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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 
37 namespace llvm {
38 
39 template <typename K, typename V, typename KInfo = DenseMapInfo<K>,
40           typename AllocatorTy = MallocAllocator>
41 class ScopedHashTable;
42 
43 template <typename K, typename V>
44 class ScopedHashTableVal {
45   ScopedHashTableVal *NextInScope;
46   ScopedHashTableVal *NextForKey;
47   K Key;
48   V Val;
ScopedHashTableVal(const K & key,const V & val)49   ScopedHashTableVal(const K &key, const V &val) : Key(key), Val(val) {}
50 public:
51 
getKey()52   const K &getKey() const { return Key; }
getValue()53   const V &getValue() const { return Val; }
getValue()54   V &getValue() { return Val; }
55 
getNextForKey()56   ScopedHashTableVal *getNextForKey() { return NextForKey; }
getNextForKey()57   const ScopedHashTableVal *getNextForKey() const { return NextForKey; }
getNextInScope()58   ScopedHashTableVal *getNextInScope() { return NextInScope; }
59 
60   template <typename AllocatorTy>
Create(ScopedHashTableVal * nextInScope,ScopedHashTableVal * nextForKey,const K & key,const V & val,AllocatorTy & Allocator)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>
Destroy(AllocatorTy & Allocator)74   void Destroy(AllocatorTy &Allocator) {
75     // Free memory referenced by the item.
76     this->~ScopedHashTableVal();
77     Allocator.Deallocate(this);
78   }
79 };
80 
81 template <typename K, typename V, typename KInfo = DenseMapInfo<K>,
82           typename AllocatorTy = MallocAllocator>
83 class 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&);       // DO NOT IMPLEMENT
94   ScopedHashTableScope(ScopedHashTableScope&); // DO NOT IMPLEMENT
95 public:
96   ScopedHashTableScope(ScopedHashTable<K, V, KInfo, AllocatorTy> &HT);
97   ~ScopedHashTableScope();
98 
getParentScope()99   ScopedHashTableScope *getParentScope() { return PrevScope; }
getParentScope()100   const ScopedHashTableScope *getParentScope() const { return PrevScope; }
101 
102 private:
103   friend class ScopedHashTable<K, V, KInfo, AllocatorTy>;
getLastValInScope()104   ScopedHashTableVal<K, V> *getLastValInScope() {
105     return LastValInScope;
106   }
setLastValInScope(ScopedHashTableVal<K,V> * Val)107   void setLastValInScope(ScopedHashTableVal<K, V> *Val) {
108     LastValInScope = Val;
109   }
110 };
111 
112 
113 template <typename K, typename V, typename KInfo = DenseMapInfo<K> >
114 class ScopedHashTableIterator {
115   ScopedHashTableVal<K, V> *Node;
116 public:
ScopedHashTableIterator(ScopedHashTableVal<K,V> * node)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 
145 template <typename K, typename V, typename KInfo, typename AllocatorTy>
146 class ScopedHashTable {
147 public:
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 private:
152   typedef ScopedHashTableVal<K, V> ValTy;
153   DenseMap<K, ValTy*, KInfo> TopLevelMap;
154   ScopeTy *CurScope;
155 
156   AllocatorTy Allocator;
157 
158   ScopedHashTable(const ScopedHashTable&); // NOT YET IMPLEMENTED
159   void operator=(const ScopedHashTable&);  // NOT YET IMPLEMENTED
160   friend class ScopedHashTableScope<K, V, KInfo, AllocatorTy>;
161 public:
ScopedHashTable()162   ScopedHashTable() : CurScope(0) {}
ScopedHashTable(AllocatorTy A)163   ScopedHashTable(AllocatorTy A) : CurScope(0), Allocator(A) {}
~ScopedHashTable()164   ~ScopedHashTable() {
165     assert(CurScope == 0 && TopLevelMap.empty() && "Scope imbalance!");
166   }
167 
168 
169   /// Access to the allocator.
170   typedef typename ReferenceAdder<AllocatorTy>::result AllocatorRefTy;
171   typedef typename ReferenceAdder<const AllocatorTy>::result AllocatorCRefTy;
getAllocator()172   AllocatorRefTy getAllocator() { return Allocator; }
getAllocator()173   AllocatorCRefTy getAllocator() const { return Allocator; }
174 
count(const K & Key)175   bool count(const K &Key) const {
176     return TopLevelMap.count(Key);
177   }
178 
lookup(const K & Key)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 
insert(const K & Key,const V & Val)187   void insert(const K &Key, const V &Val) {
188     insertIntoScope(CurScope, Key, Val);
189   }
190 
191   typedef ScopedHashTableIterator<K, V, KInfo> iterator;
192 
end()193   iterator end() { return iterator(0); }
194 
begin(const K & Key)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 
getCurScope()202   ScopeTy *getCurScope() { return CurScope; }
getCurScope()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.
insertIntoScope(ScopeTy * S,const K & Key,const V & Val)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.
220 template <typename K, typename V, typename KInfo, typename Allocator>
221 ScopedHashTableScope<K, V, KInfo, Allocator>::
ScopedHashTableScope(ScopedHashTable<K,V,KInfo,Allocator> & ht)222   ScopedHashTableScope(ScopedHashTable<K, V, KInfo, Allocator> &ht) : HT(ht) {
223   PrevScope = HT.CurScope;
224   HT.CurScope = this;
225   LastValInScope = 0;
226 }
227 
228 template <typename K, typename V, typename KInfo, typename Allocator>
~ScopedHashTableScope()229 ScopedHashTableScope<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() == 0) {
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