Merge pull request #6136 from ethereum/yul-break-continue

[Yul] introduce break/continue keywords.

libsolidity/analysis/ViewPureChecker.cpp

@@ -94,6 +94,12 @@ public:
 		(*this)(_for.body);
 		(*this)(_for.post);
 	}
+	void operator()(yul::Break const&)
+	{
+	}
+	void operator()(yul::Continue const&)
+	{
+	}
 	void operator()(yul::Block const& _block)
 	{
 		for (auto const& s: _block.statements)

libyul/AsmAnalysis.cpp

@@ -25,6 +25,7 @@
 #include <libyul/AsmScope.h>
 #include <libyul/AsmAnalysisInfo.h>
 #include <libyul/Utilities.h>
+#include <libyul/Exceptions.h>
 
 #include <liblangutil/ErrorReporter.h>
 
@@ -33,6 +34,7 @@
 
 #include <memory>
 #include <functional>
+#include <utility>
 
 using namespace std;
 using namespace dev;
@@ -472,7 +474,7 @@ bool AsmAnalyzer::operator()(ForLoop const& _for)
 {
 	solAssert(_for.condition, "");
 
-	Scope* originalScope = m_currentScope;
+	Scope* outerScope = m_currentScope;
 
 	bool success = true;
 	if (!(*this)(_for.pre))
@@ -485,18 +487,37 @@ bool AsmAnalyzer::operator()(ForLoop const& _for)
 	if (!expectExpression(*_for.condition))
 		success = false;
 	m_stackHeight--;
+
+	// backup outer for-loop & create new state
+	auto outerForLoop = m_currentForLoop;
+	m_currentForLoop = &_for;
+
 	if (!(*this)(_for.body))
 		success = false;
+
 	if (!(*this)(_for.post))
 		success = false;
 
 	m_stackHeight -= scope(&_for.pre).numberOfVariables();
 	m_info.stackHeightInfo[&_for] = m_stackHeight;
-	m_currentScope = originalScope;
+	m_currentScope = outerScope;
+	m_currentForLoop = outerForLoop;
 
 	return success;
 }
 
+bool AsmAnalyzer::operator()(Break const& _break)
+{
+	m_info.stackHeightInfo[&_break] = m_stackHeight;
+	return true;
+}
+
+bool AsmAnalyzer::operator()(Continue const& _continue)
+{
+	m_info.stackHeightInfo[&_continue] = m_stackHeight;
+	return true;
+}
+
 bool AsmAnalyzer::operator()(Block const& _block)
 {
 	bool success = true;

libyul/AsmAnalysis.h

@@ -34,6 +34,7 @@
 #include <boost/optional.hpp>
 
 #include <functional>
+#include <list>
 #include <memory>
 
 namespace langutil
@@ -93,6 +94,8 @@ public:
 	bool operator()(If const& _if);
 	bool operator()(Switch const& _switch);
 	bool operator()(ForLoop const& _forLoop);
+	bool operator()(Break const&);
+	bool operator()(Continue const&);
 	bool operator()(Block const& _block);
 
 private:
@@ -124,6 +127,7 @@ private:
 	langutil::EVMVersion m_evmVersion;
 	std::shared_ptr<Dialect> m_dialect;
 	boost::optional<langutil::Error::Type> m_errorTypeForLoose;
+	ForLoop const* m_currentForLoop = nullptr;
 };
 
 }

libyul/AsmData.h

@@ -78,6 +78,10 @@ struct Case { langutil::SourceLocation location; std::unique_ptr<Literal> value;
 /// Switch statement
 struct Switch { langutil::SourceLocation location; std::unique_ptr<Expression> expression; std::vector<Case> cases; };
 struct ForLoop { langutil::SourceLocation location; Block pre; std::unique_ptr<Expression> condition; Block post; Block body; };
+/// Break statement (valid within for loop)
+struct Break { langutil::SourceLocation location; };
+/// Continue statement (valid within for loop)
+struct Continue { langutil::SourceLocation location; };
 
 struct LocationExtractor: boost::static_visitor<langutil::SourceLocation>
 {

libyul/AsmDataForward.h

@@ -41,12 +41,14 @@ struct If;
 struct Switch;
 struct Case;
 struct ForLoop;
+struct Break;
+struct Continue;
 struct ExpressionStatement;
 struct Block;
 
 struct TypedName;
 
 using Expression = boost::variant<FunctionalInstruction, FunctionCall, Identifier, Literal>;
-using Statement = boost::variant<ExpressionStatement, Instruction, Label, StackAssignment, Assignment, VariableDeclaration, FunctionDefinition, If, Switch, ForLoop, Block>;
+using Statement = boost::variant<ExpressionStatement, Instruction, Label, StackAssignment, Assignment, VariableDeclaration, FunctionDefinition, If, Switch, ForLoop, Break, Continue, Block>;
 
 }

libyul/AsmParser.cpp

@@ -23,6 +23,7 @@
 #include <libyul/AsmParser.h>
 #include <liblangutil/Scanner.h>
 #include <liblangutil/ErrorReporter.h>
+#include <libdevcore/Common.h>
 
 #include <boost/algorithm/string.hpp>
 
@@ -104,6 +105,32 @@ Statement Parser::parseStatement()
 	}
 	case Token::For:
 		return parseForLoop();
+	case Token::Break:
+		if (m_insideForLoopBody)
+		{
+			auto stmt = Statement{ createWithLocation<Break>() };
+			m_scanner->next();
+			return stmt;
+		}
+		else
+		{
+			m_errorReporter.syntaxError(location(), "Keyword break outside for-loop body is not allowed.");
+			m_scanner->next();
+			return {};
+		}
+	case Token::Continue:
+		if (m_insideForLoopBody)
+		{
+			auto stmt = Statement{ createWithLocation<Continue>() };
+			m_scanner->next();
+			return stmt;
+		}
+		else
+		{
+			m_errorReporter.syntaxError(location(), "Keyword continue outside for-loop body is not allowed.");
+			m_scanner->next();
+			return {};
+		}
 	case Token::Assign:
 	{
 		if (m_dialect->flavour != AsmFlavour::Loose)
@@ -243,13 +270,19 @@ Case Parser::parseCase()
 
 ForLoop Parser::parseForLoop()
 {
+	bool outerForLoopBody = m_insideForLoopBody;
+	m_insideForLoopBody = false;
+
 	RecursionGuard recursionGuard(*this);
 	ForLoop forLoop = createWithLocation<ForLoop>();
 	expectToken(Token::For);
 	forLoop.pre = parseBlock();
 	forLoop.condition = make_unique<Expression>(parseExpression());
 	forLoop.post = parseBlock();
+
+	m_insideForLoopBody = true;
 	forLoop.body = parseBlock();
+	m_insideForLoopBody = outerForLoopBody;
 	forLoop.location.end = forLoop.body.location.end;
 	return forLoop;
 }
@@ -455,6 +488,9 @@ VariableDeclaration Parser::parseVariableDeclaration()
 FunctionDefinition Parser::parseFunctionDefinition()
 {
 	RecursionGuard recursionGuard(*this);
+	auto outerForLoopBody = m_insideForLoopBody;
+	m_insideForLoopBody = false;
+	ScopeGuard restoreInsideForLoopBody{[&]() { m_insideForLoopBody = outerForLoopBody; }};
 	FunctionDefinition funDef = createWithLocation<FunctionDefinition>();
 	expectToken(Token::Function);
 	funDef.name = expectAsmIdentifier();

libyul/AsmParser.h

@@ -39,7 +39,7 @@ class Parser: public langutil::ParserBase
 {
 public:
 	explicit Parser(langutil::ErrorReporter& _errorReporter, std::shared_ptr<Dialect> _dialect):
-		ParserBase(_errorReporter), m_dialect(std::move(_dialect)) {}
+		ParserBase(_errorReporter), m_dialect(std::move(_dialect)), m_insideForLoopBody{false} {}
 
 	/// Parses an inline assembly block starting with `{` and ending with `}`.
 	/// @param _reuseScanner if true, do check for end of input after the `}`.
@@ -87,6 +87,7 @@ protected:
 
 private:
 	std::shared_ptr<Dialect> m_dialect;
+	bool m_insideForLoopBody;
 };
 
 }

libyul/AsmPrinter.cpp

@@ -224,6 +224,16 @@ string AsmPrinter::operator()(ForLoop const& _forLoop) const
 	return out;
 }
 
+string AsmPrinter::operator()(Break const&) const
+{
+	return "break";
+}
+
+string AsmPrinter::operator()(Continue const&) const
+{
+	return "continue";
+}
+
 string AsmPrinter::operator()(Block const& _block) const
 {
 	if (_block.statements.empty())

libyul/AsmPrinter.h

@@ -50,6 +50,8 @@ public:
 	std::string operator()(If const& _if) const;
 	std::string operator()(Switch const& _switch) const;
 	std::string operator()(ForLoop const& _forLoop) const;
+	std::string operator()(Break const& _break) const;
+	std::string operator()(Continue const& _continue) const;
 	std::string operator()(Block const& _block) const;
 
 private:

libyul/AsmScopeFiller.h

@@ -63,6 +63,8 @@ public:
 	bool operator()(If const& _if);
 	bool operator()(Switch const& _switch);
 	bool operator()(ForLoop const& _forLoop);
+	bool operator()(Break const&) { return true; }
+	bool operator()(Continue const&) { return true; }
 	bool operator()(Block const& _block);
 
 private:

libyul/backends/evm/EVMCodeTransform.cpp

@@ -69,7 +69,6 @@ void VariableReferenceCounter::operator()(ForLoop const& _forLoop)
 	m_scope = originalScope;
 }
 
-
 void VariableReferenceCounter::operator()(Block const& _block)
 {
 	Scope* originalScope = m_scope;
@@ -92,7 +91,6 @@ void VariableReferenceCounter::increaseRefIfFound(YulString _variableName)
 	));
 }
 
-
 CodeTransform::CodeTransform(
 	AbstractAssembly& _assembly,
 	AsmAnalysisInfo& _analysisInfo,
@@ -605,11 +603,9 @@ void CodeTransform::operator()(ForLoop const& _forLoop)
 
 	visitStatements(_forLoop.pre.statements);
 
-	// TODO: When we implement break and continue, the labels and the stack heights at that point
-	// have to be stored in a stack.
 	AbstractAssembly::LabelID loopStart = m_assembly.newLabelId();
-	AbstractAssembly::LabelID loopEnd = m_assembly.newLabelId();
 	AbstractAssembly::LabelID postPart = m_assembly.newLabelId();
+	AbstractAssembly::LabelID loopEnd = m_assembly.newLabelId();
 
 	m_assembly.setSourceLocation(_forLoop.location);
 	m_assembly.appendLabel(loopStart);
@@ -619,6 +615,8 @@ void CodeTransform::operator()(ForLoop const& _forLoop)
 	m_assembly.appendInstruction(solidity::Instruction::ISZERO);
 	m_assembly.appendJumpToIf(loopEnd);
 
+	int const stackHeightBody = m_assembly.stackHeight();
+	m_context->forLoopStack.emplace(Context::ForLoopLabels{ {postPart, stackHeightBody}, {loopEnd, stackHeightBody} });
 	(*this)(_forLoop.body);
 
 	m_assembly.setSourceLocation(_forLoop.location);
@@ -631,7 +629,19 @@ void CodeTransform::operator()(ForLoop const& _forLoop)
 	m_assembly.appendLabel(loopEnd);
 
 	finalizeBlock(_forLoop.pre, stackStartHeight);
+	m_context->forLoopStack.pop();
 	m_scope = originalScope;
+	checkStackHeight(&_forLoop);
+}
+
+void CodeTransform::operator()(Break const&)
+{
+	yulAssert(false, "Code generation for break statement in Yul is not implemented yet.");
+}
+
+void CodeTransform::operator()(Continue const&)
+{
+	yulAssert(false, "Code generation for continue statement in Yul is not implemented yet.");
 }
 
 void CodeTransform::operator()(Block const& _block)

libyul/backends/evm/EVMCodeTransform.h

@@ -30,6 +30,8 @@
 #include <boost/variant.hpp>
 #include <boost/optional.hpp>
 
+#include <stack>
+
 namespace langutil
 {
 class ErrorReporter;
@@ -57,6 +59,20 @@ struct CodeTransformContext
 	std::map<Scope::Function const*, AbstractAssembly::LabelID> functionEntryIDs;
 	std::map<Scope::Variable const*, int> variableStackHeights;
 	std::map<Scope::Variable const*, unsigned> variableReferences;
+
+	struct JumpInfo
+	{
+		AbstractAssembly::LabelID label;  ///< Jump's LabelID to jump to.
+		int targetStackHeight;            ///< Stack height after the jump.
+	};
+
+	struct ForLoopLabels
+	{
+		JumpInfo post; ///< Jump info for jumping to post branch.
+		JumpInfo done; ///< Jump info for jumping to done branch.
+	};
+
+	std::stack<ForLoopLabels> forLoopStack;
 };
 
 /**
@@ -166,6 +182,8 @@ public:
 	void operator()(Switch const& _switch);
 	void operator()(FunctionDefinition const&);
 	void operator()(ForLoop const&);
+	void operator()(Break const&);
+	void operator()(Continue const&);
 	void operator()(Block const& _block);
 
 private:

libyul/optimiser/ASTCopier.cpp

@@ -138,6 +138,15 @@ Statement ASTCopier::operator()(ForLoop const& _forLoop)
 		translate(_forLoop.body)
 	};
 }
+Statement ASTCopier::operator()(Break const& _break)
+{
+	return Break{ _break };
+}
+
+Statement ASTCopier::operator()(Continue const& _continue)
+{
+	return Continue{ _continue };
+}
 
 Statement ASTCopier::operator ()(Block const& _block)
 {

libyul/optimiser/ASTCopier.h

@@ -58,6 +58,8 @@ public:
 	virtual Statement operator()(Switch const& _switch) = 0;
 	virtual Statement operator()(FunctionDefinition const&) = 0;
 	virtual Statement operator()(ForLoop const&) = 0;
+	virtual Statement operator()(Break const&) = 0;
+	virtual Statement operator()(Continue const&) = 0;
 	virtual Statement operator()(Block const& _block) = 0;
 };
 
@@ -83,6 +85,8 @@ public:
 	Statement operator()(Switch const& _switch) override;
 	Statement operator()(FunctionDefinition const&) override;
 	Statement operator()(ForLoop const&) override;
+	Statement operator()(Break const&) override;
+	Statement operator()(Continue const&) override;
 	Statement operator()(Block const& _block) override;
 
 	virtual Expression translate(Expression const& _expression);

libyul/optimiser/ASTWalker.cpp

@@ -161,6 +161,14 @@ void ASTModifier::operator()(ForLoop& _for)
 	(*this)(_for.body);
 }
 
+void ASTModifier::operator()(Break&)
+{
+}
+
+void ASTModifier::operator()(Continue&)
+{
+}
+
 void ASTModifier::operator()(Block& _block)
 {
 	walkVector(_block.statements);

libyul/optimiser/ASTWalker.h

@@ -56,6 +56,8 @@ public:
 	virtual void operator()(Switch const& _switch);
 	virtual void operator()(FunctionDefinition const&);
 	virtual void operator()(ForLoop const&);
+	virtual void operator()(Break const&) {}
+	virtual void operator()(Continue const&) {}
 	virtual void operator()(Block const& _block);
 
 	virtual void visit(Statement const& _st);
@@ -91,6 +93,8 @@ public:
 	virtual void operator()(Switch& _switch);
 	virtual void operator()(FunctionDefinition&);
 	virtual void operator()(ForLoop&);
+	virtual void operator()(Break&);
+	virtual void operator()(Continue&);
 	virtual void operator()(Block& _block);
 
 	virtual void visit(Statement& _st);

libyul/optimiser/DataFlowAnalyzer.cpp

@@ -130,6 +130,16 @@ void DataFlowAnalyzer::operator()(ForLoop& _for)
 	popScope();
 }
 
+void DataFlowAnalyzer::operator()(Break&)
+{
+	yulAssert(false, "Not implemented yet.");
+}
+
+void DataFlowAnalyzer::operator()(Continue&)
+{
+	yulAssert(false, "Not implemented yet.");
+}
+
 void DataFlowAnalyzer::operator()(Block& _block)
 {
 	size_t numScopes = m_variableScopes.size();

libyul/optimiser/DataFlowAnalyzer.h

@@ -53,6 +53,8 @@ public:
 	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/RedundantAssignEliminator.cpp

@@ -149,6 +149,16 @@ void RedundantAssignEliminator::operator()(ForLoop const& _forLoop)
 	join(zeroRuns);
 }
 
+void RedundantAssignEliminator::operator()(Break const&)
+{
+	yulAssert(false, "Not implemented yet.");
+}
+
+void RedundantAssignEliminator::operator()(Continue const&)
+{
+	yulAssert(false, "Not implemented yet.");
+}
+
 void RedundantAssignEliminator::operator()(Block const& _block)
 {
 	// This will set all variables that are declared in this

libyul/optimiser/RedundantAssignEliminator.h

@@ -112,6 +112,8 @@ public:
 	void operator()(Switch const& _switch) override;
 	void operator()(FunctionDefinition const&) override;
 	void operator()(ForLoop const&) override;
+	void operator()(Break const&) override;
+	void operator()(Continue const&) override;
 	void operator()(Block const& _block) override;
 
 	static void run(Dialect const& _dialect, Block& _ast);

libyul/optimiser/SyntacticalEquality.h

@@ -55,6 +55,8 @@ public:
 	bool statementEqual(Switch const& _lhs, Switch const& _rhs);
 	bool switchCaseEqual(Case const& _lhs, Case const& _rhs);
 	bool statementEqual(ForLoop const& _lhs, ForLoop const& _rhs);
+	bool statementEqual(Break const&, Break const&) { return true; }
+	bool statementEqual(Continue const&, Continue const&) { return true; }
 	bool statementEqual(Block const& _lhs, Block const& _rhs);
 private:
 	bool statementEqual(Instruction const& _lhs, Instruction const& _rhs);

test/libyul/Parser.cpp

@@ -295,6 +295,74 @@ BOOST_AUTO_TEST_CASE(if_statement)
 	BOOST_CHECK(successParse("{ function f() -> x:bool {} if f() { let b:bool := f() } }"));
 }
 
+BOOST_AUTO_TEST_CASE(for_statement)
+{
+	auto dialect = EVMDialect::strictAssemblyForEVMObjects(EVMVersion::constantinople());
+	BOOST_CHECK(successParse("{ for {let i := 0} iszero(eq(i, 10)) {i := add(i, 1)} {} }", dialect));
+}
+
+BOOST_AUTO_TEST_CASE(for_statement_break)
+{
+	auto dialect = EVMDialect::strictAssemblyForEVMObjects(EVMVersion::constantinople());
+	BOOST_CHECK(successParse("{ for {let i := 0} iszero(eq(i, 10)) {i := add(i, 1)} {break} }", dialect));
+}
+
+BOOST_AUTO_TEST_CASE(for_statement_break_init)
+{
+	auto dialect = EVMDialect::strictAssemblyForEVMObjects(EVMVersion::constantinople());
+	CHECK_ERROR_DIALECT(
+		"{ for {let i := 0 break} iszero(eq(i, 10)) {i := add(i, 1)} {} }",
+		SyntaxError,
+		"Keyword break outside for-loop body is not allowed.",
+		dialect);
+}
+
+BOOST_AUTO_TEST_CASE(for_statement_break_post)
+{
+	auto dialect = EVMDialect::strictAssemblyForEVMObjects(EVMVersion::constantinople());
+	CHECK_ERROR_DIALECT(
+		"{ for {let i := 0} iszero(eq(i, 10)) {i := add(i, 1) break} {} }",
+		SyntaxError,
+		"Keyword break outside for-loop body is not allowed.",
+		dialect);
+}
+
+BOOST_AUTO_TEST_CASE(for_statement_nested_break)
+{
+	auto dialect = EVMDialect::strictAssemblyForEVMObjects(EVMVersion::constantinople());
+	CHECK_ERROR_DIALECT(
+		"{ for {let i := 0} iszero(eq(i, 10)) {} { function f() { break } } }",
+		SyntaxError,
+		"Keyword break outside for-loop body is not allowed.",
+		dialect);
+}
+
+BOOST_AUTO_TEST_CASE(for_statement_continue)
+{
+	auto dialect = EVMDialect::strictAssemblyForEVMObjects(EVMVersion::constantinople());
+	BOOST_CHECK(successParse("{ for {let i := 0} iszero(eq(i, 10)) {i := add(i, 1)} {continue} }", dialect));
+}
+
+BOOST_AUTO_TEST_CASE(for_statement_continue_fail_init)
+{
+	auto dialect = EVMDialect::strictAssemblyForEVMObjects(EVMVersion::constantinople());
+	CHECK_ERROR_DIALECT(
+		"{ for {let i := 0 continue} iszero(eq(i, 10)) {i := add(i, 1)} {} }",
+		SyntaxError,
+		"Keyword continue outside for-loop body is not allowed.",
+		dialect);
+}
+
+BOOST_AUTO_TEST_CASE(for_statement_continue_fail_post)
+{
+	auto dialect = EVMDialect::strictAssemblyForEVMObjects(EVMVersion::constantinople());
+	CHECK_ERROR_DIALECT(
+		"{ for {let i := 0} iszero(eq(i, 10)) {i := add(i, 1) continue} {} }",
+		SyntaxError,
+		"Keyword continue outside for-loop body is not allowed.",
+		dialect);
+}
+
 BOOST_AUTO_TEST_CASE(if_statement_invalid)
 {
 	CHECK_ERROR("{ if let x:u256 {} }", ParserError, "Literal or identifier expected.");

test/tools/yulInterpreter/Interpreter.cpp

@@ -105,12 +105,27 @@ void Interpreter::operator()(ForLoop const& _forLoop)
 		visit(statement);
 	while (evaluate(*_forLoop.condition) != 0)
 	{
+		m_state.loopState = LoopState::Default;
 		(*this)(_forLoop.body);
+		if (m_state.loopState == LoopState::Break)
+			break;
+
 		(*this)(_forLoop.post);
 	}
+	m_state.loopState = LoopState::Default;
 	closeScope();
 }
 
+void Interpreter::operator()(Break const&)
+{
+	m_state.loopState = LoopState::Break;
+}
+
+void Interpreter::operator()(Continue const&)
+{
+	m_state.loopState = LoopState::Continue;
+}
+
 void Interpreter::operator()(Block const& _block)
 {
 	openScope();
@@ -122,7 +137,14 @@ void Interpreter::operator()(Block const& _block)
 			m_functions[funDef.name] = &funDef;
 			m_scopes.back().insert(funDef.name);
 		}
-	ASTWalker::operator()(_block);
+
+	for (auto const& statement: _block.statements)
+	{
+		visit(statement);
+		if (m_state.loopState != LoopState::Default)
+			break;
+	}
+
 	closeScope();
 }
 

test/tools/yulInterpreter/Interpreter.h

@@ -39,6 +39,13 @@ class InterpreterTerminated: dev::Exception
 {
 };
 
+enum class LoopState
+{
+	Default,
+	Continue,
+	Break,
+};
+
 struct InterpreterState
 {
 	dev::bytes calldata;
@@ -65,6 +72,7 @@ struct InterpreterState
 	std::vector<std::string> trace;
 	/// This is actually an input parameter that more or less limits the runtime.
 	size_t maxTraceSize = 0;
+	LoopState loopState = LoopState::Default;
 };
 
 /**
@@ -90,6 +98,8 @@ public:
 	void operator()(Switch const& _switch) override;
 	void operator()(FunctionDefinition const&) override;
 	void operator()(ForLoop const&) override;
+	void operator()(Break const&) override;
+	void operator()(Continue const&) override;
 	void operator()(Block const& _block) override;
 
 	std::vector<std::string> const& trace() const { return m_state.trace; }