//===- 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;

  incrementEpoch();

  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);

}