diff --git a/src/Reactor/SubzeroReactor.cpp b/src/Reactor/SubzeroReactor.cpp
index 5d057b0..15b0eec 100644
--- a/src/Reactor/SubzeroReactor.cpp
+++ b/src/Reactor/SubzeroReactor.cpp
@@ -51,8 +51,85 @@
 
 // Subzero utility functions
 // These functions only accept and return Subzero (Ice) types, and do not access any globals.
+namespace {
 namespace sz {
-static Ice::Constant *getConstantPointer(Ice::GlobalContext *context, void const *ptr)
+void replaceEntryNode(Ice::Cfg *function, Ice::CfgNode *newEntryNode)
+{
+	ASSERT_MSG(function->getEntryNode() != nullptr, "Function should have an entry node");
+
+	if(function->getEntryNode() == newEntryNode)
+	{
+		return;
+	}
+
+	// Make this the new entry node
+	function->setEntryNode(newEntryNode);
+
+	// Reorder nodes so that new entry block comes first. This is required
+	// by Cfg::renumberInstructions, which expects the first node in the list
+	// to be the entry node.
+	{
+		auto nodes = function->getNodes();
+
+		// TODO(amaiorano): Fast path if newEntryNode is last? Can avoid linear search.
+
+		auto iter = std::find(nodes.begin(), nodes.end(), newEntryNode);
+		ASSERT_MSG(iter != nodes.end(), "New node should be in the function's node list");
+
+		nodes.erase(iter);
+		nodes.insert(nodes.begin(), newEntryNode);
+
+		// swapNodes replaces its nodes with the input one, and renumbers them,
+		// so our new entry node will be 0, and the previous will be 1.
+		function->swapNodes(nodes);
+	}
+}
+
+Ice::Cfg *createFunction(Ice::GlobalContext *context, Ice::Type returnType, const std::vector<Ice::Type> &paramTypes)
+{
+	uint32_t sequenceNumber = 0;
+	auto function = Ice::Cfg::create(context, sequenceNumber).release();
+
+	Ice::CfgLocalAllocatorScope allocScope{ function };
+
+	for(auto type : paramTypes)
+	{
+		Ice::Variable *arg = function->makeVariable(type);
+		function->addArg(arg);
+	}
+
+	Ice::CfgNode *node = function->makeNode();
+	function->setEntryNode(node);
+
+	return function;
+}
+
+Ice::Type getPointerType(Ice::Type elementType)
+{
+	if(sizeof(void *) == 8)
+	{
+		return Ice::IceType_i64;
+	}
+	else
+	{
+		return Ice::IceType_i32;
+	}
+}
+
+Ice::Variable *allocateStackVariable(Ice::Cfg *function, Ice::Type type, int arraySize = 0)
+{
+	int typeSize = Ice::typeWidthInBytes(type);
+	int totalSize = typeSize * (arraySize ? arraySize : 1);
+
+	auto bytes = Ice::ConstantInteger32::create(function->getContext(), Ice::IceType_i32, totalSize);
+	auto address = function->makeVariable(getPointerType(type));
+	auto alloca = Ice::InstAlloca::create(function, address, bytes, typeSize);
+	function->getEntryNode()->getInsts().push_front(alloca);
+
+	return address;
+}
+
+Ice::Constant *getConstantPointer(Ice::GlobalContext *context, void const *ptr)
 {
 	if(sizeof(void *) == 8)
 	{
@@ -64,8 +141,38 @@
 	}
 }
 
+// Wrapper for calls on C functions with Ice types
+template<typename Return, typename... CArgs, typename... RArgs>
+Ice::Variable *Call(Ice::Cfg *function, Ice::CfgNode *basicBlock, Return(fptr)(CArgs...), RArgs &&... args)
+{
+	Ice::Type retTy = T(rr::CToReactorT<Return>::getType());
+
+	// Subzero doesn't support boolean return values. Replace with an i32.
+	if(retTy == Ice::IceType_i1)
+	{
+		retTy = Ice::IceType_i32;
+	}
+
+	Ice::Variable *ret = nullptr;
+	if(retTy != Ice::IceType_void)
+	{
+		ret = function->makeVariable(retTy);
+	}
+
+	std::initializer_list<Ice::Variable *> iceArgs = { std::forward<RArgs>(args)... };
+
+	auto call = Ice::InstCall::create(function, iceArgs.size(), ret, getConstantPointer(function->getContext(), reinterpret_cast<void const *>(fptr)), false);
+	for(auto arg : iceArgs)
+	{
+		call->addArg(arg);
+	}
+
+	basicBlock->appendInst(call);
+	return ret;
+}
+
 // Returns a non-const variable copy of const v
-static Ice::Variable *createUnconstCast(Ice::Cfg *function, Ice::CfgNode *basicBlock, Ice::Constant *v)
+Ice::Variable *createUnconstCast(Ice::Cfg *function, Ice::CfgNode *basicBlock, Ice::Constant *v)
 {
 	Ice::Variable *result = function->makeVariable(v->getType());
 	Ice::InstCast *cast = Ice::InstCast::create(function, Ice::InstCast::Bitcast, result, v);
@@ -73,7 +180,7 @@
 	return result;
 }
 
-static Ice::Variable *createLoad(Ice::Cfg *function, Ice::CfgNode *basicBlock, Ice::Operand *ptr, Ice::Type type, unsigned int align)
+Ice::Variable *createLoad(Ice::Cfg *function, Ice::CfgNode *basicBlock, Ice::Operand *ptr, Ice::Type type, unsigned int align)
 {
 	// TODO(b/148272103): InstLoad assumes that a constant ptr is an offset, rather than an
 	// absolute address. We circumvent this by casting to a non-const variable, and loading
@@ -91,9 +198,12 @@
 }
 
 }  // namespace sz
+}  // namespace
+
 namespace rr {
 class ELFMemoryStreamer;
-}
+class CoroutineGenerator;
+}  // namespace rr
 
 namespace {
 
@@ -119,6 +229,10 @@
 Ice::ELFFileStreamer *elfFile = nullptr;
 Ice::Fdstream *out = nullptr;
 
+// Coroutine globals
+rr::Type *coroYieldType = nullptr;
+std::shared_ptr<rr::CoroutineGenerator> coroGen;
+
 }  // Anonymous namespace
 
 namespace {
@@ -232,7 +346,11 @@
 }
 
 const Capabilities Caps = {
+#if defined(_WIN32)
+	true,  // CoroutinesSupported
+#else
 	false,  // CoroutinesSupported
+#endif
 };
 
 enum EmulatedType
@@ -274,11 +392,27 @@
 	return reinterpret_cast<Type *>(t);
 }
 
+std::vector<Ice::Type> T(const std::vector<Type *> &types)
+{
+	std::vector<Ice::Type> result;
+	result.reserve(types.size());
+	for(auto &t : types)
+	{
+		result.push_back(T(t));
+	}
+	return result;
+}
+
 Value *V(Ice::Operand *v)
 {
 	return reinterpret_cast<Value *>(v);
 }
 
+Ice::Operand *V(Value *v)
+{
+	return reinterpret_cast<Ice::Variable *>(v);
+}
+
 BasicBlock *B(Ice::CfgNode *b)
 {
 	return reinterpret_cast<BasicBlock *>(b);
@@ -303,6 +437,14 @@
 	return Ice::typeWidthInBytes(T(type));
 }
 
+static void createRetVoidIfNoRet()
+{
+	if(::basicBlock->getInsts().empty() || ::basicBlock->getInsts().back().getKind() != Ice::Inst::Ret)
+	{
+		Nucleus::createRetVoid();
+	}
+}
+
 using ElfHeader = std::conditional<sizeof(void *) == 8, Elf64_Ehdr, Elf32_Ehdr>::type;
 using SectionHeader = std::conditional<sizeof(void *) == 8, Elf64_Shdr, Elf32_Shdr>::type;
 
@@ -462,7 +604,7 @@
 	return symbolValue;
 }
 
-void *loadImage(uint8_t *const elfImage, size_t &codeSize)
+void *loadImage(uint8_t *const elfImage, size_t &codeSize, const char *functionName = nullptr)
 {
 	ElfHeader *elfHeader = (ElfHeader *)elfImage;
 
@@ -496,6 +638,15 @@
 		{
 			if(sectionHeader[i].sh_flags & SHF_EXECINSTR)
 			{
+				auto getCurrSectionName = [&]() {
+					auto sectionNameOffset = sectionHeader[elfHeader->e_shstrndx].sh_offset + sectionHeader[i].sh_name;
+					return reinterpret_cast<const char *>(elfImage + sectionNameOffset);
+				};
+				if(functionName && strstr(getCurrSectionName(), functionName) == nullptr)
+				{
+					continue;
+				}
+
 				entry = elfImage + sectionHeader[i].sh_offset;
 				codeSize = sectionHeader[i].sh_size;
 			}
@@ -593,22 +744,27 @@
 
 	void seek(uint64_t Off) override { position = Off; }
 
-	const void *finalizeEntryBegin()
+	const void *getEntryByName(const char *name)
 	{
-		position = std::numeric_limits<std::size_t>::max();  // Can't stream more data after this
-
 		size_t codeSize = 0;
-		const void *entry = loadImage(&buffer[0], codeSize);
+		const void *entry = loadImage(&buffer[0], codeSize, name);
 
-		protectMemoryPages(&buffer[0], buffer.size(), PERMISSION_READ | PERMISSION_EXECUTE);
 #if defined(_WIN32)
 		FlushInstructionCache(GetCurrentProcess(), NULL, 0);
 #else
 		__builtin___clear_cache((char *)entry, (char *)entry + codeSize);
 #endif
+
 		return entry;
 	}
 
+	void finalize()
+	{
+		position = std::numeric_limits<std::size_t>::max();  // Can't stream more data after this
+
+		protectMemoryPages(&buffer[0], buffer.size(), PERMISSION_READ | PERMISSION_EXECUTE);
+	}
+
 	void setEntry(int index, const void *func)
 	{
 		ASSERT(func);
@@ -664,6 +820,9 @@
 	Flags.setVerbose(subzeroDumpEnabled ? Ice::IceV_Most : Ice::IceV_None);
 	Flags.setDisableHybridAssembly(true);
 
+	// Emit functions into separate sections in the ELF so we can find them by name
+	Flags.setFunctionSections(true);
+
 	static llvm::raw_os_ostream cout(std::cout);
 	static llvm::raw_os_ostream cerr(std::cerr);
 
@@ -691,13 +850,24 @@
 Nucleus::~Nucleus()
 {
 	delete ::routine;
+	::routine = nullptr;
 
 	delete ::allocator;
+	::allocator = nullptr;
+
 	delete ::function;
+	::function = nullptr;
+
 	delete ::context;
+	::context = nullptr;
 
 	delete ::elfFile;
+	::elfFile = nullptr;
+
 	delete ::out;
+	::out = nullptr;
+
+	::basicBlock = nullptr;
 
 	::codegenMutex.unlock();
 }
@@ -721,56 +891,89 @@
 	return ::defaultConfig();
 }
 
-std::shared_ptr<Routine> Nucleus::acquireRoutine(const char *name, const Config::Edit &cfgEdit /* = Config::Edit::None */)
+// This function lowers and produces executable binary code in memory for the input functions,
+// and returns a Routine with the entry points to these functions.
+template<size_t Count>
+static std::shared_ptr<Routine> acquireRoutine(Ice::Cfg *const (&functions)[Count], const char *const (&names)[Count], const Config::Edit &cfgEdit)
 {
+	// This logic is modeled after the IceCompiler, as well as GlobalContext::translateFunctions
+	// and GlobalContext::emitItems.
+
 	if(subzeroDumpEnabled)
 	{
 		// Output dump strings immediately, rather than once buffer is full. Useful for debugging.
-		context->getStrDump().SetUnbuffered();
-	}
-
-	if(basicBlock->getInsts().empty() || basicBlock->getInsts().back().getKind() != Ice::Inst::Ret)
-	{
-		createRetVoid();
-	}
-
-	::function->setFunctionName(Ice::GlobalString::createWithString(::context, name));
-
-	rr::optimize(::function);
-
-	::function->computeInOutEdges();
-	ASSERT(!::function->hasError());
-
-	::function->translate();
-	ASSERT(!::function->hasError());
-
-	auto globals = ::function->getGlobalInits();
-
-	if(globals && !globals->empty())
-	{
-		::context->getGlobals()->merge(globals.get());
+		::context->getStrDump().SetUnbuffered();
 	}
 
 	::context->emitFileHeader();
 
-	if(subzeroEmitTextAsm)
+	// Translate
+
+	for(size_t i = 0; i < Count; ++i)
 	{
-		::function->emit();
+		Ice::Cfg *currFunc = functions[i];
+
+		// Install function allocator in TLS for Cfg-specific container allocators
+		Ice::CfgLocalAllocatorScope allocScope(currFunc);
+
+		currFunc->setFunctionName(Ice::GlobalString::createWithString(::context, names[i]));
+
+		rr::optimize(currFunc);
+
+		currFunc->computeInOutEdges();
+		ASSERT(!currFunc->hasError());
+
+		currFunc->translate();
+		ASSERT(!currFunc->hasError());
+
+		currFunc->getAssembler<>()->setInternal(currFunc->getInternal());
+
+		if(subzeroEmitTextAsm)
+		{
+			currFunc->emit();
+		}
+
+		currFunc->emitIAS();
 	}
 
-	::function->emitIAS();
-	auto assembler = ::function->releaseAssembler();
+	// Emit items
+
+	::context->lowerGlobals("");
+
 	auto objectWriter = ::context->getObjectWriter();
-	assembler->alignFunction();
-	objectWriter->writeFunctionCode(::function->getFunctionName(), false, assembler.get());
+
+	for(size_t i = 0; i < Count; ++i)
+	{
+		Ice::Cfg *currFunc = functions[i];
+
+		// Accumulate globals from functions to emit into the "last" section at the end
+		auto globals = currFunc->getGlobalInits();
+		if(globals && !globals->empty())
+		{
+			::context->getGlobals()->merge(globals.get());
+		}
+
+		auto assembler = currFunc->releaseAssembler();
+		assembler->alignFunction();
+		objectWriter->writeFunctionCode(currFunc->getFunctionName(), currFunc->getInternal(), assembler.get());
+	}
+
 	::context->lowerGlobals("last");
 	::context->lowerConstants();
 	::context->lowerJumpTables();
+
 	objectWriter->setUndefinedSyms(::context->getConstantExternSyms());
+	::context->emitTargetRODataSections();
 	objectWriter->writeNonUserSections();
 
-	const void *entryBegin = ::routine->finalizeEntryBegin();
-	::routine->setEntry(Nucleus::CoroutineEntryBegin, entryBegin);
+	// Done compiling functions, get entry pointers to each of them
+	for(size_t i = 0; i < Count; ++i)
+	{
+		const void *entry = ::routine->getEntryByName(names[i]);
+		::routine->setEntry(i, entry);
+	}
+
+	::routine->finalize();
 
 	Routine *handoffRoutine = ::routine;
 	::routine = nullptr;
@@ -778,6 +981,12 @@
 	return std::shared_ptr<Routine>(handoffRoutine);
 }
 
+std::shared_ptr<Routine> Nucleus::acquireRoutine(const char *name, const Config::Edit &cfgEdit /* = Config::Edit::None */)
+{
+	createRetVoidIfNoRet();
+	return rr::acquireRoutine({ ::function }, { name }, cfgEdit);
+}
+
 Value *Nucleus::allocateStackVariable(Type *t, int arraySize)
 {
 	Ice::Type type = T(t);
@@ -811,21 +1020,21 @@
 	::basicBlock = basicBlock;
 }
 
-void Nucleus::createFunction(Type *ReturnType, std::vector<Type *> &Params)
+void Nucleus::createFunction(Type *returnType, const std::vector<Type *> &paramTypes)
 {
-	uint32_t sequenceNumber = 0;
-	::function = Ice::Cfg::create(::context, sequenceNumber).release();
+	ASSERT(::function == nullptr);
+	ASSERT(::allocator == nullptr);
+	ASSERT(::basicBlock == nullptr);
+
+	::function = sz::createFunction(::context, T(returnType), T(paramTypes));
+
+	// NOTE: The scoped allocator sets the TLS allocator to the one in the function. This global one
+	// becomes invalid if another one is created; for example, when creating await and destroy functions
+	// for coroutines, in which case, we must make sure to create a new scoped allocator for ::function again.
+	// TODO: Get rid of this as a global, and create scoped allocs in every Nucleus function instead.
 	::allocator = new Ice::CfgLocalAllocatorScope(::function);
 
-	for(Type *type : Params)
-	{
-		Ice::Variable *arg = ::function->makeVariable(T(type));
-		::function->addArg(arg);
-	}
-
-	Ice::CfgNode *node = ::function->makeNode();
-	::function->setEntryNode(node);
-	::basicBlock = node;
+	::basicBlock = ::function->getEntryNode();
 }
 
 Value *Nucleus::getArgument(unsigned int index)
@@ -1152,7 +1361,7 @@
 	{
 		ASSERT(value->getType() == T(type));
 
-		auto store = Ice::InstStore::create(::function, value, ptr, align);
+		auto store = Ice::InstStore::create(::function, V(value), V(ptr), align);
 		::basicBlock->appendInst(store);
 	}
 
@@ -1556,14 +1765,7 @@
 
 Type *Nucleus::getPointerType(Type *ElementType)
 {
-	if(sizeof(void *) == 8)
-	{
-		return T(Ice::IceType_i64);
-	}
-	else
-	{
-		return T(Ice::IceType_i32);
-	}
+	return T(sz::getPointerType(T(ElementType)));
 }
 
 Value *Nucleus::createNullValue(Type *Ty)
@@ -2899,11 +3101,11 @@
 	Value *e;
 	int swizzle[16] = { 0, 16, 1, 17, 2, 18, 3, 19, 4, 20, 5, 21, 6, 22, 7, 23 };
 	Value *b = Nucleus::createBitCast(a, Byte16::getType());
-	Value *c = Nucleus::createShuffleVector(b, V(Nucleus::createNullValue(Byte16::getType())), swizzle);
+	Value *c = Nucleus::createShuffleVector(b, Nucleus::createNullValue(Byte16::getType()), swizzle);
 
 	int swizzle2[8] = { 0, 8, 1, 9, 2, 10, 3, 11 };
 	Value *d = Nucleus::createBitCast(c, Short8::getType());
-	e = Nucleus::createShuffleVector(d, V(Nucleus::createNullValue(Short8::getType())), swizzle2);
+	e = Nucleus::createShuffleVector(d, Nucleus::createNullValue(Short8::getType()), swizzle2);
 
 	Value *f = Nucleus::createBitCast(e, Int4::getType());
 	storeValue(f);
@@ -3879,34 +4081,507 @@
 void EmitDebugVariable(Value *value) {}
 void FlushDebug() {}
 
-void Nucleus::createCoroutine(Type *YieldType, std::vector<Type *> &Params)
+namespace {
+namespace coro {
+
+using FiberHandle = void *;
+
+// Instance data per generated coroutine
+// This is the "handle" type used for Coroutine functions
+// Lifetime: from yield to when CoroutineEntryDestroy generated function is called.
+struct CoroutineData
 {
-	// Subzero currently only supports coroutines as functions (i.e. that do not yield)
-	createFunction(YieldType, Params);
+	FiberHandle mainFiber{};
+	FiberHandle routineFiber{};
+	bool convertedFiber = false;
+
+	// Variables used by coroutines
+	bool done = false;
+	void *promisePtr = nullptr;
+};
+
+CoroutineData *createCoroutineData()
+{
+	return new CoroutineData{};
+}
+
+void destroyCoroutineData(CoroutineData *coroData)
+{
+	delete coroData;
+}
+
+void convertThreadToMainFiber(Nucleus::CoroutineHandle handle)
+{
+#if defined(_WIN32)
+	auto *coroData = reinterpret_cast<CoroutineData *>(handle);
+
+	coroData->mainFiber = ::ConvertThreadToFiber(nullptr);
+
+	if(coroData->mainFiber)
+	{
+		coroData->convertedFiber = true;
+	}
+	else
+	{
+		// We're probably already on a fiber, so just grab it and remember that we didn't
+		// convert it, so not to convert back to thread.
+		coroData->mainFiber = GetCurrentFiber();
+		coroData->convertedFiber = false;
+	}
+	ASSERT(coroData->mainFiber);
+#else
+	UNIMPLEMENTED("convertThreadToMainFiber not implemented for current platform");
+#endif
+}
+
+void convertMainFiberToThread(Nucleus::CoroutineHandle handle)
+{
+#if defined(_WIN32)
+	auto *coroData = reinterpret_cast<CoroutineData *>(handle);
+
+	ASSERT(coroData->mainFiber);
+
+	if(coroData->convertedFiber)
+	{
+		::ConvertFiberToThread();
+		coroData->mainFiber = nullptr;
+	}
+#else
+	UNIMPLEMENTED("convertMainFiberToThread not implemented for current platform");
+#endif
+}
+using FiberFunc = std::function<void()>;
+
+void createRoutineFiber(Nucleus::CoroutineHandle handle, FiberFunc *fiberFunc)
+{
+#if defined(_WIN32)
+	struct Invoker
+	{
+		FiberFunc func;
+
+		static VOID __stdcall fiberEntry(LPVOID lpParameter)
+		{
+			auto *func = reinterpret_cast<FiberFunc *>(lpParameter);
+			(*func)();
+		}
+	};
+
+	auto *coroData = reinterpret_cast<CoroutineData *>(handle);
+
+	constexpr SIZE_T StackSize = 2 * 1024 * 1024;
+	coroData->routineFiber = ::CreateFiber(StackSize, &Invoker::fiberEntry, fiberFunc);
+	ASSERT(coroData->routineFiber);
+#else
+	UNIMPLEMENTED("createRoutineFiber not implemented for current platform");
+#endif
+}
+
+void deleteRoutineFiber(Nucleus::CoroutineHandle handle)
+{
+#if defined(_WIN32)
+	auto *coroData = reinterpret_cast<CoroutineData *>(handle);
+	ASSERT(coroData->routineFiber);
+	::DeleteFiber(coroData->routineFiber);
+	coroData->routineFiber = nullptr;
+#else
+	UNIMPLEMENTED("deleteRoutineFiber not implemented for current platform");
+#endif
+}
+
+void switchToMainFiber(Nucleus::CoroutineHandle handle)
+{
+#if defined(_WIN32)
+	auto *coroData = reinterpret_cast<CoroutineData *>(handle);
+
+	// Win32
+	ASSERT(coroData->mainFiber);
+	::SwitchToFiber(coroData->mainFiber);
+#else
+	UNIMPLEMENTED("switchToMainFiber not implemented for current platform");
+#endif
+}
+
+void switchToRoutineFiber(Nucleus::CoroutineHandle handle)
+{
+#if defined(_WIN32)
+	auto *coroData = reinterpret_cast<CoroutineData *>(handle);
+
+	// Win32
+	ASSERT(coroData->routineFiber);
+	::SwitchToFiber(coroData->routineFiber);
+#else
+	UNIMPLEMENTED("switchToRoutineFiber not implemented for current platform");
+#endif
+}
+
+namespace detail {
+thread_local rr::Nucleus::CoroutineHandle coroHandle{};
+}  // namespace detail
+
+void setHandleParam(Nucleus::CoroutineHandle handle)
+{
+	ASSERT(!detail::coroHandle);
+	detail::coroHandle = handle;
+}
+
+Nucleus::CoroutineHandle getHandleParam()
+{
+	ASSERT(detail::coroHandle);
+	auto handle = detail::coroHandle;
+	detail::coroHandle = {};
+	return handle;
+}
+
+void setDone(Nucleus::CoroutineHandle handle)
+{
+	auto *coroData = reinterpret_cast<CoroutineData *>(handle);
+	ASSERT(!coroData->done);  // Should be called once
+	coroData->done = true;
+}
+
+bool isDone(Nucleus::CoroutineHandle handle)
+{
+	auto *coroData = reinterpret_cast<CoroutineData *>(handle);
+	return coroData->done;
+}
+
+void setPromisePtr(Nucleus::CoroutineHandle handle, void *promisePtr)
+{
+	auto *coroData = reinterpret_cast<CoroutineData *>(handle);
+	coroData->promisePtr = promisePtr;
+}
+
+void *getPromisePtr(Nucleus::CoroutineHandle handle)
+{
+	auto *coroData = reinterpret_cast<CoroutineData *>(handle);
+	return coroData->promisePtr;
+}
+
+}  // namespace coro
+}  // namespace
+
+// Used to generate coroutines.
+// Lifetime: from yield to acquireCoroutine
+class CoroutineGenerator
+{
+public:
+	CoroutineGenerator()
+	{
+	}
+
+	// Inserts instructions at the top of the current function to make it a coroutine.
+	void generateCoroutineBegin()
+	{
+		// Begin building the main coroutine_begin() function.
+		// We insert these instructions at the top of the entry node,
+		// before existing reactor-generated instructions.
+
+		//    CoroutineHandle coroutine_begin(<Arguments>)
+		//    {
+		//        this->handle = coro::getHandleParam();
+		//
+		//        YieldType promise;
+		//        coro::setPromisePtr(handle, &promise); // For await
+		//
+		//        ... <REACTOR CODE> ...
+		//
+
+		// Save original entry block and current block, and create a new entry block and make it current.
+		// This new block will be used to inject code above the begin routine's existing code. We make
+		// this block branch to the original entry block as the last instruction.
+		auto origEntryBB = ::function->getEntryNode();
+		auto origCurrBB = ::basicBlock;
+		auto newBB = ::function->makeNode();
+		sz::replaceEntryNode(::function, newBB);
+		::basicBlock = newBB;
+
+		//        this->handle = coro::getHandleParam();
+		this->handle = sz::Call(::function, ::basicBlock, coro::getHandleParam);
+
+		//        YieldType promise;
+		//        coro::setPromisePtr(handle, &promise); // For await
+		this->promise = sz::allocateStackVariable(::function, T(::coroYieldType));
+		sz::Call(::function, ::basicBlock, coro::setPromisePtr, this->handle, this->promise);
+
+		// Branch to original entry block
+		auto br = Ice::InstBr::create(::function, origEntryBB);
+		::basicBlock->appendInst(br);
+
+		// Restore current block for future instructions
+		::basicBlock = origCurrBB;
+	}
+
+	// Adds instructions for Yield() calls at the current location of the main coroutine function.
+	void generateYield(Value *val)
+	{
+		//        ... <REACTOR CODE> ...
+		//
+		//        promise = val;
+		//        coro::switchToMainFiber(handle);
+		//
+		//        ... <REACTOR CODE> ...
+
+		Nucleus::createStore(val, V(this->promise), ::coroYieldType);
+		sz::Call(::function, ::basicBlock, coro::switchToMainFiber, this->handle);
+	}
+
+	// Adds instructions at the end of the current main coroutine function to end the coroutine.
+	void generateCoroutineEnd()
+	{
+		//        ... <REACTOR CODE> ...
+		//
+		//        coro::setDone(handle);
+		//        coro::switchToMainFiber();
+		//        // Unreachable
+		//    }
+		//
+
+		sz::Call(::function, ::basicBlock, coro::setDone, this->handle);
+
+		// A Win32 Fiber function must not end, otherwise it tears down the thread it's running on.
+		// So we add code to switch back to the main thread.
+		sz::Call(::function, ::basicBlock, coro::switchToMainFiber, this->handle);
+	}
+
+	using FunctionUniquePtr = std::unique_ptr<Ice::Cfg>;
+
+	// Generates the await function for the current coroutine.
+	// Cannot use Nucleus functions that modify ::function and ::basicBlock.
+	static FunctionUniquePtr generateAwaitFunction()
+	{
+		// bool coroutine_await(CoroutineHandle handle, YieldType* out)
+		// {
+		//     if (coro::isDone())
+		//     {
+		//         return false;
+		//     }
+		//     else // resume
+		//     {
+		//         YieldType* promise = coro::getPromisePtr(handle);
+		//         *out = *promise;
+		//         coro::switchToRoutineFiber(handle);
+		//         return true;
+		//     }
+		// }
+
+		// Subzero doesn't support bool types (IceType_i1) as return type
+		const Ice::Type ReturnType = Ice::IceType_i32;
+		const Ice::Type YieldPtrType = sz::getPointerType(T(::coroYieldType));
+		const Ice::Type HandleType = sz::getPointerType(Ice::IceType_void);
+
+		Ice::Cfg *awaitFunc = sz::createFunction(::context, ReturnType, std::vector<Ice::Type>{ HandleType, YieldPtrType });
+		Ice::CfgLocalAllocatorScope scopedAlloc{ awaitFunc };
+
+		Ice::Variable *handle = awaitFunc->getArgs()[0];
+		Ice::Variable *outPtr = awaitFunc->getArgs()[1];
+
+		auto doneBlock = awaitFunc->makeNode();
+		{
+			//         return false;
+			Ice::InstRet *ret = Ice::InstRet::create(awaitFunc, ::context->getConstantInt32(0));
+			doneBlock->appendInst(ret);
+		}
+
+		auto resumeBlock = awaitFunc->makeNode();
+		{
+			//         YieldType* promise = coro::getPromisePtr(handle);
+			Ice::Variable *promise = sz::Call(awaitFunc, resumeBlock, coro::getPromisePtr, handle);
+
+			//         *out = *promise;
+			// Load promise value
+			Ice::Variable *promiseVal = awaitFunc->makeVariable(T(::coroYieldType));
+			auto load = Ice::InstLoad::create(awaitFunc, promiseVal, promise);
+			resumeBlock->appendInst(load);
+			// Then store it in output param
+			auto store = Ice::InstStore::create(awaitFunc, promiseVal, outPtr);
+			resumeBlock->appendInst(store);
+
+			//         coro::switchToRoutineFiber(handle);
+			sz::Call(awaitFunc, resumeBlock, coro::switchToRoutineFiber, handle);
+
+			//         return true;
+			Ice::InstRet *ret = Ice::InstRet::create(awaitFunc, ::context->getConstantInt32(1));
+			resumeBlock->appendInst(ret);
+		}
+
+		//     if (coro::isDone())
+		//     {
+		//         <doneBlock>
+		//     }
+		//     else // resume
+		//     {
+		//         <resumeBlock>
+		//     }
+		Ice::CfgNode *bb = awaitFunc->getEntryNode();
+		Ice::Variable *done = sz::Call(awaitFunc, bb, coro::isDone);
+		auto br = Ice::InstBr::create(awaitFunc, done, doneBlock, resumeBlock);
+		bb->appendInst(br);
+
+		return FunctionUniquePtr{ awaitFunc };
+	}
+
+	// Generates the destroy function for the current coroutine.
+	// Cannot use Nucleus functions that modify ::function and ::basicBlock.
+	static FunctionUniquePtr generateDestroyFunction()
+	{
+		// void coroutine_destroy(Nucleus::CoroutineHandle handle)
+		// {
+		//     coro::convertMainFiberToThread(coroData);
+		//     coro::deleteRoutineFiber(handle);
+		//     coro::destroyCoroutineData(handle);
+		//     return;
+		// }
+
+		const Ice::Type ReturnType = Ice::IceType_void;
+		const Ice::Type HandleType = sz::getPointerType(Ice::IceType_void);
+
+		Ice::Cfg *destroyFunc = sz::createFunction(::context, ReturnType, std::vector<Ice::Type>{ HandleType });
+		Ice::CfgLocalAllocatorScope scopedAlloc{ destroyFunc };
+
+		Ice::Variable *handle = destroyFunc->getArgs()[0];
+
+		auto *bb = destroyFunc->getEntryNode();
+
+		//     coro::convertMainFiberToThread(coroData);
+		sz::Call(destroyFunc, bb, coro::convertMainFiberToThread, handle);
+
+		//     coro::deleteRoutineFiber(handle);
+		sz::Call(destroyFunc, bb, coro::deleteRoutineFiber, handle);
+
+		//     coro::destroyCoroutineData(handle);
+		sz::Call(destroyFunc, bb, coro::destroyCoroutineData, handle);
+
+		//     return;
+		Ice::InstRet *ret = Ice::InstRet::create(destroyFunc);
+		bb->appendInst(ret);
+
+		return FunctionUniquePtr{ destroyFunc };
+	}
+
+private:
+	Ice::Variable *handle{};
+	Ice::Variable *promise{};
+};
+
+static Nucleus::CoroutineHandle invokeCoroutineBegin(std::function<Nucleus::CoroutineHandle()> beginFunc)
+{
+	// This doubles up as our coroutine handle
+	auto coroData = coro::createCoroutineData();
+
+	// Convert current thread to a fiber so we can create new fibers and switch to them
+	coro::convertThreadToMainFiber(coroData);
+
+	coro::FiberFunc fiberFunc = [&]() {
+		// Store handle in TLS so that the coroutine can grab it right away, before
+		// any fiber switch occurs.
+		coro::setHandleParam(coroData);
+
+		// Invoke the begin function in the context of the routine fiber
+		beginFunc();
+
+		// Either it yielded, or finished. In either case, we switch back to the main fiber.
+		// We don't ever return from this function, or the current thread will be destroyed.
+		coro::switchToMainFiber(coroData);
+	};
+
+	coro::createRoutineFiber(coroData, &fiberFunc);
+
+	// Fiber will now start running, executing the saved beginFunc
+	coro::switchToRoutineFiber(coroData);
+
+	return coroData;
+}
+
+void Nucleus::createCoroutine(Type *yieldType, const std::vector<Type *> &params)
+{
+	// Start by creating a regular function
+	createFunction(yieldType, params);
+
+	// Save in case yield() is called
+	ASSERT(::coroYieldType == nullptr);  // Only one coroutine can be generated at once
+	::coroYieldType = yieldType;
+}
+
+void Nucleus::yield(Value *val)
+{
+	Variable::materializeAll();
+
+	// On first yield, we start generating coroutine functions
+	if(!::coroGen)
+	{
+		::coroGen = std::make_shared<CoroutineGenerator>();
+		::coroGen->generateCoroutineBegin();
+	}
+
+	ASSERT(::coroGen);
+	::coroGen->generateYield(val);
 }
 
 static bool coroutineEntryAwaitStub(Nucleus::CoroutineHandle, void *yieldValue)
 {
 	return false;
 }
-static void coroutineEntryDestroyStub(Nucleus::CoroutineHandle) {}
+
+static void coroutineEntryDestroyStub(Nucleus::CoroutineHandle handle)
+{
+}
 
 std::shared_ptr<Routine> Nucleus::acquireCoroutine(const char *name, const Config::Edit &cfgEdit /* = Config::Edit::None */)
 {
-	// acquireRoutine sets the CoroutineEntryBegin entry
-	auto coroutineEntry = acquireRoutine(name, cfgEdit);
+	if(::coroGen)
+	{
+		// Finish generating coroutine functions
+		{
+			Ice::CfgLocalAllocatorScope scopedAlloc{ ::function };
+			::coroGen->generateCoroutineEnd();
+			createRetVoidIfNoRet();
+		}
 
-	// For now, set the await and destroy entries to stubs, until we add proper coroutine support to the Subzero backend
-	auto routine = std::static_pointer_cast<ELFMemoryStreamer>(coroutineEntry);
-	routine->setEntry(Nucleus::CoroutineEntryAwait, reinterpret_cast<const void *>(&coroutineEntryAwaitStub));
-	routine->setEntry(Nucleus::CoroutineEntryDestroy, reinterpret_cast<const void *>(&coroutineEntryDestroyStub));
+		auto awaitFunc = ::coroGen->generateAwaitFunction();
+		auto destroyFunc = ::coroGen->generateDestroyFunction();
 
-	return coroutineEntry;
+		// At this point, we no longer need the CoroutineGenerator.
+		::coroGen.reset();
+		::coroYieldType = nullptr;
+
+		auto routine = rr::acquireRoutine({ ::function, awaitFunc.get(), destroyFunc.get() },
+		                                  { name, "await", "destroy" },
+		                                  cfgEdit);
+
+		return routine;
+	}
+	else
+	{
+		{
+			Ice::CfgLocalAllocatorScope scopedAlloc{ ::function };
+			createRetVoidIfNoRet();
+		}
+
+		::coroYieldType = nullptr;
+
+		// Not an actual coroutine (no yields), so return stubs for await and destroy
+		auto routine = rr::acquireRoutine({ ::function }, { name }, cfgEdit);
+
+		auto routineImpl = std::static_pointer_cast<ELFMemoryStreamer>(routine);
+		routineImpl->setEntry(Nucleus::CoroutineEntryAwait, reinterpret_cast<const void *>(&coroutineEntryAwaitStub));
+		routineImpl->setEntry(Nucleus::CoroutineEntryDestroy, reinterpret_cast<const void *>(&coroutineEntryDestroyStub));
+		return routine;
+	}
 }
 
-void Nucleus::yield(Value *val)
+Nucleus::CoroutineHandle Nucleus::invokeCoroutineBegin(Routine &routine, std::function<Nucleus::CoroutineHandle()> func)
 {
-	UNIMPLEMENTED("Yield");
+	const bool isCoroutine = routine.getEntry(Nucleus::CoroutineEntryAwait) != reinterpret_cast<const void *>(&coroutineEntryAwaitStub);
+
+	if(isCoroutine)
+	{
+		return rr::invokeCoroutineBegin(func);
+	}
+	else
+	{
+		// For regular routines, just invoke the begin func directly
+		return func();
+	}
 }
 
 }  // namespace rr