qatomic_cxx11.h

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// Copyright (C) 2011 Thiago Macieira <thiago@kde.org>
// Copyright (C) 2016 Intel Corporation.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only
 
#ifndef QATOMIC_CXX11_H
#define QATOMIC_CXX11_H
 
#include <QtCore/qgenericatomic.h>
#include <QtCore/qyieldcpu.h>
#include <atomic>
 
QT_BEGIN_NAMESPACE
 
#if 0
// silence syncqt warnings
QT_END_NAMESPACE
#pragma qt_sync_skip_header_check
#pragma qt_sync_stop_processing
#endif
 
/* Attempt to detect whether the atomic operations exist in hardware
 * or whether they are emulated by way of a lock.
 *
 * C++11 29.4 [atomics.lockfree] p1 says
 *
 *  The ATOMIC_..._LOCK_FREE macros indicate the lock-free property of the
 *  corresponding atomic types, with the signed and unsigned variants grouped
 *  together. The properties also apply to the corresponding (partial)
 *  specializations of the atomic template. A value of 0 indicates that the
 *  types are never lock-free. A value of 1 indicates that the types are
 *  sometimes lock-free. A value of 2 indicates that the types are always
 *  lock-free.
 *
 * We have a problem when the value is 1: we'd need to check at runtime, but
 * QAtomicInteger requires a constexpr answer (defect introduced in Qt 5.0). So
 * we'll err in the side of caution and say it isn't.
 */
template <int N> struct QAtomicTraits
{ static inline bool isLockFree(); };
 
#define Q_ATOMIC_INT32_IS_SUPPORTED
#if ATOMIC_INT_LOCK_FREE == 2
#  define Q_ATOMIC_INT_REFERENCE_COUNTING_IS_ALWAYS_NATIVE
#  define Q_ATOMIC_INT_TEST_AND_SET_IS_ALWAYS_NATIVE
#  define Q_ATOMIC_INT_FETCH_AND_STORE_IS_ALWAYS_NATIVE
#  define Q_ATOMIC_INT_FETCH_AND_ADD_IS_ALWAYS_NATIVE
#  define Q_ATOMIC_INT32_REFERENCE_COUNTING_IS_ALWAYS_NATIVE
#  define Q_ATOMIC_INT32_TEST_AND_SET_IS_ALWAYS_NATIVE
#  define Q_ATOMIC_INT32_FETCH_AND_STORE_IS_ALWAYS_NATIVE
#  define Q_ATOMIC_INT32_FETCH_AND_ADD_IS_ALWAYS_NATIVE
 
template <> inline bool QAtomicTraits<4>::isLockFree()
{ return true; }
#elif ATOMIC_INT_LOCK_FREE == 1
#  define Q_ATOMIC_INT_REFERENCE_COUNTING_IS_SOMETIMES_NATIVE
#  define Q_ATOMIC_INT_TEST_AND_SET_IS_SOMETIMES_NATIVE
#  define Q_ATOMIC_INT_FETCH_AND_STORE_IS_SOMETIMES_NATIVE
#  define Q_ATOMIC_INT_FETCH_AND_ADD_IS_SOMETIMES_NATIVE
#  define Q_ATOMIC_INT32_REFERENCE_COUNTING_IS_SOMETIMES_NATIVE
#  define Q_ATOMIC_INT32_TEST_AND_SET_IS_SOMETIMES_NATIVE
#  define Q_ATOMIC_INT32_FETCH_AND_STORE_IS_SOMETIMES_NATIVE
#  define Q_ATOMIC_INT32_FETCH_AND_ADD_IS_SOMETIMES_NATIVE
 
template <> inline bool QAtomicTraits<4>::isLockFree()
{ return false; }
#else
#  define Q_ATOMIC_INT_REFERENCE_COUNTING_IS_NEVER_NATIVE
#  define Q_ATOMIC_INT_TEST_AND_SET_IS_NEVER_NATIVE
#  define Q_ATOMIC_INT_FETCH_AND_STORE_IS_NEVER_NATIVE
#  define Q_ATOMIC_INT_FETCH_AND_ADD_IS_NEVER_NATIVE
#  define Q_ATOMIC_INT32_REFERENCE_COUNTING_IS_NEVER_NATIVE
#  define Q_ATOMIC_INT32_TEST_AND_SET_IS_NEVER_NATIVE
#  define Q_ATOMIC_INT32_FETCH_AND_STORE_IS_NEVER_NATIVE
#  define Q_ATOMIC_INT32_FETCH_AND_ADD_IS_NEVER_NATIVE
 
template <> inline bool QAtomicTraits<4>::isLockFree()
{ return false; }
#endif
 
#if ATOMIC_POINTER_LOCK_FREE == 2
#  define Q_ATOMIC_POINTER_REFERENCE_COUNTING_IS_ALWAYS_NATIVE
#  define Q_ATOMIC_POINTER_TEST_AND_SET_IS_ALWAYS_NATIVE
#  define Q_ATOMIC_POINTER_FETCH_AND_STORE_IS_ALWAYS_NATIVE
#  define Q_ATOMIC_POINTER_FETCH_AND_ADD_IS_ALWAYS_NATIVE
#elif ATOMIC_POINTER_LOCK_FREE == 1
#  define Q_ATOMIC_POINTER_REFERENCE_COUNTING_IS_SOMETIMES_NATIVE
#  define Q_ATOMIC_POINTER_TEST_AND_SET_IS_SOMETIMES_NATIVE
#  define Q_ATOMIC_POINTER_FETCH_AND_STORE_IS_SOMETIMES_NATIVE
#  define Q_ATOMIC_POINTER_FETCH_AND_ADD_IS_SOMETIMES_NATIVE
#else
#  define Q_ATOMIC_POINTER_REFERENCE_COUNTING_IS_NEVER_NATIVE
#  define Q_ATOMIC_POINTER_TEST_AND_SET_IS_NEVER_NATIVE
#  define Q_ATOMIC_POINTER_FETCH_AND_STORE_IS_NEVER_NATIVE
#  define Q_ATOMIC_POINTER_FETCH_AND_ADD_IS_NEVER_NATIVE
#endif
 
template<> struct QAtomicOpsSupport<1> { enum { IsSupported = 1 }; };
#define Q_ATOMIC_INT8_IS_SUPPORTED
#if ATOMIC_CHAR_LOCK_FREE == 2
#  define Q_ATOMIC_INT8_REFERENCE_COUNTING_IS_ALWAYS_NATIVE
#  define Q_ATOMIC_INT8_TEST_AND_SET_IS_ALWAYS_NATIVE
#  define Q_ATOMIC_INT8_FETCH_AND_STORE_IS_ALWAYS_NATIVE
#  define Q_ATOMIC_INT8_FETCH_AND_ADD_IS_ALWAYS_NATIVE
 
template <> inline bool QAtomicTraits<1>::isLockFree()
{ return true; }
#elif ATOMIC_CHAR_LOCK_FREE == 1
#  define Q_ATOMIC_INT8_REFERENCE_COUNTING_IS_SOMETIMES_NATIVE
#  define Q_ATOMIC_INT8_TEST_AND_SET_IS_SOMETIMES_NATIVE
#  define Q_ATOMIC_INT8_FETCH_AND_STORE_IS_SOMETIMES_NATIVE
#  define Q_ATOMIC_INT8_FETCH_AND_ADD_IS_SOMETIMES_NATIVE
 
template <> inline bool QAtomicTraits<1>::isLockFree()
{ return false; }
#else
#  define Q_ATOMIC_INT8_REFERENCE_COUNTING_IS_NEVER_NATIVE
#  define Q_ATOMIC_INT8_TEST_AND_SET_IS_NEVER_NATIVE
#  define Q_ATOMIC_INT8_FETCH_AND_STORE_IS_NEVER_NATIVE
#  define Q_ATOMIC_INT8_FETCH_AND_ADD_IS_NEVER_NATIVE
 
template <> bool QAtomicTraits<1>::isLockFree()
{ return false; }
#endif
 
template<> struct QAtomicOpsSupport<2> { enum { IsSupported = 1 }; };
#define Q_ATOMIC_INT16_IS_SUPPORTED
#if ATOMIC_SHORT_LOCK_FREE == 2
#  define Q_ATOMIC_INT16_REFERENCE_COUNTING_IS_ALWAYS_NATIVE
#  define Q_ATOMIC_INT16_TEST_AND_SET_IS_ALWAYS_NATIVE
#  define Q_ATOMIC_INT16_FETCH_AND_STORE_IS_ALWAYS_NATIVE
#  define Q_ATOMIC_INT16_FETCH_AND_ADD_IS_ALWAYS_NATIVE
 
template <> inline bool QAtomicTraits<2>::isLockFree()
{ return false; }
#elif ATOMIC_SHORT_LOCK_FREE == 1
#  define Q_ATOMIC_INT16_REFERENCE_COUNTING_IS_SOMETIMES_NATIVE
#  define Q_ATOMIC_INT16_TEST_AND_SET_IS_SOMETIMES_NATIVE
#  define Q_ATOMIC_INT16_FETCH_AND_STORE_IS_SOMETIMES_NATIVE
#  define Q_ATOMIC_INT16_FETCH_AND_ADD_IS_SOMETIMES_NATIVE
 
template <> inline bool QAtomicTraits<2>::isLockFree()
{ return false; }
#else
#  define Q_ATOMIC_INT16_REFERENCE_COUNTING_IS_NEVER_NATIVE
#  define Q_ATOMIC_INT16_TEST_AND_SET_IS_NEVER_NATIVE
#  define Q_ATOMIC_INT16_FETCH_AND_STORE_IS_NEVER_NATIVE
#  define Q_ATOMIC_INT16_FETCH_AND_ADD_IS_NEVER_NATIVE
 
template <> inline bool QAtomicTraits<2>::isLockFree()
{ return false; }
#endif
 
#if !defined(QT_BOOTSTRAPPED) && QT_CONFIG(std_atomic64)
template<> struct QAtomicOpsSupport<8> { enum { IsSupported = 1 }; };
#  define Q_ATOMIC_INT64_IS_SUPPORTED
#  if ATOMIC_LLONG_LOCK_FREE == 2
#    define Q_ATOMIC_INT64_REFERENCE_COUNTING_IS_ALWAYS_NATIVE
#    define Q_ATOMIC_INT64_TEST_AND_SET_IS_ALWAYS_NATIVE
#    define Q_ATOMIC_INT64_FETCH_AND_STORE_IS_ALWAYS_NATIVE
#    define Q_ATOMIC_INT64_FETCH_AND_ADD_IS_ALWAYS_NATIVE
 
template <> inline bool QAtomicTraits<8>::isLockFree()
{ return true; }
#  elif ATOMIC_LLONG_LOCK_FREE == 1
#    define Q_ATOMIC_INT64_REFERENCE_COUNTING_IS_SOMETIMES_NATIVE
#    define Q_ATOMIC_INT64_TEST_AND_SET_IS_SOMETIMES_NATIVE
#    define Q_ATOMIC_INT64_FETCH_AND_STORE_IS_SOMETIMES_NATIVE
#    define Q_ATOMIC_INT64_FETCH_AND_ADD_IS_SOMETIMES_NATIVE
 
template <> inline bool QAtomicTraits<8>::isLockFree()
{ return false; }
#  else
#    define Q_ATOMIC_INT64_REFERENCE_COUNTING_IS_NEVER_NATIVE
#    define Q_ATOMIC_INT64_TEST_AND_SET_IS_NEVER_NATIVE
#    define Q_ATOMIC_INT64_FETCH_AND_STORE_IS_NEVER_NATIVE
#    define Q_ATOMIC_INT64_FETCH_AND_ADD_IS_NEVER_NATIVE
 
template <> inline bool QAtomicTraits<8>::isLockFree()
{ return false; }
#  endif
#endif
 
template <typename X> struct QAtomicOps
{
    typedef std::atomic<X> Type;
 
    template <typename T> static inline
    T load(const std::atomic<T> &_q_value) noexcept
    {
        return _q_value.load(std::memory_order_relaxed);
    }
 
    template <typename T> static inline
    T load(const volatile std::atomic<T> &_q_value) noexcept
    {
        return _q_value.load(std::memory_order_relaxed);
    }
 
    template <typename T> static inline
    T loadRelaxed(const std::atomic<T> &_q_value) noexcept
    {
        return _q_value.load(std::memory_order_relaxed);
    }
 
    template <typename T> static inline
    T loadRelaxed(const volatile std::atomic<T> &_q_value) noexcept
    {
        return _q_value.load(std::memory_order_relaxed);
    }
 
    template <typename T> static inline
    T loadAcquire(const std::atomic<T> &_q_value) noexcept
    {
        return _q_value.load(std::memory_order_acquire);
    }
 
    template <typename T> static inline
    T loadAcquire(const volatile std::atomic<T> &_q_value) noexcept
    {
        return _q_value.load(std::memory_order_acquire);
    }
 
    template <typename T> static inline
    void store(std::atomic<T> &_q_value, T newValue) noexcept
    {
        _q_value.store(newValue, std::memory_order_relaxed);
    }
 
    template <typename T> static inline
    void storeRelaxed(std::atomic<T> &_q_value, T newValue) noexcept
    {
        _q_value.store(newValue, std::memory_order_relaxed);
    }
 
    template <typename T> static inline
    void storeRelease(std::atomic<T> &_q_value, T newValue) noexcept
    {
        _q_value.store(newValue, std::memory_order_release);
    }
 
    static inline bool isReferenceCountingNative() noexcept { return isTestAndSetNative(); }
    static inline constexpr bool isReferenceCountingWaitFree() noexcept { return false; }
    template <typename T>
    static inline bool ref(std::atomic<T> &_q_value)
    {
        /* Conceptually, we want to
         *    return ++_q_value != 0;
         * However, that would be sequentially consistent, and thus stronger
         * than what we need. Based on
         * http://eel.is/c++draft/atomics.types.memop#6, we know that
         * pre-increment is equivalent to fetch_add(1) + 1. Unlike
         * pre-increment, fetch_add takes a memory order argument, so we can get
         * the desired acquire-release semantics.
         * One last gotcha is that fetch_add(1) + 1 would need to be converted
         * back to T, because it's susceptible to integer promotion. To sidestep
         * this issue and to avoid UB on signed overflow, we rewrite the
         * expression to:
         */
        return _q_value.fetch_add(1, std::memory_order_acq_rel) != T(-1);
    }
 
    template <typename T>
    static inline bool deref(std::atomic<T> &_q_value) noexcept
    {
        // compare with ref
        return _q_value.fetch_sub(1, std::memory_order_acq_rel) != T(1);
    }
 
    static inline bool isTestAndSetNative() noexcept
    { return QAtomicTraits<sizeof(X)>::isLockFree(); }
    static inline constexpr bool isTestAndSetWaitFree() noexcept { return false; }
 
    template <typename T>
    static bool testAndSetRelaxed(std::atomic<T> &_q_value, T expectedValue, T newValue, T *currentValue = nullptr) noexcept
    {
        bool tmp = _q_value.compare_exchange_strong(expectedValue, newValue, std::memory_order_relaxed, std::memory_order_relaxed);
        if (currentValue)
            *currentValue = expectedValue;
        return tmp;
    }
 
    template <typename T>
    static bool testAndSetAcquire(std::atomic<T> &_q_value, T expectedValue, T newValue, T *currentValue = nullptr) noexcept
    {
        bool tmp = _q_value.compare_exchange_strong(expectedValue, newValue, std::memory_order_acquire, std::memory_order_acquire);
        if (currentValue)
            *currentValue = expectedValue;
        return tmp;
    }
 
    template <typename T>
    static bool testAndSetRelease(std::atomic<T> &_q_value, T expectedValue, T newValue, T *currentValue = nullptr) noexcept
    {
        bool tmp = _q_value.compare_exchange_strong(expectedValue, newValue, std::memory_order_release, std::memory_order_relaxed);
        if (currentValue)
            *currentValue = expectedValue;
        return tmp;
    }
 
    template <typename T>
    static bool testAndSetOrdered(std::atomic<T> &_q_value, T expectedValue, T newValue, T *currentValue = nullptr) noexcept
    {
        bool tmp = _q_value.compare_exchange_strong(expectedValue, newValue, std::memory_order_acq_rel, std::memory_order_acquire);
        if (currentValue)
            *currentValue = expectedValue;
        return tmp;
    }
 
    static inline bool isFetchAndStoreNative() noexcept { return isTestAndSetNative(); }
    static inline constexpr bool isFetchAndStoreWaitFree() noexcept { return false; }
 
    template <typename T>
    static T fetchAndStoreRelaxed(std::atomic<T> &_q_value, T newValue) noexcept
    {
        return _q_value.exchange(newValue, std::memory_order_relaxed);
    }
 
    template <typename T>
    static T fetchAndStoreAcquire(std::atomic<T> &_q_value, T newValue) noexcept
    {
        return _q_value.exchange(newValue, std::memory_order_acquire);
    }
 
    template <typename T>
    static T fetchAndStoreRelease(std::atomic<T> &_q_value, T newValue) noexcept
    {
        return _q_value.exchange(newValue, std::memory_order_release);
    }
 
    template <typename T>
    static T fetchAndStoreOrdered(std::atomic<T> &_q_value, T newValue) noexcept
    {
        return _q_value.exchange(newValue, std::memory_order_acq_rel);
    }
 
    static inline bool isFetchAndAddNative() noexcept { return isTestAndSetNative(); }
    static inline constexpr bool isFetchAndAddWaitFree() noexcept { return false; }
 
    template <typename T> static inline
    T fetchAndAddRelaxed(std::atomic<T> &_q_value, typename QAtomicAdditiveType<T>::AdditiveT valueToAdd) noexcept
    {
        return _q_value.fetch_add(valueToAdd, std::memory_order_relaxed);
    }
 
    template <typename T> static inline
    T fetchAndAddAcquire(std::atomic<T> &_q_value, typename QAtomicAdditiveType<T>::AdditiveT valueToAdd) noexcept
    {
        return _q_value.fetch_add(valueToAdd, std::memory_order_acquire);
    }
 
    template <typename T> static inline
    T fetchAndAddRelease(std::atomic<T> &_q_value, typename QAtomicAdditiveType<T>::AdditiveT valueToAdd) noexcept
    {
        return _q_value.fetch_add(valueToAdd, std::memory_order_release);
    }
 
    template <typename T> static inline
    T fetchAndAddOrdered(std::atomic<T> &_q_value, typename QAtomicAdditiveType<T>::AdditiveT valueToAdd) noexcept
    {
        return _q_value.fetch_add(valueToAdd, std::memory_order_acq_rel);
    }
 
    template <typename T> static inline
    T fetchAndSubRelaxed(std::atomic<T> &_q_value, typename QAtomicAdditiveType<T>::AdditiveT valueToAdd) noexcept
    {
        return _q_value.fetch_sub(valueToAdd, std::memory_order_relaxed);
    }
 
    template <typename T> static inline
    T fetchAndSubAcquire(std::atomic<T> &_q_value, typename QAtomicAdditiveType<T>::AdditiveT valueToAdd) noexcept
    {
        return _q_value.fetch_sub(valueToAdd, std::memory_order_acquire);
    }
 
    template <typename T> static inline
    T fetchAndSubRelease(std::atomic<T> &_q_value, typename QAtomicAdditiveType<T>::AdditiveT valueToAdd) noexcept
    {
        return _q_value.fetch_sub(valueToAdd, std::memory_order_release);
    }
 
    template <typename T> static inline
    T fetchAndSubOrdered(std::atomic<T> &_q_value, typename QAtomicAdditiveType<T>::AdditiveT valueToAdd) noexcept
    {
        return _q_value.fetch_sub(valueToAdd, std::memory_order_acq_rel);
    }
 
    template <typename T> static inline
    T fetchAndAndRelaxed(std::atomic<T> &_q_value, typename QAtomicAdditiveType<T>::AdditiveT valueToAdd) noexcept
    {
        return _q_value.fetch_and(valueToAdd, std::memory_order_relaxed);
    }
 
    template <typename T> static inline
    T fetchAndAndAcquire(std::atomic<T> &_q_value, typename QAtomicAdditiveType<T>::AdditiveT valueToAdd) noexcept
    {
        return _q_value.fetch_and(valueToAdd, std::memory_order_acquire);
    }
 
    template <typename T> static inline
    T fetchAndAndRelease(std::atomic<T> &_q_value, typename QAtomicAdditiveType<T>::AdditiveT valueToAdd) noexcept
    {
        return _q_value.fetch_and(valueToAdd, std::memory_order_release);
    }
 
    template <typename T> static inline
    T fetchAndAndOrdered(std::atomic<T> &_q_value, typename QAtomicAdditiveType<T>::AdditiveT valueToAdd) noexcept
    {
        return _q_value.fetch_and(valueToAdd, std::memory_order_acq_rel);
    }
 
    template <typename T> static inline
    T fetchAndOrRelaxed(std::atomic<T> &_q_value, typename QAtomicAdditiveType<T>::AdditiveT valueToAdd) noexcept
    {
        return _q_value.fetch_or(valueToAdd, std::memory_order_relaxed);
    }
 
    template <typename T> static inline
    T fetchAndOrAcquire(std::atomic<T> &_q_value, typename QAtomicAdditiveType<T>::AdditiveT valueToAdd) noexcept
    {
        return _q_value.fetch_or(valueToAdd, std::memory_order_acquire);
    }
 
    template <typename T> static inline
    T fetchAndOrRelease(std::atomic<T> &_q_value, typename QAtomicAdditiveType<T>::AdditiveT valueToAdd) noexcept
    {
        return _q_value.fetch_or(valueToAdd, std::memory_order_release);
    }
 
    template <typename T> static inline
    T fetchAndOrOrdered(std::atomic<T> &_q_value, typename QAtomicAdditiveType<T>::AdditiveT valueToAdd) noexcept
    {
        return _q_value.fetch_or(valueToAdd, std::memory_order_acq_rel);
    }
 
    template <typename T> static inline
    T fetchAndXorRelaxed(std::atomic<T> &_q_value, typename QAtomicAdditiveType<T>::AdditiveT valueToAdd) noexcept
    {
        return _q_value.fetch_xor(valueToAdd, std::memory_order_relaxed);
    }
 
    template <typename T> static inline
    T fetchAndXorAcquire(std::atomic<T> &_q_value, typename QAtomicAdditiveType<T>::AdditiveT valueToAdd) noexcept
    {
        return _q_value.fetch_xor(valueToAdd, std::memory_order_acquire);
    }
 
    template <typename T> static inline
    T fetchAndXorRelease(std::atomic<T> &_q_value, typename QAtomicAdditiveType<T>::AdditiveT valueToAdd) noexcept
    {
        return _q_value.fetch_xor(valueToAdd, std::memory_order_release);
    }
 
    template <typename T> static inline
    T fetchAndXorOrdered(std::atomic<T> &_q_value, typename QAtomicAdditiveType<T>::AdditiveT valueToAdd) noexcept
    {
        return _q_value.fetch_xor(valueToAdd, std::memory_order_acq_rel);
    }
};
 
#  define Q_BASIC_ATOMIC_INITIALIZER(a)     { a }
 
QT_END_NAMESPACE
 
#endif // QATOMIC_CXX0X_H