Control flow side effects on non-disambiguated source.

Author: chriseth

libyul/ControlFlowSideEffectsCollector.cpp

@@ -20,6 +20,7 @@
 
 #include <libyul/AST.h>
 #include <libyul/Dialect.h>
+#include <libyul/FunctionReferenceResolver.h>
 
 #include <libsolutil/Common.h>
 #include <libsolutil/CommonData.h>
@@ -35,16 +36,15 @@ using namespace solidity::yul;
 
 ControlFlowBuilder::ControlFlowBuilder(Block const& _ast)
 {
-	for (auto const& statement: _ast.statements)
-		if (auto const* function = get_if<FunctionDefinition>(&statement))
-			(*this)(*function);
+	m_currentNode = newNode();
+	(*this)(_ast);
 }
 
 void ControlFlowBuilder::operator()(FunctionCall const& _functionCall)
 {
 	walkVector(_functionCall.arguments | ranges::views::reverse);
 	newConnectedNode();
-	m_currentNode->functionCall = _functionCall.functionName.name;
+	m_currentNode->functionCall = &_functionCall;
 }
 
 void ControlFlowBuilder::operator()(If const& _if)
@@ -78,7 +78,9 @@ void ControlFlowBuilder::operator()(Switch const& _switch)
 void ControlFlowBuilder::operator()(FunctionDefinition const& _function)
 {
 	ScopedSaveAndRestore currentNode(m_currentNode, nullptr);
-	yulAssert(!m_leave && !m_break && !m_continue, "Function hoister has not been used.");
+	ScopedSaveAndRestore leave(m_leave, nullptr);
+	ScopedSaveAndRestore _break(m_break, nullptr);
+	ScopedSaveAndRestore _continue(m_continue, nullptr);
 
 	FunctionFlow flow;
 	flow.exit = newNode();
@@ -90,7 +92,7 @@ void ControlFlowBuilder::operator()(FunctionDefinition const& _function)
 
 	m_currentNode->successors.emplace_back(flow.exit);
 
-	m_functionFlows[_function.name] = move(flow);
+	m_functionFlows[&_function] = move(flow);
 
 	m_leave = nullptr;
 }
@@ -164,14 +166,17 @@ ControlFlowSideEffectsCollector::ControlFlowSideEffectsCollector(
 	Block const& _ast
 ):
 	m_dialect(_dialect),
-	m_cfgBuilder(_ast)
+	m_cfgBuilder(_ast),
+	m_functionReferences(FunctionReferenceResolver{_ast}.references())
 {
-	for (auto&& [name, flow]: m_cfgBuilder.functionFlows())
+	for (auto&& [function, flow]: m_cfgBuilder.functionFlows())
 	{
 		yulAssert(!flow.entry->functionCall);
-		m_processedNodes[name] = {};
-		m_pendingNodes[name].push_front(flow.entry);
-		m_functionSideEffects[name] = {false, false, false};
+		yulAssert(function);
+		m_processedNodes[function] = {};
+		m_pendingNodes[function].push_front(flow.entry);
+		m_functionSideEffects[function] = {false, false, false};
+		m_functionCalls[function] = {};
 	}
 
 	// Process functions while we have progress. For now, we are only interested
@@ -180,8 +185,8 @@ ControlFlowSideEffectsCollector::ControlFlowSideEffectsCollector(
 	while (progress)
 	{
 		progress = false;
-		for (auto const& functionName: m_pendingNodes | ranges::views::keys)
-			if (processFunction(functionName))
+		for (FunctionDefinition const* function: m_pendingNodes | ranges::views::keys)
+			if (processFunction(*function))
 				progress = true;
 	}
 
@@ -190,57 +195,64 @@ ControlFlowSideEffectsCollector::ControlFlowSideEffectsCollector(
 	// If we have not set `canContinue` by now, the function's exit
 	// is not reachable.
 
-	for (auto&& [functionName, calls]: m_functionCalls)
+	// Now it is sufficient to handle the reachable function calls (`m_functionCalls`),
+	// we do not have to consider the control-flow graph anymore.
+	for (auto&& [function, calls]: m_functionCalls)
 	{
-		ControlFlowSideEffects& sideEffects = m_functionSideEffects[functionName];
-		auto _visit = [&, visited = std::set<YulString>{}](YulString _function, auto&& _recurse) mutable {
-			if (sideEffects.canTerminate && sideEffects.canRevert)
+		yulAssert(function);
+		ControlFlowSideEffects& functionSideEffects = m_functionSideEffects[function];
+		auto _visit = [&, visited = std::set<FunctionDefinition const*>{}](FunctionDefinition const& _function, auto&& _recurse) mutable {
+			// Worst side-effects already, stop searching.
+			if (functionSideEffects.canTerminate && functionSideEffects.canRevert)
 				return;
-			if (!visited.insert(_function).second)
+			if (!visited.insert(&_function).second)
 				return;
 
-			ControlFlowSideEffects const* calledSideEffects = nullptr;
-			if (BuiltinFunction const* f = _dialect.builtin(_function))
-				calledSideEffects = &f->controlFlowSideEffects;
-			else
-				calledSideEffects = &m_functionSideEffects.at(_function);
-
-			if (calledSideEffects->canTerminate)
-				sideEffects.canTerminate = true;
-			if (calledSideEffects->canRevert)
-				sideEffects.canRevert = true;
-
-			set<YulString> emptySet;
-			for (YulString callee: util::valueOrDefault(m_functionCalls, _function, emptySet))
-				_recurse(callee, _recurse);
+			for (FunctionCall const* call: m_functionCalls.at(&_function))
+			{
+				ControlFlowSideEffects const& calledSideEffects = sideEffects(*call);
+				if (calledSideEffects.canTerminate)
+					functionSideEffects.canTerminate = true;
+				if (calledSideEffects.canRevert)
+					functionSideEffects.canRevert = true;
+
+				if (m_functionReferences.count(call))
+					_recurse(*m_functionReferences.at(call), _recurse);
+			}
 		};
-		for (auto const& call: calls)
-			_visit(call, _visit);
+		_visit(*function, _visit);
 	}
+}
 
+map<YulString, ControlFlowSideEffects> ControlFlowSideEffectsCollector::functionSideEffectsNamed() const
+{
+	map<YulString, ControlFlowSideEffects> result;
+	for (auto&& [function, sideEffects]: m_functionSideEffects)
+		yulAssert(result.insert({function->name, sideEffects}).second);
+	return result;
 }
 
-bool ControlFlowSideEffectsCollector::processFunction(YulString _name)
+bool ControlFlowSideEffectsCollector::processFunction(FunctionDefinition const& _function)
 {
 	bool progress = false;
-	while (ControlFlowNode const* node = nextProcessableNode(_name))
+	while (ControlFlowNode const* node = nextProcessableNode(_function))
 	{
-		if (node == m_cfgBuilder.functionFlows().at(_name).exit)
+		if (node == m_cfgBuilder.functionFlows().at(&_function).exit)
 		{
-			m_functionSideEffects[_name].canContinue = true;
+			m_functionSideEffects[&_function].canContinue = true;
 			return true;
 		}
 		for (ControlFlowNode const* s: node->successors)
-			recordReachabilityAndQueue(_name, s);
+			recordReachabilityAndQueue(_function, s);
 
 		progress = true;
 	}
 	return progress;
 }
 
-ControlFlowNode const* ControlFlowSideEffectsCollector::nextProcessableNode(YulString _functionName)
+ControlFlowNode const* ControlFlowSideEffectsCollector::nextProcessableNode(FunctionDefinition const& _function)
 {
-	std::list<ControlFlowNode const*>& nodes = m_pendingNodes[_functionName];
+	std::list<ControlFlowNode const*>& nodes = m_pendingNodes[&_function];
 	auto it = ranges::find_if(nodes, [this](ControlFlowNode const* _node) {
 		return !_node->functionCall || sideEffects(*_node->functionCall).canContinue;
 	});
@@ -252,22 +264,22 @@ ControlFlowNode const* ControlFlowSideEffectsCollector::nextProcessableNode(YulS
 	return node;
 }
 
-ControlFlowSideEffects const& ControlFlowSideEffectsCollector::sideEffects(YulString _functionName) const
+ControlFlowSideEffects const& ControlFlowSideEffectsCollector::sideEffects(FunctionCall const& _call) const
 {
-	if (auto const* builtin = m_dialect.builtin(_functionName))
+	if (auto const* builtin = m_dialect.builtin(_call.functionName.name))
 		return builtin->controlFlowSideEffects;
 	else
-		return m_functionSideEffects.at(_functionName);
+		return m_functionSideEffects.at(m_functionReferences.at(&_call));
 }
 
 void ControlFlowSideEffectsCollector::recordReachabilityAndQueue(
-	YulString _functionName,
+	FunctionDefinition const& _function,
 	ControlFlowNode const* _node
 )
 {
 	if (_node->functionCall)
-		m_functionCalls[_functionName].insert(*_node->functionCall);
-	if (m_processedNodes[_functionName].insert(_node).second)
-		m_pendingNodes.at(_functionName).push_front(_node);
+		m_functionCalls[&_function].insert(_node->functionCall);
+	if (m_processedNodes[&_function].insert(_node).second)
+		m_pendingNodes.at(&_function).push_front(_node);
 }
 

libyul/ControlFlowSideEffectsCollector.h

@@ -34,8 +34,8 @@ struct Dialect;
 struct ControlFlowNode
 {
 	std::vector<ControlFlowNode const*> successors;
-	/// Name of the called function if the node calls a function.
-	std::optional<YulString> functionCall;
+	/// Function call AST node, if present.
+	FunctionCall const* functionCall = nullptr;
 };
 
 /**
@@ -56,7 +56,7 @@ class ControlFlowBuilder: private ASTWalker
 	/// Computes the control-flows of all function defined in the block.
 	/// Assumes the functions are hoisted to the topmost block.
 	explicit ControlFlowBuilder(Block const& _ast);
-	std::map<YulString, FunctionFlow> const& functionFlows() const { return m_functionFlows; }
+	std::map<FunctionDefinition const*, FunctionFlow> const& functionFlows() const { return m_functionFlows; }
 
 private:
 	using ASTWalker::operator();
@@ -79,12 +79,14 @@ class ControlFlowBuilder: private ASTWalker
 	ControlFlowNode const* m_break = nullptr;
 	ControlFlowNode const* m_continue = nullptr;
 
-	std::map<YulString, FunctionFlow> m_functionFlows;
+	std::map<FunctionDefinition const*, FunctionFlow> m_functionFlows;
 };
 
 
 /**
- * Requires: Disambiguator, Function Hoister.
+ * Computes control-flow side-effects for user-defined functions.
+ * Source does not have to be disambiguated, unless you want the side-effects
+ * based on function names.
  */
 class ControlFlowSideEffectsCollector
 {
@@ -94,36 +96,43 @@ class ControlFlowSideEffectsCollector
 		Block const& _ast
 	);
 
-	std::map<YulString, ControlFlowSideEffects> const& functionSideEffects() const
+	std::map<FunctionDefinition const*, ControlFlowSideEffects> const& functionSideEffects() const
 	{
 		return m_functionSideEffects;
 	}
+	/// Returns the side effects by function name, requires unique function names.
+	std::map<YulString, ControlFlowSideEffects> functionSideEffectsNamed() const;
 private:
 
 	/// @returns false if nothing could be processed.
-	bool processFunction(YulString _name);
+	bool processFunction(FunctionDefinition const& _function);
 
 	/// @returns the next pending node of the function that is not
 	/// a function call to a function that might not continue.
 	/// De-queues the node or returns nullptr if no such node is found.
-	ControlFlowNode const* nextProcessableNode(YulString _functionName);
+	ControlFlowNode const* nextProcessableNode(FunctionDefinition const& _function);
 
 	/// @returns the side-effects of either a builtin call or a user defined function
 	/// call (as far as already computed).
-	ControlFlowSideEffects const& sideEffects(YulString _functionName) const;
+	ControlFlowSideEffects const& sideEffects(FunctionCall const& _call) const;
 
 	/// Queues the given node to be processed (if not already visited)
 	/// and if it is a function call, records that `_functionName` calls
 	/// `*_node->functionCall`.
-	void recordReachabilityAndQueue(YulString _functionName, ControlFlowNode const* _node);
+	void recordReachabilityAndQueue(FunctionDefinition const& _function, ControlFlowNode const* _node);
 
 	Dialect const& m_dialect;
 	ControlFlowBuilder m_cfgBuilder;
-	std::map<YulString, ControlFlowSideEffects> m_functionSideEffects;
-	std::map<YulString, std::list<ControlFlowNode const*>> m_pendingNodes;
-	std::map<YulString, std::set<ControlFlowNode const*>> m_processedNodes;
-	/// `x` is in `m_functionCalls[y]` if a direct call to `x` is reachable inside `y`
-	std::map<YulString, std::set<YulString>> m_functionCalls;
+	/// Function references, but only for calls to user-defined functions.
+	std::map<FunctionCall const*, FunctionDefinition const*> m_functionReferences;
+	/// Side effects of user-defined functions, is being constructod.
+	std::map<FunctionDefinition const*, ControlFlowSideEffects> m_functionSideEffects;
+	/// Control flow nodes still to process, per function.
+	std::map<FunctionDefinition const*, std::list<ControlFlowNode const*>> m_pendingNodes;
+	/// Control flow nodes already processed, per function.
+	std::map<FunctionDefinition const*, std::set<ControlFlowNode const*>> m_processedNodes;
+	/// Set of reachable function calls nodes in each function (including calls to builtins).
+	std::map<FunctionDefinition const*, std::set<FunctionCall const*>> m_functionCalls;
 };
 
 

libyul/optimiser/ConditionalSimplifier.cpp

@@ -29,8 +29,10 @@ using namespace solidity::util;
 
 void ConditionalSimplifier::run(OptimiserStepContext& _context, Block& _ast)
 {
-	ControlFlowSideEffectsCollector sideEffects(_context.dialect, _ast);
-	ConditionalSimplifier{_context.dialect, sideEffects.functionSideEffects()}(_ast);
+	ConditionalSimplifier{
+		_context.dialect,
+		ControlFlowSideEffectsCollector{_context.dialect, _ast}.functionSideEffectsNamed()
+	}(_ast);
 }
 
 void ConditionalSimplifier::operator()(Switch& _switch)

libyul/optimiser/ConditionalSimplifier.h

@@ -62,12 +62,12 @@ class ConditionalSimplifier: public ASTModifier
 private:
 	explicit ConditionalSimplifier(
 		Dialect const& _dialect,
-		std::map<YulString, ControlFlowSideEffects> const& _sideEffects
+		std::map<YulString, ControlFlowSideEffects> _sideEffects
 	):
-		m_dialect(_dialect), m_functionSideEffects(_sideEffects)
+		m_dialect(_dialect), m_functionSideEffects(move(_sideEffects))
 	{}
 	Dialect const& m_dialect;
-	std::map<YulString, ControlFlowSideEffects> const& m_functionSideEffects;
+	std::map<YulString, ControlFlowSideEffects> m_functionSideEffects;
 };
 
 }

libyul/optimiser/ConditionalUnsimplifier.cpp

@@ -30,8 +30,10 @@ using namespace solidity::util;
 
 void ConditionalUnsimplifier::run(OptimiserStepContext& _context, Block& _ast)
 {
-	ControlFlowSideEffectsCollector sideEffects(_context.dialect, _ast);
-	ConditionalUnsimplifier{_context.dialect, sideEffects.functionSideEffects()}(_ast);
+	ConditionalUnsimplifier{
+		_context.dialect,
+		ControlFlowSideEffectsCollector{_context.dialect, _ast}.functionSideEffectsNamed()
+	}(_ast);
 }
 
 void ConditionalUnsimplifier::operator()(Switch& _switch)

libyul/optimiser/DeadCodeEliminator.cpp

@@ -40,7 +40,7 @@ void DeadCodeEliminator::run(OptimiserStepContext& _context, Block& _ast)
 	ControlFlowSideEffectsCollector sideEffects(_context.dialect, _ast);
 	DeadCodeEliminator{
 		_context.dialect,
-		sideEffects.functionSideEffects()
+		sideEffects.functionSideEffectsNamed()
 	}(_ast);
 }
 

libyul/optimiser/DeadCodeEliminator.h

@@ -23,6 +23,7 @@
 
 #include <libyul/optimiser/ASTWalker.h>
 #include <libyul/YulString.h>
+#include <libyul/ControlFlowSideEffects.h>
 
 #include <map>
 #include <set>
@@ -31,7 +32,6 @@ namespace solidity::yul
 {
 struct Dialect;
 struct OptimiserStepContext;
-struct ControlFlowSideEffects;
 
 /**
  * Optimisation stage that removes unreachable code
@@ -62,11 +62,11 @@ class DeadCodeEliminator: public ASTModifier
 private:
 	DeadCodeEliminator(
 		Dialect const& _dialect,
-		std::map<YulString, ControlFlowSideEffects> const& _sideEffects
-	): m_dialect(_dialect), m_functionSideEffects(_sideEffects) {}
+		std::map<YulString, ControlFlowSideEffects> _sideEffects
+	): m_dialect(_dialect), m_functionSideEffects(move(_sideEffects)) {}
 
 	Dialect const& m_dialect;
-	std::map<YulString, ControlFlowSideEffects> const& m_functionSideEffects;
+	std::map<YulString, ControlFlowSideEffects> m_functionSideEffects;
 };
 
 }