From 1b449d357e36c73bcde5394282c343a92ef5024c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Pawe=C5=82=20Bylica?= <pawel.bylica@imapp.pl>
Date: Thu, 29 Jan 2015 16:20:22 +0100
Subject: [PATCH] Fallback to interpreter VM in case of JIT requirements unmet

---
 libevmjit-cpp/JitVM.cpp | 28 ++++++++++++++++------------
 libevmjit-cpp/JitVM.h   |  4 +---
 libevmjit/Common.h      | 24 ++++++++++++++----------
 3 files changed, 31 insertions(+), 25 deletions(-)

diff --git a/libevmjit-cpp/JitVM.cpp b/libevmjit-cpp/JitVM.cpp
index 613b5031c..e3bb09099 100644
--- a/libevmjit-cpp/JitVM.cpp
+++ b/libevmjit-cpp/JitVM.cpp
@@ -1,6 +1,7 @@
 
 #include "JitVM.h"
 #include <libevm/VM.h>
+#include <libevm/VMFactory.h>
 #include <evmjit/libevmjit/ExecutionEngine.h>
 #include "Utils.h"
 
@@ -9,22 +10,25 @@ namespace dev
 namespace eth
 {
 
-bytesConstRef JitVM::go(ExtVMFace& _ext, OnOpFunc const&, uint64_t)
+bytesConstRef JitVM::go(ExtVMFace& _ext, OnOpFunc const& _onOp, uint64_t _step)
 {
 	using namespace jit;
 
-	if (m_gas > std::numeric_limits<decltype(m_data.gas)>::max())
-		BOOST_THROW_EXCEPTION(OutOfGas()); // Do not accept requests with gas > 2^63 (int64 max) // TODO: Return "not accepted" exception to allow interpreted handle that
-
-	if (_ext.gasPrice > std::numeric_limits<decltype(m_data.gasPrice)>::max())
-		BOOST_THROW_EXCEPTION(OutOfGas());
-
-	if (_ext.currentBlock.number > std::numeric_limits<decltype(m_data.number)>::max())
-		BOOST_THROW_EXCEPTION(OutOfGas());
-
-	if (_ext.currentBlock.timestamp > std::numeric_limits<decltype(m_data.timestamp)>::max())
-		BOOST_THROW_EXCEPTION(OutOfGas());
+	auto rejected = false;
+	rejected |= m_gas > std::numeric_limits<decltype(m_data.gas)>::max(); // Do not accept requests with gas > 2^63 (int64 max)
+	rejected |= _ext.gasPrice > std::numeric_limits<decltype(m_data.gasPrice)>::max();
+	rejected |= _ext.currentBlock.number > std::numeric_limits<decltype(m_data.number)>::max();
+	rejected |= _ext.currentBlock.timestamp > std::numeric_limits<decltype(m_data.timestamp)>::max();
 
+	if (rejected)
+	{
+		UNTESTED;
+		std::cerr << "Rejected\n";
+		VMFactory::setKind(VMKind::Interpreter);
+		m_fallbackVM = VMFactory::create(m_gas);
+		VMFactory::setKind(VMKind::JIT);
+		return m_fallbackVM->go(_ext, _onOp, _step);
+	}
 
 	m_data.gas 			= static_cast<decltype(m_data.gas)>(m_gas);
 	m_data.gasPrice		= static_cast<decltype(m_data.gasPrice)>(_ext.gasPrice);
diff --git a/libevmjit-cpp/JitVM.h b/libevmjit-cpp/JitVM.h
index 90855127e..58caa3648 100644
--- a/libevmjit-cpp/JitVM.h
+++ b/libevmjit-cpp/JitVM.h
@@ -12,15 +12,13 @@ class JitVM: public VMFace
 {
 	virtual bytesConstRef go(ExtVMFace& _ext, OnOpFunc const& _onOp = {}, uint64_t _steps = (uint64_t)-1) override final;
 
-	enum Kind: bool { Interpreter, JIT };
-	static std::unique_ptr<VMFace> create(Kind, u256 _gas = 0);
-
 private:
 	friend class VMFactory;
 	explicit JitVM(u256 _gas = 0) : VMFace(_gas) {}
 
 	jit::RuntimeData m_data;
 	jit::ExecutionEngine m_engine;
+	std::unique_ptr<VMFace> m_fallbackVM; ///< VM used in case of input data rejected by JIT
 };
 
 
diff --git a/libevmjit/Common.h b/libevmjit/Common.h
index 7383b9f93..e485148fb 100644
--- a/libevmjit/Common.h
+++ b/libevmjit/Common.h
@@ -25,20 +25,24 @@ struct NoteChannel {};	// FIXME: Use some log library?
 
 enum class ReturnCode
 {
-	Stop = 0,
-	Return = 1,
+	// Success codes
+	Stop    = 0,
+	Return  = 1,
 	Suicide = 2,
 
-	OutOfGas = -1,
-	BadJumpDestination = -2,
-	StackTooSmall = -3,
-	BadInstruction = -4,
+	// Standard error codes
+	OutOfGas           = -1,
+	StackTooSmall      = -2,
+	BadJumpDestination = -3,
+	BadInstruction     = -4,
+	Rejected           = -5, ///< Input data (code, gas, block info, etc.) does not meet JIT requirement and execution request has been rejected
 
-	LLVMConfigError = -5,
-	LLVMCompileError = -6,
-	LLVMLinkError = -7,
+	// Internal error codes
+	LLVMConfigError    = -101,
+	LLVMCompileError   = -102,
+	LLVMLinkError      = -103,
 
-	UnexpectedException = -8,
+	UnexpectedException = -111,
 };
 
 /// Representation of 256-bit value binary compatible with LLVM i256