dolphin/Source/Core/Common/Atomic_Win32.h

// Copyright 2009 Dolphin Emulator Project
// Licensed under GPLv2+
// Refer to the license.txt file included.

// IWYU pragma: private, include "Common/Atomic.h"

#pragma once

#include <Windows.h>

#include <atomic>
#include "Common/CommonTypes.h"

// Atomic operations are performed in a single step by the CPU. It is
// impossible for other threads to see the operation "half-done."
//
// Some atomic operations can be combined with different types of memory
// barriers called "Acquire semantics" and "Release semantics", defined below.
//
// Acquire semantics: Future memory accesses cannot be relocated to before the
//                    operation.
//
// Release semantics: Past memory accesses cannot be relocated to after the
//                    operation.
//
// These barriers affect not only the compiler, but also the CPU.
//
// NOTE: Acquire and Release are not differentiated right now. They perform a
// full memory barrier instead of a "one-way" memory barrier. The newest
// Windows SDK has Acquire and Release versions of some Interlocked* functions.

namespace Common
{
inline void AtomicAdd(volatile u32& target, u32 value)
{
  _InterlockedExchangeAdd((volatile LONG*)&target, (LONG)value);
}

inline void AtomicAnd(volatile u32& target, u32 value)
{
  _InterlockedAnd((volatile LONG*)&target, (LONG)value);
}

inline void AtomicIncrement(volatile u32& target)
{
  _InterlockedIncrement((volatile LONG*)&target);
}

inline void AtomicDecrement(volatile u32& target)
{
  _InterlockedDecrement((volatile LONG*)&target);
}

inline void AtomicOr(volatile u32& target, u32 value)
{
  _InterlockedOr((volatile LONG*)&target, (LONG)value);
}

template <typename T>
inline T AtomicLoad(volatile T& src)
{
  return src;  // 32-bit reads are always atomic.
}

template <typename T>
inline T AtomicLoadAcquire(volatile T& src)
{
  // 32-bit reads are always atomic.
  T result = src;
  // Compiler instruction only. x86 loads always have acquire semantics.
  std::atomic_thread_fence(std::memory_order_acquire);
  return result;
}

template <typename T, typename U>
inline void AtomicStore(volatile T& dest, U value)
{
  dest = (T)value;  // 32-bit writes are always atomic.
}

template <typename T, typename U>
inline void AtomicStoreRelease(volatile T& dest, U value)
{
  // Compiler instruction only. x86 stores always have release semantics.
  std::atomic_thread_fence(std::memory_order_release);
  dest = (T)value;  // 32-bit writes are always atomic.
}

template <typename T, typename U>
inline T* AtomicExchangeAcquire(T* volatile& loc, U newval)
{
  return (T*)_InterlockedExchangePointer_acq((void* volatile*)&loc, (void*)newval);
}
}  // namespace Common