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