Imported Upstream version 5.18.0.205

Former-commit-id: 7f59f7e792705db773f1caecdaa823092f4e2927

external/llvm/lib/Transforms/ObjCARC/PtrState.cpp

@@ -0,0 +1,426 @@
+//===- PtrState.cpp -------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "PtrState.h"
+#include "DependencyAnalysis.h"
+#include "ObjCARC.h"
+#include "llvm/Analysis/ObjCARCAnalysisUtils.h"
+#include "llvm/Analysis/ObjCARCInstKind.h"
+#include "llvm/IR/BasicBlock.h"
+#include "llvm/IR/Instruction.h"
+#include "llvm/IR/Instructions.h"
+#include "llvm/IR/Value.h"
+#include "llvm/Support/Casting.h"
+#include "llvm/Support/Compiler.h"
+#include "llvm/Support/Debug.h"
+#include "llvm/Support/ErrorHandling.h"
+#include "llvm/Support/raw_ostream.h"
+#include <cassert>
+#include <iterator>
+#include <utility>
+
+using namespace llvm;
+using namespace llvm::objcarc;
+
+#define DEBUG_TYPE "objc-arc-ptr-state"
+
+//===----------------------------------------------------------------------===//
+//                                  Utility
+//===----------------------------------------------------------------------===//
+
+raw_ostream &llvm::objcarc::operator<<(raw_ostream &OS, const Sequence S) {
+  switch (S) {
+  case S_None:
+    return OS << "S_None";
+  case S_Retain:
+    return OS << "S_Retain";
+  case S_CanRelease:
+    return OS << "S_CanRelease";
+  case S_Use:
+    return OS << "S_Use";
+  case S_Release:
+    return OS << "S_Release";
+  case S_MovableRelease:
+    return OS << "S_MovableRelease";
+  case S_Stop:
+    return OS << "S_Stop";
+  }
+  llvm_unreachable("Unknown sequence type.");
+}
+
+//===----------------------------------------------------------------------===//
+//                                  Sequence
+//===----------------------------------------------------------------------===//
+
+static Sequence MergeSeqs(Sequence A, Sequence B, bool TopDown) {
+  // The easy cases.
+  if (A == B)
+    return A;
+  if (A == S_None || B == S_None)
+    return S_None;
+
+  if (A > B)
+    std::swap(A, B);
+  if (TopDown) {
+    // Choose the side which is further along in the sequence.
+    if ((A == S_Retain || A == S_CanRelease) &&
+        (B == S_CanRelease || B == S_Use))
+      return B;
+  } else {
+    // Choose the side which is further along in the sequence.
+    if ((A == S_Use || A == S_CanRelease) &&
+        (B == S_Use || B == S_Release || B == S_Stop || B == S_MovableRelease))
+      return A;
+    // If both sides are releases, choose the more conservative one.
+    if (A == S_Stop && (B == S_Release || B == S_MovableRelease))
+      return A;
+    if (A == S_Release && B == S_MovableRelease)
+      return A;
+  }
+
+  return S_None;
+}
+
+//===----------------------------------------------------------------------===//
+//                                   RRInfo
+//===----------------------------------------------------------------------===//
+
+void RRInfo::clear() {
+  KnownSafe = false;
+  IsTailCallRelease = false;
+  ReleaseMetadata = nullptr;
+  Calls.clear();
+  ReverseInsertPts.clear();
+  CFGHazardAfflicted = false;
+}
+
+bool RRInfo::Merge(const RRInfo &Other) {
+  // Conservatively merge the ReleaseMetadata information.
+  if (ReleaseMetadata != Other.ReleaseMetadata)
+    ReleaseMetadata = nullptr;
+
+  // Conservatively merge the boolean state.
+  KnownSafe &= Other.KnownSafe;
+  IsTailCallRelease &= Other.IsTailCallRelease;
+  CFGHazardAfflicted |= Other.CFGHazardAfflicted;
+
+  // Merge the call sets.
+  Calls.insert(Other.Calls.begin(), Other.Calls.end());
+
+  // Merge the insert point sets. If there are any differences,
+  // that makes this a partial merge.
+  bool Partial = ReverseInsertPts.size() != Other.ReverseInsertPts.size();
+  for (Instruction *Inst : Other.ReverseInsertPts)
+    Partial |= ReverseInsertPts.insert(Inst).second;
+  return Partial;
+}
+
+//===----------------------------------------------------------------------===//
+//                                  PtrState
+//===----------------------------------------------------------------------===//
+
+void PtrState::SetKnownPositiveRefCount() {
+  DEBUG(dbgs() << "        Setting Known Positive.\n");
+  KnownPositiveRefCount = true;
+}
+
+void PtrState::ClearKnownPositiveRefCount() {
+  DEBUG(dbgs() << "        Clearing Known Positive.\n");
+  KnownPositiveRefCount = false;
+}
+
+void PtrState::SetSeq(Sequence NewSeq) {
+  DEBUG(dbgs() << "            Old: " << GetSeq() << "; New: " << NewSeq << "\n");
+  Seq = NewSeq;
+}
+
+void PtrState::ResetSequenceProgress(Sequence NewSeq) {
+  DEBUG(dbgs() << "        Resetting sequence progress.\n");
+  SetSeq(NewSeq);
+  Partial = false;
+  RRI.clear();
+}
+
+void PtrState::Merge(const PtrState &Other, bool TopDown) {
+  Seq = MergeSeqs(GetSeq(), Other.GetSeq(), TopDown);
+  KnownPositiveRefCount &= Other.KnownPositiveRefCount;
+
+  // If we're not in a sequence (anymore), drop all associated state.
+  if (Seq == S_None) {
+    Partial = false;
+    RRI.clear();
+  } else if (Partial || Other.Partial) {
+    // If we're doing a merge on a path that's previously seen a partial
+    // merge, conservatively drop the sequence, to avoid doing partial
+    // RR elimination. If the branch predicates for the two merge differ,
+    // mixing them is unsafe.
+    ClearSequenceProgress();
+  } else {
+    // Otherwise merge the other PtrState's RRInfo into our RRInfo. At this
+    // point, we know that currently we are not partial. Stash whether or not
+    // the merge operation caused us to undergo a partial merging of reverse
+    // insertion points.
+    Partial = RRI.Merge(Other.RRI);
+  }
+}
+
+//===----------------------------------------------------------------------===//
+//                              BottomUpPtrState
+//===----------------------------------------------------------------------===//
+
+bool BottomUpPtrState::InitBottomUp(ARCMDKindCache &Cache, Instruction *I) {
+  // If we see two releases in a row on the same pointer. If so, make
+  // a note, and we'll cicle back to revisit it after we've
+  // hopefully eliminated the second release, which may allow us to
+  // eliminate the first release too.
+  // Theoretically we could implement removal of nested retain+release
+  // pairs by making PtrState hold a stack of states, but this is
+  // simple and avoids adding overhead for the non-nested case.
+  bool NestingDetected = false;
+  if (GetSeq() == S_Release || GetSeq() == S_MovableRelease) {
+    DEBUG(dbgs() << "        Found nested releases (i.e. a release pair)\n");
+    NestingDetected = true;
+  }
+
+  MDNode *ReleaseMetadata =
+      I->getMetadata(Cache.get(ARCMDKindID::ImpreciseRelease));
+  Sequence NewSeq = ReleaseMetadata ? S_MovableRelease : S_Release;
+  ResetSequenceProgress(NewSeq);
+  SetReleaseMetadata(ReleaseMetadata);
+  SetKnownSafe(HasKnownPositiveRefCount());
+  SetTailCallRelease(cast<CallInst>(I)->isTailCall());
+  InsertCall(I);
+  SetKnownPositiveRefCount();
+  return NestingDetected;
+}
+
+bool BottomUpPtrState::MatchWithRetain() {
+  SetKnownPositiveRefCount();
+
+  Sequence OldSeq = GetSeq();
+  switch (OldSeq) {
+  case S_Stop:
+  case S_Release:
+  case S_MovableRelease:
+  case S_Use:
+    // If OldSeq is not S_Use or OldSeq is S_Use and we are tracking an
+    // imprecise release, clear our reverse insertion points.
+    if (OldSeq != S_Use || IsTrackingImpreciseReleases())
+      ClearReverseInsertPts();
+    LLVM_FALLTHROUGH;
+  case S_CanRelease:
+    return true;
+  case S_None:
+    return false;
+  case S_Retain:
+    llvm_unreachable("bottom-up pointer in retain state!");
+  }
+  llvm_unreachable("Sequence unknown enum value");
+}
+
+bool BottomUpPtrState::HandlePotentialAlterRefCount(Instruction *Inst,
+                                                    const Value *Ptr,
+                                                    ProvenanceAnalysis &PA,
+                                                    ARCInstKind Class) {
+  Sequence S = GetSeq();
+
+  // Check for possible releases.
+  if (!CanAlterRefCount(Inst, Ptr, PA, Class))
+    return false;
+
+  DEBUG(dbgs() << "            CanAlterRefCount: Seq: " << S << "; " << *Ptr
+               << "\n");
+  switch (S) {
+  case S_Use:
+    SetSeq(S_CanRelease);
+    return true;
+  case S_CanRelease:
+  case S_Release:
+  case S_MovableRelease:
+  case S_Stop:
+  case S_None:
+    return false;
+  case S_Retain:
+    llvm_unreachable("bottom-up pointer in retain state!");
+  }
+  llvm_unreachable("Sequence unknown enum value");
+}
+
+void BottomUpPtrState::HandlePotentialUse(BasicBlock *BB, Instruction *Inst,
+                                          const Value *Ptr,
+                                          ProvenanceAnalysis &PA,
+                                          ARCInstKind Class) {
+  auto SetSeqAndInsertReverseInsertPt = [&](Sequence NewSeq){
+    assert(!HasReverseInsertPts());
+    SetSeq(NewSeq);
+    // If this is an invoke instruction, we're scanning it as part of
+    // one of its successor blocks, since we can't insert code after it
+    // in its own block, and we don't want to split critical edges.
+    BasicBlock::iterator InsertAfter;
+    if (isa<InvokeInst>(Inst)) {
+      const auto IP = BB->getFirstInsertionPt();
+      InsertAfter = IP == BB->end() ? std::prev(BB->end()) : IP;
+    } else {
+      InsertAfter = std::next(Inst->getIterator());
+    }
+    InsertReverseInsertPt(&*InsertAfter);
+  };
+
+  // Check for possible direct uses.
+  switch (GetSeq()) {
+  case S_Release:
+  case S_MovableRelease:
+    if (CanUse(Inst, Ptr, PA, Class)) {
+      DEBUG(dbgs() << "            CanUse: Seq: " << GetSeq() << "; " << *Ptr
+                   << "\n");
+      SetSeqAndInsertReverseInsertPt(S_Use);
+    } else if (Seq == S_Release && IsUser(Class)) {
+      DEBUG(dbgs() << "            PreciseReleaseUse: Seq: " << GetSeq() << "; "
+                   << *Ptr << "\n");
+      // Non-movable releases depend on any possible objc pointer use.
+      SetSeqAndInsertReverseInsertPt(S_Stop);
+    } else if (const auto *Call = getreturnRVOperand(*Inst, Class)) {
+      if (CanUse(Call, Ptr, PA, GetBasicARCInstKind(Call))) {
+        DEBUG(dbgs() << "            ReleaseUse: Seq: " << GetSeq() << "; "
+                     << *Ptr << "\n");
+        SetSeqAndInsertReverseInsertPt(S_Stop);
+      }
+    }
+    break;
+  case S_Stop:
+    if (CanUse(Inst, Ptr, PA, Class)) {
+      DEBUG(dbgs() << "            PreciseStopUse: Seq: " << GetSeq() << "; "
+                   << *Ptr << "\n");
+      SetSeq(S_Use);
+    }
+    break;
+  case S_CanRelease:
+  case S_Use:
+  case S_None:
+    break;
+  case S_Retain:
+    llvm_unreachable("bottom-up pointer in retain state!");
+  }
+}
+
+//===----------------------------------------------------------------------===//
+//                              TopDownPtrState
+//===----------------------------------------------------------------------===//
+
+bool TopDownPtrState::InitTopDown(ARCInstKind Kind, Instruction *I) {
+  bool NestingDetected = false;
+  // Don't do retain+release tracking for ARCInstKind::RetainRV, because
+  // it's
+  // better to let it remain as the first instruction after a call.
+  if (Kind != ARCInstKind::RetainRV) {
+    // If we see two retains in a row on the same pointer. If so, make
+    // a note, and we'll cicle back to revisit it after we've
+    // hopefully eliminated the second retain, which may allow us to
+    // eliminate the first retain too.
+    // Theoretically we could implement removal of nested retain+release
+    // pairs by making PtrState hold a stack of states, but this is
+    // simple and avoids adding overhead for the non-nested case.
+    if (GetSeq() == S_Retain)
+      NestingDetected = true;
+
+    ResetSequenceProgress(S_Retain);
+    SetKnownSafe(HasKnownPositiveRefCount());
+    InsertCall(I);
+  }
+
+  SetKnownPositiveRefCount();
+  return NestingDetected;
+}
+
+bool TopDownPtrState::MatchWithRelease(ARCMDKindCache &Cache,
+                                       Instruction *Release) {
+  ClearKnownPositiveRefCount();
+
+  Sequence OldSeq = GetSeq();
+
+  MDNode *ReleaseMetadata =
+      Release->getMetadata(Cache.get(ARCMDKindID::ImpreciseRelease));
+
+  switch (OldSeq) {
+  case S_Retain:
+  case S_CanRelease:
+    if (OldSeq == S_Retain || ReleaseMetadata != nullptr)
+      ClearReverseInsertPts();
+    LLVM_FALLTHROUGH;
+  case S_Use:
+    SetReleaseMetadata(ReleaseMetadata);
+    SetTailCallRelease(cast<CallInst>(Release)->isTailCall());
+    return true;
+  case S_None:
+    return false;
+  case S_Stop:
+  case S_Release:
+  case S_MovableRelease:
+    llvm_unreachable("top-down pointer in bottom up state!");
+  }
+  llvm_unreachable("Sequence unknown enum value");
+}
+
+bool TopDownPtrState::HandlePotentialAlterRefCount(Instruction *Inst,
+                                                   const Value *Ptr,
+                                                   ProvenanceAnalysis &PA,
+                                                   ARCInstKind Class) {
+  // Check for possible releases. Treat clang.arc.use as a releasing instruction
+  // to prevent sinking a retain past it.
+  if (!CanAlterRefCount(Inst, Ptr, PA, Class) &&
+      Class != ARCInstKind::IntrinsicUser)
+    return false;
+
+  DEBUG(dbgs() << "            CanAlterRefCount: Seq: " << GetSeq() << "; " << *Ptr
+               << "\n");
+  ClearKnownPositiveRefCount();
+  switch (GetSeq()) {
+  case S_Retain:
+    SetSeq(S_CanRelease);
+    assert(!HasReverseInsertPts());
+    InsertReverseInsertPt(Inst);
+
+    // One call can't cause a transition from S_Retain to S_CanRelease
+    // and S_CanRelease to S_Use. If we've made the first transition,
+    // we're done.
+    return true;
+  case S_Use:
+  case S_CanRelease:
+  case S_None:
+    return false;
+  case S_Stop:
+  case S_Release:
+  case S_MovableRelease:
+    llvm_unreachable("top-down pointer in release state!");
+  }
+  llvm_unreachable("covered switch is not covered!?");
+}
+
+void TopDownPtrState::HandlePotentialUse(Instruction *Inst, const Value *Ptr,
+                                         ProvenanceAnalysis &PA,
+                                         ARCInstKind Class) {
+  // Check for possible direct uses.
+  switch (GetSeq()) {
+  case S_CanRelease:
+    if (!CanUse(Inst, Ptr, PA, Class))
+      return;
+    DEBUG(dbgs() << "             CanUse: Seq: " << GetSeq() << "; " << *Ptr
+                 << "\n");
+    SetSeq(S_Use);
+    return;
+  case S_Retain:
+  case S_Use:
+  case S_None:
+    return;
+  case S_Stop:
+  case S_Release:
+  case S_MovableRelease:
+    llvm_unreachable("top-down pointer in release state!");
+  }
+}