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