//===--- Atomic.h - Utilities for atomic operations. ------------*- C++ -*-===//
//
// This source file is part of the Swift.org open source project
//
// Copyright (c) 2014 - 2018 Apple Inc. and the Swift project authors
// Licensed under Apache License v2.0 with Runtime Library Exception
//
// See https://swift.org/LICENSE.txt for license information
// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
//
//===----------------------------------------------------------------------===//
//
// Utilities for atomic operations, to use with std::atomic.
//
//===----------------------------------------------------------------------===//

#ifndef SWIFT_RUNTIME_ATOMIC_H
#define SWIFT_RUNTIME_ATOMIC_H

// FIXME: Workaround for rdar://problem/18889711. 'Consume' does not require
// a barrier on ARM64, but LLVM doesn't know that. Although 'relaxed'
// is formally UB by C++11 language rules, we should be OK because neither
// the processor model nor the optimizer can realistically reorder our uses
// of 'consume'.
#if __arm64__ || __arm__
#  define SWIFT_MEMORY_ORDER_CONSUME (std::memory_order_relaxed)
#else
#  define SWIFT_MEMORY_ORDER_CONSUME (std::memory_order_consume)
#endif

#endif