diff --git a/evmjit/libevmjit/Arith256.cpp b/evmjit/libevmjit/Arith256.cpp
index e88fda432..029eb9370 100644
--- a/evmjit/libevmjit/Arith256.cpp
+++ b/evmjit/libevmjit/Arith256.cpp
@@ -170,18 +170,7 @@ llvm::Function* Arith256::getDivFunc(llvm::Type* _type)
 		auto yLz = m_builder.CreateCall2(ctlzIntr, yArg, m_builder.getInt1(true), "y.lz");
 		auto rLz = m_builder.CreateCall2(ctlzIntr, r0, m_builder.getInt1(true), "r.lz");
 		auto i0 = m_builder.CreateNUWSub(yLz, rLz, "i0");
-		auto shlBy0 = m_builder.CreateICmpEQ(i0, zero);
 		auto y0 = m_builder.CreateShl(yArg, i0);
-		if (_type == m_builder.getIntNTy(512)) // Workaround for shl bug for long shifts
-		{
-			const auto treshold = m_builder.getIntN(512, 128);
-			auto highShift = m_builder.CreateICmpUGT(i0, treshold);
-			auto s = m_builder.CreateNUWSub(i0, treshold);
-			auto yhs = m_builder.CreateShl(yArg, treshold);
-			yhs = m_builder.CreateShl(yhs, s);
-			y0 = m_builder.CreateSelect(highShift, yhs, y0);
-		}
-		y0 = m_builder.CreateSelect(shlBy0, yArg, y0, "y0"); // Workaround for LLVM bug: shl by 0 produces wrong result
 		m_builder.CreateBr(loopBB);
 
 		m_builder.SetInsertPoint(loopBB);
diff --git a/evmjit/libevmjit/Compiler.cpp b/evmjit/libevmjit/Compiler.cpp
index 1e1f8fe93..d5cb493ab 100644
--- a/evmjit/libevmjit/Compiler.cpp
+++ b/evmjit/libevmjit/Compiler.cpp
@@ -464,12 +464,8 @@ void Compiler::compileBasicBlock(BasicBlock& _basicBlock, RuntimeManager& _runti
 			// test for word >> (k * 8 + 7)
 			auto bitpos = m_builder.CreateAdd(k32x8, m_builder.getInt64(7), "bitpos");
 			auto bitposEx = m_builder.CreateZExt(bitpos, Type::Word);
-			auto bittester = m_builder.CreateShl(Constant::get(1), bitposEx);
-			auto bitresult = m_builder.CreateAnd(word, bittester);
-			auto bittest = m_builder.CreateICmpUGT(bitresult, Constant::get(0));
-			// FIXME: The following does not work - LLVM bug, report!
-			//auto bitval = m_builder.CreateLShr(word, bitpos, "bitval");
-			//auto bittest = m_builder.CreateTrunc(bitval, Type::Bool, "bittest");
+			auto bitval = m_builder.CreateLShr(word, bitposEx, "bitval");
+			auto bittest = m_builder.CreateTrunc(bitval, Type::Bool, "bittest");
 
 			auto mask_ = m_builder.CreateShl(Constant::get(1), bitposEx);
 			auto mask = m_builder.CreateSub(mask_, Constant::get(1), "mask");
diff --git a/evmjit/libevmjit/Endianness.cpp b/evmjit/libevmjit/Endianness.cpp
index d36f4b7fa..25b66c0d5 100644
--- a/evmjit/libevmjit/Endianness.cpp
+++ b/evmjit/libevmjit/Endianness.cpp
@@ -18,9 +18,8 @@ llvm::Value* Endianness::bswapIfLE(llvm::IRBuilder<>& _builder, llvm::Value* _wo
 {
 	if (llvm::sys::IsLittleEndianHost)
 	{
-		// FIXME: Disabled because of problems with BYTE
-		//if (auto constant = llvm::dyn_cast<llvm::ConstantInt>(_word))
-		//	return _builder.getInt(constant->getValue().byteSwap());
+		if (auto constant = llvm::dyn_cast<llvm::ConstantInt>(_word))
+			return _builder.getInt(constant->getValue().byteSwap());
 
 		// OPT: Cache func declaration?
 		auto bswapFunc = llvm::Intrinsic::getDeclaration(_builder.GetInsertBlock()->getParent()->getParent(), llvm::Intrinsic::bswap, Type::Word);
diff --git a/evmjit/libevmjit/ExecutionEngine.cpp b/evmjit/libevmjit/ExecutionEngine.cpp
index 9bd767158..fba9cfd96 100644
--- a/evmjit/libevmjit/ExecutionEngine.cpp
+++ b/evmjit/libevmjit/ExecutionEngine.cpp
@@ -85,20 +85,7 @@ void parseOptions()
 {
 	static llvm::llvm_shutdown_obj shutdownObj{};
 	cl::AddExtraVersionPrinter(printVersion);
-	//cl::ParseEnvironmentOptions("evmjit", "EVMJIT", "Ethereum EVM JIT Compiler");
-
-	// FIXME: LLVM workaround:
-	// Manually select instruction scheduler. Confirmed bad schedulers: source, list-burr, list-hybrid.
-	// "source" scheduler has a bug: http://llvm.org/bugs/show_bug.cgi?id=22304
-	auto envLine = std::getenv("EVMJIT");
-	auto commandLine = std::string{"evmjit "} + (envLine ? envLine : "") + " -pre-RA-sched=list-ilp\0";
-	static const auto c_maxArgs = 20;
-	char const* argv[c_maxArgs] = {nullptr, };
-	auto arg = std::strtok(&*commandLine.begin(), " ");
-	auto i = 0;
-	for (; i < c_maxArgs && arg; ++i, arg = std::strtok(nullptr, " "))
-		argv[i] = arg;
-	cl::ParseCommandLineOptions(i, argv, "Ethereum EVM JIT Compiler");
+	cl::ParseEnvironmentOptions("evmjit", "EVMJIT", "Ethereum EVM JIT Compiler");
 }
 
 }
diff --git a/evmjit/libevmjit/GasMeter.cpp b/evmjit/libevmjit/GasMeter.cpp
index ffbd654e6..c0a2ed287 100644
--- a/evmjit/libevmjit/GasMeter.cpp
+++ b/evmjit/libevmjit/GasMeter.cpp
@@ -216,22 +216,12 @@ void GasMeter::countExp(llvm::Value* _exponent)
 	// cost = ((256 - lz) + 7) / 8
 
 	// OPT: Can gas update be done in exp algorithm?
-
-	auto t = llvm::APInt{256, 1};
-	auto c = m_builder.CreateSelect(m_builder.CreateICmpUGE(_exponent, Constant::get(t)), m_builder.getInt64(1), m_builder.getInt64(0));
-	for (auto i = 2; i <= 32; ++i)
-	{
-		t <<= 8;
-		c = m_builder.CreateSelect(m_builder.CreateICmpUGE(_exponent, Constant::get(t)), m_builder.getInt64(i), c);
-	}
-
-	// FIXME: Does not work because of LLVM bug: https://llvm.org/bugs/show_bug.cgi?id=22304
-//	auto ctlz = llvm::Intrinsic::getDeclaration(getModule(), llvm::Intrinsic::ctlz, Type::Word);
-//	auto lz256 = m_builder.CreateCall2(ctlz, _exponent, m_builder.getInt1(false));
-//	auto lz = m_builder.CreateTrunc(lz256, Type::Gas, "lz");
-//	auto sigBits = m_builder.CreateSub(m_builder.getInt64(256), lz, "sigBits");
-//	auto sigBytes = m_builder.CreateUDiv(m_builder.CreateAdd(sigBits, m_builder.getInt64(7)), m_builder.getInt64(8));
-	count(m_builder.CreateNUWMul(c, m_builder.getInt64(c_expByteGas)));
+	auto ctlz = llvm::Intrinsic::getDeclaration(getModule(), llvm::Intrinsic::ctlz, Type::Word);
+	auto lz256 = m_builder.CreateCall2(ctlz, _exponent, m_builder.getInt1(false));
+	auto lz = m_builder.CreateTrunc(lz256, Type::Gas, "lz");
+	auto sigBits = m_builder.CreateSub(m_builder.getInt64(256), lz, "sigBits");
+	auto sigBytes = m_builder.CreateUDiv(m_builder.CreateAdd(sigBits, m_builder.getInt64(7)), m_builder.getInt64(8));
+	count(m_builder.CreateNUWMul(sigBytes, m_builder.getInt64(c_expByteGas)));
 }
 
 void GasMeter::countSStore(Ext& _ext, llvm::Value* _index, llvm::Value* _newValue)
diff --git a/evmjit/libevmjit/Optimizer.cpp b/evmjit/libevmjit/Optimizer.cpp
index 731fda5c6..df88b4df8 100644
--- a/evmjit/libevmjit/Optimizer.cpp
+++ b/evmjit/libevmjit/Optimizer.cpp
@@ -16,9 +16,9 @@ namespace jit
 bool optimize(llvm::Module& _module)
 {
 	auto pm = llvm::legacy::PassManager{};
-	//pm.add(llvm::createFunctionInliningPass(2, 2)); // Produces invalid IR
+	//pm.add(llvm::createFunctionInliningPass(2, 2)); // Problem with APInt value bigger than 64bit
 	pm.add(llvm::createCFGSimplificationPass());
-	//pm.add(llvm::createInstructionCombiningPass()); // Produces invalid runtime results
+	pm.add(llvm::createInstructionCombiningPass());
 	pm.add(llvm::createAggressiveDCEPass());
 	pm.add(llvm::createLowerSwitchPass());
 	return pm.run(_module);
diff --git a/evmjit/libevmjit/preprocessor/llvm_includes_end.h b/evmjit/libevmjit/preprocessor/llvm_includes_end.h
index 2ead6dda3..643e03064 100644
--- a/evmjit/libevmjit/preprocessor/llvm_includes_end.h
+++ b/evmjit/libevmjit/preprocessor/llvm_includes_end.h
@@ -1,7 +1,3 @@
 #if defined(_MSC_VER)
 	#pragma warning(pop)
-#elif defined(__clang__)
-	#pragma clang diagnostic pop
-#else
-	#pragma GCC diagnostic pop
 #endif
diff --git a/evmjit/libevmjit/preprocessor/llvm_includes_start.h b/evmjit/libevmjit/preprocessor/llvm_includes_start.h
index 9077bf43f..9499f9835 100644
--- a/evmjit/libevmjit/preprocessor/llvm_includes_start.h
+++ b/evmjit/libevmjit/preprocessor/llvm_includes_start.h
@@ -1,12 +1,4 @@
 #if defined(_MSC_VER)
 	#pragma warning(push)
 	#pragma warning(disable: 4267 4244 4800)
-#elif defined(__clang__)
-	#pragma clang diagnostic push
-	#pragma clang diagnostic ignored "-Wunused-parameter"
-	#pragma clang diagnostic ignored "-Wconversion"
-#else
-	#pragma GCC diagnostic push
-	#pragma GCC diagnostic ignored "-Wunused-parameter"
-	#pragma GCC diagnostic ignored "-Wconversion"
 #endif