Ben Murdoch | 3fb3ca8 | 2011-12-02 17:19:32 +0000 | [diff] [blame] | 1 | // Copyright 2011 the V8 project authors. All rights reserved. |
Iain Merrick | 7568138 | 2010-08-19 15:07:18 +0100 | [diff] [blame] | 2 | // Redistribution and use in source and binary forms, with or without |
| 3 | // modification, are permitted provided that the following conditions are |
| 4 | // met: |
| 5 | // |
| 6 | // * Redistributions of source code must retain the above copyright |
| 7 | // notice, this list of conditions and the following disclaimer. |
| 8 | // * Redistributions in binary form must reproduce the above |
| 9 | // copyright notice, this list of conditions and the following |
| 10 | // disclaimer in the documentation and/or other materials provided |
| 11 | // with the distribution. |
| 12 | // * Neither the name of Google Inc. nor the names of its |
| 13 | // contributors may be used to endorse or promote products derived |
| 14 | // from this software without specific prior written permission. |
| 15 | // |
| 16 | // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS |
| 17 | // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT |
| 18 | // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR |
| 19 | // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT |
| 20 | // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, |
| 21 | // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT |
| 22 | // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, |
| 23 | // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY |
| 24 | // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT |
| 25 | // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE |
| 26 | // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
| 27 | |
Ben Murdoch | f87a203 | 2010-10-22 12:50:53 +0100 | [diff] [blame] | 28 | #ifndef V8_OBJECTS_VISITING_H_ |
| 29 | #define V8_OBJECTS_VISITING_H_ |
Iain Merrick | 7568138 | 2010-08-19 15:07:18 +0100 | [diff] [blame] | 30 | |
Ben Murdoch | 257744e | 2011-11-30 15:57:28 +0000 | [diff] [blame] | 31 | #include "allocation.h" |
| 32 | |
Iain Merrick | 7568138 | 2010-08-19 15:07:18 +0100 | [diff] [blame] | 33 | // This file provides base classes and auxiliary methods for defining |
| 34 | // static object visitors used during GC. |
| 35 | // Visiting HeapObject body with a normal ObjectVisitor requires performing |
| 36 | // two switches on object's instance type to determine object size and layout |
| 37 | // and one or more virtual method calls on visitor itself. |
| 38 | // Static visitor is different: it provides a dispatch table which contains |
| 39 | // pointers to specialized visit functions. Each map has the visitor_id |
| 40 | // field which contains an index of specialized visitor to use. |
| 41 | |
| 42 | namespace v8 { |
| 43 | namespace internal { |
| 44 | |
| 45 | |
| 46 | // Base class for all static visitors. |
| 47 | class StaticVisitorBase : public AllStatic { |
| 48 | public: |
| 49 | enum VisitorId { |
| 50 | kVisitSeqAsciiString = 0, |
| 51 | kVisitSeqTwoByteString, |
| 52 | kVisitShortcutCandidate, |
| 53 | kVisitByteArray, |
Ben Murdoch | 3ef787d | 2012-04-12 10:51:47 +0100 | [diff] [blame] | 54 | kVisitFreeSpace, |
Iain Merrick | 7568138 | 2010-08-19 15:07:18 +0100 | [diff] [blame] | 55 | kVisitFixedArray, |
Ben Murdoch | 3fb3ca8 | 2011-12-02 17:19:32 +0000 | [diff] [blame] | 56 | kVisitFixedDoubleArray, |
Ben Murdoch | f87a203 | 2010-10-22 12:50:53 +0100 | [diff] [blame] | 57 | kVisitGlobalContext, |
Iain Merrick | 7568138 | 2010-08-19 15:07:18 +0100 | [diff] [blame] | 58 | |
| 59 | // For data objects, JS objects and structs along with generic visitor which |
| 60 | // can visit object of any size we provide visitors specialized by |
| 61 | // object size in words. |
| 62 | // Ids of specialized visitors are declared in a linear order (without |
| 63 | // holes) starting from the id of visitor specialized for 2 words objects |
| 64 | // (base visitor id) and ending with the id of generic visitor. |
| 65 | // Method GetVisitorIdForSize depends on this ordering to calculate visitor |
| 66 | // id of specialized visitor from given instance size, base visitor id and |
| 67 | // generic visitor's id. |
| 68 | |
| 69 | kVisitDataObject, |
| 70 | kVisitDataObject2 = kVisitDataObject, |
| 71 | kVisitDataObject3, |
| 72 | kVisitDataObject4, |
| 73 | kVisitDataObject5, |
| 74 | kVisitDataObject6, |
| 75 | kVisitDataObject7, |
| 76 | kVisitDataObject8, |
| 77 | kVisitDataObject9, |
| 78 | kVisitDataObjectGeneric, |
| 79 | |
| 80 | kVisitJSObject, |
| 81 | kVisitJSObject2 = kVisitJSObject, |
| 82 | kVisitJSObject3, |
| 83 | kVisitJSObject4, |
| 84 | kVisitJSObject5, |
| 85 | kVisitJSObject6, |
| 86 | kVisitJSObject7, |
| 87 | kVisitJSObject8, |
| 88 | kVisitJSObject9, |
| 89 | kVisitJSObjectGeneric, |
| 90 | |
| 91 | kVisitStruct, |
| 92 | kVisitStruct2 = kVisitStruct, |
| 93 | kVisitStruct3, |
| 94 | kVisitStruct4, |
| 95 | kVisitStruct5, |
| 96 | kVisitStruct6, |
| 97 | kVisitStruct7, |
| 98 | kVisitStruct8, |
| 99 | kVisitStruct9, |
| 100 | kVisitStructGeneric, |
| 101 | |
| 102 | kVisitConsString, |
Ben Murdoch | 69a99ed | 2011-11-30 16:03:39 +0000 | [diff] [blame] | 103 | kVisitSlicedString, |
Iain Merrick | 7568138 | 2010-08-19 15:07:18 +0100 | [diff] [blame] | 104 | kVisitOddball, |
| 105 | kVisitCode, |
| 106 | kVisitMap, |
| 107 | kVisitPropertyCell, |
| 108 | kVisitSharedFunctionInfo, |
| 109 | kVisitJSFunction, |
Ben Murdoch | 69a99ed | 2011-11-30 16:03:39 +0000 | [diff] [blame] | 110 | kVisitJSWeakMap, |
Ben Murdoch | 257744e | 2011-11-30 15:57:28 +0000 | [diff] [blame] | 111 | kVisitJSRegExp, |
Iain Merrick | 7568138 | 2010-08-19 15:07:18 +0100 | [diff] [blame] | 112 | |
| 113 | kVisitorIdCount, |
| 114 | kMinObjectSizeInWords = 2 |
| 115 | }; |
| 116 | |
Iain Merrick | 9ac36c9 | 2010-09-13 15:29:50 +0100 | [diff] [blame] | 117 | // Visitor ID should fit in one byte. |
| 118 | STATIC_ASSERT(kVisitorIdCount <= 256); |
| 119 | |
Iain Merrick | 7568138 | 2010-08-19 15:07:18 +0100 | [diff] [blame] | 120 | // Determine which specialized visitor should be used for given instance type |
| 121 | // and instance type. |
| 122 | static VisitorId GetVisitorId(int instance_type, int instance_size); |
| 123 | |
| 124 | static VisitorId GetVisitorId(Map* map) { |
| 125 | return GetVisitorId(map->instance_type(), map->instance_size()); |
| 126 | } |
| 127 | |
| 128 | // For visitors that allow specialization by size calculate VisitorId based |
| 129 | // on size, base visitor id and generic visitor id. |
| 130 | static VisitorId GetVisitorIdForSize(VisitorId base, |
| 131 | VisitorId generic, |
| 132 | int object_size) { |
| 133 | ASSERT((base == kVisitDataObject) || |
| 134 | (base == kVisitStruct) || |
| 135 | (base == kVisitJSObject)); |
| 136 | ASSERT(IsAligned(object_size, kPointerSize)); |
| 137 | ASSERT(kMinObjectSizeInWords * kPointerSize <= object_size); |
Ben Murdoch | 3ef787d | 2012-04-12 10:51:47 +0100 | [diff] [blame] | 138 | ASSERT(object_size < Page::kMaxNonCodeHeapObjectSize); |
Iain Merrick | 7568138 | 2010-08-19 15:07:18 +0100 | [diff] [blame] | 139 | |
| 140 | const VisitorId specialization = static_cast<VisitorId>( |
| 141 | base + (object_size >> kPointerSizeLog2) - kMinObjectSizeInWords); |
| 142 | |
| 143 | return Min(specialization, generic); |
| 144 | } |
| 145 | }; |
| 146 | |
| 147 | |
| 148 | template<typename Callback> |
| 149 | class VisitorDispatchTable { |
| 150 | public: |
Ben Murdoch | 8b112d2 | 2011-06-08 16:22:53 +0100 | [diff] [blame] | 151 | void CopyFrom(VisitorDispatchTable* other) { |
| 152 | // We are not using memcpy to guarantee that during update |
| 153 | // every element of callbacks_ array will remain correct |
| 154 | // pointer (memcpy might be implemented as a byte copying loop). |
| 155 | for (int i = 0; i < StaticVisitorBase::kVisitorIdCount; i++) { |
| 156 | NoBarrier_Store(&callbacks_[i], other->callbacks_[i]); |
| 157 | } |
| 158 | } |
| 159 | |
Ben Murdoch | 3ef787d | 2012-04-12 10:51:47 +0100 | [diff] [blame] | 160 | inline Callback GetVisitorById(StaticVisitorBase::VisitorId id) { |
| 161 | return reinterpret_cast<Callback>(callbacks_[id]); |
| 162 | } |
| 163 | |
Iain Merrick | 7568138 | 2010-08-19 15:07:18 +0100 | [diff] [blame] | 164 | inline Callback GetVisitor(Map* map) { |
Ben Murdoch | 8b112d2 | 2011-06-08 16:22:53 +0100 | [diff] [blame] | 165 | return reinterpret_cast<Callback>(callbacks_[map->visitor_id()]); |
Iain Merrick | 7568138 | 2010-08-19 15:07:18 +0100 | [diff] [blame] | 166 | } |
| 167 | |
| 168 | void Register(StaticVisitorBase::VisitorId id, Callback callback) { |
Ben Murdoch | b8e0da2 | 2011-05-16 14:20:40 +0100 | [diff] [blame] | 169 | ASSERT(id < StaticVisitorBase::kVisitorIdCount); // id is unsigned. |
Ben Murdoch | 8b112d2 | 2011-06-08 16:22:53 +0100 | [diff] [blame] | 170 | callbacks_[id] = reinterpret_cast<AtomicWord>(callback); |
Iain Merrick | 7568138 | 2010-08-19 15:07:18 +0100 | [diff] [blame] | 171 | } |
| 172 | |
| 173 | template<typename Visitor, |
| 174 | StaticVisitorBase::VisitorId base, |
| 175 | StaticVisitorBase::VisitorId generic, |
| 176 | int object_size_in_words> |
| 177 | void RegisterSpecialization() { |
| 178 | static const int size = object_size_in_words * kPointerSize; |
| 179 | Register(StaticVisitorBase::GetVisitorIdForSize(base, generic, size), |
| 180 | &Visitor::template VisitSpecialized<size>); |
| 181 | } |
| 182 | |
| 183 | |
| 184 | template<typename Visitor, |
| 185 | StaticVisitorBase::VisitorId base, |
| 186 | StaticVisitorBase::VisitorId generic> |
| 187 | void RegisterSpecializations() { |
| 188 | STATIC_ASSERT( |
| 189 | (generic - base + StaticVisitorBase::kMinObjectSizeInWords) == 10); |
| 190 | RegisterSpecialization<Visitor, base, generic, 2>(); |
| 191 | RegisterSpecialization<Visitor, base, generic, 3>(); |
| 192 | RegisterSpecialization<Visitor, base, generic, 4>(); |
| 193 | RegisterSpecialization<Visitor, base, generic, 5>(); |
| 194 | RegisterSpecialization<Visitor, base, generic, 6>(); |
| 195 | RegisterSpecialization<Visitor, base, generic, 7>(); |
| 196 | RegisterSpecialization<Visitor, base, generic, 8>(); |
| 197 | RegisterSpecialization<Visitor, base, generic, 9>(); |
| 198 | Register(generic, &Visitor::Visit); |
| 199 | } |
| 200 | |
| 201 | private: |
Ben Murdoch | 8b112d2 | 2011-06-08 16:22:53 +0100 | [diff] [blame] | 202 | AtomicWord callbacks_[StaticVisitorBase::kVisitorIdCount]; |
Iain Merrick | 7568138 | 2010-08-19 15:07:18 +0100 | [diff] [blame] | 203 | }; |
| 204 | |
| 205 | |
| 206 | template<typename StaticVisitor> |
| 207 | class BodyVisitorBase : public AllStatic { |
| 208 | public: |
Steve Block | 44f0eee | 2011-05-26 01:26:41 +0100 | [diff] [blame] | 209 | INLINE(static void IteratePointers(Heap* heap, |
| 210 | HeapObject* object, |
Iain Merrick | 7568138 | 2010-08-19 15:07:18 +0100 | [diff] [blame] | 211 | int start_offset, |
Steve Block | 9fac840 | 2011-05-12 15:51:54 +0100 | [diff] [blame] | 212 | int end_offset)) { |
Iain Merrick | 7568138 | 2010-08-19 15:07:18 +0100 | [diff] [blame] | 213 | Object** start_slot = reinterpret_cast<Object**>(object->address() + |
| 214 | start_offset); |
| 215 | Object** end_slot = reinterpret_cast<Object**>(object->address() + |
| 216 | end_offset); |
Steve Block | 44f0eee | 2011-05-26 01:26:41 +0100 | [diff] [blame] | 217 | StaticVisitor::VisitPointers(heap, start_slot, end_slot); |
Iain Merrick | 7568138 | 2010-08-19 15:07:18 +0100 | [diff] [blame] | 218 | } |
| 219 | }; |
| 220 | |
| 221 | |
| 222 | template<typename StaticVisitor, typename BodyDescriptor, typename ReturnType> |
| 223 | class FlexibleBodyVisitor : public BodyVisitorBase<StaticVisitor> { |
| 224 | public: |
| 225 | static inline ReturnType Visit(Map* map, HeapObject* object) { |
| 226 | int object_size = BodyDescriptor::SizeOf(map, object); |
Steve Block | 791712a | 2010-08-27 10:21:07 +0100 | [diff] [blame] | 227 | BodyVisitorBase<StaticVisitor>::IteratePointers( |
Ben Murdoch | 3ef787d | 2012-04-12 10:51:47 +0100 | [diff] [blame] | 228 | map->GetHeap(), |
Steve Block | 44f0eee | 2011-05-26 01:26:41 +0100 | [diff] [blame] | 229 | object, |
| 230 | BodyDescriptor::kStartOffset, |
| 231 | object_size); |
Iain Merrick | 7568138 | 2010-08-19 15:07:18 +0100 | [diff] [blame] | 232 | return static_cast<ReturnType>(object_size); |
| 233 | } |
| 234 | |
| 235 | template<int object_size> |
| 236 | static inline ReturnType VisitSpecialized(Map* map, HeapObject* object) { |
| 237 | ASSERT(BodyDescriptor::SizeOf(map, object) == object_size); |
Steve Block | 791712a | 2010-08-27 10:21:07 +0100 | [diff] [blame] | 238 | BodyVisitorBase<StaticVisitor>::IteratePointers( |
Ben Murdoch | 3ef787d | 2012-04-12 10:51:47 +0100 | [diff] [blame] | 239 | map->GetHeap(), |
Steve Block | 44f0eee | 2011-05-26 01:26:41 +0100 | [diff] [blame] | 240 | object, |
| 241 | BodyDescriptor::kStartOffset, |
| 242 | object_size); |
Iain Merrick | 7568138 | 2010-08-19 15:07:18 +0100 | [diff] [blame] | 243 | return static_cast<ReturnType>(object_size); |
| 244 | } |
| 245 | }; |
| 246 | |
| 247 | |
| 248 | template<typename StaticVisitor, typename BodyDescriptor, typename ReturnType> |
| 249 | class FixedBodyVisitor : public BodyVisitorBase<StaticVisitor> { |
| 250 | public: |
| 251 | static inline ReturnType Visit(Map* map, HeapObject* object) { |
Steve Block | 791712a | 2010-08-27 10:21:07 +0100 | [diff] [blame] | 252 | BodyVisitorBase<StaticVisitor>::IteratePointers( |
Ben Murdoch | 3ef787d | 2012-04-12 10:51:47 +0100 | [diff] [blame] | 253 | map->GetHeap(), |
Steve Block | 44f0eee | 2011-05-26 01:26:41 +0100 | [diff] [blame] | 254 | object, |
| 255 | BodyDescriptor::kStartOffset, |
| 256 | BodyDescriptor::kEndOffset); |
Iain Merrick | 7568138 | 2010-08-19 15:07:18 +0100 | [diff] [blame] | 257 | return static_cast<ReturnType>(BodyDescriptor::kSize); |
| 258 | } |
| 259 | }; |
| 260 | |
| 261 | |
| 262 | // Base class for visitors used for a linear new space iteration. |
| 263 | // IterateBody returns size of visited object. |
| 264 | // Certain types of objects (i.e. Code objects) are not handled |
| 265 | // by dispatch table of this visitor because they cannot appear |
| 266 | // in the new space. |
| 267 | // |
| 268 | // This class is intended to be used in the following way: |
| 269 | // |
| 270 | // class SomeVisitor : public StaticNewSpaceVisitor<SomeVisitor> { |
| 271 | // ... |
| 272 | // } |
| 273 | // |
| 274 | // This is an example of Curiously recurring template pattern |
| 275 | // (see http://en.wikipedia.org/wiki/Curiously_recurring_template_pattern). |
| 276 | // We use CRTP to guarantee aggressive compile time optimizations (i.e. |
| 277 | // inlining and specialization of StaticVisitor::VisitPointers methods). |
| 278 | template<typename StaticVisitor> |
| 279 | class StaticNewSpaceVisitor : public StaticVisitorBase { |
| 280 | public: |
Ben Murdoch | 3ef787d | 2012-04-12 10:51:47 +0100 | [diff] [blame] | 281 | static void Initialize(); |
Iain Merrick | 7568138 | 2010-08-19 15:07:18 +0100 | [diff] [blame] | 282 | |
| 283 | static inline int IterateBody(Map* map, HeapObject* obj) { |
| 284 | return table_.GetVisitor(map)(map, obj); |
| 285 | } |
| 286 | |
Steve Block | 44f0eee | 2011-05-26 01:26:41 +0100 | [diff] [blame] | 287 | static inline void VisitPointers(Heap* heap, Object** start, Object** end) { |
| 288 | for (Object** p = start; p < end; p++) StaticVisitor::VisitPointer(heap, p); |
Iain Merrick | 7568138 | 2010-08-19 15:07:18 +0100 | [diff] [blame] | 289 | } |
| 290 | |
| 291 | private: |
| 292 | static inline int VisitByteArray(Map* map, HeapObject* object) { |
| 293 | return reinterpret_cast<ByteArray*>(object)->ByteArraySize(); |
| 294 | } |
| 295 | |
Ben Murdoch | 3fb3ca8 | 2011-12-02 17:19:32 +0000 | [diff] [blame] | 296 | static inline int VisitFixedDoubleArray(Map* map, HeapObject* object) { |
| 297 | int length = reinterpret_cast<FixedDoubleArray*>(object)->length(); |
| 298 | return FixedDoubleArray::SizeFor(length); |
| 299 | } |
| 300 | |
Ben Murdoch | 69a99ed | 2011-11-30 16:03:39 +0000 | [diff] [blame] | 301 | static inline int VisitJSObject(Map* map, HeapObject* object) { |
| 302 | return JSObjectVisitor::Visit(map, object); |
| 303 | } |
| 304 | |
Iain Merrick | 7568138 | 2010-08-19 15:07:18 +0100 | [diff] [blame] | 305 | static inline int VisitSeqAsciiString(Map* map, HeapObject* object) { |
| 306 | return SeqAsciiString::cast(object)-> |
| 307 | SeqAsciiStringSize(map->instance_type()); |
| 308 | } |
| 309 | |
| 310 | static inline int VisitSeqTwoByteString(Map* map, HeapObject* object) { |
| 311 | return SeqTwoByteString::cast(object)-> |
| 312 | SeqTwoByteStringSize(map->instance_type()); |
| 313 | } |
| 314 | |
Ben Murdoch | 3ef787d | 2012-04-12 10:51:47 +0100 | [diff] [blame] | 315 | static inline int VisitFreeSpace(Map* map, HeapObject* object) { |
| 316 | return FreeSpace::cast(object)->Size(); |
| 317 | } |
| 318 | |
Iain Merrick | 7568138 | 2010-08-19 15:07:18 +0100 | [diff] [blame] | 319 | class DataObjectVisitor { |
| 320 | public: |
| 321 | template<int object_size> |
| 322 | static inline int VisitSpecialized(Map* map, HeapObject* object) { |
| 323 | return object_size; |
| 324 | } |
| 325 | |
| 326 | static inline int Visit(Map* map, HeapObject* object) { |
| 327 | return map->instance_size(); |
| 328 | } |
| 329 | }; |
| 330 | |
| 331 | typedef FlexibleBodyVisitor<StaticVisitor, |
| 332 | StructBodyDescriptor, |
| 333 | int> StructVisitor; |
| 334 | |
| 335 | typedef FlexibleBodyVisitor<StaticVisitor, |
| 336 | JSObject::BodyDescriptor, |
| 337 | int> JSObjectVisitor; |
| 338 | |
| 339 | typedef int (*Callback)(Map* map, HeapObject* object); |
| 340 | |
| 341 | static VisitorDispatchTable<Callback> table_; |
| 342 | }; |
| 343 | |
| 344 | |
| 345 | template<typename StaticVisitor> |
| 346 | VisitorDispatchTable<typename StaticNewSpaceVisitor<StaticVisitor>::Callback> |
| 347 | StaticNewSpaceVisitor<StaticVisitor>::table_; |
| 348 | |
| 349 | |
Iain Merrick | 7568138 | 2010-08-19 15:07:18 +0100 | [diff] [blame] | 350 | } } // namespace v8::internal |
| 351 | |
Ben Murdoch | f87a203 | 2010-10-22 12:50:53 +0100 | [diff] [blame] | 352 | #endif // V8_OBJECTS_VISITING_H_ |