrow(!!workQueue.back().first, OptimizerException, "");
 		BasicBlock& block = m_blocks.at(workQueue.back().first);
-		shared_ptr<KnownState> state = workQueue.back().second;
+		KnownStatePointer state = workQueue.back().second;
 		workQueue.pop_back();
 		if (block.startState)
 		{
@@ -283,7 +283,7 @@ void ControlFlowGraph::gatherKnowledge()
 	}
 }
 
-AssemblyItems ControlFlowGraph::rebuildCode()
+BasicBlocks ControlFlowGraph::rebuildCode()
 {
 	map<BlockId, unsigned> pushes;
 	for (auto& idAndBlock: m_blocks)
@@ -294,7 +294,7 @@ AssemblyItems ControlFlowGraph::rebuildCode()
 	for (auto it: m_blocks)
 		blocksToAdd.insert(it.first);
 	set<BlockId> blocksAdded;
-	AssemblyItems code;
+	BasicBlocks blocks;
 
 	for (
 		BlockId blockId = BlockId::initial();
@@ -311,22 +311,18 @@ AssemblyItems ControlFlowGraph::rebuildCode()
 			blocksToAdd.erase(blockId);
 			blocksAdded.insert(blockId);
 
-			auto begin = m_items.begin() + block.begin;
+			if (block.begin == block.end)
-			auto end = m_items.begin() + block.end;
-			if (begin == end)
 				continue;
 			// If block starts with unused tag, skip it.
-			if (previousHandedOver && !pushes[blockId] && begin->type() == Tag)
+			if (previousHandedOver && !pushes[blockId] && m_items[block.begin].type() == Tag)
-			{
-				++begin;
 				++block.begin;
-			}
+			if (block.begin < block.end)
+				blocks.push_back(block);
 			previousHandedOver = (block.endType == BasicBlock::EndType::HANDOVER);
-			copy(begin, end, back_inserter(code));
 		}
 	}
 
-	return code;
+	return blocks;
 }
 
 BlockId ControlFlowGraph::expressionClassToBlockId(

ControlFlowGraph.h

@@ -35,6 +35,7 @@ namespace eth
 {
 
 class KnownState;
+using KnownStatePointer = std::shared_ptr<KnownState>;
 
 /**
  * Identifier for a block, coincides with the tag number of an AssemblyItem but adds a special
@@ -81,19 +82,22 @@ struct BasicBlock
 
 	/// Knowledge about the state when this block is entered. Intersection of all possible ways
 	/// to enter this block.
-	std::shared_ptr<KnownState> startState;
+	KnownStatePointer startState;
 	/// Knowledge about the state at the end of this block.
-	std::shared_ptr<KnownState> endState;
+	KnownStatePointer endState;
 };
 
+using BasicBlocks = std::vector<BasicBlock>;
+
 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) {}
-	/// @returns the collection of optimised items, should be called only once.
+	/// @returns vector of basic blocks in the order they should be used in the final code.
-	AssemblyItems optimisedItems();
+	/// Should be called only once.
+	BasicBlocks optimisedBlocks();
 
 private:
 	void findLargestTag();
@@ -102,7 +106,7 @@ private:
 	void removeUnusedBlocks();
 	void gatherKnowledge();
 	void setPrevLinks();
-	AssemblyItems rebuildCode();
+	BasicBlocks rebuildCode();
 
 	/// @returns the corresponding BlockId if _id is a pushed jump tag,
 	/// and an invalid BlockId otherwise.