text: //===- SROA.cpp - Scalar Replacement Of Aggregates ------------------------===//
  //
  //                     The LLVM Compiler Infrastructure
  //
  // This file is distributed under the University of Illinois Open Source
  // License. See LICENSE.TXT for details.
  //
  //===----------------------------------------------------------------------===//
  /// \file
  /// This transformation implements the well known scalar replacement of
  /// aggregates transformation. It tries to identify promotable elements of an
  /// aggregate alloca, and promote them to registers. It will also try to
  /// convert uses of an element (or set of elements) of an alloca into a vector
  /// or bitfield-style integer scalar if appropriate.
  ///
  /// It works to do this with minimal slicing of the alloca so that regions
  /// which are merely transferred in and out of external memory remain unchanged
  /// and are not decomposed to scalar code.
  ///
  /// Because this also performs alloca promotion, it can be thought of as also
  /// serving the purpose of SSA formation. The algorithm iterates on the
  /// function until all opportunities for promotion have been realized.
  ///
  //===----------------------------------------------------------------------===//
  
  #include "llvm/Transforms/Scalar/SROA.h"
  #include "llvm/ADT/APInt.h"
  #include "llvm/ADT/ArrayRef.h"
  #include "llvm/ADT/DenseMap.h"
  #include "llvm/ADT/PointerIntPair.h"
  #include "llvm/ADT/STLExtras.h"
  #include "llvm/ADT/SetVector.h"
  #include "llvm/ADT/SmallBitVector.h"
  #include "llvm/ADT/SmallPtrSet.h"
  #include "llvm/ADT/SmallVector.h"
  #include "llvm/ADT/Statistic.h"
  #include "llvm/ADT/StringRef.h"
  #include "llvm/ADT/Twine.h"
  #include "llvm/ADT/iterator.h"
  #include "llvm/ADT/iterator_range.h"
  #include "llvm/Analysis/AssumptionCache.h"
  #include "llvm/Analysis/GlobalsModRef.h"
  #include "llvm/Analysis/Loads.h"
  #include "llvm/Analysis/PtrUseVisitor.h"
  #include "llvm/Transforms/Utils/Local.h"
  #include "llvm/Config/llvm-config.h"
  #include "llvm/IR/BasicBlock.h"
  #include "llvm/IR/Constant.h"
  #include "llvm/IR/ConstantFolder.h"
  #include "llvm/IR/Constants.h"
  #include "llvm/IR/DIBuilder.h"
  #include "llvm/IR/DataLayout.h"
  #include "llvm/IR/DebugInfoMetadata.h"
  #include "llvm/IR/DerivedTypes.h"
  #include "llvm/IR/Dominators.h"
  #include "llvm/IR/Function.h"
  #include "llvm/IR/GetElementPtrTypeIterator.h"
  #include "llvm/IR/GlobalAlias.h"
  #include "llvm/IR/IRBuilder.h"
  #include "llvm/IR/InstVisitor.h"
  #include "llvm/IR/InstrTypes.h"
  #include "llvm/IR/Instruction.h"
  #include "llvm/IR/Instructions.h"
  #include "llvm/IR/IntrinsicInst.h"
  #include "llvm/IR/Intrinsics.h"
  #include "llvm/IR/LLVMContext.h"
  #include "llvm/IR/Metadata.h"
  #include "llvm/IR/Module.h"
  #include "llvm/IR/Operator.h"
  #include "llvm/IR/PassManager.h"
  #include "llvm/IR/Type.h"
  #include "llvm/IR/Use.h"
  #include "llvm/IR/User.h"
  #include "llvm/IR/Value.h"
  #include "llvm/Pass.h"
  #include "llvm/Support/Casting.h"
  #include "llvm/Support/CommandLine.h"
  #include "llvm/Support/Compiler.h"
  #include "llvm/Support/Debug.h"
  #include "llvm/Support/ErrorHandling.h"
  #include "llvm/Support/MathExtras.h"
  #include "llvm/Support/raw_ostream.h"
  #include "llvm/Transforms/Scalar.h"
  #include "llvm/Transforms/Utils/PromoteMemToReg.h"
  #include <algorithm>
  #include <cassert>
  #include <chrono>
  #include <cstddef>
  #include <cstdint>
  #include <cstring>
  #include <iterator>
  #include <string>
  #include <tuple>
  #include <utility>
  #include <vector>
  
  #ifndef NDEBUG
  // We only use this for a debug check.
  #include <random>
  #endif
  
  using namespace llvm;
  using namespace llvm::sroa;
  
  #define DEBUG_TYPE "sroa"
  
  STATISTIC(NumAllocasAnalyzed, "Number of allocas analyzed for replacement");
  STATISTIC(NumAllocaPartitions, "Number of alloca partitions formed");
  STATISTIC(MaxPartitionsPerAlloca, "Maximum number of partitions per alloca");
  STATISTIC(NumAllocaPartitionUses, "Number of alloca partition uses rewritten");
  STATISTIC(MaxUsesPerAllocaPartition, "Maximum number of uses of a partition");
  STATISTIC(NumNewAllocas, "Number of new, smaller allocas introduced");
  STATISTIC(NumPromoted, "Number of allocas promoted to SSA values");
  STATISTIC(NumLoadsSpeculated, "Number of loads speculated to allow promotion");
  STATISTIC(NumDeleted, "Number of instructions deleted");
  STATISTIC(NumVectorized, "Number of vectorized aggregates");
  
  /// Hidden option to enable randomly shuffling the slices to help uncover
  /// instability in their order.
  static cl::opt<bool> SROARandomShuffleSlices("sroa-random-shuffle-slices",
                                               cl::init(false), cl::Hidden);
  
  /// Hidden option to experiment with completely strict handling of inbounds
  /// GEPs.
  static cl::opt<bool> SROAStrictInbounds("sroa-strict-inbounds", cl::init(false),
                                          cl::Hidden);
  
  namespace {
  
  /// A custom IRBuilder inserter which prefixes all names, but only in
  /// Assert builds.
  class IRBuilderPrefixedInserter : public IRBuilderDefaultInserter {
    std::string Prefix;
  
    const Twine getNameWithPrefix(const Twine &Name) const {
      return Name.isTriviallyEmpty() ? Name : Prefix + Name;
    }
  
  public:
    void SetNamePrefix(const Twine &P) { Prefix = P.str(); }
  
  protected:
    void InsertHelper(Instruction *I, const Twine &Name, BasicBlock *BB,
                      BasicBlock::iterator InsertPt) const {
      IRBuilderDefaultInserter::InsertHelper(I, getNameWithPrefix(Name), BB,
                                             InsertPt);
    }
  };
  
  /// Provide a type for IRBuilder that drops names in release builds.
  using IRBuilderTy = IRBuilder<ConstantFolder, IRBuilderPrefixedInserter>;
  
  /// A used slice of an alloca.
  ///
  /// This structure represents a slice of an alloca used by some instruction. It
  /// stores both the begin and end offsets of this use, a pointer to the use
  /// itself, and a flag indicating whether we can classify the use as splittable
  /// or not when forming partitions of the alloca.
  class Slice {
    /// The beginning offset of the range.
    uint64_t BeginOffset = 0;
  
    /// The ending offset, not included in the range.
    uint64_t EndOffset = 0;
  
    /// Storage for both the use of this slice and whether it can be
    /// split.
    PointerIntPair<Use *, 1, bool> UseAndIsSplittable;
  
  public:
    Slice() = default;
  
    Slice(uint64_t BeginOffset, uint64_t EndOffset, Use *U, bool IsSplittable)
        : BeginOffset(BeginOffset), EndOffset(EndOffset),
          UseAndIsSplittable(U, IsSplittable) {}
  
    uint64_t beginOffset() const { return BeginOffset; }
    uint64_t endOffset() const { return EndOffset; }
  
    bool isSplittable() const { return UseAndIsSplittable.getInt(); }
    void makeUnsplittable() { UseAndIsSplittable.setInt(false); }
  
    Use *getUse() const { return UseAndIsSplittable.getPointer(); }
  
    bool isDead() const { return getUse() == nullptr; }
    void kill() { UseAndIsSplittable.setPointer(nullptr); }
  
    /// Support for ordering ranges.
    ///
    /// This provides an ordering over ranges such that start offsets are
    /// always increasing, and within equal start offsets, the end offsets are
    /// decreasing. Thus the spanning range comes first in a cluster with the
    /// same start position.
    bool operator<(const Slice &RHS) const {
      if (beginOffset() < RHS.beginOffset())
        return true;
      if (beginOffset() > RHS.beginOffset())
        return false;
      if (isSplittable() != RHS.isSplittable())
        return !isSplittable();
      if (endOffset() > RHS.endOffset())
        return true;
      return false;
    }
  
    /// Support comparison with a single offset to allow binary searches.
    friend LLVM_ATTRIBUTE_UNUSED bool operator<(const Slice &LHS,
                                                uint64_t RHSOffset) {
      return LHS.beginOffset() < RHSOffset;
    }
    friend LLVM_ATTRIBUTE_UNUSED bool operator<(uint64_t LHSOffset,
                                                const Slice &RHS) {
      return LHSOffset < RHS.beginOffset();
    }
  
    bool operator==(const Slice &RHS) const {
      return isSplittable() == RHS.isSplittable() &&
             beginOffset() == RHS.beginOffset() && endOffset() == RHS.endOffset();
    }
    bool operator!=(const Slice &RHS) const { return !operator==(RHS); }
  };
  
  } // end anonymous namespace
  
  namespace llvm {
  
  template <typename T> struct isPodLike;
  template <> struct isPodLike<Slice> { static const bool value = true; };
  
  } // end namespace llvm
  
  /// Representation of the alloca slices.
  ///
  /// This class represents the slices of an alloca which are formed by its
  /// various uses. If a pointer escapes, we can't fully build a representation
  /// for the slices used and we reflect that in this structure. The uses are
  /// stored, sorted by increasing beginning offset and with unsplittable slices
  /// starting at a particular offset before splittable slices.
  class llvm::sroa::AllocaSlices {
  public:
    /// Construct the slices of a particular alloca.
    AllocaSlices(const DataLayout &DL, AllocaInst &AI);
  
    /// Test whether a pointer to the allocation escapes our analysis.
    ///
    /// If this is true, the slices are never fully built and should be
    /// ignored.
    bool isEscaped() const { return PointerEscapingInstr; }
  
    /// Support for iterating over the slices.
    /// @{
    using iterator = SmallVectorImpl<Slice>::iterator;
    using range = iterator_range<iterator>;
  
    iterator begin() { return Slices.begin(); }
    iterator end() { return Slices.end(); }
  
    using const_iterator = SmallVectorImpl<Slice>::const_iterator;
    using const_range = iterator_range<const_iterator>;
  
    const_iterator begin() const { return Slices.begin(); }
    const_iterator end() const { return Slices.end(); }
    /// @}
  
    /// Erase a range of slices.
    void erase(iterator Start, iterator Stop) { Slices.erase(Start, Stop); }
  
    /// Insert new slices for this alloca.
    ///
    /// This moves the slices into the alloca's slices collection, and re-sorts
    /// everything so that the usual ordering properties of the alloca's slices
    /// hold.
    void insert(ArrayRef<Slice> NewSlices) {
      int OldSize = Slices.size();
      Slices.append(NewSlices.begin(), NewSlices.end());
      auto SliceI = Slices.begin() + OldSize;
      llvm::sort(SliceI, Slices.end());
      std::inplace_merge(Slices.begin(), SliceI, Slices.end());
    }
  
    // Forward declare the iterator and range accessor for walking the
    // partitions.
    class partition_iterator;
    iterator_range<partition_iterator> partitions();
  
    /// Access the dead users for this alloca.
    ArrayRef<Instruction *> getDeadUsers() const { return DeadUsers; }
  
    /// Access the dead operands referring to this alloca.
    ///
    /// These are operands which have cannot actually be used to refer to the
    /// alloca as they are outside its range and the user doesn't correct for
    /// that. These mostly consist of PHI node inputs and the like which we just
    /// need to replace with undef.
    ArrayRef<Use *> getDeadOperands() const { return DeadOperands; }
  
  #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
    void print(raw_ostream &OS, const_iterator I, StringRef Indent = "  ") const;
    void printSlice(raw_ostream &OS, const_iterator I,
                    StringRef Indent = "  ") const;
    void printUse(raw_ostream &OS, const_iterator I,
                  StringRef Indent = "  ") const;
    void print(raw_ostream &OS) const;
    void dump(const_iterator I) const;
    void dump() const;
  #endif
  
  private:
    template <typename DerivedT, typename RetT = void> class BuilderBase;
    class SliceBuilder;
  
    friend class AllocaSlices::SliceBuilder;
  
  #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
    /// Handle to alloca instruction to simplify method interfaces.
    AllocaInst &AI;
  #endif
  
    /// The instruction responsible for this alloca not having a known set
    /// of slices.
    ///
    /// When an instruction (potentially) escapes the pointer to the alloca, we
    /// store a pointer to that here and abort trying to form slices of the
    /// alloca. This will be null if the alloca slices are analyzed successfully.
    Instruction *PointerEscapingInstr;
  
    /// The slices of the alloca.
    ///
    /// We store a vector of the slices formed by uses of the alloca here. This
    /// vector is sorted by increasing begin offset, and then the unsplittable
    /// slices before the splittable ones. See the Slice inner class for more
    /// details.
    SmallVector<Slice, 8> Slices;
  
    /// Instructions which will become dead if we rewrite the alloca.
    ///
    /// Note that these are not separated by slice. This is because we expect an
    /// alloca to be completely rewritten or not rewritten at all. If rewritten,
    /// all these instructions can simply be removed and replaced with undef as
    /// they come from outside of the allocated space.
    SmallVector<Instruction *, 8> DeadUsers;
  
    /// Operands which will become dead if we rewrite the alloca.
    ///
    /// These are operands that in their particular use can be replaced with
    /// undef when we rewrite the alloca. These show up in out-of-bounds inputs
    /// to PHI nodes and the like. They aren't entirely dead (there might be
    /// a GEP back into the bounds using it elsewhere) and nor is the PHI, but we
    /// want to swap this particular input for undef to simplify the use lists of
    /// the alloca.
    SmallVector<Use *, 8> DeadOperands;
  };
  
  /// A partition of the slices.
  ///
  /// An ephemeral representation for a range of slices which can be viewed as
  /// a partition of the alloca. This range represents a span of the alloca's
  /// memory which cannot be split, and provides access to all of the slices
  /// overlapping some part of the partition.
  ///
  /// Objects of this type are produced by traversing the alloca's slices, but
  /// are only ephemeral and not persistent.
  class llvm::sroa::Partition {
  private:
    friend class AllocaSlices;
    friend class AllocaSlices::partition_iterator;
  
    using iterator = AllocaSlices::iterator;
  
    /// The beginning and ending offsets of the alloca for this
    /// partition.
    uint64_t BeginOffset, EndOffset;
  
    /// The start and end iterators of this partition.
    iterator SI, SJ;
  
    /// A collection of split slice tails overlapping the partition.
    SmallVector<Slice *, 4> SplitTails;
  
    /// Raw constructor builds an empty partition starting and ending at
    /// the given iterator.
    Partition(iterator SI) : SI(SI), SJ(SI) {}
  
  public:
    /// The start offset of this partition.
    ///
    /// All of the contained slices start at or after this offset.
    uint64_t beginOffset() const { return BeginOffset; }
  
    /// The end offset of this partition.
    ///
    /// All of the contained slices end at or before this offset.
    uint64_t endOffset() const { return EndOffset; }
  
    /// The size of the partition.
    ///
    /// Note that this can never be zero.
    uint64_t size() const {
      assert(BeginOffset < EndOffset && "Partitions must span some bytes!");
      return EndOffset - BeginOffset;
    }
  
    /// Test whether this partition contains no slices, and merely spans
    /// a region occupied by split slices.
    bool empty() const { return SI == SJ; }
  
    /// \name Iterate slices that start within the partition.
    /// These may be splittable or unsplittable. They have a begin offset >= the
    /// partition begin offset.
    /// @{
    // FIXME: We should probably define a "concat_iterator" helper and use that
    // to stitch together pointee_iterators over the split tails and the
    // contiguous iterators of the partition. That would give a much nicer
    // interface here. We could then additionally expose filtered iterators for
    // split, unsplit, and unsplittable splices based on the usage patterns.
    iterator begin() const { return SI; }
    iterator end() const { return SJ; }
    /// @}
  
    /// Get the sequence of split slice tails.
    ///
    /// These tails are of slices which start before this partition but are
    /// split and overlap into the partition. We accumulate these while forming
    /// partitions.
    ArrayRef<Slice *> splitSliceTails() const { return SplitTails; }
  };
  
  /// An iterator over partitions of the alloca's slices.
  ///
  /// This iterator implements the core algorithm for partitioning the alloca's
  /// slices. It is a forward iterator as we don't support backtracking for
  /// efficiency reasons, and re-use a single storage area to maintain the
  /// current set of split slices.
  ///
  /// It is templated on the slice iterator type to use so that it can operate
  /// with either const or non-const slice iterators.
  class AllocaSlices::partition_iterator
      : public iterator_facade_base<partition_iterator, std::forward_iterator_tag,
                                    Partition> {
    friend class AllocaSlices;
  
    /// Most of the state for walking the partitions is held in a class
    /// with a nice interface for examining them.
    Partition P;
  
    /// We need to keep the end of the slices to know when to stop.
    AllocaSlices::iterator SE;
  
    /// We also need to keep track of the maximum split end offset seen.
    /// FIXME: Do we really?
    uint64_t MaxSplitSliceEndOffset = 0;
  
    /// Sets the partition to be empty at given iterator, and sets the
    /// end iterator.
    partition_iterator(AllocaSlices::iterator SI, AllocaSlices::iterator SE)
        : P(SI), SE(SE) {
      // If not already at the end, advance our state to form the initial
      // partition.
      if (SI != SE)
        advance();
    }
  
    /// Advance the iterator to the next partition.
    ///
    /// Requires that the iterator not be at the end of the slices.
    void advance() {
      assert((P.SI != SE || !P.SplitTails.empty()) &&
             "Cannot advance past the end of the slices!");
  
      // Clear out any split uses which have ended.
      if (!P.SplitTails.empty()) {
        if (P.EndOffset >= MaxSplitSliceEndOffset) {
          // If we've finished all splits, this is easy.
          P.SplitTails.clear();
          MaxSplitSliceEndOffset = 0;
        } else {
          // Remove the uses which have ended in the prior partition. This
          // cannot change the max split slice end because we just checked that
          // the prior partition ended prior to that max.
          P.SplitTails.erase(llvm::remove_if(P.SplitTails,
                                             [&](Slice *S) {
                                               return S->endOffset() <=
                                                      P.EndOffset;
                                             }),
                             P.SplitTails.end());
          assert(llvm::any_of(P.SplitTails,
                              [&](Slice *S) {
                                return S->endOffset() == MaxSplitSliceEndOffset;
                              }) &&
                 "Could not find the current max split slice offset!");
          assert(llvm::all_of(P.SplitTails,
                              [&](Slice *S) {
                                return S->endOffset() <= MaxSplitSliceEndOffset;
                              }) &&
                 "Max split slice end offset is not actually the max!");
        }
      }
  
      // If P.SI is already at the end, then we've cleared the split tail and
      // now have an end iterator.
      if (P.SI == SE) {
        assert(P.SplitTails.empty() && "Failed to clear the split slices!");
        return;
      }
  
      // If we had a non-empty partition previously, set up the state for
      // subsequent partitions.
      if (P.SI != P.SJ) {
        // Accumulate all the splittable slices which started in the old
        // partition into the split list.
        for (Slice &S : P)
          if (S.isSplittable() && S.endOffset() > P.EndOffset) {
            P.SplitTails.push_back(&S);
            MaxSplitSliceEndOffset =
                std::max(S.endOffset(), MaxSplitSliceEndOffset);
          }
  
        // Start from the end of the previous partition.
        P.SI = P.SJ;
  
        // If P.SI is now at the end, we at most have a tail of split slices.
        if (P.SI == SE) {
          P.BeginOffset = P.EndOffset;
          P.EndOffset = MaxSplitSliceEndOffset;
          return;
        }
  
        // If the we have split slices and the next slice is after a gap and is
        // not splittable immediately form an empty partition for the split
        // slices up until the next slice begins.
        if (!P.SplitTails.empty() && P.SI->beginOffset() != P.EndOffset &&
            !P.SI->isSplittable()) {
          P.BeginOffset = P.EndOffset;
          P.EndOffset = P.SI->beginOffset();
          return;
        }
      }
  
      // OK, we need to consume new slices. Set the end offset based on the
      // current slice, and step SJ past it. The beginning offset of the
      // partition is the beginning offset of the next slice unless we have
      // pre-existing split slices that are continuing, in which case we begin
      // at the prior end offset.
      P.BeginOffset = P.SplitTails.empty() ? P.SI->beginOffset() : P.EndOffset;
      P.EndOffset = P.SI->endOffset();
      ++P.SJ;
  
      // There are two strategies to form a partition based on whether the
      // partition starts with an unsplittable slice or a splittable slice.
      if (!P.SI->isSplittable()) {
        // When we're forming an unsplittable region, it must always start at
        // the first slice and will extend through its end.
        assert(P.BeginOffset == P.SI->beginOffset());
  
        // Form a partition including all of the overlapping slices with this
        // unsplittable slice.
        while (P.SJ != SE && P.SJ->beginOffset() < P.EndOffset) {
          if (!P.SJ->isSplittable())
            P.EndOffset = std::max(P.EndOffset, P.SJ->endOffset());
          ++P.SJ;
        }
  
        // We have a partition across a set of overlapping unsplittable
        // partitions.
        return;
      }
  
      // If we're starting with a splittable slice, then we need to form
      // a synthetic partition spanning it and any other overlapping splittable
      // splices.
      assert(P.SI->isSplittable() && "Forming a splittable partition!");
  
      // Collect all of the overlapping splittable slices.
      while (P.SJ != SE && P.SJ->beginOffset() < P.EndOffset &&
             P.SJ->isSplittable()) {
        P.EndOffset = std::max(P.EndOffset, P.SJ->endOffset());
        ++P.SJ;
      }
  
      // Back upiP.EndOffset if we ended the span early when encountering an
      // unsplittable slice. This synthesizes the early end offset of
      // a partition spanning only splittable slices.
      if (P.SJ != SE && P.SJ->beginOffset() < P.EndOffset) {
        assert(!P.SJ->isSplittable());
        P.EndOffset = P.SJ->beginOffset();
      }
    }
  
  public:
    bool operator==(const partition_iterator &RHS) const {
      assert(SE == RHS.SE &&
             "End iterators don't match between compared partition iterators!");
  
      // The observed positions of partitions is marked by the P.SI iterator and
      // the emptiness of the split slices. The latter is only relevant when
      // P.SI == SE, as the end iterator will additionally have an empty split
      // slices list, but the prior may have the same P.SI and a tail of split
      // slices.
      if (P.SI == RHS.P.SI && P.SplitTails.empty() == RHS.P.SplitTails.empty()) {
        assert(P.SJ == RHS.P.SJ &&
               "Same set of slices formed two different sized partitions!");
        assert(P.SplitTails.size() == RHS.P.SplitTails.size() &&
               "Same slice position with differently sized non-empty split "
               "slice tails!");
        return true;
      }
      return false;
    }
  
    partition_iterator &operator++() {
      advance();
      return *this;
    }
  
    Partition &operator*() { return P; }
  };
  
  /// A forward range over the partitions of the alloca's slices.
  ///
  /// This accesses an iterator range over the partitions of the alloca's
  /// slices. It computes these partitions on the fly based on the overlapping
  /// offsets of the slices and the ability to split them. It will visit "empty"
  /// partitions to cover regions of the alloca only accessed via split
  /// slices.
  iterator_range<AllocaSlices::partition_iterator> AllocaSlices::partitions() {
    return make_range(partition_iterator(begin(), end()),
                      partition_iterator(end(), end()));
  }
  
  static Value *foldSelectInst(SelectInst &SI) {
    // If the condition being selected on is a constant or the same value is
    // being selected between, fold the select. Yes this does (rarely) happen
    // early on.
    if (ConstantInt *CI = dyn_cast<ConstantInt>(SI.getCondition()))
      return SI.getOperand(1 + CI->isZero());
    if (SI.getOperand(1) == SI.getOperand(2))
      return SI.getOperand(1);
  
    return nullptr;
  }
  
  /// A helper that folds a PHI node or a select.
  static Value *foldPHINodeOrSelectInst(Instruction &I) {
    if (PHINode *PN = dyn_cast<PHINode>(&I)) {
      // If PN merges together the same value, return that value.
      return PN->hasConstantValue();
    }
    return foldSelectInst(cast<SelectInst>(I));
  }
  
  /// Builder for the alloca slices.
  ///
  /// This class builds a set of alloca slices by recursively visiting the uses
  /// of an alloca and making a slice for each load and store at each offset.
  class AllocaSlices::SliceBuilder : public PtrUseVisitor<SliceBuilder> {
    friend class PtrUseVisitor<SliceBuilder>;
    friend class InstVisitor<SliceBuilder>;
  
    using Base = PtrUseVisitor<SliceBuilder>;
  
    const uint64_t AllocSize;
    AllocaSlices &AS;
  
    SmallDenseMap<Instruction *, unsigned> MemTransferSliceMap;
    SmallDenseMap<Instruction *, uint64_t> PHIOrSelectSizes;
  
    /// Set to de-duplicate dead instructions found in the use walk.
    SmallPtrSet<Instruction *, 4> VisitedDeadInsts;
  
  public:
    SliceBuilder(const DataLayout &DL, AllocaInst &AI, AllocaSlices &AS)
        : PtrUseVisitor<SliceBuilder>(DL),
          AllocSize(DL.getTypeAllocSize(AI.getAllocatedType())), AS(AS) {}
  
  private:
    void markAsDead(Instruction &I) {
      if (VisitedDeadInsts.insert(&I).second)
        AS.DeadUsers.push_back(&I);
    }
  
    void insertUse(Instruction &I, const APInt &Offset, uint64_t Size,
                   bool IsSplittable = false) {
      // Completely skip uses which have a zero size or start either before or
      // past the end of the allocation.
      if (Size == 0 || Offset.uge(AllocSize)) {
        LLVM_DEBUG(dbgs() << "WARNING: Ignoring " << Size << " byte use @"
                          << Offset
                          << " which has zero size or starts outside of the "
                          << AllocSize << " byte alloca:\n"
                          << "    alloca: " << AS.AI << "\n"
                          << "       use: " << I << "\n");
        return markAsDead(I);
      }
  
      uint64_t BeginOffset = Offset.getZExtValue();
      uint64_t EndOffset = BeginOffset + Size;
  
      // Clamp the end offset to the end of the allocation. Note that this is
      // formulated to handle even the case where "BeginOffset + Size" overflows.
      // This may appear superficially to be something we could ignore entirely,
      // but that is not so! There may be widened loads or PHI-node uses where
      // some instructions are dead but not others. We can't completely ignore
      // them, and so have to record at least the information here.
      assert(AllocSize >= BeginOffset); // Established above.
      if (Size > AllocSize - BeginOffset) {
        LLVM_DEBUG(dbgs() << "WARNING: Clamping a " << Size << " byte use @"
                          << Offset << " to remain within the " << AllocSize
                          << " byte alloca:\n"
                          << "    alloca: " << AS.AI << "\n"
                          << "       use: " << I << "\n");
        EndOffset = AllocSize;
      }
  
      AS.Slices.push_back(Slice(BeginOffset, EndOffset, U, IsSplittable));
    }
  
    void visitBitCastInst(BitCastInst &BC) {
      if (BC.use_empty())
        return markAsDead(BC);
  
      return Base::visitBitCastInst(BC);
    }
  
    void visitGetElementPtrInst(GetElementPtrInst &GEPI) {
      if (GEPI.use_empty())
        return markAsDead(GEPI);
  
      if (SROAStrictInbounds && GEPI.isInBounds()) {
        // FIXME: This is a manually un-factored variant of the basic code inside
        // of GEPs with checking of the inbounds invariant specified in the
        // langref in a very strict sense. If we ever want to enable
        // SROAStrictInbounds, this code should be factored cleanly into
        // PtrUseVisitor, but it is easier to experiment with SROAStrictInbounds
        // by writing out the code here where we have the underlying allocation
        // size readily available.
        APInt GEPOffset = Offset;
        const DataLayout &DL = GEPI.getModule()->getDataLayout();
        for (gep_type_iterator GTI = gep_type_begin(GEPI),
                               GTE = gep_type_end(GEPI);
             GTI != GTE; ++GTI) {
          ConstantInt *OpC = dyn_cast<ConstantInt>(GTI.getOperand());
          if (!OpC)
            break;
  
          // Handle a struct index, which adds its field offset to the pointer.
          if (StructType *STy = GTI.getStructTypeOrNull()) {
            unsigned ElementIdx = OpC->getZExtValue();
            const StructLayout *SL = DL.getStructLayout(STy);
            GEPOffset +=
                APInt(Offset.getBitWidth(), SL->getElementOffset(ElementIdx));
          } else {
            // For array or vector indices, scale the index by the size of the
            // type.
            APInt Index = OpC->getValue().sextOrTrunc(Offset.getBitWidth());
            GEPOffset += Index * APInt(Offset.getBitWidth(),
                                       DL.getTypeAllocSize(GTI.getIndexedType()));
          }
  
          // If this index has computed an intermediate pointer which is not
          // inbounds, then the result of the GEP is a poison value and we can
          // delete it and all uses.
          if (GEPOffset.ugt(AllocSize))
            return markAsDead(GEPI);
        }
      }
  
      return Base::visitGetElementPtrInst(GEPI);
    }
  
    void handleLoadOrStore(Type *Ty, Instruction &I, const APInt &Offset,
                           uint64_t Size, bool IsVolatile) {
      // We allow splitting of non-volatile loads and stores where the type is an
      // integer type. These may be used to implement 'memcpy' or other "transfer
      // of bits" patterns.
      bool IsSplittable = Ty->isIntegerTy() && !IsVolatile;
  
      insertUse(I, Offset, Size, IsSplittable);
    }
  
    void visitLoadInst(LoadInst &LI) {
      assert((!LI.isSimple() || LI.getType()->isSingleValueType()) &&
             "All simple FCA loads should have been pre-split");
  
      if (!IsOffsetKnown)
        return PI.setAborted(&LI);
  
      const DataLayout &DL = LI.getModule()->getDataLayout();
      uint64_t Size = DL.getTypeStoreSize(LI.getType());
      return handleLoadOrStore(LI.getType(), LI, Offset, Size, LI.isVolatile());
    }
  
    void visitStoreInst(StoreInst &SI) {
      Value *ValOp = SI.getValueOperand();
      if (ValOp == *U)
        return PI.setEscapedAndAborted(&SI);
      if (!IsOffsetKnown)
        return PI.setAborted(&SI);
  
      const DataLayout &DL = SI.getModule()->getDataLayout();
      uint64_t Size = DL.getTypeStoreSize(ValOp->getType());
  
      // If this memory access can be shown to *statically* extend outside the
      // bounds of the allocation, it's behavior is undefined, so simply
      // ignore it. Note that this is more strict than the generic clamping
      // behavior of insertUse. We also try to handle cases which might run the
      // risk of overflow.
      // FIXME: We should instead consider the pointer to have escaped if this
      // function is being instrumented for addressing bugs or race conditions.
      if (Size > AllocSize || Offset.ugt(AllocSize - Size)) {
        LLVM_DEBUG(dbgs() << "WARNING: Ignoring " << Size << " byte store @"
                          << Offset << " which extends past the end of the "
                          << AllocSize << " byte alloca:\n"
                          << "    alloca: " << AS.AI << "\n"
                          << "       use: " << SI << "\n");
        return markAsDead(SI);
      }
  
      assert((!SI.isSimple() || ValOp->getType()->isSingleValueType()) &&
             "All simple FCA stores should have been pre-split");
      handleLoadOrStore(ValOp->getType(), SI, Offset, Size, SI.isVolatile());
    }
  
    void visitMemSetInst(MemSetInst &II) {
      assert(II.getRawDest() == *U && "Pointer use is not the destination?");
      ConstantInt *Length = dyn_cast<ConstantInt>(II.getLength());
      if ((Length && Length->getValue() == 0) ||
          (IsOffsetKnown && Offset.uge(AllocSize)))
        // Zero-length mem transfer intrinsics can be ignored entirely.
        return markAsDead(II);
  
      if (!IsOffsetKnown)
        return PI.setAborted(&II);
  
      insertUse(II, Offset, Length ? Length->getLimitedValue()
                                   : AllocSize - Offset.getLimitedValue(),
                (bool)Length);
    }
  
    void visitMemTransferInst(MemTransferInst &II) {
      ConstantInt *Length = dyn_cast<ConstantInt>(II.getLength());
      if (Length && Length->getValue() == 0)
        // Zero-length mem transfer intrinsics can be ignored entirely.
        return markAsDead(II);
  
      // Because we can visit these intrinsics twice, also check to see if the
      // first time marked this instruction as dead. If so, skip it.
      if (VisitedDeadInsts.count(&II))
        return;
  
      if (!IsOffsetKnown)
        return PI.setAborted(&II);
  
      // This side of the transfer is completely out-of-bounds, and so we can
      // nuke the entire transfer. However, we also need to nuke the other side
      // if already added to our partitions.
      // FIXME: Yet another place we really should bypass this when
      // instrumenting for ASan.
      if (Offset.uge(AllocSize)) {
        SmallDenseMap<Instruction *, unsigned>::iterator MTPI =
            MemTransferSliceMap.find(&II);
        if (MTPI != MemTransferSliceMap.end())
          AS.Slices[MTPI->second].kill();
        return markAsDead(II);
      }
  
      uint64_t RawOffset = Offset.getLimitedValue();
      uint64_t Size = Length ? Length->getLimitedValue() : AllocSize - RawOffset;
  
      // Check for the special case where the same exact value is used for both
      // source and dest.
      if (*U == II.getRawDest() && *U == II.getRawSource()) {
        // For non-volatile transfers this is a no-op.
        if (!II.isVolatile())
          return markAsDead(II);
  
        return insertUse(II, Offset, Size, /*IsSplittable=*/false);
      }
  
      // If we have seen both source and destination for a mem transfer, then
      // they both point to the same alloca.
      bool Inserted;
      SmallDenseMap<Instruction *, unsigned>::iterator MTPI;
      std::tie(MTPI, Inserted) =
          MemTransferSliceMap.insert(std::make_pair(&II, AS.Slices.size()));
      unsigned PrevIdx = MTPI->second;
      if (!Inserted) {
        Slice &PrevP = AS.Slices[PrevIdx];
  
        // Check if the begin offsets match and this is a non-volatile transfer.
        // In that case, we can completely elide the transfer.
        if (!II.isVolatile() && PrevP.beginOffset() == RawOffset) {
          PrevP.kill();
          return markAsDead(II);
        }
  
        // Otherwise we have an offset transfer within the same alloca. We can't
        // split those.
        PrevP.makeUnsplittable();
      }
  
      // Insert the use now that we've fixed up the splittable nature.
      insertUse(II, Offset, Size, /*IsSplittable=*/Inserted && Length);
  
      // Check that we ended up with a valid index in the map.
      assert(AS.Slices[PrevIdx].getUse()->getUser() == &II &&
             "Map index doesn't point back to a slice with this user.");
    }
  
    // Disable SRoA for any intrinsics except for lifetime invariants.
    // FIXME: What about debug intrinsics? This matches old behavior, but
    // doesn't make sense.
    void visitIntrinsicInst(IntrinsicInst &II) {
      if (!IsOffsetKnown)
        return PI.setAborted(&II);
  
      if (II.getIntrinsicID() == Intrinsic::lifetime_start ||
          II.getIntrinsicID() == Intrinsic::lifetime_end) {
        ConstantInt *Length = cast<ConstantInt>(II.getArgOperand(0));
        uint64_t Size = std::min(AllocSize - Offset.getLimitedValue(),
                                 Length->getLimitedValue());
        insertUse(II, Offset, Size, true);
        return;
      }
  
      Base::visitIntrinsicInst(II);
    }
  
    Instruction *hasUnsafePHIOrSelectUse(Instruction *Root, uint64_t &Size) {
      // We consider any PHI or select that results in a direct load or store of
      // the same offset to be a viable use for slicing purposes. These uses
      // are considered unsplittable and the size is the maximum loaded or stored
      // size.
      SmallPtrSet<Instruction *, 4> Visited;
      SmallVector<std::pair<Instruction *, Instruction *>, 4> Uses;
      Visited.insert(Root);
      Uses.push_back(std::make_pair(cast<Instruction>(*U), Root));
      const DataLayout &DL = Root->getModule()->getDataLayout();
      // If there are no loads or stores, the access is dead. We mark that as
      // a size zero access.
      Size = 0;
      do {
        Instruction *I, *UsedI;
        std::tie(UsedI, I) = Uses.pop_back_val();
  
        if (LoadInst *LI = dyn_cast<LoadInst>(I)) {
          Size = std::max(Size, DL.getTypeStoreSize(LI->getType()));
          continue;
        }
        if (StoreInst *SI = dyn_cast<StoreInst>(I)) {
          Value *Op = SI->getOperand(0);
          if (Op == UsedI)
            return SI;
          Size = std::max(Size, DL.getTypeStoreSize(Op->getType()));
          continue;
        }
  
        if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(I)) {
          if (!GEP->hasAllZeroIndices())
            return GEP;
        } else if (!isa<BitCastInst>(I) && !isa<PHINode>(I) &&
                   !isa<SelectInst>(I)) {
          return I;
        }
  
        for (User *U : I->users())
          if (Visited.insert(cast<Instruction>(U)).second)
            Uses.push_back(std::make_pair(I, cast<Instruction>(U)));
      } while (!Uses.empty());
  
      return nullptr;
    }
  
    void visitPHINodeOrSelectInst(Instruction &I) {
      assert(isa<PHINode>(I) || isa<SelectInst>(I));
      if (I.use_empty())
        return markAsDead(I);
  
      // TODO: We could use SimplifyInstruction here to fold PHINodes and
      // SelectInsts. However, doing so requires to change the current
      // dead-operand-tracking mechanism. For instance, suppose neither loading
      // from %U nor %other traps. Then "load (select undef, %U, %other)" does not
      // trap either.  However, if we simply replace %U with undef using the
      // current dead-operand-tracking mechanism, "load (select undef, undef,
      // %other)" may trap because the select may return the first operand
      // "undef".
      if (Value *Result = foldPHINodeOrSelectInst(I)) {
        if (Result == *U)
          // If the result of the constant fold will be the pointer, recurse
          // through the PHI/select as if we had RAUW'ed it.
          enqueueUsers(I);
        else
          // Otherwise the operand to the PHI/select is dead, and we can replace
          // it with undef.
          AS.DeadOperands.push_back(U);
  
        return;
      }
  
      if (!IsOffsetKnown)
        return PI.setAborted(&I);
  
      // See if we already have computed info on this node.
      uint64_t &Size = PHIOrSelectSizes[&I];
      if (!Size) {
        // This is a new PHI/Select, check for an unsafe use of it.
        if (Instruction *UnsafeI = hasUnsafePHIOrSelectUse(&I, Size))
          return PI.setAborted(UnsafeI);
      }
  
      // For PHI and select operands outside the alloca, we can't nuke the entire
      // phi or select -- the other side might still be relevant, so we special
      // case them here and use a separate structure to track the operands
      // themselves which should be replaced with undef.
      // FIXME: This should instead be escaped in the event we're instrumenting
      // for address sanitization.
      if (Offset.uge(AllocSize)) {
        AS.DeadOperands.push_back(U);
        return;
      }
  
      insertUse(I, Offset, Size);
    }
  
    void visitPHINode(PHINode &PN) { visitPHINodeOrSelectInst(PN); }
  
    void visitSelectInst(SelectInst &SI) { visitPHINodeOrSelectInst(SI); }
  
    /// Disable SROA entirely if there are unhandled users of the alloca.
    void visitInstruction(Instruction &I) { PI.setAborted(&I); }
  };
  
  AllocaSlices::AllocaSlices(const DataLayout &DL, AllocaInst &AI)
      :
  #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
        AI(AI),
  #endif
        PointerEscapingInstr(nullptr) {
    SliceBuilder PB(DL, AI, *this);
    SliceBuilder::PtrInfo PtrI = PB.visitPtr(AI);
    if (PtrI.isEscaped() || PtrI.isAborted()) {
      // FIXME: We should sink the escape vs. abort info into the caller nicely,
      // possibly by just storing the PtrInfo in the AllocaSlices.
      PointerEscapingInstr = PtrI.getEscapingInst() ? PtrI.getEscapingInst()
                                                    : PtrI.getAbortingInst();
      assert(PointerEscapingInstr && "Did not track a bad instruction");
      return;
    }
  
    Slices.erase(
        llvm::remove_if(Slices, [](const Slice &S) { return S.isDead(); }),
        Slices.end());
  
  #ifndef NDEBUG
    if (SROARandomShuffleSlices) {
      std::mt19937 MT(static_cast<unsigned>(
          std::chrono::system_clock::now().time_since_epoch().count()));
      std::shuffle(Slices.begin(), Slices.end(), MT);
    }
  #endif
  
    // Sort the uses. This arranges for the offsets to be in ascending order,
    // and the sizes to be in descending order.
    llvm::sort(Slices.begin(), Slices.end());
  }
  
  #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
  
  void AllocaSlices::print(raw_ostream &OS, const_iterator I,
                           StringRef Indent) const {
    printSlice(OS, I, Indent);
    OS << "\n";
    printUse(OS, I, Indent);
  }
  
  void AllocaSlices::printSlice(raw_ostream &OS, const_iterator I,
                                StringRef Indent) const {
    OS << Indent << "[" << I->beginOffset() << "," << I->endOffset() << ")"
       << " slice #" << (I - begin())
       << (I->isSplittable() ? " (splittable)" : "");
  }
  
  void AllocaSlices::printUse(raw_ostream &OS, const_iterator I,
                              StringRef Indent) const {
    OS << Indent << "  used by: " << *I->getUse()->getUser() << "\n";
  }
  
  void AllocaSlices::print(raw_ostream &OS) const {
    if (PointerEscapingInstr) {
      OS << "Can't analyze slices for alloca: " << AI << "\n"
         << "  A pointer to this alloca escaped by:\n"
         << "  " << *PointerEscapingInstr << "\n";
      return;
    }
  
    OS << "Slices of alloca: " << AI << "\n";
    for (const_iterator I = begin(), E = end(); I != E; ++I)
      print(OS, I);
  }
  
  LLVM_DUMP_METHOD void AllocaSlices::dump(const_iterator I) const {
    print(dbgs(), I);
  }
  LLVM_DUMP_METHOD void AllocaSlices::dump() const { print(dbgs()); }
  
  #endif // !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
  
  /// Walk the range of a partitioning looking for a common type to cover this
  /// sequence of slices.
  static Type *findCommonType(AllocaSlices::const_iterator B,
                              AllocaSlices::const_iterator E,
                              uint64_t EndOffset) {
    Type *Ty = nullptr;
    bool TyIsCommon = true;
    IntegerType *ITy = nullptr;
  
    // Note that we need to look at *every* alloca slice's Use to ensure we
    // always get consistent results regardless of the order of slices.
    for (AllocaSlices::const_iterator I = B; I != E; ++I) {
      Use *U = I->getUse();
      if (isa<IntrinsicInst>(*U->getUser()))
        continue;
      if (I->beginOffset() != B->beginOffset() || I->endOffset() != EndOffset)
        continue;
  
      Type *UserTy = nullptr;
      if (LoadInst *LI = dyn_cast<LoadInst>(U->getUser())) {
        UserTy = LI->getType();
      } else if (StoreInst *SI = dyn_cast<StoreInst>(U->getUser())) {
        UserTy = SI->getValueOperand()->getType();
      }
  
      if (IntegerType *UserITy = dyn_cast_or_null<IntegerType>(UserTy)) {
        // If the type is larger than the partition, skip it. We only encounter
        // this for split integer operations where we want to use the type of the
        // entity causing the split. Also skip if the type is not a byte width
        // multiple.
        // TVM local begin
        if (UserITy->getBitWidth() % ByteSizeInBits != 0 ||
            UserITy->getBitWidth() / ByteSizeInBits >
            (EndOffset - B->beginOffset()))
          continue;
        // TVM local end
  
        // Track the largest bitwidth integer type used in this way in case there
        // is no common type.
        if (!ITy || ITy->getBitWidth() < UserITy->getBitWidth())
          ITy = UserITy;
      }
  
      // To avoid depending on the order of slices, Ty and TyIsCommon must not
      // depend on types skipped above.
      if (!UserTy || (Ty && Ty != UserTy))
        TyIsCommon = false; // Give up on anything but an iN type.
      else
        Ty = UserTy;
    }
  
    return TyIsCommon ? Ty : ITy;
  }
  
  /// PHI instructions that use an alloca and are subsequently loaded can be
  /// rewritten to load both input pointers in the pred blocks and then PHI the
  /// results, allowing the load of the alloca to be promoted.
  /// From this:
  ///   %P2 = phi [i32* %Alloca, i32* %Other]
  ///   %V = load i32* %P2
  /// to:
  ///   %V1 = load i32* %Alloca      -> will be mem2reg'd
  ///   ...
  ///   %V2 = load i32* %Other
  ///   ...
  ///   %V = phi [i32 %V1, i32 %V2]
  ///
  /// We can do this to a select if its only uses are loads and if the operands
  /// to the select can be loaded unconditionally.
  ///
  /// FIXME: This should be hoisted into a generic utility, likely in
  /// Transforms/Util/Local.h
  static bool isSafePHIToSpeculate(PHINode &PN) {
    // For now, we can only do this promotion if the load is in the same block
    // as the PHI, and if there are no stores between the phi and load.
    // TODO: Allow recursive phi users.
    // TODO: Allow stores.
    BasicBlock *BB = PN.getParent();
    unsigned MaxAlign = 0;
    bool HaveLoad = false;
    for (User *U : PN.users()) {
      LoadInst *LI = dyn_cast<LoadInst>(U);
      if (!LI || !LI->isSimple())
        return false;
  
      // For now we only allow loads in the same block as the PHI.  This is
      // a common case that happens when instcombine merges two loads through
      // a PHI.
      if (LI->getParent() != BB)
        return false;
  
      // Ensure that there are no instructions between the PHI and the load that
      // could store.
      for (BasicBlock::iterator BBI(PN); &*BBI != LI; ++BBI)
        if (BBI->mayWriteToMemory())
          return false;
  
      MaxAlign = std::max(MaxAlign, LI->getAlignment());
      HaveLoad = true;
    }
  
    if (!HaveLoad)
      return false;
  
    const DataLayout &DL = PN.getModule()->getDataLayout();
  
    // We can only transform this if it is safe to push the loads into the
    // predecessor blocks. The only thing to watch out for is that we can't put
    // a possibly trapping load in the predecessor if it is a critical edge.
    for (unsigned Idx = 0, Num = PN.getNumIncomingValues(); Idx != Num; ++Idx) {
      TerminatorInst *TI = PN.getIncomingBlock(Idx)->getTerminator();
      Value *InVal = PN.getIncomingValue(Idx);
  
      // If the value is produced by the terminator of the predecessor (an
      // invoke) or it has side-effects, there is no valid place to put a load
      // in the predecessor.
      if (TI == InVal || TI->mayHaveSideEffects())
        return false;
  
      // If the predecessor has a single successor, then the edge isn't
      // critical.
      if (TI->getNumSuccessors() == 1)
        continue;
  
      // If this pointer is always safe to load, or if we can prove that there
      // is already a load in the block, then we can move the load to the pred
      // block.
      if (isSafeToLoadUnconditionally(InVal, MaxAlign, DL, TI))
        continue;
  
      return false;
    }
  
    return true;
  }
  
  static void speculatePHINodeLoads(PHINode &PN) {
    LLVM_DEBUG(dbgs() << "    original: " << PN << "\n");
  
    Type *LoadTy = cast<PointerType>(PN.getType())->getElementType();
    IRBuilderTy PHIBuilder(&PN);
    PHINode *NewPN = PHIBuilder.CreatePHI(LoadTy, PN.getNumIncomingValues(),
                                          PN.getName() + ".sroa.speculated");
  
    // Get the AA tags and alignment to use from one of the loads.  It doesn't
    // matter which one we get and if any differ.
    LoadInst *SomeLoad = cast<LoadInst>(PN.user_back());
  
    AAMDNodes AATags;
    SomeLoad->getAAMetadata(AATags);
    unsigned Align = SomeLoad->getAlignment();
  
    // Rewrite all loads of the PN to use the new PHI.
    while (!PN.use_empty()) {
      LoadInst *LI = cast<LoadInst>(PN.user_back());
      LI->replaceAllUsesWith(NewPN);
      LI->eraseFromParent();
    }
  
    // Inject loads into all of the pred blocks.
    DenseMap<BasicBlock*, Value*> InjectedLoads;
    for (unsigned Idx = 0, Num = PN.getNumIncomingValues(); Idx != Num; ++Idx) {
      BasicBlock *Pred = PN.getIncomingBlock(Idx);
      Value *InVal = PN.getIncomingValue(Idx);
  
      // A PHI node is allowed to have multiple (duplicated) entries for the same
      // basic block, as long as the value is the same. So if we already injected
      // a load in the predecessor, then we should reuse the same load for all
      // duplicated entries.
      if (Value* V = InjectedLoads.lookup(Pred)) {
        NewPN->addIncoming(V, Pred);
        continue;
      }
  
      TerminatorInst *TI = Pred->getTerminator();
      IRBuilderTy PredBuilder(TI);
  
      LoadInst *Load = PredBuilder.CreateLoad(
          InVal, (PN.getName() + ".sroa.speculate.load." + Pred->getName()));
      ++NumLoadsSpeculated;
      Load->setAlignment(Align);
      if (AATags)
        Load->setAAMetadata(AATags);
      NewPN->addIncoming(Load, Pred);
      InjectedLoads[Pred] = Load;
    }
  
    LLVM_DEBUG(dbgs() << "          speculated to: " << *NewPN << "\n");
    PN.eraseFromParent();
  }
  
  /// Select instructions that use an alloca and are subsequently loaded can be
  /// rewritten to load both input pointers and then select between the result,
  /// allowing the load of the alloca to be promoted.
  /// From this:
  ///   %P2 = select i1 %cond, i32* %Alloca, i32* %Other
  ///   %V = load i32* %P2
  /// to:
  ///   %V1 = load i32* %Alloca      -> will be mem2reg'd
  ///   %V2 = load i32* %Other
  ///   %V = select i1 %cond, i32 %V1, i32 %V2
  ///
  /// We can do this to a select if its only uses are loads and if the operand
  /// to the select can be loaded unconditionally.
  static bool isSafeSelectToSpeculate(SelectInst &SI) {
    Value *TValue = SI.getTrueValue();
    Value *FValue = SI.getFalseValue();
    const DataLayout &DL = SI.getModule()->getDataLayout();
  
    for (User *U : SI.users()) {
      LoadInst *LI = dyn_cast<LoadInst>(U);
      if (!LI || !LI->isSimple())
        return false;
  
      // Both operands to the select need to be dereferenceable, either
      // absolutely (e.g. allocas) or at this point because we can see other
      // accesses to it.
      if (!isSafeToLoadUnconditionally(TValue, LI->getAlignment(), DL, LI))
        return false;
      if (!isSafeToLoadUnconditionally(FValue, LI->getAlignment(), DL, LI))
        return false;
    }
  
    return true;
  }
  
  static void speculateSelectInstLoads(SelectInst &SI) {
    LLVM_DEBUG(dbgs() << "    original: " << SI << "\n");
  
    IRBuilderTy IRB(&SI);
    Value *TV = SI.getTrueValue();
    Value *FV = SI.getFalseValue();
    // Replace the loads of the select with a select of two loads.
    while (!SI.use_empty()) {
      LoadInst *LI = cast<LoadInst>(SI.user_back());
      assert(LI->isSimple() && "We only speculate simple loads");
  
      IRB.SetInsertPoint(LI);
      LoadInst *TL =
          IRB.CreateLoad(TV, LI->getName() + ".sroa.speculate.load.true");
      LoadInst *FL =
          IRB.CreateLoad(FV, LI->getName() + ".sroa.speculate.load.false");
      NumLoadsSpeculated += 2;
  
      // Transfer alignment and AA info if present.
      TL->setAlignment(LI->getAlignment());
      FL->setAlignment(LI->getAlignment());
  
      AAMDNodes Tags;
      LI->getAAMetadata(Tags);
      if (Tags) {
        TL->setAAMetadata(Tags);
        FL->setAAMetadata(Tags);
      }
  
      Value *V = IRB.CreateSelect(SI.getCondition(), TL, FL,
                                  LI->getName() + ".sroa.speculated");
  
      LLVM_DEBUG(dbgs() << "          speculated to: " << *V << "\n");
      LI->replaceAllUsesWith(V);
      LI->eraseFromParent();
    }
    SI.eraseFromParent();
  }
  
  /// Build a GEP out of a base pointer and indices.
  ///
  /// This will return the BasePtr if that is valid, or build a new GEP
  /// instruction using the IRBuilder if GEP-ing is needed.
  static Value *buildGEP(IRBuilderTy &IRB, Value *BasePtr,
                         SmallVectorImpl<Value *> &Indices, Twine NamePrefix) {
    if (Indices.empty())
      return BasePtr;
  
    // A single zero index is a no-op, so check for this and avoid building a GEP
    // in that case.
    if (Indices.size() == 1 && cast<ConstantInt>(Indices.back())->isZero())
      return BasePtr;
  
    return IRB.CreateInBoundsGEP(nullptr, BasePtr, Indices,
                                 NamePrefix + "sroa_idx");
  }
  
  /// Get a natural GEP off of the BasePtr walking through Ty toward
  /// TargetTy without changing the offset of the pointer.
  ///
  /// This routine assumes we've already established a properly offset GEP with
  /// Indices, and arrived at the Ty type. The goal is to continue to GEP with
  /// zero-indices down through type layers until we find one the same as
  /// TargetTy. If we can't find one with the same type, we at least try to use
  /// one with the same size. If none of that works, we just produce the GEP as
  /// indicated by Indices to have the correct offset.
  static Value *getNaturalGEPWithType(IRBuilderTy &IRB, const DataLayout &DL,
                                      Value *BasePtr, Type *Ty, Type *TargetTy,
                                      SmallVectorImpl<Value *> &Indices,
                                      Twine NamePrefix) {
    if (Ty == TargetTy)
      return buildGEP(IRB, BasePtr, Indices, NamePrefix);
  
    // Pointer size to use for the indices.
    unsigned PtrSize = DL.getPointerTypeSizeInBits(BasePtr->getType());
  
    // See if we can descend into a struct and locate a field with the correct
    // type.
    unsigned NumLayers = 0;
    Type *ElementTy = Ty;
    do {
      if (ElementTy->isPointerTy())
        break;
  
      if (ArrayType *ArrayTy = dyn_cast<ArrayType>(ElementTy)) {
        ElementTy = ArrayTy->getElementType();
        Indices.push_back(IRB.getIntN(PtrSize, 0));
      } else if (VectorType *VectorTy = dyn_cast<VectorType>(ElementTy)) {
        ElementTy = VectorTy->getElementType();
        Indices.push_back(IRB.getInt32(0));
      } else if (StructType *STy = dyn_cast<StructType>(ElementTy)) {
        if (STy->element_begin() == STy->element_end())
          break; // Nothing left to descend into.
        ElementTy = *STy->element_begin();
        Indices.push_back(IRB.getInt32(0));
      } else {
        break;
      }
      ++NumLayers;
    } while (ElementTy != TargetTy);
    if (ElementTy != TargetTy)
      Indices.erase(Indices.end() - NumLayers, Indices.end());
  
    return buildGEP(IRB, BasePtr, Indices, NamePrefix);
  }
  
  /// Recursively compute indices for a natural GEP.
  ///
  /// This is the recursive step for getNaturalGEPWithOffset that walks down the
  /// element types adding appropriate indices for the GEP.
  static Value *getNaturalGEPRecursively(IRBuilderTy &IRB, const DataLayout &DL,
                                         Value *Ptr, Type *Ty, APInt &Offset,
                                         Type *TargetTy,
                                         SmallVectorImpl<Value *> &Indices,
                                         Twine NamePrefix) {
    if (Offset == 0)
      return getNaturalGEPWithType(IRB, DL, Ptr, Ty, TargetTy, Indices,
                                   NamePrefix);
  
    // We can't recurse through pointer types.
    if (Ty->isPointerTy())
      return nullptr;
  
    // We try to analyze GEPs over vectors here, but note that these GEPs are
    // extremely poorly defined currently. The long-term goal is to remove GEPing
    // over a vector from the IR completely.
    if (VectorType *VecTy = dyn_cast<VectorType>(Ty)) {
      unsigned ElementSizeInBits = DL.getTypeSizeInBits(VecTy->getScalarType());
      // TVM local begin
      if (ElementSizeInBits % ByteSizeInBits != 0) {
      // TVM local end
        // GEPs over non-multiple of 8 size vector elements are invalid.
        return nullptr;
      }
      // TVM local begin
      APInt ElementSize(Offset.getBitWidth(), ElementSizeInBits / ByteSizeInBits);
      // TVM local end
      APInt NumSkippedElements = Offset.sdiv(ElementSize);
      if (NumSkippedElements.ugt(VecTy->getNumElements()))
        return nullptr;
      Offset -= NumSkippedElements * ElementSize;
      Indices.push_back(IRB.getInt(NumSkippedElements));
      return getNaturalGEPRecursively(IRB, DL, Ptr, VecTy->getElementType(),
                                      Offset, TargetTy, Indices, NamePrefix);
    }
  
    if (ArrayType *ArrTy = dyn_cast<ArrayType>(Ty)) {
      Type *ElementTy = ArrTy->getElementType();
      APInt ElementSize(Offset.getBitWidth(), DL.getTypeAllocSize(ElementTy));
      APInt NumSkippedElements = Offset.sdiv(ElementSize);
      if (NumSkippedElements.ugt(ArrTy->getNumElements()))
        return nullptr;
  
      Offset -= NumSkippedElements * ElementSize;
      Indices.push_back(IRB.getInt(NumSkippedElements));
      return getNaturalGEPRecursively(IRB, DL, Ptr, ElementTy, Offset, TargetTy,
                                      Indices, NamePrefix);
    }
  
    StructType *STy = dyn_cast<StructType>(Ty);
    if (!STy)
      return nullptr;
  
    const StructLayout *SL = DL.getStructLayout(STy);
    uint64_t StructOffset = Offset.getZExtValue();
    if (StructOffset >= SL->getSizeInBytes())
      return nullptr;
    unsigned Index = SL->getElementContainingOffset(StructOffset);
    Offset -= APInt(Offset.getBitWidth(), SL->getElementOffset(Index));
    Type *ElementTy = STy->getElementType(Index);
    if (Offset.uge(DL.getTypeAllocSize(ElementTy)))
      return nullptr; // The offset points into alignment padding.
  
    Indices.push_back(IRB.getInt32(Index));
    return getNaturalGEPRecursively(IRB, DL, Ptr, ElementTy, Offset, TargetTy,
                                    Indices, NamePrefix);
  }
  
  /// Get a natural GEP from a base pointer to a particular offset and
  /// resulting in a particular type.
  ///
  /// The goal is to produce a "natural" looking GEP that works with the existing
  /// composite types to arrive at the appropriate offset and element type for
  /// a pointer. TargetTy is the element type the returned GEP should point-to if
  /// possible. We recurse by decreasing Offset, adding the appropriate index to
  /// Indices, and setting Ty to the result subtype.
  ///
  /// If no natural GEP can be constructed, this function returns null.
  static Value *getNaturalGEPWithOffset(IRBuilderTy &IRB, const DataLayout &DL,
                                        Value *Ptr, APInt Offset, Type *TargetTy,
                                        SmallVectorImpl<Value *> &Indices,
                                        Twine NamePrefix) {
    PointerType *Ty = cast<PointerType>(Ptr->getType());
  
    // Don't consider any GEPs through an i8* as natural unless the TargetTy is
    // an i8.
    // TVM local begin
    if (Ty == IRB.getIntBytePtrTy(Ty->getAddressSpace()) &&
        TargetTy->isIntegerTy(ByteSizeInBits))
    // TVM local end
      return nullptr;
  
    Type *ElementTy = Ty->getElementType();
    if (!ElementTy->isSized())
      return nullptr; // We can't GEP through an unsized element.
    APInt ElementSize(Offset.getBitWidth(), DL.getTypeAllocSize(ElementTy));
    if (ElementSize == 0)
      return nullptr; // Zero-length arrays can't help us build a natural GEP.
    APInt NumSkippedElements = Offset.sdiv(ElementSize);
  
    Offset -= NumSkippedElements * ElementSize;
    Indices.push_back(IRB.getInt(NumSkippedElements));
    return getNaturalGEPRecursively(IRB, DL, Ptr, ElementTy, Offset, TargetTy,
                                    Indices, NamePrefix);
  }
  
  /// Compute an adjusted pointer from Ptr by Offset bytes where the
  /// resulting pointer has PointerTy.
  ///
  /// This tries very hard to compute a "natural" GEP which arrives at the offset
  /// and produces the pointer type desired. Where it cannot, it will try to use
  /// the natural GEP to arrive at the offset and bitcast to the type. Where that
  /// fails, it will try to use an existing i8* and GEP to the byte offset and
  /// bitcast to the type.
  ///
  /// The strategy for finding the more natural GEPs is to peel off layers of the
  /// pointer, walking back through bit casts and GEPs, searching for a base
  /// pointer from which we can compute a natural GEP with the desired
  /// properties. The algorithm tries to fold as many constant indices into
  /// a single GEP as possible, thus making each GEP more independent of the
  /// surrounding code.
  static Value *getAdjustedPtr(IRBuilderTy &IRB, const DataLayout &DL, Value *Ptr,
                               APInt Offset, Type *PointerTy, Twine NamePrefix) {
    // Even though we don't look through PHI nodes, we could be called on an
    // instruction in an unreachable block, which may be on a cycle.
    SmallPtrSet<Value *, 4> Visited;
    Visited.insert(Ptr);
    SmallVector<Value *, 4> Indices;
  
    // We may end up computing an offset pointer that has the wrong type. If we
    // never are able to compute one directly that has the correct type, we'll
    // fall back to it, so keep it and the base it was computed from around here.
    Value *OffsetPtr = nullptr;
    Value *OffsetBasePtr;
  
    // Remember any i8 pointer we come across to re-use if we need to do a raw
    // byte offset.
    Value *Int8Ptr = nullptr;
    APInt Int8PtrOffset(Offset.getBitWidth(), 0);
  
    Type *TargetTy = PointerTy->getPointerElementType();
  
    do {
      // First fold any existing GEPs into the offset.
      while (GEPOperator *GEP = dyn_cast<GEPOperator>(Ptr)) {
        APInt GEPOffset(Offset.getBitWidth(), 0);
        if (!GEP->accumulateConstantOffset(DL, GEPOffset))
          break;
        Offset += GEPOffset;
        Ptr = GEP->getPointerOperand();
        if (!Visited.insert(Ptr).second)
          break;
      }
  
      // See if we can perform a natural GEP here.
      Indices.clear();
      if (Value *P = getNaturalGEPWithOffset(IRB, DL, Ptr, Offset, TargetTy,
                                             Indices, NamePrefix)) {
        // If we have a new natural pointer at the offset, clear out any old
        // offset pointer we computed. Unless it is the base pointer or
        // a non-instruction, we built a GEP we don't need. Zap it.
        if (OffsetPtr && OffsetPtr != OffsetBasePtr)
          if (Instruction *I = dyn_cast<Instruction>(OffsetPtr)) {
            assert(I->use_empty() && "Built a GEP with uses some how!");
            I->eraseFromParent();
          }
        OffsetPtr = P;
        OffsetBasePtr = Ptr;
        // If we also found a pointer of the right type, we're done.
        if (P->getType() == PointerTy)
          return P;
      }
  
      // Stash this pointer if we've found an i8*.
      // TVM local begin
      if (Ptr->getType()->isIntegerTy(ByteSizeInBits)) {
      // TVM local end
        Int8Ptr = Ptr;
        Int8PtrOffset = Offset;
      }
  
      // Peel off a layer of the pointer and update the offset appropriately.
      if (Operator::getOpcode(Ptr) == Instruction::BitCast) {
        Ptr = cast<Operator>(Ptr)->getOperand(0);
      } else if (GlobalAlias *GA = dyn_cast<GlobalAlias>(Ptr)) {
        if (GA->isInterposable())
          break;
        Ptr = GA->getAliasee();
      } else {
        break;
      }
      assert(Ptr->getType()->isPointerTy() && "Unexpected operand type!");
    } while (Visited.insert(Ptr).second);
  
    if (!OffsetPtr) {
      if (!Int8Ptr) {
        Int8Ptr = IRB.CreateBitCast(
            // TVM local begin
            Ptr, IRB.getIntBytePtrTy(PointerTy->getPointerAddressSpace()),
            // TVM local end
            NamePrefix + "sroa_raw_cast");
        Int8PtrOffset = Offset;
      }
  
      // TVM local begin
      OffsetPtr = Int8PtrOffset == 0
                      ? Int8Ptr
                      : IRB.CreateInBoundsGEP(IRB.getByteTy(), Int8Ptr,
                                              IRB.getInt(Int8PtrOffset),
                                              NamePrefix + "sroa_raw_idx");
      // TVM local end
    }
    Ptr = OffsetPtr;
  
    // On the off chance we were targeting i8*, guard the bitcast here.
    if (Ptr->getType() != PointerTy)
      Ptr = IRB.CreateBitCast(Ptr, PointerTy, NamePrefix + "sroa_cast");
  
    return Ptr;
  }
  
  /// Compute the adjusted alignment for a load or store from an offset.
  static unsigned getAdjustedAlignment(Instruction *I, uint64_t Offset,
                                       const DataLayout &DL) {
    unsigned Alignment;
    Type *Ty;
    if (auto *LI = dyn_cast<LoadInst>(I)) {
      Alignment = LI->getAlignment();
      Ty = LI->getType();
    } else if (auto *SI = dyn_cast<StoreInst>(I)) {
      Alignment = SI->getAlignment();
      Ty = SI->getValueOperand()->getType();
    } else {
      llvm_unreachable("Only loads and stores are allowed!");
    }
  
    if (!Alignment)
      Alignment = DL.getABITypeAlignment(Ty);
  
    return MinAlign(Alignment, Offset);
  }
  
  /// Test whether we can convert a value from the old to the new type.
  ///
  /// This predicate should be used to guard calls to convertValue in order to
  /// ensure that we only try to convert viable values. The strategy is that we
  /// will peel off single element struct and array wrappings to get to an
  /// underlying value, and convert that value.
  static bool canConvertValue(const DataLayout &DL, Type *OldTy, Type *NewTy) {
    if (OldTy == NewTy)
      return true;
  
    // For integer types, we can't handle any bit-width differences. This would
    // break both vector conversions with extension and introduce endianness
    // issues when in conjunction with loads and stores.
    if (isa<IntegerType>(OldTy) && isa<IntegerType>(NewTy)) {
      assert(cast<IntegerType>(OldTy)->getBitWidth() !=
                 cast<IntegerType>(NewTy)->getBitWidth() &&
             "We can't have the same bitwidth for different int types");
      return false;
    }
  
    if (DL.getTypeSizeInBits(NewTy) != DL.getTypeSizeInBits(OldTy))
      return false;
    if (!NewTy->isSingleValueType() || !OldTy->isSingleValueType())
      return false;
  
    // We can convert pointers to integers and vice-versa. Same for vectors
    // of pointers and integers.
    OldTy = OldTy->getScalarType();
    NewTy = NewTy->getScalarType();
    if (NewTy->isPointerTy() || OldTy->isPointerTy()) {
      if (NewTy->isPointerTy() && OldTy->isPointerTy()) {
        return cast<PointerType>(NewTy)->getPointerAddressSpace() ==
          cast<PointerType>(OldTy)->getPointerAddressSpace();
      }
  
      // We can convert integers to integral pointers, but not to non-integral
      // pointers.
      if (OldTy->isIntegerTy())
        return !DL.isNonIntegralPointerType(NewTy);
  
      // We can convert integral pointers to integers, but non-integral pointers
      // need to remain pointers.
      if (!DL.isNonIntegralPointerType(OldTy))
        return NewTy->isIntegerTy();
  
      return false;
    }
  
    return true;
  }
  
  /// Generic routine to convert an SSA value to a value of a different
  /// type.
  ///
  /// This will try various different casting techniques, such as bitcasts,
  /// inttoptr, and ptrtoint casts. Use the \c canConvertValue predicate to test
  /// two types for viability with this routine.
  static Value *convertValue(const DataLayout &DL, IRBuilderTy &IRB, Value *V,
                             Type *NewTy) {
    Type *OldTy = V->getType();
    assert(canConvertValue(DL, OldTy, NewTy) && "Value not convertable to type");
  
    if (OldTy == NewTy)
      return V;
  
    assert(!(isa<IntegerType>(OldTy) && isa<IntegerType>(NewTy)) &&
           "Integer types must be the exact same to convert.");
  
    // See if we need inttoptr for this type pair. A cast involving both scalars
    // and vectors requires and additional bitcast.
    if (OldTy->isIntOrIntVectorTy() && NewTy->isPtrOrPtrVectorTy()) {
      // Expand <2 x i32> to i8* --> <2 x i32> to i64 to i8*
      if (OldTy->isVectorTy() && !NewTy->isVectorTy())
        return IRB.CreateIntToPtr(IRB.CreateBitCast(V, DL.getIntPtrType(NewTy)),
                                  NewTy);
  
      // Expand i128 to <2 x i8*> --> i128 to <2 x i64> to <2 x i8*>
      if (!OldTy->isVectorTy() && NewTy->isVectorTy())
        return IRB.CreateIntToPtr(IRB.CreateBitCast(V, DL.getIntPtrType(NewTy)),
                                  NewTy);
  
      return IRB.CreateIntToPtr(V, NewTy);
    }
  
    // See if we need ptrtoint for this type pair. A cast involving both scalars
    // and vectors requires and additional bitcast.
    if (OldTy->isPtrOrPtrVectorTy() && NewTy->isIntOrIntVectorTy()) {
      // Expand <2 x i8*> to i128 --> <2 x i8*> to <2 x i64> to i128
      if (OldTy->isVectorTy() && !NewTy->isVectorTy())
        return IRB.CreateBitCast(IRB.CreatePtrToInt(V, DL.getIntPtrType(OldTy)),
                                 NewTy);
  
      // Expand i8* to <2 x i32> --> i8* to i64 to <2 x i32>
      if (!OldTy->isVectorTy() && NewTy->isVectorTy())
        return IRB.CreateBitCast(IRB.CreatePtrToInt(V, DL.getIntPtrType(OldTy)),
                                 NewTy);
  
      return IRB.CreatePtrToInt(V, NewTy);
    }
  
    return IRB.CreateBitCast(V, NewTy);
  }
  
  /// Test whether the given slice use can be promoted to a vector.
  ///
  /// This function is called to test each entry in a partition which is slated
  /// for a single slice.
  static bool isVectorPromotionViableForSlice(Partition &P, const Slice &S,
                                              VectorType *Ty,
                                              uint64_t ElementSize,
                                              const DataLayout &DL) {
    // First validate the slice offsets.
    uint64_t BeginOffset =
        std::max(S.beginOffset(), P.beginOffset()) - P.beginOffset();
    uint64_t BeginIndex = BeginOffset / ElementSize;
    if (BeginIndex * ElementSize != BeginOffset ||
        BeginIndex >= Ty->getNumElements())
      return false;
    uint64_t EndOffset =
        std::min(S.endOffset(), P.endOffset()) - P.beginOffset();
    uint64_t EndIndex = EndOffset / ElementSize;
    if (EndIndex * ElementSize != EndOffset || EndIndex > Ty->getNumElements())
      return false;
  
    assert(EndIndex > BeginIndex && "Empty vector!");
    uint64_t NumElements = EndIndex - BeginIndex;
    Type *SliceTy = (NumElements == 1)
                        ? Ty->getElementType()
                        : VectorType::get(Ty->getElementType(), NumElements);
    // TVM local begin
    Type *SplitIntTy =
        Type::getIntNTy(Ty->getContext(), NumElements * ElementSize *
                        ByteSizeInBits);
    // TVM local end
  
    Use *U = S.getUse();
  
    if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(U->getUser())) {
      if (MI->isVolatile())
        return false;
      if (!S.isSplittable())
        return false; // Skip any unsplittable intrinsics.
    } else if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(U->getUser())) {
      if (II->getIntrinsicID() != Intrinsic::lifetime_start &&
          II->getIntrinsicID() != Intrinsic::lifetime_end)
        return false;
    } else if (U->get()->getType()->getPointerElementType()->isStructTy()) {
      // Disable vector promotion when there are loads or stores of an FCA.
      return false;
    } else if (LoadInst *LI = dyn_cast<LoadInst>(U->getUser())) {
      if (LI->isVolatile())
        return false;
      Type *LTy = LI->getType();
      if (P.beginOffset() > S.beginOffset() || P.endOffset() < S.endOffset()) {
        assert(LTy->isIntegerTy());
        LTy = SplitIntTy;
      }
      if (!canConvertValue(DL, SliceTy, LTy))
        return false;
    } else if (StoreInst *SI = dyn_cast<StoreInst>(U->getUser())) {
      if (SI->isVolatile())
        return false;
      Type *STy = SI->getValueOperand()->getType();
      if (P.beginOffset() > S.beginOffset() || P.endOffset() < S.endOffset()) {
        assert(STy->isIntegerTy());
        STy = SplitIntTy;
      }
      if (!canConvertValue(DL, STy, SliceTy))
        return false;
    } else {
      return false;
    }
  
    return true;
  }
  
  /// Test whether the given alloca partitioning and range of slices can be
  /// promoted to a vector.
  ///
  /// This is a quick test to check whether we can rewrite a particular alloca
  /// partition (and its newly formed alloca) into a vector alloca with only
  /// whole-vector loads and stores such that it could be promoted to a vector
  /// SSA value. We only can ensure this for a limited set of operations, and we
  /// don't want to do the rewrites unless we are confident that the result will
  /// be promotable, so we have an early test here.
  static VectorType *isVectorPromotionViable(Partition &P, const DataLayout &DL) {
    // Collect the candidate types for vector-based promotion. Also track whether
    // we have different element types.
    SmallVector<VectorType *, 4> CandidateTys;
    Type *CommonEltTy = nullptr;
    bool HaveCommonEltTy = true;
    auto CheckCandidateType = [&](Type *Ty) {
      if (auto *VTy = dyn_cast<VectorType>(Ty)) {
        CandidateTys.push_back(VTy);
        if (!CommonEltTy)
          CommonEltTy = VTy->getElementType();
        else if (CommonEltTy != VTy->getElementType())
          HaveCommonEltTy = false;
      }
    };
    // Consider any loads or stores that are the exact size of the slice.
    for (const Slice &S : P)
      if (S.beginOffset() == P.beginOffset() &&
          S.endOffset() == P.endOffset()) {
        if (auto *LI = dyn_cast<LoadInst>(S.getUse()->getUser()))
          CheckCandidateType(LI->getType());
        else if (auto *SI = dyn_cast<StoreInst>(S.getUse()->getUser()))
          CheckCandidateType(SI->getValueOperand()->getType());
      }
  
    // If we didn't find a vector type, nothing to do here.
    if (CandidateTys.empty())
      return nullptr;
  
    // Remove non-integer vector types if we had multiple common element types.
    // FIXME: It'd be nice to replace them with integer vector types, but we can't
    // do that until all the backends are known to produce good code for all
    // integer vector types.
    if (!HaveCommonEltTy) {
      CandidateTys.erase(
          llvm::remove_if(CandidateTys,
                          [](VectorType *VTy) {
                            return !VTy->getElementType()->isIntegerTy();
                          }),
          CandidateTys.end());
  
      // If there were no integer vector types, give up.
      if (CandidateTys.empty())
        return nullptr;
  
      // Rank the remaining candidate vector types. This is easy because we know
      // they're all integer vectors. We sort by ascending number of elements.
      auto RankVectorTypes = [&DL](VectorType *RHSTy, VectorType *LHSTy) {
        (void)DL;
        assert(DL.getTypeSizeInBits(RHSTy) == DL.getTypeSizeInBits(LHSTy) &&
               "Cannot have vector types of different sizes!");
        assert(RHSTy->getElementType()->isIntegerTy() &&
               "All non-integer types eliminated!");
        assert(LHSTy->getElementType()->isIntegerTy() &&
               "All non-integer types eliminated!");
        return RHSTy->getNumElements() < LHSTy->getNumElements();
      };
      llvm::sort(CandidateTys.begin(), CandidateTys.end(), RankVectorTypes);
      CandidateTys.erase(
          std::unique(CandidateTys.begin(), CandidateTys.end(), RankVectorTypes),
          CandidateTys.end());
    } else {
  // The only way to have the same element type in every vector type is to
  // have the same vector type. Check that and remove all but one.
  #ifndef NDEBUG
      for (VectorType *VTy : CandidateTys) {
        assert(VTy->getElementType() == CommonEltTy &&
               "Unaccounted for element type!");
        assert(VTy == CandidateTys[0] &&
               "Different vector types with the same element type!");
      }
  #endif
      CandidateTys.resize(1);
    }
  
    // Try each vector type, and return the one which works.
    auto CheckVectorTypeForPromotion = [&](VectorType *VTy) {
      uint64_t ElementSize = DL.getTypeSizeInBits(VTy->getElementType());
  
      // While the definition of LLVM vectors is bitpacked, we don't support sizes
      // that aren't byte sized.
      // TVM local begin
      if (ElementSize % ByteSizeInBits)
        return false;
      assert((DL.getTypeSizeInBits(VTy) % ByteSizeInBits) == 0 &&
             "vector size not a multiple of element size?");
      ElementSize /= ByteSizeInBits;
      // TVM local end
  
      for (const Slice &S : P)
        if (!isVectorPromotionViableForSlice(P, S, VTy, ElementSize, DL))
          return false;
  
      for (const Slice *S : P.splitSliceTails())
        if (!isVectorPromotionViableForSlice(P, *S, VTy, ElementSize, DL))
          return false;
  
      return true;
    };
    for (VectorType *VTy : CandidateTys)
      if (CheckVectorTypeForPromotion(VTy))
        return VTy;
  
    return nullptr;
  }
  
  /// Test whether a slice of an alloca is valid for integer widening.
  ///
  /// This implements the necessary checking for the \c isIntegerWideningViable
  /// test below on a single slice of the alloca.
  static bool isIntegerWideningViableForSlice(const Slice &S,
                                              uint64_t AllocBeginOffset,
                                              Type *AllocaTy,
                                              const DataLayout &DL,
                                              bool &WholeAllocaOp) {
    uint64_t Size = DL.getTypeStoreSize(AllocaTy);
  
    uint64_t RelBegin = S.beginOffset() - AllocBeginOffset;
    uint64_t RelEnd = S.endOffset() - AllocBeginOffset;
  
    // We can't reasonably handle cases where the load or store extends past
    // the end of the alloca's type and into its padding.
    if (RelEnd > Size)
      return false;
  
    Use *U = S.getUse();
  
    if (LoadInst *LI = dyn_cast<LoadInst>(U->getUser())) {
      if (LI->isVolatile())
        return false;
      // We can't handle loads that extend past the allocated memory.
      if (DL.getTypeStoreSize(LI->getType()) > Size)
        return false;
      // So far, AllocaSliceRewriter does not support widening split slice tails
      // in rewriteIntegerLoad.
      if (S.beginOffset() < AllocBeginOffset)
        return false;
      // Note that we don't count vector loads or stores as whole-alloca
      // operations which enable integer widening because we would prefer to use
      // vector widening instead.
      if (!isa<VectorType>(LI->getType()) && RelBegin == 0 && RelEnd == Size)
        WholeAllocaOp = true;
      if (IntegerType *ITy = dyn_cast<IntegerType>(LI->getType())) {
        if (ITy->getBitWidth() < DL.getTypeStoreSizeInBits(ITy))
          return false;
      } else if (RelBegin != 0 || RelEnd != Size ||
                 !canConvertValue(DL, AllocaTy, LI->getType())) {
        // Non-integer loads need to be convertible from the alloca type so that
        // they are promotable.
        return false;
      }
    } else if (StoreInst *SI = dyn_cast<StoreInst>(U->getUser())) {
      Type *ValueTy = SI->getValueOperand()->getType();
      if (SI->isVolatile())
        return false;
      // We can't handle stores that extend past the allocated memory.
      if (DL.getTypeStoreSize(ValueTy) > Size)
        return false;
      // So far, AllocaSliceRewriter does not support widening split slice tails
      // in rewriteIntegerStore.
      if (S.beginOffset() < AllocBeginOffset)
        return false;
      // Note that we don't count vector loads or stores as whole-alloca
      // operations which enable integer widening because we would prefer to use
      // vector widening instead.
      if (!isa<VectorType>(ValueTy) && RelBegin == 0 && RelEnd == Size)
        WholeAllocaOp = true;
      if (IntegerType *ITy = dyn_cast<IntegerType>(ValueTy)) {
        if (ITy->getBitWidth() < DL.getTypeStoreSizeInBits(ITy))
          return false;
      } else if (RelBegin != 0 || RelEnd != Size ||
                 !canConvertValue(DL, ValueTy, AllocaTy)) {
        // Non-integer stores need to be convertible to the alloca type so that
        // they are promotable.
        return false;
      }
    } else if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(U->getUser())) {
      if (MI->isVolatile() || !isa<Constant>(MI->getLength()))
        return false;
      if (!S.isSplittable())
        return false; // Skip any unsplittable intrinsics.
    } else if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(U->getUser())) {
      if (II->getIntrinsicID() != Intrinsic::lifetime_start &&
          II->getIntrinsicID() != Intrinsic::lifetime_end)
        return false;
    } else {
      return false;
    }
  
    return true;
  }
  
  /// Test whether the given alloca partition's integer operations can be
  /// widened to promotable ones.
  ///
  /// This is a quick test to check whether we can rewrite the integer loads and
  /// stores to a particular alloca into wider loads and stores and be able to
  /// promote the resulting alloca.
  static bool isIntegerWideningViable(Partition &P, Type *AllocaTy,
                                      const DataLayout &DL) {
    uint64_t SizeInBits = DL.getTypeSizeInBits(AllocaTy);
    // Don't create integer types larger than the maximum bitwidth.
    if (SizeInBits > IntegerType::MAX_INT_BITS)
      return false;
  
    // Don't try to handle allocas with bit-padding.
    if (SizeInBits != DL.getTypeStoreSizeInBits(AllocaTy))
      return false;
  
    // We need to ensure that an integer type with the appropriate bitwidth can
    // be converted to the alloca type, whatever that is. We don't want to force
    // the alloca itself to have an integer type if there is a more suitable one.
    Type *IntTy = Type::getIntNTy(AllocaTy->getContext(), SizeInBits);
    if (!canConvertValue(DL, AllocaTy, IntTy) ||
        !canConvertValue(DL, IntTy, AllocaTy))
      return false;
  
    // While examining uses, we ensure that the alloca has a covering load or
    // store. We don't want to widen the integer operations only to fail to
    // promote due to some other unsplittable entry (which we may make splittable
    // later). However, if there are only splittable uses, go ahead and assume
    // that we cover the alloca.
    // FIXME: We shouldn't consider split slices that happen to start in the
    // partition here...
    bool WholeAllocaOp =
        P.begin() != P.end() ? false : DL.isLegalInteger(SizeInBits);
  
    for (const Slice &S : P)
      if (!isIntegerWideningViableForSlice(S, P.beginOffset(), AllocaTy, DL,
                                           WholeAllocaOp))
        return false;
  
    for (const Slice *S : P.splitSliceTails())
      if (!isIntegerWideningViableForSlice(*S, P.beginOffset(), AllocaTy, DL,
                                           WholeAllocaOp))
        return false;
  
    return WholeAllocaOp;
  }
  
  static Value *extractInteger(const DataLayout &DL, IRBuilderTy &IRB, Value *V,
                               IntegerType *Ty, uint64_t Offset,
                               const Twine &Name) {
    LLVM_DEBUG(dbgs() << "       start: " << *V << "\n");
    IntegerType *IntTy = cast<IntegerType>(V->getType());
    assert(DL.getTypeStoreSize(Ty) + Offset <= DL.getTypeStoreSize(IntTy) &&
           "Element extends past full value");
    // TVM local begin
    uint64_t ShAmt = ByteSizeInBits * Offset;
    if (DL.isBigEndian())
      ShAmt = ByteSizeInBits *
        (DL.getTypeStoreSize(IntTy) - DL.getTypeStoreSize(Ty) - Offset);
    // TVM local end
    if (ShAmt) {
      V = IRB.CreateLShr(V, ShAmt, Name + ".shift");
      LLVM_DEBUG(dbgs() << "     shifted: " << *V << "\n");
    }
    assert(Ty->getBitWidth() <= IntTy->getBitWidth() &&
           "Cannot extract to a larger integer!");
    if (Ty != IntTy) {
      V = IRB.CreateTrunc(V, Ty, Name + ".trunc");
      LLVM_DEBUG(dbgs() << "     trunced: " << *V << "\n");
    }
    return V;
  }
  
  static Value *insertInteger(const DataLayout &DL, IRBuilderTy &IRB, Value *Old,
                              Value *V, uint64_t Offset, const Twine &Name) {
    IntegerType *IntTy = cast<IntegerType>(Old->getType());
    IntegerType *Ty = cast<IntegerType>(V->getType());
    assert(Ty->getBitWidth() <= IntTy->getBitWidth() &&
           "Cannot insert a larger integer!");
    LLVM_DEBUG(dbgs() << "       start: " << *V << "\n");
    if (Ty != IntTy) {
      V = IRB.CreateZExt(V, IntTy, Name + ".ext");
      LLVM_DEBUG(dbgs() << "    extended: " << *V << "\n");
    }
    assert(DL.getTypeStoreSize(Ty) + Offset <= DL.getTypeStoreSize(IntTy) &&
           "Element store outside of alloca store");
    // TVM local begin
    uint64_t ShAmt = ByteSizeInBits * Offset;
    if (DL.isBigEndian())
      ShAmt = ByteSizeInBits *
        (DL.getTypeStoreSize(IntTy) - DL.getTypeStoreSize(Ty) - Offset);
    // TVM local end
    if (ShAmt) {
      V = IRB.CreateShl(V, ShAmt, Name + ".shift");
      LLVM_DEBUG(dbgs() << "     shifted: " << *V << "\n");
    }
  
    if (ShAmt || Ty->getBitWidth() < IntTy->getBitWidth()) {
      APInt Mask = ~Ty->getMask().zext(IntTy->getBitWidth()).shl(ShAmt);
      Old = IRB.CreateAnd(Old, Mask, Name + ".mask");
      LLVM_DEBUG(dbgs() << "      masked: " << *Old << "\n");
      V = IRB.CreateOr(Old, V, Name + ".insert");
      LLVM_DEBUG(dbgs() << "    inserted: " << *V << "\n");
    }
    return V;
  }
  
  static Value *extractVector(IRBuilderTy &IRB, Value *V, unsigned BeginIndex,
                              unsigned EndIndex, const Twine &Name) {
    VectorType *VecTy = cast<VectorType>(V->getType());
    unsigned NumElements = EndIndex - BeginIndex;
    assert(NumElements <= VecTy->getNumElements() && "Too many elements!");
  
    if (NumElements == VecTy->getNumElements())
      return V;
  
    if (NumElements == 1) {
      V = IRB.CreateExtractElement(V, IRB.getInt32(BeginIndex),
                                   Name + ".extract");
      LLVM_DEBUG(dbgs() << "     extract: " << *V << "\n");
      return V;
    }
  
    SmallVector<Constant *, 8> Mask;
    Mask.reserve(NumElements);
    for (unsigned i = BeginIndex; i != EndIndex; ++i)
      Mask.push_back(IRB.getInt32(i));
    V = IRB.CreateShuffleVector(V, UndefValue::get(V->getType()),
                                ConstantVector::get(Mask), Name + ".extract");
    LLVM_DEBUG(dbgs() << "     shuffle: " << *V << "\n");
    return V;
  }
  
  static Value *insertVector(IRBuilderTy &IRB, Value *Old, Value *V,
                             unsigned BeginIndex, const Twine &Name) {
    VectorType *VecTy = cast<VectorType>(Old->getType());
    assert(VecTy && "Can only insert a vector into a vector");
  
    VectorType *Ty = dyn_cast<VectorType>(V->getType());
    if (!Ty) {
      // Single element to insert.
      V = IRB.CreateInsertElement(Old, V, IRB.getInt32(BeginIndex),
                                  Name + ".insert");
      LLVM_DEBUG(dbgs() << "     insert: " << *V << "\n");
      return V;
    }
  
    assert(Ty->getNumElements() <= VecTy->getNumElements() &&
           "Too many elements!");
    if (Ty->getNumElements() == VecTy->getNumElements()) {
      assert(V->getType() == VecTy && "Vector type mismatch");
      return V;
    }
    unsigned EndIndex = BeginIndex + Ty->getNumElements();
  
    // When inserting a smaller vector into the larger to store, we first
    // use a shuffle vector to widen it with undef elements, and then
    // a second shuffle vector to select between the loaded vector and the
    // incoming vector.
    SmallVector<Constant *, 8> Mask;
    Mask.reserve(VecTy->getNumElements());
    for (unsigned i = 0; i != VecTy->getNumElements(); ++i)
      if (i >= BeginIndex && i < EndIndex)
        Mask.push_back(IRB.getInt32(i - BeginIndex));
      else
        Mask.push_back(UndefValue::get(IRB.getInt32Ty()));
    V = IRB.CreateShuffleVector(V, UndefValue::get(V->getType()),
                                ConstantVector::get(Mask), Name + ".expand");
    LLVM_DEBUG(dbgs() << "    shuffle: " << *V << "\n");
  
    Mask.clear();
    for (unsigned i = 0; i != VecTy->getNumElements(); ++i)
      Mask.push_back(IRB.getInt1(i >= BeginIndex && i < EndIndex));
  
    V = IRB.CreateSelect(ConstantVector::get(Mask), V, Old, Name + "blend");
  
    LLVM_DEBUG(dbgs() << "    blend: " << *V << "\n");
    return V;
  }
  
  /// Visitor to rewrite instructions using p particular slice of an alloca
  /// to use a new alloca.
  ///
  /// Also implements the rewriting to vector-based accesses when the partition
  /// passes the isVectorPromotionViable predicate. Most of the rewriting logic
  /// lives here.
  class llvm::sroa::AllocaSliceRewriter
      : public InstVisitor<AllocaSliceRewriter, bool> {
    // Befriend the base class so it can delegate to private visit methods.
    friend class InstVisitor<AllocaSliceRewriter, bool>;
  
    using Base = InstVisitor<AllocaSliceRewriter, bool>;
  
    const DataLayout &DL;
    AllocaSlices &AS;
    SROA &Pass;
    AllocaInst &OldAI, &NewAI;
    const uint64_t NewAllocaBeginOffset, NewAllocaEndOffset;
    Type *NewAllocaTy;
  
    // This is a convenience and flag variable that will be null unless the new
    // alloca's integer operations should be widened to this integer type due to
    // passing isIntegerWideningViable above. If it is non-null, the desired
    // integer type will be stored here for easy access during rewriting.
    IntegerType *IntTy;
  
    // If we are rewriting an alloca partition which can be written as pure
    // vector operations, we stash extra information here. When VecTy is
    // non-null, we have some strict guarantees about the rewritten alloca:
    //   - The new alloca is exactly the size of the vector type here.
    //   - The accesses all either map to the entire vector or to a single
    //     element.
    //   - The set of accessing instructions is only one of those handled above
    //     in isVectorPromotionViable. Generally these are the same access kinds
    //     which are promotable via mem2reg.
    VectorType *VecTy;
    Type *ElementTy;
    uint64_t ElementSize;
  
    // The original offset of the slice currently being rewritten relative to
    // the original alloca.
    uint64_t BeginOffset = 0;
    uint64_t EndOffset = 0;
  
    // The new offsets of the slice currently being rewritten relative to the
    // original alloca.
    uint64_t NewBeginOffset, NewEndOffset;
  
    uint64_t SliceSize;
    bool IsSplittable = false;
    bool IsSplit = false;
    Use *OldUse = nullptr;
    Instruction *OldPtr = nullptr;
  
    // Track post-rewrite users which are PHI nodes and Selects.
    SmallSetVector<PHINode *, 8> &PHIUsers;
    SmallSetVector<SelectInst *, 8> &SelectUsers;
  
    // Utility IR builder, whose name prefix is setup for each visited use, and
    // the insertion point is set to point to the user.
    IRBuilderTy IRB;
  
  public:
    AllocaSliceRewriter(const DataLayout &DL, AllocaSlices &AS, SROA &Pass,
                        AllocaInst &OldAI, AllocaInst &NewAI,
                        uint64_t NewAllocaBeginOffset,
                        uint64_t NewAllocaEndOffset, bool IsIntegerPromotable,
                        VectorType *PromotableVecTy,
                        SmallSetVector<PHINode *, 8> &PHIUsers,
                        SmallSetVector<SelectInst *, 8> &SelectUsers)
        : DL(DL), AS(AS), Pass(Pass), OldAI(OldAI), NewAI(NewAI),
          NewAllocaBeginOffset(NewAllocaBeginOffset),
          NewAllocaEndOffset(NewAllocaEndOffset),
          NewAllocaTy(NewAI.getAllocatedType()),
          IntTy(IsIntegerPromotable
                    ? Type::getIntNTy(
                          NewAI.getContext(),
                          DL.getTypeSizeInBits(NewAI.getAllocatedType()))
                    : nullptr),
          VecTy(PromotableVecTy),
          ElementTy(VecTy ? VecTy->getElementType() : nullptr),
          // TVM local begin
          ElementSize(VecTy ?
            DL.getTypeSizeInBits(ElementTy) / ByteSizeInBits : 0),
          // TVM local end
          PHIUsers(PHIUsers), SelectUsers(SelectUsers),
          IRB(NewAI.getContext(), ConstantFolder()) {
      if (VecTy) {
        // TVM local begin
        assert((DL.getTypeSizeInBits(ElementTy) % ByteSizeInBits) == 0 &&
               "Only multiple-of-8 sized vector elements are viable");
        // TVM local end
        ++NumVectorized;
      }
      assert((!IntTy && !VecTy) || (IntTy && !VecTy) || (!IntTy && VecTy));
    }
  
    bool visit(AllocaSlices::const_iterator I) {
      bool CanSROA = true;
      BeginOffset = I->beginOffset();
      EndOffset = I->endOffset();
      IsSplittable = I->isSplittable();
      IsSplit =
          BeginOffset < NewAllocaBeginOffset || EndOffset > NewAllocaEndOffset;
      LLVM_DEBUG(dbgs() << "  rewriting " << (IsSplit ? "split " : ""));
      LLVM_DEBUG(AS.printSlice(dbgs(), I, ""));
      LLVM_DEBUG(dbgs() << "\n");
  
      // Compute the intersecting offset range.
      assert(BeginOffset < NewAllocaEndOffset);
      assert(EndOffset > NewAllocaBeginOffset);
      NewBeginOffset = std::max(BeginOffset, NewAllocaBeginOffset);
      NewEndOffset = std::min(EndOffset, NewAllocaEndOffset);
  
      SliceSize = NewEndOffset - NewBeginOffset;
  
      OldUse = I->getUse();
      OldPtr = cast<Instruction>(OldUse->get());
  
      Instruction *OldUserI = cast<Instruction>(OldUse->getUser());
      IRB.SetInsertPoint(OldUserI);
      IRB.SetCurrentDebugLocation(OldUserI->getDebugLoc());
      IRB.SetNamePrefix(Twine(NewAI.getName()) + "." + Twine(BeginOffset) + ".");
  
      CanSROA &= visit(cast<Instruction>(OldUse->getUser()));
      if (VecTy || IntTy)
        assert(CanSROA);
      return CanSROA;
    }
  
  private:
    // Make sure the other visit overloads are visible.
    using Base::visit;
  
    // Every instruction which can end up as a user must have a rewrite rule.
    bool visitInstruction(Instruction &I) {
      LLVM_DEBUG(dbgs() << "    !!!! Cannot rewrite: " << I << "\n");
      llvm_unreachable("No rewrite rule for this instruction!");
    }
  
    Value *getNewAllocaSlicePtr(IRBuilderTy &IRB, Type *PointerTy) {
      // Note that the offset computation can use BeginOffset or NewBeginOffset
      // interchangeably for unsplit slices.
      assert(IsSplit || BeginOffset == NewBeginOffset);
      uint64_t Offset = NewBeginOffset - NewAllocaBeginOffset;
  
  #ifndef NDEBUG
      StringRef OldName = OldPtr->getName();
      // Skip through the last '.sroa.' component of the name.
      size_t LastSROAPrefix = OldName.rfind(".sroa.");
      if (LastSROAPrefix != StringRef::npos) {
        OldName = OldName.substr(LastSROAPrefix + strlen(".sroa."));
        // Look for an SROA slice index.
        size_t IndexEnd = OldName.find_first_not_of("0123456789");
        if (IndexEnd != StringRef::npos && OldName[IndexEnd] == '.') {
          // Strip the index and look for the offset.
          OldName = OldName.substr(IndexEnd + 1);
          size_t OffsetEnd = OldName.find_first_not_of("0123456789");
          if (OffsetEnd != StringRef::npos && OldName[OffsetEnd] == '.')
            // Strip the offset.
            OldName = OldName.substr(OffsetEnd + 1);
        }
      }
      // Strip any SROA suffixes as well.
      OldName = OldName.substr(0, OldName.find(".sroa_"));
  #endif
  
      return getAdjustedPtr(IRB, DL, &NewAI,
                            APInt(DL.getPointerTypeSizeInBits(PointerTy), Offset),
                            PointerTy,
  #ifndef NDEBUG
                            Twine(OldName) + "."
  #else
                            Twine()
  #endif
                            );
    }
  
    /// Compute suitable alignment to access this slice of the *new*
    /// alloca.
    ///
    /// You can optionally pass a type to this routine and if that type's ABI
    /// alignment is itself suitable, this will return zero.
    unsigned getSliceAlign(Type *Ty = nullptr) {
      unsigned NewAIAlign = NewAI.getAlignment();
      if (!NewAIAlign)
        NewAIAlign = DL.getABITypeAlignment(NewAI.getAllocatedType());
      unsigned Align =
          MinAlign(NewAIAlign, NewBeginOffset - NewAllocaBeginOffset);
      return (Ty && Align == DL.getABITypeAlignment(Ty)) ? 0 : Align;
    }
  
    unsigned getIndex(uint64_t Offset) {
      assert(VecTy && "Can only call getIndex when rewriting a vector");
      uint64_t RelOffset = Offset - NewAllocaBeginOffset;
      assert(RelOffset / ElementSize < UINT32_MAX && "Index out of bounds");
      uint32_t Index = RelOffset / ElementSize;
      assert(Index * ElementSize == RelOffset);
      return Index;
    }
  
    void deleteIfTriviallyDead(Value *V) {
      Instruction *I = cast<Instruction>(V);
      if (isInstructionTriviallyDead(I))
        Pass.DeadInsts.insert(I);
    }
  
    Value *rewriteVectorizedLoadInst() {
      unsigned BeginIndex = getIndex(NewBeginOffset);
      unsigned EndIndex = getIndex(NewEndOffset);
      assert(EndIndex > BeginIndex && "Empty vector!");
  
      Value *V = IRB.CreateAlignedLoad(&NewAI, NewAI.getAlignment(), "load");
      return extractVector(IRB, V, BeginIndex, EndIndex, "vec");
    }
  
    Value *rewriteIntegerLoad(LoadInst &LI) {
      assert(IntTy && "We cannot insert an integer to the alloca");
      assert(!LI.isVolatile());
      Value *V = IRB.CreateAlignedLoad(&NewAI, NewAI.getAlignment(), "load");
      V = convertValue(DL, IRB, V, IntTy);
      assert(NewBeginOffset >= NewAllocaBeginOffset && "Out of bounds offset");
      uint64_t Offset = NewBeginOffset - NewAllocaBeginOffset;
      if (Offset > 0 || NewEndOffset < NewAllocaEndOffset) {
        // TVM local begin
        IntegerType *ExtractTy = Type::getIntNTy(
            LI.getContext(), static_cast<unsigned>(SliceSize) * ByteSizeInBits);
        // TVM local end
        V = extractInteger(DL, IRB, V, ExtractTy, Offset, "extract");
      }
      // It is possible that the extracted type is not the load type. This
      // happens if there is a load past the end of the alloca, and as
      // a consequence the slice is narrower but still a candidate for integer
      // lowering. To handle this case, we just zero extend the extracted
      // integer.
      // TVM local begin
      assert((cast<IntegerType>(LI.getType())->getBitWidth() >=
             SliceSize * ByteSizeInBits) &&
             "Can only handle an extract for an overly wide load");
      if (cast<IntegerType>(LI.getType())->getBitWidth() >
          SliceSize * ByteSizeInBits)
        V = IRB.CreateZExt(V, LI.getType());
      // TVM local end
      return V;
    }
  
    bool visitLoadInst(LoadInst &LI) {
      LLVM_DEBUG(dbgs() << "    original: " << LI << "\n");
      Value *OldOp = LI.getOperand(0);
      assert(OldOp == OldPtr);
  
      AAMDNodes AATags;
      LI.getAAMetadata(AATags);
  
      unsigned AS = LI.getPointerAddressSpace();
  
      // TVM local begin
      Type *TargetTy = IsSplit ?
          Type::getIntNTy(LI.getContext(),
                          static_cast<unsigned>(SliceSize) * ByteSizeInBits)
          : LI.getType();
      // TVM local end
      const bool IsLoadPastEnd = DL.getTypeStoreSize(TargetTy) > SliceSize;
      bool IsPtrAdjusted = false;
      Value *V;
      if (VecTy) {
        V = rewriteVectorizedLoadInst();
      } else if (IntTy && LI.getType()->isIntegerTy()) {
        V = rewriteIntegerLoad(LI);
      } else if (NewBeginOffset == NewAllocaBeginOffset &&
                 NewEndOffset == NewAllocaEndOffset &&
                 (canConvertValue(DL, NewAllocaTy, TargetTy) ||
                  (IsLoadPastEnd && NewAllocaTy->isIntegerTy() &&
                   TargetTy->isIntegerTy()))) {
        LoadInst *NewLI = IRB.CreateAlignedLoad(&NewAI, NewAI.getAlignment(),
                                                LI.isVolatile(), LI.getName());
        if (AATags)
          NewLI->setAAMetadata(AATags);
        if (LI.isVolatile())
          NewLI->setAtomic(LI.getOrdering(), LI.getSyncScopeID());
  
        // Any !nonnull metadata or !range metadata on the old load is also valid
        // on the new load. This is even true in some cases even when the loads
        // are different types, for example by mapping !nonnull metadata to
        // !range metadata by modeling the null pointer constant converted to the
        // integer type.
        // FIXME: Add support for range metadata here. Currently the utilities
        // for this don't propagate range metadata in trivial cases from one
        // integer load to another, don't handle non-addrspace-0 null pointers
        // correctly, and don't have any support for mapping ranges as the
        // integer type becomes winder or narrower.
        if (MDNode *N = LI.getMetadata(LLVMContext::MD_nonnull))
          copyNonnullMetadata(LI, N, *NewLI);
  
        // Try to preserve nonnull metadata
        V = NewLI;
  
        // If this is an integer load past the end of the slice (which means the
        // bytes outside the slice are undef or this load is dead) just forcibly
        // fix the integer size with correct handling of endianness.
        if (auto *AITy = dyn_cast<IntegerType>(NewAllocaTy))
          if (auto *TITy = dyn_cast<IntegerType>(TargetTy))
            if (AITy->getBitWidth() < TITy->getBitWidth()) {
              V = IRB.CreateZExt(V, TITy, "load.ext");
              if (DL.isBigEndian())
                V = IRB.CreateShl(V, TITy->getBitWidth() - AITy->getBitWidth(),
                                  "endian_shift");
            }
      } else {
        Type *LTy = TargetTy->getPointerTo(AS);
        LoadInst *NewLI = IRB.CreateAlignedLoad(getNewAllocaSlicePtr(IRB, LTy),
                                                getSliceAlign(TargetTy),
                                                LI.isVolatile(), LI.getName());
        if (AATags)
          NewLI->setAAMetadata(AATags);
        if (LI.isVolatile())
          NewLI->setAtomic(LI.getOrdering(), LI.getSyncScopeID());
  
        V = NewLI;
        IsPtrAdjusted = true;
      }
      V = convertValue(DL, IRB, V, TargetTy);
  
      if (IsSplit) {
        assert(!LI.isVolatile());
        assert(LI.getType()->isIntegerTy() &&
               "Only integer type loads and stores are split");
        assert(SliceSize < DL.getTypeStoreSize(LI.getType()) &&
               "Split load isn't smaller than original load");
        assert(LI.getType()->getIntegerBitWidth() ==
                   DL.getTypeStoreSizeInBits(LI.getType()) &&
               "Non-byte-multiple bit width");
        // Move the insertion point just past the load so that we can refer to it.
        IRB.SetInsertPoint(&*std::next(BasicBlock::iterator(&LI)));
        // Create a placeholder value with the same type as LI to use as the
        // basis for the new value. This allows us to replace the uses of LI with
        // the computed value, and then replace the placeholder with LI, leaving
        // LI only used for this computation.
        Value *Placeholder =
            new LoadInst(UndefValue::get(LI.getType()->getPointerTo(AS)));
        V = insertInteger(DL, IRB, Placeholder, V, NewBeginOffset - BeginOffset,
                          "insert");
        LI.replaceAllUsesWith(V);
        Placeholder->replaceAllUsesWith(&LI);
        Placeholder->deleteValue();
      } else {
        LI.replaceAllUsesWith(V);
      }
  
      Pass.DeadInsts.insert(&LI);
      deleteIfTriviallyDead(OldOp);
      LLVM_DEBUG(dbgs() << "          to: " << *V << "\n");
      return !LI.isVolatile() && !IsPtrAdjusted;
    }
  
    bool rewriteVectorizedStoreInst(Value *V, StoreInst &SI, Value *OldOp,
                                    AAMDNodes AATags) {
      if (V->getType() != VecTy) {
        unsigned BeginIndex = getIndex(NewBeginOffset);
        unsigned EndIndex = getIndex(NewEndOffset);
        assert(EndIndex > BeginIndex && "Empty vector!");
        unsigned NumElements = EndIndex - BeginIndex;
        assert(NumElements <= VecTy->getNumElements() && "Too many elements!");
        Type *SliceTy = (NumElements == 1)
                            ? ElementTy
                            : VectorType::get(ElementTy, NumElements);
        if (V->getType() != SliceTy)
          V = convertValue(DL, IRB, V, SliceTy);
  
        // Mix in the existing elements.
        Value *Old = IRB.CreateAlignedLoad(&NewAI, NewAI.getAlignment(), "load");
        V = insertVector(IRB, Old, V, BeginIndex, "vec");
      }
      StoreInst *Store = IRB.CreateAlignedStore(V, &NewAI, NewAI.getAlignment());
      if (AATags)
        Store->setAAMetadata(AATags);
      Pass.DeadInsts.insert(&SI);
  
      LLVM_DEBUG(dbgs() << "          to: " << *Store << "\n");
      return true;
    }
  
    bool rewriteIntegerStore(Value *V, StoreInst &SI, AAMDNodes AATags) {
      assert(IntTy && "We cannot extract an integer from the alloca");
      assert(!SI.isVolatile());
      if (DL.getTypeSizeInBits(V->getType()) != IntTy->getBitWidth()) {
        Value *Old =
            IRB.CreateAlignedLoad(&NewAI, NewAI.getAlignment(), "oldload");
        Old = convertValue(DL, IRB, Old, IntTy);
        assert(BeginOffset >= NewAllocaBeginOffset && "Out of bounds offset");
        uint64_t Offset = BeginOffset - NewAllocaBeginOffset;
        V = insertInteger(DL, IRB, Old, SI.getValueOperand(), Offset, "insert");
      }
      V = convertValue(DL, IRB, V, NewAllocaTy);
      StoreInst *Store = IRB.CreateAlignedStore(V, &NewAI, NewAI.getAlignment());
      Store->copyMetadata(SI, LLVMContext::MD_mem_parallel_loop_access);
      if (AATags)
        Store->setAAMetadata(AATags);
      Pass.DeadInsts.insert(&SI);
      LLVM_DEBUG(dbgs() << "          to: " << *Store << "\n");
      return true;
    }
  
    bool visitStoreInst(StoreInst &SI) {
      LLVM_DEBUG(dbgs() << "    original: " << SI << "\n");
      Value *OldOp = SI.getOperand(1);
      assert(OldOp == OldPtr);
  
      AAMDNodes AATags;
      SI.getAAMetadata(AATags);
  
      Value *V = SI.getValueOperand();
  
      // Strip all inbounds GEPs and pointer casts to try to dig out any root
      // alloca that should be re-examined after promoting this alloca.
      if (V->getType()->isPointerTy())
        if (AllocaInst *AI = dyn_cast<AllocaInst>(V->stripInBoundsOffsets()))
          Pass.PostPromotionWorklist.insert(AI);
  
      if (SliceSize < DL.getTypeStoreSize(V->getType())) {
        assert(!SI.isVolatile());
        assert(V->getType()->isIntegerTy() &&
               "Only integer type loads and stores are split");
        assert(V->getType()->getIntegerBitWidth() ==
                   DL.getTypeStoreSizeInBits(V->getType()) &&
               "Non-byte-multiple bit width");
        // TVM local begin
        IntegerType *NarrowTy = Type::getIntNTy(
            SI.getContext(), static_cast<unsigned>(SliceSize) * ByteSizeInBits);
        // TVM local end
        V = extractInteger(DL, IRB, V, NarrowTy, NewBeginOffset - BeginOffset,
                           "extract");
      }
  
      if (VecTy)
        return rewriteVectorizedStoreInst(V, SI, OldOp, AATags);
      if (IntTy && V->getType()->isIntegerTy())
        return rewriteIntegerStore(V, SI, AATags);
  
      const bool IsStorePastEnd = DL.getTypeStoreSize(V->getType()) > SliceSize;
      StoreInst *NewSI;
      if (NewBeginOffset == NewAllocaBeginOffset &&
          NewEndOffset == NewAllocaEndOffset &&
          (canConvertValue(DL, V->getType(), NewAllocaTy) ||
           (IsStorePastEnd && NewAllocaTy->isIntegerTy() &&
            V->getType()->isIntegerTy()))) {
        // If this is an integer store past the end of slice (and thus the bytes
        // past that point are irrelevant or this is unreachable), truncate the
        // value prior to storing.
        if (auto *VITy = dyn_cast<IntegerType>(V->getType()))
          if (auto *AITy = dyn_cast<IntegerType>(NewAllocaTy))
            if (VITy->getBitWidth() > AITy->getBitWidth()) {
              if (DL.isBigEndian())
                V = IRB.CreateLShr(V, VITy->getBitWidth() - AITy->getBitWidth(),
                                   "endian_shift");
              V = IRB.CreateTrunc(V, AITy, "load.trunc");
            }
  
        V = convertValue(DL, IRB, V, NewAllocaTy);
        NewSI = IRB.CreateAlignedStore(V, &NewAI, NewAI.getAlignment(),
                                       SI.isVolatile());
      } else {
        unsigned AS = SI.getPointerAddressSpace();
        Value *NewPtr = getNewAllocaSlicePtr(IRB, V->getType()->getPointerTo(AS));
        NewSI = IRB.CreateAlignedStore(V, NewPtr, getSliceAlign(V->getType()),
                                       SI.isVolatile());
      }
      NewSI->copyMetadata(SI, LLVMContext::MD_mem_parallel_loop_access);
      if (AATags)
        NewSI->setAAMetadata(AATags);
      if (SI.isVolatile())
        NewSI->setAtomic(SI.getOrdering(), SI.getSyncScopeID());
      Pass.DeadInsts.insert(&SI);
      deleteIfTriviallyDead(OldOp);
  
      LLVM_DEBUG(dbgs() << "          to: " << *NewSI << "\n");
      return NewSI->getPointerOperand() == &NewAI && !SI.isVolatile();
    }
  
    /// Compute an integer value from splatting an i8 across the given
    /// number of bytes.
    ///
    /// Note that this routine assumes an i8 is a byte. If that isn't true, don't
    /// call this routine.
    /// FIXME: Heed the advice above.
    ///
    /// \param V The i8 value to splat.
    /// \param Size The number of bytes in the output (assuming i8 is one byte)
    Value *getIntegerSplat(Value *V, unsigned Size) {
      assert(Size > 0 && "Expected a positive number of bytes.");
      IntegerType *VTy = cast<IntegerType>(V->getType());
      // TVM local begin
      assert(VTy->getBitWidth() == ByteSizeInBits
             && "Expected an i8 value for the byte");
      // TVM local end
      if (Size == 1)
        return V;
  
      // TVM local begin
      Type *SplatIntTy = Type::getIntNTy(VTy->getContext(),
                                         Size * ByteSizeInBits);
      // TVM local end
      V = IRB.CreateMul(
          IRB.CreateZExt(V, SplatIntTy, "zext"),
          ConstantExpr::getUDiv(
              Constant::getAllOnesValue(SplatIntTy),
              ConstantExpr::getZExt(Constant::getAllOnesValue(V->getType()),
                                    SplatIntTy)),
          "isplat");
      return V;
    }
  
    /// Compute a vector splat for a given element value.
    Value *getVectorSplat(Value *V, unsigned NumElements) {
      V = IRB.CreateVectorSplat(NumElements, V, "vsplat");
      LLVM_DEBUG(dbgs() << "       splat: " << *V << "\n");
      return V;
    }
  
    bool visitMemSetInst(MemSetInst &II) {
      LLVM_DEBUG(dbgs() << "    original: " << II << "\n");
      assert(II.getRawDest() == OldPtr);
  
      AAMDNodes AATags;
      II.getAAMetadata(AATags);
  
      // If the memset has a variable size, it cannot be split, just adjust the
      // pointer to the new alloca.
      if (!isa<Constant>(II.getLength())) {
        assert(!IsSplit);
        assert(NewBeginOffset == BeginOffset);
        II.setDest(getNewAllocaSlicePtr(IRB, OldPtr->getType()));
        II.setDestAlignment(getSliceAlign());
  
        deleteIfTriviallyDead(OldPtr);
        return false;
      }
  
      // Record this instruction for deletion.
      Pass.DeadInsts.insert(&II);
  
      Type *AllocaTy = NewAI.getAllocatedType();
      Type *ScalarTy = AllocaTy->getScalarType();
  
      // If this doesn't map cleanly onto the alloca type, and that type isn't
      // a single value type, just emit a memset.
      if (!VecTy && !IntTy &&
          (BeginOffset > NewAllocaBeginOffset || EndOffset < NewAllocaEndOffset ||
           SliceSize != DL.getTypeStoreSize(AllocaTy) ||
           !AllocaTy->isSingleValueType() ||
           !DL.isLegalInteger(DL.getTypeSizeInBits(ScalarTy)) ||
        // TVM local begin
           DL.getTypeSizeInBits(ScalarTy) % ByteSizeInBits != 0)) {
        // TVM local end
        Type *SizeTy = II.getLength()->getType();
        Constant *Size = ConstantInt::get(SizeTy, NewEndOffset - NewBeginOffset);
        CallInst *New = IRB.CreateMemSet(
            getNewAllocaSlicePtr(IRB, OldPtr->getType()), II.getValue(), Size,
            getSliceAlign(), II.isVolatile());
        if (AATags)
          New->setAAMetadata(AATags);
        LLVM_DEBUG(dbgs() << "          to: " << *New << "\n");
        return false;
      }
  
      // If we can represent this as a simple value, we have to build the actual
      // value to store, which requires expanding the byte present in memset to
      // a sensible representation for the alloca type. This is essentially
      // splatting the byte to a sufficiently wide integer, splatting it across
      // any desired vector width, and bitcasting to the final type.
      Value *V;
  
      if (VecTy) {
        // If this is a memset of a vectorized alloca, insert it.
        assert(ElementTy == ScalarTy);
  
        unsigned BeginIndex = getIndex(NewBeginOffset);
        unsigned EndIndex = getIndex(NewEndOffset);
        assert(EndIndex > BeginIndex && "Empty vector!");
        unsigned NumElements = EndIndex - BeginIndex;
        assert(NumElements <= VecTy->getNumElements() && "Too many elements!");
  
        // TVM local begin
        Value *Splat =
            getIntegerSplat(II.getValue(),
                            DL.getTypeSizeInBits(ElementTy) / ByteSizeInBits);
        // TVM local end
        Splat = convertValue(DL, IRB, Splat, ElementTy);
        if (NumElements > 1)
          Splat = getVectorSplat(Splat, NumElements);
  
        Value *Old =
            IRB.CreateAlignedLoad(&NewAI, NewAI.getAlignment(), "oldload");
        V = insertVector(IRB, Old, Splat, BeginIndex, "vec");
      } else if (IntTy) {
        // If this is a memset on an alloca where we can widen stores, insert the
        // set integer.
        assert(!II.isVolatile());
  
        uint64_t Size = NewEndOffset - NewBeginOffset;
        V = getIntegerSplat(II.getValue(), Size);
  
        if (IntTy && (BeginOffset != NewAllocaBeginOffset ||
                      EndOffset != NewAllocaBeginOffset)) {
          Value *Old =
              IRB.CreateAlignedLoad(&NewAI, NewAI.getAlignment(), "oldload");
          Old = convertValue(DL, IRB, Old, IntTy);
          uint64_t Offset = NewBeginOffset - NewAllocaBeginOffset;
          V = insertInteger(DL, IRB, Old, V, Offset, "insert");
        } else {
          assert(V->getType() == IntTy &&
                 "Wrong type for an alloca wide integer!");
        }
        V = convertValue(DL, IRB, V, AllocaTy);
      } else {
        // Established these invariants above.
        assert(NewBeginOffset == NewAllocaBeginOffset);
        assert(NewEndOffset == NewAllocaEndOffset);
  
        // TVM local begin
        V = getIntegerSplat(II.getValue(),
                            DL.getTypeSizeInBits(ScalarTy) / ByteSizeInBits);
        // TVM local end
        if (VectorType *AllocaVecTy = dyn_cast<VectorType>(AllocaTy))
          V = getVectorSplat(V, AllocaVecTy->getNumElements());
  
        V = convertValue(DL, IRB, V, AllocaTy);
      }
  
      StoreInst *New = IRB.CreateAlignedStore(V, &NewAI, NewAI.getAlignment(),
                                              II.isVolatile());
      if (AATags)
        New->setAAMetadata(AATags);
      LLVM_DEBUG(dbgs() << "          to: " << *New << "\n");
      return !II.isVolatile();
    }
  
    bool visitMemTransferInst(MemTransferInst &II) {
      // Rewriting of memory transfer instructions can be a bit tricky. We break
      // them into two categories: split intrinsics and unsplit intrinsics.
  
      LLVM_DEBUG(dbgs() << "    original: " << II << "\n");
  
      AAMDNodes AATags;
      II.getAAMetadata(AATags);
  
      bool IsDest = &II.getRawDestUse() == OldUse;
      assert((IsDest && II.getRawDest() == OldPtr) ||
             (!IsDest && II.getRawSource() == OldPtr));
  
      unsigned SliceAlign = getSliceAlign();
  
      // For unsplit intrinsics, we simply modify the source and destination
      // pointers in place. This isn't just an optimization, it is a matter of
      // correctness. With unsplit intrinsics we may be dealing with transfers
      // within a single alloca before SROA ran, or with transfers that have
      // a variable length. We may also be dealing with memmove instead of
      // memcpy, and so simply updating the pointers is the necessary for us to
      // update both source and dest of a single call.
      if (!IsSplittable) {
        Value *AdjustedPtr = getNewAllocaSlicePtr(IRB, OldPtr->getType());
        if (IsDest) {
          II.setDest(AdjustedPtr);
          II.setDestAlignment(SliceAlign);
        }
        else {
          II.setSource(AdjustedPtr);
          II.setSourceAlignment(SliceAlign);
        }
  
        LLVM_DEBUG(dbgs() << "          to: " << II << "\n");
        deleteIfTriviallyDead(OldPtr);
        return false;
      }
      // For split transfer intrinsics we have an incredibly useful assurance:
      // the source and destination do not reside within the same alloca, and at
      // least one of them does not escape. This means that we can replace
      // memmove with memcpy, and we don't need to worry about all manner of
      // downsides to splitting and transforming the operations.
  
      // If this doesn't map cleanly onto the alloca type, and that type isn't
      // a single value type, just emit a memcpy.
      bool EmitMemCpy =
          !VecTy && !IntTy &&
          (BeginOffset > NewAllocaBeginOffset || EndOffset < NewAllocaEndOffset ||
           SliceSize != DL.getTypeStoreSize(NewAI.getAllocatedType()) ||
           !NewAI.getAllocatedType()->isSingleValueType());
  
      // If we're just going to emit a memcpy, the alloca hasn't changed, and the
      // size hasn't been shrunk based on analysis of the viable range, this is
      // a no-op.
      if (EmitMemCpy && &OldAI == &NewAI) {
        // Ensure the start lines up.
        assert(NewBeginOffset == BeginOffset);
  
        // Rewrite the size as needed.
        if (NewEndOffset != EndOffset)
          II.setLength(ConstantInt::get(II.getLength()->getType(),
                                        NewEndOffset - NewBeginOffset));
        return false;
      }
      // Record this instruction for deletion.
      Pass.DeadInsts.insert(&II);
  
      // Strip all inbounds GEPs and pointer casts to try to dig out any root
      // alloca that should be re-examined after rewriting this instruction.
      Value *OtherPtr = IsDest ? II.getRawSource() : II.getRawDest();
      if (AllocaInst *AI =
              dyn_cast<AllocaInst>(OtherPtr->stripInBoundsOffsets())) {
        assert(AI != &OldAI && AI != &NewAI &&
               "Splittable transfers cannot reach the same alloca on both ends.");
        Pass.Worklist.insert(AI);
      }
  
      Type *OtherPtrTy = OtherPtr->getType();
      unsigned OtherAS = OtherPtrTy->getPointerAddressSpace();
  
      // Compute the relative offset for the other pointer within the transfer.
      unsigned IntPtrWidth = DL.getPointerSizeInBits(OtherAS);
      APInt OtherOffset(IntPtrWidth, NewBeginOffset - BeginOffset);
      unsigned OtherAlign =
        IsDest ? II.getSourceAlignment() : II.getDestAlignment();
      OtherAlign =  MinAlign(OtherAlign ? OtherAlign : 1,
                             OtherOffset.zextOrTrunc(64).getZExtValue());
  
      if (EmitMemCpy) {
        // Compute the other pointer, folding as much as possible to produce
        // a single, simple GEP in most cases.
        OtherPtr = getAdjustedPtr(IRB, DL, OtherPtr, OtherOffset, OtherPtrTy,
                                  OtherPtr->getName() + ".");
  
        Value *OurPtr = getNewAllocaSlicePtr(IRB, OldPtr->getType());
        Type *SizeTy = II.getLength()->getType();
        Constant *Size = ConstantInt::get(SizeTy, NewEndOffset - NewBeginOffset);
  
        Value *DestPtr, *SrcPtr;
        unsigned DestAlign, SrcAlign;
        // Note: IsDest is true iff we're copying into the new alloca slice
        if (IsDest) {
          DestPtr = OurPtr;
          DestAlign = SliceAlign;
          SrcPtr = OtherPtr;
          SrcAlign = OtherAlign;
        } else {
          DestPtr = OtherPtr;
          DestAlign = OtherAlign;
          SrcPtr = OurPtr;
          SrcAlign = SliceAlign;
        }
        CallInst *New = IRB.CreateMemCpy(DestPtr, DestAlign, SrcPtr, SrcAlign,
                                         Size, II.isVolatile());
        if (AATags)
          New->setAAMetadata(AATags);
        LLVM_DEBUG(dbgs() << "          to: " << *New << "\n");
        return false;
      }
  
      bool IsWholeAlloca = NewBeginOffset == NewAllocaBeginOffset &&
                           NewEndOffset == NewAllocaEndOffset;
      uint64_t Size = NewEndOffset - NewBeginOffset;
      unsigned BeginIndex = VecTy ? getIndex(NewBeginOffset) : 0;
      unsigned EndIndex = VecTy ? getIndex(NewEndOffset) : 0;
      unsigned NumElements = EndIndex - BeginIndex;
      // TVM local begin
      IntegerType *SubIntTy =
          IntTy ? Type::getIntNTy(IntTy->getContext(),
                                  Size * ByteSizeInBits) : nullptr;
      // TVM local end
  
      // Reset the other pointer type to match the register type we're going to
      // use, but using the address space of the original other pointer.
      if (VecTy && !IsWholeAlloca) {
        if (NumElements == 1)
          OtherPtrTy = VecTy->getElementType();
        else
          OtherPtrTy = VectorType::get(VecTy->getElementType(), NumElements);
  
        OtherPtrTy = OtherPtrTy->getPointerTo(OtherAS);
      } else if (IntTy && !IsWholeAlloca) {
        OtherPtrTy = SubIntTy->getPointerTo(OtherAS);
      } else {
        OtherPtrTy = NewAllocaTy->getPointerTo(OtherAS);
      }
  
      Value *SrcPtr = getAdjustedPtr(IRB, DL, OtherPtr, OtherOffset, OtherPtrTy,
                                     OtherPtr->getName() + ".");
      unsigned SrcAlign = OtherAlign;
      Value *DstPtr = &NewAI;
      unsigned DstAlign = SliceAlign;
      if (!IsDest) {
        std::swap(SrcPtr, DstPtr);
        std::swap(SrcAlign, DstAlign);
      }
  
      Value *Src;
      if (VecTy && !IsWholeAlloca && !IsDest) {
        Src = IRB.CreateAlignedLoad(&NewAI, NewAI.getAlignment(), "load");
        Src = extractVector(IRB, Src, BeginIndex, EndIndex, "vec");
      } else if (IntTy && !IsWholeAlloca && !IsDest) {
        Src = IRB.CreateAlignedLoad(&NewAI, NewAI.getAlignment(), "load");
        Src = convertValue(DL, IRB, Src, IntTy);
        uint64_t Offset = NewBeginOffset - NewAllocaBeginOffset;
        Src = extractInteger(DL, IRB, Src, SubIntTy, Offset, "extract");
      } else {
        LoadInst *Load = IRB.CreateAlignedLoad(SrcPtr, SrcAlign, II.isVolatile(),
                                               "copyload");
        if (AATags)
          Load->setAAMetadata(AATags);
        Src = Load;
      }
  
      if (VecTy && !IsWholeAlloca && IsDest) {
        Value *Old =
            IRB.CreateAlignedLoad(&NewAI, NewAI.getAlignment(), "oldload");
        Src = insertVector(IRB, Old, Src, BeginIndex, "vec");
      } else if (IntTy && !IsWholeAlloca && IsDest) {
        Value *Old =
            IRB.CreateAlignedLoad(&NewAI, NewAI.getAlignment(), "oldload");
        Old = convertValue(DL, IRB, Old, IntTy);
        uint64_t Offset = NewBeginOffset - NewAllocaBeginOffset;
        Src = insertInteger(DL, IRB, Old, Src, Offset, "insert");
        Src = convertValue(DL, IRB, Src, NewAllocaTy);
      }
  
      StoreInst *Store = cast<StoreInst>(
          IRB.CreateAlignedStore(Src, DstPtr, DstAlign, II.isVolatile()));
      if (AATags)
        Store->setAAMetadata(AATags);
      LLVM_DEBUG(dbgs() << "          to: " << *Store << "\n");
      return !II.isVolatile();
    }
  
    bool visitIntrinsicInst(IntrinsicInst &II) {
      assert(II.getIntrinsicID() == Intrinsic::lifetime_start ||
             II.getIntrinsicID() == Intrinsic::lifetime_end);
      LLVM_DEBUG(dbgs() << "    original: " << II << "\n");
      assert(II.getArgOperand(1) == OldPtr);
  
      // Record this instruction for deletion.
      Pass.DeadInsts.insert(&II);
  
      // Lifetime intrinsics are only promotable if they cover the whole alloca.
      // Therefore, we drop lifetime intrinsics which don't cover the whole
      // alloca.
      // (In theory, intrinsics which partially cover an alloca could be
      // promoted, but PromoteMemToReg doesn't handle that case.)
      // FIXME: Check whether the alloca is promotable before dropping the
      // lifetime intrinsics?
      if (NewBeginOffset != NewAllocaBeginOffset ||
          NewEndOffset != NewAllocaEndOffset)
        return true;
  
      ConstantInt *Size =
          ConstantInt::get(cast<IntegerType>(II.getArgOperand(0)->getType()),
                           NewEndOffset - NewBeginOffset);
      Value *Ptr = getNewAllocaSlicePtr(IRB, OldPtr->getType());
      Value *New;
      if (II.getIntrinsicID() == Intrinsic::lifetime_start)
        New = IRB.CreateLifetimeStart(Ptr, Size);
      else
        New = IRB.CreateLifetimeEnd(Ptr, Size);
  
      (void)New;
      LLVM_DEBUG(dbgs() << "          to: " << *New << "\n");
  
      return true;
    }
  
    void fixLoadStoreAlign(Instruction &Root) {
      // This algorithm implements the same visitor loop as
      // hasUnsafePHIOrSelectUse, and fixes the alignment of each load
      // or store found.
      SmallPtrSet<Instruction *, 4> Visited;
      SmallVector<Instruction *, 4> Uses;
      Visited.insert(&Root);
      Uses.push_back(&Root);
      do {
        Instruction *I = Uses.pop_back_val();
  
        if (LoadInst *LI = dyn_cast<LoadInst>(I)) {
          unsigned LoadAlign = LI->getAlignment();
          if (!LoadAlign)
            LoadAlign = DL.getABITypeAlignment(LI->getType());
          LI->setAlignment(std::min(LoadAlign, getSliceAlign()));
          continue;
        }
        if (StoreInst *SI = dyn_cast<StoreInst>(I)) {
          unsigned StoreAlign = SI->getAlignment();
          if (!StoreAlign) {
            Value *Op = SI->getOperand(0);
            StoreAlign = DL.getABITypeAlignment(Op->getType());
          }
          SI->setAlignment(std::min(StoreAlign, getSliceAlign()));
          continue;
        }
  
        assert(isa<BitCastInst>(I) || isa<PHINode>(I) ||
               isa<SelectInst>(I) || isa<GetElementPtrInst>(I));
        for (User *U : I->users())
          if (Visited.insert(cast<Instruction>(U)).second)
            Uses.push_back(cast<Instruction>(U));
      } while (!Uses.empty());
    }
  
    bool visitPHINode(PHINode &PN) {
      LLVM_DEBUG(dbgs() << "    original: " << PN << "\n");
      assert(BeginOffset >= NewAllocaBeginOffset && "PHIs are unsplittable");
      assert(EndOffset <= NewAllocaEndOffset && "PHIs are unsplittable");
  
      // We would like to compute a new pointer in only one place, but have it be
      // as local as possible to the PHI. To do that, we re-use the location of
      // the old pointer, which necessarily must be in the right position to
      // dominate the PHI.
      IRBuilderTy PtrBuilder(IRB);
      if (isa<PHINode>(OldPtr))
        PtrBuilder.SetInsertPoint(&*OldPtr->getParent()->getFirstInsertionPt());
      else
        PtrBuilder.SetInsertPoint(OldPtr);
      PtrBuilder.SetCurrentDebugLocation(OldPtr->getDebugLoc());
  
      Value *NewPtr = getNewAllocaSlicePtr(PtrBuilder, OldPtr->getType());
      // Replace the operands which were using the old pointer.
      std::replace(PN.op_begin(), PN.op_end(), cast<Value>(OldPtr), NewPtr);
  
      LLVM_DEBUG(dbgs() << "          to: " << PN << "\n");
      deleteIfTriviallyDead(OldPtr);
  
      // Fix the alignment of any loads or stores using this PHI node.
      fixLoadStoreAlign(PN);
  
      // PHIs can't be promoted on their own, but often can be speculated. We
      // check the speculation outside of the rewriter so that we see the
      // fully-rewritten alloca.
      PHIUsers.insert(&PN);
      return true;
    }
  
    bool visitSelectInst(SelectInst &SI) {
      LLVM_DEBUG(dbgs() << "    original: " << SI << "\n");
      assert((SI.getTrueValue() == OldPtr || SI.getFalseValue() == OldPtr) &&
             "Pointer isn't an operand!");
      assert(BeginOffset >= NewAllocaBeginOffset && "Selects are unsplittable");
      assert(EndOffset <= NewAllocaEndOffset && "Selects are unsplittable");
  
      Value *NewPtr = getNewAllocaSlicePtr(IRB, OldPtr->getType());
      // Replace the operands which were using the old pointer.
      if (SI.getOperand(1) == OldPtr)
        SI.setOperand(1, NewPtr);
      if (SI.getOperand(2) == OldPtr)
        SI.setOperand(2, NewPtr);
  
      LLVM_DEBUG(dbgs() << "          to: " << SI << "\n");
      deleteIfTriviallyDead(OldPtr);
  
      // Fix the alignment of any loads or stores using this select.
      fixLoadStoreAlign(SI);
  
      // Selects can't be promoted on their own, but often can be speculated. We
      // check the speculation outside of the rewriter so that we see the
      // fully-rewritten alloca.
      SelectUsers.insert(&SI);
      return true;
    }
  };
  
  namespace {
  
  /// Visitor to rewrite aggregate loads and stores as scalar.
  ///
  /// This pass aggressively rewrites all aggregate loads and stores on
  /// a particular pointer (or any pointer derived from it which we can identify)
  /// with scalar loads and stores.
  class AggLoadStoreRewriter : public InstVisitor<AggLoadStoreRewriter, bool> {
    // Befriend the base class so it can delegate to private visit methods.
    friend class InstVisitor<AggLoadStoreRewriter, bool>;
  
    /// Queue of pointer uses to analyze and potentially rewrite.
    SmallVector<Use *, 8> Queue;
  
    /// Set to prevent us from cycling with phi nodes and loops.
    SmallPtrSet<User *, 8> Visited;
  
    /// The current pointer use being rewritten. This is used to dig up the used
    /// value (as opposed to the user).
    Use *U;
  
  public:
    /// Rewrite loads and stores through a pointer and all pointers derived from
    /// it.
    bool rewrite(Instruction &I) {
      LLVM_DEBUG(dbgs() << "  Rewriting FCA loads and stores...\n");
      enqueueUsers(I);
      bool Changed = false;
      while (!Queue.empty()) {
        U = Queue.pop_back_val();
        Changed |= visit(cast<Instruction>(U->getUser()));
      }
      return Changed;
    }
  
  private:
    /// Enqueue all the users of the given instruction for further processing.
    /// This uses a set to de-duplicate users.
    void enqueueUsers(Instruction &I) {
      for (Use &U : I.uses())
        if (Visited.insert(U.getUser()).second)
          Queue.push_back(&U);
    }
  
    // Conservative default is to not rewrite anything.
    bool visitInstruction(Instruction &I) { return false; }
  
    /// Generic recursive split emission class.
    template <typename Derived> class OpSplitter {
    protected:
      /// The builder used to form new instructions.
      IRBuilderTy IRB;
  
      /// The indices which to be used with insert- or extractvalue to select the
      /// appropriate value within the aggregate.
      SmallVector<unsigned, 4> Indices;
  
      /// The indices to a GEP instruction which will move Ptr to the correct slot
      /// within the aggregate.
      SmallVector<Value *, 4> GEPIndices;
  
      /// The base pointer of the original op, used as a base for GEPing the
      /// split operations.
      Value *Ptr;
  
      /// Initialize the splitter with an insertion point, Ptr and start with a
      /// single zero GEP index.
      OpSplitter(Instruction *InsertionPoint, Value *Ptr)
          : IRB(InsertionPoint), GEPIndices(1, IRB.getInt32(0)), Ptr(Ptr) {}
  
    public:
      /// Generic recursive split emission routine.
      ///
      /// This method recursively splits an aggregate op (load or store) into
      /// scalar or vector ops. It splits recursively until it hits a single value
      /// and emits that single value operation via the template argument.
      ///
      /// The logic of this routine relies on GEPs and insertvalue and
      /// extractvalue all operating with the same fundamental index list, merely
      /// formatted differently (GEPs need actual values).
      ///
      /// \param Ty  The type being split recursively into smaller ops.
      /// \param Agg The aggregate value being built up or stored, depending on
      /// whether this is splitting a load or a store respectively.
      void emitSplitOps(Type *Ty, Value *&Agg, const Twine &Name) {
        if (Ty->isSingleValueType())
          return static_cast<Derived *>(this)->emitFunc(Ty, Agg, Name);
  
        if (ArrayType *ATy = dyn_cast<ArrayType>(Ty)) {
          unsigned OldSize = Indices.size();
          (void)OldSize;
          for (unsigned Idx = 0, Size = ATy->getNumElements(); Idx != Size;
               ++Idx) {
            assert(Indices.size() == OldSize && "Did not return to the old size");
            Indices.push_back(Idx);
            GEPIndices.push_back(IRB.getInt32(Idx));
            emitSplitOps(ATy->getElementType(), Agg, Name + "." + Twine(Idx));
            GEPIndices.pop_back();
            Indices.pop_back();
          }
          return;
        }
  
        if (StructType *STy = dyn_cast<StructType>(Ty)) {
          unsigned OldSize = Indices.size();
          (void)OldSize;
          for (unsigned Idx = 0, Size = STy->getNumElements(); Idx != Size;
               ++Idx) {
            assert(Indices.size() == OldSize && "Did not return to the old size");
            Indices.push_back(Idx);
            GEPIndices.push_back(IRB.getInt32(Idx));
            emitSplitOps(STy->getElementType(Idx), Agg, Name + "." + Twine(Idx));
            GEPIndices.pop_back();
            Indices.pop_back();
          }
          return;
        }
  
        llvm_unreachable("Only arrays and structs are aggregate loadable types");
      }
    };
  
    struct LoadOpSplitter : public OpSplitter<LoadOpSplitter> {
      AAMDNodes AATags;
  
      LoadOpSplitter(Instruction *InsertionPoint, Value *Ptr, AAMDNodes AATags)
          : OpSplitter<LoadOpSplitter>(InsertionPoint, Ptr), AATags(AATags) {}
  
      /// Emit a leaf load of a single value. This is called at the leaves of the
      /// recursive emission to actually load values.
      void emitFunc(Type *Ty, Value *&Agg, const Twine &Name) {
        assert(Ty->isSingleValueType());
        // Load the single value and insert it using the indices.
        Value *GEP =
            IRB.CreateInBoundsGEP(nullptr, Ptr, GEPIndices, Name + ".gep");
        LoadInst *Load = IRB.CreateLoad(GEP, Name + ".load");
        if (AATags)
          Load->setAAMetadata(AATags);
        Agg = IRB.CreateInsertValue(Agg, Load, Indices, Name + ".insert");
        LLVM_DEBUG(dbgs() << "          to: " << *Load << "\n");
      }
    };
  
    bool visitLoadInst(LoadInst &LI) {
      assert(LI.getPointerOperand() == *U);
      if (!LI.isSimple() || LI.getType()->isSingleValueType())
        return false;
  
      // We have an aggregate being loaded, split it apart.
      LLVM_DEBUG(dbgs() << "    original: " << LI << "\n");
      AAMDNodes AATags;
      LI.getAAMetadata(AATags);
      LoadOpSplitter Splitter(&LI, *U, AATags);
      Value *V = UndefValue::get(LI.getType());
      Splitter.emitSplitOps(LI.getType(), V, LI.getName() + ".fca");
      LI.replaceAllUsesWith(V);
      LI.eraseFromParent();
      return true;
    }
  
    struct StoreOpSplitter : public OpSplitter<StoreOpSplitter> {
      StoreOpSplitter(Instruction *InsertionPoint, Value *Ptr, AAMDNodes AATags)
          : OpSplitter<StoreOpSplitter>(InsertionPoint, Ptr), AATags(AATags) {}
      AAMDNodes AATags;
  
      /// Emit a leaf store of a single value. This is called at the leaves of the
      /// recursive emission to actually produce stores.
      void emitFunc(Type *Ty, Value *&Agg, const Twine &Name) {
        assert(Ty->isSingleValueType());
        // Extract the single value and store it using the indices.
        //
        // The gep and extractvalue values are factored out of the CreateStore
        // call to make the output independent of the argument evaluation order.
        Value *ExtractValue =
            IRB.CreateExtractValue(Agg, Indices, Name + ".extract");
        Value *InBoundsGEP =
            IRB.CreateInBoundsGEP(nullptr, Ptr, GEPIndices, Name + ".gep");
        StoreInst *Store = IRB.CreateStore(ExtractValue, InBoundsGEP);
        if (AATags)
          Store->setAAMetadata(AATags);
        LLVM_DEBUG(dbgs() << "          to: " << *Store << "\n");
      }
    };
  
    bool visitStoreInst(StoreInst &SI) {
      if (!SI.isSimple() || SI.getPointerOperand() != *U)
        return false;
      Value *V = SI.getValueOperand();
      if (V->getType()->isSingleValueType())
        return false;
  
      // We have an aggregate being stored, split it apart.
      LLVM_DEBUG(dbgs() << "    original: " << SI << "\n");
      AAMDNodes AATags;
      SI.getAAMetadata(AATags);
      StoreOpSplitter Splitter(&SI, *U, AATags);
      Splitter.emitSplitOps(V->getType(), V, V->getName() + ".fca");
      SI.eraseFromParent();
      return true;
    }
  
    bool visitBitCastInst(BitCastInst &BC) {
      enqueueUsers(BC);
      return false;
    }
  
    bool visitGetElementPtrInst(GetElementPtrInst &GEPI) {
      enqueueUsers(GEPI);
      return false;
    }
  
    bool visitPHINode(PHINode &PN) {
      enqueueUsers(PN);
      return false;
    }
  
    bool visitSelectInst(SelectInst &SI) {
      enqueueUsers(SI);
      return false;
    }
  };
  
  } // end anonymous namespace
  
  /// Strip aggregate type wrapping.
  ///
  /// This removes no-op aggregate types wrapping an underlying type. It will
  /// strip as many layers of types as it can without changing either the type
  /// size or the allocated size.
  static Type *stripAggregateTypeWrapping(const DataLayout &DL, Type *Ty) {
    if (Ty->isSingleValueType())
      return Ty;
  
    uint64_t AllocSize = DL.getTypeAllocSize(Ty);
    uint64_t TypeSize = DL.getTypeSizeInBits(Ty);
  
    Type *InnerTy;
    if (ArrayType *ArrTy = dyn_cast<ArrayType>(Ty)) {
      InnerTy = ArrTy->getElementType();
    } else if (StructType *STy = dyn_cast<StructType>(Ty)) {
      const StructLayout *SL = DL.getStructLayout(STy);
      unsigned Index = SL->getElementContainingOffset(0);
      InnerTy = STy->getElementType(Index);
    } else {
      return Ty;
    }
  
    if (AllocSize > DL.getTypeAllocSize(InnerTy) ||
        TypeSize > DL.getTypeSizeInBits(InnerTy))
      return Ty;
  
    return stripAggregateTypeWrapping(DL, InnerTy);
  }
  
  /// Try to find a partition of the aggregate type passed in for a given
  /// offset and size.
  ///
  /// This recurses through the aggregate type and tries to compute a subtype
  /// based on the offset and size. When the offset and size span a sub-section
  /// of an array, it will even compute a new array type for that sub-section,
  /// and the same for structs.
  ///
  /// Note that this routine is very strict and tries to find a partition of the
  /// type which produces the *exact* right offset and size. It is not forgiving
  /// when the size or offset cause either end of type-based partition to be off.
  /// Also, this is a best-effort routine. It is reasonable to give up and not
  /// return a type if necessary.
  static Type *getTypePartition(const DataLayout &DL, Type *Ty, uint64_t Offset,
                                uint64_t Size) {
    if (Offset == 0 && DL.getTypeAllocSize(Ty) == Size)
      return stripAggregateTypeWrapping(DL, Ty);
    if (Offset > DL.getTypeAllocSize(Ty) ||
        (DL.getTypeAllocSize(Ty) - Offset) < Size)
      return nullptr;
  
    if (SequentialType *SeqTy = dyn_cast<SequentialType>(Ty)) {
      Type *ElementTy = SeqTy->getElementType();
      uint64_t ElementSize = DL.getTypeAllocSize(ElementTy);
      uint64_t NumSkippedElements = Offset / ElementSize;
      if (NumSkippedElements >= SeqTy->getNumElements())
        return nullptr;
      Offset -= NumSkippedElements * ElementSize;
  
      // First check if we need to recurse.
      if (Offset > 0 || Size < ElementSize) {
        // Bail if the partition ends in a different array element.
        if ((Offset + Size) > ElementSize)
          return nullptr;
        // Recurse through the element type trying to peel off offset bytes.
        return getTypePartition(DL, ElementTy, Offset, Size);
      }
      assert(Offset == 0);
  
      if (Size == ElementSize)
        return stripAggregateTypeWrapping(DL, ElementTy);
      assert(Size > ElementSize);
      uint64_t NumElements = Size / ElementSize;
      if (NumElements * ElementSize != Size)
        return nullptr;
      return ArrayType::get(ElementTy, NumElements);
    }
  
    StructType *STy = dyn_cast<StructType>(Ty);
    if (!STy)
      return nullptr;
  
    const StructLayout *SL = DL.getStructLayout(STy);
    if (Offset >= SL->getSizeInBytes())
      return nullptr;
    uint64_t EndOffset = Offset + Size;
    if (EndOffset > SL->getSizeInBytes())
      return nullptr;
  
    unsigned Index = SL->getElementContainingOffset(Offset);
    Offset -= SL->getElementOffset(Index);
  
    Type *ElementTy = STy->getElementType(Index);
    uint64_t ElementSize = DL.getTypeAllocSize(ElementTy);
    if (Offset >= ElementSize)
      return nullptr; // The offset points into alignment padding.
  
    // See if any partition must be contained by the element.
    if (Offset > 0 || Size < ElementSize) {
      if ((Offset + Size) > ElementSize)
        return nullptr;
      return getTypePartition(DL, ElementTy, Offset, Size);
    }
    assert(Offset == 0);
  
    if (Size == ElementSize)
      return stripAggregateTypeWrapping(DL, ElementTy);
  
    StructType::element_iterator EI = STy->element_begin() + Index,
                                 EE = STy->element_end();
    if (EndOffset < SL->getSizeInBytes()) {
      unsigned EndIndex = SL->getElementContainingOffset(EndOffset);
      if (Index == EndIndex)
        return nullptr; // Within a single element and its padding.
  
      // Don't try to form "natural" types if the elements don't line up with the
      // expected size.
      // FIXME: We could potentially recurse down through the last element in the
      // sub-struct to find a natural end point.
      if (SL->getElementOffset(EndIndex) != EndOffset)
        return nullptr;
  
      assert(Index < EndIndex);
      EE = STy->element_begin() + EndIndex;
    }
  
    // Try to build up a sub-structure.
    StructType *SubTy =
        StructType::get(STy->getContext(), makeArrayRef(EI, EE), STy->isPacked());
    const StructLayout *SubSL = DL.getStructLayout(SubTy);
    if (Size != SubSL->getSizeInBytes())
      return nullptr; // The sub-struct doesn't have quite the size needed.
  
    return SubTy;
  }
  
  /// Pre-split loads and stores to simplify rewriting.
  ///
  /// We want to break up the splittable load+store pairs as much as
  /// possible. This is important to do as a preprocessing step, as once we
  /// start rewriting the accesses to partitions of the alloca we lose the
  /// necessary information to correctly split apart paired loads and stores
  /// which both point into this alloca. The case to consider is something like
  /// the following:
  ///
  ///   %a = alloca [12 x i8]
  ///   %gep1 = getelementptr [12 x i8]* %a, i32 0, i32 0
  ///   %gep2 = getelementptr [12 x i8]* %a, i32 0, i32 4
  ///   %gep3 = getelementptr [12 x i8]* %a, i32 0, i32 8
  ///   %iptr1 = bitcast i8* %gep1 to i64*
  ///   %iptr2 = bitcast i8* %gep2 to i64*
  ///   %fptr1 = bitcast i8* %gep1 to float*
  ///   %fptr2 = bitcast i8* %gep2 to float*
  ///   %fptr3 = bitcast i8* %gep3 to float*
  ///   store float 0.0, float* %fptr1
  ///   store float 1.0, float* %fptr2
  ///   %v = load i64* %iptr1
  ///   store i64 %v, i64* %iptr2
  ///   %f1 = load float* %fptr2
  ///   %f2 = load float* %fptr3
  ///
  /// Here we want to form 3 partitions of the alloca, each 4 bytes large, and
  /// promote everything so we recover the 2 SSA values that should have been
  /// there all along.
  ///
  /// \returns true if any changes are made.
  bool SROA::presplitLoadsAndStores(AllocaInst &AI, AllocaSlices &AS) {
    LLVM_DEBUG(dbgs() << "Pre-splitting loads and stores\n");
  
    // Track the loads and stores which are candidates for pre-splitting here, in
    // the order they first appear during the partition scan. These give stable
    // iteration order and a basis for tracking which loads and stores we
    // actually split.
    SmallVector<LoadInst *, 4> Loads;
    SmallVector<StoreInst *, 4> Stores;
  
    // We need to accumulate the splits required of each load or store where we
    // can find them via a direct lookup. This is important to cross-check loads
    // and stores against each other. We also track the slice so that we can kill
    // all the slices that end up split.
    struct SplitOffsets {
      Slice *S;
      std::vector<uint64_t> Splits;
    };
    SmallDenseMap<Instruction *, SplitOffsets, 8> SplitOffsetsMap;
  
    // Track loads out of this alloca which cannot, for any reason, be pre-split.
    // This is important as we also cannot pre-split stores of those loads!
    // FIXME: This is all pretty gross. It means that we can be more aggressive
    // in pre-splitting when the load feeding the store happens to come from
    // a separate alloca. Put another way, the effectiveness of SROA would be
    // decreased by a frontend which just concatenated all of its local allocas
    // into one big flat alloca. But defeating such patterns is exactly the job
    // SROA is tasked with! Sadly, to not have this discrepancy we would have
    // change store pre-splitting to actually force pre-splitting of the load
    // that feeds it *and all stores*. That makes pre-splitting much harder, but
    // maybe it would make it more principled?
    SmallPtrSet<LoadInst *, 8> UnsplittableLoads;
  
    LLVM_DEBUG(dbgs() << "  Searching for candidate loads and stores\n");
    for (auto &P : AS.partitions()) {
      for (Slice &S : P) {
        Instruction *I = cast<Instruction>(S.getUse()->getUser());
        if (!S.isSplittable() || S.endOffset() <= P.endOffset()) {
          // If this is a load we have to track that it can't participate in any
          // pre-splitting. If this is a store of a load we have to track that
          // that load also can't participate in any pre-splitting.
          if (auto *LI = dyn_cast<LoadInst>(I))
            UnsplittableLoads.insert(LI);
          else if (auto *SI = dyn_cast<StoreInst>(I))
            if (auto *LI = dyn_cast<LoadInst>(SI->getValueOperand()))
              UnsplittableLoads.insert(LI);
          continue;
        }
        assert(P.endOffset() > S.beginOffset() &&
               "Empty or backwards partition!");
  
        // Determine if this is a pre-splittable slice.
        if (auto *LI = dyn_cast<LoadInst>(I)) {
          assert(!LI->isVolatile() && "Cannot split volatile loads!");
  
          // The load must be used exclusively to store into other pointers for
          // us to be able to arbitrarily pre-split it. The stores must also be
          // simple to avoid changing semantics.
          auto IsLoadSimplyStored = [](LoadInst *LI) {
            for (User *LU : LI->users()) {
              auto *SI = dyn_cast<StoreInst>(LU);
              if (!SI || !SI->isSimple())
                return false;
            }
            return true;
          };
          if (!IsLoadSimplyStored(LI)) {
            UnsplittableLoads.insert(LI);
            continue;
          }
  
          Loads.push_back(LI);
        } else if (auto *SI = dyn_cast<StoreInst>(I)) {
          if (S.getUse() != &SI->getOperandUse(SI->getPointerOperandIndex()))
            // Skip stores *of* pointers. FIXME: This shouldn't even be possible!
            continue;
          auto *StoredLoad = dyn_cast<LoadInst>(SI->getValueOperand());
          if (!StoredLoad || !StoredLoad->isSimple())
            continue;
          assert(!SI->isVolatile() && "Cannot split volatile stores!");
  
          Stores.push_back(SI);
        } else {
          // Other uses cannot be pre-split.
          continue;
        }
  
        // Record the initial split.
        LLVM_DEBUG(dbgs() << "    Candidate: " << *I << "\n");
        auto &Offsets = SplitOffsetsMap[I];
        assert(Offsets.Splits.empty() &&
               "Should not have splits the first time we see an instruction!");
        Offsets.S = &S;
        Offsets.Splits.push_back(P.endOffset() - S.beginOffset());
      }
  
      // Now scan the already split slices, and add a split for any of them which
      // we're going to pre-split.
      for (Slice *S : P.splitSliceTails()) {
        auto SplitOffsetsMapI =
            SplitOffsetsMap.find(cast<Instruction>(S->getUse()->getUser()));
        if (SplitOffsetsMapI == SplitOffsetsMap.end())
          continue;
        auto &Offsets = SplitOffsetsMapI->second;
  
        assert(Offsets.S == S && "Found a mismatched slice!");
        assert(!Offsets.Splits.empty() &&
               "Cannot have an empty set of splits on the second partition!");
        assert(Offsets.Splits.back() ==
                   P.beginOffset() - Offsets.S->beginOffset() &&
               "Previous split does not end where this one begins!");
  
        // Record each split. The last partition's end isn't needed as the size
        // of the slice dictates that.
        if (S->endOffset() > P.endOffset())
          Offsets.Splits.push_back(P.endOffset() - Offsets.S->beginOffset());
      }
    }
  
    // We may have split loads where some of their stores are split stores. For
    // such loads and stores, we can only pre-split them if their splits exactly
    // match relative to their starting offset. We have to verify this prior to
    // any rewriting.
    Stores.erase(
        llvm::remove_if(Stores,
                        [&UnsplittableLoads, &SplitOffsetsMap](StoreInst *SI) {
                          // Lookup the load we are storing in our map of split
                          // offsets.
                          auto *LI = cast<LoadInst>(SI->getValueOperand());
                          // If it was completely unsplittable, then we're done,
                          // and this store can't be pre-split.
                          if (UnsplittableLoads.count(LI))
                            return true;
  
                          auto LoadOffsetsI = SplitOffsetsMap.find(LI);
                          if (LoadOffsetsI == SplitOffsetsMap.end())
                            return false; // Unrelated loads are definitely safe.
                          auto &LoadOffsets = LoadOffsetsI->second;
  
                          // Now lookup the store's offsets.
                          auto &StoreOffsets = SplitOffsetsMap[SI];
  
                          // If the relative offsets of each split in the load and
                          // store match exactly, then we can split them and we
                          // don't need to remove them here.
                          if (LoadOffsets.Splits == StoreOffsets.Splits)
                            return false;
  
                          LLVM_DEBUG(
                              dbgs()
                              << "    Mismatched splits for load and store:\n"
                              << "      " << *LI << "\n"
                              << "      " << *SI << "\n");
  
                          // We've found a store and load that we need to split
                          // with mismatched relative splits. Just give up on them
                          // and remove both instructions from our list of
                          // candidates.
                          UnsplittableLoads.insert(LI);
                          return true;
                        }),
        Stores.end());
    // Now we have to go *back* through all the stores, because a later store may
    // have caused an earlier store's load to become unsplittable and if it is
    // unsplittable for the later store, then we can't rely on it being split in
    // the earlier store either.
    Stores.erase(llvm::remove_if(Stores,
                                 [&UnsplittableLoads](StoreInst *SI) {
                                   auto *LI =
                                       cast<LoadInst>(SI->getValueOperand());
                                   return UnsplittableLoads.count(LI);
                                 }),
                 Stores.end());
    // Once we've established all the loads that can't be split for some reason,
    // filter any that made it into our list out.
    Loads.erase(llvm::remove_if(Loads,
                                [&UnsplittableLoads](LoadInst *LI) {
                                  return UnsplittableLoads.count(LI);
                                }),
                Loads.end());
  
    // If no loads or stores are left, there is no pre-splitting to be done for
    // this alloca.
    if (Loads.empty() && Stores.empty())
      return false;
  
    // From here on, we can't fail and will be building new accesses, so rig up
    // an IR builder.
    IRBuilderTy IRB(&AI);
  
    // Collect the new slices which we will merge into the alloca slices.
    SmallVector<Slice, 4> NewSlices;
  
    // Track any allocas we end up splitting loads and stores for so we iterate
    // on them.
    SmallPtrSet<AllocaInst *, 4> ResplitPromotableAllocas;
  
    // At this point, we have collected all of the loads and stores we can
    // pre-split, and the specific splits needed for them. We actually do the
    // splitting in a specific order in order to handle when one of the loads in
    // the value operand to one of the stores.
    //
    // First, we rewrite all of the split loads, and just accumulate each split
    // load in a parallel structure. We also build the slices for them and append
    // them to the alloca slices.
    SmallDenseMap<LoadInst *, std::vector<LoadInst *>, 1> SplitLoadsMap;
    std::vector<LoadInst *> SplitLoads;
    const DataLayout &DL = AI.getModule()->getDataLayout();
    for (LoadInst *LI : Loads) {
      SplitLoads.clear();
  
      IntegerType *Ty = cast<IntegerType>(LI->getType());
      // TVM local begin
      uint64_t LoadSize = Ty->getBitWidth() / ByteSizeInBits;
      // TVM local end
      assert(LoadSize > 0 && "Cannot have a zero-sized integer load!");
  
      auto &Offsets = SplitOffsetsMap[LI];
      assert(LoadSize == Offsets.S->endOffset() - Offsets.S->beginOffset() &&
             "Slice size should always match load size exactly!");
      uint64_t BaseOffset = Offsets.S->beginOffset();
      assert(BaseOffset + LoadSize > BaseOffset &&
             "Cannot represent alloca access size using 64-bit integers!");
  
      Instruction *BasePtr = cast<Instruction>(LI->getPointerOperand());
      IRB.SetInsertPoint(LI);
  
      LLVM_DEBUG(dbgs() << "  Splitting load: " << *LI << "\n");
  
      uint64_t PartOffset = 0, PartSize = Offsets.Splits.front();
      int Idx = 0, Size = Offsets.Splits.size();
      for (;;) {
        // TVM local begin
        auto *PartTy = Type::getIntNTy(Ty->getContext(),
                                       PartSize * ByteSizeInBits);
        // TVM local end
        auto AS = LI->getPointerAddressSpace();
        auto *PartPtrTy = PartTy->getPointerTo(AS);
        LoadInst *PLoad = IRB.CreateAlignedLoad(
            getAdjustedPtr(IRB, DL, BasePtr,
                           APInt(DL.getIndexSizeInBits(AS), PartOffset),
                           PartPtrTy, BasePtr->getName() + "."),
            getAdjustedAlignment(LI, PartOffset, DL), /*IsVolatile*/ false,
            LI->getName());
        PLoad->copyMetadata(*LI, LLVMContext::MD_mem_parallel_loop_access);
  
        // Append this load onto the list of split loads so we can find it later
        // to rewrite the stores.
        SplitLoads.push_back(PLoad);
  
        // Now build a new slice for the alloca.
        NewSlices.push_back(
            Slice(BaseOffset + PartOffset, BaseOffset + PartOffset + PartSize,
                  &PLoad->getOperandUse(PLoad->getPointerOperandIndex()),
                  /*IsSplittable*/ false));
        LLVM_DEBUG(dbgs() << "    new slice [" << NewSlices.back().beginOffset()
                          << ", " << NewSlices.back().endOffset()
                          << "): " << *PLoad << "\n");
  
        // See if we've handled all the splits.
        if (Idx >= Size)
          break;
  
        // Setup the next partition.
        PartOffset = Offsets.Splits[Idx];
        ++Idx;
        PartSize = (Idx < Size ? Offsets.Splits[Idx] : LoadSize) - PartOffset;
      }
  
      // Now that we have the split loads, do the slow walk over all uses of the
      // load and rewrite them as split stores, or save the split loads to use
      // below if the store is going to be split there anyways.
      bool DeferredStores = false;
      for (User *LU : LI->users()) {
        StoreInst *SI = cast<StoreInst>(LU);
        if (!Stores.empty() && SplitOffsetsMap.count(SI)) {
          DeferredStores = true;
          LLVM_DEBUG(dbgs() << "    Deferred splitting of store: " << *SI
                            << "\n");
          continue;
        }
  
        Value *StoreBasePtr = SI->getPointerOperand();
        IRB.SetInsertPoint(SI);
  
        LLVM_DEBUG(dbgs() << "    Splitting store of load: " << *SI << "\n");
  
        for (int Idx = 0, Size = SplitLoads.size(); Idx < Size; ++Idx) {
          LoadInst *PLoad = SplitLoads[Idx];
          uint64_t PartOffset = Idx == 0 ? 0 : Offsets.Splits[Idx - 1];
          auto *PartPtrTy =
              PLoad->getType()->getPointerTo(SI->getPointerAddressSpace());
  
          auto AS = SI->getPointerAddressSpace();
          StoreInst *PStore = IRB.CreateAlignedStore(
              PLoad,
              getAdjustedPtr(IRB, DL, StoreBasePtr,
                             APInt(DL.getIndexSizeInBits(AS), PartOffset),
                             PartPtrTy, StoreBasePtr->getName() + "."),
              getAdjustedAlignment(SI, PartOffset, DL), /*IsVolatile*/ false);
          PStore->copyMetadata(*LI, LLVMContext::MD_mem_parallel_loop_access);
          LLVM_DEBUG(dbgs() << "      +" << PartOffset << ":" << *PStore << "\n");
        }
  
        // We want to immediately iterate on any allocas impacted by splitting
        // this store, and we have to track any promotable alloca (indicated by
        // a direct store) as needing to be resplit because it is no longer
        // promotable.
        if (AllocaInst *OtherAI = dyn_cast<AllocaInst>(StoreBasePtr)) {
          ResplitPromotableAllocas.insert(OtherAI);
          Worklist.insert(OtherAI);
        } else if (AllocaInst *OtherAI = dyn_cast<AllocaInst>(
                       StoreBasePtr->stripInBoundsOffsets())) {
          Worklist.insert(OtherAI);
        }
  
        // Mark the original store as dead.
        DeadInsts.insert(SI);
      }
  
      // Save the split loads if there are deferred stores among the users.
      if (DeferredStores)
        SplitLoadsMap.insert(std::make_pair(LI, std::move(SplitLoads)));
  
      // Mark the original load as dead and kill the original slice.
      DeadInsts.insert(LI);
      Offsets.S->kill();
    }
  
    // Second, we rewrite all of the split stores. At this point, we know that
    // all loads from this alloca have been split already. For stores of such
    // loads, we can simply look up the pre-existing split loads. For stores of
    // other loads, we split those loads first and then write split stores of
    // them.
    for (StoreInst *SI : Stores) {
      auto *LI = cast<LoadInst>(SI->getValueOperand());
      IntegerType *Ty = cast<IntegerType>(LI->getType());
      // TVM local begin
      uint64_t StoreSize = Ty->getBitWidth() / ByteSizeInBits;
      // TVM local end
      assert(StoreSize > 0 && "Cannot have a zero-sized integer store!");
  
      auto &Offsets = SplitOffsetsMap[SI];
      assert(StoreSize == Offsets.S->endOffset() - Offsets.S->beginOffset() &&
             "Slice size should always match load size exactly!");
      uint64_t BaseOffset = Offsets.S->beginOffset();
      assert(BaseOffset + StoreSize > BaseOffset &&
             "Cannot represent alloca access size using 64-bit integers!");
  
      Value *LoadBasePtr = LI->getPointerOperand();
      Instruction *StoreBasePtr = cast<Instruction>(SI->getPointerOperand());
  
      LLVM_DEBUG(dbgs() << "  Splitting store: " << *SI << "\n");
  
      // Check whether we have an already split load.
      auto SplitLoadsMapI = SplitLoadsMap.find(LI);
      std::vector<LoadInst *> *SplitLoads = nullptr;
      if (SplitLoadsMapI != SplitLoadsMap.end()) {
        SplitLoads = &SplitLoadsMapI->second;
        assert(SplitLoads->size() == Offsets.Splits.size() + 1 &&
               "Too few split loads for the number of splits in the store!");
      } else {
        LLVM_DEBUG(dbgs() << "          of load: " << *LI << "\n");
      }
  
      uint64_t PartOffset = 0, PartSize = Offsets.Splits.front();
      int Idx = 0, Size = Offsets.Splits.size();
      for (;;) {
        // TVM local begin
        auto *PartTy = Type::getIntNTy(Ty->getContext(),
                                       PartSize * ByteSizeInBits);
        // TVM local end
        auto *LoadPartPtrTy = PartTy->getPointerTo(LI->getPointerAddressSpace());
        auto *StorePartPtrTy = PartTy->getPointerTo(SI->getPointerAddressSpace());
  
        // Either lookup a split load or create one.
        LoadInst *PLoad;
        if (SplitLoads) {
          PLoad = (*SplitLoads)[Idx];
        } else {
          IRB.SetInsertPoint(LI);
          auto AS = LI->getPointerAddressSpace();
          PLoad = IRB.CreateAlignedLoad(
              getAdjustedPtr(IRB, DL, LoadBasePtr,
                             APInt(DL.getIndexSizeInBits(AS), PartOffset),
                             LoadPartPtrTy, LoadBasePtr->getName() + "."),
              getAdjustedAlignment(LI, PartOffset, DL), /*IsVolatile*/ false,
              LI->getName());
        }
  
        // And store this partition.
        IRB.SetInsertPoint(SI);
        auto AS = SI->getPointerAddressSpace();
        StoreInst *PStore = IRB.CreateAlignedStore(
            PLoad,
            getAdjustedPtr(IRB, DL, StoreBasePtr,
                           APInt(DL.getIndexSizeInBits(AS), PartOffset),
                           StorePartPtrTy, StoreBasePtr->getName() + "."),
            getAdjustedAlignment(SI, PartOffset, DL), /*IsVolatile*/ false);
  
        // Now build a new slice for the alloca.
        NewSlices.push_back(
            Slice(BaseOffset + PartOffset, BaseOffset + PartOffset + PartSize,
                  &PStore->getOperandUse(PStore->getPointerOperandIndex()),
                  /*IsSplittable*/ false));
        LLVM_DEBUG(dbgs() << "    new slice [" << NewSlices.back().beginOffset()
                          << ", " << NewSlices.back().endOffset()
                          << "): " << *PStore << "\n");
        if (!SplitLoads) {
          LLVM_DEBUG(dbgs() << "      of split load: " << *PLoad << "\n");
        }
  
        // See if we've finished all the splits.
        if (Idx >= Size)
          break;
  
        // Setup the next partition.
        PartOffset = Offsets.Splits[Idx];
        ++Idx;
        PartSize = (Idx < Size ? Offsets.Splits[Idx] : StoreSize) - PartOffset;
      }
  
      // We want to immediately iterate on any allocas impacted by splitting
      // this load, which is only relevant if it isn't a load of this alloca and
      // thus we didn't already split the loads above. We also have to keep track
      // of any promotable allocas we split loads on as they can no longer be
      // promoted.
      if (!SplitLoads) {
        if (AllocaInst *OtherAI = dyn_cast<AllocaInst>(LoadBasePtr)) {
          assert(OtherAI != &AI && "We can't re-split our own alloca!");
          ResplitPromotableAllocas.insert(OtherAI);
          Worklist.insert(OtherAI);
        } else if (AllocaInst *OtherAI = dyn_cast<AllocaInst>(
                       LoadBasePtr->stripInBoundsOffsets())) {
          assert(OtherAI != &AI && "We can't re-split our own alloca!");
          Worklist.insert(OtherAI);
        }
      }
  
      // Mark the original store as dead now that we've split it up and kill its
      // slice. Note that we leave the original load in place unless this store
      // was its only use. It may in turn be split up if it is an alloca load
      // for some other alloca, but it may be a normal load. This may introduce
      // redundant loads, but where those can be merged the rest of the optimizer
      // should handle the merging, and this uncovers SSA splits which is more
      // important. In practice, the original loads will almost always be fully
      // split and removed eventually, and the splits will be merged by any
      // trivial CSE, including instcombine.
      if (LI->hasOneUse()) {
        assert(*LI->user_begin() == SI && "Single use isn't this store!");
        DeadInsts.insert(LI);
      }
      DeadInsts.insert(SI);
      Offsets.S->kill();
    }
  
    // Remove the killed slices that have ben pre-split.
    AS.erase(llvm::remove_if(AS, [](const Slice &S) { return S.isDead(); }),
             AS.end());
  
    // Insert our new slices. This will sort and merge them into the sorted
    // sequence.
    AS.insert(NewSlices);
  
    LLVM_DEBUG(dbgs() << "  Pre-split slices:\n");
  #ifndef NDEBUG
    for (auto I = AS.begin(), E = AS.end(); I != E; ++I)
      LLVM_DEBUG(AS.print(dbgs(), I, "    "));
  #endif
  
    // Finally, don't try to promote any allocas that new require re-splitting.
    // They have already been added to the worklist above.
    PromotableAllocas.erase(
        llvm::remove_if(
            PromotableAllocas,
            [&](AllocaInst *AI) { return ResplitPromotableAllocas.count(AI); }),
        PromotableAllocas.end());
  
    return true;
  }
  
  /// Rewrite an alloca partition's users.
  ///
  /// This routine drives both of the rewriting goals of the SROA pass. It tries
  /// to rewrite uses of an alloca partition to be conducive for SSA value
  /// promotion. If the partition needs a new, more refined alloca, this will
  /// build that new alloca, preserving as much type information as possible, and
  /// rewrite the uses of the old alloca to point at the new one and have the
  /// appropriate new offsets. It also evaluates how successful the rewrite was
  /// at enabling promotion and if it was successful queues the alloca to be
  /// promoted.
  AllocaInst *SROA::rewritePartition(AllocaInst &AI, AllocaSlices &AS,
                                     Partition &P) {
    // Try to compute a friendly type for this partition of the alloca. This
    // won't always succeed, in which case we fall back to a legal integer type
    // or an i8 array of an appropriate size.
    Type *SliceTy = nullptr;
    const DataLayout &DL = AI.getModule()->getDataLayout();
    if (Type *CommonUseTy = findCommonType(P.begin(), P.end(), P.endOffset()))
      if (DL.getTypeAllocSize(CommonUseTy) >= P.size())
        SliceTy = CommonUseTy;
    if (!SliceTy)
      if (Type *TypePartitionTy = getTypePartition(DL, AI.getAllocatedType(),
                                                   P.beginOffset(), P.size()))
        SliceTy = TypePartitionTy;
    // TVM local begin
    if ((!SliceTy || (SliceTy->isArrayTy() &&
                      SliceTy->getArrayElementType()->isIntegerTy())) &&
        DL.isLegalInteger(P.size() * ByteSizeInBits))
      SliceTy = Type::getIntNTy(*C, P.size() * ByteSizeInBits);
    if (!SliceTy)
      SliceTy = ArrayType::get(Type::getIntNTy(*C, ByteSizeInBits), P.size());
    // TVM local end
    assert(DL.getTypeAllocSize(SliceTy) >= P.size());
  
    bool IsIntegerPromotable = isIntegerWideningViable(P, SliceTy, DL);
  
    VectorType *VecTy =
        IsIntegerPromotable ? nullptr : isVectorPromotionViable(P, DL);
    if (VecTy)
      SliceTy = VecTy;
  
    // Check for the case where we're going to rewrite to a new alloca of the
    // exact same type as the original, and with the same access offsets. In that
    // case, re-use the existing alloca, but still run through the rewriter to
    // perform phi and select speculation.
    // P.beginOffset() can be non-zero even with the same type in a case with
    // out-of-bounds access (e.g. @PR35657 function in SROA/basictest.ll).
    AllocaInst *NewAI;
    if (SliceTy == AI.getAllocatedType() && P.beginOffset() == 0) {
      NewAI = &AI;
      // FIXME: We should be able to bail at this point with "nothing changed".
      // FIXME: We might want to defer PHI speculation until after here.
      // FIXME: return nullptr;
    } else {
      unsigned Alignment = AI.getAlignment();
      if (!Alignment) {
        // The minimum alignment which users can rely on when the explicit
        // alignment is omitted or zero is that required by the ABI for this
        // type.
        Alignment = DL.getABITypeAlignment(AI.getAllocatedType());
      }
      Alignment = MinAlign(Alignment, P.beginOffset());
      // If we will get at least this much alignment from the type alone, leave
      // the alloca's alignment unconstrained.
      if (Alignment <= DL.getABITypeAlignment(SliceTy))
        Alignment = 0;
      NewAI = new AllocaInst(
        SliceTy, AI.getType()->getAddressSpace(), nullptr, Alignment,
          AI.getName() + ".sroa." + Twine(P.begin() - AS.begin()), &AI);
      // Copy the old AI debug location over to the new one.
      NewAI->setDebugLoc(AI.getDebugLoc());
      ++NumNewAllocas;
    }
  
    LLVM_DEBUG(dbgs() << "Rewriting alloca partition "
                      << "[" << P.beginOffset() << "," << P.endOffset()
                      << ") to: " << *NewAI << "\n");
  
    // Track the high watermark on the worklist as it is only relevant for
    // promoted allocas. We will reset it to this point if the alloca is not in
    // fact scheduled for promotion.
    unsigned PPWOldSize = PostPromotionWorklist.size();
    unsigned NumUses = 0;
    SmallSetVector<PHINode *, 8> PHIUsers;
    SmallSetVector<SelectInst *, 8> SelectUsers;
  
    AllocaSliceRewriter Rewriter(DL, AS, *this, AI, *NewAI, P.beginOffset(),
                                 P.endOffset(), IsIntegerPromotable, VecTy,
                                 PHIUsers, SelectUsers);
    bool Promotable = true;
    for (Slice *S : P.splitSliceTails()) {
      Promotable &= Rewriter.visit(S);
      ++NumUses;
    }
    for (Slice &S : P) {
      Promotable &= Rewriter.visit(&S);
      ++NumUses;
    }
  
    NumAllocaPartitionUses += NumUses;
    MaxUsesPerAllocaPartition.updateMax(NumUses);
  
    // Now that we've processed all the slices in the new partition, check if any
    // PHIs or Selects would block promotion.
    for (PHINode *PHI : PHIUsers)
      if (!isSafePHIToSpeculate(*PHI)) {
        Promotable = false;
        PHIUsers.clear();
        SelectUsers.clear();
        break;
      }
  
    for (SelectInst *Sel : SelectUsers)
      if (!isSafeSelectToSpeculate(*Sel)) {
        Promotable = false;
        PHIUsers.clear();
        SelectUsers.clear();
        break;
      }
  
    if (Promotable) {
      if (PHIUsers.empty() && SelectUsers.empty()) {
        // Promote the alloca.
        PromotableAllocas.push_back(NewAI);
      } else {
        // If we have either PHIs or Selects to speculate, add them to those
        // worklists and re-queue the new alloca so that we promote in on the
        // next iteration.
        for (PHINode *PHIUser : PHIUsers)
          SpeculatablePHIs.insert(PHIUser);
        for (SelectInst *SelectUser : SelectUsers)
          SpeculatableSelects.insert(SelectUser);
        Worklist.insert(NewAI);
      }
    } else {
      // Drop any post-promotion work items if promotion didn't happen.
      while (PostPromotionWorklist.size() > PPWOldSize)
        PostPromotionWorklist.pop_back();
  
      // We couldn't promote and we didn't create a new partition, nothing
      // happened.
      if (NewAI == &AI)
        return nullptr;
  
      // If we can't promote the alloca, iterate on it to check for new
      // refinements exposed by splitting the current alloca. Don't iterate on an
      // alloca which didn't actually change and didn't get promoted.
      Worklist.insert(NewAI);
    }
  
    return NewAI;
  }
  
  /// Walks the slices of an alloca and form partitions based on them,
  /// rewriting each of their uses.
  bool SROA::splitAlloca(AllocaInst &AI, AllocaSlices &AS) {
    if (AS.begin() == AS.end())
      return false;
  
    unsigned NumPartitions = 0;
    bool Changed = false;
    const DataLayout &DL = AI.getModule()->getDataLayout();
  
    // First try to pre-split loads and stores.
    Changed |= presplitLoadsAndStores(AI, AS);
  
    // Now that we have identified any pre-splitting opportunities,
    // mark loads and stores unsplittable except for the following case.
    // We leave a slice splittable if all other slices are disjoint or fully
    // included in the slice, such as whole-alloca loads and stores.
    // If we fail to split these during pre-splitting, we want to force them
    // to be rewritten into a partition.
    bool IsSorted = true;
  
    uint64_t AllocaSize = DL.getTypeAllocSize(AI.getAllocatedType());
    const uint64_t MaxBitVectorSize = 1024;
    if (AllocaSize <= MaxBitVectorSize) {
      // If a byte boundary is included in any load or store, a slice starting or
      // ending at the boundary is not splittable.
      SmallBitVector SplittableOffset(AllocaSize + 1, true);
      for (Slice &S : AS)
        for (unsigned O = S.beginOffset() + 1;
             O < S.endOffset() && O < AllocaSize; O++)
          SplittableOffset.reset(O);
  
      for (Slice &S : AS) {
        if (!S.isSplittable())
          continue;
  
        if ((S.beginOffset() > AllocaSize || SplittableOffset[S.beginOffset()]) &&
            (S.endOffset() > AllocaSize || SplittableOffset[S.endOffset()]))
          continue;
  
        if (isa<LoadInst>(S.getUse()->getUser()) ||
            isa<StoreInst>(S.getUse()->getUser())) {
          S.makeUnsplittable();
          IsSorted = false;
        }
      }
    }
    else {
      // We only allow whole-alloca splittable loads and stores
      // for a large alloca to avoid creating too large BitVector.
      for (Slice &S : AS) {
        if (!S.isSplittable())
          continue;
  
        if (S.beginOffset() == 0 && S.endOffset() >= AllocaSize)
          continue;
  
        if (isa<LoadInst>(S.getUse()->getUser()) ||
            isa<StoreInst>(S.getUse()->getUser())) {
          S.makeUnsplittable();
          IsSorted = false;
        }
      }
    }
  
    if (!IsSorted)
      llvm::sort(AS.begin(), AS.end());
  
    /// Describes the allocas introduced by rewritePartition in order to migrate
    /// the debug info.
    struct Fragment {
      AllocaInst *Alloca;
      uint64_t Offset;
      uint64_t Size;
      Fragment(AllocaInst *AI, uint64_t O, uint64_t S)
        : Alloca(AI), Offset(O), Size(S) {}
    };
    SmallVector<Fragment, 4> Fragments;
  
    // Rewrite each partition.
    for (auto &P : AS.partitions()) {
      if (AllocaInst *NewAI = rewritePartition(AI, AS, P)) {
        Changed = true;
        if (NewAI != &AI) {
          // TVM local begin
          uint64_t SizeOfByte = ByteSizeInBits;
          // TVM local end
          uint64_t AllocaSize = DL.getTypeSizeInBits(NewAI->getAllocatedType());
          // Don't include any padding.
          uint64_t Size = std::min(AllocaSize, P.size() * SizeOfByte);
          Fragments.push_back(Fragment(NewAI, P.beginOffset() * SizeOfByte, Size));
        }
      }
      ++NumPartitions;
    }
  
    NumAllocaPartitions += NumPartitions;
    MaxPartitionsPerAlloca.updateMax(NumPartitions);
  
    // Migrate debug information from the old alloca to the new alloca(s)
    // and the individual partitions.
    TinyPtrVector<DbgInfoIntrinsic *> DbgDeclares = FindDbgAddrUses(&AI);
    if (!DbgDeclares.empty()) {
      auto *Var = DbgDeclares.front()->getVariable();
      auto *Expr = DbgDeclares.front()->getExpression();
      auto VarSize = Var->getSizeInBits();
      DIBuilder DIB(*AI.getModule(), /*AllowUnresolved*/ false);
      uint64_t AllocaSize = DL.getTypeSizeInBits(AI.getAllocatedType());
      for (auto Fragment : Fragments) {
        // Create a fragment expression describing the new partition or reuse AI's
        // expression if there is only one partition.
        auto *FragmentExpr = Expr;
        if (Fragment.Size < AllocaSize || Expr->isFragment()) {
          // If this alloca is already a scalar replacement of a larger aggregate,
          // Fragment.Offset describes the offset inside the scalar.
          auto ExprFragment = Expr->getFragmentInfo();
          uint64_t Offset = ExprFragment ? ExprFragment->OffsetInBits : 0;
          uint64_t Start = Offset + Fragment.Offset;
          uint64_t Size = Fragment.Size;
          if (ExprFragment) {
            uint64_t AbsEnd =
                ExprFragment->OffsetInBits + ExprFragment->SizeInBits;
            if (Start >= AbsEnd)
              // No need to describe a SROAed padding.
              continue;
            Size = std::min(Size, AbsEnd - Start);
          }
          // The new, smaller fragment is stenciled out from the old fragment.
          if (auto OrigFragment = FragmentExpr->getFragmentInfo()) {
            assert(Start >= OrigFragment->OffsetInBits &&
                   "new fragment is outside of original fragment");
            Start -= OrigFragment->OffsetInBits;
          }
  
          // The alloca may be larger than the variable.
          if (VarSize) {
            if (Size > *VarSize)
              Size = *VarSize;
            if (Size == 0 || Start + Size > *VarSize)
              continue;
          }
  
          // Avoid creating a fragment expression that covers the entire variable.
          if (!VarSize || *VarSize != Size) {
            if (auto E =
                    DIExpression::createFragmentExpression(Expr, Start, Size))
              FragmentExpr = *E;
            else
              continue;
          }
        }
  
        // Remove any existing intrinsics describing the same alloca.
        for (DbgInfoIntrinsic *OldDII : FindDbgAddrUses(Fragment.Alloca))
          OldDII->eraseFromParent();
  
        DIB.insertDeclare(Fragment.Alloca, Var, FragmentExpr,
                          DbgDeclares.front()->getDebugLoc(), &AI);
      }
    }
    return Changed;
  }
  
  /// Clobber a use with undef, deleting the used value if it becomes dead.
  void SROA::clobberUse(Use &U) {
    Value *OldV = U;
    // Replace the use with an undef value.
    U = UndefValue::get(OldV->getType());
  
    // Check for this making an instruction dead. We have to garbage collect
    // all the dead instructions to ensure the uses of any alloca end up being
    // minimal.
    if (Instruction *OldI = dyn_cast<Instruction>(OldV))
      if (isInstructionTriviallyDead(OldI)) {
        DeadInsts.insert(OldI);
      }
  }
  
  /// Analyze an alloca for SROA.
  ///
  /// This analyzes the alloca to ensure we can reason about it, builds
  /// the slices of the alloca, and then hands it off to be split and
  /// rewritten as needed.
  bool SROA::runOnAlloca(AllocaInst &AI) {
    LLVM_DEBUG(dbgs() << "SROA alloca: " << AI << "\n");
    ++NumAllocasAnalyzed;
  
    // Special case dead allocas, as they're trivial.
    if (AI.use_empty()) {
      AI.eraseFromParent();
      return true;
    }
    const DataLayout &DL = AI.getModule()->getDataLayout();
  
    // Skip alloca forms that this analysis can't handle.
    if (AI.isArrayAllocation() || !AI.getAllocatedType()->isSized() ||
        DL.getTypeAllocSize(AI.getAllocatedType()) == 0)
      return false;
  
    bool Changed = false;
  
    // First, split any FCA loads and stores touching this alloca to promote
    // better splitting and promotion opportunities.
    AggLoadStoreRewriter AggRewriter;
    Changed |= AggRewriter.rewrite(AI);
  
    // Build the slices using a recursive instruction-visiting builder.
    AllocaSlices AS(DL, AI);
    LLVM_DEBUG(AS.print(dbgs()));
    if (AS.isEscaped())
      return Changed;
  
    // Delete all the dead users of this alloca before splitting and rewriting it.
    for (Instruction *DeadUser : AS.getDeadUsers()) {
      // Free up everything used by this instruction.
      for (Use &DeadOp : DeadUser->operands())
        clobberUse(DeadOp);
  
      // Now replace the uses of this instruction.
      DeadUser->replaceAllUsesWith(UndefValue::get(DeadUser->getType()));
  
      // And mark it for deletion.
      DeadInsts.insert(DeadUser);
      Changed = true;
    }
    for (Use *DeadOp : AS.getDeadOperands()) {
      clobberUse(*DeadOp);
      Changed = true;
    }
  
    // No slices to split. Leave the dead alloca for a later pass to clean up.
    if (AS.begin() == AS.end())
      return Changed;
  
    Changed |= splitAlloca(AI, AS);
  
    LLVM_DEBUG(dbgs() << "  Speculating PHIs\n");
    while (!SpeculatablePHIs.empty())
      speculatePHINodeLoads(*SpeculatablePHIs.pop_back_val());
  
    LLVM_DEBUG(dbgs() << "  Speculating Selects\n");
    while (!SpeculatableSelects.empty())
      speculateSelectInstLoads(*SpeculatableSelects.pop_back_val());
  
    return Changed;
  }
  
  /// Delete the dead instructions accumulated in this run.
  ///
  /// Recursively deletes the dead instructions we've accumulated. This is done
  /// at the very end to maximize locality of the recursive delete and to
  /// minimize the problems of invalidated instruction pointers as such pointers
  /// are used heavily in the intermediate stages of the algorithm.
  ///
  /// We also record the alloca instructions deleted here so that they aren't
  /// subsequently handed to mem2reg to promote.
  bool SROA::deleteDeadInstructions(
      SmallPtrSetImpl<AllocaInst *> &DeletedAllocas) {
    bool Changed = false;
    while (!DeadInsts.empty()) {
      Instruction *I = DeadInsts.pop_back_val();
      LLVM_DEBUG(dbgs() << "Deleting dead instruction: " << *I << "\n");
  
      // If the instruction is an alloca, find the possible dbg.declare connected
      // to it, and remove it too. We must do this before calling RAUW or we will
      // not be able to find it.
      if (AllocaInst *AI = dyn_cast<AllocaInst>(I)) {
        DeletedAllocas.insert(AI);
        for (DbgInfoIntrinsic *OldDII : FindDbgAddrUses(AI))
          OldDII->eraseFromParent();
      }
  
      I->replaceAllUsesWith(UndefValue::get(I->getType()));
  
      for (Use &Operand : I->operands())
        if (Instruction *U = dyn_cast<Instruction>(Operand)) {
          // Zero out the operand and see if it becomes trivially dead.
          Operand = nullptr;
          if (isInstructionTriviallyDead(U))
            DeadInsts.insert(U);
        }
  
      ++NumDeleted;
      I->eraseFromParent();
      Changed = true;
    }
    return Changed;
  }
  
  /// Promote the allocas, using the best available technique.
  ///
  /// This attempts to promote whatever allocas have been identified as viable in
  /// the PromotableAllocas list. If that list is empty, there is nothing to do.
  /// This function returns whether any promotion occurred.
  bool SROA::promoteAllocas(Function &F) {
    if (PromotableAllocas.empty())
      return false;
  
    NumPromoted += PromotableAllocas.size();
  
    LLVM_DEBUG(dbgs() << "Promoting allocas with mem2reg...\n");
    PromoteMemToReg(PromotableAllocas, *DT, AC);
    PromotableAllocas.clear();
    return true;
  }
  
  PreservedAnalyses SROA::runImpl(Function &F, DominatorTree &RunDT,
                                  AssumptionCache &RunAC) {
    LLVM_DEBUG(dbgs() << "SROA function: " << F.getName() << "\n");
    C = &F.getContext();
    DT = &RunDT;
    AC = &RunAC;
  
    BasicBlock &EntryBB = F.getEntryBlock();
    for (BasicBlock::iterator I = EntryBB.begin(), E = std::prev(EntryBB.end());
         I != E; ++I) {
      if (AllocaInst *AI = dyn_cast<AllocaInst>(I))
        Worklist.insert(AI);
    }
  
    bool Changed = false;
    // A set of deleted alloca instruction pointers which should be removed from
    // the list of promotable allocas.
    SmallPtrSet<AllocaInst *, 4> DeletedAllocas;
  
    do {
      while (!Worklist.empty()) {
        Changed |= runOnAlloca(*Worklist.pop_back_val());
        Changed |= deleteDeadInstructions(DeletedAllocas);
  
        // Remove the deleted allocas from various lists so that we don't try to
        // continue processing them.
        if (!DeletedAllocas.empty()) {
          auto IsInSet = [&](AllocaInst *AI) { return DeletedAllocas.count(AI); };
          Worklist.remove_if(IsInSet);
          PostPromotionWorklist.remove_if(IsInSet);
          PromotableAllocas.erase(llvm::remove_if(PromotableAllocas, IsInSet),
                                  PromotableAllocas.end());
          DeletedAllocas.clear();
        }
      }
  
      Changed |= promoteAllocas(F);
  
      Worklist = PostPromotionWorklist;
      PostPromotionWorklist.clear();
    } while (!Worklist.empty());
  
    if (!Changed)
      return PreservedAnalyses::all();
  
    PreservedAnalyses PA;
    PA.preserveSet<CFGAnalyses>();
    PA.preserve<GlobalsAA>();
    return PA;
  }
  
  PreservedAnalyses SROA::run(Function &F, FunctionAnalysisManager &AM) {
    return runImpl(F, AM.getResult<DominatorTreeAnalysis>(F),
                   AM.getResult<AssumptionAnalysis>(F));
  }
  
  /// A legacy pass for the legacy pass manager that wraps the \c SROA pass.
  ///
  /// This is in the llvm namespace purely to allow it to be a friend of the \c
  /// SROA pass.
  class llvm::sroa::SROALegacyPass : public FunctionPass {
    /// The SROA implementation.
    SROA Impl;
  
  public:
    static char ID;
  
    SROALegacyPass() : FunctionPass(ID) {
      initializeSROALegacyPassPass(*PassRegistry::getPassRegistry());
    }
  
    bool runOnFunction(Function &F) override {
      if (skipFunction(F))
        return false;
  
      auto PA = Impl.runImpl(
          F, getAnalysis<DominatorTreeWrapperPass>().getDomTree(),
          getAnalysis<AssumptionCacheTracker>().getAssumptionCache(F));
      return !PA.areAllPreserved();
    }
  
    void getAnalysisUsage(AnalysisUsage &AU) const override {
      AU.addRequired<AssumptionCacheTracker>();
      AU.addRequired<DominatorTreeWrapperPass>();
      AU.addPreserved<GlobalsAAWrapperPass>();
      AU.setPreservesCFG();
    }
  
    StringRef getPassName() const override { return "SROA"; }
  };
  
  char SROALegacyPass::ID = 0;
  
  FunctionPass *llvm::createSROAPass() { return new SROALegacyPass(); }
  
  INITIALIZE_PASS_BEGIN(SROALegacyPass, "sroa",
                        "Scalar Replacement Of Aggregates", false, false)
  INITIALIZE_PASS_DEPENDENCY(AssumptionCacheTracker)
  INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)
  INITIALIZE_PASS_END(SROALegacyPass, "sroa", "Scalar Replacement Of Aggregates",
                      false, false)
  