1 files changed, 13 insertions, 3 deletions
diff --git a/libyul/optimiser/SSAValueTracker.cpp b/libyul/optimiser/SSAValueTracker.cpp
index 35b29b04..23eb9ec2 100644
--- a/libyul/optimiser/SSAValueTracker.cpp
+++ b/libyul/optimiser/SSAValueTracker.cpp
@@ -33,13 +33,20 @@ void SSAValueTracker::operator()(Assignment const& _assignment)
 		m_values.erase(var.name);
 }
 
+void SSAValueTracker::operator()(FunctionDefinition const& _funDef)
+{
+	for (auto const& var: _funDef.returnVariables)
+		setValue(var.name, nullptr);
+	ASTWalker::operator()(_funDef);
+}
+
 void SSAValueTracker::operator()(VariableDeclaration const& _varDecl)
 {
-	if (_varDecl.variables.size() == 1)
-		setValue(_varDecl.variables.front().name, _varDecl.value.get());
-	else
+	if (!_varDecl.value)
 		for (auto const& var: _varDecl.variables)
 			setValue(var.name, nullptr);
+	else if (_varDecl.variables.size() == 1)
+		setValue(_varDecl.variables.front().name, _varDecl.value.get());
 }
 
 void SSAValueTracker::setValue(YulString _name, Expression const* _value)
@@ -49,5 +56,8 @@ void SSAValueTracker::setValue(YulString _name, Expression const* _value)
 		OptimizerException,
 		"Source needs to be disambiguated."
 	);
+	static Expression const zero{Literal{{}, LiteralKind::Number, YulString{"0"}, {}}};
+	if (!_value)
+		_value = &zero;
 	m_values[_name] = _value;
 }