Avoid declare variable when stack size is zero

Author: r0qs

Diff for: libsolidity/experimental/codegen/IRGeneratorForStatements.cpp

@@ -205,8 +205,10 @@ void IRGeneratorForStatements::endVisit(BinaryOperation const& _binaryOperation)
 	// TODO: get around resolveRecursive by passing the environment further down?
 	functionType = m_context.env->resolveRecursive(functionType);
 	m_context.enqueueFunctionDefinition(&functionDefinition, functionType);
-	m_code << "let " << var(_binaryOperation).commaSeparatedList() <<
-		" := " << IRNames::function(*m_context.env, functionDefinition, functionType) << "(" <<
+	std::string functionDeclaration = var(_binaryOperation).commaSeparatedList();
+	if (!functionDeclaration.empty())
+		m_code << "let " << functionDeclaration << " := ";
+	m_code << IRNames::function(*m_context.env, functionDefinition, functionType) << "(" <<
 		var(_binaryOperation.leftExpression()).commaSeparatedList() <<
 		var(_binaryOperation.rightExpression()).commaSeparatedListPrefixed() << ")\n";
 }
@@ -344,15 +346,19 @@ void IRGeneratorForStatements::endVisit(FunctionCall const& _functionCall)
 	m_context.enqueueFunctionDefinition(functionDefinition, functionType);
 	// TODO: account for return stack size
 	solAssert(!functionDefinition->returnParameterList());
-	if (functionDefinition->experimentalReturnExpression())
+	std::string functionDeclaration = var(_functionCall).commaSeparatedList();
+	if (!functionDeclaration.empty())
 		m_code << "let " << var(_functionCall).commaSeparatedList() << " := ";
 	m_code << IRNames::function(*m_context.env, *functionDefinition, functionType) << "(";
 	auto const& arguments = _functionCall.arguments();
-	if (arguments.size() > 1)
+	if (arguments.size() == 1)
+		m_code << var(*arguments.back()).commaSeparatedList();
+	else if (arguments.size() > 1)
+	{
 		for (auto arg: arguments | ranges::views::drop_last(1))
 			m_code << var(*arg).commaSeparatedList();
-	if (!arguments.empty())
 		m_code << var(*arguments.back()).commaSeparatedListPrefixed();
+	}
 	m_code << ")\n";
 }
 

Diff for: libsolidity/experimental/codegen/IRVariable.cpp

@@ -46,13 +46,13 @@ IRVariable::IRVariable(Expression const& _expression, Type _type, size_t _stackS
 std::vector<std::string> IRVariable::stackSlots() const
 {
 	std::vector<std::string> result;
-	if (m_stackSize > 1)
-	{
+	if (m_stackSize == 0)
+		return {};
+	if (m_stackSize == 1)
+		result.emplace_back(m_baseName);
+	else
 		for (size_t i = 0; i < m_stackSize; ++i)
 			result.emplace_back(suffixedName(std::to_string(i)));
-		return result;
-	}
-	result.emplace_back(m_baseName);
 	return result;
 }