Method operator()

libyul/optimiser/StackToMemoryMover.cpp:117–196

}

void StackToMemoryMover::operator()(FunctionDefinition& _functionDefinition)
{
	// It is important to first visit the function body, so that it doesn't replace the memory inits for
	// variable arguments we might generate below.
	ASTModifier::operator()(_functionDefinition);

	std::vector<Statement> memoryVariableInits;

	// All function parameters with a memory slot are moved at the beginning of the function body.
	for (NameWithDebugData const& param: _functionDefinition.parameters)
		if (auto slot = m_memoryOffsetTracker(param.name))
			memoryVariableInits += generateMemoryStore(
				m_context.dialect,
				param.debugData,
				*slot,
				Identifier{param.debugData, param.name}
			);

	// All memory return variables have to be initialized to zero in memory.
	for (NameWithDebugData const& returnVariable: _functionDefinition.returnVariables)
		if (auto slot = m_memoryOffsetTracker(returnVariable.name))
			memoryVariableInits += generateMemoryStore(
				m_context.dialect,
				returnVariable.debugData,
				*slot,
				Literal{returnVariable.debugData, LiteralKind::Number, LiteralValue(u256{0})}
			);

	// Special case of a function with a single return argument that needs to move to memory.
	if (_functionDefinition.returnVariables.size() == 1 && m_memoryOffsetTracker(_functionDefinition.returnVariables.front().name))
	{
		NameWithDebugDataList stackParameters = _functionDefinition.parameters | ranges::views::filter(
			std::not_fn(m_memoryOffsetTracker)
		) | ranges::to<NameWithDebugDataList>;
		// Generate new function without return variable and with only the non-moved parameters.
		YulName newFunctionName = m_context.dispenser.newName(_functionDefinition.name);
		m_newFunctionDefinitions.emplace_back(FunctionDefinition{
			_functionDefinition.debugData,
			newFunctionName,
			stackParameters,
			{},
			std::move(_functionDefinition.body)
		});
		// Generate new names for the arguments to maintain disambiguation.
		std::map<YulName, YulName> newArgumentNames;
		for (NameWithDebugData const& _var: stackParameters)
			newArgumentNames[_var.name] = m_context.dispenser.newName(_var.name);
		for (auto& parameter: _functionDefinition.parameters)
			parameter.name = util::valueOrDefault(newArgumentNames, parameter.name, parameter.name);
		// Replace original function by a call to the new function and an assignment to the return variable from memory.
		_functionDefinition.body = Block{_functionDefinition.debugData, std::move(memoryVariableInits)};
		_functionDefinition.body.statements.emplace_back(ExpressionStatement{
			_functionDefinition.debugData,
			FunctionCall{
				_functionDefinition.debugData,
				Identifier{_functionDefinition.debugData, newFunctionName},
				stackParameters | ranges::views::transform([&](NameWithDebugData const& _arg) {
					return Expression{Identifier{_arg.debugData, newArgumentNames.at(_arg.name)}};