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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;
     49   ScopedHashTableVal(const K &key, const V &val) : Key(key), Val(val) {}
     50 public:
     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 
     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 
     99   ScopedHashTableScope *getParentScope() { return PrevScope; }
    100   const ScopedHashTableScope *getParentScope() const { return PrevScope; }
    101 
    102 private:
    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 
    113 template <typename K, typename V, typename KInfo = DenseMapInfo<K> >
    114 class ScopedHashTableIterator {
    115   ScopedHashTableVal<K, V> *Node;
    116 public:
    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:
    162   ScopedHashTable() : CurScope(0) {}
    163   ScopedHashTable(AllocatorTy A) : CurScope(0), Allocator(A) {}
    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;
    172   AllocatorRefTy getAllocator() { return Allocator; }
    173   AllocatorCRefTy getAllocator() const { return Allocator; }
    174 
    175   bool 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.
    220 template <typename K, typename V, typename KInfo, typename Allocator>
    221 ScopedHashTableScope<K, V, KInfo, Allocator>::
    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>
    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