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diff --git a/clang-r353983e/include/llvm/IR/ModuleSlotTracker.h b/clang-r353983e/include/llvm/IR/ModuleSlotTracker.h
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+//===-- llvm/IR/ModuleSlotTracker.h -----------------------------*- 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
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_IR_MODULESLOTTRACKER_H
+#define LLVM_IR_MODULESLOTTRACKER_H
+
+#include <memory>
+
+namespace llvm {
+
+class Module;
+class Function;
+class SlotTracker;
+class Value;
+
+/// 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;
+  bool ShouldCreateStorage = false;
+  bool ShouldInitializeAllMetadata = false;
+
+  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.  Otherwise, initializes
+  /// a slot tracker, and initializes all metadata slots.  \c
+  /// ShouldInitializeAllMetadata defaults to true because this is expected to
+  /// be shared between multiple callers, and otherwise MDNode references will
+  /// not match up.
+  explicit ModuleSlotTracker(const Module *M,
+                             bool ShouldInitializeAllMetadata = true);
+
+  /// Destructor to clean up storage.
+  ~ModuleSlotTracker();
+
+  /// Lazily creates a slot tracker.
+  SlotTracker *getMachine();
+
+  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);
+
+  /// Return the slot number of the specified local value.
+  ///
+  /// A function that defines this value should be incorporated prior to calling
+  /// this method.
+  /// Return -1 if the value is not in the function's SlotTracker.
+  int getLocalSlot(const Value *V);
+};
+
+} // end namespace llvm
+
+#endif