solidity/libsolidity/ExpressionCompiler.cpp

/*
	This file is part of cpp-ethereum.

	cpp-ethereum 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.

	cpp-ethereum 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 cpp-ethereum.  If not, see <http://www.gnu.org/licenses/>.
*/
/**
 * @author Christian <c@ethdev.com>
 * @date 2014
 * Solidity AST to EVM bytecode compiler for expressions.
 */

#include <utility>
#include <numeric>
#include <boost/range/adaptor/reversed.hpp>
#include <libevmcore/Params.h>
#include <libdevcore/Common.h>
#include <libdevcore/SHA3.h>
#include <libsolidity/AST.h>
#include <libsolidity/ExpressionCompiler.h>
#include <libsolidity/CompilerContext.h>
#include <libsolidity/CompilerUtils.h>
#include <libsolidity/LValue.h>

using namespace std;

namespace dev
{
namespace solidity
{

void ExpressionCompiler::compile(Expression const& _expression)
{
	_expression.accept(*this);
}

void ExpressionCompiler::appendStateVariableInitialization(VariableDeclaration const& _varDecl)
{
	if (!_varDecl.getValue())
		return;
	TypePointer type = _varDecl.getValue()->getType();
	solAssert(!!type, "Type information not available.");
	CompilerContext::LocationSetter locationSetter(m_context, _varDecl);
	_varDecl.getValue()->accept(*this);

	if (_varDecl.getType()->dataStoredIn(DataLocation::Storage))
	{
		// reference type, only convert value to mobile type and do final conversion in storeValue.
		utils().convertType(*type, *type->mobileType());
		type = type->mobileType();
	}
	else
	{
		utils().convertType(*type, *_varDecl.getType());
		type = _varDecl.getType();
	}
	StorageItem(m_context, _varDecl).storeValue(*type, _varDecl.getLocation(), true);
}

void ExpressionCompiler::appendConstStateVariableAccessor(VariableDeclaration const& _varDecl)
{
	solAssert(_varDecl.isConstant(), "");
	_varDecl.getValue()->accept(*this);

	// append return
	m_context << eth::dupInstruction(_varDecl.getType()->getSizeOnStack() + 1);
	m_context.appendJump(eth::AssemblyItem::JumpType::OutOfFunction);
}

void ExpressionCompiler::appendStateVariableAccessor(VariableDeclaration const& _varDecl)
{
	solAssert(!_varDecl.isConstant(), "");
	CompilerContext::LocationSetter locationSetter(m_context, _varDecl);
	FunctionType accessorType(_varDecl);

	TypePointers const& paramTypes = accessorType.getParameterTypes();

	// retrieve the position of the variable
	auto const& location = m_context.getStorageLocationOfVariable(_varDecl);
	m_context << location.first << u256(location.second);

	TypePointer returnType = _varDecl.getType();

	for (size_t i = 0; i < paramTypes.size(); ++i)
	{
		if (auto mappingType = dynamic_cast<MappingType const*>(returnType.get()))
		{
			solAssert(CompilerUtils::freeMemoryPointer >= 0x40, "");
			solAssert(
				!paramTypes[i]->isDynamicallySized(),
				"Accessors for mapping with dynamically-sized keys not yet implemented."
			);
			// pop offset
			m_context << eth::Instruction::POP;
			// move storage offset to memory.
			utils().storeInMemory(32);
			// move key to memory.
			utils().copyToStackTop(paramTypes.size() - i, 1);
			utils().storeInMemory(0);
			m_context << u256(64) << u256(0) << eth::Instruction::SHA3;
			// push offset
			m_context << u256(0);
			returnType = mappingType->getValueType();
		}
		else if (auto arrayType = dynamic_cast<ArrayType const*>(returnType.get()))
		{
			// pop offset
			m_context << eth::Instruction::POP;
			utils().copyToStackTop(paramTypes.size() - i + 1, 1);
			ArrayUtils(m_context).accessIndex(*arrayType);
			returnType = arrayType->getBaseType();
		}
		else
			solAssert(false, "Index access is allowed only for \"mapping\" and \"array\" types.");
	}
	// remove index arguments.
	if (paramTypes.size() == 1)
		m_context << eth::Instruction::SWAP2 << eth::Instruction::POP << eth::Instruction::SWAP1;
	else if (paramTypes.size() >= 2)
	{
		m_context << eth::swapInstruction(paramTypes.size());
		m_context << eth::Instruction::POP;
		m_context << eth::swapInstruction(paramTypes.size());
		utils().popStackSlots(paramTypes.size() - 1);
	}
	unsigned retSizeOnStack = 0;
	solAssert(accessorType.getReturnParameterTypes().size() >= 1, "");
	auto const& returnTypes = accessorType.getReturnParameterTypes();
	if (StructType const* structType = dynamic_cast<StructType const*>(returnType.get()))
	{
		// remove offset
		m_context << eth::Instruction::POP;
		auto const& names = accessorType.getReturnParameterNames();
		// struct
		for (size_t i = 0; i < names.size(); ++i)
		{
			if (returnTypes[i]->getCategory() == Type::Category::Mapping)
				continue;
			if (auto arrayType = dynamic_cast<ArrayType const*>(returnTypes[i].get()))
				if (!arrayType->isByteArray())
					continue;
			pair<u256, unsigned> const& offsets = structType->getStorageOffsetsOfMember(names[i]);
			m_context << eth::Instruction::DUP1 << u256(offsets.first) << eth::Instruction::ADD << u256(offsets.second);
			TypePointer memberType = structType->getMemberType(names[i]);
			StorageItem(m_context, *memberType).retrieveValue(SourceLocation(), true);
			utils().convertType(*memberType, *returnTypes[i]);
			utils().moveToStackTop(returnTypes[i]->getSizeOnStack());
			retSizeOnStack += returnTypes[i]->getSizeOnStack();
		}
		// remove slot
		m_context << eth::Instruction::POP;
	}
	else
	{
		// simple value or array
		solAssert(returnTypes.size() == 1, "");
		StorageItem(m_context, *returnType).retrieveValue(SourceLocation(), true);
		utils().convertType(*returnType, *returnTypes.front());
		retSizeOnStack = returnTypes.front()->getSizeOnStack();
	}
	solAssert(retSizeOnStack == utils().getSizeOnStack(returnTypes), "");
	solAssert(retSizeOnStack <= 15, "Stack is too deep.");
	m_context << eth::dupInstruction(retSizeOnStack + 1);
	m_context.appendJump(eth::AssemblyItem::JumpType::OutOfFunction);
}

bool ExpressionCompiler::visit(Assignment const& _assignment)
{
	CompilerContext::LocationSetter locationSetter(m_context, _assignment);
	_assignment.getRightHandSide().accept(*this);
	TypePointer type = _assignment.getRightHandSide().getType();
	if (!_assignment.getType()->dataStoredIn(DataLocation::Storage))
	{
		utils().convertType(*type, *_assignment.getType());
		type = _assignment.getType();
	}
	else
	{
		utils().convertType(*type, *type->mobileType());
		type = type->mobileType();
	}

	_assignment.getLeftHandSide().accept(*this);
	solAssert(!!m_currentLValue, "LValue not retrieved.");

	Token::Value op = _assignment.getAssignmentOperator();
	if (op != Token::Assign) // compound assignment
	{
		solAssert(_assignment.getType()->isValueType(), "Compound operators not implemented for non-value types.");
		unsigned lvalueSize = m_currentLValue->sizeOnStack();
		unsigned itemSize = _assignment.getType()->getSizeOnStack();
		if (lvalueSize > 0)
		{
			utils().copyToStackTop(lvalueSize + itemSize, itemSize);
			utils().copyToStackTop(itemSize + lvalueSize, lvalueSize);
			// value lvalue_ref value lvalue_ref
		}
		m_currentLValue->retrieveValue(_assignment.getLocation(), true);
		appendOrdinaryBinaryOperatorCode(Token::AssignmentToBinaryOp(op), *_assignment.getType());
		if (lvalueSize > 0)
		{
			solAssert(itemSize + lvalueSize <= 16, "Stack too deep, try removing local variables.");
			// value [lvalue_ref] updated_value
			for (unsigned i = 0; i < itemSize; ++i)
				m_context << eth::swapInstruction(itemSize + lvalueSize) << eth::Instruction::POP;
		}
	}
	m_currentLValue->storeValue(*type, _assignment.getLocation());
	m_currentLValue.reset();
	return false;
}

bool ExpressionCompiler::visit(UnaryOperation const& _unaryOperation)
{
	CompilerContext::LocationSetter locationSetter(m_context, _unaryOperation);
	//@todo type checking and creating code for an operator should be in the same place:
	// the operator should know how to convert itself and to which types it applies, so
	// put this code together with "Type::acceptsBinary/UnaryOperator" into a class that
	// represents the operator
	if (_unaryOperation.getType()->getCategory() == Type::Category::IntegerConstant)
	{
		m_context << _unaryOperation.getType()->literalValue(nullptr);
		return false;
	}

	_unaryOperation.getSubExpression().accept(*this);

	switch (_unaryOperation.getOperator())
	{
	case Token::Not: // !
		m_context << eth::Instruction::ISZERO;
		break;
	case Token::BitNot: // ~
		m_context << eth::Instruction::NOT;
		break;
	case Token::After: // after
		m_context << eth::Instruction::TIMESTAMP << eth::Instruction::ADD;
		break;
	case Token::Delete: // delete
		solAssert(!!m_currentLValue, "LValue not retrieved.");
		m_currentLValue->setToZero(_unaryOperation.getLocation());
		m_currentLValue.reset();
		break;
	case Token::Inc: // ++ (pre- or postfix)
	case Token::Dec: // -- (pre- or postfix)
		solAssert(!!m_currentLValue, "LValue not retrieved.");
		m_currentLValue->retrieveValue(_unaryOperation.getLocation());
		if (!_unaryOperation.isPrefixOperation())
		{
			// store value for later
			solAssert(_unaryOperation.getType()->getSizeOnStack() == 1, "Stack size != 1 not implemented.");
			m_context << eth::Instruction::DUP1;
			if (m_currentLValue->sizeOnStack() > 0)
				for (unsigned i = 1 + m_currentLValue->sizeOnStack(); i > 0; --i)
					m_context << eth::swapInstruction(i);
		}
		m_context << u256(1);
		if (_unaryOperation.getOperator() == Token::Inc)
			m_context << eth::Instruction::ADD;
		else
			m_context << eth::Instruction::SWAP1 << eth::Instruction::SUB;
		// Stack for prefix: [ref...] (*ref)+-1
		// Stack for postfix: *ref [ref...] (*ref)+-1
		for (unsigned i = m_currentLValue->sizeOnStack(); i > 0; --i)
			m_context << eth::swapInstruction(i);
		m_currentLValue->storeValue(
			*_unaryOperation.getType(), _unaryOperation.getLocation(),
			!_unaryOperation.isPrefixOperation());
		m_currentLValue.reset();
		break;
	case Token::Add: // +
		// unary add, so basically no-op
		break;
	case Token::Sub: // -
		m_context << u256(0) << eth::Instruction::SUB;
		break;
	default:
		BOOST_THROW_EXCEPTION(InternalCompilerError() << errinfo_comment("Invalid unary operator: " +
																		 string(Token::toString(_unaryOperation.getOperator()))));
	}
	return false;
}

bool ExpressionCompiler::visit(BinaryOperation const& _binaryOperation)
{
	CompilerContext::LocationSetter locationSetter(m_context, _binaryOperation);
	Expression const& leftExpression = _binaryOperation.getLeftExpression();
	Expression const& rightExpression = _binaryOperation.getRightExpression();
	Type const& commonType = _binaryOperation.getCommonType();
	Token::Value const c_op = _binaryOperation.getOperator();

	if (c_op == Token::And || c_op == Token::Or) // special case: short-circuiting
		appendAndOrOperatorCode(_binaryOperation);
	else if (commonType.getCategory() == Type::Category::IntegerConstant)
		m_context << commonType.literalValue(nullptr);
	else
	{
		bool cleanupNeeded = commonType.getCategory() == Type::Category::Integer &&
			(Token::isCompareOp(c_op) || c_op == Token::Div || c_op == Token::Mod);

		// for commutative operators, push the literal as late as possible to allow improved optimization
		auto isLiteral = [](Expression const& _e)
		{
			return dynamic_cast<Literal const*>(&_e) || _e.getType()->getCategory() == Type::Category::IntegerConstant;
		};
		bool swap = m_optimize && Token::isCommutativeOp(c_op) && isLiteral(rightExpression) && !isLiteral(leftExpression);
		if (swap)
		{
			leftExpression.accept(*this);
			utils().convertType(*leftExpression.getType(), commonType, cleanupNeeded);
			rightExpression.accept(*this);
			utils().convertType(*rightExpression.getType(), commonType, cleanupNeeded);
		}
		else
		{
			rightExpression.accept(*this);
			utils().convertType(*rightExpression.getType(), commonType, cleanupNeeded);
			leftExpression.accept(*this);
			utils().convertType(*leftExpression.getType(), commonType, cleanupNeeded);
		}
		if (Token::isCompareOp(c_op))
			appendCompareOperatorCode(c_op, commonType);
		else
			appendOrdinaryBinaryOperatorCode(c_op, commonType);
	}

	// do not visit the child nodes, we already did that explicitly
	return false;
}

bool ExpressionCompiler::visit(FunctionCall const& _functionCall)
{
	CompilerContext::LocationSetter locationSetter(m_context, _functionCall);
	using Location = FunctionType::Location;
	if (_functionCall.isTypeConversion())
	{
		solAssert(_functionCall.getArguments().size() == 1, "");
		solAssert(_functionCall.getNames().empty(), "");
		Expression const& firstArgument = *_functionCall.getArguments().front();
		firstArgument.accept(*this);
		utils().convertType(*firstArgument.getType(), *_functionCall.getType());
		return false;
	}

	FunctionTypePointer functionType;
	if (_functionCall.isStructConstructorCall())
	{
		auto const& type = dynamic_cast<TypeType const&>(*_functionCall.getExpression().getType());
		auto const& structType = dynamic_cast<StructType const&>(*type.getActualType());
		functionType = structType.constructorType();
	}
	else
		functionType = dynamic_pointer_cast<FunctionType const>(_functionCall.getExpression().getType());

	TypePointers const& parameterTypes = functionType->getParameterTypes();
	vector<ASTPointer<Expression const>> const& callArguments = _functionCall.getArguments();
	vector<ASTPointer<ASTString>> const& callArgumentNames = _functionCall.getNames();
	if (!functionType->takesArbitraryParameters())
		solAssert(callArguments.size() == parameterTypes.size(), "");

	vector<ASTPointer<Expression const>> arguments;
	if (callArgumentNames.empty())
		// normal arguments
		arguments = callArguments;
	else
		// named arguments
		for (auto const& parameterName: functionType->getParameterNames())
		{
			bool found = false;
			for (size_t j = 0; j < callArgumentNames.size() && !found; j++)
				if ((found = (parameterName == *callArgumentNames[j])))
					// we found the actual parameter position
					arguments.push_back(callArguments[j]);
			solAssert(found, "");
		}

	if (_functionCall.isStructConstructorCall())
	{
		TypeType const& type = dynamic_cast<TypeType const&>(*_functionCall.getExpression().getType());
		auto const& structType = dynamic_cast<StructType const&>(*type.getActualType());

		m_context << u256(max(32u, structType.getCalldataEncodedSize(true)));
		utils().allocateMemory();
		m_context << eth::Instruction::DUP1;

		for (unsigned i = 0; i < arguments.size(); ++i)
		{
			arguments[i]->accept(*this);
			utils().convertType(*arguments[i]->getType(), *functionType->getParameterTypes()[i]);
			utils().storeInMemoryDynamic(*functionType->getParameterTypes()[i]);
		}
		m_context << eth::Instruction::POP;
	}
	else
	{
		FunctionType const& function = *functionType;
		switch (function.getLocation())
		{
		case Location::Internal:
		{
			// Calling convention: Caller pushes return address and arguments
			// Callee removes them and pushes return values

			eth::AssemblyItem returnLabel = m_context.pushNewTag();
			for (unsigned i = 0; i < arguments.size(); ++i)
			{
				arguments[i]->accept(*this);
				utils().convertType(*arguments[i]->getType(), *function.getParameterTypes()[i]);
			}
			_functionCall.getExpression().accept(*this);

			m_context.appendJump(eth::AssemblyItem::JumpType::IntoFunction);
			m_context << returnLabel;

			unsigned returnParametersSize = CompilerUtils::getSizeOnStack(function.getReturnParameterTypes());
			// callee adds return parameters, but removes arguments and return label
			m_context.adjustStackOffset(returnParametersSize - CompilerUtils::getSizeOnStack(function.getParameterTypes()) - 1);

			// @todo for now, the return value of a function is its first return value, so remove
			// all others
			for (unsigned i = 1; i < function.getReturnParameterTypes().size(); ++i)
				utils().popStackElement(*function.getReturnParameterTypes()[i]);
			break;
		}
		case Location::External:
		case Location::CallCode:
		case Location::Bare:
		case Location::BareCallCode:
			_functionCall.getExpression().accept(*this);
			appendExternalFunctionCall(function, arguments);
			break;
		case Location::Creation:
		{
			_functionCall.getExpression().accept(*this);
			solAssert(!function.gasSet(), "Gas limit set for contract creation.");
			solAssert(function.getReturnParameterTypes().size() == 1, "");
			TypePointers argumentTypes;
			for (auto const& arg: arguments)
			{
				arg->accept(*this);
				argumentTypes.push_back(arg->getType());
			}
			ContractDefinition const& contract = dynamic_cast<ContractType const&>(
							*function.getReturnParameterTypes().front()).getContractDefinition();
			// copy the contract's code into memory
			bytes const& bytecode = m_context.getCompiledContract(contract);
			utils().fetchFreeMemoryPointer();
			m_context << u256(bytecode.size()) << eth::Instruction::DUP1;
			//@todo could be done by actually appending the Assembly, but then we probably need to compile
			// multiple times. Will revisit once external fuctions are inlined.
			m_context.appendData(bytecode);
			m_context << eth::Instruction::DUP4 << eth::Instruction::CODECOPY;

			m_context << eth::Instruction::ADD;
			utils().encodeToMemory(argumentTypes, function.getParameterTypes());
			// now on stack: memory_end_ptr
			// need: size, offset, endowment
			utils().toSizeAfterFreeMemoryPointer();
			if (function.valueSet())
				m_context << eth::dupInstruction(3);
			else
				m_context << u256(0);
			m_context << eth::Instruction::CREATE;
			if (function.valueSet())
				m_context << eth::swapInstruction(1) << eth::Instruction::POP;
			break;
		}
		case Location::SetGas:
		{
			// stack layout: contract_address function_id [gas] [value]
			_functionCall.getExpression().accept(*this);

			arguments.front()->accept(*this);
			utils().convertType(*arguments.front()->getType(), IntegerType(256), true);
			// Note that function is not the original function, but the ".gas" function.
			// Its values of gasSet and valueSet is equal to the original function's though.
			unsigned stackDepth = (function.gasSet() ? 1 : 0) + (function.valueSet() ? 1 : 0);
			if (stackDepth > 0)
				m_context << eth::swapInstruction(stackDepth);
			if (function.gasSet())
				m_context << eth::Instruction::POP;
			break;
		}
		case Location::SetValue:
			// stack layout: contract_address function_id [gas] [value]
			_functionCall.getExpression().accept(*this);
			// Note that function is not the original function, but the ".value" function.
			// Its values of gasSet and valueSet is equal to the original function's though.
			if (function.valueSet())
				m_context << eth::Instruction::POP;
			arguments.front()->accept(*this);
			break;
		case Location::Send:
			_functionCall.getExpression().accept(*this);
			m_context << u256(0); // do not send gas (there still is the stipend)
			arguments.front()->accept(*this);
			utils().convertType(
				*arguments.front()->getType(),
				*function.getParameterTypes().front(), true
			);
			appendExternalFunctionCall(
				FunctionType(
					TypePointers{},
					TypePointers{},
					strings(),
					strings(),
					Location::Bare,
					false,
					nullptr,
					true,
					true
				),
				{}
			);
			break;
		case Location::Suicide:
			arguments.front()->accept(*this);
			utils().convertType(*arguments.front()->getType(), *function.getParameterTypes().front(), true);
			m_context << eth::Instruction::SUICIDE;
			break;
		case Location::SHA3:
		{
			TypePointers argumentTypes;
			for (auto const& arg: arguments)
			{
				arg->accept(*this);
				argumentTypes.push_back(arg->getType());
			}
			utils().fetchFreeMemoryPointer();
			utils().encodeToMemory(argumentTypes, TypePointers(), function.padArguments(), true);
			utils().toSizeAfterFreeMemoryPointer();
			m_context << eth::Instruction::SHA3;
			break;
		}
		case Location::Log0:
		case Location::Log1:
		case Location::Log2:
		case Location::Log3:
		case Location::Log4:
		{
			unsigned logNumber = int(function.getLocation()) - int(Location::Log0);
			for (unsigned arg = logNumber; arg > 0; --arg)
			{
				arguments[arg]->accept(*this);
				utils().convertType(*arguments[arg]->getType(), *function.getParameterTypes()[arg], true);
			}
			arguments.front()->accept(*this);
			utils().fetchFreeMemoryPointer();
			utils().encodeToMemory(
				{arguments.front()->getType()},
				{function.getParameterTypes().front()},
				false,
				true);
			utils().toSizeAfterFreeMemoryPointer();
			m_context << eth::logInstruction(logNumber);
			break;
		}
		case Location::Event:
		{
			_functionCall.getExpression().accept(*this);
			auto const& event = dynamic_cast<EventDefinition const&>(function.getDeclaration());
			unsigned numIndexed = 0;
			// All indexed arguments go to the stack
			for (unsigned arg = arguments.size(); arg > 0; --arg)
				if (event.getParameters()[arg - 1]->isIndexed())
				{
					++numIndexed;
					arguments[arg - 1]->accept(*this);
					utils().convertType(
						*arguments[arg - 1]->getType(),
						*function.getParameterTypes()[arg - 1],
						true
					);
				}
			if (!event.isAnonymous())
			{
				m_context << u256(h256::Arith(dev::sha3(function.externalSignature(event.getName()))));
				++numIndexed;
			}
			solAssert(numIndexed <= 4, "Too many indexed arguments.");
			// Copy all non-indexed arguments to memory (data)
			// Memory position is only a hack and should be removed once we have free memory pointer.
			TypePointers nonIndexedArgTypes;
			TypePointers nonIndexedParamTypes;
			for (unsigned arg = 0; arg < arguments.size(); ++arg)
				if (!event.getParameters()[arg]->isIndexed())
				{
					arguments[arg]->accept(*this);
					nonIndexedArgTypes.push_back(arguments[arg]->getType());
					nonIndexedParamTypes.push_back(function.getParameterTypes()[arg]);
				}
			utils().fetchFreeMemoryPointer();
			utils().encodeToMemory(nonIndexedArgTypes, nonIndexedParamTypes);
			// need: topic1 ... topicn memsize memstart
			utils().toSizeAfterFreeMemoryPointer();
			m_context << eth::logInstruction(numIndexed);
			break;
		}
		case Location::BlockHash:
		{
			arguments[0]->accept(*this);
			utils().convertType(*arguments[0]->getType(), *function.getParameterTypes()[0], true);
			m_context << eth::Instruction::BLOCKHASH;
			break;
		}
		case Location::ECRecover:
		case Location::SHA256:
		case Location::RIPEMD160:
		{
			_functionCall.getExpression().accept(*this);
			static const map<Location, u256> contractAddresses{{Location::ECRecover, 1},
															   {Location::SHA256, 2},
															   {Location::RIPEMD160, 3}};
			m_context << contractAddresses.find(function.getLocation())->second;
			for (unsigned i = function.getSizeOnStack(); i > 0; --i)
				m_context << eth::swapInstruction(i);
			appendExternalFunctionCall(function, arguments);
			break;
		}
		default:
			BOOST_THROW_EXCEPTION(InternalCompilerError() << errinfo_comment("Invalid function type."));
		}
	}
	return false;
}

bool ExpressionCompiler::visit(NewExpression const&)
{
	// code is created for the function call (CREATION) only
	return false;
}

void ExpressionCompiler::endVisit(MemberAccess const& _memberAccess)
{
	CompilerContext::LocationSetter locationSetter(m_context, _memberAccess);
	ASTString const& member = _memberAccess.getMemberName();
	switch (_memberAccess.getExpression().getType()->getCategory())
	{
	case Type::Category::Contract:
	{
		bool alsoSearchInteger = false;
		ContractType const& type = dynamic_cast<ContractType const&>(*_memberAccess.getExpression().getType());
		if (type.isSuper())
		{
			solAssert(!!_memberAccess.referencedDeclaration(), "Referenced declaration not resolved.");
			m_context << m_context.getSuperFunctionEntryLabel(
				dynamic_cast<FunctionDefinition const&>(*_memberAccess.referencedDeclaration()),
				type.getContractDefinition()
			).pushTag();
		}
		else
		{
			// ordinary contract type
			if (Declaration const* declaration = _memberAccess.referencedDeclaration())
			{
				u256 identifier;
				if (auto const* variable = dynamic_cast<VariableDeclaration const*>(declaration))
					identifier = FunctionType(*variable).externalIdentifier();
				else if (auto const* function = dynamic_cast<FunctionDefinition const*>(declaration))
					identifier = FunctionType(*function).externalIdentifier();
				else
					solAssert(false, "Contract member is neither variable nor function.");
				utils().convertType(type, IntegerType(0, IntegerType::Modifier::Address), true);
				m_context << identifier;
			}
			else
				// not found in contract, search in members inherited from address
				alsoSearchInteger = true;
		}
		if (!alsoSearchInteger)
			break;
	}
	case Type::Category::Integer:
		if (member == "balance")
		{
			utils().convertType(
				*_memberAccess.getExpression().getType(),
				IntegerType(0, IntegerType::Modifier::Address),
				true
			);
			m_context << eth::Instruction::BALANCE;
		}
		else if ((set<string>{"send", "call", "callcode"}).count(member))
			utils().convertType(
				*_memberAccess.getExpression().getType(),
				IntegerType(0, IntegerType::Modifier::Address),
				true
			);
		else
			BOOST_THROW_EXCEPTION(InternalCompilerError() << errinfo_comment("Invalid member access to integer."));
		break;
	case Type::Category::Function:
		solAssert(!!_memberAccess.getExpression().getType()->getMemberType(member),
				 "Invalid member access to function.");
		break;
	case Type::Category::Magic:
		// we can ignore the kind of magic and only look at the name of the member
		if (member == "coinbase")
			m_context << eth::Instruction::COINBASE;
		else if (member == "timestamp")
			m_context << eth::Instruction::TIMESTAMP;
		else if (member == "difficulty")
			m_context << eth::Instruction::DIFFICULTY;
		else if (member == "number")
			m_context << eth::Instruction::NUMBER;
		else if (member == "gaslimit")
			m_context << eth::Instruction::GASLIMIT;
		else if (member == "sender")
			m_context << eth::Instruction::CALLER;
		else if (member == "value")
			m_context << eth::Instruction::CALLVALUE;
		else if (member == "origin")
			m_context << eth::Instruction::ORIGIN;
		else if (member == "gas")
			m_context << eth::Instruction::GAS;
		else if (member == "gasprice")
			m_context << eth::Instruction::GASPRICE;
		else if (member == "data")
			m_context << u256(0) << eth::Instruction::CALLDATASIZE;
		else if (member == "sig")
			m_context << u256(0) << eth::Instruction::CALLDATALOAD
				<< (u256(0xffffffff) << (256 - 32)) << eth::Instruction::AND;
		else
			BOOST_THROW_EXCEPTION(InternalCompilerError() << errinfo_comment("Unknown magic member."));
		break;
	case Type::Category::Struct:
	{
		StructType const& type = dynamic_cast<StructType const&>(*_memberAccess.getExpression().getType());
		switch (type.location())
		{
		case DataLocation::Storage:
		{
			pair<u256, unsigned> const& offsets = type.getStorageOffsetsOfMember(member);
			m_context << offsets.first << eth::Instruction::ADD << u256(offsets.second);
			setLValueToStorageItem(_memberAccess);
			break;
		}
		case DataLocation::Memory:
		{
			m_context << type.memoryOffsetOfMember(member) << eth::Instruction::ADD;
			setLValue<MemoryItem>(_memberAccess, *_memberAccess.getType());
			break;
		}
		default:
			solAssert(false, "Illegal data location for struct.");
		}
		break;
	}
	case Type::Category::Enum:
	{
		EnumType const& type = dynamic_cast<EnumType const&>(*_memberAccess.getExpression().getType());
		m_context << type.getMemberValue(_memberAccess.getMemberName());
		break;
	}
	case Type::Category::TypeType:
	{
		TypeType const& type = dynamic_cast<TypeType const&>(*_memberAccess.getExpression().getType());
		solAssert(
			!type.getMembers().membersByName(_memberAccess.getMemberName()).empty(),
			"Invalid member access to " + type.toString(false)
		);

		if (dynamic_cast<ContractType const*>(type.getActualType().get()))
		{
			auto const* function = dynamic_cast<FunctionDefinition const*>(_memberAccess.referencedDeclaration());
			solAssert(!!function, "Function not found in member access");
			m_context << m_context.getFunctionEntryLabel(*function).pushTag();
		}
		else if (auto enumType = dynamic_cast<EnumType const*>(type.getActualType().get()))
			m_context << enumType->getMemberValue(_memberAccess.getMemberName());
		break;
	}
	case Type::Category::Array:
	{
		solAssert(member == "length", "Illegal array member.");
		auto const& type = dynamic_cast<ArrayType const&>(*_memberAccess.getExpression().getType());
		if (!type.isDynamicallySized())
		{
			utils().popStackElement(type);
			m_context << type.getLength();
		}
		else
			switch (type.location())
			{
			case DataLocation::CallData:
				m_context << eth::Instruction::SWAP1 << eth::Instruction::POP;
				break;
			case DataLocation::Storage:
				setLValue<StorageArrayLength>(_memberAccess, type);
				break;
			case DataLocation::Memory:
				m_context << eth::Instruction::MLOAD;
				break;
			}
		break;
	}
	default:
		BOOST_THROW_EXCEPTION(InternalCompilerError() << errinfo_comment("Member access to unknown type."));
	}
}

bool ExpressionCompiler::visit(IndexAccess const& _indexAccess)
{
	CompilerContext::LocationSetter locationSetter(m_context, _indexAccess);
	_indexAccess.getBaseExpression().accept(*this);

	Type const& baseType = *_indexAccess.getBaseExpression().getType();
	if (baseType.getCategory() == Type::Category::Mapping)
	{
		// stack: storage_base_ref
		TypePointer keyType = dynamic_cast<MappingType const&>(baseType).getKeyType();
		solAssert(_indexAccess.getIndexExpression(), "Index expression expected.");
		if (keyType->isDynamicallySized())
		{
			_indexAccess.getIndexExpression()->accept(*this);
			utils().fetchFreeMemoryPointer();
			// stack: base index mem
			// note: the following operations must not allocate memory!
			utils().encodeToMemory(
				TypePointers{_indexAccess.getIndexExpression()->getType()},
				TypePointers{keyType},
				false,
				true
			);
			m_context << eth::Instruction::SWAP1;
			utils().storeInMemoryDynamic(IntegerType(256));
			utils().toSizeAfterFreeMemoryPointer();
		}
		else
		{
			m_context << u256(0); // memory position
			appendExpressionCopyToMemory(*keyType, *_indexAccess.getIndexExpression());
			m_context << eth::Instruction::SWAP1;
			solAssert(CompilerUtils::freeMemoryPointer >= 0x40, "");
			utils().storeInMemoryDynamic(IntegerType(256));
			m_context << u256(0);
		}
		m_context << eth::Instruction::SHA3;
		m_context << u256(0);
		setLValueToStorageItem(_indexAccess);
	}
	else if (baseType.getCategory() == Type::Category::Array)
	{
		ArrayType const& arrayType = dynamic_cast<ArrayType const&>(baseType);
		solAssert(_indexAccess.getIndexExpression(), "Index expression expected.");

		_indexAccess.getIndexExpression()->accept(*this);
		// stack layout: <base_ref> [<length>] <index>
		ArrayUtils(m_context).accessIndex(arrayType);
		switch (arrayType.location())
		{
		case DataLocation::Storage:
			if (arrayType.isByteArray())
			{
				solAssert(!arrayType.isString(), "Index access to string is not allowed.");
				setLValue<StorageByteArrayElement>(_indexAccess);
			}
			else
				setLValueToStorageItem(_indexAccess);
			break;
		case DataLocation::Memory:
			setLValue<MemoryItem>(_indexAccess, *_indexAccess.getType(), !arrayType.isByteArray());
			break;
		case DataLocation::CallData:
			//@todo if we implement this, the value in calldata has to be added to the base offset
			solAssert(!arrayType.getBaseType()->isDynamicallySized(), "Nested arrays not yet implemented.");
			if (arrayType.getBaseType()->isValueType())
				CompilerUtils(m_context).loadFromMemoryDynamic(
					*arrayType.getBaseType(),
					true,
					!arrayType.isByteArray(),
					false
				);
			break;
		}
	}
	else
		solAssert(false, "Index access only allowed for mappings or arrays.");

	return false;
}

void ExpressionCompiler::endVisit(Identifier const& _identifier)
{
	CompilerContext::LocationSetter locationSetter(m_context, _identifier);
	Declaration const* declaration = &_identifier.getReferencedDeclaration();
	if (MagicVariableDeclaration const* magicVar = dynamic_cast<MagicVariableDeclaration const*>(declaration))
	{
		switch (magicVar->getType()->getCategory())
		{
		case Type::Category::Contract:
			// "this" or "super"
			if (!dynamic_cast<ContractType const&>(*magicVar->getType()).isSuper())
				m_context << eth::Instruction::ADDRESS;
			break;
		case Type::Category::Integer:
			// "now"
			m_context << eth::Instruction::TIMESTAMP;
			break;
		default:
			break;
		}
	}
	else if (FunctionDefinition const* functionDef = dynamic_cast<FunctionDefinition const*>(declaration))
		m_context << m_context.getVirtualFunctionEntryLabel(*functionDef).pushTag();
	else if (auto variable = dynamic_cast<VariableDeclaration const*>(declaration))
	{
		if (!variable->isConstant())
			setLValueFromDeclaration(*declaration, _identifier);
		else
			variable->getValue()->accept(*this);
	}
	else if (dynamic_cast<ContractDefinition const*>(declaration))
	{
		// no-op
	}
	else if (dynamic_cast<EventDefinition const*>(declaration))
	{
		// no-op
	}
	else if (dynamic_cast<EnumDefinition const*>(declaration))
	{
		// no-op
	}
	else
	{
		BOOST_THROW_EXCEPTION(InternalCompilerError() << errinfo_comment("Identifier type not expected in expression context."));
	}
}

void ExpressionCompiler::endVisit(Literal const& _literal)
{
	CompilerContext::LocationSetter locationSetter(m_context, _literal);
	TypePointer type = _literal.getType();
	switch (type->getCategory())
	{
	case Type::Category::IntegerConstant:
	case Type::Category::Bool:
		m_context << type->literalValue(&_literal);
		break;
	case Type::Category::StringLiteral:
		break; // will be done during conversion
	default:
		BOOST_THROW_EXCEPTION(InternalCompilerError() << errinfo_comment("Only integer, boolean and string literals implemented for now."));
	}
}

void ExpressionCompiler::appendAndOrOperatorCode(BinaryOperation const& _binaryOperation)
{
	Token::Value const c_op = _binaryOperation.getOperator();
	solAssert(c_op == Token::Or || c_op == Token::And, "");

	_binaryOperation.getLeftExpression().accept(*this);
	m_context << eth::Instruction::DUP1;
	if (c_op == Token::And)
		m_context << eth::Instruction::ISZERO;
	eth::AssemblyItem endLabel = m_context.appendConditionalJump();
	m_context << eth::Instruction::POP;
	_binaryOperation.getRightExpression().accept(*this);
	m_context << endLabel;
}

void ExpressionCompiler::appendCompareOperatorCode(Token::Value _operator, Type const& _type)
{
	if (_operator == Token::Equal || _operator == Token::NotEqual)
	{
		m_context << eth::Instruction::EQ;
		if (_operator == Token::NotEqual)
			m_context << eth::Instruction::ISZERO;
	}
	else
	{
		bool isSigned = false;
		if (auto type = dynamic_cast<IntegerType const*>(&_type))
			isSigned = type->isSigned();

		switch (_operator)
		{
		case Token::GreaterThanOrEqual:
			m_context <<
				(isSigned ? eth::Instruction::SLT : eth::Instruction::LT) <<
				eth::Instruction::ISZERO;
			break;
		case Token::LessThanOrEqual:
			m_context <<
				(isSigned ? eth::Instruction::SGT : eth::Instruction::GT) <<
				eth::Instruction::ISZERO;
			break;
		case Token::GreaterThan:
			m_context << (isSigned ? eth::Instruction::SGT : eth::Instruction::GT);
			break;
		case Token::LessThan:
			m_context << (isSigned ? eth::Instruction::SLT : eth::Instruction::LT);
			break;
		default:
			BOOST_THROW_EXCEPTION(InternalCompilerError() << errinfo_comment("Unknown comparison operator."));
		}
	}
}

void ExpressionCompiler::appendOrdinaryBinaryOperatorCode(Token::Value _operator, Type const& _type)
{
	if (Token::isArithmeticOp(_operator))
		appendArithmeticOperatorCode(_operator, _type);
	else if (Token::isBitOp(_operator))
		appendBitOperatorCode(_operator);
	else if (Token::isShiftOp(_operator))
		appendShiftOperatorCode(_operator);
	else
		BOOST_THROW_EXCEPTION(InternalCompilerError() << errinfo_comment("Unknown binary operator."));
}

void ExpressionCompiler::appendArithmeticOperatorCode(Token::Value _operator, Type const& _type)
{
	IntegerType const& type = dynamic_cast<IntegerType const&>(_type);
	bool const c_isSigned = type.isSigned();

	switch (_operator)
	{
	case Token::Add:
		m_context << eth::Instruction::ADD;
		break;
	case Token::Sub:
		m_context << eth::Instruction::SUB;
		break;
	case Token::Mul:
		m_context << eth::Instruction::MUL;
		break;
	case Token::Div:
		m_context  << (c_isSigned ? eth::Instruction::SDIV : eth::Instruction::DIV);
		break;
	case Token::Mod:
		m_context << (c_isSigned ? eth::Instruction::SMOD : eth::Instruction::MOD);
		break;
	case Token::Exp:
		m_context << eth::Instruction::EXP;
		break;
	default:
		BOOST_THROW_EXCEPTION(InternalCompilerError() << errinfo_comment("Unknown arithmetic operator."));
	}
}

void ExpressionCompiler::appendBitOperatorCode(Token::Value _operator)
{
	switch (_operator)
	{
	case Token::BitOr:
		m_context << eth::Instruction::OR;
		break;
	case Token::BitAnd:
		m_context << eth::Instruction::AND;
		break;
	case Token::BitXor:
		m_context << eth::Instruction::XOR;
		break;
	default:
		BOOST_THROW_EXCEPTION(InternalCompilerError() << errinfo_comment("Unknown bit operator."));
	}
}

void ExpressionCompiler::appendShiftOperatorCode(Token::Value _operator)
{
	BOOST_THROW_EXCEPTION(InternalCompilerError() << errinfo_comment("Shift operators not yet implemented."));
	switch (_operator)
	{
	case Token::SHL:
		break;
	case Token::SAR:
		break;
	default:
		BOOST_THROW_EXCEPTION(InternalCompilerError() << errinfo_comment("Unknown shift operator."));
	}
}

void ExpressionCompiler::appendExternalFunctionCall(
	FunctionType const& _functionType,
	vector<ASTPointer<Expression const>> const& _arguments
)
{
	solAssert(_functionType.takesArbitraryParameters() ||
			  _arguments.size() == _functionType.getParameterTypes().size(), "");

	// Assumed stack content here:
	// <stack top>
	// value [if _functionType.valueSet()]
	// gas [if _functionType.gasSet()]
	// function identifier [unless bare]
	// contract address

	unsigned gasValueSize = (_functionType.gasSet() ? 1 : 0) + (_functionType.valueSet() ? 1 : 0);

	unsigned contractStackPos = m_context.currentToBaseStackOffset(1 + gasValueSize + (_functionType.isBareCall() ? 0 : 1));
	unsigned gasStackPos = m_context.currentToBaseStackOffset(gasValueSize);
	unsigned valueStackPos = m_context.currentToBaseStackOffset(1);

	using FunctionKind = FunctionType::Location;
	FunctionKind funKind = _functionType.getLocation();
	bool returnSuccessCondition = funKind == FunctionKind::Bare || funKind == FunctionKind::BareCallCode;
	bool isCallCode = funKind == FunctionKind::BareCallCode || funKind == FunctionKind::CallCode;

	//@todo only return the first return value for now
	Type const* firstReturnType =
		_functionType.getReturnParameterTypes().empty() ?
		nullptr :
		_functionType.getReturnParameterTypes().front().get();
	unsigned retSize = 0;
	if (returnSuccessCondition)
		retSize = 0; // return value actually is success condition
	else if (firstReturnType)
	{
		retSize = firstReturnType->getCalldataEncodedSize();
		solAssert(retSize > 0, "Unable to return dynamic type from external call.");
	}

	// Evaluate arguments.
	TypePointers argumentTypes;
	bool manualFunctionId =
		(funKind == FunctionKind::Bare || funKind == FunctionKind::BareCallCode) &&
		!_arguments.empty() &&
		_arguments.front()->getType()->mobileType()->getCalldataEncodedSize(false) ==
			CompilerUtils::dataStartOffset;
	if (manualFunctionId)
	{
		// If we have a BareCall or BareCallCode and the first type has exactly 4 bytes, use it as
		// function identifier.
		_arguments.front()->accept(*this);
		utils().convertType(
			*_arguments.front()->getType(),
			IntegerType(8 * CompilerUtils::dataStartOffset),
			true
		);
		for (unsigned i = 0; i < gasValueSize; ++i)
			m_context << eth::swapInstruction(gasValueSize - i);
		gasStackPos++;
		valueStackPos++;
	}
	for (size_t i = manualFunctionId ? 1 : 0; i < _arguments.size(); ++i)
	{
		_arguments[i]->accept(*this);
		argumentTypes.push_back(_arguments[i]->getType());
	}

	// Copy function identifier to memory.
	utils().fetchFreeMemoryPointer();
	if (!_functionType.isBareCall() || manualFunctionId)
	{
		m_context << eth::dupInstruction(2 + gasValueSize + CompilerUtils::getSizeOnStack(argumentTypes));
		utils().storeInMemoryDynamic(IntegerType(8 * CompilerUtils::dataStartOffset), false);
	}
	// If the function takes arbitrary parameters, copy dynamic length data in place.
	// Move argumenst to memory, will not update the free memory pointer (but will update the memory
	// pointer on the stack).
	utils().encodeToMemory(
		argumentTypes,
		_functionType.getParameterTypes(),
		_functionType.padArguments(),
		_functionType.takesArbitraryParameters()
	);

	// Stack now:
	// <stack top>
	// input_memory_end
	// value [if _functionType.valueSet()]
	// gas [if _functionType.gasSet()]
	// function identifier [unless bare]
	// contract address

	// Output data will replace input data.
	// put on stack: <size of output> <memory pos of output> <size of input> <memory pos of input>
	m_context << u256(retSize);
	utils().fetchFreeMemoryPointer();
	m_context << eth::Instruction::DUP1 << eth::Instruction::DUP4 << eth::Instruction::SUB;
	m_context << eth::Instruction::DUP2;

	// CALL arguments: outSize, outOff, inSize, inOff (already present up to here)
	// value, addr, gas (stack top)
	if (_functionType.valueSet())
		m_context << eth::dupInstruction(m_context.baseToCurrentStackOffset(valueStackPos));
	else
		m_context << u256(0);
	m_context << eth::dupInstruction(m_context.baseToCurrentStackOffset(contractStackPos));

	if (_functionType.gasSet())
		m_context << eth::dupInstruction(m_context.baseToCurrentStackOffset(gasStackPos));
	else
	{
		// send all gas except the amount needed to execute "SUB" and "CALL"
		// @todo this retains too much gas for now, needs to be fine-tuned.
		u256 gasNeededByCaller = eth::c_callGas + 10;
		if (_functionType.valueSet())
			gasNeededByCaller += eth::c_callValueTransferGas;
		if (!isCallCode)
			gasNeededByCaller += eth::c_callNewAccountGas; // we never know
		m_context <<
			gasNeededByCaller <<
			eth::Instruction::GAS <<
			eth::Instruction::SUB;
	}
	if (isCallCode)
		m_context << eth::Instruction::CALLCODE;
	else
		m_context << eth::Instruction::CALL;

	unsigned remainsSize =
		2 + // contract address, input_memory_end
		_functionType.valueSet() +
		_functionType.gasSet() +
		(!_functionType.isBareCall() || manualFunctionId);

	if (returnSuccessCondition)
		m_context << eth::swapInstruction(remainsSize);
	else
	{
		//Propagate error condition (if CALL pushes 0 on stack).
		m_context << eth::Instruction::ISZERO;
		m_context.appendConditionalJumpTo(m_context.errorTag());
	}

	utils().popStackSlots(remainsSize);

	if (returnSuccessCondition)
	{
		// already there
	}
	else if (funKind == FunctionKind::RIPEMD160)
	{
		// fix: built-in contract returns right-aligned data
		utils().fetchFreeMemoryPointer();
		utils().loadFromMemoryDynamic(IntegerType(160), false, true, false);
		utils().convertType(IntegerType(160), FixedBytesType(20));
	}
	else if (firstReturnType)
	{
		//@todo manually update free memory pointer if we accept returning memory-stored objects
		utils().fetchFreeMemoryPointer();
		utils().loadFromMemoryDynamic(*firstReturnType, false, true, false);

	}
}

void ExpressionCompiler::appendExpressionCopyToMemory(Type const& _expectedType, Expression const& _expression)
{
	solAssert(_expectedType.isValueType(), "Not implemented for non-value types.");
	_expression.accept(*this);
	utils().convertType(*_expression.getType(), _expectedType, true);
	utils().storeInMemoryDynamic(_expectedType);
}

void ExpressionCompiler::setLValueFromDeclaration(Declaration const& _declaration, Expression const& _expression)
{
	if (m_context.isLocalVariable(&_declaration))
		setLValue<StackVariable>(_expression, _declaration);
	else if (m_context.isStateVariable(&_declaration))
		setLValue<StorageItem>(_expression, _declaration);
	else
		BOOST_THROW_EXCEPTION(InternalCompilerError()
			<< errinfo_sourceLocation(_expression.getLocation())
			<< errinfo_comment("Identifier type not supported or identifier not found."));
}

void ExpressionCompiler::setLValueToStorageItem(Expression const& _expression)
{
	setLValue<StorageItem>(_expression, *_expression.getType());
}

CompilerUtils ExpressionCompiler::utils()
{
	return CompilerUtils(m_context);
}

}
}