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//===-- Shared/RefCnt.h - Helper to keep track of references --- C++ ------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
//===----------------------------------------------------------------------===//
#ifndef OMPTARGET_SHARED_REF_CNT_H
#define OMPTARGET_SHARED_REF_CNT_H
#include <atomic>
#include <cassert>
#include <limits>
#include <memory>
namespace llvm {
namespace omp {
namespace target {
/// Utility class for thread-safe reference counting. Any class that needs
/// objects' reference counting can inherit from this entity or have it as a
/// class data member.
template <typename Ty = uint32_t,
std::memory_order MemoryOrder = std::memory_order_relaxed>
struct RefCountTy {
/// Create a refcount object initialized to zero.
RefCountTy() : Refs(0) {}
~RefCountTy() { assert(Refs == 0 && "Destroying with non-zero refcount"); }
/// Increase the reference count atomically.
void increase() { Refs.fetch_add(1, MemoryOrder); }
/// Decrease the reference count and return whether it became zero. Decreasing
/// the counter in more units than it was previously increased results in
/// undefined behavior.
bool decrease() {
Ty Prev = Refs.fetch_sub(1, MemoryOrder);
assert(Prev > 0 && "Invalid refcount");
return (Prev == 1);
}
Ty get() const { return Refs.load(MemoryOrder); }
private:
/// The atomic reference counter.
std::atomic<Ty> Refs;
};
} // namespace target
} // namespace omp
} // namespace llvm
#endif
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