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/Compiler.h"
19#include "llvm/Support/MathExtras.h"
20#include <cassert>
21
22namespace llvm {
23
24/// SmallBitVector - This is a 'bitvector' (really, a variable-sized bit array),
25/// optimized for the case when the array is small.  It contains one
26/// pointer-sized field, which is directly used as a plain collection of bits
27/// when possible, or as a pointer to a larger heap-allocated array when
28/// necessary.  This allows normal "small" cases to be fast without losing
29/// generality for large inputs.
30///
31class SmallBitVector {
32  // TODO: In "large" mode, a pointer to a BitVector is used, leading to an
33  // unnecessary level of indirection. It would be more efficient to use a
34  // pointer to memory containing size, allocation size, and the array of bits.
35  uintptr_t X;
36
37  enum {
38    // The number of bits in this class.
39    NumBaseBits = sizeof(uintptr_t) * CHAR_BIT,
40
41    // One bit is used to discriminate between small and large mode. The
42    // remaining bits are used for the small-mode representation.
43    SmallNumRawBits = NumBaseBits - 1,
44
45    // A few more bits are used to store the size of the bit set in small mode.
46    // Theoretically this is a ceil-log2. These bits are encoded in the most
47    // significant bits of the raw bits.
48    SmallNumSizeBits = (NumBaseBits == 32 ? 5 :
49                        NumBaseBits == 64 ? 6 :
50                        SmallNumRawBits),
51
52    // The remaining bits are used to store the actual set in small mode.
53    SmallNumDataBits = SmallNumRawBits - SmallNumSizeBits
54  };
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& operator=(reference t) {
67      *this = bool(t);
68      return *this;
69    }
70
71    reference& operator=(bool t) {
72      if (t)
73        TheVector.set(BitPos);
74      else
75        TheVector.reset(BitPos);
76      return *this;
77    }
78
79    operator bool() const {
80      return const_cast<const SmallBitVector &>(TheVector).operator[](BitPos);
81    }
82  };
83
84private:
85  bool isSmall() const {
86    return X & uintptr_t(1);
87  }
88
89  BitVector *getPointer() const {
90    assert(!isSmall());
91    return reinterpret_cast<BitVector *>(X);
92  }
93
94  void switchToSmall(uintptr_t NewSmallBits, size_t NewSize) {
95    X = 1;
96    setSmallSize(NewSize);
97    setSmallBits(NewSmallBits);
98  }
99
100  void switchToLarge(BitVector *BV) {
101    X = reinterpret_cast<uintptr_t>(BV);
102    assert(!isSmall() && "Tried to use an unaligned pointer");
103  }
104
105  // Return all the bits used for the "small" representation; this includes
106  // bits for the size as well as the element bits.
107  uintptr_t getSmallRawBits() const {
108    assert(isSmall());
109    return X >> 1;
110  }
111
112  void setSmallRawBits(uintptr_t NewRawBits) {
113    assert(isSmall());
114    X = (NewRawBits << 1) | uintptr_t(1);
115  }
116
117  // Return the size.
118  size_t getSmallSize() const {
119    return getSmallRawBits() >> SmallNumDataBits;
120  }
121
122  void setSmallSize(size_t Size) {
123    setSmallRawBits(getSmallBits() | (Size << SmallNumDataBits));
124  }
125
126  // Return the element bits.
127  uintptr_t getSmallBits() const {
128    return getSmallRawBits() & ~(~uintptr_t(0) << getSmallSize());
129  }
130
131  void setSmallBits(uintptr_t NewBits) {
132    setSmallRawBits((NewBits & ~(~uintptr_t(0) << getSmallSize())) |
133                    (getSmallSize() << SmallNumDataBits));
134  }
135
136public:
137  /// SmallBitVector default ctor - Creates an empty bitvector.
138  SmallBitVector() : X(1) {}
139
140  /// SmallBitVector ctor - Creates a bitvector of specified number of bits. All
141  /// bits are initialized to the specified value.
142  explicit SmallBitVector(unsigned s, bool t = false) {
143    if (s <= SmallNumDataBits)
144      switchToSmall(t ? ~uintptr_t(0) : 0, s);
145    else
146      switchToLarge(new BitVector(s, t));
147  }
148
149  /// SmallBitVector copy ctor.
150  SmallBitVector(const SmallBitVector &RHS) {
151    if (RHS.isSmall())
152      X = RHS.X;
153    else
154      switchToLarge(new BitVector(*RHS.getPointer()));
155  }
156
157  SmallBitVector(SmallBitVector &&RHS) : X(RHS.X) {
158    RHS.X = 1;
159  }
160
161  ~SmallBitVector() {
162    if (!isSmall())
163      delete getPointer();
164  }
165
166  /// empty - Tests whether there are no bits in this bitvector.
167  bool empty() const {
168    return isSmall() ? getSmallSize() == 0 : getPointer()->empty();
169  }
170
171  /// size - Returns the number of bits in this bitvector.
172  size_t size() const {
173    return isSmall() ? getSmallSize() : getPointer()->size();
174  }
175
176  /// count - Returns the number of bits which are set.
177  size_type count() const {
178    if (isSmall()) {
179      uintptr_t Bits = getSmallBits();
180      if (NumBaseBits == 32)
181        return CountPopulation_32(Bits);
182      if (NumBaseBits == 64)
183        return CountPopulation_64(Bits);
184      llvm_unreachable("Unsupported!");
185    }
186    return getPointer()->count();
187  }
188
189  /// any - Returns true if any bit is set.
190  bool any() const {
191    if (isSmall())
192      return getSmallBits() != 0;
193    return getPointer()->any();
194  }
195
196  /// all - Returns true if all bits are set.
197  bool all() const {
198    if (isSmall())
199      return getSmallBits() == (uintptr_t(1) << getSmallSize()) - 1;
200    return getPointer()->all();
201  }
202
203  /// none - Returns true if none of the bits are set.
204  bool none() const {
205    if (isSmall())
206      return getSmallBits() == 0;
207    return getPointer()->none();
208  }
209
210  /// find_first - Returns the index of the first set bit, -1 if none
211  /// of the bits are set.
212  int find_first() const {
213    if (isSmall()) {
214      uintptr_t Bits = getSmallBits();
215      if (Bits == 0)
216        return -1;
217      if (NumBaseBits == 32)
218        return countTrailingZeros(Bits);
219      if (NumBaseBits == 64)
220        return countTrailingZeros(Bits);
221      llvm_unreachable("Unsupported!");
222    }
223    return getPointer()->find_first();
224  }
225
226  /// find_next - Returns the index of the next set bit following the
227  /// "Prev" bit. Returns -1 if the next set bit is not found.
228  int find_next(unsigned Prev) const {
229    if (isSmall()) {
230      uintptr_t Bits = getSmallBits();
231      // Mask off previous bits.
232      Bits &= ~uintptr_t(0) << (Prev + 1);
233      if (Bits == 0 || Prev + 1 >= getSmallSize())
234        return -1;
235      if (NumBaseBits == 32)
236        return countTrailingZeros(Bits);
237      if (NumBaseBits == 64)
238        return countTrailingZeros(Bits);
239      llvm_unreachable("Unsupported!");
240    }
241    return getPointer()->find_next(Prev);
242  }
243
244  /// clear - Clear all bits.
245  void clear() {
246    if (!isSmall())
247      delete getPointer();
248    switchToSmall(0, 0);
249  }
250
251  /// resize - Grow or shrink the bitvector.
252  void resize(unsigned N, bool t = false) {
253    if (!isSmall()) {
254      getPointer()->resize(N, t);
255    } else if (SmallNumDataBits >= N) {
256      uintptr_t NewBits = t ? ~uintptr_t(0) << getSmallSize() : 0;
257      setSmallSize(N);
258      setSmallBits(NewBits | getSmallBits());
259    } else {
260      BitVector *BV = new BitVector(N, t);
261      uintptr_t OldBits = getSmallBits();
262      for (size_t i = 0, e = getSmallSize(); i != e; ++i)
263        (*BV)[i] = (OldBits >> i) & 1;
264      switchToLarge(BV);
265    }
266  }
267
268  void reserve(unsigned N) {
269    if (isSmall()) {
270      if (N > SmallNumDataBits) {
271        uintptr_t OldBits = getSmallRawBits();
272        size_t SmallSize = getSmallSize();
273        BitVector *BV = new BitVector(SmallSize);
274        for (size_t i = 0; i < SmallSize; ++i)
275          if ((OldBits >> i) & 1)
276            BV->set(i);
277        BV->reserve(N);
278        switchToLarge(BV);
279      }
280    } else {
281      getPointer()->reserve(N);
282    }
283  }
284
285  // Set, reset, flip
286  SmallBitVector &set() {
287    if (isSmall())
288      setSmallBits(~uintptr_t(0));
289    else
290      getPointer()->set();
291    return *this;
292  }
293
294  SmallBitVector &set(unsigned Idx) {
295    if (isSmall())
296      setSmallBits(getSmallBits() | (uintptr_t(1) << Idx));
297    else
298      getPointer()->set(Idx);
299    return *this;
300  }
301
302  /// set - Efficiently set a range of bits in [I, E)
303  SmallBitVector &set(unsigned I, unsigned E) {
304    assert(I <= E && "Attempted to set backwards range!");
305    assert(E <= size() && "Attempted to set out-of-bounds range!");
306    if (I == E) return *this;
307    if (isSmall()) {
308      uintptr_t EMask = ((uintptr_t)1) << E;
309      uintptr_t IMask = ((uintptr_t)1) << I;
310      uintptr_t Mask = EMask - IMask;
311      setSmallBits(getSmallBits() | Mask);
312    } else
313      getPointer()->set(I, E);
314    return *this;
315  }
316
317  SmallBitVector &reset() {
318    if (isSmall())
319      setSmallBits(0);
320    else
321      getPointer()->reset();
322    return *this;
323  }
324
325  SmallBitVector &reset(unsigned Idx) {
326    if (isSmall())
327      setSmallBits(getSmallBits() & ~(uintptr_t(1) << Idx));
328    else
329      getPointer()->reset(Idx);
330    return *this;
331  }
332
333  /// reset - Efficiently reset a range of bits in [I, E)
334  SmallBitVector &reset(unsigned I, unsigned E) {
335    assert(I <= E && "Attempted to reset backwards range!");
336    assert(E <= size() && "Attempted to reset out-of-bounds range!");
337    if (I == E) return *this;
338    if (isSmall()) {
339      uintptr_t EMask = ((uintptr_t)1) << E;
340      uintptr_t IMask = ((uintptr_t)1) << I;
341      uintptr_t Mask = EMask - IMask;
342      setSmallBits(getSmallBits() & ~Mask);
343    } else
344      getPointer()->reset(I, E);
345    return *this;
346  }
347
348  SmallBitVector &flip() {
349    if (isSmall())
350      setSmallBits(~getSmallBits());
351    else
352      getPointer()->flip();
353    return *this;
354  }
355
356  SmallBitVector &flip(unsigned Idx) {
357    if (isSmall())
358      setSmallBits(getSmallBits() ^ (uintptr_t(1) << Idx));
359    else
360      getPointer()->flip(Idx);
361    return *this;
362  }
363
364  // No argument flip.
365  SmallBitVector operator~() const {
366    return SmallBitVector(*this).flip();
367  }
368
369  // Indexing.
370  reference operator[](unsigned Idx) {
371    assert(Idx < size() && "Out-of-bounds Bit access.");
372    return reference(*this, Idx);
373  }
374
375  bool operator[](unsigned Idx) const {
376    assert(Idx < size() && "Out-of-bounds Bit access.");
377    if (isSmall())
378      return ((getSmallBits() >> Idx) & 1) != 0;
379    return getPointer()->operator[](Idx);
380  }
381
382  bool test(unsigned Idx) const {
383    return (*this)[Idx];
384  }
385
386  /// Test if any common bits are set.
387  bool anyCommon(const SmallBitVector &RHS) const {
388    if (isSmall() && RHS.isSmall())
389      return (getSmallBits() & RHS.getSmallBits()) != 0;
390    if (!isSmall() && !RHS.isSmall())
391      return getPointer()->anyCommon(*RHS.getPointer());
392
393    for (unsigned i = 0, e = std::min(size(), RHS.size()); i != e; ++i)
394      if (test(i) && RHS.test(i))
395        return true;
396    return false;
397  }
398
399  // Comparison operators.
400  bool operator==(const SmallBitVector &RHS) const {
401    if (size() != RHS.size())
402      return false;
403    if (isSmall())
404      return getSmallBits() == RHS.getSmallBits();
405    else
406      return *getPointer() == *RHS.getPointer();
407  }
408
409  bool operator!=(const SmallBitVector &RHS) const {
410    return !(*this == RHS);
411  }
412
413  // Intersection, union, disjoint union.
414  SmallBitVector &operator&=(const SmallBitVector &RHS) {
415    resize(std::max(size(), RHS.size()));
416    if (isSmall())
417      setSmallBits(getSmallBits() & RHS.getSmallBits());
418    else if (!RHS.isSmall())
419      getPointer()->operator&=(*RHS.getPointer());
420    else {
421      SmallBitVector Copy = RHS;
422      Copy.resize(size());
423      getPointer()->operator&=(*Copy.getPointer());
424    }
425    return *this;
426  }
427
428  /// reset - Reset bits that are set in RHS. Same as *this &= ~RHS.
429  SmallBitVector &reset(const SmallBitVector &RHS) {
430    if (isSmall() && RHS.isSmall())
431      setSmallBits(getSmallBits() & ~RHS.getSmallBits());
432    else if (!isSmall() && !RHS.isSmall())
433      getPointer()->reset(*RHS.getPointer());
434    else
435      for (unsigned i = 0, e = std::min(size(), RHS.size()); i != e; ++i)
436        if (RHS.test(i))
437          reset(i);
438
439    return *this;
440  }
441
442  /// test - Check if (This - RHS) is zero.
443  /// This is the same as reset(RHS) and any().
444  bool test(const SmallBitVector &RHS) const {
445    if (isSmall() && RHS.isSmall())
446      return (getSmallBits() & ~RHS.getSmallBits()) != 0;
447    if (!isSmall() && !RHS.isSmall())
448      return getPointer()->test(*RHS.getPointer());
449
450    unsigned i, e;
451    for (i = 0, e = std::min(size(), RHS.size()); i != e; ++i)
452      if (test(i) && !RHS.test(i))
453        return true;
454
455    for (e = size(); i != e; ++i)
456      if (test(i))
457        return true;
458
459    return false;
460  }
461
462  SmallBitVector &operator|=(const SmallBitVector &RHS) {
463    resize(std::max(size(), RHS.size()));
464    if (isSmall())
465      setSmallBits(getSmallBits() | RHS.getSmallBits());
466    else if (!RHS.isSmall())
467      getPointer()->operator|=(*RHS.getPointer());
468    else {
469      SmallBitVector Copy = RHS;
470      Copy.resize(size());
471      getPointer()->operator|=(*Copy.getPointer());
472    }
473    return *this;
474  }
475
476  SmallBitVector &operator^=(const SmallBitVector &RHS) {
477    resize(std::max(size(), RHS.size()));
478    if (isSmall())
479      setSmallBits(getSmallBits() ^ RHS.getSmallBits());
480    else if (!RHS.isSmall())
481      getPointer()->operator^=(*RHS.getPointer());
482    else {
483      SmallBitVector Copy = RHS;
484      Copy.resize(size());
485      getPointer()->operator^=(*Copy.getPointer());
486    }
487    return *this;
488  }
489
490  // Assignment operator.
491  const SmallBitVector &operator=(const SmallBitVector &RHS) {
492    if (isSmall()) {
493      if (RHS.isSmall())
494        X = RHS.X;
495      else
496        switchToLarge(new BitVector(*RHS.getPointer()));
497    } else {
498      if (!RHS.isSmall())
499        *getPointer() = *RHS.getPointer();
500      else {
501        delete getPointer();
502        X = RHS.X;
503      }
504    }
505    return *this;
506  }
507
508  const SmallBitVector &operator=(SmallBitVector &&RHS) {
509    if (this != &RHS) {
510      clear();
511      swap(RHS);
512    }
513    return *this;
514  }
515
516  void swap(SmallBitVector &RHS) {
517    std::swap(X, RHS.X);
518  }
519
520  /// setBitsInMask - Add '1' bits from Mask to this vector. Don't resize.
521  /// This computes "*this |= Mask".
522  void setBitsInMask(const uint32_t *Mask, unsigned MaskWords = ~0u) {
523    if (isSmall())
524      applyMask<true, false>(Mask, MaskWords);
525    else
526      getPointer()->setBitsInMask(Mask, MaskWords);
527  }
528
529  /// clearBitsInMask - Clear any bits in this vector that are set in Mask.
530  /// Don't resize. This computes "*this &= ~Mask".
531  void clearBitsInMask(const uint32_t *Mask, unsigned MaskWords = ~0u) {
532    if (isSmall())
533      applyMask<false, false>(Mask, MaskWords);
534    else
535      getPointer()->clearBitsInMask(Mask, MaskWords);
536  }
537
538  /// setBitsNotInMask - Add a bit to this vector for every '0' bit in Mask.
539  /// Don't resize.  This computes "*this |= ~Mask".
540  void setBitsNotInMask(const uint32_t *Mask, unsigned MaskWords = ~0u) {
541    if (isSmall())
542      applyMask<true, true>(Mask, MaskWords);
543    else
544      getPointer()->setBitsNotInMask(Mask, MaskWords);
545  }
546
547  /// clearBitsNotInMask - Clear a bit in this vector for every '0' bit in Mask.
548  /// Don't resize.  This computes "*this &= Mask".
549  void clearBitsNotInMask(const uint32_t *Mask, unsigned MaskWords = ~0u) {
550    if (isSmall())
551      applyMask<false, true>(Mask, MaskWords);
552    else
553      getPointer()->clearBitsNotInMask(Mask, MaskWords);
554  }
555
556private:
557  template<bool AddBits, bool InvertMask>
558  void applyMask(const uint32_t *Mask, unsigned MaskWords) {
559    assert((NumBaseBits == 64 || NumBaseBits == 32) && "Unsupported word size");
560    if (NumBaseBits == 64 && MaskWords >= 2) {
561      uint64_t M = Mask[0] | (uint64_t(Mask[1]) << 32);
562      if (InvertMask) M = ~M;
563      if (AddBits) setSmallBits(getSmallBits() | M);
564      else         setSmallBits(getSmallBits() & ~M);
565    } else {
566      uint32_t M = Mask[0];
567      if (InvertMask) M = ~M;
568      if (AddBits) setSmallBits(getSmallBits() | M);
569      else         setSmallBits(getSmallBits() & ~M);
570    }
571  }
572};
573
574inline SmallBitVector
575operator&(const SmallBitVector &LHS, const SmallBitVector &RHS) {
576  SmallBitVector Result(LHS);
577  Result &= RHS;
578  return Result;
579}
580
581inline SmallBitVector
582operator|(const SmallBitVector &LHS, const SmallBitVector &RHS) {
583  SmallBitVector Result(LHS);
584  Result |= RHS;
585  return Result;
586}
587
588inline SmallBitVector
589operator^(const SmallBitVector &LHS, const SmallBitVector &RHS) {
590  SmallBitVector Result(LHS);
591  Result ^= RHS;
592  return Result;
593}
594
595} // End llvm namespace
596
597namespace std {
598  /// Implement std::swap in terms of BitVector swap.
599  inline void
600  swap(llvm::SmallBitVector &LHS, llvm::SmallBitVector &RHS) {
601    LHS.swap(RHS);
602  }
603}
604
605#endif
606