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:
getValue(const BitVectorTy & Bits,unsigned Idx)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 
setValue(BitVectorTy & Bits,unsigned Idx,T val)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:
getValue(const BitVectorTy & Bits,unsigned Idx)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 
setValue(BitVectorTy & Bits,unsigned Idx,T val)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;
reference(PackedVector & vec,unsigned idx)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 
T()95     operator T() const {
96       return Vec.getValue(Vec.Bits, Idx);
97     }
98   };
99 
100   PackedVector() = default;
PackedVector(unsigned size)101   explicit PackedVector(unsigned size) : Bits(size << (BitNum-1)) {}
102 
empty()103   bool empty() const { return Bits.empty(); }
104 
size()105   unsigned size() const { return Bits.size() >> (BitNum - 1); }
106 
clear()107   void clear() { Bits.clear(); }
108 
resize(unsigned N)109   void resize(unsigned N) { Bits.resize(N << (BitNum - 1)); }
110 
reserve(unsigned N)111   void reserve(unsigned N) { Bits.reserve(N << (BitNum-1)); }
112 
reset()113   PackedVector &reset() {
114     Bits.reset();
115     return *this;
116   }
117 
push_back(T val)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
151