xref: /freebsd/contrib/llvm-project/llvm/include/llvm/ADT/ScopedHashTable.h (revision 924226fba12cc9a228c73b956e1b7fa24c60b055)
1 //===- ScopedHashTable.h - A simple scoped hash table -----------*- C++ -*-===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 //
9 // This file implements an efficient scoped hash table, which is useful for
10 // things like dominator-based optimizations.  This allows clients to do things
11 // like this:
12 //
13 //  ScopedHashTable<int, int> HT;
14 //  {
15 //    ScopedHashTableScope<int, int> Scope1(HT);
16 //    HT.insert(0, 0);
17 //    HT.insert(1, 1);
18 //    {
19 //      ScopedHashTableScope<int, int> Scope2(HT);
20 //      HT.insert(0, 42);
21 //    }
22 //  }
23 //
24 // Looking up the value for "0" in the Scope2 block will return 42.  Looking
25 // up the value for 0 before 42 is inserted or after Scope2 is popped will
26 // return 0.
27 //
28 //===----------------------------------------------------------------------===//
29 
30 #ifndef LLVM_ADT_SCOPEDHASHTABLE_H
31 #define LLVM_ADT_SCOPEDHASHTABLE_H
32 
33 #include "llvm/ADT/DenseMap.h"
34 #include "llvm/ADT/DenseMapInfo.h"
35 #include "llvm/Support/AllocatorBase.h"
36 #include <cassert>
37 #include <new>
38 
39 namespace llvm {
40 
41 template <typename K, typename V, typename KInfo = DenseMapInfo<K>,
42           typename AllocatorTy = MallocAllocator>
43 class ScopedHashTable;
44 
45 template <typename K, typename V>
46 class ScopedHashTableVal {
47   ScopedHashTableVal *NextInScope;
48   ScopedHashTableVal *NextForKey;
49   K Key;
50   V Val;
51 
52   ScopedHashTableVal(const K &key, const V &val) : Key(key), Val(val) {}
53 
54 public:
55   const K &getKey() const { return Key; }
56   const V &getValue() const { return Val; }
57   V &getValue() { return Val; }
58 
59   ScopedHashTableVal *getNextForKey() { return NextForKey; }
60   const ScopedHashTableVal *getNextForKey() const { return NextForKey; }
61   ScopedHashTableVal *getNextInScope() { return NextInScope; }
62 
63   template <typename AllocatorTy>
64   static ScopedHashTableVal *Create(ScopedHashTableVal *nextInScope,
65                                     ScopedHashTableVal *nextForKey,
66                                     const K &key, const V &val,
67                                     AllocatorTy &Allocator) {
68     ScopedHashTableVal *New = Allocator.template Allocate<ScopedHashTableVal>();
69     // Set up the value.
70     new (New) ScopedHashTableVal(key, val);
71     New->NextInScope = nextInScope;
72     New->NextForKey = nextForKey;
73     return New;
74   }
75 
76   template <typename AllocatorTy> void Destroy(AllocatorTy &Allocator) {
77     // Free memory referenced by the item.
78     this->~ScopedHashTableVal();
79     Allocator.Deallocate(this);
80   }
81 };
82 
83 template <typename K, typename V, typename KInfo = DenseMapInfo<K>,
84           typename AllocatorTy = MallocAllocator>
85 class ScopedHashTableScope {
86   /// HT - The hashtable that we are active for.
87   ScopedHashTable<K, V, KInfo, AllocatorTy> &HT;
88 
89   /// PrevScope - This is the scope that we are shadowing in HT.
90   ScopedHashTableScope *PrevScope;
91 
92   /// LastValInScope - This is the last value that was inserted for this scope
93   /// or null if none have been inserted yet.
94   ScopedHashTableVal<K, V> *LastValInScope;
95 
96 public:
97   ScopedHashTableScope(ScopedHashTable<K, V, KInfo, AllocatorTy> &HT);
98   ScopedHashTableScope(ScopedHashTableScope &) = delete;
99   ScopedHashTableScope &operator=(ScopedHashTableScope &) = delete;
100   ~ScopedHashTableScope();
101 
102   ScopedHashTableScope *getParentScope() { return PrevScope; }
103   const ScopedHashTableScope *getParentScope() const { return PrevScope; }
104 
105 private:
106   friend class ScopedHashTable<K, V, KInfo, AllocatorTy>;
107 
108   ScopedHashTableVal<K, V> *getLastValInScope() {
109     return LastValInScope;
110   }
111 
112   void setLastValInScope(ScopedHashTableVal<K, V> *Val) {
113     LastValInScope = Val;
114   }
115 };
116 
117 template <typename K, typename V, typename KInfo = DenseMapInfo<K>>
118 class ScopedHashTableIterator {
119   ScopedHashTableVal<K, V> *Node;
120 
121 public:
122   ScopedHashTableIterator(ScopedHashTableVal<K, V> *node) : Node(node) {}
123 
124   V &operator*() const {
125     assert(Node && "Dereference end()");
126     return Node->getValue();
127   }
128   V *operator->() const {
129     return &Node->getValue();
130   }
131 
132   bool operator==(const ScopedHashTableIterator &RHS) const {
133     return Node == RHS.Node;
134   }
135   bool operator!=(const ScopedHashTableIterator &RHS) const {
136     return Node != RHS.Node;
137   }
138 
139   inline ScopedHashTableIterator& operator++() {          // Preincrement
140     assert(Node && "incrementing past end()");
141     Node = Node->getNextForKey();
142     return *this;
143   }
144   ScopedHashTableIterator operator++(int) {        // Postincrement
145     ScopedHashTableIterator tmp = *this; ++*this; return tmp;
146   }
147 };
148 
149 template <typename K, typename V, typename KInfo, typename AllocatorTy>
150 class ScopedHashTable {
151 public:
152   /// ScopeTy - This is a helpful typedef that allows clients to get easy access
153   /// to the name of the scope for this hash table.
154   using ScopeTy = ScopedHashTableScope<K, V, KInfo, AllocatorTy>;
155   using size_type = unsigned;
156 
157 private:
158   friend class ScopedHashTableScope<K, V, KInfo, AllocatorTy>;
159 
160   using ValTy = ScopedHashTableVal<K, V>;
161 
162   DenseMap<K, ValTy*, KInfo> TopLevelMap;
163   ScopeTy *CurScope = nullptr;
164 
165   AllocatorTy Allocator;
166 
167 public:
168   ScopedHashTable() = default;
169   ScopedHashTable(AllocatorTy A) : Allocator(A) {}
170   ScopedHashTable(const ScopedHashTable &) = delete;
171   ScopedHashTable &operator=(const ScopedHashTable &) = delete;
172 
173   ~ScopedHashTable() {
174     assert(!CurScope && TopLevelMap.empty() && "Scope imbalance!");
175   }
176 
177   /// Access to the allocator.
178   AllocatorTy &getAllocator() { return Allocator; }
179   const AllocatorTy &getAllocator() const { return Allocator; }
180 
181   /// Return 1 if the specified key is in the table, 0 otherwise.
182   size_type count(const K &Key) const {
183     return TopLevelMap.count(Key);
184   }
185 
186   V lookup(const K &Key) const {
187     auto I = TopLevelMap.find(Key);
188     if (I != TopLevelMap.end())
189       return I->second->getValue();
190 
191     return V();
192   }
193 
194   void insert(const K &Key, const V &Val) {
195     insertIntoScope(CurScope, Key, Val);
196   }
197 
198   using iterator = ScopedHashTableIterator<K, V, KInfo>;
199 
200   iterator end() { return iterator(nullptr); }
201 
202   iterator begin(const K &Key) {
203     typename DenseMap<K, ValTy*, KInfo>::iterator I =
204       TopLevelMap.find(Key);
205     if (I == TopLevelMap.end()) return end();
206     return iterator(I->second);
207   }
208 
209   ScopeTy *getCurScope() { return CurScope; }
210   const ScopeTy *getCurScope() const { return CurScope; }
211 
212   /// insertIntoScope - This inserts the specified key/value at the specified
213   /// (possibly not the current) scope.  While it is ok to insert into a scope
214   /// that isn't the current one, it isn't ok to insert *underneath* an existing
215   /// value of the specified key.
216   void insertIntoScope(ScopeTy *S, const K &Key, const V &Val) {
217     assert(S && "No scope active!");
218     ScopedHashTableVal<K, V> *&KeyEntry = TopLevelMap[Key];
219     KeyEntry = ValTy::Create(S->getLastValInScope(), KeyEntry, Key, Val,
220                              Allocator);
221     S->setLastValInScope(KeyEntry);
222   }
223 };
224 
225 /// ScopedHashTableScope ctor - Install this as the current scope for the hash
226 /// table.
227 template <typename K, typename V, typename KInfo, typename Allocator>
228 ScopedHashTableScope<K, V, KInfo, Allocator>::
229   ScopedHashTableScope(ScopedHashTable<K, V, KInfo, Allocator> &ht) : HT(ht) {
230   PrevScope = HT.CurScope;
231   HT.CurScope = this;
232   LastValInScope = nullptr;
233 }
234 
235 template <typename K, typename V, typename KInfo, typename Allocator>
236 ScopedHashTableScope<K, V, KInfo, Allocator>::~ScopedHashTableScope() {
237   assert(HT.CurScope == this && "Scope imbalance!");
238   HT.CurScope = PrevScope;
239 
240   // Pop and delete all values corresponding to this scope.
241   while (ScopedHashTableVal<K, V> *ThisEntry = LastValInScope) {
242     // Pop this value out of the TopLevelMap.
243     if (!ThisEntry->getNextForKey()) {
244       assert(HT.TopLevelMap[ThisEntry->getKey()] == ThisEntry &&
245              "Scope imbalance!");
246       HT.TopLevelMap.erase(ThisEntry->getKey());
247     } else {
248       ScopedHashTableVal<K, V> *&KeyEntry = HT.TopLevelMap[ThisEntry->getKey()];
249       assert(KeyEntry == ThisEntry && "Scope imbalance!");
250       KeyEntry = ThisEntry->getNextForKey();
251     }
252 
253     // Pop this value out of the scope.
254     LastValInScope = ThisEntry->getNextInScope();
255 
256     // Delete this entry.
257     ThisEntry->Destroy(HT.getAllocator());
258   }
259 }
260 
261 } // end namespace llvm
262 
263 #endif // LLVM_ADT_SCOPEDHASHTABLE_H
264