+//===-- llvm/IR/ModuleSlotTracker.h -----------------------------*- C++ -*-===//
+//
+// The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_IR_MODULESLOTTRACKER_H
+#define LLVM_IR_MODULESLOTTRACKER_H
+
+#include <memory>
+
+namespace llvm {
+
+class Module;
+class Function;
+class SlotTracker;
+
+/// Manage lifetime of a slot tracker for printing IR.
+///
+/// Wrapper around the \a SlotTracker used internally by \a AsmWriter. This
+/// class allows callers to share the cost of incorporating the metadata in a
+/// module or a function.
+///
+/// If the IR changes from underneath \a ModuleSlotTracker, strings like
+/// "<badref>" will be printed, or, worse, the wrong slots entirely.
+class ModuleSlotTracker {
+ /// Storage for a slot tracker.
+ std::unique_ptr<SlotTracker> MachineStorage;
+
+ const Module *M = nullptr;
+ const Function *F = nullptr;
+ SlotTracker *Machine = nullptr;
+
+public:
+ /// Wrap a preinitialized SlotTracker.
+ ModuleSlotTracker(SlotTracker &Machine, const Module *M,
+ const Function *F = nullptr);
+
+ /// Construct a slot tracker from a module.
+ ///
+ /// If \a M is \c nullptr, uses a null slot tracker.
+ explicit ModuleSlotTracker(const Module *M);
+
+ /// Destructor to clean up storage.
+ ~ModuleSlotTracker();
+
+ SlotTracker *getMachine() const { return Machine; }
+ const Module *getModule() const { return M; }
+ const Function *getCurrentFunction() const { return F; }
+
+ /// Incorporate the given function.
+ ///
+ /// Purge the currently incorporated function and incorporate \c F. If \c F
+ /// is currently incorporated, this is a no-op.
+ void incorporateFunction(const Function &F);
+};
+
+} // end namespace llvm
+
+#endif