Revert r255444.

It doesn't build on Windows and broke the Windows LLD and LLDB bots:
http://lab.llvm.org:8011/builders/lld-x86_64-win7/builds/27693/steps/build_Lld/logs/stdio
http://lab.llvm.org:8011/builders/lldb-x86-windows-msvc/builds/13468/steps/build/logs/stdio


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@255446 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/Support/ThreadPool.h

@@ -1,95 +0,0 @@
-//===-- llvm/Support/ThreadPool.h - A ThreadPool 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 thread pool.
-//
-//===----------------------------------------------------------------------===//
-
-#ifndef LLVM_SUPPORT_THREAD_POOL_H
-#define LLVM_SUPPORT_THREAD_POOL_H
-
-#include "llvm/Support/thread.h"
-
-#include <condition_variable>
-#include <functional>
-#include <future>
-#include <memory>
-#include <mutex>
-#include <queue>
-#include <utility>
-
-namespace llvm {
-
-/// A ThreadPool for asynchronous parallel execution on a defined number of
-/// threads.
-///
-/// The pool keeps a vector of threads alive, waiting on a condition variable
-/// for some work to become available.
-class ThreadPool {
-public:
-  using TaskTy = std::function<void()>;
-
-  /// Construct a pool with the number of core available on the system (or
-  /// whatever the value returned by std::thread::hardware_concurrency() is).
-  ThreadPool();
-
-  /// Construct a pool of \p ThreadCount threads
-  ThreadPool(unsigned ThreadCount);
-
-  /// Blocking destructor: the pool will wait for all the threads to complete.
-  ~ThreadPool();
-
-  /// Asynchronous submission of a task to the pool. The returned future can be
-  /// used to wait for the task to finish and is *non-blocking* on destruction.
-  template <typename Function, typename... Args>
-  inline std::shared_future<void> async(Function &&F, Args &&... ArgList) {
-    auto Task =
-        std::bind(std::forward<Function>(F), std::forward<Args...>(ArgList...));
-    return asyncImpl(Task);
-  }
-
-  /// Asynchronous submission of a task to the pool. The returned future can be
-  /// used to wait for the task to finish and is *non-blocking* on destruction.
-  template <typename Function>
-  inline std::shared_future<void> async(Function &&F) {
-    return asyncImpl(F);
-  }
-
-  /// Blocking wait for all the threads to complete and the queue to be empty.
-  /// It is an error to try to add new tasks while blocking on this call.
-  void wait();
-
-private:
-  /// Asynchronous submission of a task to the pool. The returned future can be
-  /// used to wait for the task to finish and is *non-blocking* on destruction.
-  std::shared_future<void> asyncImpl(TaskTy f);
-
-  /// Threads in flight
-  std::vector<llvm::thread> Threads;
-
-  /// Tasks waiting for execution in the pool.
-  std::queue<std::packaged_task<void()>> Tasks;
-
-  /// Locking and signaling for accessing the Tasks queue.
-  std::mutex QueueLock;
-  std::condition_variable QueueCondition;
-
-  /// Locking and signaling for job completion
-  std::mutex CompletionLock;
-  std::condition_variable CompletionCondition;
-
-  /// Keep track of the number of thread actually busy
-  std::atomic<unsigned> ActiveThreads;
-
-  /// Signal for the destruction of the pool, asking thread to exit.
-  bool EnableFlag;
-};
-}
-
-#endif // LLVM_SUPPORT_THREAD_POOL_H

include/llvm/Support/thread.h

@@ -43,8 +43,6 @@ typedef std::thread thread;
 
 #else // !LLVM_ENABLE_THREADS
 
-#include <utility>
-
 namespace llvm {
 
 struct thread {

lib/Support/CMakeLists.txt

@@ -89,7 +89,6 @@ add_llvm_library(LLVMSupport
   StringRef.cpp
   SystemUtils.cpp
   TargetParser.cpp
-  ThreadPool.cpp
   Timer.cpp
   ToolOutputFile.cpp
   Triple.cpp

lib/Support/ThreadPool.cpp

@@ -1,143 +0,0 @@
-//==-- llvm/Support/ThreadPool.cpp - A ThreadPool 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 thread pool.
-//
-//===----------------------------------------------------------------------===//
-
-#include "llvm/Support/ThreadPool.h"
-
-#include "llvm/Config/llvm-config.h"
-#include "llvm/Support/raw_ostream.h"
-
-using namespace llvm;
-
-#if LLVM_ENABLE_THREADS
-
-// Default to std::thread::hardware_concurrency
-ThreadPool::ThreadPool() : ThreadPool(std::thread::hardware_concurrency()) {}
-
-ThreadPool::ThreadPool(unsigned ThreadCount)
-    : ActiveThreads(0), EnableFlag(true) {
-  // Create ThreadCount threads that will loop forever, wait on QueueCondition
-  // for tasks to be queued or the Pool to be destroyed.
-  Threads.reserve(ThreadCount);
-  for (unsigned ThreadID = 0; ThreadID < ThreadCount; ++ThreadID) {
-    Threads.emplace_back([&] {
-      while (true) {
-        std::packaged_task<void()> Task;
-        {
-          std::unique_lock<std::mutex> LockGuard(QueueLock);
-          // Wait for tasks to be pushed in the queue
-          QueueCondition.wait(LockGuard,
-                              [&] { return !EnableFlag || !Tasks.empty(); });
-          // Exit condition
-          if (!EnableFlag && Tasks.empty())
-            return;
-          // Yeah, we have a task, grab it and release the lock on the queue
-
-          // We first need to signal that we are active before popping the queue
-          // in order for wait() to properly detect that even if the queue is
-          // empty, there is still a task in flight.
-          {
-            ++ActiveThreads;
-            std::unique_lock<std::mutex> LockGuard(CompletionLock);
-          }
-          Task = std::move(Tasks.front());
-          Tasks.pop();
-        }
-        // Run the task we just grabbed
-        Task();
-
-        {
-          // Adjust `ActiveThreads`, in case someone waits on ThreadPool::wait()
-          std::unique_lock<std::mutex> LockGuard(CompletionLock);
-          --ActiveThreads;
-        }
-
-        // Notify task completion, in case someone waits on ThreadPool::wait()
-        CompletionCondition.notify_all();
-      }
-    });
-  }
-}
-
-void ThreadPool::wait() {
-  // Wait for all threads to complete and the queue to be empty
-  std::unique_lock<std::mutex> LockGuard(CompletionLock);
-  CompletionCondition.wait(LockGuard,
-                           [&] { return Tasks.empty() && !ActiveThreads; });
-}
-
-std::shared_future<void> ThreadPool::asyncImpl(TaskTy Task) {
-  /// Wrap the Task in a packaged_task to return a future object.
-  std::packaged_task<void()> PackagedTask(std::move(Task));
-  std::future<void> Future = PackagedTask.get_future();
-  {
-    // Lock the queue and push the new task
-    std::unique_lock<std::mutex> LockGuard(QueueLock);
-
-    // Don't allow enqueueing after disabling the pool
-    assert(EnableFlag && "Queuing a thread during ThreadPool destruction");
-
-    Tasks.push(std::move(PackagedTask));
-  }
-  QueueCondition.notify_one();
-  return Future.share();
-}
-
-// The destructor joins all threads, waiting for completion.
-ThreadPool::~ThreadPool() {
-  {
-    std::unique_lock<std::mutex> LockGuard(QueueLock);
-    EnableFlag = false;
-  }
-  QueueCondition.notify_all();
-  for (auto &Worker : Threads)
-    Worker.join();
-}
-
-#else // LLVM_ENABLE_THREADS Disabled
-
-ThreadPool::ThreadPool() : ThreadPool(0) {}
-
-// No threads are launched, issue a warning if ThreadCount is not 0
-ThreadPool::ThreadPool(unsigned ThreadCount)
-    : ActiveThreads(0), EnableFlag(true) {
-  if (ThreadCount) {
-    errs() << "Warning: request a ThreadPool with " << ThreadCount
-           << " threads, but LLVM_ENABLE_THREADS has been turned off\n";
-  }
-}
-
-void ThreadPool::wait() {
-  // Sequential implementation running the tasks
-  while (!Tasks.empty()) {
-    auto Task = std::move(Tasks.front());
-    Tasks.pop();
-    Task();
-  }
-}
-
-std::shared_future<void> ThreadPool::asyncImpl(TaskTy Task) {
-  // Get a Future with launch::deferred execution using std::async
-  auto Future = std::async(std::launch::deferred, std::move(Task)).share();
-  // Wrap the future so that both ThreadPool::wait() can operate and the
-  // returned future can be sync'ed on.
-  std::packaged_task<void()> PackagedTask([Future]() { Future.get(); });
-  Tasks.push(std::move(PackagedTask));
-  return Future;
-}
-
-ThreadPool::~ThreadPool() {
-  EnableFlag = false;
-  wait();
-}
-
-#endif

unittests/Support/CMakeLists.txt

@@ -41,7 +41,6 @@ add_llvm_unittest(SupportTests
   SwapByteOrderTest.cpp
   TargetRegistry.cpp
   ThreadLocalTest.cpp
-  ThreadPool.cpp
   TimeValueTest.cpp
   TrailingObjectsTest.cpp
   UnicodeTest.cpp

unittests/Support/ThreadPool.cpp

@@ -1,91 +0,0 @@
-//========- unittests/Support/ThreadPools.cpp - ThreadPools.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/ThreadPool.h"
-
-#include "llvm/ADT/STLExtras.h"
-
-#include "gtest/gtest.h"
-
-using namespace llvm;
-using namespace std::chrono;
-
-/// Try best to make this thread not progress faster than the main thread
-static void yield() {
-#ifdef LLVM_ENABLE_THREADS
-  std::this_thread::yield();
-#endif
-  std::this_thread::sleep_for(milliseconds(200));
-#ifdef LLVM_ENABLE_THREADS
-  std::this_thread::yield();
-#endif
-}
-
-TEST(ThreadPoolTest, AsyncBarrier) {
-  // test that async & barrier work together properly.
-
-  std::atomic_int checked_in{0};
-
-  ThreadPool Pool;
-  for (size_t i = 0; i < 5; ++i) {
-    Pool.async([&checked_in, i] {
-      yield();
-      ++checked_in;
-    });
-  }
-  ASSERT_EQ(0, checked_in);
-  Pool.wait();
-  ASSERT_EQ(5, checked_in);
-}
-
-TEST(ThreadPoolTest, Async) {
-  ThreadPool Pool;
-  std::atomic_int i{0};
-  // sleep here just to ensure that the not-equal is correct.
-  Pool.async([&i] {
-    yield();
-    ++i;
-  });
-  Pool.async([&i] { ++i; });
-  ASSERT_NE(2, i.load());
-  Pool.wait();
-  ASSERT_EQ(2, i.load());
-}
-
-TEST(ThreadPoolTest, GetFuture) {
-  ThreadPool Pool;
-  std::atomic_int i{0};
-  // sleep here just to ensure that the not-equal is correct.
-  Pool.async([&i] {
-    yield();
-    ++i;
-  });
-  // Force the future using get()
-  Pool.async([&i] { ++i; }).get();
-  ASSERT_NE(2, i.load());
-  Pool.wait();
-  ASSERT_EQ(2, i.load());
-}
-
-TEST(ThreadPoolTest, PoolDestruction) {
-  // Test that we are waiting on destruction
-  std::atomic_int checked_in{0};
-
-  {
-    ThreadPool Pool;
-    for (size_t i = 0; i < 5; ++i) {
-      Pool.async([&checked_in, i] {
-        yield();
-        ++checked_in;
-      });
-    }
-    ASSERT_EQ(0, checked_in);
-  }
-  ASSERT_EQ(5, checked_in);
-}