1//===- llvm/ADT/SmallBitVector.h - 'Normally small' bit vectors -*- C++ -*-===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8//
9// This file implements the SmallBitVector class.
10//
11//===----------------------------------------------------------------------===//
12
13#ifndef LLVM_ADT_SMALLBITVECTOR_H
14#define LLVM_ADT_SMALLBITVECTOR_H
15
16#include "llvm/ADT/BitVector.h"
17#include "llvm/ADT/iterator_range.h"
18#include "llvm/Support/MathExtras.h"
19#include <algorithm>
20#include <cassert>
21#include <climits>
22#include <cstddef>
23#include <cstdint>
24#include <limits>
25#include <utility>
26
27namespace llvm {
28
29/// This is a 'bitvector' (really, a variable-sized bit array), optimized for
30/// the case when the array is small. It contains one pointer-sized field, which
31/// is directly used as a plain collection of bits when possible, or as a
32/// pointer to a larger heap-allocated array when necessary. This allows normal
33/// "small" cases to be fast without losing generality for large inputs.
34class SmallBitVector {
35 // TODO: In "large" mode, a pointer to a BitVector is used, leading to an
36 // unnecessary level of indirection. It would be more efficient to use a
37 // pointer to memory containing size, allocation size, and the array of bits.
38 uintptr_t X = 1;
39
40 enum {
41 // The number of bits in this class.
42 NumBaseBits = sizeof(uintptr_t) * CHAR_BIT,
43
44 // One bit is used to discriminate between small and large mode. The
45 // remaining bits are used for the small-mode representation.
46 SmallNumRawBits = NumBaseBits - 1,
47
48 // A few more bits are used to store the size of the bit set in small mode.
49 // Theoretically this is a ceil-log2. These bits are encoded in the most
50 // significant bits of the raw bits.
51 SmallNumSizeBits = (NumBaseBits == 32 ? 5 :
52 NumBaseBits == 64 ? 6 :
53 SmallNumRawBits),
54
55 // The remaining bits are used to store the actual set in small mode.
56 SmallNumDataBits = SmallNumRawBits - SmallNumSizeBits
57 };
58
59 static_assert(NumBaseBits == 64 || NumBaseBits == 32,
60 "Unsupported word size");
61
62public:
63 using size_type = unsigned;
64
65 // Encapsulation of a single bit.
66 class reference {
67 SmallBitVector &TheVector;
68 unsigned BitPos;
69
70 public:
71 reference(SmallBitVector &b, unsigned Idx) : TheVector(b), BitPos(Idx) {}
72
73 reference(const reference&) = default;
74
75 reference& operator=(reference t) {
76 *this = bool(t);
77 return *this;
78 }
79
80 reference& operator=(bool t) {
81 if (t)
82 TheVector.set(BitPos);
83 else
84 TheVector.reset(BitPos);
85 return *this;
86 }
87
88 operator bool() const {
89 return const_cast<const SmallBitVector &>(TheVector).operator[](BitPos);
90 }
91 };
92
93private:
94 BitVector *getPointer() const {
95 assert(!isSmall());
96 return reinterpret_cast<BitVector *>(X);
97 }
98
99 void switchToSmall(uintptr_t NewSmallBits, size_t NewSize) {
100 X = 1;
101 setSmallSize(NewSize);
102 setSmallBits(NewSmallBits);
103 }
104
105 void switchToLarge(BitVector *BV) {
106 X = reinterpret_cast<uintptr_t>(BV);
107 assert(!isSmall() && "Tried to use an unaligned pointer");
108 }
109
110 // Return all the bits used for the "small" representation; this includes
111 // bits for the size as well as the element bits.
112 uintptr_t getSmallRawBits() const {
113 assert(isSmall());
114 return X >> 1;
115 }
116
117 void setSmallRawBits(uintptr_t NewRawBits) {
118 assert(isSmall());
119 X = (NewRawBits << 1) | uintptr_t(1);
120 }
121
122 // Return the size.
123 size_t getSmallSize() const { return getSmallRawBits() >> SmallNumDataBits; }
124
125 void setSmallSize(size_t Size) {
126 setSmallRawBits(getSmallBits() | (Size << SmallNumDataBits));
127 }
128
129 // Return the element bits.
130 uintptr_t getSmallBits() const {
131 return getSmallRawBits() & ~(~uintptr_t(0) << getSmallSize());
132 }
133
134 void setSmallBits(uintptr_t NewBits) {
135 setSmallRawBits((NewBits & ~(~uintptr_t(0) << getSmallSize())) |
136 (getSmallSize() << SmallNumDataBits));
137 }
138
139public:
140 /// Creates an empty bitvector.
141 SmallBitVector() = default;
142
143 /// Creates a bitvector of specified number of bits. All bits are initialized
144 /// to the specified value.
145 explicit SmallBitVector(unsigned s, bool t = false) {
146 if (s <= SmallNumDataBits)
147 switchToSmall(t ? ~uintptr_t(0) : 0, s);
148 else
149 switchToLarge(new BitVector(s, t));
150 }
151
152 /// SmallBitVector copy ctor.
153 SmallBitVector(const SmallBitVector &RHS) {
154 if (RHS.isSmall())
155 X = RHS.X;
156 else
157 switchToLarge(new BitVector(*RHS.getPointer()));
158 }
159
160 SmallBitVector(SmallBitVector &&RHS) : X(RHS.X) {
161 RHS.X = 1;
162 }
163
164 ~SmallBitVector() {
165 if (!isSmall())
166 delete getPointer();
167 }
168
169 using const_set_bits_iterator = const_set_bits_iterator_impl<SmallBitVector>;
170 using set_iterator = const_set_bits_iterator;
171
172 const_set_bits_iterator set_bits_begin() const {
173 return const_set_bits_iterator(*this);
174 }
175
176 const_set_bits_iterator set_bits_end() const {
177 return const_set_bits_iterator(*this, -1);
178 }
179
180 iterator_range<const_set_bits_iterator> set_bits() const {
181 return make_range(set_bits_begin(), set_bits_end());
182 }
183
184 bool isSmall() const { return X & uintptr_t(1); }
185
186 /// Tests whether there are no bits in this bitvector.
187 bool empty() const {
188 return isSmall() ? getSmallSize() == 0 : getPointer()->empty();
189 }
190
191 /// Returns the number of bits in this bitvector.
192 size_t size() const {
193 return isSmall() ? getSmallSize() : getPointer()->size();
194 }
195
196 /// Returns the number of bits which are set.
197 size_type count() const {
198 if (isSmall()) {
199 uintptr_t Bits = getSmallBits();
200 return countPopulation(Bits);
201 }
202 return getPointer()->count();
203 }
204
205 /// Returns true if any bit is set.
206 bool any() const {
207 if (isSmall())
208 return getSmallBits() != 0;
209 return getPointer()->any();
210 }
211
212 /// Returns true if all bits are set.
213 bool all() const {
214 if (isSmall())
215 return getSmallBits() == (uintptr_t(1) << getSmallSize()) - 1;
216 return getPointer()->all();
217 }
218
219 /// Returns true if none of the bits are set.
220 bool none() const {
221 if (isSmall())
222 return getSmallBits() == 0;
223 return getPointer()->none();
224 }
225
226 /// Returns the index of the first set bit, -1 if none of the bits are set.
227 int find_first() const {
228 if (isSmall()) {
229 uintptr_t Bits = getSmallBits();
230 if (Bits == 0)
231 return -1;
232 return countTrailingZeros(Bits);
233 }
234 return getPointer()->find_first();
235 }
236
237 int find_last() const {
238 if (isSmall()) {
239 uintptr_t Bits = getSmallBits();
240 if (Bits == 0)
241 return -1;
242 return NumBaseBits - countLeadingZeros(Bits) - 1;
243 }
244 return getPointer()->find_last();
245 }
246
247 /// Returns the index of the first unset bit, -1 if all of the bits are set.
248 int find_first_unset() const {
249 if (isSmall()) {
250 if (count() == getSmallSize())
251 return -1;
252
253 uintptr_t Bits = getSmallBits();
254 return countTrailingOnes(Bits);
255 }
256 return getPointer()->find_first_unset();
257 }
258
259 int find_last_unset() const {
260 if (isSmall()) {
261 if (count() == getSmallSize())
262 return -1;
263
264 uintptr_t Bits = getSmallBits();
265 // Set unused bits.
266 Bits |= ~uintptr_t(0) << getSmallSize();
267 return NumBaseBits - countLeadingOnes(Bits) - 1;
268 }
269 return getPointer()->find_last_unset();
270 }
271
272 /// Returns the index of the next set bit following the "Prev" bit.
273 /// Returns -1 if the next set bit is not found.
274 int find_next(unsigned Prev) const {
275 if (isSmall()) {
276 uintptr_t Bits = getSmallBits();
277 // Mask off previous bits.
278 Bits &= ~uintptr_t(0) << (Prev + 1);
279 if (Bits == 0 || Prev + 1 >= getSmallSize())
280 return -1;
281 return countTrailingZeros(Bits);
282 }
283 return getPointer()->find_next(Prev);
284 }
285
286 /// Returns the index of the next unset bit following the "Prev" bit.
287 /// Returns -1 if the next unset bit is not found.
288 int find_next_unset(unsigned Prev) const {
289 if (isSmall()) {
290 ++Prev;
291 uintptr_t Bits = getSmallBits();
292 // Mask in previous bits.
293 uintptr_t Mask = (1 << Prev) - 1;
294 Bits |= Mask;
295
296 if (Bits == ~uintptr_t(0) || Prev + 1 >= getSmallSize())
297 return -1;
298 return countTrailingOnes(Bits);
299 }
300 return getPointer()->find_next_unset(Prev);
301 }
302
303 /// find_prev - Returns the index of the first set bit that precedes the
304 /// the bit at \p PriorTo. Returns -1 if all previous bits are unset.
305 int find_prev(unsigned PriorTo) const {
306 if (isSmall()) {
307 if (PriorTo == 0)
308 return -1;
309
310 --PriorTo;
311 uintptr_t Bits = getSmallBits();
312 Bits &= maskTrailingOnes<uintptr_t>(PriorTo + 1);
313 if (Bits == 0)
314 return -1;
315
316 return NumBaseBits - countLeadingZeros(Bits) - 1;
317 }
318 return getPointer()->find_prev(PriorTo);
319 }
320
321 /// Clear all bits.
322 void clear() {
323 if (!isSmall())
324 delete getPointer();
325 switchToSmall(0, 0);
326 }
327
328 /// Grow or shrink the bitvector.
329 void resize(unsigned N, bool t = false) {
330 if (!isSmall()) {
331 getPointer()->resize(N, t);
332 } else if (SmallNumDataBits >= N) {
333 uintptr_t NewBits = t ? ~uintptr_t(0) << getSmallSize() : 0;
334 setSmallSize(N);
335 setSmallBits(NewBits | getSmallBits());
336 } else {
337 BitVector *BV = new BitVector(N, t);
338 uintptr_t OldBits = getSmallBits();
339 for (size_t i = 0, e = getSmallSize(); i != e; ++i)
340 (*BV)[i] = (OldBits >> i) & 1;
341 switchToLarge(BV);
342 }
343 }
344
345 void reserve(unsigned N) {
346 if (isSmall()) {
347 if (N > SmallNumDataBits) {
348 uintptr_t OldBits = getSmallRawBits();
349 size_t SmallSize = getSmallSize();
350 BitVector *BV = new BitVector(SmallSize);
351 for (size_t i = 0; i < SmallSize; ++i)
352 if ((OldBits >> i) & 1)
353 BV->set(i);
354 BV->reserve(N);
355 switchToLarge(BV);
356 }
357 } else {
358 getPointer()->reserve(N);
359 }
360 }
361
362 // Set, reset, flip
363 SmallBitVector &set() {
364 if (isSmall())
365 setSmallBits(~uintptr_t(0));
366 else
367 getPointer()->set();
368 return *this;
369 }
370
371 SmallBitVector &set(unsigned Idx) {
372 if (isSmall()) {
373 assert(Idx <= static_cast<unsigned>(
374 std::numeric_limits<uintptr_t>::digits) &&
375 "undefined behavior");
376 setSmallBits(getSmallBits() | (uintptr_t(1) << Idx));
377 }
378 else
379 getPointer()->set(Idx);
380 return *this;
381 }
382
383 /// Efficiently set a range of bits in [I, E)
384 SmallBitVector &set(unsigned I, unsigned E) {
385 assert(I <= E && "Attempted to set backwards range!");
386 assert(E <= size() && "Attempted to set out-of-bounds range!");
387 if (I == E) return *this;
388 if (isSmall()) {
389 uintptr_t EMask = ((uintptr_t)1) << E;
390 uintptr_t IMask = ((uintptr_t)1) << I;
391 uintptr_t Mask = EMask - IMask;
392 setSmallBits(getSmallBits() | Mask);
393 } else
394 getPointer()->set(I, E);
395 return *this;
396 }
397
398 SmallBitVector &reset() {
399 if (isSmall())
400 setSmallBits(0);
401 else
402 getPointer()->reset();
403 return *this;
404 }
405
406 SmallBitVector &reset(unsigned Idx) {
407 if (isSmall())
408 setSmallBits(getSmallBits() & ~(uintptr_t(1) << Idx));
409 else
410 getPointer()->reset(Idx);
411 return *this;
412 }
413
414 /// Efficiently reset a range of bits in [I, E)
415 SmallBitVector &reset(unsigned I, unsigned E) {
416 assert(I <= E && "Attempted to reset backwards range!");
417 assert(E <= size() && "Attempted to reset out-of-bounds range!");
418 if (I == E) return *this;
419 if (isSmall()) {
420 uintptr_t EMask = ((uintptr_t)1) << E;
421 uintptr_t IMask = ((uintptr_t)1) << I;
422 uintptr_t Mask = EMask - IMask;
423 setSmallBits(getSmallBits() & ~Mask);
424 } else
425 getPointer()->reset(I, E);
426 return *this;
427 }
428
429 SmallBitVector &flip() {
430 if (isSmall())
431 setSmallBits(~getSmallBits());
432 else
433 getPointer()->flip();
434 return *this;
435 }
436
437 SmallBitVector &flip(unsigned Idx) {
438 if (isSmall())
439 setSmallBits(getSmallBits() ^ (uintptr_t(1) << Idx));
440 else
441 getPointer()->flip(Idx);
442 return *this;
443 }
444
445 // No argument flip.
446 SmallBitVector operator~() const {
447 return SmallBitVector(*this).flip();
448 }
449
450 // Indexing.
451 reference operator[](unsigned Idx) {
452 assert(Idx < size() && "Out-of-bounds Bit access.");
453 return reference(*this, Idx);
454 }
455
456 bool operator[](unsigned Idx) const {
457 assert(Idx < size() && "Out-of-bounds Bit access.");
458 if (isSmall())
459 return ((getSmallBits() >> Idx) & 1) != 0;
460 return getPointer()->operator[](Idx);
461 }
462
463 bool test(unsigned Idx) const {
464 return (*this)[Idx];
465 }
466
467 // Push single bit to end of vector.
468 void push_back(bool Val) {
469 resize(size() + 1, Val);
470 }
471
472 /// Test if any common bits are set.
473 bool anyCommon(const SmallBitVector &RHS) const {
474 if (isSmall() && RHS.isSmall())
475 return (getSmallBits() & RHS.getSmallBits()) != 0;
476 if (!isSmall() && !RHS.isSmall())
477 return getPointer()->anyCommon(*RHS.getPointer());
478
479 for (unsigned i = 0, e = std::min(size(), RHS.size()); i != e; ++i)
480 if (test(i) && RHS.test(i))
481 return true;
482 return false;
483 }
484
485 // Comparison operators.
486 bool operator==(const SmallBitVector &RHS) const {
487 if (size() != RHS.size())
488 return false;
489 if (isSmall() && RHS.isSmall())
490 return getSmallBits() == RHS.getSmallBits();
491 else if (!isSmall() && !RHS.isSmall())
492 return *getPointer() == *RHS.getPointer();
493 else {
494 for (size_t i = 0, e = size(); i != e; ++i) {
495 if ((*this)[i] != RHS[i])
496 return false;
497 }
498 return true;
499 }
500 }
501
502 bool operator!=(const SmallBitVector &RHS) const {
503 return !(*this == RHS);
504 }
505
506 // Intersection, union, disjoint union.
507 // FIXME BitVector::operator&= does not resize the LHS but this does
508 SmallBitVector &operator&=(const SmallBitVector &RHS) {
509 resize(std::max(size(), RHS.size()));
510 if (isSmall() && RHS.isSmall())
511 setSmallBits(getSmallBits() & RHS.getSmallBits());
512 else if (!isSmall() && !RHS.isSmall())
513 getPointer()->operator&=(*RHS.getPointer());
514 else {
515 size_t i, e;
516 for (i = 0, e = std::min(size(), RHS.size()); i != e; ++i)
517 (*this)[i] = test(i) && RHS.test(i);
518 for (e = size(); i != e; ++i)
519 reset(i);
520 }
521 return *this;
522 }
523
524 /// Reset bits that are set in RHS. Same as *this &= ~RHS.
525 SmallBitVector &reset(const SmallBitVector &RHS) {
526 if (isSmall() && RHS.isSmall())
527 setSmallBits(getSmallBits() & ~RHS.getSmallBits());
528 else if (!isSmall() && !RHS.isSmall())
529 getPointer()->reset(*RHS.getPointer());
530 else
531 for (unsigned i = 0, e = std::min(size(), RHS.size()); i != e; ++i)
532 if (RHS.test(i))
533 reset(i);
534
535 return *this;
536 }
537
538 /// Check if (This - RHS) is zero. This is the same as reset(RHS) and any().
539 bool test(const SmallBitVector &RHS) const {
540 if (isSmall() && RHS.isSmall())
541 return (getSmallBits() & ~RHS.getSmallBits()) != 0;
542 if (!isSmall() && !RHS.isSmall())
543 return getPointer()->test(*RHS.getPointer());
544
545 unsigned i, e;
546 for (i = 0, e = std::min(size(), RHS.size()); i != e; ++i)
547 if (test(i) && !RHS.test(i))
548 return true;
549
550 for (e = size(); i != e; ++i)
551 if (test(i))
552 return true;
553
554 return false;
555 }
556
557 SmallBitVector &operator|=(const SmallBitVector &RHS) {
558 resize(std::max(size(), RHS.size()));
559 if (isSmall() && RHS.isSmall())
560 setSmallBits(getSmallBits() | RHS.getSmallBits());
561 else if (!isSmall() && !RHS.isSmall())
562 getPointer()->operator|=(*RHS.getPointer());
563 else {
564 for (size_t i = 0, e = RHS.size(); i != e; ++i)
565 (*this)[i] = test(i) || RHS.test(i);
566 }
567 return *this;
568 }
569
570 SmallBitVector &operator^=(const SmallBitVector &RHS) {
571 resize(std::max(size(), RHS.size()));
572 if (isSmall() && RHS.isSmall())
573 setSmallBits(getSmallBits() ^ RHS.getSmallBits());
574 else if (!isSmall() && !RHS.isSmall())
575 getPointer()->operator^=(*RHS.getPointer());
576 else {
577 for (size_t i = 0, e = RHS.size(); i != e; ++i)
578 (*this)[i] = test(i) != RHS.test(i);
579 }
580 return *this;
581 }
582
583 SmallBitVector &operator<<=(unsigned N) {
584 if (isSmall())
585 setSmallBits(getSmallBits() << N);
586 else
587 getPointer()->operator<<=(N);
588 return *this;
589 }
590
591 SmallBitVector &operator>>=(unsigned N) {
592 if (isSmall())
593 setSmallBits(getSmallBits() >> N);
594 else
595 getPointer()->operator>>=(N);
596 return *this;
597 }
598
599 // Assignment operator.
600 const SmallBitVector &operator=(const SmallBitVector &RHS) {
601 if (isSmall()) {
602 if (RHS.isSmall())
603 X = RHS.X;
604 else
605 switchToLarge(new BitVector(*RHS.getPointer()));
606 } else {
607 if (!RHS.isSmall())
608 *getPointer() = *RHS.getPointer();
609 else {
610 delete getPointer();
611 X = RHS.X;
612 }
613 }
614 return *this;
615 }
616
617 const SmallBitVector &operator=(SmallBitVector &&RHS) {
618 if (this != &RHS) {
619 clear();
620 swap(RHS);
621 }
622 return *this;
623 }
624
625 void swap(SmallBitVector &RHS) {
626 std::swap(X, RHS.X);
627 }
628
629 /// Add '1' bits from Mask to this vector. Don't resize.
630 /// This computes "*this |= Mask".
631 void setBitsInMask(const uint32_t *Mask, unsigned MaskWords = ~0u) {
632 if (isSmall())
633 applyMask<true, false>(Mask, MaskWords);
634 else
635 getPointer()->setBitsInMask(Mask, MaskWords);
636 }
637
638 /// Clear any bits in this vector that are set in Mask. Don't resize.
639 /// This computes "*this &= ~Mask".
640 void clearBitsInMask(const uint32_t *Mask, unsigned MaskWords = ~0u) {
641 if (isSmall())
642 applyMask<false, false>(Mask, MaskWords);
643 else
644 getPointer()->clearBitsInMask(Mask, MaskWords);
645 }
646
647 /// Add a bit to this vector for every '0' bit in Mask. Don't resize.
648 /// This computes "*this |= ~Mask".
649 void setBitsNotInMask(const uint32_t *Mask, unsigned MaskWords = ~0u) {
650 if (isSmall())
651 applyMask<true, true>(Mask, MaskWords);
652 else
653 getPointer()->setBitsNotInMask(Mask, MaskWords);
654 }
655
656 /// Clear a bit in this vector for every '0' bit in Mask. Don't resize.
657 /// This computes "*this &= Mask".
658 void clearBitsNotInMask(const uint32_t *Mask, unsigned MaskWords = ~0u) {
659 if (isSmall())
660 applyMask<false, true>(Mask, MaskWords);
661 else
662 getPointer()->clearBitsNotInMask(Mask, MaskWords);
663 }
664
665private:
666 template <bool AddBits, bool InvertMask>
667 void applyMask(const uint32_t *Mask, unsigned MaskWords) {
668 assert(MaskWords <= sizeof(uintptr_t) && "Mask is larger than base!");
669 uintptr_t M = Mask[0];
670 if (NumBaseBits == 64)
671 M |= uint64_t(Mask[1]) << 32;
672 if (InvertMask)
673 M = ~M;
674 if (AddBits)
675 setSmallBits(getSmallBits() | M);
676 else
677 setSmallBits(getSmallBits() & ~M);
678 }
679};
680
681inline SmallBitVector
682operator&(const SmallBitVector &LHS, const SmallBitVector &RHS) {
683 SmallBitVector Result(LHS);
684 Result &= RHS;
685 return Result;
686}
687
688inline SmallBitVector
689operator|(const SmallBitVector &LHS, const SmallBitVector &RHS) {
690 SmallBitVector Result(LHS);
691 Result |= RHS;
692 return Result;
693}
694
695inline SmallBitVector
696operator^(const SmallBitVector &LHS, const SmallBitVector &RHS) {
697 SmallBitVector Result(LHS);
698 Result ^= RHS;
699 return Result;
700}
701
702} // end namespace llvm
703
704namespace std {
705
706/// Implement std::swap in terms of BitVector swap.
707inline void
708swap(llvm::SmallBitVector &LHS, llvm::SmallBitVector &RHS) {
709 LHS.swap(RHS);
710}
711
712} // end namespace std
713
714#endif // LLVM_ADT_SMALLBITVECTOR_H
715