ScopedHashTable.h revision 204792 
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 <cassert>
35#include "llvm/ADT/DenseMap.h"
36
37namespace llvm {
38
39template <typename K, typename V, typename KInfo = DenseMapInfo<K> >
40class ScopedHashTable;
41
42template <typename K, typename V, typename KInfo = DenseMapInfo<K> >
43class ScopedHashTableVal {
44  ScopedHashTableVal *NextInScope;
45  ScopedHashTableVal *NextForKey;
46  K Key;
47  V Val;
48public:
49  ScopedHashTableVal(ScopedHashTableVal *nextInScope,
50                     ScopedHashTableVal *nextForKey, const K &key, const V &val)
51    : NextInScope(nextInScope), NextForKey(nextForKey), Key(key), Val(val) {
52  }
53
54  const K &getKey() const { return Key; }
55  const V &getValue() const { return Val; }
56  V &getValue() { return Val; }
57
58  ScopedHashTableVal *getNextForKey() { return NextForKey; }
59  const ScopedHashTableVal *getNextForKey() const { return NextForKey; }
60public:
61  ScopedHashTableVal *getNextInScope() { return NextInScope; }
62};
63
64template <typename K, typename V, typename KInfo = DenseMapInfo<K> >
65class ScopedHashTableScope {
66  /// HT - The hashtable that we are active for.
67  ScopedHashTable<K, V, KInfo> &HT;
68
69  /// PrevScope - This is the scope that we are shadowing in HT.
70  ScopedHashTableScope *PrevScope;
71
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
77public:
78  ScopedHashTableScope(ScopedHashTable<K, V, KInfo> &HT);
79  ~ScopedHashTableScope();
80
81private:
82  friend class ScopedHashTable<K, V, KInfo>;
83  ScopedHashTableVal<K, V, KInfo> *getLastValInScope() {
84    return LastValInScope;
85  }
86  void setLastValInScope(ScopedHashTableVal<K, V, KInfo> *Val) {
87    LastValInScope = Val;
88  }
89};
90
91
92template <typename K, typename V, typename KInfo = DenseMapInfo<K> >
93class ScopedHashTableIterator {
94  ScopedHashTableVal<K, V, KInfo> *Node;
95public:
96  ScopedHashTableIterator(ScopedHashTableVal<K, V, KInfo> *node) : Node(node) {}
97
98  V &operator*() const {
99    assert(Node && "Dereference end()");
100    return Node->getValue();
101  }
102  V *operator->() const {
103    return &Node->getValue();
104  }
105
106  bool operator==(const ScopedHashTableIterator &RHS) const {
107    return Node == RHS.Node;
108  }
109  bool operator!=(const ScopedHashTableIterator &RHS) const {
110    return Node != RHS.Node;
111  }
112
113  inline ScopedHashTableIterator& operator++() {          // Preincrement
114    assert(Node && "incrementing past end()");
115    Node = Node->getNextForKey();
116    return *this;
117  }
118  ScopedHashTableIterator operator++(int) {        // Postincrement
119    ScopedHashTableIterator tmp = *this; ++*this; return tmp;
120  }
121};
122
123
124template <typename K, typename V, typename KInfo>
125class 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>;
131public:
132  ScopedHashTable() : CurScope(0) {}
133  ~ScopedHashTable() {
134    assert(CurScope == 0 && TopLevelMap.empty() && "Scope imbalance!");
135  }
136
137  bool count(const K &Key) const {
138    return TopLevelMap.count(Key);
139  }
140
141  V lookup(const K &Key) {
142    return TopLevelMap[Key]->getValue();
143  }
144
145  void insert(const K &Key, const V &Val) {
146    assert(CurScope && "No scope active!");
147
148    ScopedHashTableVal<K, V, KInfo> *&KeyEntry = TopLevelMap[Key];
149
150    KeyEntry= new ScopedHashTableVal<K, V, KInfo>(CurScope->getLastValInScope(),
151                                                  KeyEntry, Key, Val);
152    CurScope->setLastValInScope(KeyEntry);
153  }
154
155  typedef ScopedHashTableIterator<K, V, KInfo> iterator;
156
157  iterator end() { return iterator(0); }
158
159  iterator begin(const K &Key) {
160    typename DenseMap<K, ScopedHashTableVal<K, V, KInfo>*, KInfo>::iterator I =
161      TopLevelMap.find(Key);
162    if (I == TopLevelMap.end()) return end();
163    return iterator(I->second);
164  }
165};
166
167/// ScopedHashTableScope ctor - Install this as the current scope for the hash
168/// table.
169template <typename K, typename V, typename KInfo>
170ScopedHashTableScope<K, V, KInfo>::
171  ScopedHashTableScope(ScopedHashTable<K, V, KInfo> &ht) : HT(ht) {
172  PrevScope = HT.CurScope;
173  HT.CurScope = this;
174  LastValInScope = 0;
175}
176
177template <typename K, typename V, typename KInfo>
178ScopedHashTableScope<K, V, KInfo>::~ScopedHashTableScope() {
179  assert(HT.CurScope == this && "Scope imbalance!");
180  HT.CurScope = PrevScope;
181
182  // Pop and delete all values corresponding to this scope.
183  while (ScopedHashTableVal<K, V, KInfo> *ThisEntry = LastValInScope) {
184    // Pop this value out of the TopLevelMap.
185    if (ThisEntry->getNextForKey() == 0) {
186      assert(HT.TopLevelMap[ThisEntry->getKey()] == ThisEntry &&
187             "Scope imbalance!");
188      HT.TopLevelMap.erase(ThisEntry->getKey());
189    } else {
190      ScopedHashTableVal<K, V, KInfo> *&KeyEntry =
191        HT.TopLevelMap[ThisEntry->getKey()];
192      assert(KeyEntry == ThisEntry && "Scope imbalance!");
193      KeyEntry = ThisEntry->getNextForKey();
194    }
195
196    // Pop this value out of the scope.
197    LastValInScope = ThisEntry->getNextInScope();
198
199    // Delete this entry.
200    delete ThisEntry;
201  }
202}
203
204} // end namespace llvm
205
206#endif
207