ModuleSlotTracker.h

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//===-- 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;
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