Reuse state during common subexpression elimination.

1 files changed, 36 insertions, 44 deletions

diff --git a/Assembly.cpp b/Assembly.cpp
index 9530ded4..abcd4451 100644
--- a/Assembly.cpp
+++ b/Assembly.cpp
@@ -311,54 +311,45 @@ Assembly& Assembly::optimise(bool _enable)
 		copt << toString(*this);
 		count = 0;
 
-		//@todo CFG interface should be a generator, that returns an item and a pointer to a
-		// knownstate, which has to replace the current state if it is not null.
-		// Feed these items to the CSE, but also store them and replace the stored version
-		// if the items generated by the CSE are shorter. (or even use less gas?)
-		copt << "Performing control flow analysis...";
+		copt << "Performing optimisation...";
 		{
 			ControlFlowGraph cfg(m_items);
-			AssemblyItems optItems;
+			AssemblyItems optimisedItems;
 			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();
-				m_items = move(optItems);
-				count++;
-			}
-		}
-
-		copt << "Performing common subexpression elimination...";
-		for (auto iter = m_items.begin(); iter != m_items.end();)
-		{
-			//@todo use only a single state / expression classes instance.
-			KnownState state(make_shared<ExpressionClasses>());
-			CommonSubexpressionEliminator eliminator(state);
-			auto orig = iter;
-			iter = eliminator.feedItems(iter, m_items.end());
-			AssemblyItems optItems;
-			bool shouldReplace = false;
-			try
-			{
-				optItems = eliminator.getOptimizedItems();
-				shouldReplace = (optItems.size() < size_t(iter - orig));
-			}
-			catch (StackTooDeepException const&)
-			{
-				// This might happen if the opcode reconstruction is not as efficient
-				// as the hand-crafted code.
-			}
-
-			if (shouldReplace)
-			{
-				copt << "Old size: " << (iter - orig) << ", new size: " << optItems.size();
-				count++;
-				for (auto moveIter = optItems.begin(); moveIter != optItems.end(); ++orig, ++moveIter)
-					*orig = move(*moveIter);
-				iter = m_items.erase(orig, iter);
+				assertThrow(!!block.startState, OptimizerException, "");
+				CommonSubexpressionEliminator eliminator(*block.startState);
+				auto iter = m_items.begin() + block.begin;
+				auto const end = m_items.begin() + block.end;
+				while (iter < end)
+				{
+					auto orig = iter;
+					iter = eliminator.feedItems(iter, end);
+					bool shouldReplace = false;
+					AssemblyItems optimisedChunk;
+					try
+					{
+						optimisedChunk = eliminator.getOptimizedItems();
+						shouldReplace = (optimisedChunk.size() < size_t(iter - orig));
+					}
+					catch (StackTooDeepException const&)
+					{
+						// This might happen if the opcode reconstruction is not as efficient
+						// as the hand-crafted code.
+					}
+
+					if (shouldReplace)
+					{
+						copt << "Old size: " << (iter - orig) << ", new size: " << optimisedChunk.size();
+						count++;
+						optimisedItems += optimisedChunk;
+					}
+					else
+						copy(orig, iter, back_inserter(optimisedItems));
+				}
 			}
+			if (optimisedItems.size() < m_items.size())
+				m_items = move(optimisedItems);
 		}
 	}
 
@@ -461,7 +452,8 @@ bytes Assembly::assemble() const
 	for (auto const& i: tagRef)
 	{
 		bytesRef r(ret.data() + i.first, bytesPerTag);
-		toBigEndian(tagPos[i.second], r);
+		//@todo in the failure case, we could use the position of the invalid jumpdest
+		toBigEndian(i.second < tagPos.size() ? tagPos[i.second] : (1 << (8 * bytesPerTag)) - 1, r);
 	}
 
 	if (!m_data.empty())