1 //===- llvm/ADT/SparseBitVector.h - Efficient Sparse BitVector -*- 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 defines the SparseBitVector class. See the doxygen comment for
11 // SparseBitVector for more details on the algorithm used.
13 //===----------------------------------------------------------------------===//
15 #ifndef LLVM_ADT_SPARSEBITVECTOR_H
16 #define LLVM_ADT_SPARSEBITVECTOR_H
21 #include "llvm/Support/DataTypes.h"
22 #include "llvm/ADT/STLExtras.h"
23 #include "llvm/Support/MathExtras.h"
24 #include "llvm/ADT/ilist.h"
27 /// SparseBitVector is an implementation of a bitvector that is sparse by only
28 /// storing the elements that have non-zero bits set. In order to make this
29 /// fast for the most common cases, SparseBitVector is implemented as a linked
30 /// list of SparseBitVectorElements. We maintain a pointer to the last
31 /// SparseBitVectorElement accessed (in the form of a list iterator), in order
32 /// to make multiple in-order test/set constant time after the first one is
33 /// executed. Note that using vectors to store SparseBitVectorElement's does
34 /// not work out very well because it causes insertion in the middle to take
35 /// enormous amounts of time with a large amount of bits. Other structures that
36 /// have better worst cases for insertion in the middle (various balanced trees,
37 /// etc) do not perform as well in practice as a linked list with this iterator
38 /// kept up to date. They are also significantly more memory intensive.
41 template <unsigned ElementSize = 128>
42 struct SparseBitVectorElement
43 : ilist_node<SparseBitVectorElement<ElementSize> > {
45 typedef unsigned long BitWord;
47 BITWORD_SIZE = sizeof(BitWord) * 8,
48 BITWORDS_PER_ELEMENT = (ElementSize + BITWORD_SIZE - 1) / BITWORD_SIZE,
49 BITS_PER_ELEMENT = ElementSize
53 // Index of Element in terms of where first bit starts.
54 unsigned ElementIndex;
55 BitWord Bits[BITWORDS_PER_ELEMENT];
56 // Needed for sentinels
57 friend class ilist_sentinel_traits<SparseBitVectorElement>;
58 SparseBitVectorElement() {
60 memset(&Bits[0], 0, sizeof (BitWord) * BITWORDS_PER_ELEMENT);
64 explicit SparseBitVectorElement(unsigned Idx) {
66 memset(&Bits[0], 0, sizeof (BitWord) * BITWORDS_PER_ELEMENT);
70 bool operator==(const SparseBitVectorElement &RHS) const {
71 if (ElementIndex != RHS.ElementIndex)
73 for (unsigned i = 0; i < BITWORDS_PER_ELEMENT; ++i)
74 if (Bits[i] != RHS.Bits[i])
79 bool operator!=(const SparseBitVectorElement &RHS) const {
80 return !(*this == RHS);
83 // Return the bits that make up word Idx in our element.
84 BitWord word(unsigned Idx) const {
85 assert (Idx < BITWORDS_PER_ELEMENT);
89 unsigned index() const {
94 for (unsigned i = 0; i < BITWORDS_PER_ELEMENT; ++i)
100 void set(unsigned Idx) {
101 Bits[Idx / BITWORD_SIZE] |= 1L << (Idx % BITWORD_SIZE);
104 bool test_and_set (unsigned Idx) {
105 bool old = test(Idx);
113 void reset(unsigned Idx) {
114 Bits[Idx / BITWORD_SIZE] &= ~(1L << (Idx % BITWORD_SIZE));
117 bool test(unsigned Idx) const {
118 return Bits[Idx / BITWORD_SIZE] & (1L << (Idx % BITWORD_SIZE));
121 unsigned count() const {
122 unsigned NumBits = 0;
123 for (unsigned i = 0; i < BITWORDS_PER_ELEMENT; ++i)
124 if (sizeof(BitWord) == 4)
125 NumBits += CountPopulation_32(Bits[i]);
126 else if (sizeof(BitWord) == 8)
127 NumBits += CountPopulation_64(Bits[i]);
129 assert(0 && "Unsupported!");
133 /// find_first - Returns the index of the first set bit.
134 int find_first() const {
135 for (unsigned i = 0; i < BITWORDS_PER_ELEMENT; ++i)
137 if (sizeof(BitWord) == 4)
138 return i * BITWORD_SIZE + CountTrailingZeros_32(Bits[i]);
139 else if (sizeof(BitWord) == 8)
140 return i * BITWORD_SIZE + CountTrailingZeros_64(Bits[i]);
142 assert(0 && "Unsupported!");
144 assert(0 && "Illegal empty element");
145 return 0; // Not reached
148 /// find_next - Returns the index of the next set bit starting from the
149 /// "Curr" bit. Returns -1 if the next set bit is not found.
150 int find_next(unsigned Curr) const {
151 if (Curr >= BITS_PER_ELEMENT)
154 unsigned WordPos = Curr / BITWORD_SIZE;
155 unsigned BitPos = Curr % BITWORD_SIZE;
156 BitWord Copy = Bits[WordPos];
157 assert (WordPos <= BITWORDS_PER_ELEMENT
158 && "Word Position outside of element");
160 // Mask off previous bits.
161 Copy &= ~0L << BitPos;
164 if (sizeof(BitWord) == 4)
165 return WordPos * BITWORD_SIZE + CountTrailingZeros_32(Copy);
166 else if (sizeof(BitWord) == 8)
167 return WordPos * BITWORD_SIZE + CountTrailingZeros_64(Copy);
169 assert(0 && "Unsupported!");
172 // Check subsequent words.
173 for (unsigned i = WordPos+1; i < BITWORDS_PER_ELEMENT; ++i)
175 if (sizeof(BitWord) == 4)
176 return i * BITWORD_SIZE + CountTrailingZeros_32(Bits[i]);
177 else if (sizeof(BitWord) == 8)
178 return i * BITWORD_SIZE + CountTrailingZeros_64(Bits[i]);
180 assert(0 && "Unsupported!");
185 // Union this element with RHS and return true if this one changed.
186 bool unionWith(const SparseBitVectorElement &RHS) {
187 bool changed = false;
188 for (unsigned i = 0; i < BITWORDS_PER_ELEMENT; ++i) {
189 BitWord old = changed ? 0 : Bits[i];
191 Bits[i] |= RHS.Bits[i];
192 if (!changed && old != Bits[i])
198 // Return true if we have any bits in common with RHS
199 bool intersects(const SparseBitVectorElement &RHS) const {
200 for (unsigned i = 0; i < BITWORDS_PER_ELEMENT; ++i) {
201 if (RHS.Bits[i] & Bits[i])
207 // Intersect this Element with RHS and return true if this one changed.
208 // BecameZero is set to true if this element became all-zero bits.
209 bool intersectWith(const SparseBitVectorElement &RHS,
211 bool changed = false;
215 for (unsigned i = 0; i < BITWORDS_PER_ELEMENT; ++i) {
216 BitWord old = changed ? 0 : Bits[i];
218 Bits[i] &= RHS.Bits[i];
222 if (!changed && old != Bits[i])
225 BecameZero = allzero;
228 // Intersect this Element with the complement of RHS and return true if this
229 // one changed. BecameZero is set to true if this element became all-zero
231 bool intersectWithComplement(const SparseBitVectorElement &RHS,
233 bool changed = false;
237 for (unsigned i = 0; i < BITWORDS_PER_ELEMENT; ++i) {
238 BitWord old = changed ? 0 : Bits[i];
240 Bits[i] &= ~RHS.Bits[i];
244 if (!changed && old != Bits[i])
247 BecameZero = allzero;
250 // Three argument version of intersectWithComplement that intersects
251 // RHS1 & ~RHS2 into this element
252 void intersectWithComplement(const SparseBitVectorElement &RHS1,
253 const SparseBitVectorElement &RHS2,
258 for (unsigned i = 0; i < BITWORDS_PER_ELEMENT; ++i) {
259 Bits[i] = RHS1.Bits[i] & ~RHS2.Bits[i];
263 BecameZero = allzero;
266 // Get a hash value for this element;
267 uint64_t getHashValue() const {
268 uint64_t HashVal = 0;
269 for (unsigned i = 0; i < BITWORDS_PER_ELEMENT; ++i) {
276 template <unsigned ElementSize = 128>
277 class SparseBitVector {
278 typedef ilist<SparseBitVectorElement<ElementSize> > ElementList;
279 typedef typename ElementList::iterator ElementListIter;
280 typedef typename ElementList::const_iterator ElementListConstIter;
282 BITWORD_SIZE = SparseBitVectorElement<ElementSize>::BITWORD_SIZE
285 // Pointer to our current Element.
286 ElementListIter CurrElementIter;
287 ElementList Elements;
289 // This is like std::lower_bound, except we do linear searching from the
291 ElementListIter FindLowerBound(unsigned ElementIndex) {
293 if (Elements.empty()) {
294 CurrElementIter = Elements.begin();
295 return Elements.begin();
298 // Make sure our current iterator is valid.
299 if (CurrElementIter == Elements.end())
302 // Search from our current iterator, either backwards or forwards,
303 // depending on what element we are looking for.
304 ElementListIter ElementIter = CurrElementIter;
305 if (CurrElementIter->index() == ElementIndex) {
307 } else if (CurrElementIter->index() > ElementIndex) {
308 while (ElementIter != Elements.begin()
309 && ElementIter->index() > ElementIndex)
312 while (ElementIter != Elements.end() &&
313 ElementIter->index() < ElementIndex)
316 CurrElementIter = ElementIter;
320 // Iterator to walk set bits in the bitmap. This iterator is a lot uglier
321 // than it would be, in order to be efficient.
322 class SparseBitVectorIterator {
326 const SparseBitVector<ElementSize> *BitVector;
328 // Current element inside of bitmap.
329 ElementListConstIter Iter;
331 // Current bit number inside of our bitmap.
334 // Current word number inside of our element.
337 // Current bits from the element.
338 typename SparseBitVectorElement<ElementSize>::BitWord Bits;
340 // Move our iterator to the first non-zero bit in the bitmap.
341 void AdvanceToFirstNonZero() {
344 if (BitVector->Elements.empty()) {
348 Iter = BitVector->Elements.begin();
349 BitNumber = Iter->index() * ElementSize;
350 unsigned BitPos = Iter->find_first();
352 WordNumber = (BitNumber % ElementSize) / BITWORD_SIZE;
353 Bits = Iter->word(WordNumber);
354 Bits >>= BitPos % BITWORD_SIZE;
357 // Move our iterator to the next non-zero bit.
358 void AdvanceToNextNonZero() {
362 while (Bits && !(Bits & 1)) {
367 // See if we ran out of Bits in this word.
369 int NextSetBitNumber = Iter->find_next(BitNumber % ElementSize) ;
370 // If we ran out of set bits in this element, move to next element.
371 if (NextSetBitNumber == -1 || (BitNumber % ElementSize == 0)) {
375 // We may run out of elements in the bitmap.
376 if (Iter == BitVector->Elements.end()) {
380 // Set up for next non zero word in bitmap.
381 BitNumber = Iter->index() * ElementSize;
382 NextSetBitNumber = Iter->find_first();
383 BitNumber += NextSetBitNumber;
384 WordNumber = (BitNumber % ElementSize) / BITWORD_SIZE;
385 Bits = Iter->word(WordNumber);
386 Bits >>= NextSetBitNumber % BITWORD_SIZE;
388 WordNumber = (NextSetBitNumber % ElementSize) / BITWORD_SIZE;
389 Bits = Iter->word(WordNumber);
390 Bits >>= NextSetBitNumber % BITWORD_SIZE;
391 BitNumber = Iter->index() * ElementSize;
392 BitNumber += NextSetBitNumber;
398 inline SparseBitVectorIterator& operator++() {
401 AdvanceToNextNonZero();
406 inline SparseBitVectorIterator operator++(int) {
407 SparseBitVectorIterator tmp = *this;
412 // Return the current set bit number.
413 unsigned operator*() const {
417 bool operator==(const SparseBitVectorIterator &RHS) const {
418 // If they are both at the end, ignore the rest of the fields.
419 if (AtEnd && RHS.AtEnd)
421 // Otherwise they are the same if they have the same bit number and
423 return AtEnd == RHS.AtEnd && RHS.BitNumber == BitNumber;
425 bool operator!=(const SparseBitVectorIterator &RHS) const {
426 return !(*this == RHS);
428 SparseBitVectorIterator(): BitVector(NULL) {
432 SparseBitVectorIterator(const SparseBitVector<ElementSize> *RHS,
433 bool end = false):BitVector(RHS) {
434 Iter = BitVector->Elements.begin();
439 AdvanceToFirstNonZero();
443 typedef SparseBitVectorIterator iterator;
446 CurrElementIter = Elements.begin ();
452 // SparseBitVector copy ctor.
453 SparseBitVector(const SparseBitVector &RHS) {
454 ElementListConstIter ElementIter = RHS.Elements.begin();
455 while (ElementIter != RHS.Elements.end()) {
456 Elements.push_back(SparseBitVectorElement<ElementSize>(*ElementIter));
460 CurrElementIter = Elements.begin ();
464 SparseBitVector& operator=(const SparseBitVector& RHS) {
467 ElementListConstIter ElementIter = RHS.Elements.begin();
468 while (ElementIter != RHS.Elements.end()) {
469 Elements.push_back(SparseBitVectorElement<ElementSize>(*ElementIter));
473 CurrElementIter = Elements.begin ();
478 // Test, Reset, and Set a bit in the bitmap.
479 bool test(unsigned Idx) {
480 if (Elements.empty())
483 unsigned ElementIndex = Idx / ElementSize;
484 ElementListIter ElementIter = FindLowerBound(ElementIndex);
486 // If we can't find an element that is supposed to contain this bit, there
487 // is nothing more to do.
488 if (ElementIter == Elements.end() ||
489 ElementIter->index() != ElementIndex)
491 return ElementIter->test(Idx % ElementSize);
494 void reset(unsigned Idx) {
495 if (Elements.empty())
498 unsigned ElementIndex = Idx / ElementSize;
499 ElementListIter ElementIter = FindLowerBound(ElementIndex);
501 // If we can't find an element that is supposed to contain this bit, there
502 // is nothing more to do.
503 if (ElementIter == Elements.end() ||
504 ElementIter->index() != ElementIndex)
506 ElementIter->reset(Idx % ElementSize);
508 // When the element is zeroed out, delete it.
509 if (ElementIter->empty()) {
511 Elements.erase(ElementIter);
515 void set(unsigned Idx) {
516 unsigned ElementIndex = Idx / ElementSize;
517 SparseBitVectorElement<ElementSize> *Element;
518 ElementListIter ElementIter;
519 if (Elements.empty()) {
520 Element = new SparseBitVectorElement<ElementSize>(ElementIndex);
521 ElementIter = Elements.insert(Elements.end(), Element);
524 ElementIter = FindLowerBound(ElementIndex);
526 if (ElementIter == Elements.end() ||
527 ElementIter->index() != ElementIndex) {
528 Element = new SparseBitVectorElement<ElementSize>(ElementIndex);
529 // We may have hit the beginning of our SparseBitVector, in which case,
530 // we may need to insert right after this element, which requires moving
531 // the current iterator forward one, because insert does insert before.
532 if (ElementIter != Elements.end() &&
533 ElementIter->index() < ElementIndex)
534 ElementIter = Elements.insert(++ElementIter, Element);
536 ElementIter = Elements.insert(ElementIter, Element);
539 CurrElementIter = ElementIter;
541 ElementIter->set(Idx % ElementSize);
544 bool test_and_set (unsigned Idx) {
545 bool old = test(Idx);
553 bool operator!=(const SparseBitVector &RHS) const {
554 return !(*this == RHS);
557 bool operator==(const SparseBitVector &RHS) const {
558 ElementListConstIter Iter1 = Elements.begin();
559 ElementListConstIter Iter2 = RHS.Elements.begin();
561 for (; Iter1 != Elements.end() && Iter2 != RHS.Elements.end();
563 if (*Iter1 != *Iter2)
566 return Iter1 == Elements.end() && Iter2 == RHS.Elements.end();
569 // Union our bitmap with the RHS and return true if we changed.
570 bool operator|=(const SparseBitVector &RHS) {
571 bool changed = false;
572 ElementListIter Iter1 = Elements.begin();
573 ElementListConstIter Iter2 = RHS.Elements.begin();
575 // If RHS is empty, we are done
576 if (RHS.Elements.empty())
579 while (Iter2 != RHS.Elements.end()) {
580 if (Iter1 == Elements.end() || Iter1->index() > Iter2->index()) {
581 Elements.insert(Iter1,
582 new SparseBitVectorElement<ElementSize>(*Iter2));
585 } else if (Iter1->index() == Iter2->index()) {
586 changed |= Iter1->unionWith(*Iter2);
593 CurrElementIter = Elements.begin();
597 // Intersect our bitmap with the RHS and return true if ours changed.
598 bool operator&=(const SparseBitVector &RHS) {
599 bool changed = false;
600 ElementListIter Iter1 = Elements.begin();
601 ElementListConstIter Iter2 = RHS.Elements.begin();
603 // Check if both bitmaps are empty.
604 if (Elements.empty() && RHS.Elements.empty())
607 // Loop through, intersecting as we go, erasing elements when necessary.
608 while (Iter2 != RHS.Elements.end()) {
609 if (Iter1 == Elements.end()) {
610 CurrElementIter = Elements.begin();
614 if (Iter1->index() > Iter2->index()) {
616 } else if (Iter1->index() == Iter2->index()) {
618 changed |= Iter1->intersectWith(*Iter2, BecameZero);
620 ElementListIter IterTmp = Iter1;
622 Elements.erase(IterTmp);
628 ElementListIter IterTmp = Iter1;
630 Elements.erase(IterTmp);
633 Elements.erase(Iter1, Elements.end());
634 CurrElementIter = Elements.begin();
638 // Intersect our bitmap with the complement of the RHS and return true if ours
640 bool intersectWithComplement(const SparseBitVector &RHS) {
641 bool changed = false;
642 ElementListIter Iter1 = Elements.begin();
643 ElementListConstIter Iter2 = RHS.Elements.begin();
645 // If either our bitmap or RHS is empty, we are done
646 if (Elements.empty() || RHS.Elements.empty())
649 // Loop through, intersecting as we go, erasing elements when necessary.
650 while (Iter2 != RHS.Elements.end()) {
651 if (Iter1 == Elements.end()) {
652 CurrElementIter = Elements.begin();
656 if (Iter1->index() > Iter2->index()) {
658 } else if (Iter1->index() == Iter2->index()) {
660 changed |= Iter1->intersectWithComplement(*Iter2, BecameZero);
662 ElementListIter IterTmp = Iter1;
664 Elements.erase(IterTmp);
673 CurrElementIter = Elements.begin();
677 bool intersectWithComplement(const SparseBitVector<ElementSize> *RHS) const {
678 return intersectWithComplement(*RHS);
682 // Three argument version of intersectWithComplement. Result of RHS1 & ~RHS2
683 // is stored into this bitmap.
684 void intersectWithComplement(const SparseBitVector<ElementSize> &RHS1,
685 const SparseBitVector<ElementSize> &RHS2)
688 CurrElementIter = Elements.begin();
689 ElementListConstIter Iter1 = RHS1.Elements.begin();
690 ElementListConstIter Iter2 = RHS2.Elements.begin();
692 // If RHS1 is empty, we are done
693 // If RHS2 is empty, we still have to copy RHS1
694 if (RHS1.Elements.empty())
697 // Loop through, intersecting as we go, erasing elements when necessary.
698 while (Iter2 != RHS2.Elements.end()) {
699 if (Iter1 == RHS1.Elements.end())
702 if (Iter1->index() > Iter2->index()) {
704 } else if (Iter1->index() == Iter2->index()) {
705 bool BecameZero = false;
706 SparseBitVectorElement<ElementSize> *NewElement =
707 new SparseBitVectorElement<ElementSize>(Iter1->index());
708 NewElement->intersectWithComplement(*Iter1, *Iter2, BecameZero);
710 Elements.push_back(NewElement);
717 SparseBitVectorElement<ElementSize> *NewElement =
718 new SparseBitVectorElement<ElementSize>(*Iter1);
719 Elements.push_back(NewElement);
724 // copy the remaining elements
725 while (Iter1 != RHS1.Elements.end()) {
726 SparseBitVectorElement<ElementSize> *NewElement =
727 new SparseBitVectorElement<ElementSize>(*Iter1);
728 Elements.push_back(NewElement);
735 void intersectWithComplement(const SparseBitVector<ElementSize> *RHS1,
736 const SparseBitVector<ElementSize> *RHS2) {
737 intersectWithComplement(*RHS1, *RHS2);
740 bool intersects(const SparseBitVector<ElementSize> *RHS) const {
741 return intersects(*RHS);
744 // Return true if we share any bits in common with RHS
745 bool intersects(const SparseBitVector<ElementSize> &RHS) const {
746 ElementListConstIter Iter1 = Elements.begin();
747 ElementListConstIter Iter2 = RHS.Elements.begin();
749 // Check if both bitmaps are empty.
750 if (Elements.empty() && RHS.Elements.empty())
753 // Loop through, intersecting stopping when we hit bits in common.
754 while (Iter2 != RHS.Elements.end()) {
755 if (Iter1 == Elements.end())
758 if (Iter1->index() > Iter2->index()) {
760 } else if (Iter1->index() == Iter2->index()) {
761 if (Iter1->intersects(*Iter2))
772 // Return the first set bit in the bitmap. Return -1 if no bits are set.
773 int find_first() const {
774 if (Elements.empty())
776 const SparseBitVectorElement<ElementSize> &First = *(Elements.begin());
777 return (First.index() * ElementSize) + First.find_first();
780 // Return true if the SparseBitVector is empty
782 return Elements.empty();
785 unsigned count() const {
786 unsigned BitCount = 0;
787 for (ElementListConstIter Iter = Elements.begin();
788 Iter != Elements.end();
790 BitCount += Iter->count();
794 iterator begin() const {
795 return iterator(this);
798 iterator end() const {
799 return iterator(this, true);
802 // Get a hash value for this bitmap.
803 uint64_t getHashValue() const {
804 uint64_t HashVal = 0;
805 for (ElementListConstIter Iter = Elements.begin();
806 Iter != Elements.end();
808 HashVal ^= Iter->index();
809 HashVal ^= Iter->getHashValue();
815 // Convenience functions to allow Or and And without dereferencing in the user
818 template <unsigned ElementSize>
819 inline bool operator |=(SparseBitVector<ElementSize> &LHS,
820 const SparseBitVector<ElementSize> *RHS) {
824 template <unsigned ElementSize>
825 inline bool operator |=(SparseBitVector<ElementSize> *LHS,
826 const SparseBitVector<ElementSize> &RHS) {
827 return LHS->operator|=(RHS);
830 template <unsigned ElementSize>
831 inline bool operator &=(SparseBitVector<ElementSize> *LHS,
832 const SparseBitVector<ElementSize> &RHS) {
833 return LHS->operator&=(RHS);
836 template <unsigned ElementSize>
837 inline bool operator &=(SparseBitVector<ElementSize> &LHS,
838 const SparseBitVector<ElementSize> *RHS) {
839 return LHS &= (*RHS);
843 // Dump a SparseBitVector to a stream
844 template <unsigned ElementSize>
845 void dump(const SparseBitVector<ElementSize> &LHS, llvm::OStream &out) {
848 typename SparseBitVector<ElementSize>::iterator bi;
849 for (bi = LHS.begin(); bi != LHS.end(); ++bi) {