text: //===- Attributor.cpp - Module-wide attribute deduction -------------------===//
  //
  // 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 implements an interprocedural pass that deduces and/or propagates
  // attributes. This is done in an abstract interpretation style fixpoint
  // iteration. See the Attributor.h file comment and the class descriptions in
  // that file for more information.
  //
  //===----------------------------------------------------------------------===//
  
  #include "llvm/Transforms/IPO/Attributor.h"
  
  #include "llvm/ADT/GraphTraits.h"
  #include "llvm/ADT/PointerIntPair.h"
  #include "llvm/ADT/Statistic.h"
  #include "llvm/ADT/TinyPtrVector.h"
  #include "llvm/Analysis/InlineCost.h"
  #include "llvm/Analysis/LazyValueInfo.h"
  #include "llvm/Analysis/MemorySSAUpdater.h"
  #include "llvm/Analysis/MustExecute.h"
  #include "llvm/Analysis/ValueTracking.h"
  #include "llvm/IR/Attributes.h"
  #include "llvm/IR/GlobalValue.h"
  #include "llvm/IR/IRBuilder.h"
  #include "llvm/IR/NoFolder.h"
  #include "llvm/IR/Verifier.h"
  #include "llvm/InitializePasses.h"
  #include "llvm/Support/Casting.h"
  #include "llvm/Support/CommandLine.h"
  #include "llvm/Support/Debug.h"
  #include "llvm/Support/DebugCounter.h"
  #include "llvm/Support/FileSystem.h"
  #include "llvm/Support/GraphWriter.h"
  #include "llvm/Support/raw_ostream.h"
  #include "llvm/Transforms/Utils/BasicBlockUtils.h"
  #include "llvm/Transforms/Utils/Cloning.h"
  #include "llvm/Transforms/Utils/Local.h"
  
  #include <cassert>
  #include <string>
  
  using namespace llvm;
  
  #define DEBUG_TYPE "attributor"
  
  DEBUG_COUNTER(ManifestDBGCounter, "attributor-manifest",
                "Determine what attributes are manifested in the IR");
  
  STATISTIC(NumFnDeleted, "Number of function deleted");
  STATISTIC(NumFnWithExactDefinition,
            "Number of functions with exact definitions");
  STATISTIC(NumFnWithoutExactDefinition,
            "Number of functions without exact definitions");
  STATISTIC(NumFnShallowWrappersCreated, "Number of shallow wrappers created");
  STATISTIC(NumAttributesTimedOut,
            "Number of abstract attributes timed out before fixpoint");
  STATISTIC(NumAttributesValidFixpoint,
            "Number of abstract attributes in a valid fixpoint state");
  STATISTIC(NumAttributesManifested,
            "Number of abstract attributes manifested in IR");
  STATISTIC(NumAttributesFixedDueToRequiredDependences,
            "Number of abstract attributes fixed due to required dependences");
  
  // TODO: Determine a good default value.
  //
  // In the LLVM-TS and SPEC2006, 32 seems to not induce compile time overheads
  // (when run with the first 5 abstract attributes). The results also indicate
  // that we never reach 32 iterations but always find a fixpoint sooner.
  //
  // This will become more evolved once we perform two interleaved fixpoint
  // iterations: bottom-up and top-down.
  static cl::opt<unsigned>
      MaxFixpointIterations("attributor-max-iterations", cl::Hidden,
                            cl::desc("Maximal number of fixpoint iterations."),
                            cl::init(32));
  
  static cl::opt<unsigned, true> MaxInitializationChainLengthX(
      "attributor-max-initialization-chain-length", cl::Hidden,
      cl::desc(
          "Maximal number of chained initializations (to avoid stack overflows)"),
      cl::location(MaxInitializationChainLength), cl::init(1024));
  unsigned llvm::MaxInitializationChainLength;
  
  static cl::opt<bool> VerifyMaxFixpointIterations(
      "attributor-max-iterations-verify", cl::Hidden,
      cl::desc("Verify that max-iterations is a tight bound for a fixpoint"),
      cl::init(false));
  
  static cl::opt<bool> AnnotateDeclarationCallSites(
      "attributor-annotate-decl-cs", cl::Hidden,
      cl::desc("Annotate call sites of function declarations."), cl::init(false));
  
  static cl::opt<bool> EnableHeapToStack("enable-heap-to-stack-conversion",
                                         cl::init(true), cl::Hidden);
  
  static cl::opt<bool>
      AllowShallowWrappers("attributor-allow-shallow-wrappers", cl::Hidden,
                           cl::desc("Allow the Attributor to create shallow "
                                    "wrappers for non-exact definitions."),
                           cl::init(false));
  
  static cl::opt<bool>
      AllowDeepWrapper("attributor-allow-deep-wrappers", cl::Hidden,
                       cl::desc("Allow the Attributor to use IP information "
                                "derived from non-exact functions via cloning"),
                       cl::init(false));
  
  // These options can only used for debug builds.
  #ifndef NDEBUG
  static cl::list<std::string>
      SeedAllowList("attributor-seed-allow-list", cl::Hidden,
                    cl::desc("Comma seperated list of attribute names that are "
                             "allowed to be seeded."),
                    cl::ZeroOrMore, cl::CommaSeparated);
  
  static cl::list<std::string> FunctionSeedAllowList(
      "attributor-function-seed-allow-list", cl::Hidden,
      cl::desc("Comma seperated list of function names that are "
               "allowed to be seeded."),
      cl::ZeroOrMore, cl::CommaSeparated);
  #endif
  
  static cl::opt<bool>
      DumpDepGraph("attributor-dump-dep-graph", cl::Hidden,
                   cl::desc("Dump the dependency graph to dot files."),
                   cl::init(false));
  
  static cl::opt<std::string> DepGraphDotFileNamePrefix(
      "attributor-depgraph-dot-filename-prefix", cl::Hidden,
      cl::desc("The prefix used for the CallGraph dot file names."));
  
  static cl::opt<bool> ViewDepGraph("attributor-view-dep-graph", cl::Hidden,
                                    cl::desc("View the dependency graph."),
                                    cl::init(false));
  
  static cl::opt<bool> PrintDependencies("attributor-print-dep", cl::Hidden,
                                         cl::desc("Print attribute dependencies"),
                                         cl::init(false));
  
  /// Logic operators for the change status enum class.
  ///
  ///{
  ChangeStatus llvm::operator|(ChangeStatus L, ChangeStatus R) {
    return L == ChangeStatus::CHANGED ? L : R;
  }
  ChangeStatus llvm::operator&(ChangeStatus L, ChangeStatus R) {
    return L == ChangeStatus::UNCHANGED ? L : R;
  }
  ///}
  
  /// Return true if \p New is equal or worse than \p Old.
  static bool isEqualOrWorse(const Attribute &New, const Attribute &Old) {
    if (!Old.isIntAttribute())
      return true;
  
    return Old.getValueAsInt() >= New.getValueAsInt();
  }
  
  /// Return true if the information provided by \p Attr was added to the
  /// attribute list \p Attrs. This is only the case if it was not already present
  /// in \p Attrs at the position describe by \p PK and \p AttrIdx.
  static bool addIfNotExistent(LLVMContext &Ctx, const Attribute &Attr,
                               AttributeList &Attrs, int AttrIdx) {
  
    if (Attr.isEnumAttribute()) {
      Attribute::AttrKind Kind = Attr.getKindAsEnum();
      if (Attrs.hasAttribute(AttrIdx, Kind))
        if (isEqualOrWorse(Attr, Attrs.getAttribute(AttrIdx, Kind)))
          return false;
      Attrs = Attrs.addAttribute(Ctx, AttrIdx, Attr);
      return true;
    }
    if (Attr.isStringAttribute()) {
      StringRef Kind = Attr.getKindAsString();
      if (Attrs.hasAttribute(AttrIdx, Kind))
        if (isEqualOrWorse(Attr, Attrs.getAttribute(AttrIdx, Kind)))
          return false;
      Attrs = Attrs.addAttribute(Ctx, AttrIdx, Attr);
      return true;
    }
    if (Attr.isIntAttribute()) {
      Attribute::AttrKind Kind = Attr.getKindAsEnum();
      if (Attrs.hasAttribute(AttrIdx, Kind))
        if (isEqualOrWorse(Attr, Attrs.getAttribute(AttrIdx, Kind)))
          return false;
      Attrs = Attrs.removeAttribute(Ctx, AttrIdx, Kind);
      Attrs = Attrs.addAttribute(Ctx, AttrIdx, Attr);
      return true;
    }
  
    llvm_unreachable("Expected enum or string attribute!");
  }
  
  Argument *IRPosition::getAssociatedArgument() const {
    if (getPositionKind() == IRP_ARGUMENT)
      return cast<Argument>(&getAnchorValue());
  
    // Not an Argument and no argument number means this is not a call site
    // argument, thus we cannot find a callback argument to return.
    int ArgNo = getCallSiteArgNo();
    if (ArgNo < 0)
      return nullptr;
  
    // Use abstract call sites to make the connection between the call site
    // values and the ones in callbacks. If a callback was found that makes use
    // of the underlying call site operand, we want the corresponding callback
    // callee argument and not the direct callee argument.
    Optional<Argument *> CBCandidateArg;
    SmallVector<const Use *, 4> CallbackUses;
    const auto &CB = cast<CallBase>(getAnchorValue());
    AbstractCallSite::getCallbackUses(CB, CallbackUses);
    for (const Use *U : CallbackUses) {
      AbstractCallSite ACS(U);
      assert(ACS && ACS.isCallbackCall());
      if (!ACS.getCalledFunction())
        continue;
  
      for (unsigned u = 0, e = ACS.getNumArgOperands(); u < e; u++) {
  
        // Test if the underlying call site operand is argument number u of the
        // callback callee.
        if (ACS.getCallArgOperandNo(u) != ArgNo)
          continue;
  
        assert(ACS.getCalledFunction()->arg_size() > u &&
               "ACS mapped into var-args arguments!");
        if (CBCandidateArg.hasValue()) {
          CBCandidateArg = nullptr;
          break;
        }
        CBCandidateArg = ACS.getCalledFunction()->getArg(u);
      }
    }
  
    // If we found a unique callback candidate argument, return it.
    if (CBCandidateArg.hasValue() && CBCandidateArg.getValue())
      return CBCandidateArg.getValue();
  
    // If no callbacks were found, or none used the underlying call site operand
    // exclusively, use the direct callee argument if available.
    const Function *Callee = CB.getCalledFunction();
    if (Callee && Callee->arg_size() > unsigned(ArgNo))
      return Callee->getArg(ArgNo);
  
    return nullptr;
  }
  
  ChangeStatus AbstractAttribute::update(Attributor &A) {
    ChangeStatus HasChanged = ChangeStatus::UNCHANGED;
    if (getState().isAtFixpoint())
      return HasChanged;
  
    LLVM_DEBUG(dbgs() << "[Attributor] Update: " << *this << "\n");
  
    HasChanged = updateImpl(A);
  
    LLVM_DEBUG(dbgs() << "[Attributor] Update " << HasChanged << " " << *this
                      << "\n");
  
    return HasChanged;
  }
  
  ChangeStatus
  IRAttributeManifest::manifestAttrs(Attributor &A, const IRPosition &IRP,
                                     const ArrayRef<Attribute> &DeducedAttrs) {
    Function *ScopeFn = IRP.getAnchorScope();
    IRPosition::Kind PK = IRP.getPositionKind();
  
    // In the following some generic code that will manifest attributes in
    // DeducedAttrs if they improve the current IR. Due to the different
    // annotation positions we use the underlying AttributeList interface.
  
    AttributeList Attrs;
    switch (PK) {
    case IRPosition::IRP_INVALID:
    case IRPosition::IRP_FLOAT:
      return ChangeStatus::UNCHANGED;
    case IRPosition::IRP_ARGUMENT:
    case IRPosition::IRP_FUNCTION:
    case IRPosition::IRP_RETURNED:
      Attrs = ScopeFn->getAttributes();
      break;
    case IRPosition::IRP_CALL_SITE:
    case IRPosition::IRP_CALL_SITE_RETURNED:
    case IRPosition::IRP_CALL_SITE_ARGUMENT:
      Attrs = cast<CallBase>(IRP.getAnchorValue()).getAttributes();
      break;
    }
  
    ChangeStatus HasChanged = ChangeStatus::UNCHANGED;
    LLVMContext &Ctx = IRP.getAnchorValue().getContext();
    for (const Attribute &Attr : DeducedAttrs) {
      if (!addIfNotExistent(Ctx, Attr, Attrs, IRP.getAttrIdx()))
        continue;
  
      HasChanged = ChangeStatus::CHANGED;
    }
  
    if (HasChanged == ChangeStatus::UNCHANGED)
      return HasChanged;
  
    switch (PK) {
    case IRPosition::IRP_ARGUMENT:
    case IRPosition::IRP_FUNCTION:
    case IRPosition::IRP_RETURNED:
      ScopeFn->setAttributes(Attrs);
      break;
    case IRPosition::IRP_CALL_SITE:
    case IRPosition::IRP_CALL_SITE_RETURNED:
    case IRPosition::IRP_CALL_SITE_ARGUMENT:
      cast<CallBase>(IRP.getAnchorValue()).setAttributes(Attrs);
      break;
    case IRPosition::IRP_INVALID:
    case IRPosition::IRP_FLOAT:
      break;
    }
  
    return HasChanged;
  }
  
  const IRPosition IRPosition::EmptyKey(DenseMapInfo<void *>::getEmptyKey());
  const IRPosition
      IRPosition::TombstoneKey(DenseMapInfo<void *>::getTombstoneKey());
  
  SubsumingPositionIterator::SubsumingPositionIterator(const IRPosition &IRP) {
    IRPositions.emplace_back(IRP);
  
    // Helper to determine if operand bundles on a call site are benin or
    // potentially problematic. We handle only llvm.assume for now.
    auto CanIgnoreOperandBundles = [](const CallBase &CB) {
      return (isa<IntrinsicInst>(CB) &&
              cast<IntrinsicInst>(CB).getIntrinsicID() == Intrinsic ::assume);
    };
  
    const auto *CB = dyn_cast<CallBase>(&IRP.getAnchorValue());
    switch (IRP.getPositionKind()) {
    case IRPosition::IRP_INVALID:
    case IRPosition::IRP_FLOAT:
    case IRPosition::IRP_FUNCTION:
      return;
    case IRPosition::IRP_ARGUMENT:
    case IRPosition::IRP_RETURNED:
      IRPositions.emplace_back(IRPosition::function(*IRP.getAnchorScope()));
      return;
    case IRPosition::IRP_CALL_SITE:
      assert(CB && "Expected call site!");
      // TODO: We need to look at the operand bundles similar to the redirection
      //       in CallBase.
      if (!CB->hasOperandBundles() || CanIgnoreOperandBundles(*CB))
        if (const Function *Callee = CB->getCalledFunction())
          IRPositions.emplace_back(IRPosition::function(*Callee));
      return;
    case IRPosition::IRP_CALL_SITE_RETURNED:
      assert(CB && "Expected call site!");
      // TODO: We need to look at the operand bundles similar to the redirection
      //       in CallBase.
      if (!CB->hasOperandBundles() || CanIgnoreOperandBundles(*CB)) {
        if (const Function *Callee = CB->getCalledFunction()) {
          IRPositions.emplace_back(IRPosition::returned(*Callee));
          IRPositions.emplace_back(IRPosition::function(*Callee));
          for (const Argument &Arg : Callee->args())
            if (Arg.hasReturnedAttr()) {
              IRPositions.emplace_back(
                  IRPosition::callsite_argument(*CB, Arg.getArgNo()));
              IRPositions.emplace_back(
                  IRPosition::value(*CB->getArgOperand(Arg.getArgNo())));
              IRPositions.emplace_back(IRPosition::argument(Arg));
            }
        }
      }
      IRPositions.emplace_back(IRPosition::callsite_function(*CB));
      return;
    case IRPosition::IRP_CALL_SITE_ARGUMENT: {
      assert(CB && "Expected call site!");
      // TODO: We need to look at the operand bundles similar to the redirection
      //       in CallBase.
      if (!CB->hasOperandBundles() || CanIgnoreOperandBundles(*CB)) {
        const Function *Callee = CB->getCalledFunction();
        if (Callee) {
          if (Argument *Arg = IRP.getAssociatedArgument())
            IRPositions.emplace_back(IRPosition::argument(*Arg));
          IRPositions.emplace_back(IRPosition::function(*Callee));
        }
      }
      IRPositions.emplace_back(IRPosition::value(IRP.getAssociatedValue()));
      return;
    }
    }
  }
  
  bool IRPosition::hasAttr(ArrayRef<Attribute::AttrKind> AKs,
                           bool IgnoreSubsumingPositions, Attributor *A) const {
    SmallVector<Attribute, 4> Attrs;
    for (const IRPosition &EquivIRP : SubsumingPositionIterator(*this)) {
      for (Attribute::AttrKind AK : AKs)
        if (EquivIRP.getAttrsFromIRAttr(AK, Attrs))
          return true;
      // The first position returned by the SubsumingPositionIterator is
      // always the position itself. If we ignore subsuming positions we
      // are done after the first iteration.
      if (IgnoreSubsumingPositions)
        break;
    }
    if (A)
      for (Attribute::AttrKind AK : AKs)
        if (getAttrsFromAssumes(AK, Attrs, *A))
          return true;
    return false;
  }
  
  void IRPosition::getAttrs(ArrayRef<Attribute::AttrKind> AKs,
                            SmallVectorImpl<Attribute> &Attrs,
                            bool IgnoreSubsumingPositions, Attributor *A) const {
    for (const IRPosition &EquivIRP : SubsumingPositionIterator(*this)) {
      for (Attribute::AttrKind AK : AKs)
        EquivIRP.getAttrsFromIRAttr(AK, Attrs);
      // The first position returned by the SubsumingPositionIterator is
      // always the position itself. If we ignore subsuming positions we
      // are done after the first iteration.
      if (IgnoreSubsumingPositions)
        break;
    }
    if (A)
      for (Attribute::AttrKind AK : AKs)
        getAttrsFromAssumes(AK, Attrs, *A);
  }
  
  bool IRPosition::getAttrsFromIRAttr(Attribute::AttrKind AK,
                                      SmallVectorImpl<Attribute> &Attrs) const {
    if (getPositionKind() == IRP_INVALID || getPositionKind() == IRP_FLOAT)
      return false;
  
    AttributeList AttrList;
    if (const auto *CB = dyn_cast<CallBase>(&getAnchorValue()))
      AttrList = CB->getAttributes();
    else
      AttrList = getAssociatedFunction()->getAttributes();
  
    bool HasAttr = AttrList.hasAttribute(getAttrIdx(), AK);
    if (HasAttr)
      Attrs.push_back(AttrList.getAttribute(getAttrIdx(), AK));
    return HasAttr;
  }
  
  bool IRPosition::getAttrsFromAssumes(Attribute::AttrKind AK,
                                       SmallVectorImpl<Attribute> &Attrs,
                                       Attributor &A) const {
    assert(getPositionKind() != IRP_INVALID && "Did expect a valid position!");
    Value &AssociatedValue = getAssociatedValue();
  
    const Assume2KnowledgeMap &A2K =
        A.getInfoCache().getKnowledgeMap().lookup({&AssociatedValue, AK});
  
    // Check if we found any potential assume use, if not we don't need to create
    // explorer iterators.
    if (A2K.empty())
      return false;
  
    LLVMContext &Ctx = AssociatedValue.getContext();
    unsigned AttrsSize = Attrs.size();
    MustBeExecutedContextExplorer &Explorer =
        A.getInfoCache().getMustBeExecutedContextExplorer();
    auto EIt = Explorer.begin(getCtxI()), EEnd = Explorer.end(getCtxI());
    for (auto &It : A2K)
      if (Explorer.findInContextOf(It.first, EIt, EEnd))
        Attrs.push_back(Attribute::get(Ctx, AK, It.second.Max));
    return AttrsSize != Attrs.size();
  }
  
  void IRPosition::verify() {
  #ifdef EXPENSIVE_CHECKS
    switch (getPositionKind()) {
    case IRP_INVALID:
      assert(!Enc.getOpaqueValue() &&
             "Expected a nullptr for an invalid position!");
      return;
    case IRP_FLOAT:
      assert((!isa<CallBase>(&getAssociatedValue()) &&
              !isa<Argument>(&getAssociatedValue())) &&
             "Expected specialized kind for call base and argument values!");
      return;
    case IRP_RETURNED:
      assert(isa<Function>(getAsValuePtr()) &&
             "Expected function for a 'returned' position!");
      assert(getAsValuePtr() == &getAssociatedValue() &&
             "Associated value mismatch!");
      return;
    case IRP_CALL_SITE_RETURNED:
      assert((isa<CallBase>(getAsValuePtr())) &&
             "Expected call base for 'call site returned' position!");
      assert(getAsValuePtr() == &getAssociatedValue() &&
             "Associated value mismatch!");
      return;
    case IRP_CALL_SITE:
      assert((isa<CallBase>(getAsValuePtr())) &&
             "Expected call base for 'call site function' position!");
      assert(getAsValuePtr() == &getAssociatedValue() &&
             "Associated value mismatch!");
      return;
    case IRP_FUNCTION:
      assert(isa<Function>(getAsValuePtr()) &&
             "Expected function for a 'function' position!");
      assert(getAsValuePtr() == &getAssociatedValue() &&
             "Associated value mismatch!");
      return;
    case IRP_ARGUMENT:
      assert(isa<Argument>(getAsValuePtr()) &&
             "Expected argument for a 'argument' position!");
      assert(getAsValuePtr() == &getAssociatedValue() &&
             "Associated value mismatch!");
      return;
    case IRP_CALL_SITE_ARGUMENT: {
      Use *U = getAsUsePtr();
      assert(U && "Expected use for a 'call site argument' position!");
      assert(isa<CallBase>(U->getUser()) &&
             "Expected call base user for a 'call site argument' position!");
      assert(cast<CallBase>(U->getUser())->isArgOperand(U) &&
             "Expected call base argument operand for a 'call site argument' "
             "position");
      assert(cast<CallBase>(U->getUser())->getArgOperandNo(U) ==
                 unsigned(getCallSiteArgNo()) &&
             "Argument number mismatch!");
      assert(U->get() == &getAssociatedValue() && "Associated value mismatch!");
      return;
    }
    }
  #endif
  }
  
  Optional<Constant *>
  Attributor::getAssumedConstant(const Value &V, const AbstractAttribute &AA,
                                 bool &UsedAssumedInformation) {
    const auto &ValueSimplifyAA =
        getAAFor<AAValueSimplify>(AA, IRPosition::value(V), DepClassTy::NONE);
    Optional<Value *> SimplifiedV =
        ValueSimplifyAA.getAssumedSimplifiedValue(*this);
    bool IsKnown = ValueSimplifyAA.isKnown();
    UsedAssumedInformation |= !IsKnown;
    if (!SimplifiedV.hasValue()) {
      recordDependence(ValueSimplifyAA, AA, DepClassTy::OPTIONAL);
      return llvm::None;
    }
    if (isa_and_nonnull<UndefValue>(SimplifiedV.getValue())) {
      recordDependence(ValueSimplifyAA, AA, DepClassTy::OPTIONAL);
      return llvm::None;
    }
    Constant *CI = dyn_cast_or_null<Constant>(SimplifiedV.getValue());
    if (CI && CI->getType() != V.getType()) {
      // TODO: Check for a save conversion.
      return nullptr;
    }
    if (CI)
      recordDependence(ValueSimplifyAA, AA, DepClassTy::OPTIONAL);
    return CI;
  }
  
  Attributor::~Attributor() {
    // The abstract attributes are allocated via the BumpPtrAllocator Allocator,
    // thus we cannot delete them. We can, and want to, destruct them though.
    for (auto &DepAA : DG.SyntheticRoot.Deps) {
      AbstractAttribute *AA = cast<AbstractAttribute>(DepAA.getPointer());
      AA->~AbstractAttribute();
    }
  }
  
  bool Attributor::isAssumedDead(const AbstractAttribute &AA,
                                 const AAIsDead *FnLivenessAA,
                                 bool CheckBBLivenessOnly, DepClassTy DepClass) {
    const IRPosition &IRP = AA.getIRPosition();
    if (!Functions.count(IRP.getAnchorScope()))
      return false;
    return isAssumedDead(IRP, &AA, FnLivenessAA, CheckBBLivenessOnly, DepClass);
  }
  
  bool Attributor::isAssumedDead(const Use &U,
                                 const AbstractAttribute *QueryingAA,
                                 const AAIsDead *FnLivenessAA,
                                 bool CheckBBLivenessOnly, DepClassTy DepClass) {
    Instruction *UserI = dyn_cast<Instruction>(U.getUser());
    if (!UserI)
      return isAssumedDead(IRPosition::value(*U.get()), QueryingAA, FnLivenessAA,
                           CheckBBLivenessOnly, DepClass);
  
    if (auto *CB = dyn_cast<CallBase>(UserI)) {
      // For call site argument uses we can check if the argument is
      // unused/dead.
      if (CB->isArgOperand(&U)) {
        const IRPosition &CSArgPos =
            IRPosition::callsite_argument(*CB, CB->getArgOperandNo(&U));
        return isAssumedDead(CSArgPos, QueryingAA, FnLivenessAA,
                             CheckBBLivenessOnly, DepClass);
      }
    } else if (ReturnInst *RI = dyn_cast<ReturnInst>(UserI)) {
      const IRPosition &RetPos = IRPosition::returned(*RI->getFunction());
      return isAssumedDead(RetPos, QueryingAA, FnLivenessAA, CheckBBLivenessOnly,
                           DepClass);
    } else if (PHINode *PHI = dyn_cast<PHINode>(UserI)) {
      BasicBlock *IncomingBB = PHI->getIncomingBlock(U);
      return isAssumedDead(*IncomingBB->getTerminator(), QueryingAA, FnLivenessAA,
                           CheckBBLivenessOnly, DepClass);
    }
  
    return isAssumedDead(IRPosition::value(*UserI), QueryingAA, FnLivenessAA,
                         CheckBBLivenessOnly, DepClass);
  }
  
  bool Attributor::isAssumedDead(const Instruction &I,
                                 const AbstractAttribute *QueryingAA,
                                 const AAIsDead *FnLivenessAA,
                                 bool CheckBBLivenessOnly, DepClassTy DepClass) {
    if (!FnLivenessAA)
      FnLivenessAA = lookupAAFor<AAIsDead>(IRPosition::function(*I.getFunction()),
                                           QueryingAA, DepClassTy::NONE);
  
    // If we have a context instruction and a liveness AA we use it.
    if (FnLivenessAA &&
        FnLivenessAA->getIRPosition().getAnchorScope() == I.getFunction() &&
        FnLivenessAA->isAssumedDead(&I)) {
      if (QueryingAA)
        recordDependence(*FnLivenessAA, *QueryingAA, DepClass);
      return true;
    }
  
    if (CheckBBLivenessOnly)
      return false;
  
    const AAIsDead &IsDeadAA = getOrCreateAAFor<AAIsDead>(
        IRPosition::value(I), QueryingAA, DepClassTy::NONE);
    // Don't check liveness for AAIsDead.
    if (QueryingAA == &IsDeadAA)
      return false;
  
    if (IsDeadAA.isAssumedDead()) {
      if (QueryingAA)
        recordDependence(IsDeadAA, *QueryingAA, DepClass);
      return true;
    }
  
    return false;
  }
  
  bool Attributor::isAssumedDead(const IRPosition &IRP,
                                 const AbstractAttribute *QueryingAA,
                                 const AAIsDead *FnLivenessAA,
                                 bool CheckBBLivenessOnly, DepClassTy DepClass) {
    Instruction *CtxI = IRP.getCtxI();
    if (CtxI &&
        isAssumedDead(*CtxI, QueryingAA, FnLivenessAA,
                      /* CheckBBLivenessOnly */ true,
                      CheckBBLivenessOnly ? DepClass : DepClassTy::OPTIONAL))
      return true;
  
    if (CheckBBLivenessOnly)
      return false;
  
    // If we haven't succeeded we query the specific liveness info for the IRP.
    const AAIsDead *IsDeadAA;
    if (IRP.getPositionKind() == IRPosition::IRP_CALL_SITE)
      IsDeadAA = &getOrCreateAAFor<AAIsDead>(
          IRPosition::callsite_returned(cast<CallBase>(IRP.getAssociatedValue())),
          QueryingAA, DepClassTy::NONE);
    else
      IsDeadAA = &getOrCreateAAFor<AAIsDead>(IRP, QueryingAA, DepClassTy::NONE);
    // Don't check liveness for AAIsDead.
    if (QueryingAA == IsDeadAA)
      return false;
  
    if (IsDeadAA->isAssumedDead()) {
      if (QueryingAA)
        recordDependence(*IsDeadAA, *QueryingAA, DepClass);
      return true;
    }
  
    return false;
  }
  
  bool Attributor::checkForAllUses(function_ref<bool(const Use &, bool &)> Pred,
                                   const AbstractAttribute &QueryingAA,
                                   const Value &V, DepClassTy LivenessDepClass) {
  
    // Check the trivial case first as it catches void values.
    if (V.use_empty())
      return true;
  
    // If the value is replaced by another one, for now a constant, we do not have
    // uses. Note that this requires users of `checkForAllUses` to not recurse but
    // instead use the `follow` callback argument to look at transitive users,
    // however, that should be clear from the presence of the argument.
    bool UsedAssumedInformation = false;
    Optional<Constant *> C =
        getAssumedConstant(V, QueryingAA, UsedAssumedInformation);
    if (C.hasValue() && C.getValue()) {
      LLVM_DEBUG(dbgs() << "[Attributor] Value is simplified, uses skipped: " << V
                        << " -> " << *C.getValue() << "\n");
      return true;
    }
  
    const IRPosition &IRP = QueryingAA.getIRPosition();
    SmallVector<const Use *, 16> Worklist;
    SmallPtrSet<const Use *, 16> Visited;
  
    for (const Use &U : V.uses())
      Worklist.push_back(&U);
  
    LLVM_DEBUG(dbgs() << "[Attributor] Got " << Worklist.size()
                      << " initial uses to check\n");
  
    const Function *ScopeFn = IRP.getAnchorScope();
    const auto *LivenessAA =
        ScopeFn ? &getAAFor<AAIsDead>(QueryingAA, IRPosition::function(*ScopeFn),
                                      DepClassTy::NONE)
                : nullptr;
  
    while (!Worklist.empty()) {
      const Use *U = Worklist.pop_back_val();
      if (!Visited.insert(U).second)
        continue;
      LLVM_DEBUG(dbgs() << "[Attributor] Check use: " << **U << " in "
                        << *U->getUser() << "\n");
      if (isAssumedDead(*U, &QueryingAA, LivenessAA,
                        /* CheckBBLivenessOnly */ false, LivenessDepClass)) {
        LLVM_DEBUG(dbgs() << "[Attributor] Dead use, skip!\n");
        continue;
      }
      if (U->getUser()->isDroppable()) {
        LLVM_DEBUG(dbgs() << "[Attributor] Droppable user, skip!\n");
        continue;
      }
  
      bool Follow = false;
      if (!Pred(*U, Follow))
        return false;
      if (!Follow)
        continue;
      for (const Use &UU : U->getUser()->uses())
        Worklist.push_back(&UU);
    }
  
    return true;
  }
  
  bool Attributor::checkForAllCallSites(function_ref<bool(AbstractCallSite)> Pred,
                                        const AbstractAttribute &QueryingAA,
                                        bool RequireAllCallSites,
                                        bool &AllCallSitesKnown) {
    // We can try to determine information from
    // the call sites. However, this is only possible all call sites are known,
    // hence the function has internal linkage.
    const IRPosition &IRP = QueryingAA.getIRPosition();
    const Function *AssociatedFunction = IRP.getAssociatedFunction();
    if (!AssociatedFunction) {
      LLVM_DEBUG(dbgs() << "[Attributor] No function associated with " << IRP
                        << "\n");
      AllCallSitesKnown = false;
      return false;
    }
  
    return checkForAllCallSites(Pred, *AssociatedFunction, RequireAllCallSites,
                                &QueryingAA, AllCallSitesKnown);
  }
  
  bool Attributor::checkForAllCallSites(function_ref<bool(AbstractCallSite)> Pred,
                                        const Function &Fn,
                                        bool RequireAllCallSites,
                                        const AbstractAttribute *QueryingAA,
                                        bool &AllCallSitesKnown) {
    if (RequireAllCallSites && !Fn.hasLocalLinkage()) {
      LLVM_DEBUG(
          dbgs()
          << "[Attributor] Function " << Fn.getName()
          << " has no internal linkage, hence not all call sites are known\n");
      AllCallSitesKnown = false;
      return false;
    }
  
    // If we do not require all call sites we might not see all.
    AllCallSitesKnown = RequireAllCallSites;
  
    SmallVector<const Use *, 8> Uses(make_pointer_range(Fn.uses()));
    for (unsigned u = 0; u < Uses.size(); ++u) {
      const Use &U = *Uses[u];
      LLVM_DEBUG(dbgs() << "[Attributor] Check use: " << *U << " in "
                        << *U.getUser() << "\n");
      if (isAssumedDead(U, QueryingAA, nullptr, /* CheckBBLivenessOnly */ true)) {
        LLVM_DEBUG(dbgs() << "[Attributor] Dead use, skip!\n");
        continue;
      }
      if (ConstantExpr *CE = dyn_cast<ConstantExpr>(U.getUser())) {
        if (CE->isCast() && CE->getType()->isPointerTy() &&
            CE->getType()->getPointerElementType()->isFunctionTy()) {
          for (const Use &CEU : CE->uses())
            Uses.push_back(&CEU);
          continue;
        }
      }
  
      AbstractCallSite ACS(&U);
      if (!ACS) {
        LLVM_DEBUG(dbgs() << "[Attributor] Function " << Fn.getName()
                          << " has non call site use " << *U.get() << " in "
                          << *U.getUser() << "\n");
        // BlockAddress users are allowed.
        if (isa<BlockAddress>(U.getUser()))
          continue;
        return false;
      }
  
      const Use *EffectiveUse =
          ACS.isCallbackCall() ? &ACS.getCalleeUseForCallback() : &U;
      if (!ACS.isCallee(EffectiveUse)) {
        if (!RequireAllCallSites)
          continue;
        LLVM_DEBUG(dbgs() << "[Attributor] User " << EffectiveUse->getUser()
                          << " is an invalid use of " << Fn.getName() << "\n");
        return false;
      }
  
      // Make sure the arguments that can be matched between the call site and the
      // callee argee on their type. It is unlikely they do not and it doesn't
      // make sense for all attributes to know/care about this.
      assert(&Fn == ACS.getCalledFunction() && "Expected known callee");
      unsigned MinArgsParams =
          std::min(size_t(ACS.getNumArgOperands()), Fn.arg_size());
      for (unsigned u = 0; u < MinArgsParams; ++u) {
        Value *CSArgOp = ACS.getCallArgOperand(u);
        if (CSArgOp && Fn.getArg(u)->getType() != CSArgOp->getType()) {
          LLVM_DEBUG(
              dbgs() << "[Attributor] Call site / callee argument type mismatch ["
                     << u << "@" << Fn.getName() << ": "
                     << *Fn.getArg(u)->getType() << " vs. "
                     << *ACS.getCallArgOperand(u)->getType() << "\n");
          return false;
        }
      }
  
      if (Pred(ACS))
        continue;
  
      LLVM_DEBUG(dbgs() << "[Attributor] Call site callback failed for "
                        << *ACS.getInstruction() << "\n");
      return false;
    }
  
    return true;
  }
  
  bool Attributor::checkForAllReturnedValuesAndReturnInsts(
      function_ref<bool(Value &, const SmallSetVector<ReturnInst *, 4> &)> Pred,
      const AbstractAttribute &QueryingAA) {
  
    const IRPosition &IRP = QueryingAA.getIRPosition();
    // Since we need to provide return instructions we have to have an exact
    // definition.
    const Function *AssociatedFunction = IRP.getAssociatedFunction();
    if (!AssociatedFunction)
      return false;
  
    // If this is a call site query we use the call site specific return values
    // and liveness information.
    // TODO: use the function scope once we have call site AAReturnedValues.
    const IRPosition &QueryIRP = IRPosition::function(*AssociatedFunction);
    const auto &AARetVal =
        getAAFor<AAReturnedValues>(QueryingAA, QueryIRP, DepClassTy::REQUIRED);
    if (!AARetVal.getState().isValidState())
      return false;
  
    return AARetVal.checkForAllReturnedValuesAndReturnInsts(Pred);
  }
  
  bool Attributor::checkForAllReturnedValues(
      function_ref<bool(Value &)> Pred, const AbstractAttribute &QueryingAA) {
  
    const IRPosition &IRP = QueryingAA.getIRPosition();
    const Function *AssociatedFunction = IRP.getAssociatedFunction();
    if (!AssociatedFunction)
      return false;
  
    // TODO: use the function scope once we have call site AAReturnedValues.
    const IRPosition &QueryIRP = IRPosition::function(*AssociatedFunction);
    const auto &AARetVal =
        getAAFor<AAReturnedValues>(QueryingAA, QueryIRP, DepClassTy::REQUIRED);
    if (!AARetVal.getState().isValidState())
      return false;
  
    return AARetVal.checkForAllReturnedValuesAndReturnInsts(
        [&](Value &RV, const SmallSetVector<ReturnInst *, 4> &) {
          return Pred(RV);
        });
  }
  
  static bool checkForAllInstructionsImpl(
      Attributor *A, InformationCache::OpcodeInstMapTy &OpcodeInstMap,
      function_ref<bool(Instruction &)> Pred, const AbstractAttribute *QueryingAA,
      const AAIsDead *LivenessAA, const ArrayRef<unsigned> &Opcodes,
      bool CheckBBLivenessOnly = false) {
    for (unsigned Opcode : Opcodes) {
      // Check if we have instructions with this opcode at all first.
      auto *Insts = OpcodeInstMap.lookup(Opcode);
      if (!Insts)
        continue;
  
      for (Instruction *I : *Insts) {
        // Skip dead instructions.
        if (A && A->isAssumedDead(IRPosition::value(*I), QueryingAA, LivenessAA,
                                  CheckBBLivenessOnly))
          continue;
  
        if (!Pred(*I))
          return false;
      }
    }
    return true;
  }
  
  bool Attributor::checkForAllInstructions(function_ref<bool(Instruction &)> Pred,
                                           const AbstractAttribute &QueryingAA,
                                           const ArrayRef<unsigned> &Opcodes,
                                           bool CheckBBLivenessOnly) {
  
    const IRPosition &IRP = QueryingAA.getIRPosition();
    // Since we need to provide instructions we have to have an exact definition.
    const Function *AssociatedFunction = IRP.getAssociatedFunction();
    if (!AssociatedFunction)
      return false;
  
    // TODO: use the function scope once we have call site AAReturnedValues.
    const IRPosition &QueryIRP = IRPosition::function(*AssociatedFunction);
    const auto *LivenessAA =
        CheckBBLivenessOnly
            ? nullptr
            : &(getAAFor<AAIsDead>(QueryingAA, QueryIRP, DepClassTy::NONE));
  
    auto &OpcodeInstMap =
        InfoCache.getOpcodeInstMapForFunction(*AssociatedFunction);
    if (!checkForAllInstructionsImpl(this, OpcodeInstMap, Pred, &QueryingAA,
                                     LivenessAA, Opcodes, CheckBBLivenessOnly))
      return false;
  
    return true;
  }
  
  bool Attributor::checkForAllReadWriteInstructions(
      function_ref<bool(Instruction &)> Pred, AbstractAttribute &QueryingAA) {
  
    const Function *AssociatedFunction =
        QueryingAA.getIRPosition().getAssociatedFunction();
    if (!AssociatedFunction)
      return false;
  
    // TODO: use the function scope once we have call site AAReturnedValues.
    const IRPosition &QueryIRP = IRPosition::function(*AssociatedFunction);
    const auto &LivenessAA =
        getAAFor<AAIsDead>(QueryingAA, QueryIRP, DepClassTy::NONE);
  
    for (Instruction *I :
         InfoCache.getReadOrWriteInstsForFunction(*AssociatedFunction)) {
      // Skip dead instructions.
      if (isAssumedDead(IRPosition::value(*I), &QueryingAA, &LivenessAA))
        continue;
  
      if (!Pred(*I))
        return false;
    }
  
    return true;
  }
  
  void Attributor::runTillFixpoint() {
    TimeTraceScope TimeScope("Attributor::runTillFixpoint");
    LLVM_DEBUG(dbgs() << "[Attributor] Identified and initialized "
                      << DG.SyntheticRoot.Deps.size()
                      << " abstract attributes.\n");
  
    // Now that all abstract attributes are collected and initialized we start
    // the abstract analysis.
  
    unsigned IterationCounter = 1;
  
    SmallVector<AbstractAttribute *, 32> ChangedAAs;
    SetVector<AbstractAttribute *> Worklist, InvalidAAs;
    Worklist.insert(DG.SyntheticRoot.begin(), DG.SyntheticRoot.end());
  
    do {
      // Remember the size to determine new attributes.
      size_t NumAAs = DG.SyntheticRoot.Deps.size();
      LLVM_DEBUG(dbgs() << "\n\n[Attributor] #Iteration: " << IterationCounter
                        << ", Worklist size: " << Worklist.size() << "\n");
  
      // For invalid AAs we can fix dependent AAs that have a required dependence,
      // thereby folding long dependence chains in a single step without the need
      // to run updates.
      for (unsigned u = 0; u < InvalidAAs.size(); ++u) {
        AbstractAttribute *InvalidAA = InvalidAAs[u];
  
        // Check the dependences to fast track invalidation.
        LLVM_DEBUG(dbgs() << "[Attributor] InvalidAA: " << *InvalidAA << " has "
                          << InvalidAA->Deps.size()
                          << " required & optional dependences\n");
        while (!InvalidAA->Deps.empty()) {
          const auto &Dep = InvalidAA->Deps.back();
          InvalidAA->Deps.pop_back();
          AbstractAttribute *DepAA = cast<AbstractAttribute>(Dep.getPointer());
          if (Dep.getInt() == unsigned(DepClassTy::OPTIONAL)) {
            Worklist.insert(DepAA);
            continue;
          }
          DepAA->getState().indicatePessimisticFixpoint();
          assert(DepAA->getState().isAtFixpoint() && "Expected fixpoint state!");
          if (!DepAA->getState().isValidState())
            InvalidAAs.insert(DepAA);
          else
            ChangedAAs.push_back(DepAA);
        }
      }
  
      // Add all abstract attributes that are potentially dependent on one that
      // changed to the work list.
      for (AbstractAttribute *ChangedAA : ChangedAAs)
        while (!ChangedAA->Deps.empty()) {
          Worklist.insert(
              cast<AbstractAttribute>(ChangedAA->Deps.back().getPointer()));
          ChangedAA->Deps.pop_back();
        }
  
      LLVM_DEBUG(dbgs() << "[Attributor] #Iteration: " << IterationCounter
                        << ", Worklist+Dependent size: " << Worklist.size()
                        << "\n");
  
      // Reset the changed and invalid set.
      ChangedAAs.clear();
      InvalidAAs.clear();
  
      // Update all abstract attribute in the work list and record the ones that
      // changed.
      for (AbstractAttribute *AA : Worklist) {
        const auto &AAState = AA->getState();
        if (!AAState.isAtFixpoint())
          if (updateAA(*AA) == ChangeStatus::CHANGED)
            ChangedAAs.push_back(AA);
  
        // Use the InvalidAAs vector to propagate invalid states fast transitively
        // without requiring updates.
        if (!AAState.isValidState())
          InvalidAAs.insert(AA);
      }
  
      // Add attributes to the changed set if they have been created in the last
      // iteration.
      ChangedAAs.append(DG.SyntheticRoot.begin() + NumAAs,
                        DG.SyntheticRoot.end());
  
      // Reset the work list and repopulate with the changed abstract attributes.
      // Note that dependent ones are added above.
      Worklist.clear();
      Worklist.insert(ChangedAAs.begin(), ChangedAAs.end());
  
    } while (!Worklist.empty() && (IterationCounter++ < MaxFixpointIterations ||
                                   VerifyMaxFixpointIterations));
  
    LLVM_DEBUG(dbgs() << "\n[Attributor] Fixpoint iteration done after: "
                      << IterationCounter << "/" << MaxFixpointIterations
                      << " iterations\n");
  
    // Reset abstract arguments not settled in a sound fixpoint by now. This
    // happens when we stopped the fixpoint iteration early. Note that only the
    // ones marked as "changed" *and* the ones transitively depending on them
    // need to be reverted to a pessimistic state. Others might not be in a
    // fixpoint state but we can use the optimistic results for them anyway.
    SmallPtrSet<AbstractAttribute *, 32> Visited;
    for (unsigned u = 0; u < ChangedAAs.size(); u++) {
      AbstractAttribute *ChangedAA = ChangedAAs[u];
      if (!Visited.insert(ChangedAA).second)
        continue;
  
      AbstractState &State = ChangedAA->getState();
      if (!State.isAtFixpoint()) {
        State.indicatePessimisticFixpoint();
  
        NumAttributesTimedOut++;
      }
  
      while (!ChangedAA->Deps.empty()) {
        ChangedAAs.push_back(
            cast<AbstractAttribute>(ChangedAA->Deps.back().getPointer()));
        ChangedAA->Deps.pop_back();
      }
    }
  
    LLVM_DEBUG({
      if (!Visited.empty())
        dbgs() << "\n[Attributor] Finalized " << Visited.size()
               << " abstract attributes.\n";
    });
  
    if (VerifyMaxFixpointIterations &&
        IterationCounter != MaxFixpointIterations) {
      errs() << "\n[Attributor] Fixpoint iteration done after: "
             << IterationCounter << "/" << MaxFixpointIterations
             << " iterations\n";
      llvm_unreachable("The fixpoint was not reached with exactly the number of "
                       "specified iterations!");
    }
  }
  
  ChangeStatus Attributor::manifestAttributes() {
    TimeTraceScope TimeScope("Attributor::manifestAttributes");
    size_t NumFinalAAs = DG.SyntheticRoot.Deps.size();
  
    unsigned NumManifested = 0;
    unsigned NumAtFixpoint = 0;
    ChangeStatus ManifestChange = ChangeStatus::UNCHANGED;
    for (auto &DepAA : DG.SyntheticRoot.Deps) {
      AbstractAttribute *AA = cast<AbstractAttribute>(DepAA.getPointer());
      AbstractState &State = AA->getState();
  
      // If there is not already a fixpoint reached, we can now take the
      // optimistic state. This is correct because we enforced a pessimistic one
      // on abstract attributes that were transitively dependent on a changed one
      // already above.
      if (!State.isAtFixpoint())
        State.indicateOptimisticFixpoint();
  
      // If the state is invalid, we do not try to manifest it.
      if (!State.isValidState())
        continue;
  
      // Skip dead code.
      if (isAssumedDead(*AA, nullptr, /* CheckBBLivenessOnly */ true))
        continue;
      // Check if the manifest debug counter that allows skipping manifestation of
      // AAs
      if (!DebugCounter::shouldExecute(ManifestDBGCounter))
        continue;
      // Manifest the state and record if we changed the IR.
      ChangeStatus LocalChange = AA->manifest(*this);
      if (LocalChange == ChangeStatus::CHANGED && AreStatisticsEnabled())
        AA->trackStatistics();
      LLVM_DEBUG(dbgs() << "[Attributor] Manifest " << LocalChange << " : " << *AA
                        << "\n");
  
      ManifestChange = ManifestChange | LocalChange;
  
      NumAtFixpoint++;
      NumManifested += (LocalChange == ChangeStatus::CHANGED);
    }
  
    (void)NumManifested;
    (void)NumAtFixpoint;
    LLVM_DEBUG(dbgs() << "\n[Attributor] Manifested " << NumManifested
                      << " arguments while " << NumAtFixpoint
                      << " were in a valid fixpoint state\n");
  
    NumAttributesManifested += NumManifested;
    NumAttributesValidFixpoint += NumAtFixpoint;
  
    (void)NumFinalAAs;
    if (NumFinalAAs != DG.SyntheticRoot.Deps.size()) {
      for (unsigned u = NumFinalAAs; u < DG.SyntheticRoot.Deps.size(); ++u)
        errs() << "Unexpected abstract attribute: "
               << cast<AbstractAttribute>(DG.SyntheticRoot.Deps[u].getPointer())
               << " :: "
               << cast<AbstractAttribute>(DG.SyntheticRoot.Deps[u].getPointer())
                      ->getIRPosition()
                      .getAssociatedValue()
               << "\n";
      llvm_unreachable("Expected the final number of abstract attributes to "
                       "remain unchanged!");
    }
    return ManifestChange;
  }
  
  void Attributor::identifyDeadInternalFunctions() {
    // Early exit if we don't intend to delete functions.
    if (!DeleteFns)
      return;
  
    // Identify dead internal functions and delete them. This happens outside
    // the other fixpoint analysis as we might treat potentially dead functions
    // as live to lower the number of iterations. If they happen to be dead, the
    // below fixpoint loop will identify and eliminate them.
    SmallVector<Function *, 8> InternalFns;
    for (Function *F : Functions)
      if (F->hasLocalLinkage())
        InternalFns.push_back(F);
  
    SmallPtrSet<Function *, 8> LiveInternalFns;
    bool FoundLiveInternal = true;
    while (FoundLiveInternal) {
      FoundLiveInternal = false;
      for (unsigned u = 0, e = InternalFns.size(); u < e; ++u) {
        Function *F = InternalFns[u];
        if (!F)
          continue;
  
        bool AllCallSitesKnown;
        if (checkForAllCallSites(
                [&](AbstractCallSite ACS) {
                  Function *Callee = ACS.getInstruction()->getFunction();
                  return ToBeDeletedFunctions.count(Callee) ||
                         (Functions.count(Callee) && Callee->hasLocalLinkage() &&
                          !LiveInternalFns.count(Callee));
                },
                *F, true, nullptr, AllCallSitesKnown)) {
          continue;
        }
  
        LiveInternalFns.insert(F);
        InternalFns[u] = nullptr;
        FoundLiveInternal = true;
      }
    }
  
    for (unsigned u = 0, e = InternalFns.size(); u < e; ++u)
      if (Function *F = InternalFns[u])
        ToBeDeletedFunctions.insert(F);
  }
  
  ChangeStatus Attributor::cleanupIR() {
    TimeTraceScope TimeScope("Attributor::cleanupIR");
    // Delete stuff at the end to avoid invalid references and a nice order.
    LLVM_DEBUG(dbgs() << "\n[Attributor] Delete at least "
                      << ToBeDeletedFunctions.size() << " functions and "
                      << ToBeDeletedBlocks.size() << " blocks and "
                      << ToBeDeletedInsts.size() << " instructions and "
                      << ToBeChangedUses.size() << " uses\n");
  
    SmallVector<WeakTrackingVH, 32> DeadInsts;
    SmallVector<Instruction *, 32> TerminatorsToFold;
  
    for (auto &It : ToBeChangedUses) {
      Use *U = It.first;
      Value *NewV = It.second;
      Value *OldV = U->get();
  
      // Do not replace uses in returns if the value is a must-tail call we will
      // not delete.
      if (isa<ReturnInst>(U->getUser()))
        if (auto *CI = dyn_cast<CallInst>(OldV->stripPointerCasts()))
          if (CI->isMustTailCall() && !ToBeDeletedInsts.count(CI))
            continue;
  
      LLVM_DEBUG(dbgs() << "Use " << *NewV << " in " << *U->getUser()
                        << " instead of " << *OldV << "\n");
      U->set(NewV);
      // Do not modify call instructions outside the SCC.
      if (auto *CB = dyn_cast<CallBase>(OldV))
        if (!Functions.count(CB->getCaller()))
          continue;
      if (Instruction *I = dyn_cast<Instruction>(OldV)) {
        CGModifiedFunctions.insert(I->getFunction());
        if (!isa<PHINode>(I) && !ToBeDeletedInsts.count(I) &&
            isInstructionTriviallyDead(I))
          DeadInsts.push_back(I);
      }
      if (isa<UndefValue>(NewV) && isa<CallBase>(U->getUser())) {
        auto *CB = cast<CallBase>(U->getUser());
        if (CB->isArgOperand(U)) {
          unsigned Idx = CB->getArgOperandNo(U);
          CB->removeParamAttr(Idx, Attribute::NoUndef);
          Function *Fn = CB->getCalledFunction();
          assert(Fn && "Expected callee when call argument is replaced!");
          if (Fn->arg_size() > Idx)
            Fn->removeParamAttr(Idx, Attribute::NoUndef);
        }
      }
      if (isa<Constant>(NewV) && isa<BranchInst>(U->getUser())) {
        Instruction *UserI = cast<Instruction>(U->getUser());
        if (isa<UndefValue>(NewV)) {
          ToBeChangedToUnreachableInsts.insert(UserI);
        } else {
          TerminatorsToFold.push_back(UserI);
        }
      }
    }
    for (auto &V : InvokeWithDeadSuccessor)
      if (InvokeInst *II = dyn_cast_or_null<InvokeInst>(V)) {
        bool UnwindBBIsDead = II->hasFnAttr(Attribute::NoUnwind);
        bool NormalBBIsDead = II->hasFnAttr(Attribute::NoReturn);
        bool Invoke2CallAllowed =
            !AAIsDead::mayCatchAsynchronousExceptions(*II->getFunction());
        assert((UnwindBBIsDead || NormalBBIsDead) &&
               "Invoke does not have dead successors!");
        BasicBlock *BB = II->getParent();
        BasicBlock *NormalDestBB = II->getNormalDest();
        if (UnwindBBIsDead) {
          Instruction *NormalNextIP = &NormalDestBB->front();
          if (Invoke2CallAllowed) {
            changeToCall(II);
            NormalNextIP = BB->getTerminator();
          }
          if (NormalBBIsDead)
            ToBeChangedToUnreachableInsts.insert(NormalNextIP);
        } else {
          assert(NormalBBIsDead && "Broken invariant!");
          if (!NormalDestBB->getUniquePredecessor())
            NormalDestBB = SplitBlockPredecessors(NormalDestBB, {BB}, ".dead");
          ToBeChangedToUnreachableInsts.insert(&NormalDestBB->front());
        }
      }
    for (Instruction *I : TerminatorsToFold) {
      CGModifiedFunctions.insert(I->getFunction());
      ConstantFoldTerminator(I->getParent());
    }
    for (auto &V : ToBeChangedToUnreachableInsts)
      if (Instruction *I = dyn_cast_or_null<Instruction>(V)) {
        CGModifiedFunctions.insert(I->getFunction());
        changeToUnreachable(I, /* UseLLVMTrap */ false);
      }
  
    for (auto &V : ToBeDeletedInsts) {
      if (Instruction *I = dyn_cast_or_null<Instruction>(V)) {
        I->dropDroppableUses();
        CGModifiedFunctions.insert(I->getFunction());
        if (!I->getType()->isVoidTy())
          I->replaceAllUsesWith(UndefValue::get(I->getType()));
        if (!isa<PHINode>(I) && isInstructionTriviallyDead(I))
          DeadInsts.push_back(I);
        else
          I->eraseFromParent();
      }
    }
  
    LLVM_DEBUG(dbgs() << "[Attributor] DeadInsts size: " << DeadInsts.size()
                      << "\n");
  
    RecursivelyDeleteTriviallyDeadInstructions(DeadInsts);
  
    if (unsigned NumDeadBlocks = ToBeDeletedBlocks.size()) {
      SmallVector<BasicBlock *, 8> ToBeDeletedBBs;
      ToBeDeletedBBs.reserve(NumDeadBlocks);
      for (BasicBlock *BB : ToBeDeletedBlocks) {
        CGModifiedFunctions.insert(BB->getParent());
        ToBeDeletedBBs.push_back(BB);
      }
      // Actually we do not delete the blocks but squash them into a single
      // unreachable but untangling branches that jump here is something we need
      // to do in a more generic way.
      DetatchDeadBlocks(ToBeDeletedBBs, nullptr);
    }
  
    identifyDeadInternalFunctions();
  
    // Rewrite the functions as requested during manifest.
    ChangeStatus ManifestChange = rewriteFunctionSignatures(CGModifiedFunctions);
  
    for (Function *Fn : CGModifiedFunctions)
      if (!ToBeDeletedFunctions.count(Fn))
        CGUpdater.reanalyzeFunction(*Fn);
  
    for (Function *Fn : ToBeDeletedFunctions) {
      if (!Functions.count(Fn))
        continue;
      CGUpdater.removeFunction(*Fn);
    }
  
    if (!ToBeChangedUses.empty())
      ManifestChange = ChangeStatus::CHANGED;
  
    if (!ToBeChangedToUnreachableInsts.empty())
      ManifestChange = ChangeStatus::CHANGED;
  
    if (!ToBeDeletedFunctions.empty())
      ManifestChange = ChangeStatus::CHANGED;
  
    if (!ToBeDeletedBlocks.empty())
      ManifestChange = ChangeStatus::CHANGED;
  
    if (!ToBeDeletedInsts.empty())
      ManifestChange = ChangeStatus::CHANGED;
  
    if (!InvokeWithDeadSuccessor.empty())
      ManifestChange = ChangeStatus::CHANGED;
  
    if (!DeadInsts.empty())
      ManifestChange = ChangeStatus::CHANGED;
  
    NumFnDeleted += ToBeDeletedFunctions.size();
  
    LLVM_DEBUG(dbgs() << "[Attributor] Deleted " << ToBeDeletedFunctions.size()
                      << " functions after manifest.\n");
  
  #ifdef EXPENSIVE_CHECKS
    for (Function *F : Functions) {
      if (ToBeDeletedFunctions.count(F))
        continue;
      assert(!verifyFunction(*F, &errs()) && "Module verification failed!");
    }
  #endif
  
    return ManifestChange;
  }
  
  ChangeStatus Attributor::run() {
    TimeTraceScope TimeScope("Attributor::run");
  
    Phase = AttributorPhase::UPDATE;
    runTillFixpoint();
  
    // dump graphs on demand
    if (DumpDepGraph)
      DG.dumpGraph();
  
    if (ViewDepGraph)
      DG.viewGraph();
  
    if (PrintDependencies)
      DG.print();
  
    Phase = AttributorPhase::MANIFEST;
    ChangeStatus ManifestChange = manifestAttributes();
  
    Phase = AttributorPhase::CLEANUP;
    ChangeStatus CleanupChange = cleanupIR();
  
    return ManifestChange | CleanupChange;
  }
  
  ChangeStatus Attributor::updateAA(AbstractAttribute &AA) {
    TimeTraceScope TimeScope(
        AA.getName() + std::to_string(AA.getIRPosition().getPositionKind()) +
        "::updateAA");
    assert(Phase == AttributorPhase::UPDATE &&
           "We can update AA only in the update stage!");
  
    // Use a new dependence vector for this update.
    DependenceVector DV;
    DependenceStack.push_back(&DV);
  
    auto &AAState = AA.getState();
    ChangeStatus CS = ChangeStatus::UNCHANGED;
    if (!isAssumedDead(AA, nullptr, /* CheckBBLivenessOnly */ true))
      CS = AA.update(*this);
  
    if (DV.empty()) {
      // If the attribute did not query any non-fix information, the state
      // will not change and we can indicate that right away.
      AAState.indicateOptimisticFixpoint();
    }
  
    if (!AAState.isAtFixpoint())
      rememberDependences();
  
    // Verify the stack was used properly, that is we pop the dependence vector we
    // put there earlier.
    DependenceVector *PoppedDV = DependenceStack.pop_back_val();
    (void)PoppedDV;
    assert(PoppedDV == &DV && "Inconsistent usage of the dependence stack!");
  
    return CS;
  }
  
  void Attributor::createShallowWrapper(Function &F) {
    assert(!F.isDeclaration() && "Cannot create a wrapper around a declaration!");
  
    Module &M = *F.getParent();
    LLVMContext &Ctx = M.getContext();
    FunctionType *FnTy = F.getFunctionType();
  
    Function *Wrapper =
        Function::Create(FnTy, F.getLinkage(), F.getAddressSpace(), F.getName());
    F.setName(""); // set the inside function anonymous
    M.getFunctionList().insert(F.getIterator(), Wrapper);
  
    F.setLinkage(GlobalValue::InternalLinkage);
  
    F.replaceAllUsesWith(Wrapper);
    assert(F.use_empty() && "Uses remained after wrapper was created!");
  
    // Move the COMDAT section to the wrapper.
    // TODO: Check if we need to keep it for F as well.
    Wrapper->setComdat(F.getComdat());
    F.setComdat(nullptr);
  
    // Copy all metadata and attributes but keep them on F as well.
    SmallVector<std::pair<unsigned, MDNode *>, 1> MDs;
    F.getAllMetadata(MDs);
    for (auto MDIt : MDs)
      Wrapper->addMetadata(MDIt.first, *MDIt.second);
    Wrapper->setAttributes(F.getAttributes());
  
    // Create the call in the wrapper.
    BasicBlock *EntryBB = BasicBlock::Create(Ctx, "entry", Wrapper);
  
    SmallVector<Value *, 8> Args;
    Argument *FArgIt = F.arg_begin();
    for (Argument &Arg : Wrapper->args()) {
      Args.push_back(&Arg);
      Arg.setName((FArgIt++)->getName());
    }
  
    CallInst *CI = CallInst::Create(&F, Args, "", EntryBB);
    CI->setTailCall(true);
    CI->addAttribute(AttributeList::FunctionIndex, Attribute::NoInline);
    ReturnInst::Create(Ctx, CI->getType()->isVoidTy() ? nullptr : CI, EntryBB);
  
    NumFnShallowWrappersCreated++;
  }
  
  /// Make another copy of the function \p F such that the copied version has
  /// internal linkage afterwards and can be analysed. Then we replace all uses
  /// of the original function to the copied one
  ///
  /// Only non-exactly defined functions that have `linkonce_odr` or `weak_odr`
  /// linkage can be internalized because these linkages guarantee that other
  /// definitions with the same name have the same semantics as this one
  ///
  static Function *internalizeFunction(Function &F) {
    assert(AllowDeepWrapper && "Cannot create a copy if not allowed.");
    assert(!F.isDeclaration() && !F.hasExactDefinition() &&
           !GlobalValue::isInterposableLinkage(F.getLinkage()) &&
           "Trying to internalize function which cannot be internalized.");
  
    Module &M = *F.getParent();
    FunctionType *FnTy = F.getFunctionType();
  
    // create a copy of the current function
    Function *Copied = Function::Create(FnTy, F.getLinkage(), F.getAddressSpace(),
                                        F.getName() + ".internalized");
    ValueToValueMapTy VMap;
    auto *NewFArgIt = Copied->arg_begin();
    for (auto &Arg : F.args()) {
      auto ArgName = Arg.getName();
      NewFArgIt->setName(ArgName);
      VMap[&Arg] = &(*NewFArgIt++);
    }
    SmallVector<ReturnInst *, 8> Returns;
  
    // Copy the body of the original function to the new one
    CloneFunctionInto(Copied, &F, VMap, CloneFunctionChangeType::LocalChangesOnly,
                      Returns);
  
    // Set the linakage and visibility late as CloneFunctionInto has some implicit
    // requirements.
    Copied->setVisibility(GlobalValue::DefaultVisibility);
    Copied->setLinkage(GlobalValue::PrivateLinkage);
  
    // Copy metadata
    SmallVector<std::pair<unsigned, MDNode *>, 1> MDs;
    F.getAllMetadata(MDs);
    for (auto MDIt : MDs)
      Copied->addMetadata(MDIt.first, *MDIt.second);
  
    M.getFunctionList().insert(F.getIterator(), Copied);
    F.replaceAllUsesWith(Copied);
    Copied->setDSOLocal(true);
  
    return Copied;
  }
  
  bool Attributor::isValidFunctionSignatureRewrite(
      Argument &Arg, ArrayRef<Type *> ReplacementTypes) {
  
    auto CallSiteCanBeChanged = [](AbstractCallSite ACS) {
      // Forbid the call site to cast the function return type. If we need to
      // rewrite these functions we need to re-create a cast for the new call site
      // (if the old had uses).
      if (!ACS.getCalledFunction() ||
          ACS.getInstruction()->getType() !=
              ACS.getCalledFunction()->getReturnType())
        return false;
      // Forbid must-tail calls for now.
      return !ACS.isCallbackCall() && !ACS.getInstruction()->isMustTailCall();
    };
  
    Function *Fn = Arg.getParent();
    // Avoid var-arg functions for now.
    if (Fn->isVarArg()) {
      LLVM_DEBUG(dbgs() << "[Attributor] Cannot rewrite var-args functions\n");
      return false;
    }
  
    // Avoid functions with complicated argument passing semantics.
    AttributeList FnAttributeList = Fn->getAttributes();
    if (FnAttributeList.hasAttrSomewhere(Attribute::Nest) ||
        FnAttributeList.hasAttrSomewhere(Attribute::StructRet) ||
        FnAttributeList.hasAttrSomewhere(Attribute::InAlloca) ||
        FnAttributeList.hasAttrSomewhere(Attribute::Preallocated)) {
      LLVM_DEBUG(
          dbgs() << "[Attributor] Cannot rewrite due to complex attribute\n");
      return false;
    }
  
    // Avoid callbacks for now.
    bool AllCallSitesKnown;
    if (!checkForAllCallSites(CallSiteCanBeChanged, *Fn, true, nullptr,
                              AllCallSitesKnown)) {
      LLVM_DEBUG(dbgs() << "[Attributor] Cannot rewrite all call sites\n");
      return false;
    }
  
    auto InstPred = [](Instruction &I) {
      if (auto *CI = dyn_cast<CallInst>(&I))
        return !CI->isMustTailCall();
      return true;
    };
  
    // Forbid must-tail calls for now.
    // TODO:
    auto &OpcodeInstMap = InfoCache.getOpcodeInstMapForFunction(*Fn);
    if (!checkForAllInstructionsImpl(nullptr, OpcodeInstMap, InstPred, nullptr,
                                     nullptr, {Instruction::Call})) {
      LLVM_DEBUG(dbgs() << "[Attributor] Cannot rewrite due to instructions\n");
      return false;
    }
  
    return true;
  }
  
  bool Attributor::registerFunctionSignatureRewrite(
      Argument &Arg, ArrayRef<Type *> ReplacementTypes,
      ArgumentReplacementInfo::CalleeRepairCBTy &&CalleeRepairCB,
      ArgumentReplacementInfo::ACSRepairCBTy &&ACSRepairCB) {
    LLVM_DEBUG(dbgs() << "[Attributor] Register new rewrite of " << Arg << " in "
                      << Arg.getParent()->getName() << " with "
                      << ReplacementTypes.size() << " replacements\n");
    assert(isValidFunctionSignatureRewrite(Arg, ReplacementTypes) &&
           "Cannot register an invalid rewrite");
  
    Function *Fn = Arg.getParent();
    SmallVectorImpl<std::unique_ptr<ArgumentReplacementInfo>> &ARIs =
        ArgumentReplacementMap[Fn];
    if (ARIs.empty())
      ARIs.resize(Fn->arg_size());
  
    // If we have a replacement already with less than or equal new arguments,
    // ignore this request.
    std::unique_ptr<ArgumentReplacementInfo> &ARI = ARIs[Arg.getArgNo()];
    if (ARI && ARI->getNumReplacementArgs() <= ReplacementTypes.size()) {
      LLVM_DEBUG(dbgs() << "[Attributor] Existing rewrite is preferred\n");
      return false;
    }
  
    // If we have a replacement already but we like the new one better, delete
    // the old.
    ARI.reset();
  
    LLVM_DEBUG(dbgs() << "[Attributor] Register new rewrite of " << Arg << " in "
                      << Arg.getParent()->getName() << " with "
                      << ReplacementTypes.size() << " replacements\n");
  
    // Remember the replacement.
    ARI.reset(new ArgumentReplacementInfo(*this, Arg, ReplacementTypes,
                                          std::move(CalleeRepairCB),
                                          std::move(ACSRepairCB)));
  
    return true;
  }
  
  bool Attributor::shouldSeedAttribute(AbstractAttribute &AA) {
    bool Result = true;
  #ifndef NDEBUG
    if (SeedAllowList.size() != 0)
      Result =
          std::count(SeedAllowList.begin(), SeedAllowList.end(), AA.getName());
    Function *Fn = AA.getAnchorScope();
    if (FunctionSeedAllowList.size() != 0 && Fn)
      Result &= std::count(FunctionSeedAllowList.begin(),
                           FunctionSeedAllowList.end(), Fn->getName());
  #endif
    return Result;
  }
  
  ChangeStatus Attributor::rewriteFunctionSignatures(
      SmallPtrSetImpl<Function *> &ModifiedFns) {
    ChangeStatus Changed = ChangeStatus::UNCHANGED;
  
    for (auto &It : ArgumentReplacementMap) {
      Function *OldFn = It.getFirst();
  
      // Deleted functions do not require rewrites.
      if (!Functions.count(OldFn) || ToBeDeletedFunctions.count(OldFn))
        continue;
  
      const SmallVectorImpl<std::unique_ptr<ArgumentReplacementInfo>> &ARIs =
          It.getSecond();
      assert(ARIs.size() == OldFn->arg_size() && "Inconsistent state!");
  
      SmallVector<Type *, 16> NewArgumentTypes;
      SmallVector<AttributeSet, 16> NewArgumentAttributes;
  
      // Collect replacement argument types and copy over existing attributes.
      AttributeList OldFnAttributeList = OldFn->getAttributes();
      for (Argument &Arg : OldFn->args()) {
        if (const std::unique_ptr<ArgumentReplacementInfo> &ARI =
                ARIs[Arg.getArgNo()]) {
          NewArgumentTypes.append(ARI->ReplacementTypes.begin(),
                                  ARI->ReplacementTypes.end());
          NewArgumentAttributes.append(ARI->getNumReplacementArgs(),
                                       AttributeSet());
        } else {
          NewArgumentTypes.push_back(Arg.getType());
          NewArgumentAttributes.push_back(
              OldFnAttributeList.getParamAttributes(Arg.getArgNo()));
        }
      }
  
      FunctionType *OldFnTy = OldFn->getFunctionType();
      Type *RetTy = OldFnTy->getReturnType();
  
      // Construct the new function type using the new arguments types.
      FunctionType *NewFnTy =
          FunctionType::get(RetTy, NewArgumentTypes, OldFnTy->isVarArg());
  
      LLVM_DEBUG(dbgs() << "[Attributor] Function rewrite '" << OldFn->getName()
                        << "' from " << *OldFn->getFunctionType() << " to "
                        << *NewFnTy << "\n");
  
      // Create the new function body and insert it into the module.
      Function *NewFn = Function::Create(NewFnTy, OldFn->getLinkage(),
                                         OldFn->getAddressSpace(), "");
      OldFn->getParent()->getFunctionList().insert(OldFn->getIterator(), NewFn);
      NewFn->takeName(OldFn);
      NewFn->copyAttributesFrom(OldFn);
  
      // Patch the pointer to LLVM function in debug info descriptor.
      NewFn->setSubprogram(OldFn->getSubprogram());
      OldFn->setSubprogram(nullptr);
  
      // Recompute the parameter attributes list based on the new arguments for
      // the function.
      LLVMContext &Ctx = OldFn->getContext();
      NewFn->setAttributes(AttributeList::get(
          Ctx, OldFnAttributeList.getFnAttributes(),
          OldFnAttributeList.getRetAttributes(), NewArgumentAttributes));
  
      // Since we have now created the new function, splice the body of the old
      // function right into the new function, leaving the old rotting hulk of the
      // function empty.
      NewFn->getBasicBlockList().splice(NewFn->begin(),
                                        OldFn->getBasicBlockList());
  
      // Fixup block addresses to reference new function.
      SmallVector<BlockAddress *, 8u> BlockAddresses;
      for (User *U : OldFn->users())
        if (auto *BA = dyn_cast<BlockAddress>(U))
          BlockAddresses.push_back(BA);
      for (auto *BA : BlockAddresses)
        BA->replaceAllUsesWith(BlockAddress::get(NewFn, BA->getBasicBlock()));
  
      // Set of all "call-like" instructions that invoke the old function mapped
      // to their new replacements.
      SmallVector<std::pair<CallBase *, CallBase *>, 8> CallSitePairs;
  
      // Callback to create a new "call-like" instruction for a given one.
      auto CallSiteReplacementCreator = [&](AbstractCallSite ACS) {
        CallBase *OldCB = cast<CallBase>(ACS.getInstruction());
        const AttributeList &OldCallAttributeList = OldCB->getAttributes();
  
        // Collect the new argument operands for the replacement call site.
        SmallVector<Value *, 16> NewArgOperands;
        SmallVector<AttributeSet, 16> NewArgOperandAttributes;
        for (unsigned OldArgNum = 0; OldArgNum < ARIs.size(); ++OldArgNum) {
          unsigned NewFirstArgNum = NewArgOperands.size();
          (void)NewFirstArgNum; // only used inside assert.
          if (const std::unique_ptr<ArgumentReplacementInfo> &ARI =
                  ARIs[OldArgNum]) {
            if (ARI->ACSRepairCB)
              ARI->ACSRepairCB(*ARI, ACS, NewArgOperands);
            assert(ARI->getNumReplacementArgs() + NewFirstArgNum ==
                       NewArgOperands.size() &&
                   "ACS repair callback did not provide as many operand as new "
                   "types were registered!");
            // TODO: Exose the attribute set to the ACS repair callback
            NewArgOperandAttributes.append(ARI->ReplacementTypes.size(),
                                           AttributeSet());
          } else {
            NewArgOperands.push_back(ACS.getCallArgOperand(OldArgNum));
            NewArgOperandAttributes.push_back(
                OldCallAttributeList.getParamAttributes(OldArgNum));
          }
        }
  
        assert(NewArgOperands.size() == NewArgOperandAttributes.size() &&
               "Mismatch # argument operands vs. # argument operand attributes!");
        assert(NewArgOperands.size() == NewFn->arg_size() &&
               "Mismatch # argument operands vs. # function arguments!");
  
        SmallVector<OperandBundleDef, 4> OperandBundleDefs;
        OldCB->getOperandBundlesAsDefs(OperandBundleDefs);
  
        // Create a new call or invoke instruction to replace the old one.
        CallBase *NewCB;
        if (InvokeInst *II = dyn_cast<InvokeInst>(OldCB)) {
          NewCB =
              InvokeInst::Create(NewFn, II->getNormalDest(), II->getUnwindDest(),
                                 NewArgOperands, OperandBundleDefs, "", OldCB);
        } else {
          auto *NewCI = CallInst::Create(NewFn, NewArgOperands, OperandBundleDefs,
                                         "", OldCB);
          NewCI->setTailCallKind(cast<CallInst>(OldCB)->getTailCallKind());
          NewCB = NewCI;
        }
  
        // Copy over various properties and the new attributes.
        NewCB->copyMetadata(*OldCB, {LLVMContext::MD_prof, LLVMContext::MD_dbg});
        NewCB->setCallingConv(OldCB->getCallingConv());
        NewCB->takeName(OldCB);
        NewCB->setAttributes(AttributeList::get(
            Ctx, OldCallAttributeList.getFnAttributes(),
            OldCallAttributeList.getRetAttributes(), NewArgOperandAttributes));
  
        CallSitePairs.push_back({OldCB, NewCB});
        return true;
      };
  
      // Use the CallSiteReplacementCreator to create replacement call sites.
      bool AllCallSitesKnown;
      bool Success = checkForAllCallSites(CallSiteReplacementCreator, *OldFn,
                                          true, nullptr, AllCallSitesKnown);
      (void)Success;
      assert(Success && "Assumed call site replacement to succeed!");
  
      // Rewire the arguments.
      Argument *OldFnArgIt = OldFn->arg_begin();
      Argument *NewFnArgIt = NewFn->arg_begin();
      for (unsigned OldArgNum = 0; OldArgNum < ARIs.size();
           ++OldArgNum, ++OldFnArgIt) {
        if (const std::unique_ptr<ArgumentReplacementInfo> &ARI =
                ARIs[OldArgNum]) {
          if (ARI->CalleeRepairCB)
            ARI->CalleeRepairCB(*ARI, *NewFn, NewFnArgIt);
          NewFnArgIt += ARI->ReplacementTypes.size();
        } else {
          NewFnArgIt->takeName(&*OldFnArgIt);
          OldFnArgIt->replaceAllUsesWith(&*NewFnArgIt);
          ++NewFnArgIt;
        }
      }
  
      // Eliminate the instructions *after* we visited all of them.
      for (auto &CallSitePair : CallSitePairs) {
        CallBase &OldCB = *CallSitePair.first;
        CallBase &NewCB = *CallSitePair.second;
        assert(OldCB.getType() == NewCB.getType() &&
               "Cannot handle call sites with different types!");
        ModifiedFns.insert(OldCB.getFunction());
        CGUpdater.replaceCallSite(OldCB, NewCB);
        OldCB.replaceAllUsesWith(&NewCB);
        OldCB.eraseFromParent();
      }
  
      // Replace the function in the call graph (if any).
      CGUpdater.replaceFunctionWith(*OldFn, *NewFn);
  
      // If the old function was modified and needed to be reanalyzed, the new one
      // does now.
      if (ModifiedFns.erase(OldFn))
        ModifiedFns.insert(NewFn);
  
      Changed = ChangeStatus::CHANGED;
    }
  
    return Changed;
  }
  
  void InformationCache::initializeInformationCache(const Function &CF,
                                                    FunctionInfo &FI) {
    // As we do not modify the function here we can remove the const
    // withouth breaking implicit assumptions. At the end of the day, we could
    // initialize the cache eagerly which would look the same to the users.
    Function &F = const_cast<Function &>(CF);
  
    // Walk all instructions to find interesting instructions that might be
    // queried by abstract attributes during their initialization or update.
    // This has to happen before we create attributes.
  
    for (Instruction &I : instructions(&F)) {
      bool IsInterestingOpcode = false;
  
      // To allow easy access to all instructions in a function with a given
      // opcode we store them in the InfoCache. As not all opcodes are interesting
      // to concrete attributes we only cache the ones that are as identified in
      // the following switch.
      // Note: There are no concrete attributes now so this is initially empty.
      switch (I.getOpcode()) {
      default:
        assert(!isa<CallBase>(&I) &&
               "New call base instruction type needs to be known in the "
               "Attributor.");
        break;
      case Instruction::Call:
        // Calls are interesting on their own, additionally:
        // For `llvm.assume` calls we also fill the KnowledgeMap as we find them.
        // For `must-tail` calls we remember the caller and callee.
        if (IntrinsicInst *Assume = dyn_cast<IntrinsicInst>(&I)) {
          if (Assume->getIntrinsicID() == Intrinsic::assume)
            fillMapFromAssume(*Assume, KnowledgeMap);
        } else if (cast<CallInst>(I).isMustTailCall()) {
          FI.ContainsMustTailCall = true;
          if (const Function *Callee = cast<CallInst>(I).getCalledFunction())
            getFunctionInfo(*Callee).CalledViaMustTail = true;
        }
        LLVM_FALLTHROUGH;
      case Instruction::CallBr:
      case Instruction::Invoke:
      case Instruction::CleanupRet:
      case Instruction::CatchSwitch:
      case Instruction::AtomicRMW:
      case Instruction::AtomicCmpXchg:
      case Instruction::Br:
      case Instruction::Resume:
      case Instruction::Ret:
      case Instruction::Load:
        // The alignment of a pointer is interesting for loads.
      case Instruction::Store:
        // The alignment of a pointer is interesting for stores.
        IsInterestingOpcode = true;
      }
      if (IsInterestingOpcode) {
        auto *&Insts = FI.OpcodeInstMap[I.getOpcode()];
        if (!Insts)
          Insts = new (Allocator) InstructionVectorTy();
        Insts->push_back(&I);
      }
      if (I.mayReadOrWriteMemory())
        FI.RWInsts.push_back(&I);
    }
  
    if (F.hasFnAttribute(Attribute::AlwaysInline) &&
        isInlineViable(F).isSuccess())
      InlineableFunctions.insert(&F);
  }
  
  AAResults *InformationCache::getAAResultsForFunction(const Function &F) {
    return AG.getAnalysis<AAManager>(F);
  }
  
  InformationCache::FunctionInfo::~FunctionInfo() {
    // The instruction vectors are allocated using a BumpPtrAllocator, we need to
    // manually destroy them.
    for (auto &It : OpcodeInstMap)
      It.getSecond()->~InstructionVectorTy();
  }
  
  void Attributor::recordDependence(const AbstractAttribute &FromAA,
                                    const AbstractAttribute &ToAA,
                                    DepClassTy DepClass) {
    if (DepClass == DepClassTy::NONE)
      return;
    // If we are outside of an update, thus before the actual fixpoint iteration
    // started (= when we create AAs), we do not track dependences because we will
    // put all AAs into the initial worklist anyway.
    if (DependenceStack.empty())
      return;
    if (FromAA.getState().isAtFixpoint())
      return;
    DependenceStack.back()->push_back({&FromAA, &ToAA, DepClass});
  }
  
  void Attributor::rememberDependences() {
    assert(!DependenceStack.empty() && "No dependences to remember!");
  
    for (DepInfo &DI : *DependenceStack.back()) {
      assert((DI.DepClass == DepClassTy::REQUIRED ||
              DI.DepClass == DepClassTy::OPTIONAL) &&
             "Expected required or optional dependence (1 bit)!");
      auto &DepAAs = const_cast<AbstractAttribute &>(*DI.FromAA).Deps;
      DepAAs.push_back(AbstractAttribute::DepTy(
          const_cast<AbstractAttribute *>(DI.ToAA), unsigned(DI.DepClass)));
    }
  }
  
  void Attributor::identifyDefaultAbstractAttributes(Function &F) {
    if (!VisitedFunctions.insert(&F).second)
      return;
    if (F.isDeclaration())
      return;
  
    // In non-module runs we need to look at the call sites of a function to
    // determine if it is part of a must-tail call edge. This will influence what
    // attributes we can derive.
    InformationCache::FunctionInfo &FI = InfoCache.getFunctionInfo(F);
    if (!isModulePass() && !FI.CalledViaMustTail) {
      for (const Use &U : F.uses())
        if (const auto *CB = dyn_cast<CallBase>(U.getUser()))
          if (CB->isCallee(&U) && CB->isMustTailCall())
            FI.CalledViaMustTail = true;
    }
  
    IRPosition FPos = IRPosition::function(F);
  
    // Check for dead BasicBlocks in every function.
    // We need dead instruction detection because we do not want to deal with
    // broken IR in which SSA rules do not apply.
    getOrCreateAAFor<AAIsDead>(FPos);
  
    // Every function might be "will-return".
    getOrCreateAAFor<AAWillReturn>(FPos);
  
    // Every function might contain instructions that cause "undefined behavior".
    getOrCreateAAFor<AAUndefinedBehavior>(FPos);
  
    // Every function can be nounwind.
    getOrCreateAAFor<AANoUnwind>(FPos);
  
    // Every function might be marked "nosync"
    getOrCreateAAFor<AANoSync>(FPos);
  
    // Every function might be "no-free".
    getOrCreateAAFor<AANoFree>(FPos);
  
    // Every function might be "no-return".
    getOrCreateAAFor<AANoReturn>(FPos);
  
    // Every function might be "no-recurse".
    getOrCreateAAFor<AANoRecurse>(FPos);
  
    // Every function might be "readnone/readonly/writeonly/...".
    getOrCreateAAFor<AAMemoryBehavior>(FPos);
  
    // Every function can be "readnone/argmemonly/inaccessiblememonly/...".
    getOrCreateAAFor<AAMemoryLocation>(FPos);
  
    // Every function might be applicable for Heap-To-Stack conversion.
    if (EnableHeapToStack)
      getOrCreateAAFor<AAHeapToStack>(FPos);
  
    // Return attributes are only appropriate if the return type is non void.
    Type *ReturnType = F.getReturnType();
    if (!ReturnType->isVoidTy()) {
      // Argument attribute "returned" --- Create only one per function even
      // though it is an argument attribute.
      getOrCreateAAFor<AAReturnedValues>(FPos);
  
      IRPosition RetPos = IRPosition::returned(F);
  
      // Every returned value might be dead.
      getOrCreateAAFor<AAIsDead>(RetPos);
  
      // Every function might be simplified.
      getOrCreateAAFor<AAValueSimplify>(RetPos);
  
      // Every returned value might be marked noundef.
      getOrCreateAAFor<AANoUndef>(RetPos);
  
      if (ReturnType->isPointerTy()) {
  
        // Every function with pointer return type might be marked align.
        getOrCreateAAFor<AAAlign>(RetPos);
  
        // Every function with pointer return type might be marked nonnull.
        getOrCreateAAFor<AANonNull>(RetPos);
  
        // Every function with pointer return type might be marked noalias.
        getOrCreateAAFor<AANoAlias>(RetPos);
  
        // Every function with pointer return type might be marked
        // dereferenceable.
        getOrCreateAAFor<AADereferenceable>(RetPos);
      }
    }
  
    for (Argument &Arg : F.args()) {
      IRPosition ArgPos = IRPosition::argument(Arg);
  
      // Every argument might be simplified.
      getOrCreateAAFor<AAValueSimplify>(ArgPos);
  
      // Every argument might be dead.
      getOrCreateAAFor<AAIsDead>(ArgPos);
  
      // Every argument might be marked noundef.
      getOrCreateAAFor<AANoUndef>(ArgPos);
  
      if (Arg.getType()->isPointerTy()) {
        // Every argument with pointer type might be marked nonnull.
        getOrCreateAAFor<AANonNull>(ArgPos);
  
        // Every argument with pointer type might be marked noalias.
        getOrCreateAAFor<AANoAlias>(ArgPos);
  
        // Every argument with pointer type might be marked dereferenceable.
        getOrCreateAAFor<AADereferenceable>(ArgPos);
  
        // Every argument with pointer type might be marked align.
        getOrCreateAAFor<AAAlign>(ArgPos);
  
        // Every argument with pointer type might be marked nocapture.
        getOrCreateAAFor<AANoCapture>(ArgPos);
  
        // Every argument with pointer type might be marked
        // "readnone/readonly/writeonly/..."
        getOrCreateAAFor<AAMemoryBehavior>(ArgPos);
  
        // Every argument with pointer type might be marked nofree.
        getOrCreateAAFor<AANoFree>(ArgPos);
  
        // Every argument with pointer type might be privatizable (or promotable)
        getOrCreateAAFor<AAPrivatizablePtr>(ArgPos);
      }
    }
  
    auto CallSitePred = [&](Instruction &I) -> bool {
      auto &CB = cast<CallBase>(I);
      IRPosition CBRetPos = IRPosition::callsite_returned(CB);
  
      // Call sites might be dead if they do not have side effects and no live
      // users. The return value might be dead if there are no live users.
      getOrCreateAAFor<AAIsDead>(CBRetPos);
  
      Function *Callee = CB.getCalledFunction();
      // TODO: Even if the callee is not known now we might be able to simplify
      //       the call/callee.
      if (!Callee)
        return true;
  
      // Skip declarations except if annotations on their call sites were
      // explicitly requested.
      if (!AnnotateDeclarationCallSites && Callee->isDeclaration() &&
          !Callee->hasMetadata(LLVMContext::MD_callback))
        return true;
  
      if (!Callee->getReturnType()->isVoidTy() && !CB.use_empty()) {
  
        IRPosition CBRetPos = IRPosition::callsite_returned(CB);
  
        // Call site return integer values might be limited by a constant range.
        if (Callee->getReturnType()->isIntegerTy())
          getOrCreateAAFor<AAValueConstantRange>(CBRetPos);
      }
  
      for (int I = 0, E = CB.getNumArgOperands(); I < E; ++I) {
  
        IRPosition CBArgPos = IRPosition::callsite_argument(CB, I);
  
        // Every call site argument might be dead.
        getOrCreateAAFor<AAIsDead>(CBArgPos);
  
        // Call site argument might be simplified.
        getOrCreateAAFor<AAValueSimplify>(CBArgPos);
  
        // Every call site argument might be marked "noundef".
        getOrCreateAAFor<AANoUndef>(CBArgPos);
  
        if (!CB.getArgOperand(I)->getType()->isPointerTy())
          continue;
  
        // Call site argument attribute "non-null".
        getOrCreateAAFor<AANonNull>(CBArgPos);
  
        // Call site argument attribute "nocapture".
        getOrCreateAAFor<AANoCapture>(CBArgPos);
  
        // Call site argument attribute "no-alias".
        getOrCreateAAFor<AANoAlias>(CBArgPos);
  
        // Call site argument attribute "dereferenceable".
        getOrCreateAAFor<AADereferenceable>(CBArgPos);
  
        // Call site argument attribute "align".
        getOrCreateAAFor<AAAlign>(CBArgPos);
  
        // Call site argument attribute
        // "readnone/readonly/writeonly/..."
        getOrCreateAAFor<AAMemoryBehavior>(CBArgPos);
  
        // Call site argument attribute "nofree".
        getOrCreateAAFor<AANoFree>(CBArgPos);
      }
      return true;
    };
  
    auto &OpcodeInstMap = InfoCache.getOpcodeInstMapForFunction(F);
    bool Success;
    Success = checkForAllInstructionsImpl(
        nullptr, OpcodeInstMap, CallSitePred, nullptr, nullptr,
        {(unsigned)Instruction::Invoke, (unsigned)Instruction::CallBr,
         (unsigned)Instruction::Call});
    (void)Success;
    assert(Success && "Expected the check call to be successful!");
  
    auto LoadStorePred = [&](Instruction &I) -> bool {
      if (isa<LoadInst>(I))
        getOrCreateAAFor<AAAlign>(
            IRPosition::value(*cast<LoadInst>(I).getPointerOperand()));
      else
        getOrCreateAAFor<AAAlign>(
            IRPosition::value(*cast<StoreInst>(I).getPointerOperand()));
      return true;
    };
    Success = checkForAllInstructionsImpl(
        nullptr, OpcodeInstMap, LoadStorePred, nullptr, nullptr,
        {(unsigned)Instruction::Load, (unsigned)Instruction::Store});
    (void)Success;
    assert(Success && "Expected the check call to be successful!");
  }
  
  /// Helpers to ease debugging through output streams and print calls.
  ///
  ///{
  raw_ostream &llvm::operator<<(raw_ostream &OS, ChangeStatus S) {
    return OS << (S == ChangeStatus::CHANGED ? "changed" : "unchanged");
  }
  
  raw_ostream &llvm::operator<<(raw_ostream &OS, IRPosition::Kind AP) {
    switch (AP) {
    case IRPosition::IRP_INVALID:
      return OS << "inv";
    case IRPosition::IRP_FLOAT:
      return OS << "flt";
    case IRPosition::IRP_RETURNED:
      return OS << "fn_ret";
    case IRPosition::IRP_CALL_SITE_RETURNED:
      return OS << "cs_ret";
    case IRPosition::IRP_FUNCTION:
      return OS << "fn";
    case IRPosition::IRP_CALL_SITE:
      return OS << "cs";
    case IRPosition::IRP_ARGUMENT:
      return OS << "arg";
    case IRPosition::IRP_CALL_SITE_ARGUMENT:
      return OS << "cs_arg";
    }
    llvm_unreachable("Unknown attribute position!");
  }
  
  raw_ostream &llvm::operator<<(raw_ostream &OS, const IRPosition &Pos) {
    const Value &AV = Pos.getAssociatedValue();
    return OS << "{" << Pos.getPositionKind() << ":" << AV.getName() << " ["
              << Pos.getAnchorValue().getName() << "@" << Pos.getCallSiteArgNo()
              << "]}";
  }
  
  raw_ostream &llvm::operator<<(raw_ostream &OS, const IntegerRangeState &S) {
    OS << "range-state(" << S.getBitWidth() << ")<";
    S.getKnown().print(OS);
    OS << " / ";
    S.getAssumed().print(OS);
    OS << ">";
  
    return OS << static_cast<const AbstractState &>(S);
  }
  
  raw_ostream &llvm::operator<<(raw_ostream &OS, const AbstractState &S) {
    return OS << (!S.isValidState() ? "top" : (S.isAtFixpoint() ? "fix" : ""));
  }
  
  raw_ostream &llvm::operator<<(raw_ostream &OS, const AbstractAttribute &AA) {
    AA.print(OS);
    return OS;
  }
  
  raw_ostream &llvm::operator<<(raw_ostream &OS,
                                const PotentialConstantIntValuesState &S) {
    OS << "set-state(< {";
    if (!S.isValidState())
      OS << "full-set";
    else {
      for (auto &it : S.getAssumedSet())
        OS << it << ", ";
      if (S.undefIsContained())
        OS << "undef ";
    }
    OS << "} >)";
  
    return OS;
  }
  
  void AbstractAttribute::print(raw_ostream &OS) const {
    OS << "[";
    OS << getName();
    OS << "] for CtxI ";
  
    if (auto *I = getCtxI()) {
      OS << "'";
      I->print(OS);
      OS << "'";
    } else
      OS << "<<null inst>>";
  
    OS << " at position " << getIRPosition() << " with state " << getAsStr()
       << '\n';
  }
  
  void AbstractAttribute::printWithDeps(raw_ostream &OS) const {
    print(OS);
  
    for (const auto &DepAA : Deps) {
      auto *AA = DepAA.getPointer();
      OS << "  updates ";
      AA->print(OS);
    }
  
    OS << '\n';
  }
  ///}
  
  /// ----------------------------------------------------------------------------
  ///                       Pass (Manager) Boilerplate
  /// ----------------------------------------------------------------------------
  
  static bool runAttributorOnFunctions(InformationCache &InfoCache,
                                       SetVector<Function *> &Functions,
                                       AnalysisGetter &AG,
                                       CallGraphUpdater &CGUpdater,
                                       bool DeleteFns) {
    if (Functions.empty())
      return false;
  
    LLVM_DEBUG(dbgs() << "[Attributor] Run on module with " << Functions.size()
                      << " functions.\n");
  
    // Create an Attributor and initially empty information cache that is filled
    // while we identify default attribute opportunities.
    Attributor A(Functions, InfoCache, CGUpdater, /* Allowed */ nullptr,
                 DeleteFns);
  
    // Create shallow wrappers for all functions that are not IPO amendable
    if (AllowShallowWrappers)
      for (Function *F : Functions)
        if (!A.isFunctionIPOAmendable(*F))
          Attributor::createShallowWrapper(*F);
  
    // Internalize non-exact functions
    // TODO: for now we eagerly internalize functions without calculating the
    //       cost, we need a cost interface to determine whether internalizing
    //       a function is "benefitial"
    if (AllowDeepWrapper) {
      unsigned FunSize = Functions.size();
      for (unsigned u = 0; u < FunSize; u++) {
        Function *F = Functions[u];
        if (!F->isDeclaration() && !F->isDefinitionExact() && F->getNumUses() &&
            !GlobalValue::isInterposableLinkage(F->getLinkage())) {
          Function *NewF = internalizeFunction(*F);
          Functions.insert(NewF);
  
          // Update call graph
          CGUpdater.replaceFunctionWith(*F, *NewF);
          for (const Use &U : NewF->uses())
            if (CallBase *CB = dyn_cast<CallBase>(U.getUser())) {
              auto *CallerF = CB->getCaller();
              CGUpdater.reanalyzeFunction(*CallerF);
            }
        }
      }
    }
  
    for (Function *F : Functions) {
      if (F->hasExactDefinition())
        NumFnWithExactDefinition++;
      else
        NumFnWithoutExactDefinition++;
  
      // We look at internal functions only on-demand but if any use is not a
      // direct call or outside the current set of analyzed functions, we have
      // to do it eagerly.
      if (F->hasLocalLinkage()) {
        if (llvm::all_of(F->uses(), [&Functions](const Use &U) {
              const auto *CB = dyn_cast<CallBase>(U.getUser());
              return CB && CB->isCallee(&U) &&
                     Functions.count(const_cast<Function *>(CB->getCaller()));
            }))
          continue;
      }
  
      // Populate the Attributor with abstract attribute opportunities in the
      // function and the information cache with IR information.
      A.identifyDefaultAbstractAttributes(*F);
    }
  
    ChangeStatus Changed = A.run();
  
    LLVM_DEBUG(dbgs() << "[Attributor] Done with " << Functions.size()
                      << " functions, result: " << Changed << ".\n");
    return Changed == ChangeStatus::CHANGED;
  }
  
  void AADepGraph::viewGraph() { llvm::ViewGraph(this, "Dependency Graph"); }
  
  void AADepGraph::dumpGraph() {
    static std::atomic<int> CallTimes;
    std::string Prefix;
  
    if (!DepGraphDotFileNamePrefix.empty())
      Prefix = DepGraphDotFileNamePrefix;
    else
      Prefix = "dep_graph";
    std::string Filename =
        Prefix + "_" + std::to_string(CallTimes.load()) + ".dot";
  
    outs() << "Dependency graph dump to " << Filename << ".\n";
  
    std::error_code EC;
  
    raw_fd_ostream File(Filename, EC, sys::fs::OF_Text);
    if (!EC)
      llvm::WriteGraph(File, this);
  
    CallTimes++;
  }
  
  void AADepGraph::print() {
    for (auto DepAA : SyntheticRoot.Deps)
      cast<AbstractAttribute>(DepAA.getPointer())->printWithDeps(outs());
  }
  
  PreservedAnalyses AttributorPass::run(Module &M, ModuleAnalysisManager &AM) {
    FunctionAnalysisManager &FAM =
        AM.getResult<FunctionAnalysisManagerModuleProxy>(M).getManager();
    AnalysisGetter AG(FAM);
  
    SetVector<Function *> Functions;
    for (Function &F : M)
      Functions.insert(&F);
  
    CallGraphUpdater CGUpdater;
    BumpPtrAllocator Allocator;
    InformationCache InfoCache(M, AG, Allocator, /* CGSCC */ nullptr);
    if (runAttributorOnFunctions(InfoCache, Functions, AG, CGUpdater,
                                 /* DeleteFns */ true)) {
      // FIXME: Think about passes we will preserve and add them here.
      return PreservedAnalyses::none();
    }
    return PreservedAnalyses::all();
  }
  
  PreservedAnalyses AttributorCGSCCPass::run(LazyCallGraph::SCC &C,
                                             CGSCCAnalysisManager &AM,
                                             LazyCallGraph &CG,
                                             CGSCCUpdateResult &UR) {
    FunctionAnalysisManager &FAM =
        AM.getResult<FunctionAnalysisManagerCGSCCProxy>(C, CG).getManager();
    AnalysisGetter AG(FAM);
  
    SetVector<Function *> Functions;
    for (LazyCallGraph::Node &N : C)
      Functions.insert(&N.getFunction());
  
    if (Functions.empty())
      return PreservedAnalyses::all();
  
    Module &M = *Functions.back()->getParent();
    CallGraphUpdater CGUpdater;
    CGUpdater.initialize(CG, C, AM, UR);
    BumpPtrAllocator Allocator;
    InformationCache InfoCache(M, AG, Allocator, /* CGSCC */ &Functions);
    if (runAttributorOnFunctions(InfoCache, Functions, AG, CGUpdater,
                                 /* DeleteFns */ false)) {
      // FIXME: Think about passes we will preserve and add them here.
      PreservedAnalyses PA;
      PA.preserve<FunctionAnalysisManagerCGSCCProxy>();
      return PA;
    }
    return PreservedAnalyses::all();
  }
  
  namespace llvm {
  
  template <> struct GraphTraits<AADepGraphNode *> {
    using NodeRef = AADepGraphNode *;
    using DepTy = PointerIntPair<AADepGraphNode *, 1>;
    using EdgeRef = PointerIntPair<AADepGraphNode *, 1>;
  
    static NodeRef getEntryNode(AADepGraphNode *DGN) { return DGN; }
    static NodeRef DepGetVal(DepTy &DT) { return DT.getPointer(); }
  
    using ChildIteratorType =
        mapped_iterator<TinyPtrVector<DepTy>::iterator, decltype(&DepGetVal)>;
    using ChildEdgeIteratorType = TinyPtrVector<DepTy>::iterator;
  
    static ChildIteratorType child_begin(NodeRef N) { return N->child_begin(); }
  
    static ChildIteratorType child_end(NodeRef N) { return N->child_end(); }
  };
  
  template <>
  struct GraphTraits<AADepGraph *> : public GraphTraits<AADepGraphNode *> {
    static NodeRef getEntryNode(AADepGraph *DG) { return DG->GetEntryNode(); }
  
    using nodes_iterator =
        mapped_iterator<TinyPtrVector<DepTy>::iterator, decltype(&DepGetVal)>;
  
    static nodes_iterator nodes_begin(AADepGraph *DG) { return DG->begin(); }
  
    static nodes_iterator nodes_end(AADepGraph *DG) { return DG->end(); }
  };
  
  template <> struct DOTGraphTraits<AADepGraph *> : public DefaultDOTGraphTraits {
    DOTGraphTraits(bool isSimple = false) : DefaultDOTGraphTraits(isSimple) {}
  
    static std::string getNodeLabel(const AADepGraphNode *Node,
                                    const AADepGraph *DG) {
      std::string AAString;
      raw_string_ostream O(AAString);
      Node->print(O);
      return AAString;
    }
  };
  
  } // end namespace llvm
  
  namespace {
  
  struct AttributorLegacyPass : public ModulePass {
    static char ID;
  
    AttributorLegacyPass() : ModulePass(ID) {
      initializeAttributorLegacyPassPass(*PassRegistry::getPassRegistry());
    }
  
    bool runOnModule(Module &M) override {
      if (skipModule(M))
        return false;
  
      AnalysisGetter AG;
      SetVector<Function *> Functions;
      for (Function &F : M)
        Functions.insert(&F);
  
      CallGraphUpdater CGUpdater;
      BumpPtrAllocator Allocator;
      InformationCache InfoCache(M, AG, Allocator, /* CGSCC */ nullptr);
      return runAttributorOnFunctions(InfoCache, Functions, AG, CGUpdater,
                                      /* DeleteFns*/ true);
    }
  
    void getAnalysisUsage(AnalysisUsage &AU) const override {
      // FIXME: Think about passes we will preserve and add them here.
      AU.addRequired<TargetLibraryInfoWrapperPass>();
    }
  };
  
  struct AttributorCGSCCLegacyPass : public CallGraphSCCPass {
    static char ID;
  
    AttributorCGSCCLegacyPass() : CallGraphSCCPass(ID) {
      initializeAttributorCGSCCLegacyPassPass(*PassRegistry::getPassRegistry());
    }
  
    bool runOnSCC(CallGraphSCC &SCC) override {
      if (skipSCC(SCC))
        return false;
  
      SetVector<Function *> Functions;
      for (CallGraphNode *CGN : SCC)
        if (Function *Fn = CGN->getFunction())
          if (!Fn->isDeclaration())
            Functions.insert(Fn);
  
      if (Functions.empty())
        return false;
  
      AnalysisGetter AG;
      CallGraph &CG = const_cast<CallGraph &>(SCC.getCallGraph());
      CallGraphUpdater CGUpdater;
      CGUpdater.initialize(CG, SCC);
      Module &M = *Functions.back()->getParent();
      BumpPtrAllocator Allocator;
      InformationCache InfoCache(M, AG, Allocator, /* CGSCC */ &Functions);
      return runAttributorOnFunctions(InfoCache, Functions, AG, CGUpdater,
                                      /* DeleteFns */ false);
    }
  
    void getAnalysisUsage(AnalysisUsage &AU) const override {
      // FIXME: Think about passes we will preserve and add them here.
      AU.addRequired<TargetLibraryInfoWrapperPass>();
      CallGraphSCCPass::getAnalysisUsage(AU);
    }
  };
  
  } // end anonymous namespace
  
  Pass *llvm::createAttributorLegacyPass() { return new AttributorLegacyPass(); }
  Pass *llvm::createAttributorCGSCCLegacyPass() {
    return new AttributorCGSCCLegacyPass();
  }
  
  char AttributorLegacyPass::ID = 0;
  char AttributorCGSCCLegacyPass::ID = 0;
  
  INITIALIZE_PASS_BEGIN(AttributorLegacyPass, "attributor",
                        "Deduce and propagate attributes", false, false)
  INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfoWrapperPass)
  INITIALIZE_PASS_END(AttributorLegacyPass, "attributor",
                      "Deduce and propagate attributes", false, false)
  INITIALIZE_PASS_BEGIN(AttributorCGSCCLegacyPass, "attributor-cgscc",
                        "Deduce and propagate attributes (CGSCC pass)", false,
                        false)
  INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfoWrapperPass)
  INITIALIZE_PASS_DEPENDENCY(CallGraphWrapperPass)
  INITIALIZE_PASS_END(AttributorCGSCCLegacyPass, "attributor-cgscc",
                      "Deduce and propagate attributes (CGSCC pass)", false,
                      false)
  