include/llvm/ADT/PackedVector.h

   1 //===- llvm/ADT/PackedVector.h - Packed values vector -----------*- C++ -*-===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8 //
   9 // This file implements the PackedVector class.
  10 //
  11 //===----------------------------------------------------------------------===//
  12
  13 #ifndef LLVM_ADT_PACKEDVECTOR_H
  14 #define LLVM_ADT_PACKEDVECTOR_H
  15
  16 #include "llvm/ADT/BitVector.h"
  17 #include <cassert>
  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 /// 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   using base = PackedVectorBase<T, BitNum, BitVectorTy,
  79                                 std::numeric_limits<T>::is_signed>;
  80
  81 public:
  82   class reference {
  83     PackedVector &Vec;
  84     const unsigned Idx;
  85
  86   public:
  87     reference() = delete;
  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
  95     operator T() const {
  96       return Vec.getValue(Vec.Bits, Idx);
  97     }
  98   };
  99
 100   PackedVector() = default;
 101   explicit PackedVector(unsigned size) : Bits(size << (BitNum-1)) {}
 102
 103   bool empty() const { return Bits.empty(); }
 104
 105   unsigned size() const { return Bits.size() >> (BitNum - 1); }
 106
 107   void clear() { Bits.clear(); }
 108
 109   void resize(unsigned N) { Bits.resize(N << (BitNum - 1)); }
 110
 111   void reserve(unsigned N) { Bits.reserve(N << (BitNum-1)); }
 112
 113   PackedVector &reset() {
 114     Bits.reset();
 115     return *this;
 116   }
 117
 118   void push_back(T val) {
 119     resize(size()+1);
 120     (*this)[size()-1] = val;
 121   }
 122
 123   reference operator[](unsigned Idx) {
 124     return reference(*this, Idx);
 125   }
 126
 127   T operator[](unsigned Idx) const {
 128     return base::getValue(Bits, Idx);
 129   }
 130
 131   bool operator==(const PackedVector &RHS) const {
 132     return Bits == RHS.Bits;
 133   }
 134
 135   bool operator!=(const PackedVector &RHS) const {
 136     return Bits != RHS.Bits;
 137   }
 138
 139   PackedVector &operator|=(const PackedVector &RHS) {
 140     Bits |= RHS.Bits;
 141     return *this;
 142   }
 143 };
 144
 145 // Leave BitNum=0 undefined.
 146 template <typename T> class PackedVector<T, 0>;
 147
 148 } // end namespace llvm
 149
 150 #endif // LLVM_ADT_PACKEDVECTOR_H