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Revert "Add a C++11 ThreadPool implementation in LLVM"

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This reverts commit r255589. Breaks g++

From: Mehdi Amini <mehdi.amini@apple.com>
llvm-svn: 255591
This commit is contained in:
Mehdi Amini 2015-12-15 00:42:44 +00:00
parent dbdd929681
commit 5acecbc1ec
6 changed files with 0 additions and 354 deletions
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113
include/llvm/Support/ThreadPool.h
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@ -1,113 +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:
#ifndef _MSC_VER
using VoidTy = void;
#else
// MSVC 2013 has a bug and can't use std::packaged_task<void()>;
// We force it to use bool(bool) instead.
using VoidTy = bool;
#endif
using TaskTy = std::function<VoidTy(VoidTy)>;
using PackagedTaskTy = std::packaged_task<VoidTy(VoidTy)>;
/// 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<VoidTy> async(Function &&F, Args &&... ArgList) {
auto Task =
std::bind(std::forward<Function>(F), std::forward<Args...>(ArgList...));
#ifndef _MSC_VER
return asyncImpl(std::move(Task));
#else
return asyncImpl([Task] (VoidTy) -> VoidTy { Task(); return VoidTy(); });
#endif
}
/// 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<VoidTy> async(Function &&F) {
#ifndef _MSC_VER
return asyncImpl(std::forward<Function>(F));
#else
return asyncImpl([F] (VoidTy) -> VoidTy { F(); return VoidTy(); });
#endif
}
/// 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<VoidTy> asyncImpl(TaskTy F);
/// Threads in flight
std::vector<llvm::thread> Threads;
/// Tasks waiting for execution in the pool.
std::queue<PackagedTaskTy> 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;
#if LLVM_ENABLE_THREADS // avoids warning for unused variable
/// Signal for the destruction of the pool, asking thread to exit.
bool EnableFlag;
#endif
};
}
#endif // LLVM_SUPPORT_THREAD_POOL_H

2
include/llvm/Support/thread.h
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@ -43,8 +43,6 @@ typedef std::thread thread;
#else // !LLVM_ENABLE_THREADS
#include <utility>
namespace llvm {
struct thread {

1
lib/Support/CMakeLists.txt
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@ -89,7 +89,6 @@ add_llvm_library(LLVMSupport
StringRef.cpp
SystemUtils.cpp
TargetParser.cpp
ThreadPool.cpp
Timer.cpp
ToolOutputFile.cpp
Triple.cpp

146
lib/Support/ThreadPool.cpp
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@ -1,146 +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) {
PackagedTaskTy 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
#ifndef _MSC_VER
Task();
#else
Task(/* unused */ false);
#endif
{
// 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<ThreadPool::VoidTy> ThreadPool::asyncImpl(TaskTy Task) {
/// Wrap the Task in a packaged_task to return a future object.
PackagedTaskTy PackagedTask(std::move(Task));
auto 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) {
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<ThreadPool::VoidTy> 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.
PackagedTaskTy PackagedTask([Future]() { Future.get(); });
Tasks.push(std::move(PackagedTask));
return Future;
}
ThreadPool::~ThreadPool() {
wait();
}
#endif

1
unittests/Support/CMakeLists.txt
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@ -41,7 +41,6 @@ add_llvm_unittest(SupportTests
SwapByteOrderTest.cpp
TargetRegistry.cpp
ThreadLocalTest.cpp
ThreadPool.cpp
TimeValueTest.cpp
TrailingObjectsTest.cpp
UnicodeTest.cpp

91
unittests/Support/ThreadPool.cpp
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@ -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);
}