1/*
2 * Copyright (C) 2016 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,
18 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
19 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
20 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
21 * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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#pragma once
27
28#include "JSObject.h"
29#include "PropertySlot.h"
30#include "Structure.h"
31
32namespace JSC {
33
34class HasOwnPropertyCache {
35 static const uint32_t size = 2 * 1024;
36 static_assert(hasOneBitSet(size), "size should be a power of two.");
37public:
38 static const uint32_t mask = size - 1;
39
40 struct Entry {
41 static ptrdiff_t offsetOfStructureID() { return OBJECT_OFFSETOF(Entry, structureID); }
42 static ptrdiff_t offsetOfImpl() { return OBJECT_OFFSETOF(Entry, impl); }
43 static ptrdiff_t offsetOfResult() { return OBJECT_OFFSETOF(Entry, result); }
44
45 RefPtr<UniquedStringImpl> impl;
46 StructureID structureID { 0 };
47 bool result { false };
48 };
49
50 HasOwnPropertyCache() = delete;
51
52 void operator delete(void* cache)
53 {
54 static_cast<HasOwnPropertyCache*>(cache)->clear();
55 fastFree(cache);
56 }
57
58 static HasOwnPropertyCache* create()
59 {
60 size_t allocationSize = sizeof(Entry) * size;
61 HasOwnPropertyCache* result = static_cast<HasOwnPropertyCache*>(fastMalloc(allocationSize));
62 result->clearBuffer();
63 return result;
64 }
65
66 ALWAYS_INLINE static uint32_t hash(StructureID structureID, UniquedStringImpl* impl)
67 {
68 return bitwise_cast<uint32_t>(structureID) + impl->hash();
69 }
70
71 ALWAYS_INLINE Optional<bool> get(Structure* structure, PropertyName propName)
72 {
73 UniquedStringImpl* impl = propName.uid();
74 StructureID id = structure->id();
75 uint32_t index = HasOwnPropertyCache::hash(id, impl) & mask;
76 Entry& entry = bitwise_cast<Entry*>(this)[index];
77 if (entry.structureID == id && entry.impl.get() == impl)
78 return entry.result;
79 return WTF::nullopt;
80 }
81
82 ALWAYS_INLINE void tryAdd(VM& vm, PropertySlot& slot, JSObject* object, PropertyName propName, bool result)
83 {
84 if (parseIndex(propName))
85 return;
86
87 if (!slot.isCacheable() && !slot.isUnset())
88 return;
89
90 if (object->type() == PureForwardingProxyType || object->type() == ImpureProxyType)
91 return;
92
93 Structure* structure = object->structure(vm);
94 if (!structure->typeInfo().prohibitsPropertyCaching()
95 && structure->propertyAccessesAreCacheable()
96 && (!slot.isUnset() || structure->propertyAccessesAreCacheableForAbsence())) {
97 if (structure->isDictionary()) {
98 // FIXME: We should be able to flatten a dictionary object again.
99 // https://bugs.webkit.org/show_bug.cgi?id=163092
100 return;
101 }
102
103 ASSERT(!result == slot.isUnset());
104
105 UniquedStringImpl* impl = propName.uid();
106 StructureID id = structure->id();
107 uint32_t index = HasOwnPropertyCache::hash(id, impl) & mask;
108 bitwise_cast<Entry*>(this)[index] = Entry { RefPtr<UniquedStringImpl>(impl), id, result };
109 }
110 }
111
112 void clear()
113 {
114 Entry* buffer = bitwise_cast<Entry*>(this);
115 for (uint32_t i = 0; i < size; ++i)
116 buffer[i].Entry::~Entry();
117
118 clearBuffer();
119 }
120
121private:
122 void clearBuffer()
123 {
124 Entry* buffer = bitwise_cast<Entry*>(this);
125 for (uint32_t i = 0; i < size; ++i)
126 new (&buffer[i]) Entry();
127 }
128};
129
130ALWAYS_INLINE HasOwnPropertyCache* VM::ensureHasOwnPropertyCache()
131{
132 if (UNLIKELY(!m_hasOwnPropertyCache))
133 m_hasOwnPropertyCache = std::unique_ptr<HasOwnPropertyCache>(HasOwnPropertyCache::create());
134 return m_hasOwnPropertyCache.get();
135}
136
137} // namespace JSC
138