1 //===- ScopedHashTable.h - A simple scoped hash table ---------------------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
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
14 // ScopedHashTable<int, int> HT;
16 // ScopedHashTableScope<int, int> Scope1(HT);
20 // ScopedHashTableScope<int, int> Scope2(HT);
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
29 //===----------------------------------------------------------------------===//
31 #ifndef LLVM_ADT_SCOPEDHASHTABLE_H
32 #define LLVM_ADT_SCOPEDHASHTABLE_H
35 #include "llvm/ADT/DenseMap.h"
39 template <typename K, typename V, typename KInfo = DenseMapInfo<K> >
40 class ScopedHashTable;
42 template <typename K, typename V, typename KInfo = DenseMapInfo<K> >
43 class ScopedHashTableVal {
44 ScopedHashTableVal *NextInScope;
45 ScopedHashTableVal *NextForKey;
49 ScopedHashTableVal(ScopedHashTableVal *nextInScope,
50 ScopedHashTableVal *nextForKey, const K &key, const V &val)
51 : NextInScope(nextInScope), NextForKey(nextForKey), Key(key), Val(val) {
54 const K &getKey() const { return Key; }
55 const V &getValue() const { return Val; }
56 V &getValue() { return Val; }
58 ScopedHashTableVal *getNextForKey() { return NextForKey; }
59 const ScopedHashTableVal *getNextForKey() const { return NextForKey; }
61 ScopedHashTableVal *getNextInScope() { return NextInScope; }
64 template <typename K, typename V, typename KInfo = DenseMapInfo<K> >
65 class ScopedHashTableScope {
66 /// HT - The hashtable that we are active for.
67 ScopedHashTable<K, V, KInfo> &HT;
69 /// PrevScope - This is the scope that we are shadowing in HT.
70 ScopedHashTableScope *PrevScope;
72 /// LastValInScope - This is the last value that was inserted for this scope
73 /// or null if none have been inserted yet.
74 ScopedHashTableVal<K, V, KInfo> *LastValInScope;
75 void operator=(ScopedHashTableScope&); // DO NOT IMPLEMENT
76 ScopedHashTableScope(ScopedHashTableScope&); // DO NOT IMPLEMENT
78 ScopedHashTableScope(ScopedHashTable<K, V, KInfo> &HT);
79 ~ScopedHashTableScope();
82 friend class ScopedHashTable<K, V, KInfo>;
83 ScopedHashTableVal<K, V, KInfo> *getLastValInScope() {
84 return LastValInScope;
86 void setLastValInScope(ScopedHashTableVal<K, V, KInfo> *Val) {
92 template <typename K, typename V, typename KInfo = DenseMapInfo<K> >
93 class ScopedHashTableIterator {
94 ScopedHashTableVal<K, V, KInfo> *Node;
96 ScopedHashTableIterator(ScopedHashTableVal<K, V, KInfo> *node) : Node(node) {}
98 V &operator*() const {
99 assert(Node && "Dereference end()");
100 return Node->getValue();
102 V *operator->() const {
103 return &Node->getValue();
106 bool operator==(const ScopedHashTableIterator &RHS) const {
107 return Node == RHS.Node;
109 bool operator!=(const ScopedHashTableIterator &RHS) const {
110 return Node != RHS.Node;
113 inline ScopedHashTableIterator& operator++() { // Preincrement
114 assert(Node && "incrementing past end()");
115 Node = Node->getNextForKey();
118 ScopedHashTableIterator operator++(int) { // Postincrement
119 ScopedHashTableIterator tmp = *this; ++*this; return tmp;
124 template <typename K, typename V, typename KInfo>
125 class ScopedHashTable {
126 DenseMap<K, ScopedHashTableVal<K, V, KInfo>*, KInfo> TopLevelMap;
127 ScopedHashTableScope<K, V, KInfo> *CurScope;
128 ScopedHashTable(const ScopedHashTable&); // NOT YET IMPLEMENTED
129 void operator=(const ScopedHashTable&); // NOT YET IMPLEMENTED
130 friend class ScopedHashTableScope<K, V, KInfo>;
132 ScopedHashTable() : CurScope(0) {}
134 assert(CurScope == 0 && TopLevelMap.empty() && "Scope imbalance!");
137 bool count(const K &Key) const {
138 return TopLevelMap.count(Key);
141 V lookup(const K &Key) {
142 typename DenseMap<K, ScopedHashTableVal<K, V, KInfo>*, KInfo>::iterator
143 I = TopLevelMap.find(Key);
144 if (I != TopLevelMap.end())
145 return I->second->getValue();
150 void insert(const K &Key, const V &Val) {
151 assert(CurScope && "No scope active!");
153 ScopedHashTableVal<K, V, KInfo> *&KeyEntry = TopLevelMap[Key];
155 KeyEntry= new ScopedHashTableVal<K, V, KInfo>(CurScope->getLastValInScope(),
157 CurScope->setLastValInScope(KeyEntry);
160 typedef ScopedHashTableIterator<K, V, KInfo> iterator;
162 iterator end() { return iterator(0); }
164 iterator begin(const K &Key) {
165 typename DenseMap<K, ScopedHashTableVal<K, V, KInfo>*, KInfo>::iterator I =
166 TopLevelMap.find(Key);
167 if (I == TopLevelMap.end()) return end();
168 return iterator(I->second);
172 /// ScopedHashTableScope ctor - Install this as the current scope for the hash
174 template <typename K, typename V, typename KInfo>
175 ScopedHashTableScope<K, V, KInfo>::
176 ScopedHashTableScope(ScopedHashTable<K, V, KInfo> &ht) : HT(ht) {
177 PrevScope = HT.CurScope;
182 template <typename K, typename V, typename KInfo>
183 ScopedHashTableScope<K, V, KInfo>::~ScopedHashTableScope() {
184 assert(HT.CurScope == this && "Scope imbalance!");
185 HT.CurScope = PrevScope;
187 // Pop and delete all values corresponding to this scope.
188 while (ScopedHashTableVal<K, V, KInfo> *ThisEntry = LastValInScope) {
189 // Pop this value out of the TopLevelMap.
190 if (ThisEntry->getNextForKey() == 0) {
191 assert(HT.TopLevelMap[ThisEntry->getKey()] == ThisEntry &&
193 HT.TopLevelMap.erase(ThisEntry->getKey());
195 ScopedHashTableVal<K, V, KInfo> *&KeyEntry =
196 HT.TopLevelMap[ThisEntry->getKey()];
197 assert(KeyEntry == ThisEntry && "Scope imbalance!");
198 KeyEntry = ThisEntry->getNextForKey();
201 // Pop this value out of the scope.
202 LastValInScope = ThisEntry->getNextInScope();
204 // Delete this entry.
209 } // end namespace llvm