Add a new dense hash table implementation

llvm-svn: 33751

llvm/include/llvm/ADT/DenseMap.h

@@ -0,0 +1,203 @@
+//===- llvm/ADT/DenseMap.h - Dense probed hash table ------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file was developed by Chris Lattner and is distributed under
+// the University of Illinois Open Source License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file defines the DenseMap class.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_ADT_DENSEMAP_H
+#define LLVM_ADT_DENSEMAP_H
+
+#include "llvm/Support/DataTypes.h"
+#include <cassert>
+
+namespace llvm {
+  
+template<typename T>
+struct DenseMapKeyInfo {
+  //static inline T getEmptyKey();
+  //static inline T getTombstoneKey();
+  //static unsigned getHashValue(const T &Val);
+  //static bool isPod()
+};
+
+template<typename T>
+struct DenseMapKeyInfo<T*> {
+  static inline T* getEmptyKey() { return (T*)-1; }
+  static inline T* getTombstoneKey() { return (T*)-2; }
+  static unsigned getHashValue(const T *PtrVal) {
+    return (unsigned)((uintptr_t)PtrVal >> 4) ^
+           (unsigned)((uintptr_t)PtrVal >> 9);
+  }
+  static bool isPod() { return true; }
+};
+
+
+template<typename KeyT, typename ValueT>
+class DenseMap {
+  struct BucketT { KeyT Key; ValueT Value; };
+  unsigned NumBuckets;
+  BucketT *Buckets;
+  
+  unsigned NumEntries;
+  DenseMap(const DenseMap &); // not implemented.
+public:
+  explicit DenseMap(unsigned NumInitBuckets = 8) {
+    init(NumInitBuckets);
+  }
+  ~DenseMap() {
+    const KeyT EmptyKey = getEmptyKey(), TombstoneKey = getTombstoneKey();
+    for (BucketT *P = Buckets, *E = Buckets+NumBuckets; P != E; ++P) {
+      if (P->Key != EmptyKey && P->Key != TombstoneKey)
+        P->Value.~ValueT();
+      P->Key.~KeyT();
+    }
+    delete[] (char*)Buckets;
+  }
+  
+  unsigned size() const { return NumEntries; }
+  
+  void clear() {
+    const KeyT EmptyKey = getEmptyKey(), TombstoneKey = getTombstoneKey();
+    for (BucketT *P = Buckets, *E = Buckets+NumBuckets; P != E; ++P) {
+      if (P->Key != EmptyKey && P->Key != TombstoneKey) {
+        P->Key = EmptyKey;
+        P->Value.~ValueT();
+        --NumEntries;
+      }
+    }
+    assert(NumEntries == 0 && "Node count imbalance!");
+  }
+  
+  /// count - Return true if the specified key is in the map.
+  bool count(const KeyT &Val) const {
+    BucketT *TheBucket;
+    return LookupBucketFor(Val, TheBucket);
+  }
+  
+  ValueT &operator[](const KeyT &Val) {
+    BucketT *TheBucket;
+    if (LookupBucketFor(Val, TheBucket))
+      return TheBucket->Value;
+
+    // If the load of the hash table is more than 3/4, grow it.
+    if (NumEntries*4 >= NumBuckets*3) {
+      this->grow();
+      LookupBucketFor(Val, TheBucket);
+    }
+    ++NumEntries;
+    TheBucket->Key = Val;
+    new (&TheBucket->Value) ValueT();
+    return TheBucket->Value;
+  }
+  
+private:
+  unsigned getHashValue(const KeyT &Val) const {
+    return DenseMapKeyInfo<KeyT>::getHashValue(Val);
+  }
+  const KeyT getEmptyKey() const { return DenseMapKeyInfo<KeyT>::getEmptyKey();}
+  const KeyT getTombstoneKey() const {
+    return DenseMapKeyInfo<KeyT>::getTombstoneKey();
+  }
+  
+  /// LookupBucketFor - Lookup the appropriate bucket for Val, returning it in
+  /// FoundBucket.  If the bucket contains the key and a value, this returns
+  /// true, otherwise it returns a bucket with an empty marker or tombstone and
+  /// returns false.
+  bool LookupBucketFor(const KeyT &Val, BucketT *&FoundBucket) const {
+    unsigned BucketNo = getHashValue(Val);
+    unsigned ProbeAmt = 1;
+    BucketT *BucketsPtr = Buckets;
+    
+    // FoundTombstone - Keep track of whether we find a tombstone while probing.
+    BucketT *FoundTombstone = 0;
+    const KeyT EmptyKey = getEmptyKey();
+    const KeyT TombstoneKey = getTombstoneKey();
+    assert(Val != EmptyKey && Val != TombstoneKey &&
+           "Empty/Tombstone value shouldn't be inserted into map!");
+      
+    while (1) {
+      BucketT *ThisBucket = BucketsPtr + (BucketNo & (NumBuckets-1));
+      // Found Val's bucket?  If so, return it.
+      if (ThisBucket->Key == Val) {
+        FoundBucket = ThisBucket;
+        return true;
+      }
+      
+      // If we found an empty bucket, the key doesn't exist in the set.
+      // Insert it and return the default value.
+      if (ThisBucket->Key == EmptyKey) {
+        // If we've already seen a tombstone while probing, fill it in instead
+        // of the empty bucket we eventually probed to.
+        if (FoundTombstone) ThisBucket = FoundTombstone;
+        FoundBucket = FoundTombstone ? FoundTombstone : ThisBucket;
+        return false;
+      }
+      
+      // If this is a tombstone, remember it.  If Val ends up not in the map, we
+      // prefer to return it than something that would require more probing.
+      if (ThisBucket->Key == TombstoneKey && !FoundTombstone)
+        FoundTombstone = ThisBucket;  // Remember the first tombstone found.
+      
+      // Otherwise, it's a hash collision or a tombstone, continue quadratic
+      // probing.
+      BucketNo += ProbeAmt++;
+    }
+  }
+
+  void init(unsigned InitBuckets) {
+    NumEntries = 0;
+    NumBuckets = InitBuckets;
+    assert(InitBuckets && (InitBuckets & InitBuckets-1) == 0 &&
+           "# initial buckets must be a power of two!");
+    Buckets = (BucketT*)new char[sizeof(BucketT)*InitBuckets];
+    // Initialize all the keys to EmptyKey.
+    const KeyT EmptyKey = getEmptyKey();
+    for (unsigned i = 0; i != InitBuckets; ++i)
+      new (&Buckets[i].Key) KeyT(EmptyKey);
+  }
+  
+  void grow() {
+    unsigned OldNumBuckets = NumBuckets;
+    BucketT *OldBuckets = Buckets;
+    
+    // Double the number of buckets.
+    NumBuckets <<= 1;
+    Buckets = (BucketT*)new char[sizeof(BucketT)*NumBuckets];
+
+    // Initialize all the keys to EmptyKey.
+    const KeyT EmptyKey = getEmptyKey();
+    for (unsigned i = 0, e = NumBuckets; i != e; ++i)
+      new (&Buckets[i].Key) KeyT(EmptyKey);
+
+    // Insert all the old elements.
+    const KeyT TombstoneKey = getTombstoneKey();
+    for (BucketT *B = OldBuckets, *E = OldBuckets+OldNumBuckets; B != E; ++B) {
+      if (B->Key != EmptyKey && B->Key != TombstoneKey) {
+        // Insert the key/value into the new table.
+        BucketT *DestBucket;
+        bool FoundVal = LookupBucketFor(B->Key, DestBucket);
+        assert(!FoundVal && "Key already in new map?");
+        DestBucket->Key = B->Key;
+        new (&DestBucket->Value) ValueT(B->Value);
+        
+        // Free the value.
+        B->Value.~ValueT();
+      }
+      B->Key.~KeyT();
+    }
+    
+    // Free the old table.
+    delete[] (char*)OldBuckets;
+  }
+};
+
+} // end namespace llvm
+
+#endif