[Yul] leave statement.

libyul/optimiser/Semantics.h

@@ -113,6 +113,31 @@ private:
 	bool m_msizeFound = false;
 };
 
+/**
+ * Class that can be used to find out if the given function contains the ``leave`` statement.
+ *
+ * Returns true even in the case where the function definition contains another function definition
+ * that contains the leave statement.
+ */
+class LeaveFinder: public ASTWalker
+{
+public:
+	static bool containsLeave(FunctionDefinition const& _fun)
+	{
+		LeaveFinder f;
+		f(_fun);
+		return f.m_leaveFound;
+	}
+
+	using ASTWalker::operator();
+	void operator()(Leave const&) { m_leaveFound = true; }
+
+private:
+	LeaveFinder() = default;
+
+	bool m_leaveFound = false;
+};
+
 /**
  * Specific AST walker that determines whether an expression is movable
  * and collects the referenced variables.
@@ -148,12 +173,13 @@ private:
 class TerminationFinder
 {
 public:
-	enum class ControlFlow { FlowOut, Break, Continue, Terminate };
+	// TODO check all uses of TerminationFinder!
+	enum class ControlFlow { FlowOut, Break, Continue, Terminate, Leave };
 
 	TerminationFinder(Dialect const& _dialect): m_dialect(_dialect) {}
 
 	/// @returns the index of the first statement in the provided sequence
-	/// that is an unconditional ``break``, ``continue`` or a
+	/// that is an unconditional ``break``, ``continue``, ``leave`` or a
 	/// call to a terminating builtin function.
 	/// If control flow can continue at the end of the list,
 	/// returns `FlowOut` and ``size_t(-1)``.