C++ StoreInst::isSimple方法代码示例

static bool unpackStoreToAggregate(InstCombiner &IC, StoreInst &SI) {
    // FIXME: We could probably with some care handle both volatile and atomic
    // stores here but it isn't clear that this is important.
    if (!SI.isSimple())
        return false;

    Value *V = SI.getValueOperand();
    Type *T = V->getType();

    if (!T->isAggregateType())
        return false;

    if (auto *ST = dyn_cast<StructType>(T)) {
        // If the struct only have one element, we unpack.
        if (ST->getNumElements() == 1) {
            V = IC.Builder->CreateExtractValue(V, 0);
            combineStoreToNewValue(IC, SI, V);
            return true;
        }
    }

    if (auto *AT = dyn_cast<ArrayType>(T)) {
        // If the array only have one element, we unpack.
        if (AT->getNumElements() == 1) {
            V = IC.Builder->CreateExtractValue(V, 0);
            combineStoreToNewValue(IC, SI, V);
            return true;
        }
    }

    return false;
}

bool Scalarizer::visitStoreInst(StoreInst &SI) {
  if (!ScalarizeLoadStore)
    return false;
  if (!SI.isSimple())
    return false;

  VectorLayout Layout;
  Value *FullValue = SI.getValueOperand();
  if (!getVectorLayout(FullValue->getType(), SI.getAlignment(), Layout))
    return false;

  unsigned NumElems = Layout.VecTy->getNumElements();
  IRBuilder<> Builder(SI.getParent(), &SI);
  Scatterer Ptr = scatter(&SI, SI.getPointerOperand());
  Scatterer Val = scatter(&SI, FullValue);

  ValueVector Stores;
  Stores.resize(NumElems);
  for (unsigned I = 0; I < NumElems; ++I) {
    unsigned Align = Layout.getElemAlign(I);
    Stores[I] = Builder.CreateAlignedStore(Val[I], Ptr[I], Align);
  }
  transferMetadata(&SI, Stores);
  return true;
}

static bool unpackStoreToAggregate(InstCombiner &IC, StoreInst &SI) {
  // FIXME: We could probably with some care handle both volatile and atomic
  // stores here but it isn't clear that this is important.
  if (!SI.isSimple())
    return false;

  Value *V = SI.getValueOperand();
  Type *T = V->getType();

  if (!T->isAggregateType())
    return false;

  if (auto *ST = dyn_cast<StructType>(T)) {
    // If the struct only have one element, we unpack.
    unsigned Count = ST->getNumElements();
    if (Count == 1) {
      V = IC.Builder->CreateExtractValue(V, 0);
      combineStoreToNewValue(IC, SI, V);
      return true;
    }

    // We don't want to break loads with padding here as we'd loose
    // the knowledge that padding exists for the rest of the pipeline.
    const DataLayout &DL = IC.getDataLayout();
    auto *SL = DL.getStructLayout(ST);
    if (SL->hasPadding())
      return false;

    SmallString<16> EltName = V->getName();
    EltName += ".elt";
    auto *Addr = SI.getPointerOperand();
    SmallString<16> AddrName = Addr->getName();
    AddrName += ".repack";
    auto *IdxType = Type::getInt32Ty(ST->getContext());
    auto *Zero = ConstantInt::get(IdxType, 0);
    for (unsigned i = 0; i < Count; i++) {
      Value *Indices[2] = {
        Zero,
        ConstantInt::get(IdxType, i),
      };
      auto *Ptr = IC.Builder->CreateInBoundsGEP(ST, Addr, makeArrayRef(Indices), AddrName);
      auto *Val = IC.Builder->CreateExtractValue(V, i, EltName);
      IC.Builder->CreateStore(Val, Ptr);
    }

    return true;
  }

  if (auto *AT = dyn_cast<ArrayType>(T)) {
    // If the array only have one element, we unpack.
    if (AT->getNumElements() == 1) {
      V = IC.Builder->CreateExtractValue(V, 0);
      combineStoreToNewValue(IC, SI, V);
      return true;
    }
  }

  return false;
}

/// \brief Combine stores to match the type of value being stored.
///
/// The core idea here is that the memory does not have any intrinsic type and
/// where we can we should match the type of a store to the type of value being
/// stored.
///
/// However, this routine must never change the width of a store or the number of
/// stores as that would introduce a semantic change. This combine is expected to
/// be a semantic no-op which just allows stores to more closely model the types
/// of their incoming values.
///
/// Currently, we also refuse to change the precise type used for an atomic or
/// volatile store. This is debatable, and might be reasonable to change later.
/// However, it is risky in case some backend or other part of LLVM is relying
/// on the exact type stored to select appropriate atomic operations.
///
/// \returns true if the store was successfully combined away. This indicates
/// the caller must erase the store instruction. We have to let the caller erase
/// the store instruction sas otherwise there is no way to signal whether it was
/// combined or not: IC.EraseInstFromFunction returns a null pointer.
static bool combineStoreToValueType(InstCombiner &IC, StoreInst &SI) {
  // FIXME: We could probably with some care handle both volatile and atomic
  // stores here but it isn't clear that this is important.
  if (!SI.isSimple())
    return false;

  Value *Ptr = SI.getPointerOperand();
  Value *V = SI.getValueOperand();
  unsigned AS = SI.getPointerAddressSpace();
  SmallVector<std::pair<unsigned, MDNode *>, 8> MD;
  SI.getAllMetadata(MD);

  // Fold away bit casts of the stored value by storing the original type.
  if (auto *BC = dyn_cast<BitCastInst>(V)) {
    V = BC->getOperand(0);
    StoreInst *NewStore = IC.Builder->CreateAlignedStore(
        V, IC.Builder->CreateBitCast(Ptr, V->getType()->getPointerTo(AS)),
        SI.getAlignment());
    for (const auto &MDPair : MD) {
      unsigned ID = MDPair.first;
      MDNode *N = MDPair.second;
      // Note, essentially every kind of metadata should be preserved here! This
      // routine is supposed to clone a store instruction changing *only its
      // type*. The only metadata it makes sense to drop is metadata which is
      // invalidated when the pointer type changes. This should essentially
      // never be the case in LLVM, but we explicitly switch over only known
      // metadata to be conservatively correct. If you are adding metadata to
      // LLVM which pertains to stores, you almost certainly want to add it
      // here.
      switch (ID) {
      case LLVMContext::MD_dbg:
      case LLVMContext::MD_tbaa:
      case LLVMContext::MD_prof:
      case LLVMContext::MD_fpmath:
      case LLVMContext::MD_tbaa_struct:
      case LLVMContext::MD_alias_scope:
      case LLVMContext::MD_noalias:
      case LLVMContext::MD_nontemporal:
      case LLVMContext::MD_mem_parallel_loop_access:
      case LLVMContext::MD_nonnull:
        // All of these directly apply.
        NewStore->setMetadata(ID, N);
        break;

      case LLVMContext::MD_invariant_load:
      case LLVMContext::MD_range:
        break;
      }
    }
    return true;
  }

  // FIXME: We should also canonicalize loads of vectors when their elements are
  // cast to other types.
  return false;
}

bool AMDGPURewriteOutArguments::checkArgumentUses(Value &Arg) const {
  const int MaxUses = 10;
  int UseCount = 0;

  for (Use &U : Arg.uses()) {
    StoreInst *SI = dyn_cast<StoreInst>(U.getUser());
    if (UseCount > MaxUses)
      return false;

    if (!SI) {
      auto *BCI = dyn_cast<BitCastInst>(U.getUser());
      if (!BCI || !BCI->hasOneUse())
        return false;

      // We don't handle multiple stores currently, so stores to aggregate
      // pointers aren't worth the trouble since they are canonically split up.
      Type *DestEltTy = BCI->getType()->getPointerElementType();
      if (DestEltTy->isAggregateType())
        return false;

      // We could handle these if we had a convenient way to bitcast between
      // them.
      Type *SrcEltTy = Arg.getType()->getPointerElementType();
      if (SrcEltTy->isArrayTy())
        return false;

      // Special case handle structs with single members. It is useful to handle
      // some casts between structs and non-structs, but we can't bitcast
      // directly between them.  directly bitcast between them.  Blender uses
      // some casts that look like { <3 x float> }* to <4 x float>*
      if ((SrcEltTy->isStructTy() && (SrcEltTy->getStructNumElements() != 1)))
        return false;

      // Clang emits OpenCL 3-vector type accesses with a bitcast to the
      // equivalent 4-element vector and accesses that, and we're looking for
      // this pointer cast.
      if (DL->getTypeAllocSize(SrcEltTy) != DL->getTypeAllocSize(DestEltTy))
        return false;

      return checkArgumentUses(*BCI);
    }

    if (!SI->isSimple() ||
        U.getOperandNo() != StoreInst::getPointerOperandIndex())
      return false;

    ++UseCount;
  }

  // Skip unused arguments.
  return UseCount > 0;
}

bool CallAnalyzer::visitStore(StoreInst &I) {
  Value *SROAArg;
  DenseMap<Value *, int>::iterator CostIt;
  if (lookupSROAArgAndCost(I.getOperand(0), SROAArg, CostIt)) {
    if (I.isSimple()) {
      accumulateSROACost(CostIt, InlineConstants::InstrCost);
      return true;
    }

    disableSROA(CostIt);
  }

  return false;
}

bool IRTranslator::translateStore(const StoreInst &SI) {
  assert(SI.isSimple() && "only simple loads are supported at the moment");

  MachineFunction &MF = MIRBuilder.getMF();
  unsigned Val = getOrCreateVReg(*SI.getValueOperand());
  unsigned Addr = getOrCreateVReg(*SI.getPointerOperand());
  LLT VTy{*SI.getValueOperand()->getType()},
      PTy{*SI.getPointerOperand()->getType()};

  MIRBuilder.buildStore(
      VTy, PTy, Val, Addr,
      *MF.getMachineMemOperand(MachinePointerInfo(SI.getPointerOperand()),
                               MachineMemOperand::MOStore,
                               VTy.getSizeInBits() / 8, getMemOpAlignment(SI)));
  return true;
}

/// \brief Check loop instructions safe for Loop versioning.
/// It returns true if it's safe else returns false.
/// Consider following:
/// 1) Check all load store in loop body are non atomic & non volatile.
/// 2) Check function call safety, by ensuring its not accessing memory.
/// 3) Loop body shouldn't have any may throw instruction.
bool LoopVersioningLICM::instructionSafeForVersioning(Instruction *I) {
  assert(I != nullptr && "Null instruction found!");
  // Check function call safety
  if (isa<CallInst>(I) && !AA->doesNotAccessMemory(CallSite(I))) {
    DEBUG(dbgs() << "    Unsafe call site found.\n");
    return false;
  }
  // Avoid loops with possiblity of throw
  if (I->mayThrow()) {
    DEBUG(dbgs() << "    May throw instruction found in loop body\n");
    return false;
  }
  // If current instruction is load instructions
  // make sure it's a simple load (non atomic & non volatile)
  if (I->mayReadFromMemory()) {
    LoadInst *Ld = dyn_cast<LoadInst>(I);
    if (!Ld || !Ld->isSimple()) {
      DEBUG(dbgs() << "    Found a non-simple load.\n");
      return false;
    }
    LoadAndStoreCounter++;
    collectStridedAccess(Ld);
    Value *Ptr = Ld->getPointerOperand();
    // Check loop invariant.
    if (SE->isLoopInvariant(SE->getSCEV(Ptr), CurLoop))
      InvariantCounter++;
  }
  // If current instruction is store instruction
  // make sure it's a simple store (non atomic & non volatile)
  else if (I->mayWriteToMemory()) {
    StoreInst *St = dyn_cast<StoreInst>(I);
    if (!St || !St->isSimple()) {
      DEBUG(dbgs() << "    Found a non-simple store.\n");
      return false;
    }
    LoadAndStoreCounter++;
    collectStridedAccess(St);
    Value *Ptr = St->getPointerOperand();
    // Check loop invariant.
    if (SE->isLoopInvariant(SE->getSCEV(Ptr), CurLoop))
      InvariantCounter++;

    IsReadOnlyLoop = false;
  }
  return true;
}

/// \brief Combine stores to match the type of value being stored.
///
/// The core idea here is that the memory does not have any intrinsic type and
/// where we can we should match the type of a store to the type of value being
/// stored.
///
/// However, this routine must never change the width of a store or the number of
/// stores as that would introduce a semantic change. This combine is expected to
/// be a semantic no-op which just allows stores to more closely model the types
/// of their incoming values.
///
/// Currently, we also refuse to change the precise type used for an atomic or
/// volatile store. This is debatable, and might be reasonable to change later.
/// However, it is risky in case some backend or other part of LLVM is relying
/// on the exact type stored to select appropriate atomic operations.
///
/// \returns true if the store was successfully combined away. This indicates
/// the caller must erase the store instruction. We have to let the caller erase
/// the store instruction as otherwise there is no way to signal whether it was
/// combined or not: IC.EraseInstFromFunction returns a null pointer.
static bool combineStoreToValueType(InstCombiner &IC, StoreInst &SI) {
  // FIXME: We could probably with some care handle both volatile and atomic
  // stores here but it isn't clear that this is important.
  if (!SI.isSimple())
    return false;

  Value *V = SI.getValueOperand();

  // Fold away bit casts of the stored value by storing the original type.
  if (auto *BC = dyn_cast<BitCastInst>(V)) {
    V = BC->getOperand(0);
    combineStoreToNewValue(IC, SI, V);
    return true;
  }

  // FIXME: We should also canonicalize loads of vectors when their elements are
  // cast to other types.
  return false;
}

///   store {atomic|volatile} T %val, T* %ptr memory_order, align sizeof(T)
/// becomes:
///   call void @llvm.nacl.atomic.store.i<size>(%val, %ptr, memory_order)
void AtomicVisitor::visitStoreInst(StoreInst &I) {
  return; // XXX EMSCRIPTEN
  if (I.isSimple())
    return;
  PointerHelper<StoreInst> PH(*this, I);
  const NaCl::AtomicIntrinsics::AtomicIntrinsic *Intrinsic =
      findAtomicIntrinsic(I, Intrinsic::nacl_atomic_store, PH.PET);
  checkAlignment(I, I.getAlignment(), PH.BitSize / CHAR_BIT);
  Value *V = I.getValueOperand();
  if (!V->getType()->isIntegerTy()) {
    // The store isn't of an integer type. We define atomics in terms of
    // integers, so bitcast the value to store to an integer of the
    // proper width.
    CastInst *Cast = createCast(I, V, Type::getIntNTy(C, PH.BitSize),
                                V->getName() + ".cast");
    Cast->setDebugLoc(I.getDebugLoc());
    V = Cast;
  }
  checkSizeMatchesType(I, PH.BitSize, V->getType());
  Value *Args[] = {V, PH.P, freezeMemoryOrder(I, I.getOrdering())};
  replaceInstructionWithIntrinsicCall(I, Intrinsic, PH.OriginalPET, PH.PET,
                                      Args);
}

static StoreInst *findSafeStoreForStoreStrongContraction(LoadInst *Load,
                                                         Instruction *Release,
                                                         ProvenanceAnalysis &PA,
                                                         AliasAnalysis *AA) {
  StoreInst *Store = nullptr;
  bool SawRelease = false;

  // Get the location associated with Load.
  MemoryLocation Loc = MemoryLocation::get(Load);

  // Walk down to find the store and the release, which may be in either order.
  for (auto I = std::next(BasicBlock::iterator(Load)),
            E = Load->getParent()->end();
       I != E; ++I) {
    // If we found the store we were looking for and saw the release,
    // break. There is no more work to be done.
    if (Store && SawRelease)
      break;

    // Now we know that we have not seen either the store or the release. If I
    // is the release, mark that we saw the release and continue.
    Instruction *Inst = &*I;
    if (Inst == Release) {
      SawRelease = true;
      continue;
    }

    // Otherwise, we check if Inst is a "good" store. Grab the instruction class
    // of Inst.
    ARCInstKind Class = GetBasicARCInstKind(Inst);

    // If Inst is an unrelated retain, we don't care about it.
    //
    // TODO: This is one area where the optimization could be made more
    // aggressive.
    if (IsRetain(Class))
      continue;

    // If we have seen the store, but not the release...
    if (Store) {
      // We need to make sure that it is safe to move the release from its
      // current position to the store. This implies proving that any
      // instruction in between Store and the Release conservatively can not use
      // the RCIdentityRoot of Release. If we can prove we can ignore Inst, so
      // continue...
      if (!CanUse(Inst, Load, PA, Class)) {
        continue;
      }

      // Otherwise, be conservative and return nullptr.
      return nullptr;
    }

    // Ok, now we know we have not seen a store yet. See if Inst can write to
    // our load location, if it can not, just ignore the instruction.
    if (!(AA->getModRefInfo(Inst, Loc) & MRI_Mod))
      continue;

    Store = dyn_cast<StoreInst>(Inst);

    // If Inst can, then check if Inst is a simple store. If Inst is not a
    // store or a store that is not simple, then we have some we do not
    // understand writing to this memory implying we can not move the load
    // over the write to any subsequent store that we may find.
    if (!Store || !Store->isSimple())
      return nullptr;

    // Then make sure that the pointer we are storing to is Ptr. If so, we
    // found our Store!
    if (Store->getPointerOperand() == Loc.Ptr)
      continue;

    // Otherwise, we have an unknown store to some other ptr that clobbers
    // Loc.Ptr. Bail!
    return nullptr;
  }

  // If we did not find the store or did not see the release, fail.
  if (!Store || !SawRelease)
    return nullptr;

  // We succeeded!
  return Store;
}

/// tryAggregating - When scanning forward over instructions, we look for
/// other loads or stores that could be aggregated with this one.
/// Returns the last instruction added (if one was added) since we might have
/// removed some loads or stores and that might invalidate an iterator.
Instruction *AggregateGlobalOpsOpt::tryAggregating(Instruction *StartInst, Value *StartPtr,
    bool DebugThis) {
  if (TD == 0) return 0;

  Module* M = StartInst->getParent()->getParent()->getParent();
  LLVMContext& Context = StartInst->getContext();

  Type* int8Ty = Type::getInt8Ty(Context);
  Type* sizeTy = Type::getInt64Ty(Context);
  Type* globalInt8PtrTy = int8Ty->getPointerTo(globalSpace);
  bool isLoad = isa<LoadInst>(StartInst);
  bool isStore = isa<StoreInst>(StartInst);
  Instruction *lastAddedInsn = NULL;
  Instruction *LastLoadOrStore = NULL;
 
  SmallVector<Instruction*, 8> toRemove;

  // Okay, so we now have a single global load/store. Scan to find
  // all subsequent stores of the same value to offset from the same pointer.
  // Join these together into ranges, so we can decide whether contiguous blocks
  // are stored.
  MemOpRanges Ranges(*TD);
 
  // Put the first store in since we want to preserve the order.
  Ranges.addInst(0, StartInst);

  BasicBlock::iterator BI = StartInst;
  for (++BI; !isa<TerminatorInst>(BI); ++BI) {

    if( isGlobalLoadOrStore(BI, globalSpace, isLoad, isStore) ) {
      // OK!
    } else {
      // If the instruction is readnone, ignore it, otherwise bail out.  We
      // don't even allow readonly here because we don't want something like:
      // A[1] = 2; strlen(A); A[2] = 2; -> memcpy(A, ...); strlen(A).
      if (BI->mayWriteToMemory())
        break;
      if (isStore && BI->mayReadFromMemory())
        break;
      continue;
    }

    if ( isStore && isa<StoreInst>(BI) ) {
      StoreInst *NextStore = cast<StoreInst>(BI);
      // If this is a store, see if we can merge it in.
      if (!NextStore->isSimple()) break;

      // Check to see if this store is to a constant offset from the start ptr.
      int64_t Offset;
      if (!IsPointerOffset(StartPtr, NextStore->getPointerOperand(), Offset, *TD))
        break;

      Ranges.addStore(Offset, NextStore);
      LastLoadOrStore = NextStore;
    } else {
      LoadInst *NextLoad = cast<LoadInst>(BI);
      if (!NextLoad->isSimple()) break;

      // Check to see if this load is to a constant offset from the start ptr.
      int64_t Offset;
      if (!IsPointerOffset(StartPtr, NextLoad->getPointerOperand(), Offset, *TD))
        break;

      Ranges.addLoad(Offset, NextLoad);
      LastLoadOrStore = NextLoad;
    }
  }

  // If we have no ranges, then we just had a single store with nothing that
  // could be merged in.  This is a very common case of course.
  if (!Ranges.moreThanOneOp())
    return 0;

  // Divide the instructions between StartInst and LastLoadOrStore into
  // addressing, memops, and uses of memops (uses of loads)
  reorderAddressingMemopsUses(StartInst, LastLoadOrStore, DebugThis);

  Instruction* insertBefore = StartInst;
  IRBuilder<> builder(insertBefore);

  // Now that we have full information about ranges, loop over the ranges and
  // emit memcpy's for anything big enough to be worthwhile.
  for (MemOpRanges::const_iterator I = Ranges.begin(), E = Ranges.end();
       I != E; ++I) {
    const MemOpRange &Range = *I;
    Value* oldBaseI = NULL;
    Value* newBaseI = NULL;

    if (Range.TheStores.size() == 1) continue; // Don't bother if there's only one thing...

    builder.SetInsertPoint(insertBefore);

    // Otherwise, we do want to transform this!  Create a new memcpy.
    // Get the starting pointer of the block.
    StartPtr = Range.StartPtr;

//.........这里部分代码省略.........

/// Attempt to merge an objc_release with a store, load, and objc_retain to form
/// an objc_storeStrong. This can be a little tricky because the instructions
/// don't always appear in order, and there may be unrelated intervening
/// instructions.
void ObjCARCContract::ContractRelease(Instruction *Release,
                                      inst_iterator &Iter) {
  LoadInst *Load = dyn_cast<LoadInst>(GetObjCArg(Release));
  if (!Load || !Load->isSimple()) return;

  // For now, require everything to be in one basic block.
  BasicBlock *BB = Release->getParent();
  if (Load->getParent() != BB) return;

  // Walk down to find the store and the release, which may be in either order.
  BasicBlock::iterator I = Load, End = BB->end();
  ++I;
  AliasAnalysis::Location Loc = AA->getLocation(Load);
  StoreInst *Store = 0;
  bool SawRelease = false;
  for (; !Store || !SawRelease; ++I) {
    if (I == End)
      return;

    Instruction *Inst = I;
    if (Inst == Release) {
      SawRelease = true;
      continue;
    }

    InstructionClass Class = GetBasicInstructionClass(Inst);

    // Unrelated retains are harmless.
    if (IsRetain(Class))
      continue;

    if (Store) {
      // The store is the point where we're going to put the objc_storeStrong,
      // so make sure there are no uses after it.
      if (CanUse(Inst, Load, PA, Class))
        return;
    } else if (AA->getModRefInfo(Inst, Loc) & AliasAnalysis::Mod) {
      // We are moving the load down to the store, so check for anything
      // else which writes to the memory between the load and the store.
      Store = dyn_cast<StoreInst>(Inst);
      if (!Store || !Store->isSimple()) return;
      if (Store->getPointerOperand() != Loc.Ptr) return;
    }
  }

  Value *New = StripPointerCastsAndObjCCalls(Store->getValueOperand());

  // Walk up to find the retain.
  I = Store;
  BasicBlock::iterator Begin = BB->begin();
  while (I != Begin && GetBasicInstructionClass(I) != IC_Retain)
    --I;
  Instruction *Retain = I;
  if (GetBasicInstructionClass(Retain) != IC_Retain) return;
  if (GetObjCArg(Retain) != New) return;

  Changed = true;
  ++NumStoreStrongs;

  LLVMContext &C = Release->getContext();
  Type *I8X = PointerType::getUnqual(Type::getInt8Ty(C));
  Type *I8XX = PointerType::getUnqual(I8X);

  Value *Args[] = { Load->getPointerOperand(), New };
  if (Args[0]->getType() != I8XX)
    Args[0] = new BitCastInst(Args[0], I8XX, "", Store);
  if (Args[1]->getType() != I8X)
    Args[1] = new BitCastInst(Args[1], I8X, "", Store);
  CallInst *StoreStrong =
    CallInst::Create(getStoreStrongCallee(BB->getParent()->getParent()),
                     Args, "", Store);
  StoreStrong->setDoesNotThrow();
  StoreStrong->setDebugLoc(Store->getDebugLoc());

  // We can't set the tail flag yet, because we haven't yet determined
  // whether there are any escaping allocas. Remember this call, so that
  // we can set the tail flag once we know it's safe.
  StoreStrongCalls.insert(StoreStrong);

  if (&*Iter == Store) ++Iter;
  Store->eraseFromParent();
  Release->eraseFromParent();
  EraseInstruction(Retain);
  if (Load->use_empty())
    Load->eraseFromParent();
}

    bool runOnFunction(Function &F) override {
    	AliasAnalysis AA = getAnalysis<AliasAnalysis>();
        DependenceAnalysis *DA = &(getAnalysis<DependenceAnalysis>());
        // iterate over basic blocks
        Function *func = &F;
        unsigned bb_num = 0;
        for (Function::iterator BB = func->begin(), BE = func->end();
       BB != BE; ++BB) {
        	errs() << "BB-" << bb_num << "\n";
            bb_num++;
            // iterator over instructions
            unsigned inst_num = 0;
            for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E;++I) {
                Instruction *Ins = dyn_cast<Instruction>(I);
                if (!Ins)
                    return false;
                LoadInst *Ld = dyn_cast<LoadInst>(I);
                StoreInst *St = dyn_cast<StoreInst>(I);
                if (!St && !Ld)
                    continue;
                if (Ld && !Ld->isSimple())
                    return false;
                if (St && !St->isSimple())
                    return false;
                inst_num++;
                MemInstr.push_back(&*I);
                errs() << "MemInst-" << inst_num << ":" << *I << "\n";
            }

        	ValueVector::iterator I, IE, J, JE;
            for (I = MemInstr.begin(), IE = MemInstr.end(); I != IE; ++I) {
            for (J = I, JE = MemInstr.end(); J != JE; ++J) {
                std::vector<char> Dep;
                Instruction *Src = dyn_cast<Instruction>(*I);
                Instruction *Des = dyn_cast<Instruction>(*J);
                if (Src == Des)
                    continue;
                if (isa<LoadInst>(Src) && isa<LoadInst>(Des))
                    continue;
                if (auto D = DA->depends(Src, Des, true)) {
                    errs() << "Found Dependency between:\nSrc:" << *Src << "\nDes:" << *Des
                     << "\n";
                	if (D->isFlow()) {
                    	errs () << "Flow dependence not handled";
                    	return false;
                	}
                
                	if (D->isAnti()) {
                    	errs() << "Found Anti dependence \n";

						AliasAnalysis::AliasResult AA_dep = AA.alias(Src, Des);
                        AliasAnalysis::AliasResult AA_dep_1 = AA.alias(Des, Src);
                    	errs() << "The Ld->St alias result is " << AA_dep << "\n";
                    	errs() << "The St->Ld alias result is " << AA_dep_1 << "\n";
                    	
                        unsigned Levels = D->getLevels();
                    	errs() << "levels = " << Levels << "\n";
                    	char Direction;
                    	for (unsigned II = 1; II <= Levels; ++II) {
                        	const SCEV *Distance = D->getDistance(II);
                        	const SCEVConstant *SCEVConst = dyn_cast_or_null<SCEVConstant>(Distance);
                        	if (SCEVConst) {
                            	const ConstantInt *CI = SCEVConst->getValue();
                                //int64_t it_dist = CI->getUniqueInteger().getSExtValue();
                                //int it_dist = CI->getUniqueInteger().getSExtValue();
                               	unsigned it_dist = abs(CI->getUniqueInteger().getSExtValue());
                            	errs() << "distance is not null\n";
                            	//errs() << "distance = "<< *CI << "\n";
                            	errs() << "distance = "<< it_dist << "\n";
                       			if (CI->isNegative())
                            		Direction = '<';
                        		else if (CI->isZero())
                            		Direction = '=';
                        		else
                            		Direction = '>';
                        		Dep.push_back(Direction);
                        	} 
                        	else if (D->isScalar(II)) {
                        		Direction = 'S';
                        		Dep.push_back(Direction);
                        	} 
                        	else {
                            	unsigned Dir = D->getDirection(II);
                            	if (Dir == Dependence::DVEntry::LT || Dir == Dependence::DVEntry::LE)
                                	Direction = '<';
                            	else if (Dir == Dependence::DVEntry::GT || Dir == Dependence::DVEntry::GE)
                                	Direction = '>';
                            	else if (Dir == Dependence::DVEntry::EQ)
                                	Direction = '=';
                            	else
                                	Direction = '*';
                            	Dep.push_back(Direction);
                        	}
                    	}
                	}
              	}
            }
        	}
        }
        errs() << "------Hello World!--------\n";
//.........这里部分代码省略.........