1 //===- ScopedHashTable.h - A simple scoped hash table ---------------------===//
2 //
3 // The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 // This file implements an efficient scoped hash table, which is useful for
11 // things like dominator-based optimizations. This allows clients to do things
12 // like this:
13 //
14 // ScopedHashTable<int, int> HT;
15 // {
16 // ScopedHashTableScope<int, int> Scope1(HT);
17 // HT.insert(0, 0);
18 // HT.insert(1, 1);
19 // {
20 // ScopedHashTableScope<int, int> Scope2(HT);
21 // HT.insert(0, 42);
22 // }
23 // }
24 //
25 // Looking up the value for "0" in the Scope2 block will return 42. Looking
26 // up the value for 0 before 42 is inserted or after Scope2 is popped will
27 // return 0.
28 //
29 //===----------------------------------------------------------------------===//
30
31 #ifndef LLVM_ADT_SCOPEDHASHTABLE_H
32 #define LLVM_ADT_SCOPEDHASHTABLE_H
33
34 #include "llvm/ADT/DenseMap.h"
35 #include "llvm/Support/Allocator.h"
36
37 namespace llvm {
38
39 template <typename K, typename V, typename KInfo = DenseMapInfo<K>,
40 typename AllocatorTy = MallocAllocator>
41 class ScopedHashTable;
42
43 template <typename K, typename V>
44 class ScopedHashTableVal {
45 ScopedHashTableVal *NextInScope;
46 ScopedHashTableVal *NextForKey;
47 K Key;
48 V Val;
ScopedHashTableVal(const K & key,const V & val)49 ScopedHashTableVal(const K &key, const V &val) : Key(key), Val(val) {}
50 public:
51
getKey()52 const K &getKey() const { return Key; }
getValue()53 const V &getValue() const { return Val; }
getValue()54 V &getValue() { return Val; }
55
getNextForKey()56 ScopedHashTableVal *getNextForKey() { return NextForKey; }
getNextForKey()57 const ScopedHashTableVal *getNextForKey() const { return NextForKey; }
getNextInScope()58 ScopedHashTableVal *getNextInScope() { return NextInScope; }
59
60 template <typename AllocatorTy>
Create(ScopedHashTableVal * nextInScope,ScopedHashTableVal * nextForKey,const K & key,const V & val,AllocatorTy & Allocator)61 static ScopedHashTableVal *Create(ScopedHashTableVal *nextInScope,
62 ScopedHashTableVal *nextForKey,
63 const K &key, const V &val,
64 AllocatorTy &Allocator) {
65 ScopedHashTableVal *New = Allocator.template Allocate<ScopedHashTableVal>();
66 // Set up the value.
67 new (New) ScopedHashTableVal(key, val);
68 New->NextInScope = nextInScope;
69 New->NextForKey = nextForKey;
70 return New;
71 }
72
73 template <typename AllocatorTy>
Destroy(AllocatorTy & Allocator)74 void Destroy(AllocatorTy &Allocator) {
75 // Free memory referenced by the item.
76 this->~ScopedHashTableVal();
77 Allocator.Deallocate(this);
78 }
79 };
80
81 template <typename K, typename V, typename KInfo = DenseMapInfo<K>,
82 typename AllocatorTy = MallocAllocator>
83 class ScopedHashTableScope {
84 /// HT - The hashtable that we are active for.
85 ScopedHashTable<K, V, KInfo, AllocatorTy> &HT;
86
87 /// PrevScope - This is the scope that we are shadowing in HT.
88 ScopedHashTableScope *PrevScope;
89
90 /// LastValInScope - This is the last value that was inserted for this scope
91 /// or null if none have been inserted yet.
92 ScopedHashTableVal<K, V> *LastValInScope;
93 void operator=(ScopedHashTableScope&) = delete;
94 ScopedHashTableScope(ScopedHashTableScope&) = delete;
95 public:
96 ScopedHashTableScope(ScopedHashTable<K, V, KInfo, AllocatorTy> &HT);
97 ~ScopedHashTableScope();
98
getParentScope()99 ScopedHashTableScope *getParentScope() { return PrevScope; }
getParentScope()100 const ScopedHashTableScope *getParentScope() const { return PrevScope; }
101
102 private:
103 friend class ScopedHashTable<K, V, KInfo, AllocatorTy>;
getLastValInScope()104 ScopedHashTableVal<K, V> *getLastValInScope() {
105 return LastValInScope;
106 }
setLastValInScope(ScopedHashTableVal<K,V> * Val)107 void setLastValInScope(ScopedHashTableVal<K, V> *Val) {
108 LastValInScope = Val;
109 }
110 };
111
112
113 template <typename K, typename V, typename KInfo = DenseMapInfo<K> >
114 class ScopedHashTableIterator {
115 ScopedHashTableVal<K, V> *Node;
116 public:
ScopedHashTableIterator(ScopedHashTableVal<K,V> * node)117 ScopedHashTableIterator(ScopedHashTableVal<K, V> *node) : Node(node) {}
118
119 V &operator*() const {
120 assert(Node && "Dereference end()");
121 return Node->getValue();
122 }
123 V *operator->() const {
124 return &Node->getValue();
125 }
126
127 bool operator==(const ScopedHashTableIterator &RHS) const {
128 return Node == RHS.Node;
129 }
130 bool operator!=(const ScopedHashTableIterator &RHS) const {
131 return Node != RHS.Node;
132 }
133
134 inline ScopedHashTableIterator& operator++() { // Preincrement
135 assert(Node && "incrementing past end()");
136 Node = Node->getNextForKey();
137 return *this;
138 }
139 ScopedHashTableIterator operator++(int) { // Postincrement
140 ScopedHashTableIterator tmp = *this; ++*this; return tmp;
141 }
142 };
143
144
145 template <typename K, typename V, typename KInfo, typename AllocatorTy>
146 class ScopedHashTable {
147 public:
148 /// ScopeTy - This is a helpful typedef that allows clients to get easy access
149 /// to the name of the scope for this hash table.
150 typedef ScopedHashTableScope<K, V, KInfo, AllocatorTy> ScopeTy;
151 typedef unsigned size_type;
152 private:
153 typedef ScopedHashTableVal<K, V> ValTy;
154 DenseMap<K, ValTy*, KInfo> TopLevelMap;
155 ScopeTy *CurScope;
156
157 AllocatorTy Allocator;
158
159 ScopedHashTable(const ScopedHashTable&); // NOT YET IMPLEMENTED
160 void operator=(const ScopedHashTable&); // NOT YET IMPLEMENTED
161 friend class ScopedHashTableScope<K, V, KInfo, AllocatorTy>;
162 public:
ScopedHashTable()163 ScopedHashTable() : CurScope(nullptr) {}
ScopedHashTable(AllocatorTy A)164 ScopedHashTable(AllocatorTy A) : CurScope(0), Allocator(A) {}
~ScopedHashTable()165 ~ScopedHashTable() {
166 assert(!CurScope && TopLevelMap.empty() && "Scope imbalance!");
167 }
168
169
170 /// Access to the allocator.
getAllocator()171 AllocatorTy &getAllocator() { return Allocator; }
getAllocator()172 const AllocatorTy &getAllocator() const { return Allocator; }
173
174 /// Return 1 if the specified key is in the table, 0 otherwise.
count(const K & Key)175 size_type count(const K &Key) const {
176 return TopLevelMap.count(Key);
177 }
178
lookup(const K & Key)179 V lookup(const K &Key) {
180 typename DenseMap<K, ValTy*, KInfo>::iterator I = TopLevelMap.find(Key);
181 if (I != TopLevelMap.end())
182 return I->second->getValue();
183
184 return V();
185 }
186
insert(const K & Key,const V & Val)187 void insert(const K &Key, const V &Val) {
188 insertIntoScope(CurScope, Key, Val);
189 }
190
191 typedef ScopedHashTableIterator<K, V, KInfo> iterator;
192
end()193 iterator end() { return iterator(0); }
194
begin(const K & Key)195 iterator begin(const K &Key) {
196 typename DenseMap<K, ValTy*, KInfo>::iterator I =
197 TopLevelMap.find(Key);
198 if (I == TopLevelMap.end()) return end();
199 return iterator(I->second);
200 }
201
getCurScope()202 ScopeTy *getCurScope() { return CurScope; }
getCurScope()203 const ScopeTy *getCurScope() const { return CurScope; }
204
205 /// insertIntoScope - This inserts the specified key/value at the specified
206 /// (possibly not the current) scope. While it is ok to insert into a scope
207 /// that isn't the current one, it isn't ok to insert *underneath* an existing
208 /// value of the specified key.
insertIntoScope(ScopeTy * S,const K & Key,const V & Val)209 void insertIntoScope(ScopeTy *S, const K &Key, const V &Val) {
210 assert(S && "No scope active!");
211 ScopedHashTableVal<K, V> *&KeyEntry = TopLevelMap[Key];
212 KeyEntry = ValTy::Create(S->getLastValInScope(), KeyEntry, Key, Val,
213 Allocator);
214 S->setLastValInScope(KeyEntry);
215 }
216 };
217
218 /// ScopedHashTableScope ctor - Install this as the current scope for the hash
219 /// table.
220 template <typename K, typename V, typename KInfo, typename Allocator>
221 ScopedHashTableScope<K, V, KInfo, Allocator>::
ScopedHashTableScope(ScopedHashTable<K,V,KInfo,Allocator> & ht)222 ScopedHashTableScope(ScopedHashTable<K, V, KInfo, Allocator> &ht) : HT(ht) {
223 PrevScope = HT.CurScope;
224 HT.CurScope = this;
225 LastValInScope = nullptr;
226 }
227
228 template <typename K, typename V, typename KInfo, typename Allocator>
~ScopedHashTableScope()229 ScopedHashTableScope<K, V, KInfo, Allocator>::~ScopedHashTableScope() {
230 assert(HT.CurScope == this && "Scope imbalance!");
231 HT.CurScope = PrevScope;
232
233 // Pop and delete all values corresponding to this scope.
234 while (ScopedHashTableVal<K, V> *ThisEntry = LastValInScope) {
235 // Pop this value out of the TopLevelMap.
236 if (!ThisEntry->getNextForKey()) {
237 assert(HT.TopLevelMap[ThisEntry->getKey()] == ThisEntry &&
238 "Scope imbalance!");
239 HT.TopLevelMap.erase(ThisEntry->getKey());
240 } else {
241 ScopedHashTableVal<K, V> *&KeyEntry = HT.TopLevelMap[ThisEntry->getKey()];
242 assert(KeyEntry == ThisEntry && "Scope imbalance!");
243 KeyEntry = ThisEntry->getNextForKey();
244 }
245
246 // Pop this value out of the scope.
247 LastValInScope = ThisEntry->getNextInScope();
248
249 // Delete this entry.
250 ThisEntry->Destroy(HT.getAllocator());
251 }
252 }
253
254 } // end namespace llvm
255
256 #endif
257