Index: lld/CMakeLists.txt
===================================================================
--- lld/CMakeLists.txt
+++ lld/CMakeLists.txt
@@ -192,7 +192,6 @@
   "Build the lld tools. If OFF, just generate build targets." ON)
 
 if (MSVC)
-  add_definitions(-wd4530) # Suppress 'warning C4530: C++ exception handler used, but unwind semantics are not enabled.'
   add_definitions(-wd4062) # Suppress 'warning C4062: enumerator X in switch of enum Y is not handled' from system header.
 endif()
 
Index: lld/COFF/ICF.cpp
===================================================================
--- lld/COFF/ICF.cpp
+++ lld/COFF/ICF.cpp
@@ -21,9 +21,9 @@
 #include "Chunks.h"
 #include "Error.h"
 #include "Symbols.h"
-#include "lld/Core/Parallel.h"
 #include "llvm/ADT/Hashing.h"
 #include "llvm/Support/Debug.h"
+#include "llvm/Support/Parallel.h"
 #include "llvm/Support/raw_ostream.h"
 #include <algorithm>
 #include <atomic>
Index: lld/COFF/MapFile.cpp
===================================================================
--- lld/COFF/MapFile.cpp
+++ lld/COFF/MapFile.cpp
@@ -25,7 +25,7 @@
 #include "Symbols.h"
 #include "Writer.h"
 
-#include "lld/Core/Parallel.h"
+#include "llvm/Support/Parallel.h"
 #include "llvm/Support/raw_ostream.h"
 
 using namespace llvm;
Index: lld/COFF/Writer.cpp
===================================================================
--- lld/COFF/Writer.cpp
+++ lld/COFF/Writer.cpp
@@ -17,13 +17,13 @@
 #include "PDB.h"
 #include "SymbolTable.h"
 #include "Symbols.h"
-#include "lld/Core/Parallel.h"
 #include "llvm/ADT/DenseMap.h"
 #include "llvm/ADT/STLExtras.h"
 #include "llvm/ADT/StringSwitch.h"
 #include "llvm/Support/Debug.h"
 #include "llvm/Support/Endian.h"
 #include "llvm/Support/FileOutputBuffer.h"
+#include "llvm/Support/Parallel.h"
 #include "llvm/Support/RandomNumberGenerator.h"
 #include "llvm/Support/raw_ostream.h"
 #include <algorithm>
Index: lld/ELF/Threads.h
===================================================================
--- lld/ELF/Threads.h
+++ lld/ELF/Threads.h
@@ -61,7 +61,7 @@
 
 #include "Config.h"
 
-#include "lld/Core/Parallel.h"
+#include "llvm/Support/Parallel.h"
 #include <algorithm>
 #include <functional>
 
@@ -71,7 +71,7 @@
 template <class IterTy, class FuncTy>
 void parallelForEach(IterTy Begin, IterTy End, FuncTy Fn) {
   if (Config->Threads)
-    parallel_for_each(Begin, End, Fn);
+    llvm::parallel_for_each(Begin, End, Fn);
   else
     std::for_each(Begin, End, Fn);
 }
@@ -79,7 +79,7 @@
 inline void parallelFor(size_t Begin, size_t End,
                         std::function<void(size_t)> Fn) {
   if (Config->Threads) {
-    parallel_for(Begin, End, Fn);
+    llvm::parallel_for(Begin, End, Fn);
   } else {
     for (size_t I = Begin; I < End; ++I)
       Fn(I);
Index: lld/include/lld/Core/Parallel.h
===================================================================
--- lld/include/lld/Core/Parallel.h
+++ /dev/null
@@ -1,335 +0,0 @@
-//===- lld/Core/Parallel.h - Parallel utilities ---------------------------===//
-//
-//                             The LLVM Linker
-//
-// This file is distributed under the University of Illinois Open Source
-// License. See LICENSE.TXT for details.
-//
-//===----------------------------------------------------------------------===//
-
-#ifndef LLD_CORE_PARALLEL_H
-#define LLD_CORE_PARALLEL_H
-
-#include "lld/Core/Instrumentation.h"
-#include "lld/Core/LLVM.h"
-#include "llvm/Support/MathExtras.h"
-#include "llvm/Support/thread.h"
-
-#include <algorithm>
-#include <atomic>
-#include <condition_variable>
-#include <mutex>
-#include <stack>
-
-#if defined(_MSC_VER) && LLVM_ENABLE_THREADS
-#include <concrt.h>
-#include <ppl.h>
-#endif
-
-namespace lld {
-/// \brief Allows one or more threads to wait on a potentially unknown number of
-///   events.
-///
-/// A latch starts at \p count. inc() increments this, and dec() decrements it.
-/// All calls to sync() will block while the count is not 0.
-///
-/// Calling dec() on a Latch with a count of 0 has undefined behaivor.
-class Latch {
-  uint32_t _count;
-  mutable std::mutex _condMut;
-  mutable std::condition_variable _cond;
-
-public:
-  explicit Latch(uint32_t count = 0) : _count(count) {}
-  ~Latch() { sync(); }
-
-  void inc() {
-    std::unique_lock<std::mutex> lock(_condMut);
-    ++_count;
-  }
-
-  void dec() {
-    std::unique_lock<std::mutex> lock(_condMut);
-    if (--_count == 0)
-      _cond.notify_all();
-  }
-
-  void sync() const {
-    std::unique_lock<std::mutex> lock(_condMut);
-    _cond.wait(lock, [&] {
-      return _count == 0;
-    });
-  }
-};
-
-// Classes in this namespace are implementation details of this header.
-namespace internal {
-
-/// \brief An abstract class that takes closures and runs them asynchronously.
-class Executor {
-public:
-  virtual ~Executor() = default;
-  virtual void add(std::function<void()> func) = 0;
-};
-
-#if !defined(LLVM_ENABLE_THREADS) || LLVM_ENABLE_THREADS == 0
-class SyncExecutor : public Executor {
-public:
-  virtual void add(std::function<void()> func) {
-    func();
-  }
-};
-
-inline Executor *getDefaultExecutor() {
-  static SyncExecutor exec;
-  return &exec;
-}
-#elif defined(_MSC_VER)
-/// \brief An Executor that runs tasks via ConcRT.
-class ConcRTExecutor : public Executor {
-  struct Taskish {
-    Taskish(std::function<void()> task) : _task(task) {}
-
-    std::function<void()> _task;
-
-    static void run(void *p) {
-      Taskish *self = static_cast<Taskish *>(p);
-      self->_task();
-      concurrency::Free(self);
-    }
-  };
-
-public:
-  virtual void add(std::function<void()> func) {
-    Concurrency::CurrentScheduler::ScheduleTask(Taskish::run,
-        new (concurrency::Alloc(sizeof(Taskish))) Taskish(func));
-  }
-};
-
-inline Executor *getDefaultExecutor() {
-  static ConcRTExecutor exec;
-  return &exec;
-}
-#else
-/// \brief An implementation of an Executor that runs closures on a thread pool
-///   in filo order.
-class ThreadPoolExecutor : public Executor {
-public:
-  explicit ThreadPoolExecutor(unsigned threadCount =
-                                  std::thread::hardware_concurrency())
-      : _stop(false), _done(threadCount) {
-    // Spawn all but one of the threads in another thread as spawning threads
-    // can take a while.
-    std::thread([&, threadCount] {
-      for (size_t i = 1; i < threadCount; ++i) {
-        std::thread([=] {
-          work();
-        }).detach();
-      }
-      work();
-    }).detach();
-  }
-
-  ~ThreadPoolExecutor() override {
-    std::unique_lock<std::mutex> lock(_mutex);
-    _stop = true;
-    lock.unlock();
-    _cond.notify_all();
-    // Wait for ~Latch.
-  }
-
-  void add(std::function<void()> f) override {
-    std::unique_lock<std::mutex> lock(_mutex);
-    _workStack.push(f);
-    lock.unlock();
-    _cond.notify_one();
-  }
-
-private:
-  void work() {
-    while (true) {
-      std::unique_lock<std::mutex> lock(_mutex);
-      _cond.wait(lock, [&] {
-        return _stop || !_workStack.empty();
-      });
-      if (_stop)
-        break;
-      auto task = _workStack.top();
-      _workStack.pop();
-      lock.unlock();
-      task();
-    }
-    _done.dec();
-  }
-
-  std::atomic<bool> _stop;
-  std::stack<std::function<void()>> _workStack;
-  std::mutex _mutex;
-  std::condition_variable _cond;
-  Latch _done;
-};
-
-inline Executor *getDefaultExecutor() {
-  static ThreadPoolExecutor exec;
-  return &exec;
-}
-#endif
-
-}  // namespace internal
-
-/// \brief Allows launching a number of tasks and waiting for them to finish
-///   either explicitly via sync() or implicitly on destruction.
-class TaskGroup {
-  Latch _latch;
-
-public:
-  void spawn(std::function<void()> f) {
-    _latch.inc();
-    internal::getDefaultExecutor()->add([&, f] {
-      f();
-      _latch.dec();
-    });
-  }
-
-  void sync() const { _latch.sync(); }
-};
-
-#if !defined(LLVM_ENABLE_THREADS) || LLVM_ENABLE_THREADS == 0
-template <class RandomAccessIterator, class Comp>
-void parallel_sort(
-    RandomAccessIterator start, RandomAccessIterator end,
-    const Comp &comp = std::less<
-        typename std::iterator_traits<RandomAccessIterator>::value_type>()) {
-  std::sort(start, end, comp);
-}
-#elif defined(_MSC_VER)
-// Use ppl parallel_sort on Windows.
-template <class RandomAccessIterator, class Comp>
-void parallel_sort(
-    RandomAccessIterator start, RandomAccessIterator end,
-    const Comp &comp = std::less<
-        typename std::iterator_traits<RandomAccessIterator>::value_type>()) {
-  concurrency::parallel_sort(start, end, comp);
-}
-#else
-namespace detail {
-const ptrdiff_t minParallelSize = 1024;
-
-/// \brief Inclusive median.
-template <class RandomAccessIterator, class Comp>
-RandomAccessIterator medianOf3(RandomAccessIterator start,
-                               RandomAccessIterator end, const Comp &comp) {
-  RandomAccessIterator mid = start + (std::distance(start, end) / 2);
-  return comp(*start, *(end - 1))
-         ? (comp(*mid, *(end - 1)) ? (comp(*start, *mid) ? mid : start)
-                                   : end - 1)
-         : (comp(*mid, *start) ? (comp(*(end - 1), *mid) ? mid : end - 1)
-                               : start);
-}
-
-template <class RandomAccessIterator, class Comp>
-void parallel_quick_sort(RandomAccessIterator start, RandomAccessIterator end,
-                         const Comp &comp, TaskGroup &tg, size_t depth) {
-  // Do a sequential sort for small inputs.
-  if (std::distance(start, end) < detail::minParallelSize || depth == 0) {
-    std::sort(start, end, comp);
-    return;
-  }
-
-  // Partition.
-  auto pivot = medianOf3(start, end, comp);
-  // Move pivot to end.
-  std::swap(*(end - 1), *pivot);
-  pivot = std::partition(start, end - 1, [&comp, end](decltype(*start) v) {
-    return comp(v, *(end - 1));
-  });
-  // Move pivot to middle of partition.
-  std::swap(*pivot, *(end - 1));
-
-  // Recurse.
-  tg.spawn([=, &comp, &tg] {
-    parallel_quick_sort(start, pivot, comp, tg, depth - 1);
-  });
-  parallel_quick_sort(pivot + 1, end, comp, tg, depth - 1);
-}
-}
-
-template <class RandomAccessIterator, class Comp>
-void parallel_sort(
-    RandomAccessIterator start, RandomAccessIterator end,
-    const Comp &comp = std::less<
-        typename std::iterator_traits<RandomAccessIterator>::value_type>()) {
-  TaskGroup tg;
-  detail::parallel_quick_sort(start, end, comp, tg,
-                              llvm::Log2_64(std::distance(start, end)) + 1);
-}
-#endif
-
-template <class T> void parallel_sort(T *start, T *end) {
-  parallel_sort(start, end, std::less<T>());
-}
-
-#if !defined(LLVM_ENABLE_THREADS) || LLVM_ENABLE_THREADS == 0
-template <class IterTy, class FuncTy>
-void parallel_for_each(IterTy Begin, IterTy End, FuncTy Fn) {
-  std::for_each(Begin, End, Fn);
-}
-
-template <class IndexTy, class FuncTy>
-void parallel_for(IndexTy Begin, IndexTy End, FuncTy Fn) {
-  for (IndexTy I = Begin; I != End; ++I)
-    Fn(I);
-}
-#elif defined(_MSC_VER)
-// Use ppl parallel_for_each on Windows.
-template <class IterTy, class FuncTy>
-void parallel_for_each(IterTy Begin, IterTy End, FuncTy Fn) {
-  concurrency::parallel_for_each(Begin, End, Fn);
-}
-
-template <class IndexTy, class FuncTy>
-void parallel_for(IndexTy Begin, IndexTy End, FuncTy Fn) {
-  concurrency::parallel_for(Begin, End, Fn);
-}
-#else
-template <class IterTy, class FuncTy>
-void parallel_for_each(IterTy Begin, IterTy End, FuncTy Fn) {
-  // TaskGroup has a relatively high overhead, so we want to reduce
-  // the number of spawn() calls. We'll create up to 1024 tasks here.
-  // (Note that 1024 is an arbitrary number. This code probably needs
-  // improving to take the number of available cores into account.)
-  ptrdiff_t TaskSize = std::distance(Begin, End) / 1024;
-  if (TaskSize == 0)
-    TaskSize = 1;
-
-  TaskGroup Tg;
-  while (TaskSize <= std::distance(Begin, End)) {
-    Tg.spawn([=, &Fn] { std::for_each(Begin, Begin + TaskSize, Fn); });
-    Begin += TaskSize;
-  }
-  Tg.spawn([=, &Fn] { std::for_each(Begin, End, Fn); });
-}
-
-template <class IndexTy, class FuncTy>
-void parallel_for(IndexTy Begin, IndexTy End, FuncTy Fn) {
-  ptrdiff_t TaskSize = (End - Begin) / 1024;
-  if (TaskSize == 0)
-    TaskSize = 1;
-
-  TaskGroup Tg;
-  IndexTy I = Begin;
-  for (; I + TaskSize < End; I += TaskSize) {
-    Tg.spawn([=, &Fn] {
-      for (IndexTy J = I, E = I + TaskSize; J != E; ++J)
-        Fn(J);
-    });
-  }
-  Tg.spawn([=, &Fn] {
-    for (IndexTy J = I; J < End; ++J)
-      Fn(J);
-  });
-}
-#endif
-} // end namespace lld
-
-#endif // LLD_CORE_PARALLEL_H
Index: lld/lib/ReaderWriter/MachO/LayoutPass.cpp
===================================================================
--- lld/lib/ReaderWriter/MachO/LayoutPass.cpp
+++ lld/lib/ReaderWriter/MachO/LayoutPass.cpp
@@ -9,12 +9,12 @@
 
 #include "LayoutPass.h"
 #include "lld/Core/Instrumentation.h"
-#include "lld/Core/Parallel.h"
 #include "lld/Core/PassManager.h"
 #include "lld/ReaderWriter/MachOLinkingContext.h"
 #include "llvm/ADT/STLExtras.h"
 #include "llvm/ADT/Twine.h"
 #include "llvm/Support/Debug.h"
+#include "llvm/Support/Parallel.h"
 #include <algorithm>
 #include <set>
 #include <utility>
@@ -461,7 +461,8 @@
   });
 
   std::vector<LayoutPass::SortKey> vec = decorate(atomRange);
-  parallel_sort(vec.begin(), vec.end(),
+  llvm::parallel_sort(
+      vec.begin(), vec.end(),
       [&](const LayoutPass::SortKey &l, const LayoutPass::SortKey &r) -> bool {
         return compareAtoms(l, r, _customSorter);
       });
Index: lld/unittests/CMakeLists.txt
===================================================================
--- lld/unittests/CMakeLists.txt
+++ lld/unittests/CMakeLists.txt
@@ -12,6 +12,5 @@
   target_link_libraries(${test_dirname} ${LLVM_COMMON_LIBS})
 endfunction()
 
-add_subdirectory(CoreTests)
 add_subdirectory(DriverTests)
 add_subdirectory(MachOTests)
Index: lld/unittests/CoreTests/CMakeLists.txt
===================================================================
--- lld/unittests/CoreTests/CMakeLists.txt
+++ /dev/null
@@ -1,7 +0,0 @@
-add_lld_unittest(CoreTests
-  ParallelTest.cpp
-  )
-
-target_link_libraries(CoreTests
-  ${LLVM_PTHREAD_LIB}
-  )
Index: lld/unittests/CoreTests/ParallelTest.cpp
===================================================================
--- lld/unittests/CoreTests/ParallelTest.cpp
+++ /dev/null
@@ -1,46 +0,0 @@
-//===- lld/unittest/ParallelTest.cpp --------------------------------------===//
-//
-//                     The LLVM Compiler Infrastructure
-//
-// This file is distributed under the University of Illinois Open Source
-// License. See LICENSE.TXT for details.
-//
-//===----------------------------------------------------------------------===//
-///
-/// \file
-/// \brief Parallel.h unit tests.
-///
-//===----------------------------------------------------------------------===//
-
-#include "gtest/gtest.h"
-#include "lld/Core/Parallel.h"
-#include <array>
-#include <random>
-
-uint32_t array[1024 * 1024];
-
-TEST(Parallel, sort) {
-  std::mt19937 randEngine;
-  std::uniform_int_distribution<uint32_t> dist;
-
-  for (auto &i : array)
-    i = dist(randEngine);
-
-  lld::parallel_sort(std::begin(array), std::end(array));
-  ASSERT_TRUE(std::is_sorted(std::begin(array), std::end(array)));
-}
-
-TEST(Parallel, parallel_for) {
-  // We need to test the case with a TaskSize > 1. We are white-box testing
-  // here. The TaskSize is calculated as (End - Begin) / 1024 at the time of
-  // writing.
-  uint32_t range[2050];
-  std::fill(range, range + 2050, 1);
-  lld::parallel_for(0, 2049, [&range](size_t I) { ++range[I]; });
-
-  uint32_t expected[2049];
-  std::fill(expected, expected + 2049, 2);
-  ASSERT_TRUE(std::equal(range, range + 2049, expected));
-  // Check that we don't write past the end of the requested range.
-  ASSERT_EQ(range[2049], 1u);
-}
Index: llvm/include/llvm/Support/Parallel.h
===================================================================
--- /dev/null
+++ llvm/include/llvm/Support/Parallel.h
@@ -0,0 +1,331 @@
+//===- llvm/Support/Parallel.h - Parallel utilities -----------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_SUPPORT_PARALLEL_H
+#define LLVM_SUPPORT_PARALLEL_H
+
+#include "llvm/Support/MathExtras.h"
+#include "llvm/Support/thread.h"
+
+#include <algorithm>
+#include <atomic>
+#include <condition_variable>
+#include <mutex>
+#include <stack>
+
+#if defined(_MSC_VER) && LLVM_ENABLE_THREADS
+// Suppress 'warning C4530: C++ exception handler used, but unwind semantics are
+// not enabled.'
+#pragma warning(push)
+#pragma warning(disable : 4530)
+
+#include <concrt.h>
+#include <ppl.h>
+#pragma warning(pop)
+#endif
+
+namespace llvm {
+/// \brief Allows one or more threads to wait on a potentially unknown number of
+///   events.
+///
+/// A latch starts at \p count. inc() increments this, and dec() decrements it.
+/// All calls to sync() will block while the count is not 0.
+///
+/// Calling dec() on a Latch with a count of 0 has undefined behaivor.
+class Latch {
+  uint32_t _count;
+  mutable std::mutex _condMut;
+  mutable std::condition_variable _cond;
+
+public:
+  explicit Latch(uint32_t count = 0) : _count(count) {}
+  ~Latch() { sync(); }
+
+  void inc() {
+    std::unique_lock<std::mutex> lock(_condMut);
+    ++_count;
+  }
+
+  void dec() {
+    std::unique_lock<std::mutex> lock(_condMut);
+    if (--_count == 0)
+      _cond.notify_all();
+  }
+
+  void sync() const {
+    std::unique_lock<std::mutex> lock(_condMut);
+    _cond.wait(lock, [&] { return _count == 0; });
+  }
+};
+
+// Classes in this namespace are implementation details of this header.
+namespace internal {
+
+/// \brief An abstract class that takes closures and runs them asynchronously.
+class Executor {
+public:
+  virtual ~Executor() = default;
+  virtual void add(std::function<void()> func) = 0;
+};
+
+#if !defined(LLVM_ENABLE_THREADS) || LLVM_ENABLE_THREADS == 0
+class SyncExecutor : public Executor {
+public:
+  virtual void add(std::function<void()> func) { func(); }
+};
+
+inline Executor *getDefaultExecutor() {
+  static SyncExecutor exec;
+  return &exec;
+}
+#elif defined(_MSC_VER)
+/// \brief An Executor that runs tasks via ConcRT.
+class ConcRTExecutor : public Executor {
+  struct Taskish {
+    Taskish(std::function<void()> task) : _task(task) {}
+
+    std::function<void()> _task;
+
+    static void run(void *p) {
+      Taskish *self = static_cast<Taskish *>(p);
+      self->_task();
+      concurrency::Free(self);
+    }
+  };
+
+public:
+  virtual void add(std::function<void()> func) {
+    Concurrency::CurrentScheduler::ScheduleTask(
+        Taskish::run, new (concurrency::Alloc(sizeof(Taskish))) Taskish(func));
+  }
+};
+
+inline Executor *getDefaultExecutor() {
+  static ConcRTExecutor exec;
+  return &exec;
+}
+#else
+/// \brief An implementation of an Executor that runs closures on a thread pool
+///   in filo order.
+class ThreadPoolExecutor : public Executor {
+public:
+  explicit ThreadPoolExecutor(
+      unsigned threadCount = std::thread::hardware_concurrency())
+      : _stop(false), _done(threadCount) {
+    // Spawn all but one of the threads in another thread as spawning threads
+    // can take a while.
+    std::thread([&, threadCount] {
+      for (size_t i = 1; i < threadCount; ++i) {
+        std::thread([=] { work(); }).detach();
+      }
+      work();
+    }).detach();
+  }
+
+  ~ThreadPoolExecutor() override {
+    std::unique_lock<std::mutex> lock(_mutex);
+    _stop = true;
+    lock.unlock();
+    _cond.notify_all();
+    // Wait for ~Latch.
+  }
+
+  void add(std::function<void()> f) override {
+    std::unique_lock<std::mutex> lock(_mutex);
+    _workStack.push(f);
+    lock.unlock();
+    _cond.notify_one();
+  }
+
+private:
+  void work() {
+    while (true) {
+      std::unique_lock<std::mutex> lock(_mutex);
+      _cond.wait(lock, [&] { return _stop || !_workStack.empty(); });
+      if (_stop)
+        break;
+      auto task = _workStack.top();
+      _workStack.pop();
+      lock.unlock();
+      task();
+    }
+    _done.dec();
+  }
+
+  std::atomic<bool> _stop;
+  std::stack<std::function<void()>> _workStack;
+  std::mutex _mutex;
+  std::condition_variable _cond;
+  Latch _done;
+};
+
+inline Executor *getDefaultExecutor() {
+  static ThreadPoolExecutor exec;
+  return &exec;
+}
+#endif
+
+} // namespace internal
+
+/// \brief Allows launching a number of tasks and waiting for them to finish
+///   either explicitly via sync() or implicitly on destruction.
+class TaskGroup {
+  Latch _latch;
+
+public:
+  void spawn(std::function<void()> f) {
+    _latch.inc();
+    internal::getDefaultExecutor()->add([&, f] {
+      f();
+      _latch.dec();
+    });
+  }
+
+  void sync() const { _latch.sync(); }
+};
+
+#if !defined(LLVM_ENABLE_THREADS) || LLVM_ENABLE_THREADS == 0
+template <class RandomAccessIterator, class Comp>
+void parallel_sort(
+    RandomAccessIterator start, RandomAccessIterator end,
+    const Comp &comp = std::less<
+        typename std::iterator_traits<RandomAccessIterator>::value_type>()) {
+  std::sort(start, end, comp);
+}
+#elif defined(_MSC_VER)
+// Use ppl parallel_sort on Windows.
+template <class RandomAccessIterator, class Comp>
+void parallel_sort(
+    RandomAccessIterator start, RandomAccessIterator end,
+    const Comp &comp = std::less<
+        typename std::iterator_traits<RandomAccessIterator>::value_type>()) {
+  concurrency::parallel_sort(start, end, comp);
+}
+#else
+namespace detail {
+const ptrdiff_t minParallelSize = 1024;
+
+/// \brief Inclusive median.
+template <class RandomAccessIterator, class Comp>
+RandomAccessIterator medianOf3(RandomAccessIterator start,
+                               RandomAccessIterator end, const Comp &comp) {
+  RandomAccessIterator mid = start + (std::distance(start, end) / 2);
+  return comp(*start, *(end - 1))
+             ? (comp(*mid, *(end - 1)) ? (comp(*start, *mid) ? mid : start)
+                                       : end - 1)
+             : (comp(*mid, *start) ? (comp(*(end - 1), *mid) ? mid : end - 1)
+                                   : start);
+}
+
+template <class RandomAccessIterator, class Comp>
+void parallel_quick_sort(RandomAccessIterator start, RandomAccessIterator end,
+                         const Comp &comp, TaskGroup &tg, size_t depth) {
+  // Do a sequential sort for small inputs.
+  if (std::distance(start, end) < detail::minParallelSize || depth == 0) {
+    std::sort(start, end, comp);
+    return;
+  }
+
+  // Partition.
+  auto pivot = medianOf3(start, end, comp);
+  // Move pivot to end.
+  std::swap(*(end - 1), *pivot);
+  pivot = std::partition(start, end - 1, [&comp, end](decltype(*start) v) {
+    return comp(v, *(end - 1));
+  });
+  // Move pivot to middle of partition.
+  std::swap(*pivot, *(end - 1));
+
+  // Recurse.
+  tg.spawn([=, &comp, &tg] {
+    parallel_quick_sort(start, pivot, comp, tg, depth - 1);
+  });
+  parallel_quick_sort(pivot + 1, end, comp, tg, depth - 1);
+}
+}
+
+template <class RandomAccessIterator, class Comp>
+void parallel_sort(
+    RandomAccessIterator start, RandomAccessIterator end,
+    const Comp &comp = std::less<
+        typename std::iterator_traits<RandomAccessIterator>::value_type>()) {
+  TaskGroup tg;
+  detail::parallel_quick_sort(start, end, comp, tg,
+                              llvm::Log2_64(std::distance(start, end)) + 1);
+}
+#endif
+
+template <class T> void parallel_sort(T *start, T *end) {
+  parallel_sort(start, end, std::less<T>());
+}
+
+#if !defined(LLVM_ENABLE_THREADS) || LLVM_ENABLE_THREADS == 0
+template <class IterTy, class FuncTy>
+void parallel_for_each(IterTy Begin, IterTy End, FuncTy Fn) {
+  std::for_each(Begin, End, Fn);
+}
+
+template <class IndexTy, class FuncTy>
+void parallel_for(IndexTy Begin, IndexTy End, FuncTy Fn) {
+  for (IndexTy I = Begin; I != End; ++I)
+    Fn(I);
+}
+#elif defined(_MSC_VER)
+// Use ppl parallel_for_each on Windows.
+template <class IterTy, class FuncTy>
+void parallel_for_each(IterTy Begin, IterTy End, FuncTy Fn) {
+  concurrency::parallel_for_each(Begin, End, Fn);
+}
+
+template <class IndexTy, class FuncTy>
+void parallel_for(IndexTy Begin, IndexTy End, FuncTy Fn) {
+  concurrency::parallel_for(Begin, End, Fn);
+}
+#else
+template <class IterTy, class FuncTy>
+void parallel_for_each(IterTy Begin, IterTy End, FuncTy Fn) {
+  // TaskGroup has a relatively high overhead, so we want to reduce
+  // the number of spawn() calls. We'll create up to 1024 tasks here.
+  // (Note that 1024 is an arbitrary number. This code probably needs
+  // improving to take the number of available cores into account.)
+  ptrdiff_t TaskSize = std::distance(Begin, End) / 1024;
+  if (TaskSize == 0)
+    TaskSize = 1;
+
+  TaskGroup Tg;
+  while (TaskSize <= std::distance(Begin, End)) {
+    Tg.spawn([=, &Fn] { std::for_each(Begin, Begin + TaskSize, Fn); });
+    Begin += TaskSize;
+  }
+  Tg.spawn([=, &Fn] { std::for_each(Begin, End, Fn); });
+}
+
+template <class IndexTy, class FuncTy>
+void parallel_for(IndexTy Begin, IndexTy End, FuncTy Fn) {
+  ptrdiff_t TaskSize = (End - Begin) / 1024;
+  if (TaskSize == 0)
+    TaskSize = 1;
+
+  TaskGroup Tg;
+  IndexTy I = Begin;
+  for (; I + TaskSize < End; I += TaskSize) {
+    Tg.spawn([=, &Fn] {
+      for (IndexTy J = I, E = I + TaskSize; J != E; ++J)
+        Fn(J);
+    });
+  }
+  Tg.spawn([=, &Fn] {
+    for (IndexTy J = I; J < End; ++J)
+      Fn(J);
+  });
+}
+#endif
+} // end namespace llvm
+
+#endif // LLVM_SUPPORT_PARALLEL_H
Index: llvm/unittests/Support/CMakeLists.txt
===================================================================
--- llvm/unittests/Support/CMakeLists.txt
+++ llvm/unittests/Support/CMakeLists.txt
@@ -36,6 +36,7 @@
   MemoryBufferTest.cpp
   MemoryTest.cpp
   NativeFormatTests.cpp
+  ParallelTest.cpp
   Path.cpp
   ProcessTest.cpp
   ProgramTest.cpp
@@ -65,7 +66,7 @@
   xxhashTest.cpp
   )
 
-# ManagedStatic.cpp uses <pthread>.
+# ManagedStatic and Parallel uses <pthread>.
 target_link_libraries(SupportTests ${LLVM_PTHREAD_LIB})
 
 add_subdirectory(DynamicLibrary)
Index: llvm/unittests/Support/ParallelTest.cpp
===================================================================
--- /dev/null
+++ llvm/unittests/Support/ParallelTest.cpp
@@ -0,0 +1,46 @@
+//===- lld/unittest/ParallelTest.cpp --------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file
+/// \brief Parallel.h unit tests.
+///
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Support/Parallel.h"
+#include "gtest/gtest.h"
+#include <array>
+#include <random>
+
+uint32_t array[1024 * 1024];
+
+TEST(Parallel, sort) {
+  std::mt19937 randEngine;
+  std::uniform_int_distribution<uint32_t> dist;
+
+  for (auto &i : array)
+    i = dist(randEngine);
+
+  llvm::parallel_sort(std::begin(array), std::end(array));
+  ASSERT_TRUE(std::is_sorted(std::begin(array), std::end(array)));
+}
+
+TEST(Parallel, parallel_for) {
+  // We need to test the case with a TaskSize > 1. We are white-box testing
+  // here. The TaskSize is calculated as (End - Begin) / 1024 at the time of
+  // writing.
+  uint32_t range[2050];
+  std::fill(range, range + 2050, 1);
+  llvm::parallel_for(0, 2049, [&range](size_t I) { ++range[I]; });
+
+  uint32_t expected[2049];
+  std::fill(expected, expected + 2049, 2);
+  ASSERT_TRUE(std::equal(range, range + 2049, expected));
+  // Check that we don't write past the end of the requested range.
+  ASSERT_EQ(range[2049], 1u);
+}