VM refactor: check requirements helper function.

Move an instruction requirements checking in VM to a separated helper function.
Instruction execution is now split into two parts what reduces OS stack memory usage.

libevm/VM.cpp

@@ -45,42 +45,12 @@ static array<InstructionMetric, 256> metrics()
 	return s_ret;
 }
 
-bytesConstRef VM::execImpl(u256& io_gas, ExtVMFace& _ext, OnOpFunc const& _onOp)
+void VM::checkRequirements(u256& io_gas, ExtVMFace& _ext, OnOpFunc const& _onOp, Instruction _inst)
-{
-	// Reset leftovers from possible previous run
-	m_curPC = 0;
-	m_jumpDests.clear();
-
-	m_stack.reserve((unsigned)c_stackLimit);
-
-	unique_ptr<CallParameters> callParams;
-
-	static const array<InstructionMetric, 256> c_metrics = metrics();
-
-	auto memNeed = [](u256 _offset, dev::u256 _size) { return _size ? (bigint)_offset + _size : (bigint)0; };
-	auto gasForMem = [](bigint _size) -> bigint
 {
-		bigint s = _size / 32;
+	static const auto c_metrics = metrics();
-		return (bigint)c_memoryGas * s + s * s / c_quadCoeffDiv;
+	auto& metric = c_metrics[static_cast<size_t>(_inst)];
-	};
 
-	if (m_jumpDests.empty())
+	if (metric.gasPriceTier == InvalidTier)
-		for (unsigned i = 0; i < _ext.code.size(); ++i)
-		{
-			if (_ext.code[i] == (byte)Instruction::JUMPDEST)
-				m_jumpDests.push_back(i);
-			else if (_ext.code[i] >= (byte)Instruction::PUSH1 && _ext.code[i] <= (byte)Instruction::PUSH32)
-				i += _ext.code[i] - (unsigned)Instruction::PUSH1 + 1;
-		}
-	u256 nextPC = m_curPC + 1;
-	for (uint64_t steps = 0; true; m_curPC = nextPC, nextPC = m_curPC + 1, ++steps)
-	{
-		// INSTRUCTION...
-		Instruction inst = (Instruction)_ext.getCode(m_curPC);
-		auto metric = c_metrics[(int)inst];
-		int gasPriceTier = metric.gasPriceTier;
-
-		if (gasPriceTier == InvalidTier)
 		BOOST_THROW_EXCEPTION(BadInstruction());
 
 	// FEES...
@@ -96,10 +66,12 @@ bytesConstRef VM::execImpl(u256& io_gas, ExtVMFace& _ext, OnOpFunc const& _onOp)
 	auto onOperation = [&]()
 	{
 		if (_onOp)
-				_onOp(steps, inst, newTempSize > m_temp.size() ? (newTempSize - m_temp.size()) / 32 : bigint(0), runGas, io_gas, this, &_ext);
+			_onOp(m_steps, _inst, newTempSize > m_temp.size() ? (newTempSize - m_temp.size()) / 32 : bigint(0), runGas, io_gas, this, &_ext);
 	};
 
-		switch (inst)
+	auto memNeed = [](u256 _offset, dev::u256 _size) { return _size ? (bigint)_offset + _size : (bigint)0; };
+	
+	switch (_inst)
 	{
 	case Instruction::SSTORE:
 		if (!_ext.store(m_stack.back()) && m_stack[m_stack.size() - 2])
@@ -157,7 +129,7 @@ bytesConstRef VM::execImpl(u256& io_gas, ExtVMFace& _ext, OnOpFunc const& _onOp)
 	case Instruction::LOG3:
 	case Instruction::LOG4:
 	{
-			unsigned n = (unsigned)inst - (unsigned)Instruction::LOG0;
+		unsigned n = (unsigned)_inst - (unsigned)Instruction::LOG0;
 		runGas = c_logGas + c_logTopicGas * n + (bigint)c_logDataGas * m_stack[m_stack.size() - 2];
 		newTempSize = memNeed(m_stack[m_stack.size() - 1], m_stack[m_stack.size() - 2]);
 		break;
@@ -166,7 +138,7 @@ bytesConstRef VM::execImpl(u256& io_gas, ExtVMFace& _ext, OnOpFunc const& _onOp)
 	case Instruction::CALL:
 	case Instruction::CALLCODE:
 		runGas = (bigint)c_callGas + m_stack[m_stack.size() - 1];
-			if (inst != Instruction::CALLCODE && !_ext.exists(asAddress(m_stack[m_stack.size() - 2])))
+		if (_inst != Instruction::CALLCODE && !_ext.exists(asAddress(m_stack[m_stack.size() - 2])))
 			runGas += c_callNewAccountGas;
 		if (m_stack[m_stack.size() - 3] > 0)
 			runGas += c_callValueTransferGas;
@@ -188,6 +160,12 @@ bytesConstRef VM::execImpl(u256& io_gas, ExtVMFace& _ext, OnOpFunc const& _onOp)
 	default:;
 	}
 
+	auto gasForMem = [](bigint _size) -> bigint
+	{
+		bigint s = _size / 32;
+		return (bigint)c_memoryGas * s + s * s / c_quadCoeffDiv;
+	};
+
 	newTempSize = (newTempSize + 31) / 32 * 32;
 	if (newTempSize > m_temp.size())
 		runGas += gasForMem(newTempSize) - gasForMem(m_temp.size());
@@ -202,6 +180,32 @@ bytesConstRef VM::execImpl(u256& io_gas, ExtVMFace& _ext, OnOpFunc const& _onOp)
 
 	if (newTempSize > m_temp.size())
 		m_temp.resize((size_t)newTempSize);
+}
+
+bytesConstRef VM::execImpl(u256& io_gas, ExtVMFace& _ext, OnOpFunc const& _onOp)
+{
+	// Reset leftovers from possible previous run
+	m_curPC = 0;
+	m_jumpDests.clear();
+
+	m_stack.reserve((unsigned)c_stackLimit);
+
+	unique_ptr<CallParameters> callParams;
+
+	if (m_jumpDests.empty())
+		for (unsigned i = 0; i < _ext.code.size(); ++i)
+		{
+			if (_ext.code[i] == (byte)Instruction::JUMPDEST)
+				m_jumpDests.push_back(i);
+			else if (_ext.code[i] >= (byte)Instruction::PUSH1 && _ext.code[i] <= (byte)Instruction::PUSH32)
+				i += _ext.code[i] - (unsigned)Instruction::PUSH1 + 1;
+		}
+	u256 nextPC = m_curPC + 1;
+	for (m_steps = 0; true; m_curPC = nextPC, nextPC = m_curPC + 1, ++m_steps)
+	{
+		// INSTRUCTION...
+		Instruction inst = (Instruction)_ext.getCode(m_curPC);
+		checkRequirements(io_gas, _ext, _onOp, inst);
 
 		// EXECUTE...
 		switch (inst)

libevm/VM.h

@@ -60,10 +60,12 @@ public:
 	u256s const& stack() const { return m_stack; }
 
 private:
+	void checkRequirements(u256& io_gas, ExtVMFace& _ext, OnOpFunc const& _onOp, Instruction _inst);
 	void require(u256 _n, u256 _d) { if (m_stack.size() < _n) { if (m_onFail) m_onFail(); BOOST_THROW_EXCEPTION(StackUnderflow() << RequirementError((bigint)_n, (bigint)m_stack.size())); } if (m_stack.size() - _n + _d > c_stackLimit) { if (m_onFail) m_onFail(); BOOST_THROW_EXCEPTION(OutOfStack() << RequirementError((bigint)(_d - _n), (bigint)m_stack.size())); } }
 	void requireMem(unsigned _n) { if (m_temp.size() < _n) { m_temp.resize(_n); } }
 
 	u256 m_curPC = 0;
+	uint64_t m_steps = 0;
 	bytes m_temp;
 	u256s m_stack;
 	std::vector<uint64_t> m_jumpDests;