text: //===- llvm/ADT/SmallPtrSet.cpp - 'Normally small' pointer set ------------===//
  //
  // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
  // See https://llvm.org/LICENSE.txt for license information.
  // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
  //
  //===----------------------------------------------------------------------===//
  //
  // This file implements the SmallPtrSet class.  See SmallPtrSet.h for an
  // overview of the algorithm.
  //
  //===----------------------------------------------------------------------===//
  
  #include "llvm/ADT/SmallPtrSet.h"
  #include "llvm/ADT/DenseMapInfo.h"
  #include "llvm/Support/MathExtras.h"
  #include "llvm/Support/ErrorHandling.h"
  #include <algorithm>
  #include <cassert>
  #include <cstdlib>
  
  using namespace llvm;
  
  void SmallPtrSetImplBase::shrink_and_clear() {
    assert(!isSmall() && "Can't shrink a small set!");
    free(CurArray);
  
    // Reduce the number of buckets.
    unsigned Size = size();
    CurArraySize = Size > 16 ? 1 << (Log2_32_Ceil(Size) + 1) : 32;
    NumNonEmpty = NumTombstones = 0;
  
    // Install the new array.  Clear all the buckets to empty.
    CurArray = (const void**)safe_malloc(sizeof(void*) * CurArraySize);
  
    memset(CurArray, -1, CurArraySize*sizeof(void*));
  }
  
  std::pair<const void *const *, bool>
  SmallPtrSetImplBase::insert_imp_big(const void *Ptr) {
    if (LLVM_UNLIKELY(size() * 4 >= CurArraySize * 3)) {
      // If more than 3/4 of the array is full, grow.
      Grow(CurArraySize < 64 ? 128 : CurArraySize * 2);
    } else if (LLVM_UNLIKELY(CurArraySize - NumNonEmpty < CurArraySize / 8)) {
      // If fewer of 1/8 of the array is empty (meaning that many are filled with
      // tombstones), rehash.
      Grow(CurArraySize);
    }
  
    // Okay, we know we have space.  Find a hash bucket.
    const void **Bucket = const_cast<const void**>(FindBucketFor(Ptr));
    if (*Bucket == Ptr)
      return std::make_pair(Bucket, false); // Already inserted, good.
  
    // Otherwise, insert it!
    if (*Bucket == getTombstoneMarker())
      --NumTombstones;
    else
      ++NumNonEmpty; // Track density.
    *Bucket = Ptr;
    return std::make_pair(Bucket, true);
  }
  
  const void * const *SmallPtrSetImplBase::FindBucketFor(const void *Ptr) const {
    unsigned Bucket = DenseMapInfo<void *>::getHashValue(Ptr) & (CurArraySize-1);
    unsigned ArraySize = CurArraySize;
    unsigned ProbeAmt = 1;
    const void *const *Array = CurArray;
    const void *const *Tombstone = nullptr;
    while (true) {
      // If we found an empty bucket, the pointer doesn't exist in the set.
      // Return a tombstone if we've seen one so far, or the empty bucket if
      // not.
      if (LLVM_LIKELY(Array[Bucket] == getEmptyMarker()))
        return Tombstone ? Tombstone : Array+Bucket;
  
      // Found Ptr's bucket?
      if (LLVM_LIKELY(Array[Bucket] == Ptr))
        return Array+Bucket;
  
      // If this is a tombstone, remember it.  If Ptr ends up not in the set, we
      // prefer to return it than something that would require more probing.
      if (Array[Bucket] == getTombstoneMarker() && !Tombstone)
        Tombstone = Array+Bucket;  // Remember the first tombstone found.
  
      // It's a hash collision or a tombstone. Reprobe.
      Bucket = (Bucket + ProbeAmt++) & (ArraySize-1);
    }
  }
  
  /// Grow - Allocate a larger backing store for the buckets and move it over.
  ///
  void SmallPtrSetImplBase::Grow(unsigned NewSize) {
    const void **OldBuckets = CurArray;
    const void **OldEnd = EndPointer();
    bool WasSmall = isSmall();
  
    // Install the new array.  Clear all the buckets to empty.
    const void **NewBuckets = (const void**) safe_malloc(sizeof(void*) * NewSize);
  
    // Reset member only if memory was allocated successfully
    CurArray = NewBuckets;
    CurArraySize = NewSize;
    memset(CurArray, -1, NewSize*sizeof(void*));
  
    // Copy over all valid entries.
    for (const void **BucketPtr = OldBuckets; BucketPtr != OldEnd; ++BucketPtr) {
      // Copy over the element if it is valid.
      const void *Elt = *BucketPtr;
      if (Elt != getTombstoneMarker() && Elt != getEmptyMarker())
        *const_cast<void**>(FindBucketFor(Elt)) = const_cast<void*>(Elt);
    }
  
    if (!WasSmall)
      free(OldBuckets);
    NumNonEmpty -= NumTombstones;
    NumTombstones = 0;
  }
  
  SmallPtrSetImplBase::SmallPtrSetImplBase(const void **SmallStorage,
                                           const SmallPtrSetImplBase &that) {
    SmallArray = SmallStorage;
  
    // If we're becoming small, prepare to insert into our stack space
    if (that.isSmall()) {
      CurArray = SmallArray;
    // Otherwise, allocate new heap space (unless we were the same size)
    } else {
      CurArray = (const void**)safe_malloc(sizeof(void*) * that.CurArraySize);
    }
  
    // Copy over the that array.
    CopyHelper(that);
  }
  
  SmallPtrSetImplBase::SmallPtrSetImplBase(const void **SmallStorage,
                                           unsigned SmallSize,
                                           SmallPtrSetImplBase &&that) {
    SmallArray = SmallStorage;
    MoveHelper(SmallSize, std::move(that));
  }
  
  void SmallPtrSetImplBase::CopyFrom(const SmallPtrSetImplBase &RHS) {
    assert(&RHS != this && "Self-copy should be handled by the caller.");
  
    if (isSmall() && RHS.isSmall())
      assert(CurArraySize == RHS.CurArraySize &&
             "Cannot assign sets with different small sizes");
  
    // If we're becoming small, prepare to insert into our stack space
    if (RHS.isSmall()) {
      if (!isSmall())
        free(CurArray);
      CurArray = SmallArray;
    // Otherwise, allocate new heap space (unless we were the same size)
    } else if (CurArraySize != RHS.CurArraySize) {
      if (isSmall())
        CurArray = (const void**)safe_malloc(sizeof(void*) * RHS.CurArraySize);
      else {
        const void **T = (const void**)safe_realloc(CurArray,
                                               sizeof(void*) * RHS.CurArraySize);
        CurArray = T;
      }
    }
  
    CopyHelper(RHS);
  }
  
  void SmallPtrSetImplBase::CopyHelper(const SmallPtrSetImplBase &RHS) {
    // Copy over the new array size
    CurArraySize = RHS.CurArraySize;
  
    // Copy over the contents from the other set
    std::copy(RHS.CurArray, RHS.EndPointer(), CurArray);
  
    NumNonEmpty = RHS.NumNonEmpty;
    NumTombstones = RHS.NumTombstones;
  }
  
  void SmallPtrSetImplBase::MoveFrom(unsigned SmallSize,
                                     SmallPtrSetImplBase &&RHS) {
    if (!isSmall())
      free(CurArray);
    MoveHelper(SmallSize, std::move(RHS));
  }
  
  void SmallPtrSetImplBase::MoveHelper(unsigned SmallSize,
                                       SmallPtrSetImplBase &&RHS) {
    assert(&RHS != this && "Self-move should be handled by the caller.");
  
    if (RHS.isSmall()) {
      // Copy a small RHS rather than moving.
      CurArray = SmallArray;
      std::copy(RHS.CurArray, RHS.CurArray + RHS.NumNonEmpty, CurArray);
    } else {
      CurArray = RHS.CurArray;
      RHS.CurArray = RHS.SmallArray;
    }
  
    // Copy the rest of the trivial members.
    CurArraySize = RHS.CurArraySize;
    NumNonEmpty = RHS.NumNonEmpty;
    NumTombstones = RHS.NumTombstones;
  
    // Make the RHS small and empty.
    RHS.CurArraySize = SmallSize;
    assert(RHS.CurArray == RHS.SmallArray);
    RHS.NumNonEmpty = 0;
    RHS.NumTombstones = 0;
  }
  
  void SmallPtrSetImplBase::swap(SmallPtrSetImplBase &RHS) {
    if (this == &RHS) return;
  
    // We can only avoid copying elements if neither set is small.
    if (!this->isSmall() && !RHS.isSmall()) {
      std::swap(this->CurArray, RHS.CurArray);
      std::swap(this->CurArraySize, RHS.CurArraySize);
      std::swap(this->NumNonEmpty, RHS.NumNonEmpty);
      std::swap(this->NumTombstones, RHS.NumTombstones);
      return;
    }
  
    // FIXME: From here on we assume that both sets have the same small size.
  
    // If only RHS is small, copy the small elements into LHS and move the pointer
    // from LHS to RHS.
    if (!this->isSmall() && RHS.isSmall()) {
      assert(RHS.CurArray == RHS.SmallArray);
      std::copy(RHS.CurArray, RHS.CurArray + RHS.NumNonEmpty, this->SmallArray);
      std::swap(RHS.CurArraySize, this->CurArraySize);
      std::swap(this->NumNonEmpty, RHS.NumNonEmpty);
      std::swap(this->NumTombstones, RHS.NumTombstones);
      RHS.CurArray = this->CurArray;
      this->CurArray = this->SmallArray;
      return;
    }
  
    // If only LHS is small, copy the small elements into RHS and move the pointer
    // from RHS to LHS.
    if (this->isSmall() && !RHS.isSmall()) {
      assert(this->CurArray == this->SmallArray);
      std::copy(this->CurArray, this->CurArray + this->NumNonEmpty,
                RHS.SmallArray);
      std::swap(RHS.CurArraySize, this->CurArraySize);
      std::swap(RHS.NumNonEmpty, this->NumNonEmpty);
      std::swap(RHS.NumTombstones, this->NumTombstones);
      this->CurArray = RHS.CurArray;
      RHS.CurArray = RHS.SmallArray;
      return;
    }
  
    // Both a small, just swap the small elements.
    assert(this->isSmall() && RHS.isSmall());
    unsigned MinNonEmpty = std::min(this->NumNonEmpty, RHS.NumNonEmpty);
    std::swap_ranges(this->SmallArray, this->SmallArray + MinNonEmpty,
                     RHS.SmallArray);
    if (this->NumNonEmpty > MinNonEmpty) {
      std::copy(this->SmallArray + MinNonEmpty,
                this->SmallArray + this->NumNonEmpty,
                RHS.SmallArray + MinNonEmpty);
    } else {
      std::copy(RHS.SmallArray + MinNonEmpty, RHS.SmallArray + RHS.NumNonEmpty,
                this->SmallArray + MinNonEmpty);
    }
    assert(this->CurArraySize == RHS.CurArraySize);
    std::swap(this->NumNonEmpty, RHS.NumNonEmpty);
    std::swap(this->NumTombstones, RHS.NumTombstones);
  }
  