C++ AliasSet类代码示例

/// remove - Remove the specified (potentially non-empty) alias set from the
/// tracker.
void AliasSetTracker::remove(AliasSet &AS) {
  // Drop all call sites.
  AS.UnknownInsts.clear();
  
  // Clear the alias set.
  unsigned NumRefs = 0;
  while (!AS.empty()) {
    AliasSet::PointerRec *P = AS.PtrList;

    Value *ValToRemove = P->getValue();
    
    // Unlink and delete entry from the list of values.
    P->eraseFromList();
    
    // Remember how many references need to be dropped.
    ++NumRefs;

    // Finally, remove the entry.
    PointerMap.erase(ValToRemove);
  }
  
  // Stop using the alias set, removing it.
  AS.RefCount -= NumRefs;
  if (AS.RefCount == 0)
    AS.removeFromTracker(*this);
}

// deleteValue method - This method is used to remove a pointer value from the
// AliasSetTracker entirely.  It should be used when an instruction is deleted
// from the program to update the AST.  If you don't use this, you would have
// dangling pointers to deleted instructions.
//
void AliasSetTracker::deleteValue(Value *PtrVal) {
  // Notify the alias analysis implementation that this value is gone.
  AA.deleteValue(PtrVal);

  // If this is a call instruction, remove the callsite from the appropriate
  // AliasSet.
  CallSite CS = CallSite::get(PtrVal);
  if (CS.getInstruction()) {
    Function *F = CS.getCalledFunction();
    if (!F || !AA.doesNotAccessMemory(F)) {
      if (AliasSet *AS = findAliasSetForCallSite(CS))
        AS->removeCallSite(CS);
    }
  }

  // First, look up the PointerRec for this pointer.
  hash_map<Value*, AliasSet::PointerRec>::iterator I = PointerMap.find(PtrVal);
  if (I == PointerMap.end()) return;  // Noop

  // If we found one, remove the pointer from the alias set it is in.
  AliasSet::HashNodePair &PtrValEnt = *I;
  AliasSet *AS = PtrValEnt.second.getAliasSet(*this);

  // Unlink from the list of values...
  PtrValEnt.second.removeFromList();
  // Stop using the alias set
  AS->dropRef(*this);
  PointerMap.erase(I);
}

// deleteValue method - This method is used to remove a pointer value from the
// AliasSetTracker entirely.  It should be used when an instruction is deleted
// from the program to update the AST.  If you don't use this, you would have
// dangling pointers to deleted instructions.
//
void AliasSetTracker::deleteValue(Value *PtrVal) {
  // Notify the alias analysis implementation that this value is gone.
  AA.deleteValue(PtrVal);

  // If this is a call instruction, remove the callsite from the appropriate
  // AliasSet (if present).
  if (Instruction *Inst = dyn_cast<Instruction>(PtrVal)) {
    if (Inst->mayReadOrWriteMemory()) {
      // Scan all the alias sets to see if this call site is contained.
      for (iterator I = begin(), E = end(); I != E; ++I) {
        if (I->Forward) continue;
        
        I->removeUnknownInst(Inst);
      }
    }
  }

  // First, look up the PointerRec for this pointer.
  PointerMapType::iterator I = PointerMap.find(PtrVal);
  if (I == PointerMap.end()) return;  // Noop

  // If we found one, remove the pointer from the alias set it is in.
  AliasSet::PointerRec *PtrValEnt = I->second;
  AliasSet *AS = PtrValEnt->getAliasSet(*this);

  // Unlink and delete from the list of values.
  PtrValEnt->eraseFromList();
  
  // Stop using the alias set.
  AS->dropRef(*this);
  
  PointerMap.erase(I);
}

/// mergeSetIn - Merge the specified alias set into this alias set.
///
void AliasSet::mergeSetIn(AliasSet &AS, AliasSetTracker &AST) {
  assert(!AS.Forward && "Alias set is already forwarding!");
  assert(!Forward && "This set is a forwarding set!!");

  bool WasMustAlias = (Alias == SetMustAlias);
  // Update the alias and access types of this set...
  Access |= AS.Access;
  Alias  |= AS.Alias;

  if (Alias == SetMustAlias) {
    // Check that these two merged sets really are must aliases.  Since both
    // used to be must-alias sets, we can just check any pointer from each set
    // for aliasing.
    AliasAnalysis &AA = AST.getAliasAnalysis();
    PointerRec *L = getSomePointer();
    PointerRec *R = AS.getSomePointer();

    // If the pointers are not a must-alias pair, this set becomes a may alias.
    if (AA.alias(MemoryLocation(L->getValue(), L->getSize(), L->getAAInfo()),
                 MemoryLocation(R->getValue(), R->getSize(), R->getAAInfo())) !=
        MustAlias)
      Alias = SetMayAlias;
  }

  if (Alias == SetMayAlias) {
    if (WasMustAlias)
      AST.TotalMayAliasSetSize += size();
    if (AS.Alias == SetMustAlias)
      AST.TotalMayAliasSetSize += AS.size();
  }

  bool ASHadUnknownInsts = !AS.UnknownInsts.empty();
  if (UnknownInsts.empty()) {            // Merge call sites...
    if (ASHadUnknownInsts) {
      std::swap(UnknownInsts, AS.UnknownInsts);
      addRef();
    }
  } else if (ASHadUnknownInsts) {
    UnknownInsts.insert(UnknownInsts.end(), AS.UnknownInsts.begin(), AS.UnknownInsts.end());
    AS.UnknownInsts.clear();
  }

  AS.Forward = this; // Forward across AS now...
  addRef();          // AS is now pointing to us...

  // Merge the list of constituent pointers...
  if (AS.PtrList) {
    SetSize += AS.size();
    AS.SetSize = 0;
    *PtrListEnd = AS.PtrList;
    AS.PtrList->setPrevInList(PtrListEnd);
    PtrListEnd = AS.PtrListEnd;

    AS.PtrList = nullptr;
    AS.PtrListEnd = &AS.PtrList;
    assert(*AS.PtrListEnd == nullptr && "End of list is not null?");
  }
  if (ASHadUnknownInsts)
    AS.dropRef(AST);
}

// deleteValue method - This method is used to remove a pointer value from the
// AliasSetTracker entirely.  It should be used when an instruction is deleted
// from the program to update the AST.  If you don't use this, you would have
// dangling pointers to deleted instructions.
//
void AliasSetTracker::deleteValue(Value *PtrVal) {
  // Notify the alias analysis implementation that this value is gone.
  AA.deleteValue(PtrVal);

  // If this is a call instruction, remove the callsite from the appropriate
  // AliasSet.
  CallSite CS = CallSite::get(PtrVal);
  if (CS.getInstruction())
    if (!AA.doesNotAccessMemory(CS))
      if (AliasSet *AS = findAliasSetForCallSite(CS))
        AS->removeCallSite(CS);

  // First, look up the PointerRec for this pointer.
  PointerMapType::iterator I = PointerMap.find(PtrVal);
  if (I == PointerMap.end()) return;  // Noop

  // If we found one, remove the pointer from the alias set it is in.
  AliasSet::PointerRec *PtrValEnt = I->second;
  AliasSet *AS = PtrValEnt->getAliasSet(*this);

  // Unlink and delete from the list of values.
  PtrValEnt->eraseFromList();
  
  // Stop using the alias set.
  AS->dropRef(*this);
  
  PointerMap.erase(I);
}

/// remove - Remove the specified (potentially non-empty) alias set from the
/// tracker.
void AliasSetTracker::remove(AliasSet &AS) {
  // Drop all call sites.
  AS.CallSites.clear();
  
  // Clear the alias set.
  unsigned NumRefs = 0;
  while (!AS.empty()) {
    AliasSet::HashNodePair *P = AS.PtrList;
    
    // Unlink from the list of values.
    P->second.removeFromList();
    
    // Remember how many references need to be dropped.
    ++NumRefs;

    // Finally, remove the entry.
    Value *Remove = P->first;   // Take a copy because it is invalid to pass
    PointerMap.erase(Remove);   // a reference to the data being erased.
  }
  
  // Stop using the alias set, removing it.
  AS.RefCount -= NumRefs;
  if (AS.RefCount == 0)
    AS.removeFromTracker(*this);
}

/// mergeAliasSetsForPointer - Given a pointer, merge all alias sets that may
/// alias the pointer. Return the unified set, or nullptr if no set that aliases
/// the pointer was found. MustAliasAll is updated to true/false if the pointer
/// is found to MustAlias all the sets it merged.
AliasSet *AliasSetTracker::mergeAliasSetsForPointer(const Value *Ptr,
                                                    LocationSize Size,
                                                    const AAMDNodes &AAInfo,
                                                    bool &MustAliasAll) {
  AliasSet *FoundSet = nullptr;
  AliasResult AllAR = MustAlias;
  for (iterator I = begin(), E = end(); I != E;) {
    iterator Cur = I++;
    if (Cur->Forward)
      continue;

    AliasResult AR = Cur->aliasesPointer(Ptr, Size, AAInfo, AA);
    if (AR == NoAlias)
      continue;

    AllAR =
        AliasResult(AllAR & AR); // Possible downgrade to May/Partial, even No

    if (!FoundSet) {
      // If this is the first alias set ptr can go into, remember it.
      FoundSet = &*Cur;
    } else {
      // Otherwise, we must merge the sets.
      FoundSet->mergeSetIn(*Cur, *this);
    }
  }

  MustAliasAll = (AllAR == MustAlias);
  return FoundSet;
}

void AliasSetTracker::addUnknown(Instruction *Inst) {
  if (isa<DbgInfoIntrinsic>(Inst))
    return; // Ignore DbgInfo Intrinsics.

  if (auto *II = dyn_cast<IntrinsicInst>(Inst)) {
    // These intrinsics will show up as affecting memory, but they are just
    // markers.
    switch (II->getIntrinsicID()) {
    default:
      break;
      // FIXME: Add lifetime/invariant intrinsics (See: PR30807).
    case Intrinsic::assume:
    case Intrinsic::sideeffect:
      return;
    }
  }
  if (!Inst->mayReadOrWriteMemory())
    return; // doesn't alias anything

  AliasSet *AS = findAliasSetForUnknownInst(Inst);
  if (AS) {
    AS->addUnknownInst(Inst, AA);
    return;
  }
  AliasSets.push_back(new AliasSet());
  AS = &AliasSets.back();
  AS->addUnknownInst(Inst, AA);
}

AliasSet *AliasSetTracker::findAliasSetForUnknownInst(Instruction *Inst) {
  AliasSet *FoundSet = nullptr;
  for (iterator I = begin(), E = end(); I != E;) {
    iterator Cur = I++;
    if (Cur->Forward || !Cur->aliasesUnknownInst(Inst, AA))
      continue;
    if (!FoundSet)            // If this is the first alias set ptr can go into.
      FoundSet = &*Cur;       // Remember it.
    else   // Otherwise, we must merge the sets.
      FoundSet->mergeSetIn(*Cur, *this);     // Merge in contents.
  }
  return FoundSet;
}

AliasSet *AliasSetTracker::findAliasSetForUnknownInst(Instruction *Inst) {
  AliasSet *FoundSet = 0;
  for (iterator I = begin(), E = end(); I != E; ++I) {
    if (I->Forward || !I->aliasesUnknownInst(Inst, AA))
      continue;
    
    if (FoundSet == 0)        // If this is the first alias set ptr can go into.
      FoundSet = I;           // Remember it.
    else if (!I->Forward)     // Otherwise, we must merge the sets.
      FoundSet->mergeSetIn(*I, *this);     // Merge in contents.
  }
  return FoundSet;
}

AliasSet *AliasSetTracker::findAliasSetForCallSite(CallSite CS) {
  AliasSet *FoundSet = 0;
  for (iterator I = begin(), E = end(); I != E; ++I)
    if (!I->Forward && I->aliasesCallSite(CS, AA)) {
      if (FoundSet == 0) {  // If this is the first alias set ptr can go into.
        FoundSet = I;       // Remember it.
      } else if (!I->Forward) {     // Otherwise, we must merge the sets.
        FoundSet->mergeSetIn(*I, *this);     // Merge in contents.
      }
    }

  return FoundSet;
}

/// findAliasSetForPointer - Given a pointer, find the one alias set to put the
/// instruction referring to the pointer into.  If there are multiple alias sets
/// that may alias the pointer, merge them together and return the unified set.
///
AliasSet *AliasSetTracker::findAliasSetForPointer(const Value *Ptr,
                                                  unsigned Size) {
  AliasSet *FoundSet = 0;
  for (iterator I = begin(), E = end(); I != E; ++I)
    if (!I->Forward && I->aliasesPointer(Ptr, Size, AA)) {
      if (FoundSet == 0) {  // If this is the first alias set ptr can go into.
        FoundSet = I;       // Remember it.
      } else {              // Otherwise, we must merge the sets.
        FoundSet->mergeSetIn(*I, *this);     // Merge in contents.
      }
    }

  return FoundSet;
}

/// findAliasSetForPointer - Given a pointer, find the one alias set to put the
/// instruction referring to the pointer into.  If there are multiple alias sets
/// that may alias the pointer, merge them together and return the unified set.
///
AliasSet *AliasSetTracker::findAliasSetForPointer(const Value *Ptr,
                                                  uint64_t Size,
                                                  const MDNode *TBAAInfo) {
  AliasSet *FoundSet = 0;
  for (iterator I = begin(), E = end(); I != E; ++I) {
    if (I->Forward || !I->aliasesPointer(Ptr, Size, TBAAInfo, AA)) continue;
    
    if (FoundSet == 0) {  // If this is the first alias set ptr can go into.
      FoundSet = I;       // Remember it.
    } else {              // Otherwise, we must merge the sets.
      FoundSet->mergeSetIn(*I, *this);     // Merge in contents.
    }
  }

  return FoundSet;
}

// copyValue - This method should be used whenever a preexisting value in the
// program is copied or cloned, introducing a new value.  Note that it is ok for
// clients that use this method to introduce the same value multiple times: if
// the tracker already knows about a value, it will ignore the request.
//
void AliasSetTracker::copyValue(Value *From, Value *To) {
  // Notify the alias analysis implementation that this value is copied.
  AA.copyValue(From, To);

  // First, look up the PointerRec for this pointer.
  hash_map<Value*, AliasSet::PointerRec>::iterator I = PointerMap.find(From);
  if (I == PointerMap.end() || !I->second.hasAliasSet())
    return;  // Noop

  AliasSet::HashNodePair &Entry = getEntryFor(To);
  if (Entry.second.hasAliasSet()) return;    // Already in the tracker!

  // Add it to the alias set it aliases...
  AliasSet *AS = I->second.getAliasSet(*this);
  AS->addPointer(*this, Entry, I->second.getSize(), true);
}

bool AliasSetTracker::add(CallSite CS) {
  if (Function *F = CS.getCalledFunction())
    if (AA.doesNotAccessMemory(F))
      return true; // doesn't alias anything

  AliasSet *AS = findAliasSetForCallSite(CS);
  if (!AS) {
    AliasSets.push_back(new AliasSet());
    AS = &AliasSets.back();
    AS->addCallSite(CS, AA);
    return true;
  } else {
    AS->addCallSite(CS, AA);
    return false;
  }
}