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diff --git a/libyul/optimiser/UnusedPruner.h b/libyul/optimiser/UnusedPruner.h
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+/*
+	This file is part of solidity.
+
+	solidity is free software: you can redistribute it and/or modify
+	it under the terms of the GNU General Public License as published by
+	the Free Software Foundation, either version 3 of the License, or
+	(at your option) any later version.
+
+	solidity is distributed in the hope that it will be useful,
+	but WITHOUT ANY WARRANTY; without even the implied warranty of
+	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+	GNU General Public License for more details.
+
+	You should have received a copy of the GNU General Public License
+	along with solidity.  If not, see <http://www.gnu.org/licenses/>.
+*/
+/**
+ * Optimisation stage that removes unused variables and functions.
+ */
+
+#pragma once
+
+#include <libyul/optimiser/ASTWalker.h>
+
+#include <string>
+#include <map>
+#include <set>
+
+namespace dev
+{
+namespace julia
+{
+
+/**
+ * Optimisation stage that removes unused variables and functions.
+ *
+ * TODO: Also remove intermediate variable assignments from movable expressions
+ * which are not referenced until after the next assignment to the same variable.
+ *
+ * Note that this does not remove circular references.
+ *
+ * Prerequisite: Disambiguator
+ */
+class UnusedPruner: public ASTModifier
+{
+public:
+	explicit UnusedPruner(Block& _ast);
+
+	using ASTModifier::operator();
+	virtual void operator()(Block& _block) override;
+
+	// @returns true iff the code changed in the previous run.
+	bool shouldRunAgain() const { return m_shouldRunAgain; }
+
+	// Run the pruner until the code does not change anymore.
+	static void runUntilStabilised(Block& _ast);
+
+private:
+	bool used(std::string const& _name) const;
+	void subtractReferences(std::map<std::string, size_t> const& _subtrahend);
+
+	bool m_shouldRunAgain = false;
+	std::map<std::string, size_t> m_references;
+};
+
+}
+}