1 // Copyright 2012 the V8 project authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style license that can be
3 // found in the LICENSE file.
4 
5 #ifndef V8_PROPERTY_DETAILS_H_
6 #define V8_PROPERTY_DETAILS_H_
7 
8 #include "include/v8.h"
9 #include "src/allocation.h"
10 #include "src/utils.h"
11 
12 // Ecma-262 3rd 8.6.1
13 enum PropertyAttributes {
14   NONE              = v8::None,
15   READ_ONLY         = v8::ReadOnly,
16   DONT_ENUM         = v8::DontEnum,
17   DONT_DELETE       = v8::DontDelete,
18 
19   SEALED            = DONT_DELETE,
20   FROZEN            = SEALED | READ_ONLY,
21 
22   STRING            = 8,  // Used to filter symbols and string names
23   SYMBOLIC          = 16,
24   PRIVATE_SYMBOL    = 32,
25 
26   DONT_SHOW         = DONT_ENUM | SYMBOLIC | PRIVATE_SYMBOL,
27   ABSENT            = 64  // Used in runtime to indicate a property is absent.
28   // ABSENT can never be stored in or returned from a descriptor's attributes
29   // bitfield.  It is only used as a return value meaning the attributes of
30   // a non-existent property.
31 };
32 
33 
34 namespace v8 {
35 namespace internal {
36 
37 class Smi;
38 template<class> class TypeImpl;
39 struct ZoneTypeConfig;
40 typedef TypeImpl<ZoneTypeConfig> Type;
41 class TypeInfo;
42 
43 // Type of properties.
44 // Order of properties is significant.
45 // Must fit in the BitField PropertyDetails::TypeField.
46 // A copy of this is in mirror-debugger.js.
47 enum PropertyType {
48   // Only in slow mode.
49   NORMAL = 0,
50   // Only in fast mode.
51   FIELD = 1,
52   CONSTANT = 2,
53   CALLBACKS = 3
54 };
55 
56 
57 class Representation {
58  public:
59   enum Kind {
60     kNone,
61     kInteger8,
62     kUInteger8,
63     kInteger16,
64     kUInteger16,
65     kSmi,
66     kInteger32,
67     kDouble,
68     kHeapObject,
69     kTagged,
70     kExternal,
71     kNumRepresentations
72   };
73 
Representation()74   Representation() : kind_(kNone) { }
75 
None()76   static Representation None() { return Representation(kNone); }
Tagged()77   static Representation Tagged() { return Representation(kTagged); }
Integer8()78   static Representation Integer8() { return Representation(kInteger8); }
UInteger8()79   static Representation UInteger8() { return Representation(kUInteger8); }
Integer16()80   static Representation Integer16() { return Representation(kInteger16); }
UInteger16()81   static Representation UInteger16() { return Representation(kUInteger16); }
Smi()82   static Representation Smi() { return Representation(kSmi); }
Integer32()83   static Representation Integer32() { return Representation(kInteger32); }
Double()84   static Representation Double() { return Representation(kDouble); }
HeapObject()85   static Representation HeapObject() { return Representation(kHeapObject); }
External()86   static Representation External() { return Representation(kExternal); }
87 
FromKind(Kind kind)88   static Representation FromKind(Kind kind) { return Representation(kind); }
89 
90   static Representation FromType(Type* type);
91 
Equals(const Representation & other)92   bool Equals(const Representation& other) const {
93     return kind_ == other.kind_;
94   }
95 
IsCompatibleForLoad(const Representation & other)96   bool IsCompatibleForLoad(const Representation& other) const {
97     return (IsDouble() && other.IsDouble()) ||
98         (!IsDouble() && !other.IsDouble());
99   }
100 
IsCompatibleForStore(const Representation & other)101   bool IsCompatibleForStore(const Representation& other) const {
102     return Equals(other);
103   }
104 
is_more_general_than(const Representation & other)105   bool is_more_general_than(const Representation& other) const {
106     if (kind_ == kExternal && other.kind_ == kNone) return true;
107     if (kind_ == kExternal && other.kind_ == kExternal) return false;
108     if (kind_ == kNone && other.kind_ == kExternal) return false;
109 
110     DCHECK(kind_ != kExternal);
111     DCHECK(other.kind_ != kExternal);
112     if (IsHeapObject()) return other.IsNone();
113     if (kind_ == kUInteger8 && other.kind_ == kInteger8) return false;
114     if (kind_ == kUInteger16 && other.kind_ == kInteger16) return false;
115     return kind_ > other.kind_;
116   }
117 
fits_into(const Representation & other)118   bool fits_into(const Representation& other) const {
119     return other.is_more_general_than(*this) || other.Equals(*this);
120   }
121 
generalize(Representation other)122   Representation generalize(Representation other) {
123     if (other.fits_into(*this)) return *this;
124     if (other.is_more_general_than(*this)) return other;
125     return Representation::Tagged();
126   }
127 
size()128   int size() const {
129     DCHECK(!IsNone());
130     if (IsInteger8() || IsUInteger8()) {
131       return sizeof(uint8_t);
132     }
133     if (IsInteger16() || IsUInteger16()) {
134       return sizeof(uint16_t);
135     }
136     if (IsInteger32()) {
137       return sizeof(uint32_t);
138     }
139     return kPointerSize;
140   }
141 
kind()142   Kind kind() const { return static_cast<Kind>(kind_); }
IsNone()143   bool IsNone() const { return kind_ == kNone; }
IsInteger8()144   bool IsInteger8() const { return kind_ == kInteger8; }
IsUInteger8()145   bool IsUInteger8() const { return kind_ == kUInteger8; }
IsInteger16()146   bool IsInteger16() const { return kind_ == kInteger16; }
IsUInteger16()147   bool IsUInteger16() const { return kind_ == kUInteger16; }
IsTagged()148   bool IsTagged() const { return kind_ == kTagged; }
IsSmi()149   bool IsSmi() const { return kind_ == kSmi; }
IsSmiOrTagged()150   bool IsSmiOrTagged() const { return IsSmi() || IsTagged(); }
IsInteger32()151   bool IsInteger32() const { return kind_ == kInteger32; }
IsSmiOrInteger32()152   bool IsSmiOrInteger32() const { return IsSmi() || IsInteger32(); }
IsDouble()153   bool IsDouble() const { return kind_ == kDouble; }
IsHeapObject()154   bool IsHeapObject() const { return kind_ == kHeapObject; }
IsExternal()155   bool IsExternal() const { return kind_ == kExternal; }
IsSpecialization()156   bool IsSpecialization() const {
157     return IsInteger8() || IsUInteger8() ||
158       IsInteger16() || IsUInteger16() ||
159       IsSmi() || IsInteger32() || IsDouble();
160   }
161   const char* Mnemonic() const;
162 
163  private:
Representation(Kind k)164   explicit Representation(Kind k) : kind_(k) { }
165 
166   // Make sure kind fits in int8.
167   STATIC_ASSERT(kNumRepresentations <= (1 << kBitsPerByte));
168 
169   int8_t kind_;
170 };
171 
172 
173 static const int kDescriptorIndexBitCount = 10;
174 // The maximum number of descriptors we want in a descriptor array (should
175 // fit in a page).
176 static const int kMaxNumberOfDescriptors =
177     (1 << kDescriptorIndexBitCount) - 2;
178 static const int kInvalidEnumCacheSentinel =
179     (1 << kDescriptorIndexBitCount) - 1;
180 
181 
182 // PropertyDetails captures type and attributes for a property.
183 // They are used both in property dictionaries and instance descriptors.
184 class PropertyDetails BASE_EMBEDDED {
185  public:
PropertyDetails(PropertyAttributes attributes,PropertyType type,int index)186   PropertyDetails(PropertyAttributes attributes,
187                   PropertyType type,
188                   int index) {
189     value_ = TypeField::encode(type)
190         | AttributesField::encode(attributes)
191         | DictionaryStorageField::encode(index);
192 
193     DCHECK(type == this->type());
194     DCHECK(attributes == this->attributes());
195   }
196 
197   PropertyDetails(PropertyAttributes attributes,
198                   PropertyType type,
199                   Representation representation,
200                   int field_index = 0) {
201     value_ = TypeField::encode(type)
202         | AttributesField::encode(attributes)
203         | RepresentationField::encode(EncodeRepresentation(representation))
204         | FieldIndexField::encode(field_index);
205   }
206 
pointer()207   int pointer() const { return DescriptorPointer::decode(value_); }
208 
set_pointer(int i)209   PropertyDetails set_pointer(int i) { return PropertyDetails(value_, i); }
210 
CopyWithRepresentation(Representation representation)211   PropertyDetails CopyWithRepresentation(Representation representation) const {
212     return PropertyDetails(value_, representation);
213   }
CopyAddAttributes(PropertyAttributes new_attributes)214   PropertyDetails CopyAddAttributes(PropertyAttributes new_attributes) {
215     new_attributes =
216         static_cast<PropertyAttributes>(attributes() | new_attributes);
217     return PropertyDetails(value_, new_attributes);
218   }
219 
220   // Conversion for storing details as Object*.
221   explicit inline PropertyDetails(Smi* smi);
222   inline Smi* AsSmi() const;
223 
EncodeRepresentation(Representation representation)224   static uint8_t EncodeRepresentation(Representation representation) {
225     return representation.kind();
226   }
227 
DecodeRepresentation(uint32_t bits)228   static Representation DecodeRepresentation(uint32_t bits) {
229     return Representation::FromKind(static_cast<Representation::Kind>(bits));
230   }
231 
type()232   PropertyType type() const { return TypeField::decode(value_); }
233 
attributes()234   PropertyAttributes attributes() const {
235     return AttributesField::decode(value_);
236   }
237 
dictionary_index()238   int dictionary_index() const {
239     return DictionaryStorageField::decode(value_);
240   }
241 
representation()242   Representation representation() const {
243     DCHECK(type() != NORMAL);
244     return DecodeRepresentation(RepresentationField::decode(value_));
245   }
246 
field_index()247   int field_index() const {
248     return FieldIndexField::decode(value_);
249   }
250 
251   inline PropertyDetails AsDeleted() const;
252 
IsValidIndex(int index)253   static bool IsValidIndex(int index) {
254     return DictionaryStorageField::is_valid(index);
255   }
256 
IsReadOnly()257   bool IsReadOnly() const { return (attributes() & READ_ONLY) != 0; }
IsConfigurable()258   bool IsConfigurable() const { return (attributes() & DONT_DELETE) == 0; }
IsDontEnum()259   bool IsDontEnum() const { return (attributes() & DONT_ENUM) != 0; }
IsDeleted()260   bool IsDeleted() const { return DeletedField::decode(value_) != 0;}
261 
262   // Bit fields in value_ (type, shift, size). Must be public so the
263   // constants can be embedded in generated code.
264   class TypeField : public BitField<PropertyType, 0, 2> {};
265   class AttributesField : public BitField<PropertyAttributes, 2, 3> {};
266 
267   // Bit fields for normalized objects.
268   class DeletedField : public BitField<uint32_t, 5, 1> {};
269   class DictionaryStorageField : public BitField<uint32_t, 6, 24> {};
270 
271   // Bit fields for fast objects.
272   class RepresentationField : public BitField<uint32_t, 5, 4> {};
273   class DescriptorPointer
274       : public BitField<uint32_t, 9, kDescriptorIndexBitCount> {};  // NOLINT
275   class FieldIndexField
276       : public BitField<uint32_t, 9 + kDescriptorIndexBitCount,
277                         kDescriptorIndexBitCount> {};  // NOLINT
278   // All bits for fast objects must fix in a smi.
279   STATIC_ASSERT(9 + kDescriptorIndexBitCount + kDescriptorIndexBitCount <= 31);
280 
281   static const int kInitialIndex = 1;
282 
283  private:
PropertyDetails(int value,int pointer)284   PropertyDetails(int value, int pointer) {
285     value_ = DescriptorPointer::update(value, pointer);
286   }
PropertyDetails(int value,Representation representation)287   PropertyDetails(int value, Representation representation) {
288     value_ = RepresentationField::update(
289         value, EncodeRepresentation(representation));
290   }
PropertyDetails(int value,PropertyAttributes attributes)291   PropertyDetails(int value, PropertyAttributes attributes) {
292     value_ = AttributesField::update(value, attributes);
293   }
294 
295   uint32_t value_;
296 };
297 
298 } }  // namespace v8::internal
299 
300 #endif  // V8_PROPERTY_DETAILS_H_
301