Index: llvm/include/llvm/Support/TaskQueue.h
===================================================================
--- /dev/null
+++ llvm/include/llvm/Support/TaskQueue.h
@@ -0,0 +1,104 @@
+//===-- llvm/Support/TaskQueue.h - A TaskQueue implementation ---*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file defines a crude C++11 based task queue.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_SUPPORT_TASK_QUEUE_H
+#define LLVM_SUPPORT_TASK_QUEUE_H
+
+#include "llvm/Config/llvm-config.h"
+#include "llvm/Support/ThreadPool.h"
+#include "llvm/Support/thread.h"
+
+#include <atomic>
+#include <cassert>
+#include <condition_variable>
+#include <functional>
+#include <future>
+#include <memory>
+#include <mutex>
+#include <queue>
+#include <utility>
+
+namespace llvm {
+/// TaskQueue executes work on exactly 1 thread in a first in first out
+/// fashion.  All work is guaranteed to execute in the order it is received.
+class TaskQueue {
+public:
+  /// Construct a task queue with no work.
+  TaskQueue(ThreadPool &Pool);
+
+  /// Blocking destructor: the queue will wait for all work to complete.
+  ~TaskQueue();
+
+  /// Asynchronous submission of a task to the queue. The returned future can be
+  /// used to wait for the task (and all previous tasks that have not yet
+  /// completed) to finish.
+  template <typename Callable> std::future<void> async(Callable &&C) {
+    std::future<void> Future;
+    std::function<void()> Func;
+    {
+      std::lock_guard<std::mutex> Lock(QueueLock);
+      std::tie(Func, Future) = CreateTask(std::forward<Callable>(C));
+
+      // If there's already a task in flight, just queue this one up.
+      if (IsTaskInFlight)
+        Tasks.push(std::move(Func));
+    }
+    Scheduler.async(std::move(Func));
+    return Future;
+  }
+
+private:
+  template <typename Callable>
+  std::pair<std::function<void()>, std::future<void>> CreateTask(Callable &&C) {
+    auto P = std::make_shared<std::promise<void>>();
+
+    // Because we don't have init capture to use move-only local variables that
+    // are captured into a lambda, we create the promise inside an explicit
+    // callable struct. We want to do as much of the wrapping in the
+    // type-specialized domain (before type erasure) and then erase this into a
+    // std::function.
+    std::function<void()> WrappedTask = [this, C, P] {
+      C();
+      P->set_value();
+
+      std::function<void()> Continuation;
+      {
+        std::lock_guard<std::mutex> Lock(QueueLock);
+        if (Tasks.empty()) {
+          IsTaskInFlight = false;
+          return;
+        }
+
+        Continuation = std::move(Tasks.front());
+        Tasks.pop();
+      }
+      Scheduler.async(std::move(Continuation));
+    };
+
+    return std::make_pair(std::move(WrappedTask), P->get_future());
+  }
+
+  /// The thread pool on which to run the work.
+  ThreadPool &Scheduler;
+
+  /// Tasks waiting for execution in the queue.
+  std::queue<std::function<void()>> Tasks;
+
+  bool IsTaskInFlight = false;
+
+  /// Mutex for synchronizing access to the Tasks array.
+  std::mutex QueueLock;
+};
+} // namespace llvm
+
+#endif // LLVM_SUPPORT_TASK_QUEUE_H
Index: llvm/lib/Support/CMakeLists.txt
===================================================================
--- llvm/lib/Support/CMakeLists.txt
+++ llvm/lib/Support/CMakeLists.txt
@@ -116,6 +116,7 @@
   SystemUtils.cpp
   TarWriter.cpp
   TargetParser.cpp
+  TaskQueue.cpp
   ThreadPool.cpp
   Timer.cpp
   ToolOutputFile.cpp
Index: llvm/lib/Support/TaskQueue.cpp
===================================================================
--- /dev/null
+++ llvm/lib/Support/TaskQueue.cpp
@@ -0,0 +1,54 @@
+//==-- llvm/Support/TaskQueue.cpp - A TaskQueue implementation ---*- C++ -*-==//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file implements a crude C++11 based task queue.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Support/TaskQueue.h"
+
+#include "llvm/Config/llvm-config.h"
+#include "llvm/Support/Threading.h"
+#include "llvm/Support/raw_ostream.h"
+
+using namespace llvm;
+
+#if LLVM_ENABLE_THREADS
+
+TaskQueue::TaskQueue(ThreadPool &Scheduler) : Scheduler(Scheduler) {}
+
+// The destructor joins the work thread, waiting for completion.
+TaskQueue::~TaskQueue() { Scheduler.wait(); }
+
+#else // LLVM_ENABLE_THREADS Disabled
+
+TaskQueue::TaskQueue() {}
+
+std::shared_future<void> TaskQueue::asyncImpl(TaskFunctionTy Task) {
+  std::shared_future<void> ParentFuture;
+  if (!Tasks.empty())
+    ParentFuture = Tasks.back();
+
+  auto Future = std::async(std::launch::deferred,
+                           [this, ParentFuture, Task] {
+                             if (ParentFuture.valid())
+                               ParentFuture.wait();
+
+                             Task();
+                             Tasks.pop();
+                           })
+                    .share();
+
+  Tasks.push(Future);
+  return Future;
+}
+
+TaskQueue::~TaskQueue() { wait(); }
+
+#endif
Index: llvm/unittests/Support/CMakeLists.txt
===================================================================
--- llvm/unittests/Support/CMakeLists.txt
+++ llvm/unittests/Support/CMakeLists.txt
@@ -53,6 +53,7 @@
   SwapByteOrderTest.cpp
   TarWriterTest.cpp
   TargetParserTest.cpp
+  TaskQueueTest.cpp
   ThreadLocalTest.cpp
   ThreadPool.cpp
   Threading.cpp
Index: llvm/unittests/Support/TaskQueueTest.cpp
===================================================================
--- /dev/null
+++ llvm/unittests/Support/TaskQueueTest.cpp
@@ -0,0 +1,185 @@
+//========- unittests/Support/TaskQueue.cpp - TaskQueue.h tests ------========//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Support/TaskQueue.h"
+
+#include "gtest/gtest.h"
+
+using namespace llvm;
+
+class TaskQueueTest : public testing::Test {
+protected:
+  TaskQueueTest() {}
+
+  /// Make sure this thread not progress faster than the main thread.
+  void waitForMainThread() {
+    std::unique_lock<std::mutex> LockGuard(WaitMainThreadMutex);
+    WaitMainThread.wait(LockGuard, [&] { return MainThreadReady; });
+  }
+
+  /// Set the readiness of the main thread.
+  void setMainThreadReady() {
+    {
+      std::unique_lock<std::mutex> LockGuard(WaitMainThreadMutex);
+      MainThreadReady = true;
+    }
+    WaitMainThread.notify_all();
+  }
+
+  void SetUp() override { MainThreadReady = false; }
+
+  std::condition_variable WaitMainThread;
+  std::mutex WaitMainThreadMutex;
+  bool MainThreadReady;
+};
+
+TEST_F(TaskQueueTest, OrderedFutures) {
+  ThreadPool TP(1);
+  TaskQueue TQ(TP);
+  std::atomic<int> X = 0;
+  std::atomic<int> Y = 0;
+  std::atomic<int> Z = 0;
+
+  std::future<void> F1 = TQ.async([&] {
+    waitForMainThread();
+    ++X;
+  });
+  std::future<void> F2 = TQ.async([&] {
+    waitForMainThread();
+    ++Y;
+  });
+  std::future<void> F3 = TQ.async([&] {
+    waitForMainThread();
+    ++Z;
+  });
+
+  setMainThreadReady();
+  F1.wait();
+  ASSERT_EQ(1, X);
+#if !LLVM_ENABLE_THREADS
+  // We can't check this in the LLVM_ENABLE_THREADS case since the work thread
+  // proceeds independently of the main thread, so this may or may not still
+  // be true.
+  ASSERT_EQ(0, Y);
+  ASSERT_EQ(0, Z);
+#endif
+
+  F2.wait();
+  ASSERT_EQ(1, X);
+  ASSERT_EQ(1, Y);
+#if !LLVM_ENABLE_THREADS
+  ASSERT_EQ(0, Z);
+#endif
+
+  F3.wait();
+  ASSERT_EQ(1, X);
+  ASSERT_EQ(1, Y);
+  ASSERT_EQ(1, Z);
+}
+
+TEST_F(TaskQueueTest, UnOrderedFutures) {
+  ThreadPool TP(1);
+  TaskQueue TQ(TP);
+  std::atomic<int> X = 0;
+  std::atomic<int> Y = 0;
+  std::atomic<int> Z = 0;
+  std::future<void> F1 = TQ.async([&] { ++X; });
+  std::future<void> F2 = TQ.async([&] { ++Y; });
+  std::future<void> F3 = TQ.async([&] { ++Z; });
+
+  F2.wait();
+  ASSERT_EQ(1, X);
+  ASSERT_EQ(1, Y);
+#if !LLVM_ENABLE_THREADS
+  // We can't check this in the LLVM_ENABLE_THREADS case since the work thread
+  // proceeds independently of the main thread, so this may or may not still
+  // be true.
+  ASSERT_EQ(0, Z);
+#endif
+
+  F3.wait();
+  ASSERT_EQ(1, X);
+  ASSERT_EQ(1, Y);
+  ASSERT_EQ(1, Z);
+}
+//
+// TEST_F(TaskQueueTest, Wait) {
+//  // Test that calling wait() on a TaskQueue processes all outstanding work.
+//  TaskQueue TQ;
+//  std::atomic<int> X = 0;
+//  std::atomic<int> Y = 0;
+//  std::atomic<int> Z = 0;
+//  TQ.async([&] { X = 1; });
+//  TQ.async([&] { Y = 1; });
+//  TQ.async([&] { Z = 1; });
+//
+//  TQ.wait();
+//  ASSERT_EQ(1, X);
+//  ASSERT_EQ(1, Y);
+//  ASSERT_EQ(1, Z);
+//}
+//
+// TEST_F(TaskQueueTest, WaitAgain) {
+//  // Test that calling wait() on a TaskQueue and queueing up more work
+//  processes
+//  // the new work as it should.
+//  TaskQueue TQ;
+//  std::atomic<int> X = 0;
+//  std::atomic<int> Y = 0;
+//  std::atomic<int> Z = 0;
+//  TQ.async([&] { ++X; });
+//  TQ.async([&] { ++Y; });
+//  TQ.async([&] { ++Z; });
+//
+//  TQ.wait();
+//  ASSERT_EQ(1, X);
+//  ASSERT_EQ(1, Y);
+//  ASSERT_EQ(1, Z);
+//
+//  TQ.async([&] { ++X; });
+//  TQ.async([&] { ++Y; });
+//  TQ.async([&] { ++Z; });
+//
+//  TQ.wait();
+//  ASSERT_EQ(2, X);
+//  ASSERT_EQ(2, Y);
+//  ASSERT_EQ(2, Z);
+//}
+//
+// TEST_F(TaskQueueTest, QueueWaitAfterFutureWait) {
+//  // Test that waiting on the result of some work and then waiting on the
+//  // entire queue processes each job exactly once, and in the correct
+//  // order.
+//  TaskQueue TQ;
+//  std::atomic<int> X = 0;
+//  std::atomic<int> Y = 0;
+//  std::atomic<int> Z = 0;
+//  std::atomic<int> A = 0;
+//  std::shared_future<void> F1 = TQ.async([&] { ++X; });
+//  std::shared_future<void> F2 = TQ.async([&] { ++Y; });
+//  std::shared_future<void> F3 = TQ.async([&] { ++Z; });
+//  std::shared_future<void> F4 = TQ.async([&] { ++A; });
+//
+//  F2.wait();
+//  ASSERT_EQ(1, X);
+//  ASSERT_EQ(1, Y);
+//#if !LLVM_ENABLE_THREADS
+//  // We can't check this in the LLVM_ENABLE_THREADS case since the work thread
+//  // proceeds independently of the main thread, so this may or may not still
+//  // be true.
+//  ASSERT_EQ(0, Z);
+//  ASSERT_EQ(0, A);
+//#endif
+//
+//  TQ.wait();
+//  ASSERT_EQ(1, X);
+//  ASSERT_EQ(1, Y);
+//  ASSERT_EQ(1, Z);
+//  ASSERT_EQ(1, A);
+//}