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
37namespace llvm {
38
39template <typename K, typename V, typename KInfo = DenseMapInfo<K>,
40          typename AllocatorTy = MallocAllocator>
41class ScopedHashTable;
42
43template <typename K, typename V>
44class ScopedHashTableVal {
45  ScopedHashTableVal *NextInScope;
46  ScopedHashTableVal *NextForKey;
47  K Key;
48  V Val;
49  ScopedHashTableVal(const K &key, const V &val) : Key(key), Val(val) {}
50public:
51
52  const K &getKey() const { return Key; }
53  const V &getValue() const { return Val; }
54  V &getValue() { return Val; }
55
56  ScopedHashTableVal *getNextForKey() { return NextForKey; }
57  const ScopedHashTableVal *getNextForKey() const { return NextForKey; }
58  ScopedHashTableVal *getNextInScope() { return NextInScope; }
59
60  template <typename AllocatorTy>
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>
74  void Destroy(AllocatorTy &Allocator) {
75    // Free memory referenced by the item.
76    this->~ScopedHashTableVal();
77    Allocator.Deallocate(this);
78  }
79};
80
81template <typename K, typename V, typename KInfo = DenseMapInfo<K>,
82          typename AllocatorTy = MallocAllocator>
83class 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&) LLVM_DELETED_FUNCTION;
94  ScopedHashTableScope(ScopedHashTableScope&) LLVM_DELETED_FUNCTION;
95public:
96  ScopedHashTableScope(ScopedHashTable<K, V, KInfo, AllocatorTy> &HT);
97  ~ScopedHashTableScope();
98
99  ScopedHashTableScope *getParentScope() { return PrevScope; }
100  const ScopedHashTableScope *getParentScope() const { return PrevScope; }
101
102private:
103  friend class ScopedHashTable<K, V, KInfo, AllocatorTy>;
104  ScopedHashTableVal<K, V> *getLastValInScope() {
105    return LastValInScope;
106  }
107  void setLastValInScope(ScopedHashTableVal<K, V> *Val) {
108    LastValInScope = Val;
109  }
110};
111
112
113template <typename K, typename V, typename KInfo = DenseMapInfo<K> >
114class ScopedHashTableIterator {
115  ScopedHashTableVal<K, V> *Node;
116public:
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
145template <typename K, typename V, typename KInfo, typename AllocatorTy>
146class ScopedHashTable {
147public:
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;
152private:
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>;
162public:
163  ScopedHashTable() : CurScope(nullptr) {}
164  ScopedHashTable(AllocatorTy A) : CurScope(0), Allocator(A) {}
165  ~ScopedHashTable() {
166    assert(!CurScope && TopLevelMap.empty() && "Scope imbalance!");
167  }
168
169
170  /// Access to the allocator.
171  AllocatorTy &getAllocator() { return Allocator; }
172  const AllocatorTy &getAllocator() const { return Allocator; }
173
174  /// Return 1 if the specified key is in the table, 0 otherwise.
175  size_type count(const K &Key) const {
176    return TopLevelMap.count(Key);
177  }
178
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
187  void insert(const K &Key, const V &Val) {
188    insertIntoScope(CurScope, Key, Val);
189  }
190
191  typedef ScopedHashTableIterator<K, V, KInfo> iterator;
192
193  iterator end() { return iterator(0); }
194
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
202  ScopeTy *getCurScope() { return CurScope; }
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.
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.
220template <typename K, typename V, typename KInfo, typename Allocator>
221ScopedHashTableScope<K, V, KInfo, Allocator>::
222  ScopedHashTableScope(ScopedHashTable<K, V, KInfo, Allocator> &ht) : HT(ht) {
223  PrevScope = HT.CurScope;
224  HT.CurScope = this;
225  LastValInScope = nullptr;
226}
227
228template <typename K, typename V, typename KInfo, typename Allocator>
229ScopedHashTableScope<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