C++ AliasSetTracker类代码示例

void AliasSetTracker::add(const AliasSetTracker &AST) {
  assert(&AA == &AST.AA &&
         "Merging AliasSetTracker objects with different Alias Analyses!");

  // Loop over all of the alias sets in AST, adding the pointers contained
  // therein into the current alias sets.  This can cause alias sets to be
  // merged together in the current AST.
  for (const_iterator I = AST.begin(), E = AST.end(); I != E; ++I) {
    if (I->Forward) continue;   // Ignore forwarding alias sets
    
    AliasSet &AS = const_cast<AliasSet&>(*I);

    // If there are any call sites in the alias set, add them to this AST.
    for (unsigned i = 0, e = AS.UnknownInsts.size(); i != e; ++i)
      add(AS.UnknownInsts[i]);

    // Loop over all of the pointers in this alias set.
    bool X;
    for (AliasSet::iterator ASI = AS.begin(), E = AS.end(); ASI != E; ++ASI) {
      AliasSet &NewAS = addPointer(ASI.getPointer(), ASI.getSize(),
                                   ASI.getTBAAInfo(),
                                   (AliasSet::AccessType)AS.AccessTy, X);
      if (AS.isVolatile()) NewAS.setVolatile();
    }
  }
}

/// cloneBasicBlockAnalysis - Simple Analysis hook. Clone alias set info.
void LICM::cloneBasicBlockAnalysis(BasicBlock *From, BasicBlock *To, Loop *L) {
  AliasSetTracker *AST = LoopToAliasMap[L];
  if (!AST)
    return;

  AST->copyValue(From, To);
}

/// deleteAnalysisValue - Simple Analysis hook. Delete value V from alias
/// set.
void LICM::deleteAnalysisValue(Value *V, Loop *L) {
  AliasSetTracker *AST = LoopToAliasMap[L];
  if (!AST)
    return;

  AST->deleteValue(V);
}

void DeadStoreEliminationPass::printSet(raw_ostream &O,
    AliasSetTracker &myset) const {
  O << "    {\n";
  for (AliasSetTracker::const_iterator it = myset.begin();
      it != myset.end(); ++it) {
    O << "    ";
    (*it).print(O);
  }
  O << "    }\n";
}

void AliasSet::addPointer(AliasSetTracker &AST, PointerRec &Entry,
                          uint64_t Size, const MDNode *TBAAInfo,
                          bool KnownMustAlias) {
  assert(!Entry.hasAliasSet() && "Entry already in set!");

  // Check to see if we have to downgrade to _may_ alias.
  if (isMustAlias() && !KnownMustAlias)
    if (PointerRec *P = getSomePointer()) {
      AliasAnalysis &AA = AST.getAliasAnalysis();
      AliasAnalysis::AliasResult Result =
        AA.alias(AliasAnalysis::Location(P->getValue(), P->getSize(),
                                         P->getTBAAInfo()),
                 AliasAnalysis::Location(Entry.getValue(), Size, TBAAInfo));
      if (Result != AliasAnalysis::MustAlias)
        AliasTy = MayAlias;
      else                  // First entry of must alias must have maximum size!
        P->updateSizeAndTBAAInfo(Size, TBAAInfo);
      assert(Result != AliasAnalysis::NoAlias && "Cannot be part of must set!");
    }

  Entry.setAliasSet(this);
  Entry.updateSizeAndTBAAInfo(Size, TBAAInfo);

  // Add it to the end of the list...
  assert(*PtrListEnd == 0 && "End of list is not null?");
  *PtrListEnd = &Entry;
  PtrListEnd = Entry.setPrevInList(PtrListEnd);
  assert(*PtrListEnd == 0 && "End of list is not null?");
  addRef();               // Entry points to alias set.
}

/// 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);
}

void AliasSet::addPointer(AliasSetTracker &AST, HashNodePair &Entry,
                          unsigned Size, bool KnownMustAlias) {
  assert(!Entry.second.hasAliasSet() && "Entry already in set!");

  // Check to see if we have to downgrade to _may_ alias.
  if (isMustAlias() && !KnownMustAlias)
    if (HashNodePair *P = getSomePointer()) {
      AliasAnalysis &AA = AST.getAliasAnalysis();
      AliasAnalysis::AliasResult Result =
        AA.alias(P->first, P->second.getSize(), Entry.first, Size);
      if (Result == AliasAnalysis::MayAlias)
        AliasTy = MayAlias;
      else                  // First entry of must alias must have maximum size!
        P->second.updateSize(Size);
      assert(Result != AliasAnalysis::NoAlias && "Cannot be part of must set!");
    }

  Entry.second.setAliasSet(this);
  Entry.second.updateSize(Size);

  // Add it to the end of the list...
  assert(*PtrListEnd == 0 && "End of list is not null?");
  *PtrListEnd = &Entry;
  PtrListEnd = Entry.second.setPrevInList(PtrListEnd);
  assert(*PtrListEnd == 0 && "End of list is not null?");
  addRef();               // Entry points to alias set...
}

void AliasSetTracker::add(const AliasSetTracker &AST) {
  assert(&AA == &AST.AA &&
         "Merging AliasSetTracker objects with different Alias Analyses!");

  // Loop over all of the alias sets in AST, adding the pointers contained
  // therein into the current alias sets.  This can cause alias sets to be
  // merged together in the current AST.
  for (const_iterator I = AST.begin(), E = AST.end(); I != E; ++I)
    if (!I->Forward) {   // Ignore forwarding alias sets
      AliasSet &AS = const_cast<AliasSet&>(*I);

      // If there are any call sites in the alias set, add them to this AST.
      for (unsigned i = 0, e = AS.CallSites.size(); i != e; ++i)
        add(AS.CallSites[i]);

      // Loop over all of the pointers in this alias set...
      AliasSet::iterator I = AS.begin(), E = AS.end();
      bool X;
      for (; I != E; ++I)
        addPointer(I.getPointer(), I.getSize(),
                   (AliasSet::AccessType)AS.AccessTy, X);
    }
}

/// 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!!");

  // Update the alias and access types of this set...
  AccessTy |= AS.AccessTy;
  AliasTy  |= AS.AliasTy;
  Volatile |= AS.Volatile;

  if (AliasTy == MustAlias) {
    // 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(AliasAnalysis::Location(L->getValue(),
                                         L->getSize(),
                                         L->getTBAAInfo()),
                 AliasAnalysis::Location(R->getValue(),
                                         R->getSize(),
                                         R->getTBAAInfo()))
        != AliasAnalysis::MustAlias)
      AliasTy = MayAlias;
  }

  if (CallSites.empty()) {            // Merge call sites...
    if (!AS.CallSites.empty())
      std::swap(CallSites, AS.CallSites);
  } else if (!AS.CallSites.empty()) {
    CallSites.insert(CallSites.end(), AS.CallSites.begin(), AS.CallSites.end());
    AS.CallSites.clear();
  }

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

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

    AS.PtrList = 0;
    AS.PtrListEnd = &AS.PtrList;
    assert(*AS.PtrListEnd == 0 && "End of list is not null?");
  }
}

void AliasSet::addPointer(AliasSetTracker &AST, PointerRec &Entry,
                          LocationSize Size, const AAMDNodes &AAInfo,
                          bool KnownMustAlias) {
  assert(!Entry.hasAliasSet() && "Entry already in set!");

  // Check to see if we have to downgrade to _may_ alias.
  if (isMustAlias() && !KnownMustAlias)
    if (PointerRec *P = getSomePointer()) {
      AliasAnalysis &AA = AST.getAliasAnalysis();
      AliasResult Result =
          AA.alias(MemoryLocation(P->getValue(), P->getSize(), P->getAAInfo()),
                   MemoryLocation(Entry.getValue(), Size, AAInfo));
      if (Result != MustAlias) {
        Alias = SetMayAlias;
        AST.TotalMayAliasSetSize += size();
      } else {
        // First entry of must alias must have maximum size!
        P->updateSizeAndAAInfo(Size, AAInfo);
      }
      assert(Result != NoAlias && "Cannot be part of must set!");
    }

  Entry.setAliasSet(this);
  Entry.updateSizeAndAAInfo(Size, AAInfo);

  // Add it to the end of the list...
  ++SetSize;
  assert(*PtrListEnd == nullptr && "End of list is not null?");
  *PtrListEnd = &Entry;
  PtrListEnd = Entry.setPrevInList(PtrListEnd);
  assert(*PtrListEnd == nullptr && "End of list is not null?");
  // Entry points to alias set.
  addRef();

  if (Alias == SetMayAlias)
    AST.TotalMayAliasSetSize++;
}

void AliasSet::removeFromTracker(AliasSetTracker &AST) {
  assert(RefCount == 0 && "Cannot remove non-dead alias set from tracker!");
  AST.removeAliasSet(this);
}

DeadMemOpElimination::instr_iterator
DeadMemOpElimination::handleMemOp(instr_iterator I, DefMapTy &Defs,
                                  AliasSetTracker &AST) {
  MachineInstr *MI = I;

  MachineMemOperand *MO = *MI->memoperands_begin();
  // AliasAnalysis cannot handle offset right now, so we pretend to write a
  // a big enough size to the location pointed by the base pointer.
  uint64_t Size = MO->getSize() + MO->getOffset();
  AliasSet *ASet = &AST.getAliasSetForPointer(const_cast<Value*>(MO->getValue()),
                                              Size, 0);

  MachineInstr *&LastMI = Defs[ASet];

  bool canHandleLastStore = LastMI && ASet->isMustAlias()
                            && LastMI->getOpcode() != VTM::VOpInternalCall
                            // FIXME: We may need to remember the last
                            // definition for all predicates.
                            && isPredIdentical(LastMI, MI);

  if (canHandleLastStore) {
    MachineMemOperand *LastMO = *LastMI->memoperands_begin();
    // We can only handle last store if and only if their memory operand have
    // the must-alias address and the same size.
    canHandleLastStore = LastMO->getSize() == MO->getSize()
                         && !LastMO->isVolatile()
                         && MachineMemOperandAlias(MO, LastMO, AA, SE)
                            == AliasAnalysis::MustAlias;
  }

  // FIXME: These elimination is only valid if we are in single-thread mode!
  if (VInstrInfo::mayStore(MI)) {
    if (canHandleLastStore) {
      // Dead store find, remove it.
      LastMI->eraseFromParent();
      ++DeadStoreEliminated;
    }

    // Update the definition.
    LastMI = MI;
    return I;
  }

  // Now MI is a load.
  if (!canHandleLastStore) return I;

  // Loading the value that just be stored, the load is not necessary.
  MachineOperand LoadedMO = MI->getOperand(0);
  MachineOperand StoredMO = LastMI->getOperand(2);

  // Simply replace the load by a copy.
  DebugLoc dl = MI->getDebugLoc();
  I = *BuildMI(*MI->getParent(), I, dl, VInstrInfo::getDesc(VTM::VOpMove))
        .addOperand(LoadedMO).addOperand(StoredMO).
        addOperand(*VInstrInfo::getPredOperand(MI)).
        addOperand(*VInstrInfo::getTraceOperand(MI));

  MI->eraseFromParent();
  ++DeadLoadEliminated;
  return I;
}