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//===- PtrState.h - ARC State for a Ptr -------------------------*- 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
//
//===----------------------------------------------------------------------===//
//
// This file contains declarations for the ARC state associated with a ptr. It
// is only used by the ARC Sequence Dataflow computation. By separating this
// from the actual dataflow, it is easier to consider the mechanics of the ARC
// optimization separate from the actual predicates being used.
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_LIB_TRANSFORMS_OBJCARC_PTRSTATE_H
#define LLVM_LIB_TRANSFORMS_OBJCARC_PTRSTATE_H
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/Analysis/ObjCARCInstKind.h"
#include "llvm/Support/Compiler.h"
namespace llvm {
class BasicBlock;
class Instruction;
class MDNode;
class raw_ostream;
class Value;
namespace objcarc {
class ARCMDKindCache;
class BundledRetainClaimRVs;
class ProvenanceAnalysis;
/// \enum Sequence
///
/// A sequence of states that a pointer may go through in which an
/// objc_retain and objc_release are actually needed.
enum Sequence {
S_None,
S_Retain, ///< objc_retain(x).
S_CanRelease, ///< foo(x) -- x could possibly see a ref count decrement.
S_Use, ///< any use of x.
S_Stop, ///< code motion is stopped.
S_MovableRelease ///< objc_release(x), !clang.imprecise_release.
};
raw_ostream &operator<<(raw_ostream &OS,
const Sequence S) LLVM_ATTRIBUTE_UNUSED;
/// Unidirectional information about either a
/// retain-decrement-use-release sequence or release-use-decrement-retain
/// reverse sequence.
struct RRInfo {
/// After an objc_retain, the reference count of the referenced
/// object is known to be positive. Similarly, before an objc_release, the
/// reference count of the referenced object is known to be positive. If
/// there are retain-release pairs in code regions where the retain count
/// is known to be positive, they can be eliminated, regardless of any side
/// effects between them.
///
/// Also, a retain+release pair nested within another retain+release
/// pair all on the known same pointer value can be eliminated, regardless
/// of any intervening side effects.
///
/// KnownSafe is true when either of these conditions is satisfied.
bool KnownSafe = false;
/// True of the objc_release calls are all marked with the "tail" keyword.
bool IsTailCallRelease = false;
/// If the Calls are objc_release calls and they all have a
/// clang.imprecise_release tag, this is the metadata tag.
MDNode *ReleaseMetadata = nullptr;
/// For a top-down sequence, the set of objc_retains or
/// objc_retainBlocks. For bottom-up, the set of objc_releases.
SmallPtrSet<Instruction *, 2> Calls;
/// The set of optimal insert positions for moving calls in the opposite
/// sequence.
SmallPtrSet<Instruction *, 2> ReverseInsertPts;
/// If this is true, we cannot perform code motion but can still remove
/// retain/release pairs.
bool CFGHazardAfflicted = false;
RRInfo() = default;
void clear();
/// Conservatively merge the two RRInfo. Returns true if a partial merge has
/// occurred, false otherwise.
bool Merge(const RRInfo &Other);
};
/// This class summarizes several per-pointer runtime properties which
/// are propagated through the flow graph.
class PtrState {
protected:
/// True if the reference count is known to be incremented.
bool KnownPositiveRefCount = false;
/// True if we've seen an opportunity for partial RR elimination, such as
/// pushing calls into a CFG triangle or into one side of a CFG diamond.
bool Partial = false;
/// The current position in the sequence.
unsigned char Seq : 8;
/// Unidirectional information about the current sequence.
RRInfo RRI;
PtrState() : Seq(S_None) {}
public:
bool IsKnownSafe() const { return RRI.KnownSafe; }
void SetKnownSafe(const bool NewValue) { RRI.KnownSafe = NewValue; }
bool IsTailCallRelease() const { return RRI.IsTailCallRelease; }
void SetTailCallRelease(const bool NewValue) {
RRI.IsTailCallRelease = NewValue;
}
bool IsTrackingImpreciseReleases() const {
return RRI.ReleaseMetadata != nullptr;
}
const MDNode *GetReleaseMetadata() const { return RRI.ReleaseMetadata; }
void SetReleaseMetadata(MDNode *NewValue) { RRI.ReleaseMetadata = NewValue; }
bool IsCFGHazardAfflicted() const { return RRI.CFGHazardAfflicted; }
void SetCFGHazardAfflicted(const bool NewValue) {
RRI.CFGHazardAfflicted = NewValue;
}
void SetKnownPositiveRefCount();
void ClearKnownPositiveRefCount();
bool HasKnownPositiveRefCount() const { return KnownPositiveRefCount; }
void SetSeq(Sequence NewSeq);
Sequence GetSeq() const { return static_cast<Sequence>(Seq); }
void ClearSequenceProgress() { ResetSequenceProgress(S_None); }
void ResetSequenceProgress(Sequence NewSeq);
void Merge(const PtrState &Other, bool TopDown);
void InsertCall(Instruction *I) { RRI.Calls.insert(I); }
void InsertReverseInsertPt(Instruction *I) { RRI.ReverseInsertPts.insert(I); }
void ClearReverseInsertPts() { RRI.ReverseInsertPts.clear(); }
bool HasReverseInsertPts() const { return !RRI.ReverseInsertPts.empty(); }
const RRInfo &GetRRInfo() const { return RRI; }
};
struct BottomUpPtrState : PtrState {
BottomUpPtrState() = default;
/// (Re-)Initialize this bottom up pointer returning true if we detected a
/// pointer with nested releases.
bool InitBottomUp(ARCMDKindCache &Cache, Instruction *I);
/// Return true if this set of releases can be paired with a release. Modifies
/// state appropriately to reflect that the matching occurred if it is
/// successful.
///
/// It is assumed that one has already checked that the RCIdentity of the
/// retain and the RCIdentity of this ptr state are the same.
bool MatchWithRetain();
void HandlePotentialUse(BasicBlock *BB, Instruction *Inst, const Value *Ptr,
ProvenanceAnalysis &PA, ARCInstKind Class);
bool HandlePotentialAlterRefCount(Instruction *Inst, const Value *Ptr,
ProvenanceAnalysis &PA, ARCInstKind Class);
};
struct TopDownPtrState : PtrState {
TopDownPtrState() = default;
/// (Re-)Initialize this bottom up pointer returning true if we detected a
/// pointer with nested releases.
bool InitTopDown(ARCInstKind Kind, Instruction *I);
/// Return true if this set of retains can be paired with the given
/// release. Modifies state appropriately to reflect that the matching
/// occurred.
bool MatchWithRelease(ARCMDKindCache &Cache, Instruction *Release);
void HandlePotentialUse(Instruction *Inst, const Value *Ptr,
ProvenanceAnalysis &PA, ARCInstKind Class);
bool HandlePotentialAlterRefCount(Instruction *Inst, const Value *Ptr,
ProvenanceAnalysis &PA, ARCInstKind Class,
const BundledRetainClaimRVs &BundledRVs);
};
} // end namespace objcarc
} // end namespace llvm
#endif // LLVM_LIB_TRANSFORMS_OBJCARC_PTRSTATE_H
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