mark-compact.h revision 5913587db4c6bab03d97bfe44b06289fd6d7270d
1a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block// Copyright 2006-2008 the V8 project authors. All rights reserved. 2a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block// Redistribution and use in source and binary forms, with or without 3a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block// modification, are permitted provided that the following conditions are 4a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block// met: 5a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block// 6a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block// * Redistributions of source code must retain the above copyright 7a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block// notice, this list of conditions and the following disclaimer. 8a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block// * Redistributions in binary form must reproduce the above 9a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block// copyright notice, this list of conditions and the following 10a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block// disclaimer in the documentation and/or other materials provided 11a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block// with the distribution. 12a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block// * Neither the name of Google Inc. nor the names of its 13a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block// contributors may be used to endorse or promote products derived 14a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block// from this software without specific prior written permission. 15a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block// 16a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 17a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 18a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR 19a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT 20a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 21a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT 22a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 23a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 24a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 25a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE 26a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 27a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block 28a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block#ifndef V8_MARK_COMPACT_H_ 29a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block#define V8_MARK_COMPACT_H_ 30a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block 31a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Blocknamespace v8 { 32a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Blocknamespace internal { 33a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block 34a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block// Callback function, returns whether an object is alive. The heap size 35a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block// of the object is returned in size. It optionally updates the offset 36a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block// to the first live object in the page (only used for old and map objects). 37a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Blocktypedef bool (*IsAliveFunction)(HeapObject* obj, int* size, int* offset); 38a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block 39a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block// Forward declarations. 40a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Blockclass RootMarkingVisitor; 41a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Blockclass MarkingVisitor; 42a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block 43a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block 44a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block// ------------------------------------------------------------------------- 45a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block// Mark-Compact collector 46a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block// 47a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block// All methods are static. 48a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block 49a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Blockclass MarkCompactCollector: public AllStatic { 50a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block public: 51a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // Type of functions to compute forwarding addresses of objects in 52a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // compacted spaces. Given an object and its size, return a (non-failure) 53a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // Object* that will be the object after forwarding. There is a separate 54a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // allocation function for each (compactable) space based on the location 55a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // of the object before compaction. 565913587db4c6bab03d97bfe44b06289fd6d7270dJohn Reck typedef MaybeObject* (*AllocationFunction)(HeapObject* object, 575913587db4c6bab03d97bfe44b06289fd6d7270dJohn Reck int object_size); 58a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block 59a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // Type of functions to encode the forwarding address for an object. 60a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // Given the object, its size, and the new (non-failure) object it will be 61a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // forwarded to, encode the forwarding address. For paged spaces, the 62a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // 'offset' input/output parameter contains the offset of the forwarded 63a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // object from the forwarding address of the previous live object in the 64a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // page as input, and is updated to contain the offset to be used for the 65a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // next live object in the same page. For spaces using a different 66a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // encoding (ie, contiguous spaces), the offset parameter is ignored. 67a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block typedef void (*EncodingFunction)(HeapObject* old_object, 68a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block int object_size, 69a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block Object* new_object, 70a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block int* offset); 71a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block 72a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // Type of functions to process non-live objects. 73a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block typedef void (*ProcessNonLiveFunction)(HeapObject* object); 74a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block 75a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // Set the global force_compaction flag, it must be called before Prepare 76a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // to take effect. 77a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block static void SetForceCompaction(bool value) { 78a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block force_compaction_ = value; 79a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block } 80a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block 81756813857a4c2a4d8ad2e805969d5768d3cf43a0Iain Merrick 82756813857a4c2a4d8ad2e805969d5768d3cf43a0Iain Merrick static void Initialize(); 83756813857a4c2a4d8ad2e805969d5768d3cf43a0Iain Merrick 84a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // Prepares for GC by resetting relocation info in old and map spaces and 85a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // choosing spaces to compact. 86a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block static void Prepare(GCTracer* tracer); 87a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block 88a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // Performs a global garbage collection. 89a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block static void CollectGarbage(); 90a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block 91a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // True if the last full GC performed heap compaction. 92a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block static bool HasCompacted() { return compacting_collection_; } 93a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block 94a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // True after the Prepare phase if the compaction is taking place. 95e46be819fca9468a0cd4e74859ce0f778eb8ca60Leon Clarke static bool IsCompacting() { 96e46be819fca9468a0cd4e74859ce0f778eb8ca60Leon Clarke#ifdef DEBUG 97e46be819fca9468a0cd4e74859ce0f778eb8ca60Leon Clarke // For the purposes of asserts we don't want this to keep returning true 98e46be819fca9468a0cd4e74859ce0f778eb8ca60Leon Clarke // after the collection is completed. 99e46be819fca9468a0cd4e74859ce0f778eb8ca60Leon Clarke return state_ != IDLE && compacting_collection_; 100e46be819fca9468a0cd4e74859ce0f778eb8ca60Leon Clarke#else 101e46be819fca9468a0cd4e74859ce0f778eb8ca60Leon Clarke return compacting_collection_; 102e46be819fca9468a0cd4e74859ce0f778eb8ca60Leon Clarke#endif 103e46be819fca9468a0cd4e74859ce0f778eb8ca60Leon Clarke } 104a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block 105a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // The count of the number of objects left marked at the end of the last 106a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // completed full GC (expected to be zero). 107a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block static int previous_marked_count() { return previous_marked_count_; } 108a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block 109a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // During a full GC, there is a stack-allocated GCTracer that is used for 110a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // bookkeeping information. Return a pointer to that tracer. 111a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block static GCTracer* tracer() { return tracer_; } 112a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block 113a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block#ifdef DEBUG 114a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // Checks whether performing mark-compact collection. 115a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block static bool in_use() { return state_ > PREPARE_GC; } 11680d68eab642096c1a48b6474d6ec33064b0ad1f5Kristian Monsen static bool are_map_pointers_encoded() { return state_ == UPDATE_POINTERS; } 117a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block#endif 118a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block 119d91b9f7d46489a9ee00f9cb415630299c76a502bLeon Clarke // Determine type of object and emit deletion log event. 120d91b9f7d46489a9ee00f9cb415630299c76a502bLeon Clarke static void ReportDeleteIfNeeded(HeapObject* obj); 121d91b9f7d46489a9ee00f9cb415630299c76a502bLeon Clarke 12280d68eab642096c1a48b6474d6ec33064b0ad1f5Kristian Monsen // Distinguishable invalid map encodings (for single word and multiple words) 12380d68eab642096c1a48b6474d6ec33064b0ad1f5Kristian Monsen // that indicate free regions. 12480d68eab642096c1a48b6474d6ec33064b0ad1f5Kristian Monsen static const uint32_t kSingleFreeEncoding = 0; 12580d68eab642096c1a48b6474d6ec33064b0ad1f5Kristian Monsen static const uint32_t kMultiFreeEncoding = 1; 12680d68eab642096c1a48b6474d6ec33064b0ad1f5Kristian Monsen 127a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block private: 128a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block#ifdef DEBUG 129a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block enum CollectorState { 130a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block IDLE, 131a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block PREPARE_GC, 132a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block MARK_LIVE_OBJECTS, 133a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block SWEEP_SPACES, 134a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block ENCODE_FORWARDING_ADDRESSES, 135a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block UPDATE_POINTERS, 1367f4d5bd8c03935e2c0cd412e561b8fc5a6a880aeBen Murdoch RELOCATE_OBJECTS 137a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block }; 138a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block 139a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // The current stage of the collector. 140a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block static CollectorState state_; 141a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block#endif 142a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block 143a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // Global flag that forces a compaction. 144a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block static bool force_compaction_; 145a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block 146a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // Global flag indicating whether spaces were compacted on the last GC. 147a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block static bool compacting_collection_; 148a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block 149a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // Global flag indicating whether spaces will be compacted on the next GC. 150a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block static bool compact_on_next_gc_; 151a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block 152a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // The number of objects left marked at the end of the last completed full 153a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // GC (expected to be zero). 154a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block static int previous_marked_count_; 155a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block 156a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // A pointer to the current stack-allocated GC tracer object during a full 157a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // collection (NULL before and after). 158a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block static GCTracer* tracer_; 159a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block 160a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // Finishes GC, performs heap verification if enabled. 161a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block static void Finish(); 162a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block 163a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // ----------------------------------------------------------------------- 164a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // Phase 1: Marking live objects. 165a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // 166a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // Before: The heap has been prepared for garbage collection by 167a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // MarkCompactCollector::Prepare() and is otherwise in its 168a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // normal state. 169a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // 170a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // After: Live objects are marked and non-live objects are unmarked. 171a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block 172a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block 173a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block friend class RootMarkingVisitor; 174a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block friend class MarkingVisitor; 175756813857a4c2a4d8ad2e805969d5768d3cf43a0Iain Merrick friend class StaticMarkingVisitor; 176756813857a4c2a4d8ad2e805969d5768d3cf43a0Iain Merrick friend class CodeMarkingVisitor; 177756813857a4c2a4d8ad2e805969d5768d3cf43a0Iain Merrick friend class SharedFunctionInfoMarkingVisitor; 178756813857a4c2a4d8ad2e805969d5768d3cf43a0Iain Merrick 179756813857a4c2a4d8ad2e805969d5768d3cf43a0Iain Merrick static void PrepareForCodeFlushing(); 180a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block 181a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // Marking operations for objects reachable from roots. 182a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block static void MarkLiveObjects(); 183a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block 184a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block static void MarkUnmarkedObject(HeapObject* obj); 185a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block 186a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block static inline void MarkObject(HeapObject* obj) { 187a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block if (!obj->IsMarked()) MarkUnmarkedObject(obj); 188a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block } 189a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block 190a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block static inline void SetMark(HeapObject* obj) { 191a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block tracer_->increment_marked_count(); 192a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block#ifdef DEBUG 193a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block UpdateLiveObjectCount(obj); 194a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block#endif 195a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block obj->SetMark(); 196a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block } 197a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block 198a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // Creates back pointers for all map transitions, stores them in 199a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // the prototype field. The original prototype pointers are restored 200a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // in ClearNonLiveTransitions(). All JSObject maps 201a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // connected by map transitions have the same prototype object, which 202a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // is why we can use this field temporarily for back pointers. 203a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block static void CreateBackPointers(); 204a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block 205a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // Mark a Map and its DescriptorArray together, skipping transitions. 206a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block static void MarkMapContents(Map* map); 207a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block static void MarkDescriptorArray(DescriptorArray* descriptors); 208a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block 209a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // Mark the heap roots and all objects reachable from them. 210a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block static void MarkRoots(RootMarkingVisitor* visitor); 211a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block 212a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // Mark the symbol table specially. References to symbols from the 213a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // symbol table are weak. 214a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block static void MarkSymbolTable(); 215a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block 216a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // Mark objects in object groups that have at least one object in the 217a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // group marked. 218a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block static void MarkObjectGroups(); 219a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block 220a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // Mark all objects in an object group with at least one marked 221a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // object, then all objects reachable from marked objects in object 222a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // groups, and repeat. 223756813857a4c2a4d8ad2e805969d5768d3cf43a0Iain Merrick static void ProcessObjectGroups(); 224a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block 225a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // Mark objects reachable (transitively) from objects in the marking stack 226a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // or overflowed in the heap. 227756813857a4c2a4d8ad2e805969d5768d3cf43a0Iain Merrick static void ProcessMarkingStack(); 228a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block 229a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // Mark objects reachable (transitively) from objects in the marking 230a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // stack. This function empties the marking stack, but may leave 231a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // overflowed objects in the heap, in which case the marking stack's 232a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // overflow flag will be set. 233756813857a4c2a4d8ad2e805969d5768d3cf43a0Iain Merrick static void EmptyMarkingStack(); 234a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block 235a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // Refill the marking stack with overflowed objects from the heap. This 236a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // function either leaves the marking stack full or clears the overflow 237a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // flag on the marking stack. 238a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block static void RefillMarkingStack(); 239a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block 240a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // Callback function for telling whether the object *p is an unmarked 241a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // heap object. 242a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block static bool IsUnmarkedHeapObject(Object** p); 243a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block 244a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block#ifdef DEBUG 245a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block static void UpdateLiveObjectCount(HeapObject* obj); 246a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block#endif 247a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block 248a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // We sweep the large object space in the same way whether we are 249a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // compacting or not, because the large object space is never compacted. 250a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block static void SweepLargeObjectSpace(); 251a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block 252a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // Test whether a (possibly marked) object is a Map. 253a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block static inline bool SafeIsMap(HeapObject* object); 254a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block 255a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // Map transitions from a live map to a dead map must be killed. 256a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // We replace them with a null descriptor, with the same key. 257a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block static void ClearNonLiveTransitions(); 258a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block 259a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // ----------------------------------------------------------------------- 260a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // Phase 2: Sweeping to clear mark bits and free non-live objects for 261a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // a non-compacting collection, or else computing and encoding 262a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // forwarding addresses for a compacting collection. 263a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // 264a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // Before: Live objects are marked and non-live objects are unmarked. 265a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // 266a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // After: (Non-compacting collection.) Live objects are unmarked, 267a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // non-live regions have been added to their space's free 268a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // list. 269a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // 270a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // After: (Compacting collection.) The forwarding address of live 271a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // objects in the paged spaces is encoded in their map word 272a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // along with their (non-forwarded) map pointer. 273a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // 274a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // The forwarding address of live objects in the new space is 275a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // written to their map word's offset in the inactive 276a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // semispace. 277a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // 2787f4d5bd8c03935e2c0cd412e561b8fc5a6a880aeBen Murdoch // Bookkeeping data is written to the page header of 279a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // eached paged-space page that contains live objects after 280a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // compaction: 281a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // 2827f4d5bd8c03935e2c0cd412e561b8fc5a6a880aeBen Murdoch // The allocation watermark field is used to track the 2837f4d5bd8c03935e2c0cd412e561b8fc5a6a880aeBen Murdoch // relocation top address, the address of the first word 2847f4d5bd8c03935e2c0cd412e561b8fc5a6a880aeBen Murdoch // after the end of the last live object in the page after 2857f4d5bd8c03935e2c0cd412e561b8fc5a6a880aeBen Murdoch // compaction. 286a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // 2877f4d5bd8c03935e2c0cd412e561b8fc5a6a880aeBen Murdoch // The Page::mc_page_index field contains the zero-based index of the 2887f4d5bd8c03935e2c0cd412e561b8fc5a6a880aeBen Murdoch // page in its space. This word is only used for map space pages, in 289a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // order to encode the map addresses in 21 bits to free 11 290a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // bits per map word for the forwarding address. 291a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // 2927f4d5bd8c03935e2c0cd412e561b8fc5a6a880aeBen Murdoch // The Page::mc_first_forwarded field contains the (nonencoded) 2937f4d5bd8c03935e2c0cd412e561b8fc5a6a880aeBen Murdoch // forwarding address of the first live object in the page. 294a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // 295a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // In both the new space and the paged spaces, a linked list 296a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // of live regions is constructructed (linked through 297a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // pointers in the non-live region immediately following each 298a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // live region) to speed further passes of the collector. 299a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block 300a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // Encodes forwarding addresses of objects in compactable parts of the 301a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // heap. 302a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block static void EncodeForwardingAddresses(); 303a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block 304a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // Encodes the forwarding addresses of objects in new space. 305a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block static void EncodeForwardingAddressesInNewSpace(); 306a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block 307a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // Function template to encode the forwarding addresses of objects in 308a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // paged spaces, parameterized by allocation and non-live processing 309a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // functions. 310a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block template<AllocationFunction Alloc, ProcessNonLiveFunction ProcessNonLive> 311a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block static void EncodeForwardingAddressesInPagedSpace(PagedSpace* space); 312a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block 313a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // Iterates live objects in a space, passes live objects 314a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // to a callback function which returns the heap size of the object. 315a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // Returns the number of live objects iterated. 316a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block static int IterateLiveObjects(NewSpace* space, HeapObjectCallback size_f); 317a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block static int IterateLiveObjects(PagedSpace* space, HeapObjectCallback size_f); 318a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block 319a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // Iterates the live objects between a range of addresses, returning the 320a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // number of live objects. 321a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block static int IterateLiveObjectsInRange(Address start, Address end, 322a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block HeapObjectCallback size_func); 323a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block 324a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // If we are not compacting the heap, we simply sweep the spaces except 325a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // for the large object space, clearing mark bits and adding unmarked 326a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // regions to each space's free list. 327a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block static void SweepSpaces(); 328a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block 329a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // ----------------------------------------------------------------------- 330a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // Phase 3: Updating pointers in live objects. 331a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // 332a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // Before: Same as after phase 2 (compacting collection). 333a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // 334a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // After: All pointers in live objects, including encoded map 335a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // pointers, are updated to point to their target's new 3367f4d5bd8c03935e2c0cd412e561b8fc5a6a880aeBen Murdoch // location. 337a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block 338a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block friend class UpdatingVisitor; // helper for updating visited objects 339a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block 340a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // Updates pointers in all spaces. 341a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block static void UpdatePointers(); 342a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block 343a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // Updates pointers in an object in new space. 344a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // Returns the heap size of the object. 345a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block static int UpdatePointersInNewObject(HeapObject* obj); 346a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block 347a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // Updates pointers in an object in old spaces. 348a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // Returns the heap size of the object. 349a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block static int UpdatePointersInOldObject(HeapObject* obj); 350a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block 351a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // Calculates the forwarding address of an object in an old space. 352a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block static Address GetForwardingAddressInOldSpace(HeapObject* obj); 353a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block 354a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // ----------------------------------------------------------------------- 355a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // Phase 4: Relocating objects. 356a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // 357a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // Before: Pointers to live objects are updated to point to their 3587f4d5bd8c03935e2c0cd412e561b8fc5a6a880aeBen Murdoch // target's new location. 359a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // 3607f4d5bd8c03935e2c0cd412e561b8fc5a6a880aeBen Murdoch // After: Objects have been moved to their new addresses. 361a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block 362a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // Relocates objects in all spaces. 363a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block static void RelocateObjects(); 364a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block 365a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // Converts a code object's inline target to addresses, convention from 366a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // address to target happens in the marking phase. 367a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block static int ConvertCodeICTargetToAddress(HeapObject* obj); 368a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block 369a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // Relocate a map object. 370a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block static int RelocateMapObject(HeapObject* obj); 371a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block 372a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // Relocates an old object. 373a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block static int RelocateOldPointerObject(HeapObject* obj); 374a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block static int RelocateOldDataObject(HeapObject* obj); 375a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block 376a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // Relocate a property cell object. 377a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block static int RelocateCellObject(HeapObject* obj); 378a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block 379a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // Helper function. 380a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block static inline int RelocateOldNonCodeObject(HeapObject* obj, 381a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block PagedSpace* space); 382a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block 383a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // Relocates an object in the code space. 384a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block static int RelocateCodeObject(HeapObject* obj); 385a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block 386a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // Copy a new object. 387a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block static int RelocateNewObject(HeapObject* obj); 388a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block 389a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block#ifdef DEBUG 390a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // ----------------------------------------------------------------------- 391a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // Debugging variables, functions and classes 392a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // Counters used for debugging the marking phase of mark-compact or 393a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // mark-sweep collection. 394a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block 3956ded16be15dd865a9b21ea304d5273c8be299c87Steve Block // Size of live objects in Heap::to_space_. 3966ded16be15dd865a9b21ea304d5273c8be299c87Steve Block static int live_young_objects_size_; 397a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block 3986ded16be15dd865a9b21ea304d5273c8be299c87Steve Block // Size of live objects in Heap::old_pointer_space_. 3996ded16be15dd865a9b21ea304d5273c8be299c87Steve Block static int live_old_pointer_objects_size_; 400a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block 4016ded16be15dd865a9b21ea304d5273c8be299c87Steve Block // Size of live objects in Heap::old_data_space_. 4026ded16be15dd865a9b21ea304d5273c8be299c87Steve Block static int live_old_data_objects_size_; 403a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block 4046ded16be15dd865a9b21ea304d5273c8be299c87Steve Block // Size of live objects in Heap::code_space_. 4056ded16be15dd865a9b21ea304d5273c8be299c87Steve Block static int live_code_objects_size_; 406a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block 4076ded16be15dd865a9b21ea304d5273c8be299c87Steve Block // Size of live objects in Heap::map_space_. 4086ded16be15dd865a9b21ea304d5273c8be299c87Steve Block static int live_map_objects_size_; 409a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block 4106ded16be15dd865a9b21ea304d5273c8be299c87Steve Block // Size of live objects in Heap::cell_space_. 4116ded16be15dd865a9b21ea304d5273c8be299c87Steve Block static int live_cell_objects_size_; 412a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block 4136ded16be15dd865a9b21ea304d5273c8be299c87Steve Block // Size of live objects in Heap::lo_space_. 4146ded16be15dd865a9b21ea304d5273c8be299c87Steve Block static int live_lo_objects_size_; 415a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block 416a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block // Number of live bytes in this collection. 417a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block static int live_bytes_; 418a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block 419a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block friend class MarkObjectVisitor; 420a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block static void VisitObject(HeapObject* obj); 421a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block 422a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block friend class UnmarkObjectVisitor; 423a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block static void UnmarkObject(HeapObject* obj); 424a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block#endif 425a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block}; 426a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block 427a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block 428a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block} } // namespace v8::internal 429a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block 430a7e24c173cf37484693b9abb38e494fa7bd7baebSteve Block#endif // V8_MARK_COMPACT_H_ 431