Common: Create AtomicUniquePtr template

Source/Core/Common/AtomicUniquePtr.h

@@ -0,0 +1,51 @@
+// Copyright 2025 Dolphin Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#pragma once
+
+// atomic<shared_ptr<T>> is heavy and has limited compiler availability.
+// atomic<unique_ptr<T>> isn't feasible.
+
+// This class provides something similar to a would-be atomic unique_ptr.
+
+#include <atomic>
+#include <memory>
+
+namespace Common
+{
+
+template <typename T>
+class AtomicUniquePtr
+{
+public:
+  using UniquePtr = std::unique_ptr<T>;
+  using RawPtr = T*;
+
+  AtomicUniquePtr() = default;
+  ~AtomicUniquePtr() { Store(nullptr); }
+
+  AtomicUniquePtr(const AtomicUniquePtr&) = delete;
+  void operator=(const AtomicUniquePtr&) = delete;
+
+  explicit AtomicUniquePtr(std::nullptr_t) {}
+  explicit AtomicUniquePtr(UniquePtr ptr) { Store(std::move(ptr)); }
+
+  void operator=(std::nullptr_t) { Store(nullptr); }
+  void operator=(UniquePtr ptr) { Store(std::move(ptr)); }
+
+  void Store(UniquePtr desired)
+  {
+    // A unique_ptr is returned and appropriately destructed here.
+    Exchange(std::move(desired));
+  }
+
+  UniquePtr Exchange(UniquePtr desired)
+  {
+    return UniquePtr{m_ptr.exchange(desired.release(), std::memory_order_acq_rel)};
+  }
+
+private:
+  std::atomic<RawPtr> m_ptr = nullptr;
+};
+
+}  // namespace Common

Source/Core/Common/CMakeLists.txt

@@ -14,6 +14,7 @@ add_library(common
   Assembler/GekkoParser.cpp
   Assembler/GekkoParser.h
   Assert.h
+  AtomicUniquePtr.h
   BitField.h
   BitSet.h
   BitUtils.h

Source/Core/DolphinLib.props

@@ -22,6 +22,7 @@
     <ClInclude Include="Common\Assembler\GekkoIRGen.h" />
     <ClInclude Include="Common\Assembler\GekkoLexer.h" />
     <ClInclude Include="Common\Assembler\GekkoParser.h" />
+    <ClInclude Include="Common\AtomicUniquePtr.h" />
     <ClInclude Include="Common\BitField.h" />
     <ClInclude Include="Common\BitSet.h" />
     <ClInclude Include="Common\BitUtils.h" />