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+//===- llvm/Support/Parallel.h - Parallel algorithms ----------------------===//
+//
+// 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/ADT/STLExtras.h"
+#include "llvm/Config/llvm-config.h"
+#include "llvm/Support/MathExtras.h"
+
+#include <algorithm>
+#include <condition_variable>
+#include <functional>
+#include <mutex>
+
+#if defined(_MSC_VER) && LLVM_ENABLE_THREADS
+#pragma warning(push)
+#pragma warning(disable : 4530)
+#include <concrt.h>
+#include <ppl.h>
+#pragma warning(pop)
+#endif
+
+namespace llvm {
+
+namespace parallel {
+struct sequential_execution_policy {};
+struct parallel_execution_policy {};
+
+template <typename T>
+struct is_execution_policy
+ : public std::integral_constant<
+ bool, llvm::is_one_of<T, sequential_execution_policy,
+ parallel_execution_policy>::value> {};
+
+constexpr sequential_execution_policy seq{};
+constexpr parallel_execution_policy par{};
+
+namespace detail {
+
+#if LLVM_ENABLE_THREADS
+
+class Latch {
+ uint32_t Count;
+ mutable std::mutex Mutex;
+ mutable std::condition_variable Cond;
+
+public:
+ explicit Latch(uint32_t Count = 0) : Count(Count) {}
+ ~Latch() { sync(); }
+
+ void inc() {
+ std::unique_lock<std::mutex> lock(Mutex);
+ ++Count;
+ }
+
+ void dec() {
+ std::unique_lock<std::mutex> lock(Mutex);
+ if (--Count == 0)
+ Cond.notify_all();
+ }
+
+ void sync() const {
+ std::unique_lock<std::mutex> lock(Mutex);
+ Cond.wait(lock, [&] { return Count == 0; });
+ }
+};
+
+class TaskGroup {
+ Latch L;
+
+public:
+ void spawn(std::function<void()> f);
+
+ void sync() const { L.sync(); }
+};
+
+#if defined(_MSC_VER)
+template <class RandomAccessIterator, class Comparator>
+void parallel_sort(RandomAccessIterator Start, RandomAccessIterator End,
+ const Comparator &Comp) {
+ concurrency::parallel_sort(Start, End, Comp);
+}
+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_each_n(IndexTy Begin, IndexTy End, FuncTy Fn) {
+ concurrency::parallel_for(Begin, End, Fn);
+}
+
+#else
+const ptrdiff_t MinParallelSize = 1024;
+
+/// \brief Inclusive median.
+template <class RandomAccessIterator, class Comparator>
+RandomAccessIterator medianOf3(RandomAccessIterator Start,
+ RandomAccessIterator End,
+ const Comparator &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 Comparator>
+void parallel_quick_sort(RandomAccessIterator Start, RandomAccessIterator End,
+ const Comparator &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 Comparator>
+void parallel_sort(RandomAccessIterator Start, RandomAccessIterator End,
+ const Comparator &Comp) {
+ TaskGroup TG;
+ parallel_quick_sort(Start, End, Comp, TG,
+ llvm::Log2_64(std::distance(Start, End)) + 1);
+}
+
+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_each_n(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
+
+#endif
+
+template <typename Iter>
+using DefComparator =
+ std::less<typename std::iterator_traits<Iter>::value_type>;
+
+} // namespace detail
+
+// sequential algorithm implementations.
+template <class Policy, class RandomAccessIterator,
+ class Comparator = detail::DefComparator<RandomAccessIterator>>
+void sort(Policy policy, RandomAccessIterator Start, RandomAccessIterator End,
+ const Comparator &Comp = Comparator()) {
+ static_assert(is_execution_policy<Policy>::value,
+ "Invalid execution policy!");
+ std::sort(Start, End, Comp);
+}
+
+template <class Policy, class IterTy, class FuncTy>
+void for_each(Policy policy, IterTy Begin, IterTy End, FuncTy Fn) {
+ static_assert(is_execution_policy<Policy>::value,
+ "Invalid execution policy!");
+ std::for_each(Begin, End, Fn);
+}
+
+template <class Policy, class IndexTy, class FuncTy>
+void for_each_n(Policy policy, IndexTy Begin, IndexTy End, FuncTy Fn) {
+ static_assert(is_execution_policy<Policy>::value,
+ "Invalid execution policy!");
+ for (IndexTy I = Begin; I != End; ++I)
+ Fn(I);
+}
+
+// Parallel algorithm implementations, only available when LLVM_ENABLE_THREADS
+// is true.
+#if LLVM_ENABLE_THREADS
+template <class RandomAccessIterator,
+ class Comparator = detail::DefComparator<RandomAccessIterator>>
+void sort(parallel_execution_policy policy, RandomAccessIterator Start,
+ RandomAccessIterator End, const Comparator &Comp = Comparator()) {
+ detail::parallel_sort(Start, End, Comp);
+}
+
+template <class IterTy, class FuncTy>
+void for_each(parallel_execution_policy policy, IterTy Begin, IterTy End,
+ FuncTy Fn) {
+ detail::parallel_for_each(Begin, End, Fn);
+}
+
+template <class IndexTy, class FuncTy>
+void for_each_n(parallel_execution_policy policy, IndexTy Begin, IndexTy End,
+ FuncTy Fn) {
+ detail::parallel_for_each_n(Begin, End, Fn);
+}
+#endif
+
+} // namespace parallel
+} // namespace llvm
+
+#endif // LLVM_SUPPORT_PARALLEL_H
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