1 //===- llvm/ADT/SmallBitVector.h - 'Normally small' bit vectors -*- C++ -*-===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file implements the SmallBitVector class.
12 //===----------------------------------------------------------------------===//
14 #ifndef LLVM_ADT_SMALLBITVECTOR_H
15 #define LLVM_ADT_SMALLBITVECTOR_H
17 #include "llvm/ADT/BitVector.h"
18 #include "llvm/ADT/iterator_range.h"
19 #include "llvm/Support/MathExtras.h"
30 /// This is a 'bitvector' (really, a variable-sized bit array), optimized for
31 /// the case when the array is small. It contains one pointer-sized field, which
32 /// is directly used as a plain collection of bits when possible, or as a
33 /// pointer to a larger heap-allocated array when necessary. This allows normal
34 /// "small" cases to be fast without losing generality for large inputs.
35 class SmallBitVector {
36 // TODO: In "large" mode, a pointer to a BitVector is used, leading to an
37 // unnecessary level of indirection. It would be more efficient to use a
38 // pointer to memory containing size, allocation size, and the array of bits.
42 // The number of bits in this class.
43 NumBaseBits = sizeof(uintptr_t) * CHAR_BIT,
45 // One bit is used to discriminate between small and large mode. The
46 // remaining bits are used for the small-mode representation.
47 SmallNumRawBits = NumBaseBits - 1,
49 // A few more bits are used to store the size of the bit set in small mode.
50 // Theoretically this is a ceil-log2. These bits are encoded in the most
51 // significant bits of the raw bits.
52 SmallNumSizeBits = (NumBaseBits == 32 ? 5 :
53 NumBaseBits == 64 ? 6 :
56 // The remaining bits are used to store the actual set in small mode.
57 SmallNumDataBits = SmallNumRawBits - SmallNumSizeBits
60 static_assert(NumBaseBits == 64 || NumBaseBits == 32,
61 "Unsupported word size");
64 using size_type = unsigned;
66 // Encapsulation of a single bit.
68 SmallBitVector &TheVector;
72 reference(SmallBitVector &b, unsigned Idx) : TheVector(b), BitPos(Idx) {}
74 reference(const reference&) = default;
76 reference& operator=(reference t) {
81 reference& operator=(bool t) {
83 TheVector.set(BitPos);
85 TheVector.reset(BitPos);
89 operator bool() const {
90 return const_cast<const SmallBitVector &>(TheVector).operator[](BitPos);
95 bool isSmall() const {
96 return X & uintptr_t(1);
99 BitVector *getPointer() const {
101 return reinterpret_cast<BitVector *>(X);
104 void switchToSmall(uintptr_t NewSmallBits, size_t NewSize) {
106 setSmallSize(NewSize);
107 setSmallBits(NewSmallBits);
110 void switchToLarge(BitVector *BV) {
111 X = reinterpret_cast<uintptr_t>(BV);
112 assert(!isSmall() && "Tried to use an unaligned pointer");
115 // Return all the bits used for the "small" representation; this includes
116 // bits for the size as well as the element bits.
117 uintptr_t getSmallRawBits() const {
122 void setSmallRawBits(uintptr_t NewRawBits) {
124 X = (NewRawBits << 1) | uintptr_t(1);
128 size_t getSmallSize() const { return getSmallRawBits() >> SmallNumDataBits; }
130 void setSmallSize(size_t Size) {
131 setSmallRawBits(getSmallBits() | (Size << SmallNumDataBits));
134 // Return the element bits.
135 uintptr_t getSmallBits() const {
136 return getSmallRawBits() & ~(~uintptr_t(0) << getSmallSize());
139 void setSmallBits(uintptr_t NewBits) {
140 setSmallRawBits((NewBits & ~(~uintptr_t(0) << getSmallSize())) |
141 (getSmallSize() << SmallNumDataBits));
145 /// Creates an empty bitvector.
146 SmallBitVector() = default;
148 /// Creates a bitvector of specified number of bits. All bits are initialized
149 /// to the specified value.
150 explicit SmallBitVector(unsigned s, bool t = false) {
151 if (s <= SmallNumDataBits)
152 switchToSmall(t ? ~uintptr_t(0) : 0, s);
154 switchToLarge(new BitVector(s, t));
157 /// SmallBitVector copy ctor.
158 SmallBitVector(const SmallBitVector &RHS) {
162 switchToLarge(new BitVector(*RHS.getPointer()));
165 SmallBitVector(SmallBitVector &&RHS) : X(RHS.X) {
174 using const_set_bits_iterator = const_set_bits_iterator_impl<SmallBitVector>;
175 using set_iterator = const_set_bits_iterator;
177 const_set_bits_iterator set_bits_begin() const {
178 return const_set_bits_iterator(*this);
181 const_set_bits_iterator set_bits_end() const {
182 return const_set_bits_iterator(*this, -1);
185 iterator_range<const_set_bits_iterator> set_bits() const {
186 return make_range(set_bits_begin(), set_bits_end());
189 /// Tests whether there are no bits in this bitvector.
191 return isSmall() ? getSmallSize() == 0 : getPointer()->empty();
194 /// Returns the number of bits in this bitvector.
195 size_t size() const {
196 return isSmall() ? getSmallSize() : getPointer()->size();
199 /// Returns the number of bits which are set.
200 size_type count() const {
202 uintptr_t Bits = getSmallBits();
203 return countPopulation(Bits);
205 return getPointer()->count();
208 /// Returns true if any bit is set.
211 return getSmallBits() != 0;
212 return getPointer()->any();
215 /// Returns true if all bits are set.
218 return getSmallBits() == (uintptr_t(1) << getSmallSize()) - 1;
219 return getPointer()->all();
222 /// Returns true if none of the bits are set.
225 return getSmallBits() == 0;
226 return getPointer()->none();
229 /// Returns the index of the first set bit, -1 if none of the bits are set.
230 int find_first() const {
232 uintptr_t Bits = getSmallBits();
235 return countTrailingZeros(Bits);
237 return getPointer()->find_first();
240 int find_last() const {
242 uintptr_t Bits = getSmallBits();
245 return NumBaseBits - countLeadingZeros(Bits);
247 return getPointer()->find_last();
250 /// Returns the index of the first unset bit, -1 if all of the bits are set.
251 int find_first_unset() const {
253 if (count() == getSmallSize())
256 uintptr_t Bits = getSmallBits();
257 return countTrailingOnes(Bits);
259 return getPointer()->find_first_unset();
262 int find_last_unset() const {
264 if (count() == getSmallSize())
267 uintptr_t Bits = getSmallBits();
268 return NumBaseBits - countLeadingOnes(Bits);
270 return getPointer()->find_last_unset();
273 /// Returns the index of the next set bit following the "Prev" bit.
274 /// Returns -1 if the next set bit is not found.
275 int find_next(unsigned Prev) const {
277 uintptr_t Bits = getSmallBits();
278 // Mask off previous bits.
279 Bits &= ~uintptr_t(0) << (Prev + 1);
280 if (Bits == 0 || Prev + 1 >= getSmallSize())
282 return countTrailingZeros(Bits);
284 return getPointer()->find_next(Prev);
287 /// Returns the index of the next unset bit following the "Prev" bit.
288 /// Returns -1 if the next unset bit is not found.
289 int find_next_unset(unsigned Prev) const {
292 uintptr_t Bits = getSmallBits();
293 // Mask in previous bits.
294 uintptr_t Mask = (1 << Prev) - 1;
297 if (Bits == ~uintptr_t(0) || Prev + 1 >= getSmallSize())
299 return countTrailingOnes(Bits);
301 return getPointer()->find_next_unset(Prev);
304 /// find_prev - Returns the index of the first set bit that precedes the
305 /// the bit at \p PriorTo. Returns -1 if all previous bits are unset.
306 int find_prev(unsigned PriorTo) const {
312 uintptr_t Bits = getSmallBits();
313 Bits &= maskTrailingOnes<uintptr_t>(PriorTo + 1);
317 return NumBaseBits - countLeadingZeros(Bits) - 1;
319 return getPointer()->find_prev(PriorTo);
329 /// Grow or shrink the bitvector.
330 void resize(unsigned N, bool t = false) {
332 getPointer()->resize(N, t);
333 } else if (SmallNumDataBits >= N) {
334 uintptr_t NewBits = t ? ~uintptr_t(0) << getSmallSize() : 0;
336 setSmallBits(NewBits | getSmallBits());
338 BitVector *BV = new BitVector(N, t);
339 uintptr_t OldBits = getSmallBits();
340 for (size_t i = 0, e = getSmallSize(); i != e; ++i)
341 (*BV)[i] = (OldBits >> i) & 1;
346 void reserve(unsigned N) {
348 if (N > SmallNumDataBits) {
349 uintptr_t OldBits = getSmallRawBits();
350 size_t SmallSize = getSmallSize();
351 BitVector *BV = new BitVector(SmallSize);
352 for (size_t i = 0; i < SmallSize; ++i)
353 if ((OldBits >> i) & 1)
359 getPointer()->reserve(N);
364 SmallBitVector &set() {
366 setSmallBits(~uintptr_t(0));
372 SmallBitVector &set(unsigned Idx) {
374 assert(Idx <= static_cast<unsigned>(
375 std::numeric_limits<uintptr_t>::digits) &&
376 "undefined behavior");
377 setSmallBits(getSmallBits() | (uintptr_t(1) << Idx));
380 getPointer()->set(Idx);
384 /// Efficiently set a range of bits in [I, E)
385 SmallBitVector &set(unsigned I, unsigned E) {
386 assert(I <= E && "Attempted to set backwards range!");
387 assert(E <= size() && "Attempted to set out-of-bounds range!");
388 if (I == E) return *this;
390 uintptr_t EMask = ((uintptr_t)1) << E;
391 uintptr_t IMask = ((uintptr_t)1) << I;
392 uintptr_t Mask = EMask - IMask;
393 setSmallBits(getSmallBits() | Mask);
395 getPointer()->set(I, E);
399 SmallBitVector &reset() {
403 getPointer()->reset();
407 SmallBitVector &reset(unsigned Idx) {
409 setSmallBits(getSmallBits() & ~(uintptr_t(1) << Idx));
411 getPointer()->reset(Idx);
415 /// Efficiently reset a range of bits in [I, E)
416 SmallBitVector &reset(unsigned I, unsigned E) {
417 assert(I <= E && "Attempted to reset backwards range!");
418 assert(E <= size() && "Attempted to reset out-of-bounds range!");
419 if (I == E) return *this;
421 uintptr_t EMask = ((uintptr_t)1) << E;
422 uintptr_t IMask = ((uintptr_t)1) << I;
423 uintptr_t Mask = EMask - IMask;
424 setSmallBits(getSmallBits() & ~Mask);
426 getPointer()->reset(I, E);
430 SmallBitVector &flip() {
432 setSmallBits(~getSmallBits());
434 getPointer()->flip();
438 SmallBitVector &flip(unsigned Idx) {
440 setSmallBits(getSmallBits() ^ (uintptr_t(1) << Idx));
442 getPointer()->flip(Idx);
447 SmallBitVector operator~() const {
448 return SmallBitVector(*this).flip();
452 reference operator[](unsigned Idx) {
453 assert(Idx < size() && "Out-of-bounds Bit access.");
454 return reference(*this, Idx);
457 bool operator[](unsigned Idx) const {
458 assert(Idx < size() && "Out-of-bounds Bit access.");
460 return ((getSmallBits() >> Idx) & 1) != 0;
461 return getPointer()->operator[](Idx);
464 bool test(unsigned Idx) const {
468 /// Test if any common bits are set.
469 bool anyCommon(const SmallBitVector &RHS) const {
470 if (isSmall() && RHS.isSmall())
471 return (getSmallBits() & RHS.getSmallBits()) != 0;
472 if (!isSmall() && !RHS.isSmall())
473 return getPointer()->anyCommon(*RHS.getPointer());
475 for (unsigned i = 0, e = std::min(size(), RHS.size()); i != e; ++i)
476 if (test(i) && RHS.test(i))
481 // Comparison operators.
482 bool operator==(const SmallBitVector &RHS) const {
483 if (size() != RHS.size())
486 return getSmallBits() == RHS.getSmallBits();
488 return *getPointer() == *RHS.getPointer();
491 bool operator!=(const SmallBitVector &RHS) const {
492 return !(*this == RHS);
495 // Intersection, union, disjoint union.
496 SmallBitVector &operator&=(const SmallBitVector &RHS) {
497 resize(std::max(size(), RHS.size()));
499 setSmallBits(getSmallBits() & RHS.getSmallBits());
500 else if (!RHS.isSmall())
501 getPointer()->operator&=(*RHS.getPointer());
503 SmallBitVector Copy = RHS;
505 getPointer()->operator&=(*Copy.getPointer());
510 /// Reset bits that are set in RHS. Same as *this &= ~RHS.
511 SmallBitVector &reset(const SmallBitVector &RHS) {
512 if (isSmall() && RHS.isSmall())
513 setSmallBits(getSmallBits() & ~RHS.getSmallBits());
514 else if (!isSmall() && !RHS.isSmall())
515 getPointer()->reset(*RHS.getPointer());
517 for (unsigned i = 0, e = std::min(size(), RHS.size()); i != e; ++i)
524 /// Check if (This - RHS) is zero. This is the same as reset(RHS) and any().
525 bool test(const SmallBitVector &RHS) const {
526 if (isSmall() && RHS.isSmall())
527 return (getSmallBits() & ~RHS.getSmallBits()) != 0;
528 if (!isSmall() && !RHS.isSmall())
529 return getPointer()->test(*RHS.getPointer());
532 for (i = 0, e = std::min(size(), RHS.size()); i != e; ++i)
533 if (test(i) && !RHS.test(i))
536 for (e = size(); i != e; ++i)
543 SmallBitVector &operator|=(const SmallBitVector &RHS) {
544 resize(std::max(size(), RHS.size()));
546 setSmallBits(getSmallBits() | RHS.getSmallBits());
547 else if (!RHS.isSmall())
548 getPointer()->operator|=(*RHS.getPointer());
550 SmallBitVector Copy = RHS;
552 getPointer()->operator|=(*Copy.getPointer());
557 SmallBitVector &operator^=(const SmallBitVector &RHS) {
558 resize(std::max(size(), RHS.size()));
560 setSmallBits(getSmallBits() ^ RHS.getSmallBits());
561 else if (!RHS.isSmall())
562 getPointer()->operator^=(*RHS.getPointer());
564 SmallBitVector Copy = RHS;
566 getPointer()->operator^=(*Copy.getPointer());
571 SmallBitVector &operator<<=(unsigned N) {
573 setSmallBits(getSmallBits() << N);
575 getPointer()->operator<<=(N);
579 SmallBitVector &operator>>=(unsigned N) {
581 setSmallBits(getSmallBits() >> N);
583 getPointer()->operator>>=(N);
587 // Assignment operator.
588 const SmallBitVector &operator=(const SmallBitVector &RHS) {
593 switchToLarge(new BitVector(*RHS.getPointer()));
596 *getPointer() = *RHS.getPointer();
605 const SmallBitVector &operator=(SmallBitVector &&RHS) {
613 void swap(SmallBitVector &RHS) {
617 /// Add '1' bits from Mask to this vector. Don't resize.
618 /// This computes "*this |= Mask".
619 void setBitsInMask(const uint32_t *Mask, unsigned MaskWords = ~0u) {
621 applyMask<true, false>(Mask, MaskWords);
623 getPointer()->setBitsInMask(Mask, MaskWords);
626 /// Clear any bits in this vector that are set in Mask. Don't resize.
627 /// This computes "*this &= ~Mask".
628 void clearBitsInMask(const uint32_t *Mask, unsigned MaskWords = ~0u) {
630 applyMask<false, false>(Mask, MaskWords);
632 getPointer()->clearBitsInMask(Mask, MaskWords);
635 /// Add a bit to this vector for every '0' bit in Mask. Don't resize.
636 /// This computes "*this |= ~Mask".
637 void setBitsNotInMask(const uint32_t *Mask, unsigned MaskWords = ~0u) {
639 applyMask<true, true>(Mask, MaskWords);
641 getPointer()->setBitsNotInMask(Mask, MaskWords);
644 /// Clear a bit in this vector for every '0' bit in Mask. Don't resize.
645 /// This computes "*this &= Mask".
646 void clearBitsNotInMask(const uint32_t *Mask, unsigned MaskWords = ~0u) {
648 applyMask<false, true>(Mask, MaskWords);
650 getPointer()->clearBitsNotInMask(Mask, MaskWords);
654 template <bool AddBits, bool InvertMask>
655 void applyMask(const uint32_t *Mask, unsigned MaskWords) {
656 assert(MaskWords <= sizeof(uintptr_t) && "Mask is larger than base!");
657 uintptr_t M = Mask[0];
658 if (NumBaseBits == 64)
659 M |= uint64_t(Mask[1]) << 32;
663 setSmallBits(getSmallBits() | M);
665 setSmallBits(getSmallBits() & ~M);
669 inline SmallBitVector
670 operator&(const SmallBitVector &LHS, const SmallBitVector &RHS) {
671 SmallBitVector Result(LHS);
676 inline SmallBitVector
677 operator|(const SmallBitVector &LHS, const SmallBitVector &RHS) {
678 SmallBitVector Result(LHS);
683 inline SmallBitVector
684 operator^(const SmallBitVector &LHS, const SmallBitVector &RHS) {
685 SmallBitVector Result(LHS);
690 } // end namespace llvm
694 /// Implement std::swap in terms of BitVector swap.
696 swap(llvm::SmallBitVector &LHS, llvm::SmallBitVector &RHS) {
700 } // end namespace std
702 #endif // LLVM_ADT_SMALLBITVECTOR_H