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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 llvm::countr_zero(Bits);
     }
     return getPointer()->find_first();
   }
 
   int find_last() const {
     if (isSmall()) {
       uintptr_t Bits = getSmallBits();
       if (Bits == 0)
         return -1;
       return NumBaseBits - llvm::countl_zero(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 llvm::countr_one(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 - llvm::countl_one(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 llvm::countr_zero(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 llvm::countr_one(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 - llvm::countl_zero(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
 operator&(const SmallBitVector &LHS, const SmallBitVector &RHS) {
   SmallBitVector Result(LHS);
   Result &= RHS;
   return Result;
 }
 
 inline SmallBitVector
 operator|(const SmallBitVector &LHS, const SmallBitVector &RHS) {
   SmallBitVector Result(LHS);
   Result |= RHS;
   return Result;
 }
 
 inline SmallBitVector
 operator^(const SmallBitVector &LHS, const SmallBitVector &RHS) {
   SmallBitVector Result(LHS);
   Result ^= RHS;
   return Result;
 }
 
 template <> struct DenseMapInfo<SmallBitVector> {
   static inline SmallBitVector getEmptyKey() { return SmallBitVector(); }
   static inline SmallBitVector getTombstoneKey() {
     SmallBitVector V;
     V.invalid();
     return V;
   }
   static unsigned getHashValue(const SmallBitVector &V) {
     uintptr_t Store;
     return DenseMapInfo<
         std::pair<SmallBitVector::size_type, ArrayRef<uintptr_t>>>::
         getHashValue(std::make_pair(V.size(), V.getData(Store)));
   }
   static bool isEqual(const SmallBitVector &LHS, const SmallBitVector &RHS) {
     if (LHS.isInvalid() || RHS.isInvalid())
       return LHS.isInvalid() == RHS.isInvalid();
     return LHS == RHS;
   }
 };
 } // end namespace llvm
 
 namespace std {
 
 /// Implement std::swap in terms of BitVector swap.
 inline void
 swap(llvm::SmallBitVector &LHS, llvm::SmallBitVector &RHS) {
   LHS.swap(RHS);
 }
 
 } // end namespace std
 
 #endif // LLVM_ADT_SMALLBITVECTOR_H

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