src/llvm/include/llvm/ADT/SmallBitVector.h

   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
  22 namespace 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 ///
  31 class 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
  56 public:
  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
  84 private:
  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
 136 public:
 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       assert(Idx <= static_cast<unsigned>(
 297                         std::numeric_limits<uintptr_t>::digits) &&
 298              "undefined behavior");
 299       setSmallBits(getSmallBits() | (uintptr_t(1) << Idx));
 300     }
 301     else
 302       getPointer()->set(Idx);
 303     return *this;
 304   }
 305
 306   /// set - Efficiently set a range of bits in [I, E)
 307   SmallBitVector &set(unsigned I, unsigned E) {
 308     assert(I <= E && "Attempted to set backwards range!");
 309     assert(E <= size() && "Attempted to set out-of-bounds range!");
 310     if (I == E) return *this;
 311     if (isSmall()) {
 312       uintptr_t EMask = ((uintptr_t)1) << E;
 313       uintptr_t IMask = ((uintptr_t)1) << I;
 314       uintptr_t Mask = EMask - IMask;
 315       setSmallBits(getSmallBits() | Mask);
 316     } else
 317       getPointer()->set(I, E);
 318     return *this;
 319   }
 320
 321   SmallBitVector &reset() {
 322     if (isSmall())
 323       setSmallBits(0);
 324     else
 325       getPointer()->reset();
 326     return *this;
 327   }
 328
 329   SmallBitVector &reset(unsigned Idx) {
 330     if (isSmall())
 331       setSmallBits(getSmallBits() & ~(uintptr_t(1) << Idx));
 332     else
 333       getPointer()->reset(Idx);
 334     return *this;
 335   }
 336
 337   /// reset - Efficiently reset a range of bits in [I, E)
 338   SmallBitVector &reset(unsigned I, unsigned E) {
 339     assert(I <= E && "Attempted to reset backwards range!");
 340     assert(E <= size() && "Attempted to reset out-of-bounds range!");
 341     if (I == E) return *this;
 342     if (isSmall()) {
 343       uintptr_t EMask = ((uintptr_t)1) << E;
 344       uintptr_t IMask = ((uintptr_t)1) << I;
 345       uintptr_t Mask = EMask - IMask;
 346       setSmallBits(getSmallBits() & ~Mask);
 347     } else
 348       getPointer()->reset(I, E);
 349     return *this;
 350   }
 351
 352   SmallBitVector &flip() {
 353     if (isSmall())
 354       setSmallBits(~getSmallBits());
 355     else
 356       getPointer()->flip();
 357     return *this;
 358   }
 359
 360   SmallBitVector &flip(unsigned Idx) {
 361     if (isSmall())
 362       setSmallBits(getSmallBits() ^ (uintptr_t(1) << Idx));
 363     else
 364       getPointer()->flip(Idx);
 365     return *this;
 366   }
 367
 368   // No argument flip.
 369   SmallBitVector operator~() const {
 370     return SmallBitVector(*this).flip();
 371   }
 372
 373   // Indexing.
 374   reference operator[](unsigned Idx) {
 375     assert(Idx < size() && "Out-of-bounds Bit access.");
 376     return reference(*this, Idx);
 377   }
 378
 379   bool operator[](unsigned Idx) const {
 380     assert(Idx < size() && "Out-of-bounds Bit access.");
 381     if (isSmall())
 382       return ((getSmallBits() >> Idx) & 1) != 0;
 383     return getPointer()->operator[](Idx);
 384   }
 385
 386   bool test(unsigned Idx) const {
 387     return (*this)[Idx];
 388   }
 389
 390   /// Test if any common bits are set.
 391   bool anyCommon(const SmallBitVector &RHS) const {
 392     if (isSmall() && RHS.isSmall())
 393       return (getSmallBits() & RHS.getSmallBits()) != 0;
 394     if (!isSmall() && !RHS.isSmall())
 395       return getPointer()->anyCommon(*RHS.getPointer());
 396
 397     for (unsigned i = 0, e = std::min(size(), RHS.size()); i != e; ++i)
 398       if (test(i) && RHS.test(i))
 399         return true;
 400     return false;
 401   }
 402
 403   // Comparison operators.
 404   bool operator==(const SmallBitVector &RHS) const {
 405     if (size() != RHS.size())
 406       return false;
 407     if (isSmall())
 408       return getSmallBits() == RHS.getSmallBits();
 409     else
 410       return *getPointer() == *RHS.getPointer();
 411   }
 412
 413   bool operator!=(const SmallBitVector &RHS) const {
 414     return !(*this == RHS);
 415   }
 416
 417   // Intersection, union, disjoint union.
 418   SmallBitVector &operator&=(const SmallBitVector &RHS) {
 419     resize(std::max(size(), RHS.size()));
 420     if (isSmall())
 421       setSmallBits(getSmallBits() & RHS.getSmallBits());
 422     else if (!RHS.isSmall())
 423       getPointer()->operator&=(*RHS.getPointer());
 424     else {
 425       SmallBitVector Copy = RHS;
 426       Copy.resize(size());
 427       getPointer()->operator&=(*Copy.getPointer());
 428     }
 429     return *this;
 430   }
 431
 432   /// reset - Reset bits that are set in RHS. Same as *this &= ~RHS.
 433   SmallBitVector &reset(const SmallBitVector &RHS) {
 434     if (isSmall() && RHS.isSmall())
 435       setSmallBits(getSmallBits() & ~RHS.getSmallBits());
 436     else if (!isSmall() && !RHS.isSmall())
 437       getPointer()->reset(*RHS.getPointer());
 438     else
 439       for (unsigned i = 0, e = std::min(size(), RHS.size()); i != e; ++i)
 440         if (RHS.test(i))
 441           reset(i);
 442
 443     return *this;
 444   }
 445
 446   /// test - Check if (This - RHS) is zero.
 447   /// This is the same as reset(RHS) and any().
 448   bool test(const SmallBitVector &RHS) const {
 449     if (isSmall() && RHS.isSmall())
 450       return (getSmallBits() & ~RHS.getSmallBits()) != 0;
 451     if (!isSmall() && !RHS.isSmall())
 452       return getPointer()->test(*RHS.getPointer());
 453
 454     unsigned i, e;
 455     for (i = 0, e = std::min(size(), RHS.size()); i != e; ++i)
 456       if (test(i) && !RHS.test(i))
 457         return true;
 458
 459     for (e = size(); i != e; ++i)
 460       if (test(i))
 461         return true;
 462
 463     return false;
 464   }
 465
 466   SmallBitVector &operator|=(const SmallBitVector &RHS) {
 467     resize(std::max(size(), RHS.size()));
 468     if (isSmall())
 469       setSmallBits(getSmallBits() | RHS.getSmallBits());
 470     else if (!RHS.isSmall())
 471       getPointer()->operator|=(*RHS.getPointer());
 472     else {
 473       SmallBitVector Copy = RHS;
 474       Copy.resize(size());
 475       getPointer()->operator|=(*Copy.getPointer());
 476     }
 477     return *this;
 478   }
 479
 480   SmallBitVector &operator^=(const SmallBitVector &RHS) {
 481     resize(std::max(size(), RHS.size()));
 482     if (isSmall())
 483       setSmallBits(getSmallBits() ^ RHS.getSmallBits());
 484     else if (!RHS.isSmall())
 485       getPointer()->operator^=(*RHS.getPointer());
 486     else {
 487       SmallBitVector Copy = RHS;
 488       Copy.resize(size());
 489       getPointer()->operator^=(*Copy.getPointer());
 490     }
 491     return *this;
 492   }
 493
 494   // Assignment operator.
 495   const SmallBitVector &operator=(const SmallBitVector &RHS) {
 496     if (isSmall()) {
 497       if (RHS.isSmall())
 498         X = RHS.X;
 499       else
 500         switchToLarge(new BitVector(*RHS.getPointer()));
 501     } else {
 502       if (!RHS.isSmall())
 503         *getPointer() = *RHS.getPointer();
 504       else {
 505         delete getPointer();
 506         X = RHS.X;
 507       }
 508     }
 509     return *this;
 510   }
 511
 512   const SmallBitVector &operator=(SmallBitVector &&RHS) {
 513     if (this != &RHS) {
 514       clear();
 515       swap(RHS);
 516     }
 517     return *this;
 518   }
 519
 520   void swap(SmallBitVector &RHS) {
 521     std::swap(X, RHS.X);
 522   }
 523
 524   /// setBitsInMask - Add '1' bits from Mask to this vector. Don't resize.
 525   /// This computes "*this |= Mask".
 526   void setBitsInMask(const uint32_t *Mask, unsigned MaskWords = ~0u) {
 527     if (isSmall())
 528       applyMask<true, false>(Mask, MaskWords);
 529     else
 530       getPointer()->setBitsInMask(Mask, MaskWords);
 531   }
 532
 533   /// clearBitsInMask - Clear any bits in this vector that are set in Mask.
 534   /// Don't resize. This computes "*this &= ~Mask".
 535   void clearBitsInMask(const uint32_t *Mask, unsigned MaskWords = ~0u) {
 536     if (isSmall())
 537       applyMask<false, false>(Mask, MaskWords);
 538     else
 539       getPointer()->clearBitsInMask(Mask, MaskWords);
 540   }
 541
 542   /// setBitsNotInMask - Add a bit to this vector for every '0' bit in Mask.
 543   /// Don't resize.  This computes "*this |= ~Mask".
 544   void setBitsNotInMask(const uint32_t *Mask, unsigned MaskWords = ~0u) {
 545     if (isSmall())
 546       applyMask<true, true>(Mask, MaskWords);
 547     else
 548       getPointer()->setBitsNotInMask(Mask, MaskWords);
 549   }
 550
 551   /// clearBitsNotInMask - Clear a bit in this vector for every '0' bit in Mask.
 552   /// Don't resize.  This computes "*this &= Mask".
 553   void clearBitsNotInMask(const uint32_t *Mask, unsigned MaskWords = ~0u) {
 554     if (isSmall())
 555       applyMask<false, true>(Mask, MaskWords);
 556     else
 557       getPointer()->clearBitsNotInMask(Mask, MaskWords);
 558   }
 559
 560 private:
 561   template<bool AddBits, bool InvertMask>
 562   void applyMask(const uint32_t *Mask, unsigned MaskWords) {
 563     assert((NumBaseBits == 64 || NumBaseBits == 32) && "Unsupported word size");
 564     if (NumBaseBits == 64 && MaskWords >= 2) {
 565       uint64_t M = Mask[0] | (uint64_t(Mask[1]) << 32);
 566       if (InvertMask) M = ~M;
 567       if (AddBits) setSmallBits(getSmallBits() | M);
 568       else         setSmallBits(getSmallBits() & ~M);
 569     } else {
 570       uint32_t M = Mask[0];
 571       if (InvertMask) M = ~M;
 572       if (AddBits) setSmallBits(getSmallBits() | M);
 573       else         setSmallBits(getSmallBits() & ~M);
 574     }
 575   }
 576 };
 577
 578 inline SmallBitVector
 579 operator&(const SmallBitVector &LHS, const SmallBitVector &RHS) {
 580   SmallBitVector Result(LHS);
 581   Result &= RHS;
 582   return Result;
 583 }
 584
 585 inline SmallBitVector
 586 operator|(const SmallBitVector &LHS, const SmallBitVector &RHS) {
 587   SmallBitVector Result(LHS);
 588   Result |= RHS;
 589   return Result;
 590 }
 591
 592 inline SmallBitVector
 593 operator^(const SmallBitVector &LHS, const SmallBitVector &RHS) {
 594   SmallBitVector Result(LHS);
 595   Result ^= RHS;
 596   return Result;
 597 }
 598
 599 } // End llvm namespace
 600
 601 namespace std {
 602   /// Implement std::swap in terms of BitVector swap.
 603   inline void
 604   swap(llvm::SmallBitVector &LHS, llvm::SmallBitVector &RHS) {
 605     LHS.swap(RHS);
 606   }
 607 }
 608
 609 #endif