runtime/StructureTransitionTable.h

   1 /*
   2  * Copyright (C) 2008, 2009, 2013 Apple Inc. All rights reserved.
   3  *
   4  * Redistribution and use in source and binary forms, with or without
   5  * modification, are permitted provided that the following conditions
   6  * are met:
   7  * 1. Redistributions of source code must retain the above copyright
   8  *    notice, this list of conditions and the following disclaimer.
   9  * 2. Redistributions in binary form must reproduce the above copyright
  10  *    notice, this list of conditions and the following disclaimer in the
  11  *    documentation and/or other materials provided with the distribution.
  12  *
  13  * THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
  14  * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  15  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
  16  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE INC. OR
  17  * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
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  19  * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
  20  * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
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  22  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  23  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  24  */
  25
  26 #ifndef StructureTransitionTable_h
  27 #define StructureTransitionTable_h
  28
  29 #include "IndexingType.h"
  30 #include "WeakGCMap.h"
  31 #include <wtf/HashFunctions.h>
  32 #include <wtf/OwnPtr.h>
  33 #include <wtf/text/StringImpl.h>
  34
  35 namespace JSC {
  36
  37 class JSCell;
  38 class Structure;
  39
  40 static const unsigned FirstInternalAttribute = 1 << 6; // Use for transitions that don't have to do with property additions.
  41
  42 // Support for attributes used to indicate transitions not related to properties.
  43 // If any of these are used, the string portion of the key should be 0.
  44 enum NonPropertyTransition {
  45     AllocateUndecided,
  46     AllocateInt32,
  47     AllocateDouble,
  48     AllocateContiguous,
  49     AllocateArrayStorage,
  50     AllocateSlowPutArrayStorage,
  51     SwitchToSlowPutArrayStorage,
  52     AddIndexedAccessors
  53 };
  54
  55 inline unsigned toAttributes(NonPropertyTransition transition)
  56 {
  57     return transition + FirstInternalAttribute;
  58 }
  59
  60 inline IndexingType newIndexingType(IndexingType oldType, NonPropertyTransition transition)
  61 {
  62     switch (transition) {
  63     case AllocateUndecided:
  64         ASSERT(!hasIndexedProperties(oldType));
  65         return oldType | UndecidedShape;
  66     case AllocateInt32:
  67         ASSERT(!hasIndexedProperties(oldType) || hasUndecided(oldType));
  68         return (oldType & ~IndexingShapeMask) | Int32Shape;
  69     case AllocateDouble:
  70         ASSERT(!hasIndexedProperties(oldType) || hasUndecided(oldType) || hasInt32(oldType));
  71         return (oldType & ~IndexingShapeMask) | DoubleShape;
  72     case AllocateContiguous:
  73         ASSERT(!hasIndexedProperties(oldType) || hasUndecided(oldType) || hasInt32(oldType) || hasDouble(oldType));
  74         return (oldType & ~IndexingShapeMask) | ContiguousShape;
  75     case AllocateArrayStorage:
  76         ASSERT(!hasIndexedProperties(oldType) || hasUndecided(oldType) || hasInt32(oldType) || hasDouble(oldType) || hasContiguous(oldType));
  77         return (oldType & ~IndexingShapeMask) | ArrayStorageShape;
  78     case AllocateSlowPutArrayStorage:
  79         ASSERT(!hasIndexedProperties(oldType) || hasUndecided(oldType) || hasInt32(oldType) || hasDouble(oldType) || hasContiguous(oldType) || hasContiguous(oldType));
  80         return (oldType & ~IndexingShapeMask) | SlowPutArrayStorageShape;
  81     case SwitchToSlowPutArrayStorage:
  82         ASSERT(hasArrayStorage(oldType));
  83         return (oldType & ~IndexingShapeMask) | SlowPutArrayStorageShape;
  84     case AddIndexedAccessors:
  85         return oldType | MayHaveIndexedAccessors;
  86     default:
  87         RELEASE_ASSERT_NOT_REACHED();
  88         return oldType;
  89     }
  90 }
  91
  92 class StructureTransitionTable {
  93     static const intptr_t UsingSingleSlotFlag = 1;
  94
  95
  96     struct Hash {
  97         typedef std::pair<StringImpl*, unsigned> Key;
  98
  99         static unsigned hash(const Key& p)
 100         {
 101             return PtrHash<StringImpl*>::hash(p.first) + p.second;
 102         }
 103
 104         static bool equal(const Key& a, const Key& b)
 105         {
 106             return a == b;
 107         }
 108
 109         static const bool safeToCompareToEmptyOrDeleted = true;
 110     };
 111
 112     typedef WeakGCMap<Hash::Key, Structure, Hash> TransitionMap;
 113
 114 public:
 115     StructureTransitionTable()
 116         : m_data(UsingSingleSlotFlag)
 117     {
 118     }
 119
 120     ~StructureTransitionTable()
 121     {
 122         if (!isUsingSingleSlot()) {
 123             delete map();
 124             return;
 125         }
 126
 127         WeakImpl* impl = this->weakImpl();
 128         if (!impl)
 129             return;
 130         WeakSet::deallocate(impl);
 131     }
 132
 133     inline void add(VM&, Structure*);
 134     inline bool contains(StringImpl* rep, unsigned attributes) const;
 135     inline Structure* get(StringImpl* rep, unsigned attributes) const;
 136
 137 private:
 138     bool isUsingSingleSlot() const
 139     {
 140         return m_data & UsingSingleSlotFlag;
 141     }
 142
 143     TransitionMap* map() const
 144     {
 145         ASSERT(!isUsingSingleSlot());
 146         return reinterpret_cast<TransitionMap*>(m_data);
 147     }
 148
 149     WeakImpl* weakImpl() const
 150     {
 151         ASSERT(isUsingSingleSlot());
 152         return reinterpret_cast<WeakImpl*>(m_data & ~UsingSingleSlotFlag);
 153     }
 154
 155     void setMap(TransitionMap* map)
 156     {
 157         ASSERT(isUsingSingleSlot());
 158
 159         if (WeakImpl* impl = this->weakImpl())
 160             WeakSet::deallocate(impl);
 161
 162         // This implicitly clears the flag that indicates we're using a single transition
 163         m_data = reinterpret_cast<intptr_t>(map);
 164
 165         ASSERT(!isUsingSingleSlot());
 166     }
 167
 168     Structure* singleTransition() const
 169     {
 170         ASSERT(isUsingSingleSlot());
 171         if (WeakImpl* impl = this->weakImpl()) {
 172             if (impl->state() == WeakImpl::Live)
 173                 return reinterpret_cast<Structure*>(impl->jsValue().asCell());
 174         }
 175         return 0;
 176     }
 177
 178     void setSingleTransition(VM&, Structure* structure)
 179     {
 180         ASSERT(isUsingSingleSlot());
 181         if (WeakImpl* impl = this->weakImpl())
 182             WeakSet::deallocate(impl);
 183         WeakImpl* impl = WeakSet::allocate(reinterpret_cast<JSCell*>(structure));
 184         m_data = reinterpret_cast<intptr_t>(impl) | UsingSingleSlotFlag;
 185     }
 186
 187     intptr_t m_data;
 188 };
 189
 190 } // namespace JSC
 191
 192 #endif // StructureTransitionTable_h