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//===- llvm/ADT/SmallBitVector.h - 'Normally small' bit vectors -*- C++ -*-===//

//

// 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

//

//===----------------------------------------------------------------------===//

///

/// \file

/// This file implements the SmallBitVector class.

///

//===----------------------------------------------------------------------===//

#ifndef LLVM_ADT_SMALLBITVECTOR_H

#define LLVM_ADT_SMALLBITVECTOR_H

#include "llvm/ADT/BitVector.h"

#include "llvm/ADT/iterator_range.h"

#include "llvm/Support/MathExtras.h"

#include <algorithm>

#include <cassert>

#include <climits>

#include <cstddef>

#include <cstdint>

#include <limits>

#include <utility>

namespace llvm {

/// This is a 'bitvector' (really, a variable-sized bit array), optimized for

/// the case when the array is small. It contains one pointer-sized field, which

/// is directly used as a plain collection of bits when possible, or as a

/// pointer to a larger heap-allocated array when necessary. This allows normal

/// "small" cases to be fast without losing generality for large inputs.

class SmallBitVector {

  // TODO: In "large" mode, a pointer to a BitVector is used, leading to an

  // unnecessary level of indirection. It would be more efficient to use a

  // pointer to memory containing size, allocation size, and the array of bits.

  uintptr_t X = 1;

  enum {

    // The number of bits in this class.

    NumBaseBits = sizeof(uintptr_t) * CHAR_BIT,

    // One bit is used to discriminate between small and large mode. The

    // remaining bits are used for the small-mode representation.

    SmallNumRawBits = NumBaseBits - 1,

    // A few more bits are used to store the size of the bit set in small mode.

    // Theoretically this is a ceil-log2. These bits are encoded in the most

    // significant bits of the raw bits.

    SmallNumSizeBits = (NumBaseBits == 32 ? 5 :

                        NumBaseBits == 64 ? 6 :

                        SmallNumRawBits),

    // The remaining bits are used to store the actual set in small mode.

    SmallNumDataBits = SmallNumRawBits - SmallNumSizeBits

  };

  static_assert(NumBaseBits == 64 || NumBaseBits == 32,

                "Unsupported word size");

public:

  using size_type = uintptr_t;

  // Encapsulation of a single bit.

  class reference {

    SmallBitVector &TheVector;

    unsigned BitPos;

  public:

    reference(SmallBitVector &b, unsigned Idx) : TheVector(b), BitPos(Idx) {}

    reference(const reference&) = default;

    reference& operator=(reference t) {

      *this = bool(t);

      return *this;

    }

    reference& operator=(bool t) {

      if (t)

        TheVector.set(BitPos);

      else

        TheVector.reset(BitPos);

      return *this;

    }

    operator bool() const {

      return const_cast<const SmallBitVector &>(TheVector).operator[](BitPos);

    }

  };

private:

  BitVector *getPointer() const {

    assert(!isSmall());

    return reinterpret_cast<BitVector *>(X);

  }

  void switchToSmall(uintptr_t NewSmallBits, size_type NewSize) {

    X = 1;

    setSmallSize(NewSize);

    setSmallBits(NewSmallBits);

  }

  void switchToLarge(BitVector *BV) {

    X = reinterpret_cast<uintptr_t>(BV);

    assert(!isSmall() && "Tried to use an unaligned pointer");

  }

  // Return all the bits used for the "small" representation; this includes

  // bits for the size as well as the element bits.

  uintptr_t getSmallRawBits() const {

    assert(isSmall());

    return X >> 1;

  }

  void setSmallRawBits(uintptr_t NewRawBits) {

    assert(isSmall());

    X = (NewRawBits << 1) | uintptr_t(1);

  }

  // Return the size.

  size_type getSmallSize() const {

    return getSmallRawBits() >> SmallNumDataBits;

  }

  void setSmallSize(size_type Size) {

    setSmallRawBits(getSmallBits() | (Size << SmallNumDataBits));

  }

  // Return the element bits.

  uintptr_t getSmallBits() const {

    return getSmallRawBits() & ~(~uintptr_t(0) << getSmallSize());

  }

  void setSmallBits(uintptr_t NewBits) {

    setSmallRawBits((NewBits & ~(~uintptr_t(0) << getSmallSize())) |

                    (getSmallSize() << SmallNumDataBits));

  }

public:

  /// Creates an empty bitvector.

  SmallBitVector() = default;

  /// Creates a bitvector of specified number of bits. All bits are initialized

  /// to the specified value.

  explicit SmallBitVector(unsigned s, bool t = false) {

    if (s <= SmallNumDataBits)

      switchToSmall(t ? ~uintptr_t(0) : 0, s);

    else

      switchToLarge(new BitVector(s, t));

  }

  /// SmallBitVector copy ctor.

  SmallBitVector(const SmallBitVector &RHS) {

    if (RHS.isSmall())

      X = RHS.X;

    else

      switchToLarge(new BitVector(*RHS.getPointer()));

  }

  SmallBitVector(SmallBitVector &&RHS) : X(RHS.X) {

    RHS.X = 1;

  }

  ~SmallBitVector() {

    if (!isSmall())

      delete getPointer();

  }

  using const_set_bits_iterator = const_set_bits_iterator_impl<SmallBitVector>;

  using set_iterator = const_set_bits_iterator;

  const_set_bits_iterator set_bits_begin() const {

    return const_set_bits_iterator(*this);

  }

  const_set_bits_iterator set_bits_end() const {

    return const_set_bits_iterator(*this, -1);

  }

  iterator_range<const_set_bits_iterator> set_bits() const {

    return make_range(set_bits_begin(), set_bits_end());

  }

  bool isSmall() const { return X & uintptr_t(1); }

  /// Tests whether there are no bits in this bitvector.

  bool empty() const {

    return isSmall() ? getSmallSize() == 0 : getPointer()->empty();

  }

  /// Returns the number of bits in this bitvector.

  size_type size() const {

    return isSmall() ? getSmallSize() : getPointer()->size();

  }

  /// Returns the number of bits which are set.

  size_type count() const {

    if (isSmall()) {

      uintptr_t Bits = getSmallBits();

      return llvm::popcount(Bits);

    }

    return getPointer()->count();

  }

  /// Returns true if any bit is set.

  bool any() const {

    if (isSmall())

      return getSmallBits() != 0;

    return getPointer()->any();

  }

  /// Returns true if all bits are set.

  bool all() const {

    if (isSmall())

      return getSmallBits() == (uintptr_t(1) << getSmallSize()) - 1;

    return getPointer()->all();

  }

  /// Returns true if none of the bits are set.

  bool none() const {

    if (isSmall())

      return getSmallBits() == 0;

    return getPointer()->none();

  }

  /// Returns the index of the first set bit, -1 if none of the bits are set.

  int find_first() const {

    if (isSmall()) {

      uintptr_t Bits = getSmallBits();

      if (Bits == 0)

        return -1;

      return countTrailingZeros(Bits);

    }

    return getPointer()->find_first();

  }

  int find_last() const {

    if (isSmall()) {

      uintptr_t Bits = getSmallBits();

      if (Bits == 0)

        return -1;

      return NumBaseBits - countLeadingZeros(Bits) - 1;

    }

    return getPointer()->find_last();

  }

  /// Returns the index of the first unset bit, -1 if all of the bits are set.

  int find_first_unset() const {

    if (isSmall()) {

      if (count() == getSmallSize())

        return -1;

      uintptr_t Bits = getSmallBits();

      return countTrailingOnes(Bits);

    }

    return getPointer()->find_first_unset();

  }

  int find_last_unset() const {

    if (isSmall()) {

      if (count() == getSmallSize())

        return -1;

      uintptr_t Bits = getSmallBits();

      // Set unused bits.

      Bits |= ~uintptr_t(0) << getSmallSize();

      return NumBaseBits - countLeadingOnes(Bits) - 1;

    }

    return getPointer()->find_last_unset();

  }

  /// Returns the index of the next set bit following the "Prev" bit.

  /// Returns -1 if the next set bit is not found.

  int find_next(unsigned Prev) const {

    if (isSmall()) {

      uintptr_t Bits = getSmallBits();

      // Mask off previous bits.

      Bits &= ~uintptr_t(0) << (Prev + 1);

      if (Bits == 0 || Prev + 1 >= getSmallSize())

        return -1;

      return countTrailingZeros(Bits);

    }

    return getPointer()->find_next(Prev);

  }

  /// Returns the index of the next unset bit following the "Prev" bit.

  /// Returns -1 if the next unset bit is not found.

  int find_next_unset(unsigned Prev) const {

    if (isSmall()) {

      uintptr_t Bits = getSmallBits();

      // Mask in previous bits.

      Bits |= (uintptr_t(1) << (Prev + 1)) - 1;

      // Mask in unused bits.

      Bits |= ~uintptr_t(0) << getSmallSize();

      if (Bits == ~uintptr_t(0) || Prev + 1 >= getSmallSize())

        return -1;

      return countTrailingOnes(Bits);

    }

    return getPointer()->find_next_unset(Prev);

  }

  /// find_prev - Returns the index of the first set bit that precedes the

  /// the bit at \p PriorTo.  Returns -1 if all previous bits are unset.

  int find_prev(unsigned PriorTo) const {

    if (isSmall()) {

      if (PriorTo == 0)

        return -1;

      --PriorTo;

      uintptr_t Bits = getSmallBits();

      Bits &= maskTrailingOnes<uintptr_t>(PriorTo + 1);

      if (Bits == 0)

        return -1;

      return NumBaseBits - countLeadingZeros(Bits) - 1;

    }

    return getPointer()->find_prev(PriorTo);

  }

  /// Clear all bits.

  void clear() {

    if (!isSmall())

      delete getPointer();

    switchToSmall(0, 0);

  }

  /// Grow or shrink the bitvector.

  void resize(unsigned N, bool t = false) {

    if (!isSmall()) {

      getPointer()->resize(N, t);

    } else if (SmallNumDataBits >= N) {

      uintptr_t NewBits = t ? ~uintptr_t(0) << getSmallSize() : 0;

      setSmallSize(N);

      setSmallBits(NewBits | getSmallBits());

    } else {

      BitVector *BV = new BitVector(N, t);

      uintptr_t OldBits = getSmallBits();

      for (size_type I = 0, E = getSmallSize(); I != E; ++I)

        (*BV)[I] = (OldBits >> I) & 1;

      switchToLarge(BV);

    }

  }

  void reserve(unsigned N) {

    if (isSmall()) {

      if (N > SmallNumDataBits) {

        uintptr_t OldBits = getSmallRawBits();

        size_type SmallSize = getSmallSize();

        BitVector *BV = new BitVector(SmallSize);

        for (size_type I = 0; I < SmallSize; ++I)

          if ((OldBits >> I) & 1)

            BV->set(I);

        BV->reserve(N);

        switchToLarge(BV);

      }

    } else {

      getPointer()->reserve(N);

    }

  }

  // Set, reset, flip

  SmallBitVector &set() {

    if (isSmall())

      setSmallBits(~uintptr_t(0));

    else

      getPointer()->set();

    return *this;

  }

  SmallBitVector &set(unsigned Idx) {

    if (isSmall()) {

      assert(Idx <= static_cast<unsigned>(

                        std::numeric_limits<uintptr_t>::digits) &&

             "undefined behavior");

      setSmallBits(getSmallBits() | (uintptr_t(1) << Idx));

    }

    else

      getPointer()->set(Idx);

    return *this;

  }

  /// Efficiently set a range of bits in [I, E)

  SmallBitVector &set(unsigned I, unsigned E) {

    assert(I <= E && "Attempted to set backwards range!");

    assert(E <= size() && "Attempted to set out-of-bounds range!");

    if (I == E) return *this;

    if (isSmall()) {

      uintptr_t EMask = ((uintptr_t)1) << E;

      uintptr_t IMask = ((uintptr_t)1) << I;

      uintptr_t Mask = EMask - IMask;

      setSmallBits(getSmallBits() | Mask);

    } else

      getPointer()->set(I, E);

    return *this;

  }

  SmallBitVector &reset() {

    if (isSmall())

      setSmallBits(0);

    else

      getPointer()->reset();

    return *this;

  }

  SmallBitVector &reset(unsigned Idx) {

    if (isSmall())

      setSmallBits(getSmallBits() & ~(uintptr_t(1) << Idx));

    else

      getPointer()->reset(Idx);

    return *this;

  }

  /// Efficiently reset a range of bits in [I, E)

  SmallBitVector &reset(unsigned I, unsigned E) {

    assert(I <= E && "Attempted to reset backwards range!");

    assert(E <= size() && "Attempted to reset out-of-bounds range!");

    if (I == E) return *this;

    if (isSmall()) {

      uintptr_t EMask = ((uintptr_t)1) << E;

      uintptr_t IMask = ((uintptr_t)1) << I;

      uintptr_t Mask = EMask - IMask;

      setSmallBits(getSmallBits() & ~Mask);

    } else

      getPointer()->reset(I, E);

    return *this;

  }

  SmallBitVector &flip() {

    if (isSmall())

      setSmallBits(~getSmallBits());

    else

      getPointer()->flip();

    return *this;

  }

  SmallBitVector &flip(unsigned Idx) {

    if (isSmall())

      setSmallBits(getSmallBits() ^ (uintptr_t(1) << Idx));

    else

      getPointer()->flip(Idx);

    return *this;

  }

  // No argument flip.

  SmallBitVector operator~() const {

    return SmallBitVector(*this).flip();

  }

  // Indexing.

  reference operator[](unsigned Idx) {

    assert(Idx < size() && "Out-of-bounds Bit access.");

    return reference(*this, Idx);

  }

  bool operator[](unsigned Idx) const {

    assert(Idx < size() && "Out-of-bounds Bit access.");

    if (isSmall())

      return ((getSmallBits() >> Idx) & 1) != 0;

    return getPointer()->operator[](Idx);

  }

  /// Return the last element in the vector.

  bool back() const {

    assert(!empty() && "Getting last element of empty vector.");

    return (*this)[size() - 1];

  }

  bool test(unsigned Idx) const {

    return (*this)[Idx];

  }

  // Push single bit to end of vector.

  void push_back(bool Val) {

    resize(size() + 1, Val);

  }

  /// Pop one bit from the end of the vector.

  void pop_back() {

    assert(!empty() && "Empty vector has no element to pop.");

    resize(size() - 1);

  }

  /// Test if any common bits are set.

  bool anyCommon(const SmallBitVector &RHS) const {

    if (isSmall() && RHS.isSmall())

      return (getSmallBits() & RHS.getSmallBits()) != 0;

    if (!isSmall() && !RHS.isSmall())

      return getPointer()->anyCommon(*RHS.getPointer());

    for (unsigned i = 0, e = std::min(size(), RHS.size()); i != e; ++i)

      if (test(i) && RHS.test(i))

        return true;

    return false;

  }

  // Comparison operators.

  bool operator==(const SmallBitVector &RHS) const {

    if (size() != RHS.size())

      return false;

    if (isSmall() && RHS.isSmall())

      return getSmallBits() == RHS.getSmallBits();

    else if (!isSmall() && !RHS.isSmall())

      return *getPointer() == *RHS.getPointer();

    else {

      for (size_type I = 0, E = size(); I != E; ++I) {

        if ((*this)[I] != RHS[I])

          return false;

      }

      return true;

    }

  }

  bool operator!=(const SmallBitVector &RHS) const {

    return !(*this == RHS);

  }

  // Intersection, union, disjoint union.

  // FIXME BitVector::operator&= does not resize the LHS but this does

  SmallBitVector &operator&=(const SmallBitVector &RHS) {

    resize(std::max(size(), RHS.size()));

    if (isSmall() && RHS.isSmall())

      setSmallBits(getSmallBits() & RHS.getSmallBits());

    else if (!isSmall() && !RHS.isSmall())

      getPointer()->operator&=(*RHS.getPointer());

    else {

      size_type I, E;

      for (I = 0, E = std::min(size(), RHS.size()); I != E; ++I)

        (*this)[I] = test(I) && RHS.test(I);

      for (E = size(); I != E; ++I)

        reset(I);

    }

    return *this;

  }

  /// Reset bits that are set in RHS. Same as *this &= ~RHS.

  SmallBitVector &reset(const SmallBitVector &RHS) {

    if (isSmall() && RHS.isSmall())

      setSmallBits(getSmallBits() & ~RHS.getSmallBits());

    else if (!isSmall() && !RHS.isSmall())

      getPointer()->reset(*RHS.getPointer());

    else

      for (unsigned i = 0, e = std::min(size(), RHS.size()); i != e; ++i)

        if (RHS.test(i))

          reset(i);

    return *this;

  }

  /// Check if (This - RHS) is zero. This is the same as reset(RHS) and any().

  bool test(const SmallBitVector &RHS) const {

    if (isSmall() && RHS.isSmall())

      return (getSmallBits() & ~RHS.getSmallBits()) != 0;

    if (!isSmall() && !RHS.isSmall())

      return getPointer()->test(*RHS.getPointer());

    unsigned i, e;

    for (i = 0, e = std::min(size(), RHS.size()); i != e; ++i)

      if (test(i) && !RHS.test(i))

        return true;

    for (e = size(); i != e; ++i)

      if (test(i))

        return true;

    return false;

  }

  SmallBitVector &operator|=(const SmallBitVector &RHS) {

    resize(std::max(size(), RHS.size()));

    if (isSmall() && RHS.isSmall())

      setSmallBits(getSmallBits() | RHS.getSmallBits());

    else if (!isSmall() && !RHS.isSmall())

      getPointer()->operator|=(*RHS.getPointer());

    else {

      for (size_type I = 0, E = RHS.size(); I != E; ++I)

        (*this)[I] = test(I) || RHS.test(I);

    }

    return *this;

  }

  SmallBitVector &operator^=(const SmallBitVector &RHS) {

    resize(std::max(size(), RHS.size()));

    if (isSmall() && RHS.isSmall())

      setSmallBits(getSmallBits() ^ RHS.getSmallBits());

    else if (!isSmall() && !RHS.isSmall())

      getPointer()->operator^=(*RHS.getPointer());

    else {

      for (size_type I = 0, E = RHS.size(); I != E; ++I)

        (*this)[I] = test(I) != RHS.test(I);

    }

    return *this;

  }

  SmallBitVector &operator<<=(unsigned N) {

    if (isSmall())

      setSmallBits(getSmallBits() << N);

    else

      getPointer()->operator<<=(N);

    return *this;

  }

  SmallBitVector &operator>>=(unsigned N) {

    if (isSmall())

      setSmallBits(getSmallBits() >> N);

    else

      getPointer()->operator>>=(N);

    return *this;

  }

  // Assignment operator.

  const SmallBitVector &operator=(const SmallBitVector &RHS) {

    if (isSmall()) {

      if (RHS.isSmall())

        X = RHS.X;

      else

        switchToLarge(new BitVector(*RHS.getPointer()));

    } else {

      if (!RHS.isSmall())

        *getPointer() = *RHS.getPointer();

      else {

        delete getPointer();

        X = RHS.X;

      }

    }

    return *this;

  }

  const SmallBitVector &operator=(SmallBitVector &&RHS) {

    if (this != &RHS) {

      clear();

      swap(RHS);

    }

    return *this;

  }

  void swap(SmallBitVector &RHS) {

    std::swap(X, RHS.X);

  }

  /// Add '1' bits from Mask to this vector. Don't resize.

  /// This computes "*this |= Mask".

  void setBitsInMask(const uint32_t *Mask, unsigned MaskWords = ~0u) {

    if (isSmall())

      applyMask<true, false>(Mask, MaskWords);

    else

      getPointer()->setBitsInMask(Mask, MaskWords);

  }

  /// Clear any bits in this vector that are set in Mask. Don't resize.

  /// This computes "*this &= ~Mask".

  void clearBitsInMask(const uint32_t *Mask, unsigned MaskWords = ~0u) {

    if (isSmall())

      applyMask<false, false>(Mask, MaskWords);

    else

      getPointer()->clearBitsInMask(Mask, MaskWords);

  }

  /// Add a bit to this vector for every '0' bit in Mask. Don't resize.

  /// This computes "*this |= ~Mask".

  void setBitsNotInMask(const uint32_t *Mask, unsigned MaskWords = ~0u) {

    if (isSmall())

      applyMask<true, true>(Mask, MaskWords);

    else

      getPointer()->setBitsNotInMask(Mask, MaskWords);

  }

  /// Clear a bit in this vector for every '0' bit in Mask. Don't resize.

  /// This computes "*this &= Mask".

  void clearBitsNotInMask(const uint32_t *Mask, unsigned MaskWords = ~0u) {

    if (isSmall())

      applyMask<false, true>(Mask, MaskWords);

    else

      getPointer()->clearBitsNotInMask(Mask, MaskWords);

  }

  void invalid() {

    assert(empty());

    X = (uintptr_t)-1;

  }

  bool isInvalid() const { return X == (uintptr_t)-1; }

  ArrayRef<uintptr_t> getData(uintptr_t &Store) const {

    if (!isSmall())

      return getPointer()->getData();

    Store = getSmallBits();

    return Store;

  }

private:

  template <bool AddBits, bool InvertMask>

  void applyMask(const uint32_t *Mask, unsigned MaskWords) {

    assert(MaskWords <= sizeof(uintptr_t) && "Mask is larger than base!");

    uintptr_t M = Mask[0];

    if (NumBaseBits == 64)

      M |= uint64_t(Mask[1]) << 32;

    if (InvertMask)

      M = ~M;

    if (AddBits)

      setSmallBits(getSmallBits() | M);

    else

      setSmallBits(getSmallBits() & ~M);

  }

};

inline SmallBitVector