Merge pull request #11824 from ethereum/yulControlFlowGraphRecursiveCalls

Mark recursive calls in yul control flow graph.

Author: ekpyron

libyul/backends/evm/ControlFlowGraph.h

@@ -131,6 +131,9 @@ struct CFG
 		std::shared_ptr<DebugData const> debugData;
 		std::reference_wrapper<Scope::Function const> function;
 		std::reference_wrapper<yul::FunctionCall const> functionCall;
+		/// True, if the call is recursive, i.e. entering the function involves a control flow path (potentially involving
+		/// more intermediate function calls) that leads back to this very call.
+		bool recursive = false;
 	};
 	struct Assignment
 	{

libyul/backends/evm/ControlFlowGraphBuilder.cpp

@@ -47,22 +47,14 @@ using namespace solidity;
 using namespace solidity::yul;
 using namespace std;
 
-std::unique_ptr<CFG> ControlFlowGraphBuilder::build(
-	AsmAnalysisInfo const& _analysisInfo,
-	Dialect const& _dialect,
-	Block const& _block
-)
+namespace
+{
+// Removes edges to blocks that are not reachable.
+void cleanUnreachable(CFG& _cfg)
 {
-	auto result = std::make_unique<CFG>();
-	result->entry = &result->makeBlock();
-
-	ControlFlowGraphBuilder builder(*result, _analysisInfo, _dialect);
-	builder.m_currentBlock = result->entry;
-	builder(_block);
-
 	// Determine which blocks are reachable from the entry.
-	util::BreadthFirstSearch<CFG::BasicBlock*> reachabilityCheck{{result->entry}};
-	for (auto const& functionInfo: result->functionInfo | ranges::views::values)
+	util::BreadthFirstSearch<CFG::BasicBlock*> reachabilityCheck{{_cfg.entry}};
+	for (auto const& functionInfo: _cfg.functionInfo | ranges::views::values)
 		reachabilityCheck.verticesToTraverse.emplace_back(functionInfo.entry);
 
 	reachabilityCheck.run([&](CFG::BasicBlock* _node, auto&& _addChild) {
@@ -85,6 +77,71 @@ std::unique_ptr<CFG> ControlFlowGraphBuilder::build(
 		cxx20::erase_if(node->entries, [&](CFG::BasicBlock* entry) -> bool {
 			return !reachabilityCheck.visited.count(entry);
 		});
+}
+// Sets the ``recursive`` member to ``true`` for all recursive function calls.
+void markRecursiveCalls(CFG& _cfg)
+{
+	map<CFG::BasicBlock*, vector<CFG::FunctionCall*>> callsPerBlock;
+	auto const& findCalls = [&](CFG::BasicBlock* _block)
+	{
+		if (auto* calls = util::valueOrNullptr(callsPerBlock, _block))
+			return *calls;
+		vector<CFG::FunctionCall*>& calls = callsPerBlock[_block];
+		util::BreadthFirstSearch<CFG::BasicBlock*>{{_block}}.run([&](CFG::BasicBlock* _block, auto _addChild) {
+			for (auto& operation: _block->operations)
+				if (auto* functionCall = get_if<CFG::FunctionCall>(&operation.operation))
+					calls.emplace_back(functionCall);
+			std::visit(util::GenericVisitor{
+				[&](CFG::BasicBlock::MainExit const&) {},
+				[&](CFG::BasicBlock::Jump const& _jump)
+				{
+					_addChild(_jump.target);
+				},
+				[&](CFG::BasicBlock::ConditionalJump const& _conditionalJump)
+				{
+					_addChild(_conditionalJump.zero);
+					_addChild(_conditionalJump.nonZero);
+				},
+				[&](CFG::BasicBlock::FunctionReturn const&) {},
+				[&](CFG::BasicBlock::Terminated const&)	{},
+			}, _block->exit);
+		});
+		return calls;
+	};
+	for (auto& functionInfo: _cfg.functionInfo | ranges::views::values)
+		for (CFG::FunctionCall* call: findCalls(functionInfo.entry))
+		{
+			util::BreadthFirstSearch<CFG::FunctionCall*> breadthFirstSearch{{call}};
+			breadthFirstSearch.run([&](CFG::FunctionCall* _call, auto _addChild) {
+				auto& calledFunctionInfo = _cfg.functionInfo.at(&_call->function.get());
+				if (&calledFunctionInfo == &functionInfo)
+				{
+					call->recursive = true;
+					breadthFirstSearch.abort();
+					return;
+				}
+				for (CFG::FunctionCall* nestedCall: findCalls(_cfg.functionInfo.at(&_call->function.get()).entry))
+					_addChild(nestedCall);
+			});
+		}
+}
+}
+
+std::unique_ptr<CFG> ControlFlowGraphBuilder::build(
+	AsmAnalysisInfo const& _analysisInfo,
+	Dialect const& _dialect,
+	Block const& _block
+)
+{
+	auto result = std::make_unique<CFG>();
+	result->entry = &result->makeBlock();
+
+	ControlFlowGraphBuilder builder(*result, _analysisInfo, _dialect);
+	builder.m_currentBlock = result->entry;
+	builder(_block);
+
+	cleanUnreachable(*result);
+	markRecursiveCalls(*result);
 
 	// TODO: It might be worthwhile to run some further simplifications on the graph itself here.
 	// E.g. if there is a jump to a node that has the jumping node as its only entry, the nodes can be fused, etc.