4 files changed, 19 insertions, 8 deletions
diff --git a/libyul/optimiser/Disambiguator.cpp b/libyul/optimiser/Disambiguator.cpp
index af3507e1..dcba97c9 100644
--- a/libyul/optimiser/Disambiguator.cpp
+++ b/libyul/optimiser/Disambiguator.cpp
@@ -34,6 +34,9 @@ using Scope = dev::solidity::assembly::Scope;
 
 string Disambiguator::translateIdentifier(string const& _originalName)
 {
+	if ((m_externallyUsedIdentifiers.count(_originalName)))
+		return _originalName;
+
 	assertThrow(!m_scopes.empty() && m_scopes.back(), OptimizerException, "");
 	Scope::Identifier const* id = m_scopes.back()->lookup(_originalName);
 	assertThrow(id, OptimizerException, "");
diff --git a/libyul/optimiser/Disambiguator.h b/libyul/optimiser/Disambiguator.h
index 0829fd58..e16ebfbf 100644
--- a/libyul/optimiser/Disambiguator.h
+++ b/libyul/optimiser/Disambiguator.h
@@ -43,9 +43,14 @@ namespace yul
 class Disambiguator: public ASTCopier
 {
 public:
-	Disambiguator(solidity::assembly::AsmAnalysisInfo const& _analysisInfo):
-		m_info(_analysisInfo)
-	{}
+	explicit Disambiguator(
+		solidity::assembly::AsmAnalysisInfo const& _analysisInfo,
+		std::set<std::string> const& _externallyUsedIdentifiers = {}
+	):
+		m_info(_analysisInfo), m_externallyUsedIdentifiers(_externallyUsedIdentifiers)
+	{
+		m_nameDispenser.m_usedNames = m_externallyUsedIdentifiers;
+	}
 
 protected:
 	virtual void enterScope(Block const& _block) override;
@@ -58,6 +63,7 @@ protected:
 	void leaveScopeInternal(solidity::assembly::Scope& _scope);
 
 	solidity::assembly::AsmAnalysisInfo const& m_info;
+	std::set<std::string> const& m_externallyUsedIdentifiers;
 
 	std::vector<solidity::assembly::Scope*> m_scopes;
 	std::map<void const*, std::string> m_translations;
diff --git a/libyul/optimiser/UnusedPruner.cpp b/libyul/optimiser/UnusedPruner.cpp
index 74b6bee4..37a74553 100644
--- a/libyul/optimiser/UnusedPruner.cpp
+++ b/libyul/optimiser/UnusedPruner.cpp
@@ -33,12 +33,14 @@ using namespace std;
 using namespace dev;
 using namespace dev::yul;
 
-UnusedPruner::UnusedPruner(Block& _ast)
+UnusedPruner::UnusedPruner(Block& _ast, set<string> const& _externallyUsedFunctions)
 {
 	ReferencesCounter counter;
 	counter(_ast);
 
 	m_references = counter.references();
+	for (auto const& f: _externallyUsedFunctions)
+		++m_references[f];
 }
 
 void UnusedPruner::operator()(Block& _block)
@@ -89,11 +91,11 @@ void UnusedPruner::operator()(Block& _block)
 	ASTModifier::operator()(_block);
 }
 
-void UnusedPruner::runUntilStabilised(Block& _ast)
+void UnusedPruner::runUntilStabilised(Block& _ast, set<string> const& _externallyUsedFunctions)
 {
 	while (true)
 	{
-		UnusedPruner pruner(_ast);
+		UnusedPruner pruner(_ast, _externallyUsedFunctions);
 		pruner(_ast);
 		if (!pruner.shouldRunAgain())
 			return;
diff --git a/libyul/optimiser/UnusedPruner.h b/libyul/optimiser/UnusedPruner.h
index 327921ea..30617ff3 100644
--- a/libyul/optimiser/UnusedPruner.h
+++ b/libyul/optimiser/UnusedPruner.h
@@ -44,7 +44,7 @@ namespace yul
 class UnusedPruner: public ASTModifier
 {
 public:
-	explicit UnusedPruner(Block& _ast);
+	explicit UnusedPruner(Block& _ast, std::set<std::string> const& _externallyUsedFunctions = std::set<std::string>());
 
 	using ASTModifier::operator();
 	virtual void operator()(Block& _block) override;
@@ -53,7 +53,7 @@ public:
 	bool shouldRunAgain() const { return m_shouldRunAgain; }
 
 	// Run the pruner until the code does not change anymore.
-	static void runUntilStabilised(Block& _ast);
+	static void runUntilStabilised(Block& _ast, std::set<std::string> const& _externallyUsedFunctions = std::set<std::string>());
 
 private:
 	bool used(std::string const& _name) const;