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to reflect the new license. We understand that people may be surprised that we're moving the header entirely to discuss the new license. We checked this carefully with the Foundation's lawyer and we believe this is the correct approach. Essentially, all code in the project is now made available by the LLVM project under our new license, so you will see that the license headers include that license only. Some of our contributors have contributed code under our old license, and accordingly, we have retained a copy of our old license notice in the top-level files in each project and repository. llvm-svn: 351636
129 lines
3.0 KiB
C++
129 lines
3.0 KiB
C++
//===- llvm/Support/Parallel.cpp - Parallel algorithms --------------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/Support/Parallel.h"
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#include "llvm/Config/llvm-config.h"
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#if LLVM_ENABLE_THREADS
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#include "llvm/Support/Threading.h"
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#include <atomic>
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#include <stack>
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#include <thread>
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using namespace llvm;
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namespace {
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/// An abstract class that takes closures and runs them asynchronously.
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class Executor {
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public:
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virtual ~Executor() = default;
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virtual void add(std::function<void()> func) = 0;
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static Executor *getDefaultExecutor();
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};
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#if defined(_MSC_VER)
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/// An Executor that runs tasks via ConcRT.
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class ConcRTExecutor : public Executor {
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struct Taskish {
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Taskish(std::function<void()> Task) : Task(Task) {}
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std::function<void()> Task;
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static void run(void *P) {
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Taskish *Self = static_cast<Taskish *>(P);
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Self->Task();
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concurrency::Free(Self);
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}
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};
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public:
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virtual void add(std::function<void()> F) {
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Concurrency::CurrentScheduler::ScheduleTask(
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Taskish::run, new (concurrency::Alloc(sizeof(Taskish))) Taskish(F));
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}
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};
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Executor *Executor::getDefaultExecutor() {
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static ConcRTExecutor exec;
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return &exec;
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}
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#else
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/// An implementation of an Executor that runs closures on a thread pool
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/// in filo order.
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class ThreadPoolExecutor : public Executor {
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public:
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explicit ThreadPoolExecutor(unsigned ThreadCount = hardware_concurrency())
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: Done(ThreadCount) {
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// Spawn all but one of the threads in another thread as spawning threads
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// can take a while.
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std::thread([&, ThreadCount] {
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for (size_t i = 1; i < ThreadCount; ++i) {
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std::thread([=] { work(); }).detach();
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}
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work();
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}).detach();
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}
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~ThreadPoolExecutor() override {
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std::unique_lock<std::mutex> Lock(Mutex);
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Stop = true;
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Lock.unlock();
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Cond.notify_all();
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// Wait for ~Latch.
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}
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void add(std::function<void()> F) override {
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std::unique_lock<std::mutex> Lock(Mutex);
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WorkStack.push(F);
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Lock.unlock();
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Cond.notify_one();
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}
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private:
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void work() {
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while (true) {
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std::unique_lock<std::mutex> Lock(Mutex);
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Cond.wait(Lock, [&] { return Stop || !WorkStack.empty(); });
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if (Stop)
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break;
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auto Task = WorkStack.top();
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WorkStack.pop();
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Lock.unlock();
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Task();
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}
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Done.dec();
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}
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std::atomic<bool> Stop{false};
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std::stack<std::function<void()>> WorkStack;
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std::mutex Mutex;
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std::condition_variable Cond;
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parallel::detail::Latch Done;
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};
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Executor *Executor::getDefaultExecutor() {
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static ThreadPoolExecutor exec;
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return &exec;
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}
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#endif
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}
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void parallel::detail::TaskGroup::spawn(std::function<void()> F) {
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L.inc();
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Executor::getDefaultExecutor()->add([&, F] {
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F();
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L.dec();
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});
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}
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#endif // LLVM_ENABLE_THREADS
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