[orc-rt] Add ResourceManager interface.

The ResourceManager interface can be used to implement ownership for resources
allocated to JIT'd code, e.g. memory and metadata registrations (frame info,
language runtime metadata, etc.).

Resources can be *deallocated*, meaning that they should be cleaned up (memory
released, registrations deregistered, etc.), or they can be *detached*, meaning
that cleanup should be performed automatically when the ResourceManager itself
is destroyed.

The intent is to allow JIT'd code to continue running after the
llvm::orc::ExecutionSession that produced it is disconnected / destroyed.

orc-rt/include/CMakeLists.txt

@@ -12,6 +12,7 @@ set(ORC_RT_HEADERS
     orc-rt/IntervalSet.h
     orc-rt/Math.h
     orc-rt/MemoryFlags.h
+    orc-rt/ResourceManager.h
     orc-rt/RTTI.h
     orc-rt/ScopeExit.h
     orc-rt/SimplePackedSerialization.h

orc-rt/include/orc-rt/ResourceManager.h

@@ -0,0 +1,44 @@
+//===- ResourceManager.h -- Interface for JIT resource managers -*- 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
+//
+//===----------------------------------------------------------------------===//
+//
+// ResourceManager class and related APIs.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef ORC_RT_RESOURCEMANAGER_H
+#define ORC_RT_RESOURCEMANAGER_H
+
+#include "orc-rt/Error.h"
+#include "orc-rt/move_only_function.h"
+
+namespace orc_rt {
+
+/// A ResourceManager manages resources (e.g. JIT'd memory) to support a JIT
+/// session.
+class ResourceManager {
+public:
+  using OnCompleteFn = move_only_function<void(Error)>;
+
+  virtual ~ResourceManager();
+
+  /// The detach method will be called if the controller disconnects from the
+  /// session without shutting the session down.
+  ///
+  /// Since no further requests for allocation will be made, the ResourceManager
+  /// may discard any book-keeping data-structures used to support allocation.
+  /// E.g. a JIT memory manager may discard its free-list, since no further
+  /// JIT'd allocations will happen.
+  virtual void detach(OnCompleteFn OnComplete) = 0;
+
+  /// The shutdown operation will be called at the end of the session.
+  /// The ResourceManager should release all held resources.
+  virtual void shutdown(OnCompleteFn OnComplete) = 0;
+};
+} // namespace orc_rt
+
+#endif // ORC_RT_RESOURCEMANAGER_H

orc-rt/lib/executor/CMakeLists.txt

@@ -1,6 +1,7 @@
 set(files
   orc-rt-executor.cpp
   AllocAction.cpp
+  ResourceManager.cpp
   RTTI.cpp
   )
 

orc-rt/lib/executor/ResourceManager.cpp

@@ -0,0 +1,19 @@
+//===- ResourceManager.cpp ------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+//
+// Contains the implementation of APIs in the orc-rt/ResourceManager.h header.
+//
+//===----------------------------------------------------------------------===//
+
+#include "orc-rt/ResourceManager.h"
+
+namespace orc_rt {
+
+ResourceManager::~ResourceManager() = default;
+
+} // namespace orc_rt