Merge pull request #2304 from ethereum/evm15asm

Implementation of EVM 1.5 backend

5 files changed, 637 insertions, 129 deletions

diff --git a/libjulia/backends/evm/AbstractAssembly.h b/libjulia/backends/evm/AbstractAssembly.h
index de31be28..f667c1a7 100644
--- a/libjulia/backends/evm/AbstractAssembly.h
+++ b/libjulia/backends/evm/AbstractAssembly.h
@@ -41,6 +41,9 @@ struct Identifier;
 namespace julia
 {
 
+///
+/// Assembly class that abstracts both the libevmasm assembly and the new julia evm assembly.
+///
 class AbstractAssembly
 {
 public:
@@ -66,6 +69,26 @@ public:
 	/// Append a reference to a to-be-linked symobl.
 	/// Currently, we assume that the value is always a 20 byte number.
 	virtual void appendLinkerSymbol(std::string const& _name) = 0;
+
+	/// Append a jump instruction.
+	/// @param _stackDiffAfter the stack adjustment after this instruction.
+	/// This is helpful to stack height analysis if there is no continuing control flow.
+	virtual void appendJump(int _stackDiffAfter) = 0;
+
+	/// Append a jump-to-immediate operation.
+	/// @param _stackDiffAfter the stack adjustment after this instruction.
+	virtual void appendJumpTo(LabelID _labelId, int _stackDiffAfter = 0) = 0;
+	/// Append a jump-to-if-immediate operation.
+	virtual void appendJumpToIf(LabelID _labelId) = 0;
+	/// Start a subroutine identified by @a _labelId that takes @a _arguments
+	/// stack slots as arguments.
+	virtual void appendBeginsub(LabelID _labelId, int _arguments) = 0;
+	/// Call a subroutine identified by @a _labelId, taking @a _arguments from the
+	/// stack upon call and putting @a _returns arguments onto the stack upon return.
+	virtual void appendJumpsub(LabelID _labelId, int _arguments, int _returns) = 0;
+	/// Return from a subroutine.
+	/// @param _stackDiffAfter the stack adjustment after this instruction.
+	virtual void appendReturnsub(int _returns, int _stackDiffAfter = 0) = 0;
 };
 
 enum class IdentifierContext { LValue, RValue };
@@ -74,7 +97,7 @@ enum class IdentifierContext { LValue, RValue };
 /// to inline assembly (not used in standalone assembly mode).
 struct ExternalIdentifierAccess
 {
-	using Resolver = std::function<size_t(solidity::assembly::Identifier const&, IdentifierContext)>;
+	using Resolver = std::function<size_t(solidity::assembly::Identifier const&, IdentifierContext, bool /*_crossesFunctionBoundary*/)>;
 	/// Resolve a an external reference given by the identifier in the given context.
 	/// @returns the size of the value (number of stack slots) or size_t(-1) if not found.
 	Resolver resolve;
diff --git a/libjulia/backends/evm/EVMAssembly.cpp b/libjulia/backends/evm/EVMAssembly.cpp
new file mode 100644
index 00000000..daca2393
--- /dev/null
+++ b/libjulia/backends/evm/EVMAssembly.cpp
@@ -0,0 +1,175 @@
+/*
+	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/>.
+*/
+/**
+ * Assembly interface for EVM and EVM1.5.
+ */
+
+#include <libjulia/backends/evm/EVMAssembly.h>
+
+#include <libevmasm/Instruction.h>
+
+#include <libsolidity/interface/Utils.h>
+
+using namespace std;
+using namespace dev;
+using namespace julia;
+
+namespace
+{
+/// Size of labels in bytes. Four-byte labels are required by some EVM1.5 instructions.
+size_t constexpr labelReferenceSize = 4;
+}
+
+
+void EVMAssembly::setSourceLocation(SourceLocation const&)
+{
+	// Ignored for now;
+}
+
+void EVMAssembly::appendInstruction(solidity::Instruction _instr)
+{
+	m_bytecode.push_back(byte(_instr));
+	m_stackHeight += solidity::instructionInfo(_instr).ret - solidity::instructionInfo(_instr).args;
+}
+
+void EVMAssembly::appendConstant(u256 const& _constant)
+{
+	bytes data = toCompactBigEndian(_constant, 1);
+	appendInstruction(solidity::pushInstruction(data.size()));
+	m_bytecode += data;
+}
+
+void EVMAssembly::appendLabel(LabelID _labelId)
+{
+	setLabelToCurrentPosition(_labelId);
+	appendInstruction(solidity::Instruction::JUMPDEST);
+}
+
+void EVMAssembly::appendLabelReference(LabelID _labelId)
+{
+	solAssert(!m_evm15, "Cannot use plain label references in EMV1.5 mode.");
+	// @TODO we now always use labelReferenceSize for all labels, it could be shortened
+	// for some of them.
+	appendInstruction(solidity::pushInstruction(labelReferenceSize));
+	m_labelReferences[m_bytecode.size()] = _labelId;
+	m_bytecode += bytes(labelReferenceSize);
+}
+
+EVMAssembly::LabelID EVMAssembly::newLabelId()
+{
+	m_labelPositions[m_nextLabelId] = size_t(-1);
+	return m_nextLabelId++;
+}
+
+void EVMAssembly::appendLinkerSymbol(string const&)
+{
+	solAssert(false, "Linker symbols not yet implemented.");
+}
+
+void EVMAssembly::appendJump(int _stackDiffAfter)
+{
+	solAssert(!m_evm15, "Plain JUMP used for EVM 1.5");
+	appendInstruction(solidity::Instruction::JUMP);
+	m_stackHeight += _stackDiffAfter;
+}
+
+void EVMAssembly::appendJumpTo(LabelID _labelId, int _stackDiffAfter)
+{
+	if (m_evm15)
+	{
+		m_bytecode.push_back(byte(solidity::Instruction::JUMPTO));
+		appendLabelReferenceInternal(_labelId);
+		m_stackHeight += _stackDiffAfter;
+	}
+	else
+	{
+		appendLabelReference(_labelId);
+		appendJump(_stackDiffAfter);
+	}
+}
+
+void EVMAssembly::appendJumpToIf(LabelID _labelId)
+{
+	if (m_evm15)
+	{
+		m_bytecode.push_back(byte(solidity::Instruction::JUMPIF));
+		appendLabelReferenceInternal(_labelId);
+		m_stackHeight--;
+	}
+	else
+	{
+		appendLabelReference(_labelId);
+		appendInstruction(solidity::Instruction::JUMPI);
+	}
+}
+
+void EVMAssembly::appendBeginsub(LabelID _labelId, int _arguments)
+{
+	solAssert(m_evm15, "BEGINSUB used for EVM 1.0");
+	solAssert(_arguments >= 0, "");
+	setLabelToCurrentPosition(_labelId);
+	m_bytecode.push_back(byte(solidity::Instruction::BEGINSUB));
+	m_stackHeight += _arguments;
+}
+
+void EVMAssembly::appendJumpsub(LabelID _labelId, int _arguments, int _returns)
+{
+	solAssert(m_evm15, "JUMPSUB used for EVM 1.0");
+	solAssert(_arguments >= 0 && _returns >= 0, "");
+	m_bytecode.push_back(byte(solidity::Instruction::JUMPSUB));
+	appendLabelReferenceInternal(_labelId);
+	m_stackHeight += _returns - _arguments;
+}
+
+void EVMAssembly::appendReturnsub(int _returns, int _stackDiffAfter)
+{
+	solAssert(m_evm15, "RETURNSUB used for EVM 1.0");
+	solAssert(_returns >= 0, "");
+	m_bytecode.push_back(byte(solidity::Instruction::RETURNSUB));
+	m_stackHeight += _stackDiffAfter - _returns;
+}
+
+eth::LinkerObject EVMAssembly::finalize()
+{
+	for (auto const& ref: m_labelReferences)
+	{
+		size_t referencePos = ref.first;
+		solAssert(m_labelPositions.count(ref.second), "");
+		size_t labelPos = m_labelPositions.at(ref.second);
+		solAssert(labelPos != size_t(-1), "Undefined but allocated label used.");
+		solAssert(m_bytecode.size() >= 4 && referencePos <= m_bytecode.size() - 4, "");
+		solAssert(uint64_t(labelPos) < (uint64_t(1) << (8 * labelReferenceSize)), "");
+		for (size_t i = 0; i < labelReferenceSize; i++)
+			m_bytecode[referencePos + i] = byte((labelPos >> (8 * (labelReferenceSize - i - 1))) & 0xff);
+	}
+	eth::LinkerObject obj;
+	obj.bytecode = m_bytecode;
+	return obj;
+}
+
+void EVMAssembly::setLabelToCurrentPosition(LabelID _labelId)
+{
+	solAssert(m_labelPositions.count(_labelId), "Label not found.");
+	solAssert(m_labelPositions[_labelId] == size_t(-1), "Label already set.");
+	m_labelPositions[_labelId] = m_bytecode.size();
+}
+
+void EVMAssembly::appendLabelReferenceInternal(LabelID _labelId)
+{
+	m_labelReferences[m_bytecode.size()] = _labelId;
+	m_bytecode += bytes(labelReferenceSize);
+}
diff --git a/libjulia/backends/evm/EVMAssembly.h b/libjulia/backends/evm/EVMAssembly.h
new file mode 100644
index 00000000..a2df0cdc
--- /dev/null
+++ b/libjulia/backends/evm/EVMAssembly.h
@@ -0,0 +1,90 @@
+/*
+	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/>.
+*/
+/**
+ * Assembly interface for EVM and EVM1.5.
+ */
+
+#pragma once
+
+#include <libjulia/backends/evm/AbstractAssembly.h>
+
+#include <libevmasm/LinkerObject.h>
+
+#include <map>
+
+namespace dev
+{
+namespace julia
+{
+
+class EVMAssembly: public AbstractAssembly
+{
+public:
+	explicit EVMAssembly(bool _evm15 = false): m_evm15(_evm15) { }
+	virtual ~EVMAssembly() {}
+
+	/// Set a new source location valid starting from the next instruction.
+	virtual void setSourceLocation(SourceLocation const& _location) override;
+	/// Retrieve the current height of the stack. This does not have to be zero
+	/// at the beginning.
+	virtual int stackHeight() const override { return m_stackHeight; }
+	/// Append an EVM instruction.
+	virtual void appendInstruction(solidity::Instruction _instruction) override;
+	/// Append a constant.
+	virtual void appendConstant(u256 const& _constant) override;
+	/// Append a label.
+	virtual void appendLabel(LabelID _labelId) override;
+	/// Append a label reference.
+	virtual void appendLabelReference(LabelID _labelId) override;
+	/// Generate a new unique label.
+	virtual LabelID newLabelId() override;
+	/// Append a reference to a to-be-linked symobl.
+	/// Currently, we assume that the value is always a 20 byte number.
+	virtual void appendLinkerSymbol(std::string const& _name) override;
+
+	/// Append a jump instruction.
+	/// @param _stackDiffAfter the stack adjustment after this instruction.
+	virtual void appendJump(int _stackDiffAfter) override;
+	/// Append a jump-to-immediate operation.
+	virtual void appendJumpTo(LabelID _labelId, int _stackDiffAfter) override;
+	/// Append a jump-to-if-immediate operation.
+	virtual void appendJumpToIf(LabelID _labelId) override;
+	/// Start a subroutine.
+	virtual void appendBeginsub(LabelID _labelId, int _arguments) override;
+	/// Call a subroutine.
+	virtual void appendJumpsub(LabelID _labelId, int _arguments, int _returns) override;
+	/// Return from a subroutine.
+	virtual void appendReturnsub(int _returns, int _stackDiffAfter) override;
+
+
+	/// Resolves references inside the bytecode and returns the linker object.
+	eth::LinkerObject finalize();
+
+private:
+	void setLabelToCurrentPosition(AbstractAssembly::LabelID _labelId);
+	void appendLabelReferenceInternal(AbstractAssembly::LabelID _labelId);
+
+	bool m_evm15 = false; ///< if true, switch to evm1.5 mode
+	LabelID m_nextLabelId = 0;
+	int m_stackHeight = 0;
+	bytes m_bytecode;
+	std::map<LabelID, size_t> m_labelPositions;
+	std::map<size_t, LabelID> m_labelReferences;
+};
+
+}
+}
diff --git a/libjulia/backends/evm/EVMCodeTransform.cpp b/libjulia/backends/evm/EVMCodeTransform.cpp
index 355a9595..cd6fd276 100644
--- a/libjulia/backends/evm/EVMCodeTransform.cpp
+++ b/libjulia/backends/evm/EVMCodeTransform.cpp
@@ -25,179 +25,155 @@
 
 #include <libsolidity/interface/Utils.h>
 
+#include <boost/range/adaptor/reversed.hpp>
+
 using namespace std;
 using namespace dev;
 using namespace dev::julia;
 using namespace dev::solidity;
 using namespace dev::solidity::assembly;
 
-CodeTransform::CodeTransform(
-	ErrorReporter& _errorReporter,
-	AbstractAssembly& _assembly,
-	Block const& _block,
-	AsmAnalysisInfo& _analysisInfo,
-	ExternalIdentifierAccess const& _identifierAccess,
-	int _initialStackHeight
-):
-	m_errorReporter(_errorReporter),
-	m_assembly(_assembly),
-	m_info(_analysisInfo),
-	m_scope(*_analysisInfo.scopes.at(&_block)),
-	m_identifierAccess(_identifierAccess),
-	m_initialStackHeight(_initialStackHeight)
+void CodeTransform::run(Block const& _block)
 {
+	m_scope = m_info.scopes.at(&_block).get();
+
 	int blockStartStackHeight = m_assembly.stackHeight();
 	std::for_each(_block.statements.begin(), _block.statements.end(), boost::apply_visitor(*this));
 
 	m_assembly.setSourceLocation(_block.location);
 
 	// pop variables
-	for (auto const& identifier: m_scope.identifiers)
+	for (auto const& identifier: m_scope->identifiers)
 		if (identifier.second.type() == typeid(Scope::Variable))
 			m_assembly.appendInstruction(solidity::Instruction::POP);
 
 	int deposit = m_assembly.stackHeight() - blockStartStackHeight;
 	solAssert(deposit == 0, "Invalid stack height at end of block.");
-}
-
-void CodeTransform::operator()(const FunctionDefinition&)
-{
-	solAssert(false, "Function definition not removed during desugaring phase.");
-}
-
-void CodeTransform::generateAssignment(Identifier const& _variableName, SourceLocation const& _location)
-{
-	auto var = m_scope.lookup(_variableName.name);
-	if (var)
-	{
-		Scope::Variable const& _var = boost::get<Scope::Variable>(*var);
-		if (int heightDiff = variableHeightDiff(_var, _location, true))
-			m_assembly.appendInstruction(solidity::swapInstruction(heightDiff - 1));
-		m_assembly.appendInstruction(solidity::Instruction::POP);
-	}
-	else
-	{
-		solAssert(
-			m_identifierAccess.generateCode,
-			"Identifier not found and no external access available."
-		);
-		m_identifierAccess.generateCode(_variableName, IdentifierContext::LValue, m_assembly);
-	}
-}
-
-int CodeTransform::variableHeightDiff(solidity::assembly::Scope::Variable const& _var, SourceLocation const& _location, bool _forSwap)
-{
-	int heightDiff = m_assembly.stackHeight() - _var.stackHeight;
-	if (heightDiff <= (_forSwap ? 1 : 0) || heightDiff > (_forSwap ? 17 : 16))
-	{
-		//@TODO move this to analysis phase.
-		m_errorReporter.typeError(
-			_location,
-			"Variable inaccessible, too deep inside stack (" + boost::lexical_cast<string>(heightDiff) + ")"
-		);
-		return 0;
-	}
-	else
-		return heightDiff;
-}
-
-void CodeTransform::expectDeposit(int _deposit, int _oldHeight)
-{
-	solAssert(m_assembly.stackHeight() == _oldHeight + _deposit, "Invalid stack deposit.");
-}
-
-void CodeTransform::checkStackHeight(void const* _astElement)
-{
-	solAssert(m_info.stackHeightInfo.count(_astElement), "Stack height for AST element not found.");
-	solAssert(
-		m_info.stackHeightInfo.at(_astElement) == m_assembly.stackHeight() - m_initialStackHeight,
-		"Stack height mismatch between analysis and code generation phase."
-	);
-}
-
-void CodeTransform::assignLabelIdIfUnset(Scope::Label& _label)
-{
-	if (!_label.id)
-		_label.id.reset(m_assembly.newLabelId());
-}
-
-void CodeTransform::operator()(Block const& _block)
-{
-	CodeTransform(m_errorReporter, m_assembly, _block, m_info, m_identifierAccess, m_initialStackHeight);
 	checkStackHeight(&_block);
 }
 
-void CodeTransform::operator()(Switch const&)
-{
-	solAssert(false, "Switch not removed during desugaring phase.");
-}
 
 void CodeTransform::operator()(VariableDeclaration const& _varDecl)
 {
+	solAssert(m_scope, "");
+
 	int expectedItems = _varDecl.variables.size();
 	int height = m_assembly.stackHeight();
 	boost::apply_visitor(*this, *_varDecl.value);
 	expectDeposit(expectedItems, height);
 	for (auto const& variable: _varDecl.variables)
 	{
-		auto& var = boost::get<Scope::Variable>(m_scope.identifiers.at(variable.name));
+		auto& var = boost::get<Scope::Variable>(m_scope->identifiers.at(variable.name));
 		var.stackHeight = height++;
 		var.active = true;
 	}
+	checkStackHeight(&_varDecl);
 }
 
 void CodeTransform::operator()(Assignment const& _assignment)
 {
-	int height = m_assembly.stackHeight();
-	boost::apply_visitor(*this, *_assignment.value);
-	expectDeposit(1, height);
+	visitExpression(*_assignment.value);
 	m_assembly.setSourceLocation(_assignment.location);
-	generateAssignment(_assignment.variableName, _assignment.location);
+	generateAssignment(_assignment.variableName);
 	checkStackHeight(&_assignment);
 }
 
 void CodeTransform::operator()(StackAssignment const& _assignment)
 {
 	m_assembly.setSourceLocation(_assignment.location);
-	generateAssignment(_assignment.variableName, _assignment.location);
+	generateAssignment(_assignment.variableName);
 	checkStackHeight(&_assignment);
 }
 
 void CodeTransform::operator()(Label const& _label)
 {
 	m_assembly.setSourceLocation(_label.location);
-	solAssert(m_scope.identifiers.count(_label.name), "");
-	Scope::Label& label = boost::get<Scope::Label>(m_scope.identifiers.at(_label.name));
-	assignLabelIdIfUnset(label);
+	solAssert(m_scope, "");
+	solAssert(m_scope->identifiers.count(_label.name), "");
+	Scope::Label& label = boost::get<Scope::Label>(m_scope->identifiers.at(_label.name));
+	assignLabelIdIfUnset(label.id);
 	m_assembly.appendLabel(*label.id);
 	checkStackHeight(&_label);
 }
 
-void CodeTransform::operator()(FunctionCall const&)
+void CodeTransform::operator()(FunctionCall const& _call)
 {
-	solAssert(false, "Function call not removed during desugaring phase.");
+	solAssert(m_scope, "");
+
+	m_assembly.setSourceLocation(_call.location);
+	EVMAssembly::LabelID returnLabel(-1); // only used for evm 1.0
+	if (!m_evm15)
+	{
+		returnLabel = m_assembly.newLabelId();
+		m_assembly.appendLabelReference(returnLabel);
+		m_stackAdjustment++;
+	}
+
+	Scope::Function* function = nullptr;
+	solAssert(m_scope->lookup(_call.functionName.name, Scope::NonconstVisitor(
+		[=](Scope::Variable&) { solAssert(false, "Expected function name."); },
+		[=](Scope::Label&) { solAssert(false, "Expected function name."); },
+		[&](Scope::Function& _function) { function = &_function; }
+	)), "Function name not found.");
+	solAssert(function, "");
+	solAssert(function->arguments.size() == _call.arguments.size(), "");
+	for (auto const& arg: _call.arguments | boost::adaptors::reversed)
+		visitExpression(arg);
+	m_assembly.setSourceLocation(_call.location);
+	assignLabelIdIfUnset(function->id);
+	if (m_evm15)
+		m_assembly.appendJumpsub(*function->id, function->arguments.size(), function->returns.size());
+	else
+	{
+		m_assembly.appendJumpTo(*function->id, function->returns.size() - function->arguments.size() - 1);
+		m_assembly.appendLabel(returnLabel);
+		m_stackAdjustment--;
+	}
+	checkStackHeight(&_call);
 }
 
-void CodeTransform::operator()(FunctionalInstruction const& _instr)
+void CodeTransform::operator()(FunctionalInstruction const& _instruction)
 {
-	for (auto it = _instr.arguments.rbegin(); it != _instr.arguments.rend(); ++it)
+	if (m_evm15 && (
+		_instruction.instruction.instruction == solidity::Instruction::JUMP ||
+		_instruction.instruction.instruction == solidity::Instruction::JUMPI
+	))
 	{
-		int height = m_assembly.stackHeight();
-		boost::apply_visitor(*this, *it);
-		expectDeposit(1, height);
+		bool const isJumpI = _instruction.instruction.instruction == solidity::Instruction::JUMPI;
+		if (isJumpI)
+		{
+			solAssert(_instruction.arguments.size() == 2, "");
+			visitExpression(_instruction.arguments.at(1));
+		}
+		else
+		{
+			solAssert(_instruction.arguments.size() == 1, "");
+		}
+		m_assembly.setSourceLocation(_instruction.location);
+		auto label = labelFromIdentifier(boost::get<assembly::Identifier>(_instruction.arguments.at(0)));
+		if (isJumpI)
+			m_assembly.appendJumpToIf(label);
+		else
+			m_assembly.appendJumpTo(label);
+	}
+	else
+	{
+		for (auto const& arg: _instruction.arguments | boost::adaptors::reversed)
+			visitExpression(arg);
+		(*this)(_instruction.instruction);
 	}
-	(*this)(_instr.instruction);
-	checkStackHeight(&_instr);
+	checkStackHeight(&_instruction);
 }
 
 void CodeTransform::operator()(assembly::Identifier const& _identifier)
 {
 	m_assembly.setSourceLocation(_identifier.location);
 	// First search internals, then externals.
-	if (m_scope.lookup(_identifier.name, Scope::NonconstVisitor(
+	solAssert(m_scope, "");
+	if (m_scope->lookup(_identifier.name, Scope::NonconstVisitor(
 		[=](Scope::Variable& _var)
 		{
-			if (int heightDiff = variableHeightDiff(_var, _identifier.location, false))
+			if (int heightDiff = variableHeightDiff(_var, false))
 				m_assembly.appendInstruction(solidity::dupInstruction(heightDiff));
 			else
 				// Store something to balance the stack
@@ -205,7 +181,7 @@ void CodeTransform::operator()(assembly::Identifier const& _identifier)
 		},
 		[=](Scope::Label& _label)
 		{
-			assignLabelIdIfUnset(_label);
+			assignLabelIdIfUnset(_label.id);
 			m_assembly.appendLabelReference(*_label.id);
 		},
 		[=](Scope::Function&)
@@ -246,7 +222,233 @@ void CodeTransform::operator()(assembly::Literal const& _literal)
 
 void CodeTransform::operator()(assembly::Instruction const& _instruction)
 {
+	solAssert(!m_evm15 || _instruction.instruction != solidity::Instruction::JUMP, "Bare JUMP instruction used for EVM1.5");
+	solAssert(!m_evm15 || _instruction.instruction != solidity::Instruction::JUMPI, "Bare JUMPI instruction used for EVM1.5");
 	m_assembly.setSourceLocation(_instruction.location);
 	m_assembly.appendInstruction(_instruction.instruction);
 	checkStackHeight(&_instruction);
 }
+
+void CodeTransform::operator()(Switch const& _switch)
+{
+	//@TODO use JUMPV in EVM1.5?
+
+	visitExpression(*_switch.expression);
+	int expressionHeight = m_assembly.stackHeight();
+	map<Case const*, AbstractAssembly::LabelID> caseBodies;
+	AbstractAssembly::LabelID end = m_assembly.newLabelId();
+	for (Case const& c: _switch.cases)
+	{
+		if (c.value)
+		{
+			(*this)(*c.value);
+			m_assembly.setSourceLocation(c.location);
+			AbstractAssembly::LabelID bodyLabel = m_assembly.newLabelId();
+			caseBodies[&c] = bodyLabel;
+			solAssert(m_assembly.stackHeight() == expressionHeight + 1, "");
+			m_assembly.appendInstruction(solidity::dupInstruction(2));
+			m_assembly.appendInstruction(solidity::Instruction::EQ);
+			m_assembly.appendJumpToIf(bodyLabel);
+		}
+		else
+			// default case
+			(*this)(c.body);
+	}
+	m_assembly.setSourceLocation(_switch.location);
+	m_assembly.appendJumpTo(end);
+
+	size_t numCases = caseBodies.size();
+	for (auto const& c: caseBodies)
+	{
+		m_assembly.setSourceLocation(c.first->location);
+		m_assembly.appendLabel(c.second);
+		(*this)(c.first->body);
+		// Avoid useless "jump to next" for the last case.
+		if (--numCases > 0)
+		{
+			m_assembly.setSourceLocation(c.first->location);
+			m_assembly.appendJumpTo(end);
+		}
+	}
+
+	m_assembly.setSourceLocation(_switch.location);
+	m_assembly.appendLabel(end);
+	m_assembly.appendInstruction(solidity::Instruction::POP);
+	checkStackHeight(&_switch);
+}
+
+void CodeTransform::operator()(FunctionDefinition const& _function)
+{
+	solAssert(m_scope, "");
+	solAssert(m_scope->identifiers.count(_function.name), "");
+	Scope::Function& function = boost::get<Scope::Function>(m_scope->identifiers.at(_function.name));
+	assignLabelIdIfUnset(function.id);
+
+	int const localStackAdjustment = m_evm15 ? 0 : 1;
+	int height = localStackAdjustment;
+	solAssert(m_info.scopes.at(&_function.body), "");
+	Scope* varScope = m_info.scopes.at(m_info.virtualBlocks.at(&_function).get()).get();
+	solAssert(varScope, "");
+	for (auto const& v: _function.arguments | boost::adaptors::reversed)
+	{
+		auto& var = boost::get<Scope::Variable>(varScope->identifiers.at(v.name));
+		var.stackHeight = height++;
+		var.active = true;
+	}
+
+	m_assembly.setSourceLocation(_function.location);
+	int stackHeightBefore = m_assembly.stackHeight();
+	AbstractAssembly::LabelID afterFunction = m_assembly.newLabelId();
+
+	if (m_evm15)
+	{
+		m_assembly.appendJumpTo(afterFunction, -stackHeightBefore);
+		m_assembly.appendBeginsub(*function.id, _function.arguments.size());
+	}
+	else
+	{
+		m_assembly.appendJumpTo(afterFunction, -stackHeightBefore + height);
+		m_assembly.appendLabel(*function.id);
+	}
+	m_stackAdjustment += localStackAdjustment;
+
+	for (auto const& v: _function.returns)
+	{
+		auto& var = boost::get<Scope::Variable>(varScope->identifiers.at(v.name));
+		var.stackHeight = height++;
+		var.active = true;
+		// Preset stack slots for return variables to zero.
+		m_assembly.appendConstant(u256(0));
+	}
+
+	CodeTransform(m_assembly, m_info, m_evm15, m_identifierAccess, localStackAdjustment)
+		.run(_function.body);
+
+	{
+		// The stack layout here is:
+		// <return label>? <arguments...> <return values...>
+		// But we would like it to be:
+		// <return values...> <return label>?
+		// So we have to append some SWAP and POP instructions.
+
+		// This vector holds the desired target positions of all stack slots and is
+		// modified parallel to the actual stack.
+		vector<int> stackLayout;
+		if (!m_evm15)
+			stackLayout.push_back(_function.returns.size()); // Move return label to the top
+		stackLayout += vector<int>(_function.arguments.size(), -1); // discard all arguments
+		for (size_t i = 0; i < _function.returns.size(); ++i)
+			stackLayout.push_back(i); // Move return values down, but keep order.
+
+		solAssert(stackLayout.size() <= 17, "Stack too deep");
+		while (!stackLayout.empty() && stackLayout.back() != int(stackLayout.size() - 1))
+			if (stackLayout.back() < 0)
+			{
+				m_assembly.appendInstruction(solidity::Instruction::POP);
+				stackLayout.pop_back();
+			}
+			else
+			{
+				m_assembly.appendInstruction(swapInstruction(stackLayout.size() - stackLayout.back() - 1));
+				swap(stackLayout[stackLayout.back()], stackLayout.back());
+			}
+		for (int i = 0; size_t(i) < stackLayout.size(); ++i)
+			solAssert(i == stackLayout[i], "Error reshuffling stack.");
+	}
+
+	if (m_evm15)
+		m_assembly.appendReturnsub(_function.returns.size(), stackHeightBefore);
+	else
+		m_assembly.appendJump(stackHeightBefore - _function.returns.size());
+	m_stackAdjustment -= localStackAdjustment;
+	m_assembly.appendLabel(afterFunction);
+	checkStackHeight(&_function);
+}
+
+void CodeTransform::operator()(Block const& _block)
+{
+	CodeTransform(m_assembly, m_info, m_evm15, m_identifierAccess, m_stackAdjustment).run(_block);
+}
+
+AbstractAssembly::LabelID CodeTransform::labelFromIdentifier(Identifier const& _identifier)
+{
+	AbstractAssembly::LabelID label = AbstractAssembly::LabelID(-1);
+	if (!m_scope->lookup(_identifier.name, Scope::NonconstVisitor(
+		[=](Scope::Variable&) { solAssert(false, "Expected label"); },
+		[&](Scope::Label& _label)
+		{
+			assignLabelIdIfUnset(_label.id);
+			label = *_label.id;
+		},
+		[=](Scope::Function&) { solAssert(false, "Expected label"); }
+	)))
+	{
+		solAssert(false, "Identifier not found.");
+	}
+	return label;
+}
+
+void CodeTransform::visitExpression(Statement const& _expression)
+{
+	int height = m_assembly.stackHeight();
+	boost::apply_visitor(*this, _expression);
+	expectDeposit(1, height);
+}
+
+void CodeTransform::generateAssignment(Identifier const& _variableName)
+{
+	solAssert(m_scope, "");
+	auto var = m_scope->lookup(_variableName.name);
+	if (var)
+	{
+		Scope::Variable const& _var = boost::get<Scope::Variable>(*var);
+		if (int heightDiff = variableHeightDiff(_var, true))
+			m_assembly.appendInstruction(solidity::swapInstruction(heightDiff - 1));
+		m_assembly.appendInstruction(solidity::Instruction::POP);
+	}
+	else
+	{
+		solAssert(
+			m_identifierAccess.generateCode,
+			"Identifier not found and no external access available."
+		);
+		m_identifierAccess.generateCode(_variableName, IdentifierContext::LValue, m_assembly);
+	}
+}
+
+int CodeTransform::variableHeightDiff(solidity::assembly::Scope::Variable const& _var, bool _forSwap)
+{
+	int heightDiff = m_assembly.stackHeight() - _var.stackHeight;
+	if (heightDiff <= (_forSwap ? 1 : 0) || heightDiff > (_forSwap ? 17 : 16))
+	{
+		solUnimplemented(
+			"Variable inaccessible, too deep inside stack (" + boost::lexical_cast<string>(heightDiff) + ")"
+		);
+		return 0;
+	}
+	else
+		return heightDiff;
+}
+
+void CodeTransform::expectDeposit(int _deposit, int _oldHeight)
+{
+	solAssert(m_assembly.stackHeight() == _oldHeight + _deposit, "Invalid stack deposit.");
+}
+
+void CodeTransform::checkStackHeight(void const* _astElement)
+{
+	solAssert(m_info.stackHeightInfo.count(_astElement), "Stack height for AST element not found.");
+	solAssert(
+		m_info.stackHeightInfo.at(_astElement) == m_assembly.stackHeight() - m_stackAdjustment,
+		"Stack height mismatch between analysis and code generation phase: Analysis: " +
+		to_string(m_info.stackHeightInfo.at(_astElement)) +
+		" code gen: " +
+		to_string(m_assembly.stackHeight() - m_stackAdjustment)
+	);
+}
+
+void CodeTransform::assignLabelIdIfUnset(boost::optional<AbstractAssembly::LabelID>& _labelId)
+{
+	if (!_labelId)
+		_labelId.reset(m_assembly.newLabelId());
+}
diff --git a/libjulia/backends/evm/EVMCodeTransform.h b/libjulia/backends/evm/EVMCodeTransform.h
index 64e76246..6031d1a8 100644
--- a/libjulia/backends/evm/EVMCodeTransform.h
+++ b/libjulia/backends/evm/EVMCodeTransform.h
@@ -18,12 +18,13 @@
  * Common code generator for translating Julia / inline assembly to EVM and EVM1.5.
  */
 
-#include <libjulia/backends/evm/AbstractAssembly.h>
+#include <libjulia/backends/evm/EVMAssembly.h>
 
 #include <libsolidity/inlineasm/AsmStack.h>
 #include <libsolidity/inlineasm/AsmScope.h>
 
 #include <boost/variant.hpp>
+#include <boost/optional.hpp>
 
 namespace dev
 {
@@ -45,37 +46,46 @@ struct StackAssignment;
 struct FunctionDefinition;
 struct FunctionCall;
 
+using Statement = boost::variant<Instruction, Literal, Label, StackAssignment, Identifier, Assignment, FunctionCall, FunctionalInstruction, VariableDeclaration, FunctionDefinition, Switch, Block>;
+
 struct AsmAnalysisInfo;
 }
 }
 namespace julia
 {
+class EVMAssembly;
 
 class CodeTransform: public boost::static_visitor<>
 {
 public:
-	/// Create the code transformer which appends assembly to _assembly as a side-effect
-	/// of its creation.
+	/// Create the code transformer.
 	/// @param _identifierAccess used to resolve identifiers external to the inline assembly
 	CodeTransform(
-		solidity::ErrorReporter& _errorReporter,
 		julia::AbstractAssembly& _assembly,
-		solidity::assembly::Block const& _block,
 		solidity::assembly::AsmAnalysisInfo& _analysisInfo,
+		bool _evm15 = false,
 		ExternalIdentifierAccess const& _identifierAccess = ExternalIdentifierAccess()
-	): CodeTransform(_errorReporter, _assembly, _block, _analysisInfo, _identifierAccess, _assembly.stackHeight())
+	): CodeTransform(_assembly, _analysisInfo, _evm15, _identifierAccess, _assembly.stackHeight())
 	{
 	}
 
-private:
+	/// Processes the block and appends the resulting code to the assembly.
+	void run(solidity::assembly::Block const& _block);
+
+protected:
 	CodeTransform(
-		solidity::ErrorReporter& _errorReporter,
 		julia::AbstractAssembly& _assembly,
-		solidity::assembly::Block const& _block,
 		solidity::assembly::AsmAnalysisInfo& _analysisInfo,
+		bool _evm15,
 		ExternalIdentifierAccess const& _identifierAccess,
-		int _initialStackHeight
-	);
+		int _stackAdjustment
+	):
+		m_assembly(_assembly),
+		m_info(_analysisInfo),
+		m_evm15(_evm15),
+		m_identifierAccess(_identifierAccess),
+		m_stackAdjustment(_stackAdjustment)
+	{}
 
 public:
 	void operator()(solidity::assembly::Instruction const& _instruction);
@@ -87,31 +97,39 @@ public:
 	void operator()(solidity::assembly::StackAssignment const& _assignment);
 	void operator()(solidity::assembly::Assignment const& _assignment);
 	void operator()(solidity::assembly::VariableDeclaration const& _varDecl);
-	void operator()(solidity::assembly::Block const& _block);
 	void operator()(solidity::assembly::Switch const& _switch);
 	void operator()(solidity::assembly::FunctionDefinition const&);
+	void operator()(solidity::assembly::Block const& _block);
 
 private:
-	void generateAssignment(solidity::assembly::Identifier const& _variableName, SourceLocation const& _location);
+	AbstractAssembly::LabelID labelFromIdentifier(solidity::assembly::Identifier const& _identifier);
+	/// Generates code for an expression that is supposed to return a single value.
+	void visitExpression(solidity::assembly::Statement const& _expression);
+
+	void generateAssignment(solidity::assembly::Identifier const& _variableName);
 
-	/// Determines the stack height difference to the given variables. Automatically generates
-	/// errors if it is not yet in scope or the height difference is too large. Returns 0 on
-	/// errors and the (positive) stack height difference otherwise.
-	int variableHeightDiff(solidity::assembly::Scope::Variable const& _var, SourceLocation const& _location, bool _forSwap);
+	/// Determines the stack height difference to the given variables. Throws
+	/// if it is not yet in scope or the height difference is too large. Returns
+	/// the (positive) stack height difference otherwise.
+	int variableHeightDiff(solidity::assembly::Scope::Variable const& _var, bool _forSwap);
 
 	void expectDeposit(int _deposit, int _oldHeight);
 
 	void checkStackHeight(void const* _astElement);
 
-	/// Assigns the label's id to a value taken from eth::Assembly if it has not yet been set.
-	void assignLabelIdIfUnset(solidity::assembly::Scope::Label& _label);
+	/// Assigns the label's or function's id to a value taken from eth::Assembly if it has not yet been set.
+	void assignLabelIdIfUnset(boost::optional<AbstractAssembly::LabelID>& _labelId);
 
-	solidity::ErrorReporter& m_errorReporter;
 	julia::AbstractAssembly& m_assembly;
 	solidity::assembly::AsmAnalysisInfo& m_info;
-	solidity::assembly::Scope& m_scope;
+	solidity::assembly::Scope* m_scope = nullptr;
+	bool m_evm15 = false;
 	ExternalIdentifierAccess m_identifierAccess;
-	int const m_initialStackHeight;
+	/// Adjustment between the stack height as determined during the analysis phase
+	/// and the stack height in the assembly. This is caused by an initial stack being present
+	/// for inline assembly and different stack heights depending on the EVM backend used
+	/// (EVM 1.0 or 1.5).
+	int m_stackAdjustment = 0;
 };
 
 }