1 //===- ScopedHashTable.h - A simple scoped hash table -----------*- 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 an efficient scoped hash table, which is useful for
10 // things like dominator-based optimizations. This allows clients to do things
11 // like this:
12 //
13 // ScopedHashTable<int, int> HT;
14 // {
15 // ScopedHashTableScope<int, int> Scope1(HT);
16 // HT.insert(0, 0);
17 // HT.insert(1, 1);
18 // {
19 // ScopedHashTableScope<int, int> Scope2(HT);
20 // HT.insert(0, 42);
21 // }
22 // }
23 //
24 // Looking up the value for "0" in the Scope2 block will return 42. Looking
25 // up the value for 0 before 42 is inserted or after Scope2 is popped will
26 // return 0.
27 //
28 //===----------------------------------------------------------------------===//
29
30 #ifndef LLVM_ADT_SCOPEDHASHTABLE_H
31 #define LLVM_ADT_SCOPEDHASHTABLE_H
32
33 #include "llvm/ADT/DenseMap.h"
34 #include "llvm/ADT/DenseMapInfo.h"
35 #include "llvm/Support/AllocatorBase.h"
36 #include <cassert>
37 #include <new>
38
39 namespace llvm {
40
41 template <typename K, typename V, typename KInfo = DenseMapInfo<K>,
42 typename AllocatorTy = MallocAllocator>
43 class ScopedHashTable;
44
45 template <typename K, typename V>
46 class ScopedHashTableVal {
47 ScopedHashTableVal *NextInScope;
48 ScopedHashTableVal *NextForKey;
49 K Key;
50 V Val;
51
ScopedHashTableVal(const K & key,const V & val)52 ScopedHashTableVal(const K &key, const V &val) : Key(key), Val(val) {}
53
54 public:
getKey()55 const K &getKey() const { return Key; }
getValue()56 const V &getValue() const { return Val; }
getValue()57 V &getValue() { return Val; }
58
getNextForKey()59 ScopedHashTableVal *getNextForKey() { return NextForKey; }
getNextForKey()60 const ScopedHashTableVal *getNextForKey() const { return NextForKey; }
getNextInScope()61 ScopedHashTableVal *getNextInScope() { return NextInScope; }
62
63 template <typename AllocatorTy>
Create(ScopedHashTableVal * nextInScope,ScopedHashTableVal * nextForKey,const K & key,const V & val,AllocatorTy & Allocator)64 static ScopedHashTableVal *Create(ScopedHashTableVal *nextInScope,
65 ScopedHashTableVal *nextForKey,
66 const K &key, const V &val,
67 AllocatorTy &Allocator) {
68 ScopedHashTableVal *New = Allocator.template Allocate<ScopedHashTableVal>();
69 // Set up the value.
70 new (New) ScopedHashTableVal(key, val);
71 New->NextInScope = nextInScope;
72 New->NextForKey = nextForKey;
73 return New;
74 }
75
Destroy(AllocatorTy & Allocator)76 template <typename AllocatorTy> void Destroy(AllocatorTy &Allocator) {
77 // Free memory referenced by the item.
78 this->~ScopedHashTableVal();
79 Allocator.Deallocate(this);
80 }
81 };
82
83 template <typename K, typename V, typename KInfo = DenseMapInfo<K>,
84 typename AllocatorTy = MallocAllocator>
85 class ScopedHashTableScope {
86 /// HT - The hashtable that we are active for.
87 ScopedHashTable<K, V, KInfo, AllocatorTy> &HT;
88
89 /// PrevScope - This is the scope that we are shadowing in HT.
90 ScopedHashTableScope *PrevScope;
91
92 /// LastValInScope - This is the last value that was inserted for this scope
93 /// or null if none have been inserted yet.
94 ScopedHashTableVal<K, V> *LastValInScope;
95
96 public:
97 ScopedHashTableScope(ScopedHashTable<K, V, KInfo, AllocatorTy> &HT);
98 ScopedHashTableScope(ScopedHashTableScope &) = delete;
99 ScopedHashTableScope &operator=(ScopedHashTableScope &) = delete;
100 ~ScopedHashTableScope();
101
getParentScope()102 ScopedHashTableScope *getParentScope() { return PrevScope; }
getParentScope()103 const ScopedHashTableScope *getParentScope() const { return PrevScope; }
104
105 private:
106 friend class ScopedHashTable<K, V, KInfo, AllocatorTy>;
107
getLastValInScope()108 ScopedHashTableVal<K, V> *getLastValInScope() {
109 return LastValInScope;
110 }
111
setLastValInScope(ScopedHashTableVal<K,V> * Val)112 void setLastValInScope(ScopedHashTableVal<K, V> *Val) {
113 LastValInScope = Val;
114 }
115 };
116
117 template <typename K, typename V, typename KInfo = DenseMapInfo<K>>
118 class ScopedHashTableIterator {
119 ScopedHashTableVal<K, V> *Node;
120
121 public:
ScopedHashTableIterator(ScopedHashTableVal<K,V> * node)122 ScopedHashTableIterator(ScopedHashTableVal<K, V> *node) : Node(node) {}
123
124 V &operator*() const {
125 assert(Node && "Dereference end()");
126 return Node->getValue();
127 }
128 V *operator->() const {
129 return &Node->getValue();
130 }
131
132 bool operator==(const ScopedHashTableIterator &RHS) const {
133 return Node == RHS.Node;
134 }
135 bool operator!=(const ScopedHashTableIterator &RHS) const {
136 return Node != RHS.Node;
137 }
138
139 inline ScopedHashTableIterator& operator++() { // Preincrement
140 assert(Node && "incrementing past end()");
141 Node = Node->getNextForKey();
142 return *this;
143 }
144 ScopedHashTableIterator operator++(int) { // Postincrement
145 ScopedHashTableIterator tmp = *this; ++*this; return tmp;
146 }
147 };
148
149 template <typename K, typename V, typename KInfo, typename AllocatorTy>
150 class ScopedHashTable : detail::AllocatorHolder<AllocatorTy> {
151 using AllocTy = detail::AllocatorHolder<AllocatorTy>;
152
153 public:
154 /// ScopeTy - This is a helpful typedef that allows clients to get easy access
155 /// to the name of the scope for this hash table.
156 using ScopeTy = ScopedHashTableScope<K, V, KInfo, AllocatorTy>;
157 using size_type = unsigned;
158
159 private:
160 friend class ScopedHashTableScope<K, V, KInfo, AllocatorTy>;
161
162 using ValTy = ScopedHashTableVal<K, V>;
163
164 DenseMap<K, ValTy*, KInfo> TopLevelMap;
165 ScopeTy *CurScope = nullptr;
166
167 public:
168 ScopedHashTable() = default;
ScopedHashTable(AllocatorTy A)169 ScopedHashTable(AllocatorTy A) : AllocTy(A) {}
170 ScopedHashTable(const ScopedHashTable &) = delete;
171 ScopedHashTable &operator=(const ScopedHashTable &) = delete;
172
~ScopedHashTable()173 ~ScopedHashTable() {
174 assert(!CurScope && TopLevelMap.empty() && "Scope imbalance!");
175 }
176
177 /// Access to the allocator.
178 using AllocTy::getAllocator;
179
180 /// Return 1 if the specified key is in the table, 0 otherwise.
count(const K & Key)181 size_type count(const K &Key) const {
182 return TopLevelMap.count(Key);
183 }
184
lookup(const K & Key)185 V lookup(const K &Key) const {
186 auto I = TopLevelMap.find(Key);
187 if (I != TopLevelMap.end())
188 return I->second->getValue();
189
190 return V();
191 }
192
insert(const K & Key,const V & Val)193 void insert(const K &Key, const V &Val) {
194 insertIntoScope(CurScope, Key, Val);
195 }
196
197 using iterator = ScopedHashTableIterator<K, V, KInfo>;
198
end()199 iterator end() { return iterator(nullptr); }
200
begin(const K & Key)201 iterator begin(const K &Key) {
202 typename DenseMap<K, ValTy*, KInfo>::iterator I =
203 TopLevelMap.find(Key);
204 if (I == TopLevelMap.end()) return end();
205 return iterator(I->second);
206 }
207
getCurScope()208 ScopeTy *getCurScope() { return CurScope; }
getCurScope()209 const ScopeTy *getCurScope() const { return CurScope; }
210
211 /// insertIntoScope - This inserts the specified key/value at the specified
212 /// (possibly not the current) scope. While it is ok to insert into a scope
213 /// that isn't the current one, it isn't ok to insert *underneath* an existing
214 /// value of the specified key.
insertIntoScope(ScopeTy * S,const K & Key,const V & Val)215 void insertIntoScope(ScopeTy *S, const K &Key, const V &Val) {
216 assert(S && "No scope active!");
217 ScopedHashTableVal<K, V> *&KeyEntry = TopLevelMap[Key];
218 KeyEntry = ValTy::Create(S->getLastValInScope(), KeyEntry, Key, Val,
219 getAllocator());
220 S->setLastValInScope(KeyEntry);
221 }
222 };
223
224 /// ScopedHashTableScope ctor - Install this as the current scope for the hash
225 /// table.
226 template <typename K, typename V, typename KInfo, typename Allocator>
227 ScopedHashTableScope<K, V, KInfo, Allocator>::
ScopedHashTableScope(ScopedHashTable<K,V,KInfo,Allocator> & ht)228 ScopedHashTableScope(ScopedHashTable<K, V, KInfo, Allocator> &ht) : HT(ht) {
229 PrevScope = HT.CurScope;
230 HT.CurScope = this;
231 LastValInScope = nullptr;
232 }
233
234 template <typename K, typename V, typename KInfo, typename Allocator>
~ScopedHashTableScope()235 ScopedHashTableScope<K, V, KInfo, Allocator>::~ScopedHashTableScope() {
236 assert(HT.CurScope == this && "Scope imbalance!");
237 HT.CurScope = PrevScope;
238
239 // Pop and delete all values corresponding to this scope.
240 while (ScopedHashTableVal<K, V> *ThisEntry = LastValInScope) {
241 // Pop this value out of the TopLevelMap.
242 if (!ThisEntry->getNextForKey()) {
243 assert(HT.TopLevelMap[ThisEntry->getKey()] == ThisEntry &&
244 "Scope imbalance!");
245 HT.TopLevelMap.erase(ThisEntry->getKey());
246 } else {
247 ScopedHashTableVal<K, V> *&KeyEntry = HT.TopLevelMap[ThisEntry->getKey()];
248 assert(KeyEntry == ThisEntry && "Scope imbalance!");
249 KeyEntry = ThisEntry->getNextForKey();
250 }
251
252 // Pop this value out of the scope.
253 LastValInScope = ThisEntry->getNextInScope();
254
255 // Delete this entry.
256 ThisEntry->Destroy(HT.getAllocator());
257 }
258 }
259
260 } // end namespace llvm
261
262 #endif // LLVM_ADT_SCOPEDHASHTABLE_H
263