[yul] Implements DataFlowAnalyzer for break & continue statements.

Author: christianparpart

libyul/optimiser/DataFlowAnalyzer.cpp

@@ -122,22 +122,19 @@ void DataFlowAnalyzer::operator()(ForLoop& _for)
 	assignments(_for.post);
 	clearValues(assignments.names());
 
+	AssignmentsSinceContinue assignmentsSinceCont;
+	assignmentsSinceCont(_for.body);
+
 	visit(*_for.condition);
 	(*this)(_for.body);
 	(*this)(_for.post);
 
-	clearValues(assignments.names());
-	popScope();
-}
-
-void DataFlowAnalyzer::operator()(Break&)
-{
-	yulAssert(false, "Not implemented yet.");
-}
+	if (!assignmentsSinceCont.empty())
+		clearValues(assignmentsSinceCont.names());
+	else
+		clearValues(assignments.names());
 
-void DataFlowAnalyzer::operator()(Continue&)
-{
-	yulAssert(false, "Not implemented yet.");
+	popScope();
 }
 
 void DataFlowAnalyzer::operator()(Block& _block)

libyul/optimiser/DataFlowAnalyzer.h

@@ -23,6 +23,7 @@
 #pragma once
 
 #include <libyul/optimiser/ASTWalker.h>
+#include <libyul/optimiser/NameCollector.h>
 #include <libyul/YulString.h>
 
 #include <map>
@@ -53,8 +54,6 @@ class DataFlowAnalyzer: public ASTModifier
 	void operator()(Switch& _switch) override;
 	void operator()(FunctionDefinition&) override;
 	void operator()(ForLoop&) override;
-	void operator()(Break& _continue) override;
-	void operator()(Continue& _continue) override;
 	void operator()(Block& _block) override;
 
 protected:

libyul/optimiser/NameCollector.cpp

@@ -79,3 +79,23 @@ void Assignments::operator()(Assignment const& _assignment)
 	for (auto const& var: _assignment.variableNames)
 		m_names.emplace(var.name);
 }
+
+void AssignmentsSinceContinue::operator()(ForLoop const& _forLoop)
+{
+	m_forLoopDepth++;
+	ASTWalker::operator()(_forLoop);
+	m_forLoopDepth--;
+}
+
+void AssignmentsSinceContinue::operator()(Continue const&)
+{
+	if (m_forLoopDepth == 0)
+		m_continueFound = true;
+}
+
+void AssignmentsSinceContinue::operator()(Assignment const& _assignment)
+{
+	if (m_continueFound)
+		for (auto const& var: _assignment.variableNames)
+			m_names.emplace(var.name);
+}

libyul/optimiser/NameCollector.h

@@ -81,4 +81,28 @@ class Assignments: public ASTWalker
 	std::set<YulString> m_names;
 };
 
+/**
+ * Collects all names from a given continue statement on onwards.
+ *
+ * It makes only sense to be invoked from within a body of an outer for loop, that is,
+ * it will only collect all names from the beginning of the first continue statement
+ * of the outer-most ForLoop.
+ */
+class AssignmentsSinceContinue: public ASTWalker
+{
+public:
+	using ASTWalker::operator();
+	void operator()(ForLoop const& _forLoop) override;
+	void operator()(Continue const&) override;
+	void operator()(Assignment const& _assignment) override;
+
+	std::set<YulString> const& names() const { return m_names; }
+	bool empty() const noexcept { return m_names.empty(); }
+
+private:
+	int m_forLoopDepth = 0;
+	bool m_continueFound = false;
+	std::set<YulString> m_names;
+};
+
 }