ScopedHashTable.h revision 321369 
1//===- ScopedHashTable.h - A simple scoped hash table -----------*- C++ -*-===//
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/ADT/DenseMapInfo.h"
36#include "llvm/Support/Allocator.h"
37#include <cassert>
38#include <new>
39
40namespace llvm {
41
42template <typename K, typename V, typename KInfo = DenseMapInfo<K>,
43          typename AllocatorTy = MallocAllocator>
44class ScopedHashTable;
45
46template <typename K, typename V>
47class ScopedHashTableVal {
48  ScopedHashTableVal *NextInScope;
49  ScopedHashTableVal *NextForKey;
50  K Key;
51  V Val;
52
53  ScopedHashTableVal(const K &key, const V &val) : Key(key), Val(val) {}
54
55public:
56  const K &getKey() const { return Key; }
57  const V &getValue() const { return Val; }
58  V &getValue() { return Val; }
59
60  ScopedHashTableVal *getNextForKey() { return NextForKey; }
61  const ScopedHashTableVal *getNextForKey() const { return NextForKey; }
62  ScopedHashTableVal *getNextInScope() { return NextInScope; }
63
64  template <typename AllocatorTy>
65  static ScopedHashTableVal *Create(ScopedHashTableVal *nextInScope,
66                                    ScopedHashTableVal *nextForKey,
67                                    const K &key, const V &val,
68                                    AllocatorTy &Allocator) {
69    ScopedHashTableVal *New = Allocator.template Allocate<ScopedHashTableVal>();
70    // Set up the value.
71    new (New) ScopedHashTableVal(key, val);
72    New->NextInScope = nextInScope;
73    New->NextForKey = nextForKey;
74    return New;
75  }
76
77  template <typename AllocatorTy> void Destroy(AllocatorTy &Allocator) {
78    // Free memory referenced by the item.
79    this->~ScopedHashTableVal();
80    Allocator.Deallocate(this);
81  }
82};
83
84template <typename K, typename V, typename KInfo = DenseMapInfo<K>,
85          typename AllocatorTy = MallocAllocator>
86class ScopedHashTableScope {
87  /// HT - The hashtable that we are active for.
88  ScopedHashTable<K, V, KInfo, AllocatorTy> &HT;
89
90  /// PrevScope - This is the scope that we are shadowing in HT.
91  ScopedHashTableScope *PrevScope;
92
93  /// LastValInScope - This is the last value that was inserted for this scope
94  /// or null if none have been inserted yet.
95  ScopedHashTableVal<K, V> *LastValInScope;
96
97public:
98  ScopedHashTableScope(ScopedHashTable<K, V, KInfo, AllocatorTy> &HT);
99  ScopedHashTableScope(ScopedHashTableScope &) = delete;
100  ScopedHashTableScope &operator=(ScopedHashTableScope &) = delete;
101  ~ScopedHashTableScope();
102
103  ScopedHashTableScope *getParentScope() { return PrevScope; }
104  const ScopedHashTableScope *getParentScope() const { return PrevScope; }
105
106private:
107  friend class ScopedHashTable<K, V, KInfo, AllocatorTy>;
108
109  ScopedHashTableVal<K, V> *getLastValInScope() {
110    return LastValInScope;
111  }
112
113  void setLastValInScope(ScopedHashTableVal<K, V> *Val) {
114    LastValInScope = Val;
115  }
116};
117
118template <typename K, typename V, typename KInfo = DenseMapInfo<K>>
119class ScopedHashTableIterator {
120  ScopedHashTableVal<K, V> *Node;
121
122public:
123  ScopedHashTableIterator(ScopedHashTableVal<K, V> *node) : Node(node) {}
124
125  V &operator*() const {
126    assert(Node && "Dereference end()");
127    return Node->getValue();
128  }
129  V *operator->() const {
130    return &Node->getValue();
131  }
132
133  bool operator==(const ScopedHashTableIterator &RHS) const {
134    return Node == RHS.Node;
135  }
136  bool operator!=(const ScopedHashTableIterator &RHS) const {
137    return Node != RHS.Node;
138  }
139
140  inline ScopedHashTableIterator& operator++() {          // Preincrement
141    assert(Node && "incrementing past end()");
142    Node = Node->getNextForKey();
143    return *this;
144  }
145  ScopedHashTableIterator operator++(int) {        // Postincrement
146    ScopedHashTableIterator tmp = *this; ++*this; return tmp;
147  }
148};
149
150template <typename K, typename V, typename KInfo, typename AllocatorTy>
151class ScopedHashTable {
152public:
153  /// ScopeTy - This is a helpful typedef that allows clients to get easy access
154  /// to the name of the scope for this hash table.
155  using ScopeTy = ScopedHashTableScope<K, V, KInfo, AllocatorTy>;
156  using size_type = unsigned;
157
158private:
159  friend class ScopedHashTableScope<K, V, KInfo, AllocatorTy>;
160
161  using ValTy = ScopedHashTableVal<K, V>;
162
163  DenseMap<K, ValTy*, KInfo> TopLevelMap;
164  ScopeTy *CurScope = nullptr;
165
166  AllocatorTy Allocator;
167
168public:
169  ScopedHashTable() = default;
170  ScopedHashTable(AllocatorTy A) : Allocator(A) {}
171  ScopedHashTable(const ScopedHashTable &) = delete;
172  ScopedHashTable &operator=(const ScopedHashTable &) = delete;
173
174  ~ScopedHashTable() {
175    assert(!CurScope && TopLevelMap.empty() && "Scope imbalance!");
176  }
177
178  /// Access to the allocator.
179  AllocatorTy &getAllocator() { return Allocator; }
180  const AllocatorTy &getAllocator() const { return Allocator; }
181
182  /// Return 1 if the specified key is in the table, 0 otherwise.
183  size_type count(const K &Key) const {
184    return TopLevelMap.count(Key);
185  }
186
187  V lookup(const K &Key) const {
188    auto I = TopLevelMap.find(Key);
189    if (I != TopLevelMap.end())
190      return I->second->getValue();
191
192    return V();
193  }
194
195  void insert(const K &Key, const V &Val) {
196    insertIntoScope(CurScope, Key, Val);
197  }
198
199  using iterator = ScopedHashTableIterator<K, V, KInfo>;
200
201  iterator end() { return iterator(0); }
202
203  iterator begin(const K &Key) {
204    typename DenseMap<K, ValTy*, KInfo>::iterator I =
205      TopLevelMap.find(Key);
206    if (I == TopLevelMap.end()) return end();
207    return iterator(I->second);
208  }
209
210  ScopeTy *getCurScope() { return CurScope; }
211  const ScopeTy *getCurScope() const { return CurScope; }
212
213  /// insertIntoScope - This inserts the specified key/value at the specified
214  /// (possibly not the current) scope.  While it is ok to insert into a scope
215  /// that isn't the current one, it isn't ok to insert *underneath* an existing
216  /// value of the specified key.
217  void insertIntoScope(ScopeTy *S, const K &Key, const V &Val) {
218    assert(S && "No scope active!");
219    ScopedHashTableVal<K, V> *&KeyEntry = TopLevelMap[Key];
220    KeyEntry = ValTy::Create(S->getLastValInScope(), KeyEntry, Key, Val,
221                             Allocator);
222    S->setLastValInScope(KeyEntry);
223  }
224};
225
226/// ScopedHashTableScope ctor - Install this as the current scope for the hash
227/// table.
228template <typename K, typename V, typename KInfo, typename Allocator>
229ScopedHashTableScope<K, V, KInfo, Allocator>::
230  ScopedHashTableScope(ScopedHashTable<K, V, KInfo, Allocator> &ht) : HT(ht) {
231  PrevScope = HT.CurScope;
232  HT.CurScope = this;
233  LastValInScope = nullptr;
234}
235
236template <typename K, typename V, typename KInfo, typename Allocator>
237ScopedHashTableScope<K, V, KInfo, Allocator>::~ScopedHashTableScope() {
238  assert(HT.CurScope == this && "Scope imbalance!");
239  HT.CurScope = PrevScope;
240
241  // Pop and delete all values corresponding to this scope.
242  while (ScopedHashTableVal<K, V> *ThisEntry = LastValInScope) {
243    // Pop this value out of the TopLevelMap.
244    if (!ThisEntry->getNextForKey()) {
245      assert(HT.TopLevelMap[ThisEntry->getKey()] == ThisEntry &&
246             "Scope imbalance!");
247      HT.TopLevelMap.erase(ThisEntry->getKey());
248    } else {
249      ScopedHashTableVal<K, V> *&KeyEntry = HT.TopLevelMap[ThisEntry->getKey()];
250      assert(KeyEntry == ThisEntry && "Scope imbalance!");
251      KeyEntry = ThisEntry->getNextForKey();
252    }
253
254    // Pop this value out of the scope.
255    LastValInScope = ThisEntry->getNextInScope();
256
257    // Delete this entry.
258    ThisEntry->Destroy(HT.getAllocator());
259  }
260}
261
262} // end namespace llvm
263
264#endif // LLVM_ADT_SCOPEDHASHTABLE_H
265