1 //===- llvm/ADT/DenseMapInfo.h - Type traits for DenseMap -------*- 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 /// \file
10 /// This file defines DenseMapInfo traits for DenseMap.
11 ///
12 //===----------------------------------------------------------------------===//
13 
14 #ifndef LLVM_ADT_DENSEMAPINFO_H
15 #define LLVM_ADT_DENSEMAPINFO_H
16 
17 #include <cassert>
18 #include <cstddef>
19 #include <cstdint>
20 #include <tuple>
21 #include <type_traits>
22 #include <utility>
23 #include <variant>
24 
25 namespace llvm {
26 
27 namespace detail {
28 
29 /// Simplistic combination of 32-bit hash values into 32-bit hash values.
combineHashValue(unsigned a,unsigned b)30 static inline unsigned combineHashValue(unsigned a, unsigned b) {
31   uint64_t key = (uint64_t)a << 32 | (uint64_t)b;
32   key += ~(key << 32);
33   key ^= (key >> 22);
34   key += ~(key << 13);
35   key ^= (key >> 8);
36   key += (key << 3);
37   key ^= (key >> 15);
38   key += ~(key << 27);
39   key ^= (key >> 31);
40   return (unsigned)key;
41 }
42 
43 } // end namespace detail
44 
45 /// An information struct used to provide DenseMap with the various necessary
46 /// components for a given value type `T`. `Enable` is an optional additional
47 /// parameter that is used to support SFINAE (generally using std::enable_if_t)
48 /// in derived DenseMapInfo specializations; in non-SFINAE use cases this should
49 /// just be `void`.
50 template<typename T, typename Enable = void>
51 struct DenseMapInfo {
52   //static inline T getEmptyKey();
53   //static inline T getTombstoneKey();
54   //static unsigned getHashValue(const T &Val);
55   //static bool isEqual(const T &LHS, const T &RHS);
56 };
57 
58 // Provide DenseMapInfo for all pointers. Come up with sentinel pointer values
59 // that are aligned to alignof(T) bytes, but try to avoid requiring T to be
60 // complete. This allows clients to instantiate DenseMap<T*, ...> with forward
61 // declared key types. Assume that no pointer key type requires more than 4096
62 // bytes of alignment.
63 template<typename T>
64 struct DenseMapInfo<T*> {
65   // The following should hold, but it would require T to be complete:
66   // static_assert(alignof(T) <= (1 << Log2MaxAlign),
67   //               "DenseMap does not support pointer keys requiring more than "
68   //               "Log2MaxAlign bits of alignment");
69   static constexpr uintptr_t Log2MaxAlign = 12;
70 
71   static inline T* getEmptyKey() {
72     uintptr_t Val = static_cast<uintptr_t>(-1);
73     Val <<= Log2MaxAlign;
74     return reinterpret_cast<T*>(Val);
75   }
76 
77   static inline T* getTombstoneKey() {
78     uintptr_t Val = static_cast<uintptr_t>(-2);
79     Val <<= Log2MaxAlign;
80     return reinterpret_cast<T*>(Val);
81   }
82 
83   static unsigned getHashValue(const T *PtrVal) {
84     return (unsigned((uintptr_t)PtrVal) >> 4) ^
85            (unsigned((uintptr_t)PtrVal) >> 9);
86   }
87 
88   static bool isEqual(const T *LHS, const T *RHS) { return LHS == RHS; }
89 };
90 
91 // Provide DenseMapInfo for chars.
92 template<> struct DenseMapInfo<char> {
93   static inline char getEmptyKey() { return ~0; }
94   static inline char getTombstoneKey() { return ~0 - 1; }
95   static unsigned getHashValue(const char& Val) { return Val * 37U; }
96 
97   static bool isEqual(const char &LHS, const char &RHS) {
98     return LHS == RHS;
99   }
100 };
101 
102 // Provide DenseMapInfo for unsigned chars.
103 template <> struct DenseMapInfo<unsigned char> {
104   static inline unsigned char getEmptyKey() { return ~0; }
105   static inline unsigned char getTombstoneKey() { return ~0 - 1; }
106   static unsigned getHashValue(const unsigned char &Val) { return Val * 37U; }
107 
108   static bool isEqual(const unsigned char &LHS, const unsigned char &RHS) {
109     return LHS == RHS;
110   }
111 };
112 
113 // Provide DenseMapInfo for unsigned shorts.
114 template <> struct DenseMapInfo<unsigned short> {
115   static inline unsigned short getEmptyKey() { return 0xFFFF; }
116   static inline unsigned short getTombstoneKey() { return 0xFFFF - 1; }
117   static unsigned getHashValue(const unsigned short &Val) { return Val * 37U; }
118 
119   static bool isEqual(const unsigned short &LHS, const unsigned short &RHS) {
120     return LHS == RHS;
121   }
122 };
123 
124 // Provide DenseMapInfo for unsigned ints.
125 template<> struct DenseMapInfo<unsigned> {
126   static inline unsigned getEmptyKey() { return ~0U; }
127   static inline unsigned getTombstoneKey() { return ~0U - 1; }
128   static unsigned getHashValue(const unsigned& Val) { return Val * 37U; }
129 
130   static bool isEqual(const unsigned& LHS, const unsigned& RHS) {
131     return LHS == RHS;
132   }
133 };
134 
135 // Provide DenseMapInfo for unsigned longs.
136 template<> struct DenseMapInfo<unsigned long> {
137   static inline unsigned long getEmptyKey() { return ~0UL; }
138   static inline unsigned long getTombstoneKey() { return ~0UL - 1L; }
139 
140   static unsigned getHashValue(const unsigned long& Val) {
141     return (unsigned)(Val * 37UL);
142   }
143 
144   static bool isEqual(const unsigned long& LHS, const unsigned long& RHS) {
145     return LHS == RHS;
146   }
147 };
148 
149 // Provide DenseMapInfo for unsigned long longs.
150 template<> struct DenseMapInfo<unsigned long long> {
151   static inline unsigned long long getEmptyKey() { return ~0ULL; }
152   static inline unsigned long long getTombstoneKey() { return ~0ULL - 1ULL; }
153 
154   static unsigned getHashValue(const unsigned long long& Val) {
155     return (unsigned)(Val * 37ULL);
156   }
157 
158   static bool isEqual(const unsigned long long& LHS,
159                       const unsigned long long& RHS) {
160     return LHS == RHS;
161   }
162 };
163 
164 // Provide DenseMapInfo for shorts.
165 template <> struct DenseMapInfo<short> {
166   static inline short getEmptyKey() { return 0x7FFF; }
167   static inline short getTombstoneKey() { return -0x7FFF - 1; }
168   static unsigned getHashValue(const short &Val) { return Val * 37U; }
169   static bool isEqual(const short &LHS, const short &RHS) { return LHS == RHS; }
170 };
171 
172 // Provide DenseMapInfo for ints.
173 template<> struct DenseMapInfo<int> {
174   static inline int getEmptyKey() { return 0x7fffffff; }
175   static inline int getTombstoneKey() { return -0x7fffffff - 1; }
176   static unsigned getHashValue(const int& Val) { return (unsigned)(Val * 37U); }
177 
178   static bool isEqual(const int& LHS, const int& RHS) {
179     return LHS == RHS;
180   }
181 };
182 
183 // Provide DenseMapInfo for longs.
184 template<> struct DenseMapInfo<long> {
185   static inline long getEmptyKey() {
186     return (1UL << (sizeof(long) * 8 - 1)) - 1UL;
187   }
188 
189   static inline long getTombstoneKey() { return getEmptyKey() - 1L; }
190 
191   static unsigned getHashValue(const long& Val) {
192     return (unsigned)(Val * 37UL);
193   }
194 
195   static bool isEqual(const long& LHS, const long& RHS) {
196     return LHS == RHS;
197   }
198 };
199 
200 // Provide DenseMapInfo for long longs.
201 template<> struct DenseMapInfo<long long> {
202   static inline long long getEmptyKey() { return 0x7fffffffffffffffLL; }
203   static inline long long getTombstoneKey() { return -0x7fffffffffffffffLL-1; }
204 
205   static unsigned getHashValue(const long long& Val) {
206     return (unsigned)(Val * 37ULL);
207   }
208 
209   static bool isEqual(const long long& LHS,
210                       const long long& RHS) {
211     return LHS == RHS;
212   }
213 };
214 
215 // Provide DenseMapInfo for all pairs whose members have info.
216 template<typename T, typename U>
217 struct DenseMapInfo<std::pair<T, U>> {
218   using Pair = std::pair<T, U>;
219   using FirstInfo = DenseMapInfo<T>;
220   using SecondInfo = DenseMapInfo<U>;
221 
222   static inline Pair getEmptyKey() {
223     return std::make_pair(FirstInfo::getEmptyKey(),
224                           SecondInfo::getEmptyKey());
225   }
226 
227   static inline Pair getTombstoneKey() {
228     return std::make_pair(FirstInfo::getTombstoneKey(),
229                           SecondInfo::getTombstoneKey());
230   }
231 
232   static unsigned getHashValue(const Pair& PairVal) {
233     return detail::combineHashValue(FirstInfo::getHashValue(PairVal.first),
234                                     SecondInfo::getHashValue(PairVal.second));
235   }
236 
237   static bool isEqual(const Pair &LHS, const Pair &RHS) {
238     return FirstInfo::isEqual(LHS.first, RHS.first) &&
239            SecondInfo::isEqual(LHS.second, RHS.second);
240   }
241 };
242 
243 // Provide DenseMapInfo for all tuples whose members have info.
244 template <typename... Ts> struct DenseMapInfo<std::tuple<Ts...>> {
245   using Tuple = std::tuple<Ts...>;
246 
247   static inline Tuple getEmptyKey() {
248     return Tuple(DenseMapInfo<Ts>::getEmptyKey()...);
249   }
250 
251   static inline Tuple getTombstoneKey() {
252     return Tuple(DenseMapInfo<Ts>::getTombstoneKey()...);
253   }
254 
255   template <unsigned I>
256   static unsigned getHashValueImpl(const Tuple &values, std::false_type) {
257     using EltType = std::tuple_element_t<I, Tuple>;
258     std::integral_constant<bool, I + 1 == sizeof...(Ts)> atEnd;
259     return detail::combineHashValue(
260         DenseMapInfo<EltType>::getHashValue(std::get<I>(values)),
261         getHashValueImpl<I + 1>(values, atEnd));
262   }
263 
264   template <unsigned I>
265   static unsigned getHashValueImpl(const Tuple &, std::true_type) {
266     return 0;
267   }
268 
269   static unsigned getHashValue(const std::tuple<Ts...> &values) {
270     std::integral_constant<bool, 0 == sizeof...(Ts)> atEnd;
271     return getHashValueImpl<0>(values, atEnd);
272   }
273 
274   template <unsigned I>
275   static bool isEqualImpl(const Tuple &lhs, const Tuple &rhs, std::false_type) {
276     using EltType = std::tuple_element_t<I, Tuple>;
277     std::integral_constant<bool, I + 1 == sizeof...(Ts)> atEnd;
278     return DenseMapInfo<EltType>::isEqual(std::get<I>(lhs), std::get<I>(rhs)) &&
279            isEqualImpl<I + 1>(lhs, rhs, atEnd);
280   }
281 
282   template <unsigned I>
283   static bool isEqualImpl(const Tuple &, const Tuple &, std::true_type) {
284     return true;
285   }
286 
287   static bool isEqual(const Tuple &lhs, const Tuple &rhs) {
288     std::integral_constant<bool, 0 == sizeof...(Ts)> atEnd;
289     return isEqualImpl<0>(lhs, rhs, atEnd);
290   }
291 };
292 
293 // Provide DenseMapInfo for variants whose all alternatives have DenseMapInfo.
294 template <typename... Ts> struct DenseMapInfo<std::variant<Ts...>> {
295   using Variant = std::variant<Ts...>;
296   using FirstT = std::variant_alternative_t<0, Variant>;
297 
298   static inline Variant getEmptyKey() {
299     return Variant(std::in_place_index<0>, DenseMapInfo<FirstT>::getEmptyKey());
300   }
301 
302   static inline Variant getTombstoneKey() {
303     return Variant(std::in_place_index<0>,
304                    DenseMapInfo<FirstT>::getTombstoneKey());
305   }
306 
307   static unsigned getHashValue(const Variant &Val) {
308     return std::visit(
309         [&Val](auto &&Alternative) {
310           using T = std::decay_t<decltype(Alternative)>;
311           // Include index in hash to make sure same value as different
312           // alternatives don't collide.
313           return detail::combineHashValue(
314               DenseMapInfo<size_t>::getHashValue(Val.index()),
315               DenseMapInfo<T>::getHashValue(Alternative));
316         },
317         Val);
318   }
319 
320   static bool isEqual(const Variant &LHS, const Variant &RHS) {
321     return LHS == RHS;
322   }
323 };
324 } // end namespace llvm
325 
326 #endif // LLVM_ADT_DENSEMAPINFO_H
327