Allow stack limit evasion in system yul routines during old code generation.

libevmasm/AssemblyItem.h

@@ -63,6 +63,9 @@ public:
 
 	AssemblyItem(u256 _push, langutil::SourceLocation _location = langutil::SourceLocation()):
 		AssemblyItem(Push, std::move(_push), std::move(_location)) { }
+	/// Used only for the free memory pointer as "memoryguard". Should probably be replaced by a separate AssemblyItemType.
+	AssemblyItem(std::shared_ptr<u256> _pushData, langutil::SourceLocation _location = langutil::SourceLocation()):
+		m_type(Push), m_data(std::move(_pushData)), m_location(std::move(_location)) { }
 	AssemblyItem(Instruction _i, langutil::SourceLocation _location = langutil::SourceLocation()):
 		m_type(Operation),
 		m_instruction(_i),

libsolidity/codegen/CompilerContext.cpp

@@ -484,7 +484,7 @@ void CompilerContext::appendInlineAssembly(
 		obj.code = parserResult;
 		obj.analysisInfo = make_shared<yul::AsmAnalysisInfo>(analysisInfo);
 
-		optimizeYul(obj, dialect, _optimiserSettings, externallyUsedIdentifiers);
+		optimizeYul(obj, dialect, _optimiserSettings, externallyUsedIdentifiers, _system);
 
 		if (_system)
 		{
@@ -531,7 +531,13 @@ void CompilerContext::appendInlineAssembly(
 }
 
 
-void CompilerContext::optimizeYul(yul::Object& _object, yul::EVMDialect const& _dialect, OptimiserSettings const& _optimiserSettings, std::set<yul::YulString> const& _externalIdentifiers)
+void CompilerContext::optimizeYul(
+	yul::Object& _object,
+	yul::EVMDialect const& _dialect,
+	OptimiserSettings const& _optimiserSettings,
+	std::set<yul::YulString> const& _externalIdentifiers,
+	bool _system
+)
 {
 #ifdef SOL_OUTPUT_ASM
 	cout << yul::AsmPrinter(*dialect)(*_object.code) << endl;
@@ -539,6 +545,7 @@ void CompilerContext::optimizeYul(yul::Object& _object, yul::EVMDialect const& _
 
 	bool const isCreation = runtimeContext() != nullptr;
 	yul::GasMeter meter(_dialect, isCreation, _optimiserSettings.expectedExecutionsPerDeployment);
+	solAssert(m_freeMemoryInitPush, "");
 	yul::OptimiserSuite::run(
 		_dialect,
 		&meter,
@@ -546,7 +553,8 @@ void CompilerContext::optimizeYul(yul::Object& _object, yul::EVMDialect const& _
 		_optimiserSettings.optimizeStackAllocation,
 		_optimiserSettings.yulOptimiserSteps,
 		isCreation? nullopt : make_optional(_optimiserSettings.expectedExecutionsPerDeployment),
-		_externalIdentifiers
+		_externalIdentifiers,
+		_system ? m_freeMemoryInitPush : shared_ptr<u256>{}
 	);
 
 #ifdef SOL_OUTPUT_ASM

libsolidity/codegen/CompilerContext.h

@@ -276,7 +276,13 @@ public:
 	/// Otherwise returns "revert(0, 0)".
 	std::string revertReasonIfDebug(std::string const& _message = "");
 
-	void optimizeYul(yul::Object& _object, yul::EVMDialect const& _dialect, OptimiserSettings const& _optimiserSetting, std::set<yul::YulString> const& _externalIdentifiers = {});
+	void optimizeYul(
+		yul::Object& _object,
+		yul::EVMDialect const& _dialect,
+		OptimiserSettings const& _optimiserSetting,
+		std::set<yul::YulString> const& _externalIdentifiers = {},
+		bool _system = false
+	);
 
 	/// Appends arbitrary data to the end of the bytecode.
 	void appendToAuxiliaryData(bytes const& _data) { m_asm->appendToAuxiliaryData(_data); }
@@ -309,6 +315,12 @@ public:
 
 	RevertStrings revertStrings() const { return m_revertStrings; }
 
+	evmasm::AssemblyItem makeFreeMemoryInitPush(u256 _value)
+	{
+		m_freeMemoryInitPush = std::make_shared<u256>(_value);
+		return evmasm::AssemblyItem(m_freeMemoryInitPush);
+	}
+
 private:
 	/// Updates source location set in the assembly.
 	void updateSourceLocation();
@@ -394,6 +406,8 @@ private:
 	std::queue<std::tuple<std::string, unsigned, unsigned, std::function<void(CompilerContext&)>>> m_lowLevelFunctionGenerationQueue;
 	/// Flag to check that appendYulUtilityFunctions() was called exactly once
 	bool m_appendYulUtilityFunctionsRan = false;
+	/// The assembly item that pushes the initial value of the free memory pointer.
+	std::shared_ptr<u256> m_freeMemoryInitPush;
 };
 
 }

libsolidity/codegen/CompilerUtils.cpp

@@ -55,7 +55,7 @@ void CompilerUtils::initialiseFreeMemoryPointer()
 {
 	size_t reservedMemory = m_context.reservedMemory();
 	solAssert(bigint(generalPurposeMemoryStart) + bigint(reservedMemory) < bigint(1) << 63, "");
-	m_context << (u256(generalPurposeMemoryStart) + reservedMemory);
+	m_context << m_context.makeFreeMemoryInitPush((u256(generalPurposeMemoryStart) + reservedMemory));
 	storeFreeMemoryPointer();
 }
 

libyul/optimiser/OptimiserStep.h

@@ -20,6 +20,8 @@
 
 #include <libyul/Exceptions.h>
 
+#include <libsolutil/Common.h>
+
 #include <optional>
 #include <string>
 #include <set>
@@ -39,6 +41,7 @@ struct OptimiserStepContext
 	std::set<YulString> const& reservedIdentifiers;
 	/// The value nullopt represents creation code
 	std::optional<size_t> expectedExecutionsPerDeployment;
+	std::shared_ptr<u256> externalFreeMemoryPointerInitializer{};
 };
 
 

libyul/optimiser/StackLimitEvader.cpp

@@ -124,10 +124,7 @@ void StackLimitEvader::run(
 )
 {
 	auto const* evmDialect = dynamic_cast<EVMDialect const*>(&_context.dialect);
-	yulAssert(
-		evmDialect && evmDialect->providesObjectAccess(),
-		"StackLimitEvader can only be run on objects using the EVMDialect with object access."
-	);
+	yulAssert(evmDialect, "StackLimitEvader can only be run on objects using the EVMDialect.");
 	if (evmDialect && evmDialect->evmVersion() > langutil::EVMVersion::homestead())
 	{
 		yul::AsmAnalysisInfo analysisInfo = yul::AsmAnalyzer::analyzeStrictAssertCorrect(*evmDialect, _object);
@@ -165,11 +162,14 @@ void StackLimitEvader::run(
 {
 	yulAssert(_object.code, "");
 	auto const* evmDialect = dynamic_cast<EVMDialect const*>(&_context.dialect);
-	yulAssert(
-		evmDialect && evmDialect->providesObjectAccess(),
-		"StackLimitEvader can only be run on objects using the EVMDialect with object access."
-	);
+	yulAssert(evmDialect, "StackLimitEvader can only be run on objects using the EVMDialect.");
 
+	u256 reservedMemory = 0;
+
+	if (_context.externalFreeMemoryPointerInitializer)
+		reservedMemory = *_context.externalFreeMemoryPointerInitializer;
+	else
+	{
 		vector<FunctionCall*> memoryGuardCalls = FunctionCallFinder::run(
 			*_object.code,
 			"memoryguard"_yulstring
@@ -179,12 +179,13 @@ void StackLimitEvader::run(
 			return;
 
 		// Make sure all calls to ``memoryguard`` we found have the same value as argument (otherwise, abort).
-	u256 reservedMemory = literalArgumentValue(*memoryGuardCalls.front());
+		reservedMemory = literalArgumentValue(*memoryGuardCalls.front());
 		yulAssert(reservedMemory < u256(1) << 32 - 1, "");
 
 		for (FunctionCall const* memoryGuardCall: memoryGuardCalls)
 			if (reservedMemory != literalArgumentValue(*memoryGuardCall))
 				return;
+	}
 
 	CallGraph callGraph = CallGraphGenerator::callGraph(*_object.code);
 
@@ -195,6 +196,11 @@ void StackLimitEvader::run(
 
 	map<YulString, FunctionDefinition const*> functionDefinitions = FunctionDefinitionCollector::run(*_object.code);
 
+	if (_context.externalFreeMemoryPointerInitializer)
+		// Simulate calls from outer block to all defined functions.
+		for (auto functionDef: functionDefinitions)
+			callGraph.functionCalls[YulString{}].insert(functionDef.first);
+
 	MemoryOffsetAllocator memoryOffsetAllocator{_unreachableVariables, callGraph.functionCalls, functionDefinitions};
 	uint64_t requiredSlots = memoryOffsetAllocator.run();
 	yulAssert(requiredSlots < (uint64_t(1) << 32) - 1, "");
@@ -202,6 +208,9 @@ void StackLimitEvader::run(
 	StackToMemoryMover::run(_context, reservedMemory, memoryOffsetAllocator.slotAllocations, requiredSlots, *_object.code);
 
 	reservedMemory += 32 * requiredSlots;
+	if (_context.externalFreeMemoryPointerInitializer)
+		*_context.externalFreeMemoryPointerInitializer = reservedMemory;
+	else
 		for (FunctionCall* memoryGuardCall: FunctionCallFinder::run(*_object.code, "memoryguard"_yulstring))
 		{
 			Literal* literal = std::get_if<Literal>(&memoryGuardCall->arguments.front());

libyul/optimiser/StackToMemoryMover.cpp

@@ -109,10 +109,7 @@ m_nameDispenser(_context.dispenser),
 m_functionReturnVariables(move(_functionReturnVariables))
 {
 	auto const* evmDialect = dynamic_cast<EVMDialect const*>(&_context.dialect);
-	yulAssert(
-		evmDialect && evmDialect->providesObjectAccess(),
-		"StackToMemoryMover can only be run on objects using the EVMDialect with object access."
-	);
+	yulAssert(evmDialect, "StackToMemoryMover can only be run on objects using the EVMDialect.");
 }
 
 void StackToMemoryMover::operator()(FunctionDefinition& _functionDefinition)

libyul/optimiser/Suite.cpp

@@ -89,7 +89,8 @@ void OptimiserSuite::run(
 	bool _optimizeStackAllocation,
 	string const& _optimisationSequence,
 	optional<size_t> _expectedExecutionsPerDeployment,
-	set<YulString> const& _externallyUsedIdentifiers
+	set<YulString> const& _externallyUsedIdentifiers,
+	std::shared_ptr<u256> _externalFreeMemoryPointerInitializer
 )
 {
 	EVMDialect const* evmDialect = dynamic_cast<EVMDialect const*>(&_dialect);
@@ -107,7 +108,14 @@ void OptimiserSuite::run(
 	)(*_object.code));
 	Block& ast = *_object.code;
 
-	OptimiserSuite suite(_dialect, reservedIdentifiers, Debug::None, ast, _expectedExecutionsPerDeployment);
+	OptimiserSuite suite(
+		_dialect,
+		reservedIdentifiers,
+		Debug::None,
+		ast,
+		_expectedExecutionsPerDeployment,
+		_externalFreeMemoryPointerInitializer
+	);
 
 	// Some steps depend on properties ensured by FunctionHoister, BlockFlattener, FunctionGrouper and
 	// ForLoopInitRewriter. Run them first to be able to run arbitrary sequences safely.
@@ -144,10 +152,9 @@ void OptimiserSuite::run(
 				_optimizeStackAllocation,
 				stackCompressorMaxIterations
 			);
-			if (evmDialect->providesObjectAccess())
 			StackLimitEvader::run(suite.m_context, _object);
 		}
-		else if (evmDialect->providesObjectAccess() && _optimizeStackAllocation)
+		else if (_optimizeStackAllocation)
 			StackLimitEvader::run(suite.m_context, _object);
 	}
 	else if (dynamic_cast<WasmDialect const*>(&_dialect))

libyul/optimiser/Suite.h

@@ -66,7 +66,8 @@ public:
 		bool _optimizeStackAllocation,
 		std::string const& _optimisationSequence,
 		std::optional<size_t> _expectedExecutionsPerDeployment,
-		std::set<YulString> const& _externallyUsedIdentifiers = {}
+		std::set<YulString> const& _externallyUsedIdentifiers = {},
+		std::shared_ptr<u256> _externalFreeMemoryPointerInitializer = {}
 	);
 
 	/// Ensures that specified sequence of step abbreviations is well-formed and can be executed.
@@ -91,10 +92,18 @@ private:
 		std::set<YulString> const& _externallyUsedIdentifiers,
 		Debug _debug,
 		Block& _ast,
-		std::optional<size_t> expectedExecutionsPerDeployment
+		std::optional<size_t> expectedExecutionsPerDeployment,
+		std::shared_ptr<u256> _externalFreeMemoryPointerInitializer = {}
+
 	):
 		m_dispenser{_dialect, _ast, _externallyUsedIdentifiers},
-		m_context{_dialect, m_dispenser, _externallyUsedIdentifiers, expectedExecutionsPerDeployment},
+		m_context{
+			_dialect,
+			m_dispenser,
+			_externallyUsedIdentifiers,
+			expectedExecutionsPerDeployment,
+			_externalFreeMemoryPointerInitializer
+		},
 		m_debug(_debug)
 	{}
 

test/libsolidity/semanticTests/various/negative_stack_height.sol

@@ -62,6 +62,6 @@ contract C {
 // via yul disabled because of stack issues.
 
 // ====
-// compileViaYul: false
+// compileViaYul: also
 // ----
 // constructor() ->