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      1 //===- llvm/ADT/PackedVector.h - Packed values vector -----------*- 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 PackedVector class.
     11 //
     12 //===----------------------------------------------------------------------===//
     13 
     14 #ifndef LLVM_ADT_PACKEDVECTOR_H
     15 #define LLVM_ADT_PACKEDVECTOR_H
     16 
     17 #include "llvm/ADT/BitVector.h"
     18 #include <limits>
     19 
     20 namespace llvm {
     21 
     22 template <typename T, unsigned BitNum, typename BitVectorTy, bool isSigned>
     23 class PackedVectorBase;
     24 
     25 // This won't be necessary if we can specialize members without specializing
     26 // the parent template.
     27 template <typename T, unsigned BitNum, typename BitVectorTy>
     28 class PackedVectorBase<T, BitNum, BitVectorTy, false> {
     29 protected:
     30   static T getValue(const BitVectorTy &Bits, unsigned Idx) {
     31     T val = T();
     32     for (unsigned i = 0; i != BitNum; ++i)
     33       val = T(val | ((Bits[(Idx << (BitNum-1)) + i] ? 1UL : 0UL) << i));
     34     return val;
     35   }
     36 
     37   static void setValue(BitVectorTy &Bits, unsigned Idx, T val) {
     38     assert((val >> BitNum) == 0 && "value is too big");
     39     for (unsigned i = 0; i != BitNum; ++i)
     40       Bits[(Idx << (BitNum-1)) + i] = val & (T(1) << i);
     41   }
     42 };
     43 
     44 template <typename T, unsigned BitNum, typename BitVectorTy>
     45 class PackedVectorBase<T, BitNum, BitVectorTy, true> {
     46 protected:
     47   static T getValue(const BitVectorTy &Bits, unsigned Idx) {
     48     T val = T();
     49     for (unsigned i = 0; i != BitNum-1; ++i)
     50       val = T(val | ((Bits[(Idx << (BitNum-1)) + i] ? 1UL : 0UL) << i));
     51     if (Bits[(Idx << (BitNum-1)) + BitNum-1])
     52       val = ~val;
     53     return val;
     54   }
     55 
     56   static void setValue(BitVectorTy &Bits, unsigned Idx, T val) {
     57     if (val < 0) {
     58       val = ~val;
     59       Bits.set((Idx << (BitNum-1)) + BitNum-1);
     60     }
     61     assert((val >> (BitNum-1)) == 0 && "value is too big");
     62     for (unsigned i = 0; i != BitNum-1; ++i)
     63       Bits[(Idx << (BitNum-1)) + i] = val & (T(1) << i);
     64   }
     65 };
     66 
     67 /// \brief Store a vector of values using a specific number of bits for each
     68 /// value. Both signed and unsigned types can be used, e.g
     69 /// @code
     70 ///   PackedVector<signed, 2> vec;
     71 /// @endcode
     72 /// will create a vector accepting values -2, -1, 0, 1. Any other value will hit
     73 /// an assertion.
     74 template <typename T, unsigned BitNum, typename BitVectorTy = BitVector>
     75 class PackedVector : public PackedVectorBase<T, BitNum, BitVectorTy,
     76                                             std::numeric_limits<T>::is_signed> {
     77   BitVectorTy Bits;
     78   typedef PackedVectorBase<T, BitNum, BitVectorTy,
     79                            std::numeric_limits<T>::is_signed> base;
     80 
     81 public:
     82   class reference {
     83     PackedVector &Vec;
     84     const unsigned Idx;
     85 
     86     reference(); // Undefined
     87   public:
     88     reference(PackedVector &vec, unsigned idx) : Vec(vec), Idx(idx) {}
     89 
     90     reference &operator=(T val) {
     91       Vec.setValue(Vec.Bits, Idx, val);
     92       return *this;
     93     }
     94     operator T() const {
     95       return Vec.getValue(Vec.Bits, Idx);
     96     }
     97   };
     98 
     99   PackedVector() = default;
    100   explicit PackedVector(unsigned size) : Bits(size << (BitNum-1)) { }
    101 
    102   bool empty() const { return Bits.empty(); }
    103 
    104   unsigned size() const { return Bits.size() >> (BitNum - 1); }
    105 
    106   void clear() { Bits.clear(); }
    107 
    108   void resize(unsigned N) { Bits.resize(N << (BitNum - 1)); }
    109 
    110   void reserve(unsigned N) { Bits.reserve(N << (BitNum-1)); }
    111 
    112   PackedVector &reset() {
    113     Bits.reset();
    114     return *this;
    115   }
    116 
    117   void push_back(T val) {
    118     resize(size()+1);
    119     (*this)[size()-1] = val;
    120   }
    121 
    122   reference operator[](unsigned Idx) {
    123     return reference(*this, Idx);
    124   }
    125 
    126   T operator[](unsigned Idx) const {
    127     return base::getValue(Bits, Idx);
    128   }
    129 
    130   bool operator==(const PackedVector &RHS) const {
    131     return Bits == RHS.Bits;
    132   }
    133 
    134   bool operator!=(const PackedVector &RHS) const {
    135     return Bits != RHS.Bits;
    136   }
    137 
    138   PackedVector &operator|=(const PackedVector &RHS) {
    139     Bits |= RHS.Bits;
    140     return *this;
    141   }
    142 };
    143 
    144 // Leave BitNum=0 undefined.
    145 template <typename T> class PackedVector<T, 0>;
    146 
    147 } // end llvm namespace
    148 
    149 #endif
    150