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d8a3f46e15
Summary: Apparently, when compiling with gcc 5.3.2 for powerpc64, the order of headers is such that it gets an error about std::atomic<> use in ThreadPool.h, since this header is not included explicitly. See also: https://llvm.org/bugs/show_bug.cgi?id=27058 Fix this by including <atomic>. Patch by Bryan Drewery. Reviewers: chandlerc, joker.eph Subscribers: bdrewery, llvm-commits Differential Revision: http://reviews.llvm.org/D18460 llvm-svn: 264335
138 lines
4.1 KiB
C++
138 lines
4.1 KiB
C++
//===-- llvm/Support/ThreadPool.h - A ThreadPool implementation -*- C++ -*-===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This file defines a crude C++11 based thread pool.
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_SUPPORT_THREAD_POOL_H
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#define LLVM_SUPPORT_THREAD_POOL_H
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#include "llvm/Support/thread.h"
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#ifdef _MSC_VER
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// concrt.h depends on eh.h for __uncaught_exception declaration
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// even if we disable exceptions.
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#include <eh.h>
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// Disable warnings from ppltasks.h transitively included by <future>.
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#pragma warning(push)
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#pragma warning(disable:4530)
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#pragma warning(disable:4062)
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#endif
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#include <future>
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#ifdef _MSC_VER
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#pragma warning(pop)
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#endif
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#include <atomic>
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#include <condition_variable>
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#include <functional>
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#include <memory>
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#include <mutex>
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#include <queue>
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#include <utility>
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namespace llvm {
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/// A ThreadPool for asynchronous parallel execution on a defined number of
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/// threads.
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///
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/// The pool keeps a vector of threads alive, waiting on a condition variable
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/// for some work to become available.
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class ThreadPool {
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public:
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#ifndef _MSC_VER
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using VoidTy = void;
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using TaskTy = std::function<void()>;
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using PackagedTaskTy = std::packaged_task<void()>;
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#else
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// MSVC 2013 has a bug and can't use std::packaged_task<void()>;
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// We force it to use bool(bool) instead.
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using VoidTy = bool;
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using TaskTy = std::function<bool(bool)>;
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using PackagedTaskTy = std::packaged_task<bool(bool)>;
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#endif
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/// Construct a pool with the number of core available on the system (or
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/// whatever the value returned by std::thread::hardware_concurrency() is).
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ThreadPool();
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/// Construct a pool of \p ThreadCount threads
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ThreadPool(unsigned ThreadCount);
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/// Blocking destructor: the pool will wait for all the threads to complete.
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~ThreadPool();
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/// Asynchronous submission of a task to the pool. The returned future can be
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/// used to wait for the task to finish and is *non-blocking* on destruction.
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template <typename Function, typename... Args>
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inline std::shared_future<VoidTy> async(Function &&F, Args &&... ArgList) {
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auto Task =
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std::bind(std::forward<Function>(F), std::forward<Args>(ArgList)...);
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#ifndef _MSC_VER
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return asyncImpl(std::move(Task));
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#else
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// This lambda has to be marked mutable because MSVC 2013's std::bind call
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// operator isn't const qualified.
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return asyncImpl([Task](VoidTy) mutable -> VoidTy {
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Task();
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return VoidTy();
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});
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#endif
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}
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/// Asynchronous submission of a task to the pool. The returned future can be
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/// used to wait for the task to finish and is *non-blocking* on destruction.
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template <typename Function>
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inline std::shared_future<VoidTy> async(Function &&F) {
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#ifndef _MSC_VER
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return asyncImpl(std::forward<Function>(F));
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#else
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return asyncImpl([F] (VoidTy) -> VoidTy { F(); return VoidTy(); });
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#endif
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}
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/// Blocking wait for all the threads to complete and the queue to be empty.
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/// It is an error to try to add new tasks while blocking on this call.
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void wait();
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private:
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/// Asynchronous submission of a task to the pool. The returned future can be
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/// used to wait for the task to finish and is *non-blocking* on destruction.
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std::shared_future<VoidTy> asyncImpl(TaskTy F);
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/// Threads in flight
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std::vector<llvm::thread> Threads;
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/// Tasks waiting for execution in the pool.
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std::queue<PackagedTaskTy> Tasks;
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/// Locking and signaling for accessing the Tasks queue.
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std::mutex QueueLock;
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std::condition_variable QueueCondition;
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/// Locking and signaling for job completion
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std::mutex CompletionLock;
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std::condition_variable CompletionCondition;
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/// Keep track of the number of thread actually busy
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std::atomic<unsigned> ActiveThreads;
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#if LLVM_ENABLE_THREADS // avoids warning for unused variable
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/// Signal for the destruction of the pool, asking thread to exit.
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bool EnableFlag;
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#endif
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};
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}
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#endif // LLVM_SUPPORT_THREAD_POOL_H
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