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//===- llvm/IR/MetadataTracking.h - Metadata tracking ---------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// Low-level functions to enable tracking of metadata that could RAUW.
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_IR_METADATATRACKING_H
#define LLVM_IR_METADATATRACKING_H
#include "llvm/ADT/PointerUnion.h"
#include "llvm/Support/Casting.h"
#include <type_traits>
namespace llvm {
class Metadata;
class MetadataAsValue;
/// \brief API for tracking metadata references through RAUW and deletion.
///
/// Shared API for updating \a Metadata pointers in subclasses that support
/// RAUW.
///
/// This API is not meant to be used directly. See \a TrackingMDRef for a
/// user-friendly tracking reference.
class MetadataTracking {
public:
/// \brief Track the reference to metadata.
///
/// Register \c MD with \c *MD, if the subclass supports tracking. If \c *MD
/// gets RAUW'ed, \c MD will be updated to the new address. If \c *MD gets
/// deleted, \c MD will be set to \c nullptr.
///
/// If tracking isn't supported, \c *MD will not change.
///
/// \return true iff tracking is supported by \c MD.
static bool track(Metadata *&MD) {
return track(&MD, *MD, static_cast<Metadata *>(nullptr));
}
/// \brief Track the reference to metadata for \a Metadata.
///
/// As \a track(Metadata*&), but with support for calling back to \c Owner to
/// tell it that its operand changed. This could trigger \c Owner being
/// re-uniqued.
static bool track(void *Ref, Metadata &MD, Metadata &Owner) {
return track(Ref, MD, &Owner);
}
/// \brief Track the reference to metadata for \a MetadataAsValue.
///
/// As \a track(Metadata*&), but with support for calling back to \c Owner to
/// tell it that its operand changed. This could trigger \c Owner being
/// re-uniqued.
static bool track(void *Ref, Metadata &MD, MetadataAsValue &Owner) {
return track(Ref, MD, &Owner);
}
/// \brief Stop tracking a reference to metadata.
///
/// Stops \c *MD from tracking \c MD.
static void untrack(Metadata *&MD) { untrack(&MD, *MD); }
static void untrack(void *Ref, Metadata &MD);
/// \brief Move tracking from one reference to another.
///
/// Semantically equivalent to \c untrack(MD) followed by \c track(New),
/// except that ownership callbacks are maintained.
///
/// Note: it is an error if \c *MD does not equal \c New.
///
/// \return true iff tracking is supported by \c MD.
static bool retrack(Metadata *&MD, Metadata *&New) {
return retrack(&MD, *MD, &New);
}
static bool retrack(void *Ref, Metadata &MD, void *New);
/// \brief Check whether metadata is replaceable.
static bool isReplaceable(const Metadata &MD);
typedef PointerUnion<MetadataAsValue *, Metadata *> OwnerTy;
private:
/// \brief Track a reference to metadata for an owner.
///
/// Generalized version of tracking.
static bool track(void *Ref, Metadata &MD, OwnerTy Owner);
};
} // end namespace llvm
#endif
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