| // Copyright 2006-2008 the V8 project authors. All rights reserved. |
| // Redistribution and use in source and binary forms, with or without |
| // modification, are permitted provided that the following conditions are |
| // met: |
| // |
| // * Redistributions of source code must retain the above copyright |
| // notice, this list of conditions and the following disclaimer. |
| // * Redistributions in binary form must reproduce the above |
| // copyright notice, this list of conditions and the following |
| // disclaimer in the documentation and/or other materials provided |
| // with the distribution. |
| // * Neither the name of Google Inc. nor the names of its |
| // contributors may be used to endorse or promote products derived |
| // from this software without specific prior written permission. |
| // |
| // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS |
| // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT |
| // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR |
| // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT |
| // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, |
| // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT |
| // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, |
| // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY |
| // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT |
| // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE |
| // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
| |
| #include "v8.h" |
| |
| #include "compilation-cache.h" |
| #include "execution.h" |
| #include "heap-profiler.h" |
| #include "gdb-jit.h" |
| #include "global-handles.h" |
| #include "ic-inl.h" |
| #include "liveobjectlist-inl.h" |
| #include "mark-compact.h" |
| #include "objects-visiting.h" |
| #include "stub-cache.h" |
| |
| namespace v8 { |
| namespace internal { |
| |
| // ------------------------------------------------------------------------- |
| // MarkCompactCollector |
| |
| bool MarkCompactCollector::force_compaction_ = false; |
| bool MarkCompactCollector::compacting_collection_ = false; |
| bool MarkCompactCollector::compact_on_next_gc_ = false; |
| |
| int MarkCompactCollector::previous_marked_count_ = 0; |
| GCTracer* MarkCompactCollector::tracer_ = NULL; |
| |
| |
| #ifdef DEBUG |
| MarkCompactCollector::CollectorState MarkCompactCollector::state_ = IDLE; |
| |
| // Counters used for debugging the marking phase of mark-compact or mark-sweep |
| // collection. |
| int MarkCompactCollector::live_bytes_ = 0; |
| int MarkCompactCollector::live_young_objects_size_ = 0; |
| int MarkCompactCollector::live_old_data_objects_size_ = 0; |
| int MarkCompactCollector::live_old_pointer_objects_size_ = 0; |
| int MarkCompactCollector::live_code_objects_size_ = 0; |
| int MarkCompactCollector::live_map_objects_size_ = 0; |
| int MarkCompactCollector::live_cell_objects_size_ = 0; |
| int MarkCompactCollector::live_lo_objects_size_ = 0; |
| #endif |
| |
| |
| void MarkCompactCollector::CollectGarbage() { |
| // Make sure that Prepare() has been called. The individual steps below will |
| // update the state as they proceed. |
| ASSERT(state_ == PREPARE_GC); |
| |
| // Prepare has selected whether to compact the old generation or not. |
| // Tell the tracer. |
| if (IsCompacting()) tracer_->set_is_compacting(); |
| |
| MarkLiveObjects(); |
| |
| if (FLAG_collect_maps) ClearNonLiveTransitions(); |
| |
| SweepLargeObjectSpace(); |
| |
| if (IsCompacting()) { |
| GCTracer::Scope gc_scope(tracer_, GCTracer::Scope::MC_COMPACT); |
| EncodeForwardingAddresses(); |
| |
| Heap::MarkMapPointersAsEncoded(true); |
| UpdatePointers(); |
| Heap::MarkMapPointersAsEncoded(false); |
| PcToCodeCache::FlushPcToCodeCache(); |
| |
| RelocateObjects(); |
| } else { |
| SweepSpaces(); |
| PcToCodeCache::FlushPcToCodeCache(); |
| } |
| |
| Finish(); |
| |
| // Save the count of marked objects remaining after the collection and |
| // null out the GC tracer. |
| previous_marked_count_ = tracer_->marked_count(); |
| ASSERT(previous_marked_count_ == 0); |
| tracer_ = NULL; |
| } |
| |
| |
| void MarkCompactCollector::Prepare(GCTracer* tracer) { |
| // Rather than passing the tracer around we stash it in a static member |
| // variable. |
| tracer_ = tracer; |
| |
| #ifdef DEBUG |
| ASSERT(state_ == IDLE); |
| state_ = PREPARE_GC; |
| #endif |
| ASSERT(!FLAG_always_compact || !FLAG_never_compact); |
| |
| compacting_collection_ = |
| FLAG_always_compact || force_compaction_ || compact_on_next_gc_; |
| compact_on_next_gc_ = false; |
| |
| if (FLAG_never_compact) compacting_collection_ = false; |
| if (!Heap::map_space()->MapPointersEncodable()) |
| compacting_collection_ = false; |
| if (FLAG_collect_maps) CreateBackPointers(); |
| #ifdef ENABLE_GDB_JIT_INTERFACE |
| if (FLAG_gdbjit) { |
| // If GDBJIT interface is active disable compaction. |
| compacting_collection_ = false; |
| } |
| #endif |
| |
| PagedSpaces spaces; |
| for (PagedSpace* space = spaces.next(); |
| space != NULL; space = spaces.next()) { |
| space->PrepareForMarkCompact(compacting_collection_); |
| } |
| |
| #ifdef DEBUG |
| live_bytes_ = 0; |
| live_young_objects_size_ = 0; |
| live_old_pointer_objects_size_ = 0; |
| live_old_data_objects_size_ = 0; |
| live_code_objects_size_ = 0; |
| live_map_objects_size_ = 0; |
| live_cell_objects_size_ = 0; |
| live_lo_objects_size_ = 0; |
| #endif |
| } |
| |
| |
| void MarkCompactCollector::Finish() { |
| #ifdef DEBUG |
| ASSERT(state_ == SWEEP_SPACES || state_ == RELOCATE_OBJECTS); |
| state_ = IDLE; |
| #endif |
| // The stub cache is not traversed during GC; clear the cache to |
| // force lazy re-initialization of it. This must be done after the |
| // GC, because it relies on the new address of certain old space |
| // objects (empty string, illegal builtin). |
| StubCache::Clear(); |
| |
| ExternalStringTable::CleanUp(); |
| |
| // If we've just compacted old space there's no reason to check the |
| // fragmentation limit. Just return. |
| if (HasCompacted()) return; |
| |
| // We compact the old generation on the next GC if it has gotten too |
| // fragmented (ie, we could recover an expected amount of space by |
| // reclaiming the waste and free list blocks). |
| static const int kFragmentationLimit = 15; // Percent. |
| static const int kFragmentationAllowed = 1 * MB; // Absolute. |
| intptr_t old_gen_recoverable = 0; |
| intptr_t old_gen_used = 0; |
| |
| OldSpaces spaces; |
| for (OldSpace* space = spaces.next(); space != NULL; space = spaces.next()) { |
| old_gen_recoverable += space->Waste() + space->AvailableFree(); |
| old_gen_used += space->Size(); |
| } |
| |
| int old_gen_fragmentation = |
| static_cast<int>((old_gen_recoverable * 100.0) / old_gen_used); |
| if (old_gen_fragmentation > kFragmentationLimit && |
| old_gen_recoverable > kFragmentationAllowed) { |
| compact_on_next_gc_ = true; |
| } |
| } |
| |
| |
| // ------------------------------------------------------------------------- |
| // Phase 1: tracing and marking live objects. |
| // before: all objects are in normal state. |
| // after: a live object's map pointer is marked as '00'. |
| |
| // Marking all live objects in the heap as part of mark-sweep or mark-compact |
| // collection. Before marking, all objects are in their normal state. After |
| // marking, live objects' map pointers are marked indicating that the object |
| // has been found reachable. |
| // |
| // The marking algorithm is a (mostly) depth-first (because of possible stack |
| // overflow) traversal of the graph of objects reachable from the roots. It |
| // uses an explicit stack of pointers rather than recursion. The young |
| // generation's inactive ('from') space is used as a marking stack. The |
| // objects in the marking stack are the ones that have been reached and marked |
| // but their children have not yet been visited. |
| // |
| // The marking stack can overflow during traversal. In that case, we set an |
| // overflow flag. When the overflow flag is set, we continue marking objects |
| // reachable from the objects on the marking stack, but no longer push them on |
| // the marking stack. Instead, we mark them as both marked and overflowed. |
| // When the stack is in the overflowed state, objects marked as overflowed |
| // have been reached and marked but their children have not been visited yet. |
| // After emptying the marking stack, we clear the overflow flag and traverse |
| // the heap looking for objects marked as overflowed, push them on the stack, |
| // and continue with marking. This process repeats until all reachable |
| // objects have been marked. |
| |
| static MarkingStack marking_stack; |
| |
| class FlushCode : public AllStatic { |
| public: |
| static void AddCandidate(SharedFunctionInfo* shared_info) { |
| SetNextCandidate(shared_info, shared_function_info_candidates_head_); |
| shared_function_info_candidates_head_ = shared_info; |
| } |
| |
| |
| static void AddCandidate(JSFunction* function) { |
| ASSERT(function->unchecked_code() == |
| function->unchecked_shared()->unchecked_code()); |
| |
| SetNextCandidate(function, jsfunction_candidates_head_); |
| jsfunction_candidates_head_ = function; |
| } |
| |
| |
| static void ProcessCandidates() { |
| ProcessSharedFunctionInfoCandidates(); |
| ProcessJSFunctionCandidates(); |
| } |
| |
| private: |
| static void ProcessJSFunctionCandidates() { |
| Code* lazy_compile = Builtins::builtin(Builtins::LazyCompile); |
| |
| JSFunction* candidate = jsfunction_candidates_head_; |
| JSFunction* next_candidate; |
| while (candidate != NULL) { |
| next_candidate = GetNextCandidate(candidate); |
| |
| SharedFunctionInfo* shared = candidate->unchecked_shared(); |
| |
| Code* code = shared->unchecked_code(); |
| if (!code->IsMarked()) { |
| shared->set_code(lazy_compile); |
| candidate->set_code(lazy_compile); |
| } else { |
| candidate->set_code(shared->unchecked_code()); |
| } |
| |
| candidate = next_candidate; |
| } |
| |
| jsfunction_candidates_head_ = NULL; |
| } |
| |
| |
| static void ProcessSharedFunctionInfoCandidates() { |
| Code* lazy_compile = Builtins::builtin(Builtins::LazyCompile); |
| |
| SharedFunctionInfo* candidate = shared_function_info_candidates_head_; |
| SharedFunctionInfo* next_candidate; |
| while (candidate != NULL) { |
| next_candidate = GetNextCandidate(candidate); |
| SetNextCandidate(candidate, NULL); |
| |
| Code* code = candidate->unchecked_code(); |
| if (!code->IsMarked()) { |
| candidate->set_code(lazy_compile); |
| } |
| |
| candidate = next_candidate; |
| } |
| |
| shared_function_info_candidates_head_ = NULL; |
| } |
| |
| |
| static JSFunction** GetNextCandidateField(JSFunction* candidate) { |
| return reinterpret_cast<JSFunction**>( |
| candidate->address() + JSFunction::kCodeEntryOffset); |
| } |
| |
| |
| static JSFunction* GetNextCandidate(JSFunction* candidate) { |
| return *GetNextCandidateField(candidate); |
| } |
| |
| |
| static void SetNextCandidate(JSFunction* candidate, |
| JSFunction* next_candidate) { |
| *GetNextCandidateField(candidate) = next_candidate; |
| } |
| |
| |
| STATIC_ASSERT(kPointerSize <= Code::kHeaderSize - Code::kHeaderPaddingStart); |
| |
| |
| static SharedFunctionInfo** GetNextCandidateField( |
| SharedFunctionInfo* candidate) { |
| Code* code = candidate->unchecked_code(); |
| return reinterpret_cast<SharedFunctionInfo**>( |
| code->address() + Code::kHeaderPaddingStart); |
| } |
| |
| |
| static SharedFunctionInfo* GetNextCandidate(SharedFunctionInfo* candidate) { |
| return *GetNextCandidateField(candidate); |
| } |
| |
| |
| static void SetNextCandidate(SharedFunctionInfo* candidate, |
| SharedFunctionInfo* next_candidate) { |
| *GetNextCandidateField(candidate) = next_candidate; |
| } |
| |
| static JSFunction* jsfunction_candidates_head_; |
| |
| static SharedFunctionInfo* shared_function_info_candidates_head_; |
| }; |
| |
| JSFunction* FlushCode::jsfunction_candidates_head_ = NULL; |
| |
| SharedFunctionInfo* FlushCode::shared_function_info_candidates_head_ = NULL; |
| |
| static inline HeapObject* ShortCircuitConsString(Object** p) { |
| // Optimization: If the heap object pointed to by p is a non-symbol |
| // cons string whose right substring is Heap::empty_string, update |
| // it in place to its left substring. Return the updated value. |
| // |
| // Here we assume that if we change *p, we replace it with a heap object |
| // (ie, the left substring of a cons string is always a heap object). |
| // |
| // The check performed is: |
| // object->IsConsString() && !object->IsSymbol() && |
| // (ConsString::cast(object)->second() == Heap::empty_string()) |
| // except the maps for the object and its possible substrings might be |
| // marked. |
| HeapObject* object = HeapObject::cast(*p); |
| MapWord map_word = object->map_word(); |
| map_word.ClearMark(); |
| InstanceType type = map_word.ToMap()->instance_type(); |
| if ((type & kShortcutTypeMask) != kShortcutTypeTag) return object; |
| |
| Object* second = reinterpret_cast<ConsString*>(object)->unchecked_second(); |
| if (second != Heap::raw_unchecked_empty_string()) { |
| return object; |
| } |
| |
| // Since we don't have the object's start, it is impossible to update the |
| // page dirty marks. Therefore, we only replace the string with its left |
| // substring when page dirty marks do not change. |
| Object* first = reinterpret_cast<ConsString*>(object)->unchecked_first(); |
| if (!Heap::InNewSpace(object) && Heap::InNewSpace(first)) return object; |
| |
| *p = first; |
| return HeapObject::cast(first); |
| } |
| |
| |
| class StaticMarkingVisitor : public StaticVisitorBase { |
| public: |
| static inline void IterateBody(Map* map, HeapObject* obj) { |
| table_.GetVisitor(map)(map, obj); |
| } |
| |
| static void EnableCodeFlushing(bool enabled) { |
| if (enabled) { |
| table_.Register(kVisitJSFunction, &VisitJSFunctionAndFlushCode); |
| table_.Register(kVisitSharedFunctionInfo, |
| &VisitSharedFunctionInfoAndFlushCode); |
| |
| } else { |
| table_.Register(kVisitJSFunction, &VisitJSFunction); |
| table_.Register(kVisitSharedFunctionInfo, |
| &VisitSharedFunctionInfoGeneric); |
| } |
| } |
| |
| static void Initialize() { |
| table_.Register(kVisitShortcutCandidate, |
| &FixedBodyVisitor<StaticMarkingVisitor, |
| ConsString::BodyDescriptor, |
| void>::Visit); |
| |
| table_.Register(kVisitConsString, |
| &FixedBodyVisitor<StaticMarkingVisitor, |
| ConsString::BodyDescriptor, |
| void>::Visit); |
| |
| |
| table_.Register(kVisitFixedArray, |
| &FlexibleBodyVisitor<StaticMarkingVisitor, |
| FixedArray::BodyDescriptor, |
| void>::Visit); |
| |
| table_.Register(kVisitGlobalContext, |
| &FixedBodyVisitor<StaticMarkingVisitor, |
| Context::MarkCompactBodyDescriptor, |
| void>::Visit); |
| |
| table_.Register(kVisitByteArray, &DataObjectVisitor::Visit); |
| table_.Register(kVisitSeqAsciiString, &DataObjectVisitor::Visit); |
| table_.Register(kVisitSeqTwoByteString, &DataObjectVisitor::Visit); |
| |
| table_.Register(kVisitOddball, |
| &FixedBodyVisitor<StaticMarkingVisitor, |
| Oddball::BodyDescriptor, |
| void>::Visit); |
| table_.Register(kVisitMap, |
| &FixedBodyVisitor<StaticMarkingVisitor, |
| Map::BodyDescriptor, |
| void>::Visit); |
| |
| table_.Register(kVisitCode, &VisitCode); |
| |
| table_.Register(kVisitSharedFunctionInfo, |
| &VisitSharedFunctionInfoAndFlushCode); |
| |
| table_.Register(kVisitJSFunction, |
| &VisitJSFunctionAndFlushCode); |
| |
| table_.Register(kVisitPropertyCell, |
| &FixedBodyVisitor<StaticMarkingVisitor, |
| JSGlobalPropertyCell::BodyDescriptor, |
| void>::Visit); |
| |
| table_.RegisterSpecializations<DataObjectVisitor, |
| kVisitDataObject, |
| kVisitDataObjectGeneric>(); |
| |
| table_.RegisterSpecializations<JSObjectVisitor, |
| kVisitJSObject, |
| kVisitJSObjectGeneric>(); |
| |
| table_.RegisterSpecializations<StructObjectVisitor, |
| kVisitStruct, |
| kVisitStructGeneric>(); |
| } |
| |
| INLINE(static void VisitPointer(Object** p)) { |
| MarkObjectByPointer(p); |
| } |
| |
| INLINE(static void VisitPointers(Object** start, Object** end)) { |
| // Mark all objects pointed to in [start, end). |
| const int kMinRangeForMarkingRecursion = 64; |
| if (end - start >= kMinRangeForMarkingRecursion) { |
| if (VisitUnmarkedObjects(start, end)) return; |
| // We are close to a stack overflow, so just mark the objects. |
| } |
| for (Object** p = start; p < end; p++) MarkObjectByPointer(p); |
| } |
| |
| static inline void VisitCodeTarget(RelocInfo* rinfo) { |
| ASSERT(RelocInfo::IsCodeTarget(rinfo->rmode())); |
| Code* code = Code::GetCodeFromTargetAddress(rinfo->target_address()); |
| if (FLAG_cleanup_ics_at_gc && code->is_inline_cache_stub()) { |
| IC::Clear(rinfo->pc()); |
| // Please note targets for cleared inline cached do not have to be |
| // marked since they are contained in Heap::non_monomorphic_cache(). |
| } else { |
| MarkCompactCollector::MarkObject(code); |
| } |
| } |
| |
| static void VisitGlobalPropertyCell(RelocInfo* rinfo) { |
| ASSERT(rinfo->rmode() == RelocInfo::GLOBAL_PROPERTY_CELL); |
| Object* cell = rinfo->target_cell(); |
| Object* old_cell = cell; |
| VisitPointer(&cell); |
| if (cell != old_cell) { |
| rinfo->set_target_cell(reinterpret_cast<JSGlobalPropertyCell*>(cell)); |
| } |
| } |
| |
| static inline void VisitDebugTarget(RelocInfo* rinfo) { |
| ASSERT((RelocInfo::IsJSReturn(rinfo->rmode()) && |
| rinfo->IsPatchedReturnSequence()) || |
| (RelocInfo::IsDebugBreakSlot(rinfo->rmode()) && |
| rinfo->IsPatchedDebugBreakSlotSequence())); |
| HeapObject* code = Code::GetCodeFromTargetAddress(rinfo->call_address()); |
| MarkCompactCollector::MarkObject(code); |
| } |
| |
| // Mark object pointed to by p. |
| INLINE(static void MarkObjectByPointer(Object** p)) { |
| if (!(*p)->IsHeapObject()) return; |
| HeapObject* object = ShortCircuitConsString(p); |
| MarkCompactCollector::MarkObject(object); |
| } |
| |
| // Visit an unmarked object. |
| static inline void VisitUnmarkedObject(HeapObject* obj) { |
| #ifdef DEBUG |
| ASSERT(Heap::Contains(obj)); |
| ASSERT(!obj->IsMarked()); |
| #endif |
| Map* map = obj->map(); |
| MarkCompactCollector::SetMark(obj); |
| // Mark the map pointer and the body. |
| MarkCompactCollector::MarkObject(map); |
| IterateBody(map, obj); |
| } |
| |
| // Visit all unmarked objects pointed to by [start, end). |
| // Returns false if the operation fails (lack of stack space). |
| static inline bool VisitUnmarkedObjects(Object** start, Object** end) { |
| // Return false is we are close to the stack limit. |
| StackLimitCheck check; |
| if (check.HasOverflowed()) return false; |
| |
| // Visit the unmarked objects. |
| for (Object** p = start; p < end; p++) { |
| if (!(*p)->IsHeapObject()) continue; |
| HeapObject* obj = HeapObject::cast(*p); |
| if (obj->IsMarked()) continue; |
| VisitUnmarkedObject(obj); |
| } |
| return true; |
| } |
| |
| static inline void VisitExternalReference(Address* p) { } |
| static inline void VisitRuntimeEntry(RelocInfo* rinfo) { } |
| |
| private: |
| class DataObjectVisitor { |
| public: |
| template<int size> |
| static void VisitSpecialized(Map* map, HeapObject* object) { |
| } |
| |
| static void Visit(Map* map, HeapObject* object) { |
| } |
| }; |
| |
| typedef FlexibleBodyVisitor<StaticMarkingVisitor, |
| JSObject::BodyDescriptor, |
| void> JSObjectVisitor; |
| |
| typedef FlexibleBodyVisitor<StaticMarkingVisitor, |
| StructBodyDescriptor, |
| void> StructObjectVisitor; |
| |
| static void VisitCode(Map* map, HeapObject* object) { |
| reinterpret_cast<Code*>(object)->CodeIterateBody<StaticMarkingVisitor>(); |
| } |
| |
| // Code flushing support. |
| |
| // How many collections newly compiled code object will survive before being |
| // flushed. |
| static const int kCodeAgeThreshold = 5; |
| |
| inline static bool HasSourceCode(SharedFunctionInfo* info) { |
| Object* undefined = Heap::raw_unchecked_undefined_value(); |
| return (info->script() != undefined) && |
| (reinterpret_cast<Script*>(info->script())->source() != undefined); |
| } |
| |
| |
| inline static bool IsCompiled(JSFunction* function) { |
| return |
| function->unchecked_code() != Builtins::builtin(Builtins::LazyCompile); |
| } |
| |
| |
| inline static bool IsCompiled(SharedFunctionInfo* function) { |
| return |
| function->unchecked_code() != Builtins::builtin(Builtins::LazyCompile); |
| } |
| |
| inline static bool IsFlushable(JSFunction* function) { |
| SharedFunctionInfo* shared_info = function->unchecked_shared(); |
| |
| // Code is either on stack, in compilation cache or referenced |
| // by optimized version of function. |
| if (function->unchecked_code()->IsMarked()) { |
| shared_info->set_code_age(0); |
| return false; |
| } |
| |
| // We do not flush code for optimized functions. |
| if (function->code() != shared_info->unchecked_code()) { |
| return false; |
| } |
| |
| return IsFlushable(shared_info); |
| } |
| |
| inline static bool IsFlushable(SharedFunctionInfo* shared_info) { |
| // Code is either on stack, in compilation cache or referenced |
| // by optimized version of function. |
| if (shared_info->unchecked_code()->IsMarked()) { |
| shared_info->set_code_age(0); |
| return false; |
| } |
| |
| // The function must be compiled and have the source code available, |
| // to be able to recompile it in case we need the function again. |
| if (!(shared_info->is_compiled() && HasSourceCode(shared_info))) { |
| return false; |
| } |
| |
| // We never flush code for Api functions. |
| Object* function_data = shared_info->function_data(); |
| if (function_data->IsHeapObject() && |
| (SafeMap(function_data)->instance_type() == |
| FUNCTION_TEMPLATE_INFO_TYPE)) { |
| return false; |
| } |
| |
| // Only flush code for functions. |
| if (shared_info->code()->kind() != Code::FUNCTION) return false; |
| |
| // Function must be lazy compilable. |
| if (!shared_info->allows_lazy_compilation()) return false; |
| |
| // If this is a full script wrapped in a function we do no flush the code. |
| if (shared_info->is_toplevel()) return false; |
| |
| // Age this shared function info. |
| if (shared_info->code_age() < kCodeAgeThreshold) { |
| shared_info->set_code_age(shared_info->code_age() + 1); |
| return false; |
| } |
| |
| return true; |
| } |
| |
| |
| static bool FlushCodeForFunction(JSFunction* function) { |
| if (!IsFlushable(function)) return false; |
| |
| // This function's code looks flushable. But we have to postpone the |
| // decision until we see all functions that point to the same |
| // SharedFunctionInfo because some of them might be optimized. |
| // That would make the nonoptimized version of the code nonflushable, |
| // because it is required for bailing out from optimized code. |
| FlushCode::AddCandidate(function); |
| return true; |
| } |
| |
| |
| static inline Map* SafeMap(Object* obj) { |
| MapWord map_word = HeapObject::cast(obj)->map_word(); |
| map_word.ClearMark(); |
| map_word.ClearOverflow(); |
| return map_word.ToMap(); |
| } |
| |
| |
| static inline bool IsJSBuiltinsObject(Object* obj) { |
| return obj->IsHeapObject() && |
| (SafeMap(obj)->instance_type() == JS_BUILTINS_OBJECT_TYPE); |
| } |
| |
| |
| static inline bool IsValidNotBuiltinContext(Object* ctx) { |
| if (!ctx->IsHeapObject()) return false; |
| |
| Map* map = SafeMap(ctx); |
| if (!(map == Heap::raw_unchecked_context_map() || |
| map == Heap::raw_unchecked_catch_context_map() || |
| map == Heap::raw_unchecked_global_context_map())) { |
| return false; |
| } |
| |
| Context* context = reinterpret_cast<Context*>(ctx); |
| |
| if (IsJSBuiltinsObject(context->global())) { |
| return false; |
| } |
| |
| return true; |
| } |
| |
| |
| static void VisitSharedFunctionInfoGeneric(Map* map, HeapObject* object) { |
| SharedFunctionInfo* shared = reinterpret_cast<SharedFunctionInfo*>(object); |
| |
| if (shared->IsInobjectSlackTrackingInProgress()) shared->DetachInitialMap(); |
| |
| FixedBodyVisitor<StaticMarkingVisitor, |
| SharedFunctionInfo::BodyDescriptor, |
| void>::Visit(map, object); |
| } |
| |
| |
| static void VisitSharedFunctionInfoAndFlushCode(Map* map, |
| HeapObject* object) { |
| VisitSharedFunctionInfoAndFlushCodeGeneric(map, object, false); |
| } |
| |
| |
| static void VisitSharedFunctionInfoAndFlushCodeGeneric( |
| Map* map, HeapObject* object, bool known_flush_code_candidate) { |
| SharedFunctionInfo* shared = reinterpret_cast<SharedFunctionInfo*>(object); |
| |
| if (shared->IsInobjectSlackTrackingInProgress()) shared->DetachInitialMap(); |
| |
| if (!known_flush_code_candidate) { |
| known_flush_code_candidate = IsFlushable(shared); |
| if (known_flush_code_candidate) FlushCode::AddCandidate(shared); |
| } |
| |
| VisitSharedFunctionInfoFields(object, known_flush_code_candidate); |
| } |
| |
| |
| static void VisitCodeEntry(Address entry_address) { |
| Object* code = Code::GetObjectFromEntryAddress(entry_address); |
| Object* old_code = code; |
| VisitPointer(&code); |
| if (code != old_code) { |
| Memory::Address_at(entry_address) = |
| reinterpret_cast<Code*>(code)->entry(); |
| } |
| } |
| |
| |
| static void VisitJSFunctionAndFlushCode(Map* map, HeapObject* object) { |
| JSFunction* jsfunction = reinterpret_cast<JSFunction*>(object); |
| // The function must have a valid context and not be a builtin. |
| bool flush_code_candidate = false; |
| if (IsValidNotBuiltinContext(jsfunction->unchecked_context())) { |
| flush_code_candidate = FlushCodeForFunction(jsfunction); |
| } |
| |
| if (!flush_code_candidate) { |
| MarkCompactCollector::MarkObject( |
| jsfunction->unchecked_shared()->unchecked_code()); |
| |
| if (jsfunction->unchecked_code()->kind() == Code::OPTIMIZED_FUNCTION) { |
| // For optimized functions we should retain both non-optimized version |
| // of it's code and non-optimized version of all inlined functions. |
| // This is required to support bailing out from inlined code. |
| DeoptimizationInputData* data = |
| reinterpret_cast<DeoptimizationInputData*>( |
| jsfunction->unchecked_code()->unchecked_deoptimization_data()); |
| |
| FixedArray* literals = data->UncheckedLiteralArray(); |
| |
| for (int i = 0, count = data->InlinedFunctionCount()->value(); |
| i < count; |
| i++) { |
| JSFunction* inlined = reinterpret_cast<JSFunction*>(literals->get(i)); |
| MarkCompactCollector::MarkObject( |
| inlined->unchecked_shared()->unchecked_code()); |
| } |
| } |
| } |
| |
| VisitJSFunctionFields(map, |
| reinterpret_cast<JSFunction*>(object), |
| flush_code_candidate); |
| } |
| |
| |
| static void VisitJSFunction(Map* map, HeapObject* object) { |
| VisitJSFunctionFields(map, |
| reinterpret_cast<JSFunction*>(object), |
| false); |
| } |
| |
| |
| #define SLOT_ADDR(obj, offset) \ |
| reinterpret_cast<Object**>((obj)->address() + offset) |
| |
| |
| static inline void VisitJSFunctionFields(Map* map, |
| JSFunction* object, |
| bool flush_code_candidate) { |
| VisitPointers(SLOT_ADDR(object, JSFunction::kPropertiesOffset), |
| SLOT_ADDR(object, JSFunction::kCodeEntryOffset)); |
| |
| if (!flush_code_candidate) { |
| VisitCodeEntry(object->address() + JSFunction::kCodeEntryOffset); |
| } else { |
| // Don't visit code object. |
| |
| // Visit shared function info to avoid double checking of it's |
| // flushability. |
| SharedFunctionInfo* shared_info = object->unchecked_shared(); |
| if (!shared_info->IsMarked()) { |
| Map* shared_info_map = shared_info->map(); |
| MarkCompactCollector::SetMark(shared_info); |
| MarkCompactCollector::MarkObject(shared_info_map); |
| VisitSharedFunctionInfoAndFlushCodeGeneric(shared_info_map, |
| shared_info, |
| true); |
| } |
| } |
| |
| VisitPointers(SLOT_ADDR(object, |
| JSFunction::kCodeEntryOffset + kPointerSize), |
| SLOT_ADDR(object, JSFunction::kNonWeakFieldsEndOffset)); |
| |
| // Don't visit the next function list field as it is a weak reference. |
| } |
| |
| |
| static void VisitSharedFunctionInfoFields(HeapObject* object, |
| bool flush_code_candidate) { |
| VisitPointer(SLOT_ADDR(object, SharedFunctionInfo::kNameOffset)); |
| |
| if (!flush_code_candidate) { |
| VisitPointer(SLOT_ADDR(object, SharedFunctionInfo::kCodeOffset)); |
| } |
| |
| VisitPointers(SLOT_ADDR(object, SharedFunctionInfo::kScopeInfoOffset), |
| SLOT_ADDR(object, SharedFunctionInfo::kSize)); |
| } |
| |
| #undef SLOT_ADDR |
| |
| typedef void (*Callback)(Map* map, HeapObject* object); |
| |
| static VisitorDispatchTable<Callback> table_; |
| }; |
| |
| |
| VisitorDispatchTable<StaticMarkingVisitor::Callback> |
| StaticMarkingVisitor::table_; |
| |
| |
| class MarkingVisitor : public ObjectVisitor { |
| public: |
| void VisitPointer(Object** p) { |
| StaticMarkingVisitor::VisitPointer(p); |
| } |
| |
| void VisitPointers(Object** start, Object** end) { |
| StaticMarkingVisitor::VisitPointers(start, end); |
| } |
| |
| void VisitCodeTarget(RelocInfo* rinfo) { |
| StaticMarkingVisitor::VisitCodeTarget(rinfo); |
| } |
| |
| void VisitGlobalPropertyCell(RelocInfo* rinfo) { |
| StaticMarkingVisitor::VisitGlobalPropertyCell(rinfo); |
| } |
| |
| void VisitDebugTarget(RelocInfo* rinfo) { |
| StaticMarkingVisitor::VisitDebugTarget(rinfo); |
| } |
| }; |
| |
| |
| class CodeMarkingVisitor : public ThreadVisitor { |
| public: |
| void VisitThread(ThreadLocalTop* top) { |
| for (StackFrameIterator it(top); !it.done(); it.Advance()) { |
| MarkCompactCollector::MarkObject(it.frame()->unchecked_code()); |
| } |
| } |
| }; |
| |
| |
| class SharedFunctionInfoMarkingVisitor : public ObjectVisitor { |
| public: |
| void VisitPointers(Object** start, Object** end) { |
| for (Object** p = start; p < end; p++) VisitPointer(p); |
| } |
| |
| void VisitPointer(Object** slot) { |
| Object* obj = *slot; |
| if (obj->IsSharedFunctionInfo()) { |
| SharedFunctionInfo* shared = reinterpret_cast<SharedFunctionInfo*>(obj); |
| MarkCompactCollector::MarkObject(shared->unchecked_code()); |
| MarkCompactCollector::MarkObject(shared); |
| } |
| } |
| }; |
| |
| |
| void MarkCompactCollector::PrepareForCodeFlushing() { |
| if (!FLAG_flush_code) { |
| StaticMarkingVisitor::EnableCodeFlushing(false); |
| return; |
| } |
| |
| #ifdef ENABLE_DEBUGGER_SUPPORT |
| if (Debug::IsLoaded() || Debug::has_break_points()) { |
| StaticMarkingVisitor::EnableCodeFlushing(false); |
| return; |
| } |
| #endif |
| StaticMarkingVisitor::EnableCodeFlushing(true); |
| |
| // Ensure that empty descriptor array is marked. Method MarkDescriptorArray |
| // relies on it being marked before any other descriptor array. |
| MarkObject(Heap::raw_unchecked_empty_descriptor_array()); |
| |
| // Make sure we are not referencing the code from the stack. |
| for (StackFrameIterator it; !it.done(); it.Advance()) { |
| MarkObject(it.frame()->unchecked_code()); |
| } |
| |
| // Iterate the archived stacks in all threads to check if |
| // the code is referenced. |
| CodeMarkingVisitor code_marking_visitor; |
| ThreadManager::IterateArchivedThreads(&code_marking_visitor); |
| |
| SharedFunctionInfoMarkingVisitor visitor; |
| CompilationCache::IterateFunctions(&visitor); |
| HandleScopeImplementer::Iterate(&visitor); |
| |
| ProcessMarkingStack(); |
| } |
| |
| |
| // Visitor class for marking heap roots. |
| class RootMarkingVisitor : public ObjectVisitor { |
| public: |
| void VisitPointer(Object** p) { |
| MarkObjectByPointer(p); |
| } |
| |
| void VisitPointers(Object** start, Object** end) { |
| for (Object** p = start; p < end; p++) MarkObjectByPointer(p); |
| } |
| |
| private: |
| void MarkObjectByPointer(Object** p) { |
| if (!(*p)->IsHeapObject()) return; |
| |
| // Replace flat cons strings in place. |
| HeapObject* object = ShortCircuitConsString(p); |
| if (object->IsMarked()) return; |
| |
| Map* map = object->map(); |
| // Mark the object. |
| MarkCompactCollector::SetMark(object); |
| |
| // Mark the map pointer and body, and push them on the marking stack. |
| MarkCompactCollector::MarkObject(map); |
| StaticMarkingVisitor::IterateBody(map, object); |
| |
| // Mark all the objects reachable from the map and body. May leave |
| // overflowed objects in the heap. |
| MarkCompactCollector::EmptyMarkingStack(); |
| } |
| }; |
| |
| |
| // Helper class for pruning the symbol table. |
| class SymbolTableCleaner : public ObjectVisitor { |
| public: |
| SymbolTableCleaner() : pointers_removed_(0) { } |
| |
| virtual void VisitPointers(Object** start, Object** end) { |
| // Visit all HeapObject pointers in [start, end). |
| for (Object** p = start; p < end; p++) { |
| if ((*p)->IsHeapObject() && !HeapObject::cast(*p)->IsMarked()) { |
| // Check if the symbol being pruned is an external symbol. We need to |
| // delete the associated external data as this symbol is going away. |
| |
| // Since no objects have yet been moved we can safely access the map of |
| // the object. |
| if ((*p)->IsExternalString()) { |
| Heap::FinalizeExternalString(String::cast(*p)); |
| } |
| // Set the entry to null_value (as deleted). |
| *p = Heap::raw_unchecked_null_value(); |
| pointers_removed_++; |
| } |
| } |
| } |
| |
| int PointersRemoved() { |
| return pointers_removed_; |
| } |
| private: |
| int pointers_removed_; |
| }; |
| |
| |
| // Implementation of WeakObjectRetainer for mark compact GCs. All marked objects |
| // are retained. |
| class MarkCompactWeakObjectRetainer : public WeakObjectRetainer { |
| public: |
| virtual Object* RetainAs(Object* object) { |
| MapWord first_word = HeapObject::cast(object)->map_word(); |
| if (first_word.IsMarked()) { |
| return object; |
| } else { |
| return NULL; |
| } |
| } |
| }; |
| |
| |
| void MarkCompactCollector::MarkUnmarkedObject(HeapObject* object) { |
| ASSERT(!object->IsMarked()); |
| ASSERT(Heap::Contains(object)); |
| if (object->IsMap()) { |
| Map* map = Map::cast(object); |
| if (FLAG_cleanup_caches_in_maps_at_gc) { |
| map->ClearCodeCache(); |
| } |
| SetMark(map); |
| if (FLAG_collect_maps && |
| map->instance_type() >= FIRST_JS_OBJECT_TYPE && |
| map->instance_type() <= JS_FUNCTION_TYPE) { |
| MarkMapContents(map); |
| } else { |
| marking_stack.Push(map); |
| } |
| } else { |
| SetMark(object); |
| marking_stack.Push(object); |
| } |
| } |
| |
| |
| void MarkCompactCollector::MarkMapContents(Map* map) { |
| MarkDescriptorArray(reinterpret_cast<DescriptorArray*>( |
| *HeapObject::RawField(map, Map::kInstanceDescriptorsOffset))); |
| |
| // Mark the Object* fields of the Map. |
| // Since the descriptor array has been marked already, it is fine |
| // that one of these fields contains a pointer to it. |
| Object** start_slot = HeapObject::RawField(map, |
| Map::kPointerFieldsBeginOffset); |
| |
| Object** end_slot = HeapObject::RawField(map, Map::kPointerFieldsEndOffset); |
| |
| StaticMarkingVisitor::VisitPointers(start_slot, end_slot); |
| } |
| |
| |
| void MarkCompactCollector::MarkDescriptorArray( |
| DescriptorArray* descriptors) { |
| if (descriptors->IsMarked()) return; |
| // Empty descriptor array is marked as a root before any maps are marked. |
| ASSERT(descriptors != Heap::raw_unchecked_empty_descriptor_array()); |
| SetMark(descriptors); |
| |
| FixedArray* contents = reinterpret_cast<FixedArray*>( |
| descriptors->get(DescriptorArray::kContentArrayIndex)); |
| ASSERT(contents->IsHeapObject()); |
| ASSERT(!contents->IsMarked()); |
| ASSERT(contents->IsFixedArray()); |
| ASSERT(contents->length() >= 2); |
| SetMark(contents); |
| // Contents contains (value, details) pairs. If the details say that |
| // the type of descriptor is MAP_TRANSITION, CONSTANT_TRANSITION, or |
| // NULL_DESCRIPTOR, we don't mark the value as live. Only for |
| // MAP_TRANSITION and CONSTANT_TRANSITION is the value an Object* (a |
| // Map*). |
| for (int i = 0; i < contents->length(); i += 2) { |
| // If the pair (value, details) at index i, i+1 is not |
| // a transition or null descriptor, mark the value. |
| PropertyDetails details(Smi::cast(contents->get(i + 1))); |
| if (details.type() < FIRST_PHANTOM_PROPERTY_TYPE) { |
| HeapObject* object = reinterpret_cast<HeapObject*>(contents->get(i)); |
| if (object->IsHeapObject() && !object->IsMarked()) { |
| SetMark(object); |
| marking_stack.Push(object); |
| } |
| } |
| } |
| // The DescriptorArray descriptors contains a pointer to its contents array, |
| // but the contents array is already marked. |
| marking_stack.Push(descriptors); |
| } |
| |
| |
| void MarkCompactCollector::CreateBackPointers() { |
| HeapObjectIterator iterator(Heap::map_space()); |
| for (HeapObject* next_object = iterator.next(); |
| next_object != NULL; next_object = iterator.next()) { |
| if (next_object->IsMap()) { // Could also be ByteArray on free list. |
| Map* map = Map::cast(next_object); |
| if (map->instance_type() >= FIRST_JS_OBJECT_TYPE && |
| map->instance_type() <= JS_FUNCTION_TYPE) { |
| map->CreateBackPointers(); |
| } else { |
| ASSERT(map->instance_descriptors() == Heap::empty_descriptor_array()); |
| } |
| } |
| } |
| } |
| |
| |
| static int OverflowObjectSize(HeapObject* obj) { |
| // Recover the normal map pointer, it might be marked as live and |
| // overflowed. |
| MapWord map_word = obj->map_word(); |
| map_word.ClearMark(); |
| map_word.ClearOverflow(); |
| return obj->SizeFromMap(map_word.ToMap()); |
| } |
| |
| |
| // Fill the marking stack with overflowed objects returned by the given |
| // iterator. Stop when the marking stack is filled or the end of the space |
| // is reached, whichever comes first. |
| template<class T> |
| static void ScanOverflowedObjects(T* it) { |
| // The caller should ensure that the marking stack is initially not full, |
| // so that we don't waste effort pointlessly scanning for objects. |
| ASSERT(!marking_stack.is_full()); |
| |
| for (HeapObject* object = it->next(); object != NULL; object = it->next()) { |
| if (object->IsOverflowed()) { |
| object->ClearOverflow(); |
| ASSERT(object->IsMarked()); |
| ASSERT(Heap::Contains(object)); |
| marking_stack.Push(object); |
| if (marking_stack.is_full()) return; |
| } |
| } |
| } |
| |
| |
| bool MarkCompactCollector::IsUnmarkedHeapObject(Object** p) { |
| return (*p)->IsHeapObject() && !HeapObject::cast(*p)->IsMarked(); |
| } |
| |
| |
| void MarkCompactCollector::MarkSymbolTable() { |
| SymbolTable* symbol_table = Heap::raw_unchecked_symbol_table(); |
| // Mark the symbol table itself. |
| SetMark(symbol_table); |
| // Explicitly mark the prefix. |
| MarkingVisitor marker; |
| symbol_table->IteratePrefix(&marker); |
| ProcessMarkingStack(); |
| } |
| |
| |
| void MarkCompactCollector::MarkRoots(RootMarkingVisitor* visitor) { |
| // Mark the heap roots including global variables, stack variables, |
| // etc., and all objects reachable from them. |
| Heap::IterateStrongRoots(visitor, VISIT_ONLY_STRONG); |
| |
| // Handle the symbol table specially. |
| MarkSymbolTable(); |
| |
| // There may be overflowed objects in the heap. Visit them now. |
| while (marking_stack.overflowed()) { |
| RefillMarkingStack(); |
| EmptyMarkingStack(); |
| } |
| } |
| |
| |
| void MarkCompactCollector::MarkObjectGroups() { |
| List<ObjectGroup*>* object_groups = GlobalHandles::ObjectGroups(); |
| |
| for (int i = 0; i < object_groups->length(); i++) { |
| ObjectGroup* entry = object_groups->at(i); |
| if (entry == NULL) continue; |
| |
| List<Object**>& objects = entry->objects_; |
| bool group_marked = false; |
| for (int j = 0; j < objects.length(); j++) { |
| Object* object = *objects[j]; |
| if (object->IsHeapObject() && HeapObject::cast(object)->IsMarked()) { |
| group_marked = true; |
| break; |
| } |
| } |
| |
| if (!group_marked) continue; |
| |
| // An object in the group is marked, so mark as gray all white heap |
| // objects in the group. |
| for (int j = 0; j < objects.length(); ++j) { |
| if ((*objects[j])->IsHeapObject()) { |
| MarkObject(HeapObject::cast(*objects[j])); |
| } |
| } |
| |
| // Once the entire group has been colored gray, set the object group |
| // to NULL so it won't be processed again. |
| delete entry; |
| object_groups->at(i) = NULL; |
| } |
| } |
| |
| |
| void MarkCompactCollector::MarkImplicitRefGroups() { |
| List<ImplicitRefGroup*>* ref_groups = GlobalHandles::ImplicitRefGroups(); |
| |
| for (int i = 0; i < ref_groups->length(); i++) { |
| ImplicitRefGroup* entry = ref_groups->at(i); |
| if (entry == NULL) continue; |
| |
| if (!entry->parent_->IsMarked()) continue; |
| |
| List<Object**>& children = entry->children_; |
| // A parent object is marked, so mark as gray all child white heap |
| // objects. |
| for (int j = 0; j < children.length(); ++j) { |
| if ((*children[j])->IsHeapObject()) { |
| MarkObject(HeapObject::cast(*children[j])); |
| } |
| } |
| |
| // Once the entire group has been colored gray, set the group |
| // to NULL so it won't be processed again. |
| delete entry; |
| ref_groups->at(i) = NULL; |
| } |
| } |
| |
| |
| // Mark all objects reachable from the objects on the marking stack. |
| // Before: the marking stack contains zero or more heap object pointers. |
| // After: the marking stack is empty, and all objects reachable from the |
| // marking stack have been marked, or are overflowed in the heap. |
| void MarkCompactCollector::EmptyMarkingStack() { |
| while (!marking_stack.is_empty()) { |
| HeapObject* object = marking_stack.Pop(); |
| ASSERT(object->IsHeapObject()); |
| ASSERT(Heap::Contains(object)); |
| ASSERT(object->IsMarked()); |
| ASSERT(!object->IsOverflowed()); |
| |
| // Because the object is marked, we have to recover the original map |
| // pointer and use it to mark the object's body. |
| MapWord map_word = object->map_word(); |
| map_word.ClearMark(); |
| Map* map = map_word.ToMap(); |
| MarkObject(map); |
| |
| StaticMarkingVisitor::IterateBody(map, object); |
| } |
| } |
| |
| |
| // Sweep the heap for overflowed objects, clear their overflow bits, and |
| // push them on the marking stack. Stop early if the marking stack fills |
| // before sweeping completes. If sweeping completes, there are no remaining |
| // overflowed objects in the heap so the overflow flag on the markings stack |
| // is cleared. |
| void MarkCompactCollector::RefillMarkingStack() { |
| ASSERT(marking_stack.overflowed()); |
| |
| SemiSpaceIterator new_it(Heap::new_space(), &OverflowObjectSize); |
| ScanOverflowedObjects(&new_it); |
| if (marking_stack.is_full()) return; |
| |
| HeapObjectIterator old_pointer_it(Heap::old_pointer_space(), |
| &OverflowObjectSize); |
| ScanOverflowedObjects(&old_pointer_it); |
| if (marking_stack.is_full()) return; |
| |
| HeapObjectIterator old_data_it(Heap::old_data_space(), &OverflowObjectSize); |
| ScanOverflowedObjects(&old_data_it); |
| if (marking_stack.is_full()) return; |
| |
| HeapObjectIterator code_it(Heap::code_space(), &OverflowObjectSize); |
| ScanOverflowedObjects(&code_it); |
| if (marking_stack.is_full()) return; |
| |
| HeapObjectIterator map_it(Heap::map_space(), &OverflowObjectSize); |
| ScanOverflowedObjects(&map_it); |
| if (marking_stack.is_full()) return; |
| |
| HeapObjectIterator cell_it(Heap::cell_space(), &OverflowObjectSize); |
| ScanOverflowedObjects(&cell_it); |
| if (marking_stack.is_full()) return; |
| |
| LargeObjectIterator lo_it(Heap::lo_space(), &OverflowObjectSize); |
| ScanOverflowedObjects(&lo_it); |
| if (marking_stack.is_full()) return; |
| |
| marking_stack.clear_overflowed(); |
| } |
| |
| |
| // Mark all objects reachable (transitively) from objects on the marking |
| // stack. Before: the marking stack contains zero or more heap object |
| // pointers. After: the marking stack is empty and there are no overflowed |
| // objects in the heap. |
| void MarkCompactCollector::ProcessMarkingStack() { |
| EmptyMarkingStack(); |
| while (marking_stack.overflowed()) { |
| RefillMarkingStack(); |
| EmptyMarkingStack(); |
| } |
| } |
| |
| |
| void MarkCompactCollector::ProcessExternalMarking() { |
| bool work_to_do = true; |
| ASSERT(marking_stack.is_empty()); |
| while (work_to_do) { |
| MarkObjectGroups(); |
| MarkImplicitRefGroups(); |
| work_to_do = !marking_stack.is_empty(); |
| ProcessMarkingStack(); |
| } |
| } |
| |
| |
| void MarkCompactCollector::MarkLiveObjects() { |
| GCTracer::Scope gc_scope(tracer_, GCTracer::Scope::MC_MARK); |
| // The recursive GC marker detects when it is nearing stack overflow, |
| // and switches to a different marking system. JS interrupts interfere |
| // with the C stack limit check. |
| PostponeInterruptsScope postpone; |
| |
| #ifdef DEBUG |
| ASSERT(state_ == PREPARE_GC); |
| state_ = MARK_LIVE_OBJECTS; |
| #endif |
| // The to space contains live objects, the from space is used as a marking |
| // stack. |
| marking_stack.Initialize(Heap::new_space()->FromSpaceLow(), |
| Heap::new_space()->FromSpaceHigh()); |
| |
| ASSERT(!marking_stack.overflowed()); |
| |
| PrepareForCodeFlushing(); |
| |
| RootMarkingVisitor root_visitor; |
| MarkRoots(&root_visitor); |
| |
| // The objects reachable from the roots are marked, yet unreachable |
| // objects are unmarked. Mark objects reachable due to host |
| // application specific logic. |
| ProcessExternalMarking(); |
| |
| // The objects reachable from the roots or object groups are marked, |
| // yet unreachable objects are unmarked. Mark objects reachable |
| // only from weak global handles. |
| // |
| // First we identify nonlive weak handles and mark them as pending |
| // destruction. |
| GlobalHandles::IdentifyWeakHandles(&IsUnmarkedHeapObject); |
| // Then we mark the objects and process the transitive closure. |
| GlobalHandles::IterateWeakRoots(&root_visitor); |
| while (marking_stack.overflowed()) { |
| RefillMarkingStack(); |
| EmptyMarkingStack(); |
| } |
| |
| // Repeat host application specific marking to mark unmarked objects |
| // reachable from the weak roots. |
| ProcessExternalMarking(); |
| |
| // Prune the symbol table removing all symbols only pointed to by the |
| // symbol table. Cannot use symbol_table() here because the symbol |
| // table is marked. |
| SymbolTable* symbol_table = Heap::raw_unchecked_symbol_table(); |
| SymbolTableCleaner v; |
| symbol_table->IterateElements(&v); |
| symbol_table->ElementsRemoved(v.PointersRemoved()); |
| ExternalStringTable::Iterate(&v); |
| ExternalStringTable::CleanUp(); |
| |
| // Process the weak references. |
| MarkCompactWeakObjectRetainer mark_compact_object_retainer; |
| Heap::ProcessWeakReferences(&mark_compact_object_retainer); |
| |
| // Remove object groups after marking phase. |
| GlobalHandles::RemoveObjectGroups(); |
| GlobalHandles::RemoveImplicitRefGroups(); |
| |
| // Flush code from collected candidates. |
| FlushCode::ProcessCandidates(); |
| |
| // Clean up dead objects from the runtime profiler. |
| RuntimeProfiler::RemoveDeadSamples(); |
| } |
| |
| |
| #ifdef DEBUG |
| void MarkCompactCollector::UpdateLiveObjectCount(HeapObject* obj) { |
| live_bytes_ += obj->Size(); |
| if (Heap::new_space()->Contains(obj)) { |
| live_young_objects_size_ += obj->Size(); |
| } else if (Heap::map_space()->Contains(obj)) { |
| ASSERT(obj->IsMap()); |
| live_map_objects_size_ += obj->Size(); |
| } else if (Heap::cell_space()->Contains(obj)) { |
| ASSERT(obj->IsJSGlobalPropertyCell()); |
| live_cell_objects_size_ += obj->Size(); |
| } else if (Heap::old_pointer_space()->Contains(obj)) { |
| live_old_pointer_objects_size_ += obj->Size(); |
| } else if (Heap::old_data_space()->Contains(obj)) { |
| live_old_data_objects_size_ += obj->Size(); |
| } else if (Heap::code_space()->Contains(obj)) { |
| live_code_objects_size_ += obj->Size(); |
| } else if (Heap::lo_space()->Contains(obj)) { |
| live_lo_objects_size_ += obj->Size(); |
| } else { |
| UNREACHABLE(); |
| } |
| } |
| #endif // DEBUG |
| |
| |
| void MarkCompactCollector::SweepLargeObjectSpace() { |
| #ifdef DEBUG |
| ASSERT(state_ == MARK_LIVE_OBJECTS); |
| state_ = |
| compacting_collection_ ? ENCODE_FORWARDING_ADDRESSES : SWEEP_SPACES; |
| #endif |
| // Deallocate unmarked objects and clear marked bits for marked objects. |
| Heap::lo_space()->FreeUnmarkedObjects(); |
| } |
| |
| |
| // Safe to use during marking phase only. |
| bool MarkCompactCollector::SafeIsMap(HeapObject* object) { |
| MapWord metamap = object->map_word(); |
| metamap.ClearMark(); |
| return metamap.ToMap()->instance_type() == MAP_TYPE; |
| } |
| |
| |
| void MarkCompactCollector::ClearNonLiveTransitions() { |
| HeapObjectIterator map_iterator(Heap::map_space(), &SizeOfMarkedObject); |
| // Iterate over the map space, setting map transitions that go from |
| // a marked map to an unmarked map to null transitions. At the same time, |
| // set all the prototype fields of maps back to their original value, |
| // dropping the back pointers temporarily stored in the prototype field. |
| // Setting the prototype field requires following the linked list of |
| // back pointers, reversing them all at once. This allows us to find |
| // those maps with map transitions that need to be nulled, and only |
| // scan the descriptor arrays of those maps, not all maps. |
| // All of these actions are carried out only on maps of JSObjects |
| // and related subtypes. |
| for (HeapObject* obj = map_iterator.next(); |
| obj != NULL; obj = map_iterator.next()) { |
| Map* map = reinterpret_cast<Map*>(obj); |
| if (!map->IsMarked() && map->IsByteArray()) continue; |
| |
| ASSERT(SafeIsMap(map)); |
| // Only JSObject and subtypes have map transitions and back pointers. |
| if (map->instance_type() < FIRST_JS_OBJECT_TYPE) continue; |
| if (map->instance_type() > JS_FUNCTION_TYPE) continue; |
| |
| if (map->IsMarked() && map->attached_to_shared_function_info()) { |
| // This map is used for inobject slack tracking and has been detached |
| // from SharedFunctionInfo during the mark phase. |
| // Since it survived the GC, reattach it now. |
| map->unchecked_constructor()->unchecked_shared()->AttachInitialMap(map); |
| } |
| |
| // Follow the chain of back pointers to find the prototype. |
| Map* current = map; |
| while (SafeIsMap(current)) { |
| current = reinterpret_cast<Map*>(current->prototype()); |
| ASSERT(current->IsHeapObject()); |
| } |
| Object* real_prototype = current; |
| |
| // Follow back pointers, setting them to prototype, |
| // clearing map transitions when necessary. |
| current = map; |
| bool on_dead_path = !current->IsMarked(); |
| Object* next; |
| while (SafeIsMap(current)) { |
| next = current->prototype(); |
| // There should never be a dead map above a live map. |
| ASSERT(on_dead_path || current->IsMarked()); |
| |
| // A live map above a dead map indicates a dead transition. |
| // This test will always be false on the first iteration. |
| if (on_dead_path && current->IsMarked()) { |
| on_dead_path = false; |
| current->ClearNonLiveTransitions(real_prototype); |
| } |
| *HeapObject::RawField(current, Map::kPrototypeOffset) = |
| real_prototype; |
| current = reinterpret_cast<Map*>(next); |
| } |
| } |
| } |
| |
| // ------------------------------------------------------------------------- |
| // Phase 2: Encode forwarding addresses. |
| // When compacting, forwarding addresses for objects in old space and map |
| // space are encoded in their map pointer word (along with an encoding of |
| // their map pointers). |
| // |
| // The excact encoding is described in the comments for class MapWord in |
| // objects.h. |
| // |
| // An address range [start, end) can have both live and non-live objects. |
| // Maximal non-live regions are marked so they can be skipped on subsequent |
| // sweeps of the heap. A distinguished map-pointer encoding is used to mark |
| // free regions of one-word size (in which case the next word is the start |
| // of a live object). A second distinguished map-pointer encoding is used |
| // to mark free regions larger than one word, and the size of the free |
| // region (including the first word) is written to the second word of the |
| // region. |
| // |
| // Any valid map page offset must lie in the object area of the page, so map |
| // page offsets less than Page::kObjectStartOffset are invalid. We use a |
| // pair of distinguished invalid map encodings (for single word and multiple |
| // words) to indicate free regions in the page found during computation of |
| // forwarding addresses and skipped over in subsequent sweeps. |
| |
| |
| // Encode a free region, defined by the given start address and size, in the |
| // first word or two of the region. |
| void EncodeFreeRegion(Address free_start, int free_size) { |
| ASSERT(free_size >= kIntSize); |
| if (free_size == kIntSize) { |
| Memory::uint32_at(free_start) = MarkCompactCollector::kSingleFreeEncoding; |
| } else { |
| ASSERT(free_size >= 2 * kIntSize); |
| Memory::uint32_at(free_start) = MarkCompactCollector::kMultiFreeEncoding; |
| Memory::int_at(free_start + kIntSize) = free_size; |
| } |
| |
| #ifdef DEBUG |
| // Zap the body of the free region. |
| if (FLAG_enable_slow_asserts) { |
| for (int offset = 2 * kIntSize; |
| offset < free_size; |
| offset += kPointerSize) { |
| Memory::Address_at(free_start + offset) = kZapValue; |
| } |
| } |
| #endif |
| } |
| |
| |
| // Try to promote all objects in new space. Heap numbers and sequential |
| // strings are promoted to the code space, large objects to large object space, |
| // and all others to the old space. |
| inline MaybeObject* MCAllocateFromNewSpace(HeapObject* object, |
| int object_size) { |
| MaybeObject* forwarded; |
| if (object_size > Heap::MaxObjectSizeInPagedSpace()) { |
| forwarded = Failure::Exception(); |
| } else { |
| OldSpace* target_space = Heap::TargetSpace(object); |
| ASSERT(target_space == Heap::old_pointer_space() || |
| target_space == Heap::old_data_space()); |
| forwarded = target_space->MCAllocateRaw(object_size); |
| } |
| Object* result; |
| if (!forwarded->ToObject(&result)) { |
| result = Heap::new_space()->MCAllocateRaw(object_size)->ToObjectUnchecked(); |
| } |
| return result; |
| } |
| |
| |
| // Allocation functions for the paged spaces call the space's MCAllocateRaw. |
| MUST_USE_RESULT inline MaybeObject* MCAllocateFromOldPointerSpace( |
| HeapObject* ignore, |
| int object_size) { |
| return Heap::old_pointer_space()->MCAllocateRaw(object_size); |
| } |
| |
| |
| MUST_USE_RESULT inline MaybeObject* MCAllocateFromOldDataSpace( |
| HeapObject* ignore, |
| int object_size) { |
| return Heap::old_data_space()->MCAllocateRaw(object_size); |
| } |
| |
| |
| MUST_USE_RESULT inline MaybeObject* MCAllocateFromCodeSpace( |
| HeapObject* ignore, |
| int object_size) { |
| return Heap::code_space()->MCAllocateRaw(object_size); |
| } |
| |
| |
| MUST_USE_RESULT inline MaybeObject* MCAllocateFromMapSpace( |
| HeapObject* ignore, |
| int object_size) { |
| return Heap::map_space()->MCAllocateRaw(object_size); |
| } |
| |
| |
| MUST_USE_RESULT inline MaybeObject* MCAllocateFromCellSpace(HeapObject* ignore, |
| int object_size) { |
| return Heap::cell_space()->MCAllocateRaw(object_size); |
| } |
| |
| |
| // The forwarding address is encoded at the same offset as the current |
| // to-space object, but in from space. |
| inline void EncodeForwardingAddressInNewSpace(HeapObject* old_object, |
| int object_size, |
| Object* new_object, |
| int* ignored) { |
| int offset = |
| Heap::new_space()->ToSpaceOffsetForAddress(old_object->address()); |
| Memory::Address_at(Heap::new_space()->FromSpaceLow() + offset) = |
| HeapObject::cast(new_object)->address(); |
| } |
| |
| |
| // The forwarding address is encoded in the map pointer of the object as an |
| // offset (in terms of live bytes) from the address of the first live object |
| // in the page. |
| inline void EncodeForwardingAddressInPagedSpace(HeapObject* old_object, |
| int object_size, |
| Object* new_object, |
| int* offset) { |
| // Record the forwarding address of the first live object if necessary. |
| if (*offset == 0) { |
| Page::FromAddress(old_object->address())->mc_first_forwarded = |
| HeapObject::cast(new_object)->address(); |
| } |
| |
| MapWord encoding = |
| MapWord::EncodeAddress(old_object->map()->address(), *offset); |
| old_object->set_map_word(encoding); |
| *offset += object_size; |
| ASSERT(*offset <= Page::kObjectAreaSize); |
| } |
| |
| |
| // Most non-live objects are ignored. |
| inline void IgnoreNonLiveObject(HeapObject* object) {} |
| |
| |
| // Function template that, given a range of addresses (eg, a semispace or a |
| // paged space page), iterates through the objects in the range to clear |
| // mark bits and compute and encode forwarding addresses. As a side effect, |
| // maximal free chunks are marked so that they can be skipped on subsequent |
| // sweeps. |
| // |
| // The template parameters are an allocation function, a forwarding address |
| // encoding function, and a function to process non-live objects. |
| template<MarkCompactCollector::AllocationFunction Alloc, |
| MarkCompactCollector::EncodingFunction Encode, |
| MarkCompactCollector::ProcessNonLiveFunction ProcessNonLive> |
| inline void EncodeForwardingAddressesInRange(Address start, |
| Address end, |
| int* offset) { |
| // The start address of the current free region while sweeping the space. |
| // This address is set when a transition from live to non-live objects is |
| // encountered. A value (an encoding of the 'next free region' pointer) |
| // is written to memory at this address when a transition from non-live to |
| // live objects is encountered. |
| Address free_start = NULL; |
| |
| // A flag giving the state of the previously swept object. Initially true |
| // to ensure that free_start is initialized to a proper address before |
| // trying to write to it. |
| bool is_prev_alive = true; |
| |
| int object_size; // Will be set on each iteration of the loop. |
| for (Address current = start; current < end; current += object_size) { |
| HeapObject* object = HeapObject::FromAddress(current); |
| if (object->IsMarked()) { |
| object->ClearMark(); |
| MarkCompactCollector::tracer()->decrement_marked_count(); |
| object_size = object->Size(); |
| |
| // Allocation cannot fail, because we are compacting the space. |
| Object* forwarded = Alloc(object, object_size)->ToObjectUnchecked(); |
| Encode(object, object_size, forwarded, offset); |
| |
| #ifdef DEBUG |
| if (FLAG_gc_verbose) { |
| PrintF("forward %p -> %p.\n", object->address(), |
| HeapObject::cast(forwarded)->address()); |
| } |
| #endif |
| if (!is_prev_alive) { // Transition from non-live to live. |
| EncodeFreeRegion(free_start, static_cast<int>(current - free_start)); |
| is_prev_alive = true; |
| } |
| } else { // Non-live object. |
| object_size = object->Size(); |
| ProcessNonLive(object); |
| if (is_prev_alive) { // Transition from live to non-live. |
| free_start = current; |
| is_prev_alive = false; |
| } |
| LiveObjectList::ProcessNonLive(object); |
| } |
| } |
| |
| // If we ended on a free region, mark it. |
| if (!is_prev_alive) { |
| EncodeFreeRegion(free_start, static_cast<int>(end - free_start)); |
| } |
| } |
| |
| |
| // Functions to encode the forwarding pointers in each compactable space. |
| void MarkCompactCollector::EncodeForwardingAddressesInNewSpace() { |
| int ignored; |
| EncodeForwardingAddressesInRange<MCAllocateFromNewSpace, |
| EncodeForwardingAddressInNewSpace, |
| IgnoreNonLiveObject>( |
| Heap::new_space()->bottom(), |
| Heap::new_space()->top(), |
| &ignored); |
| } |
| |
| |
| template<MarkCompactCollector::AllocationFunction Alloc, |
| MarkCompactCollector::ProcessNonLiveFunction ProcessNonLive> |
| void MarkCompactCollector::EncodeForwardingAddressesInPagedSpace( |
| PagedSpace* space) { |
| PageIterator it(space, PageIterator::PAGES_IN_USE); |
| while (it.has_next()) { |
| Page* p = it.next(); |
| |
| // The offset of each live object in the page from the first live object |
| // in the page. |
| int offset = 0; |
| EncodeForwardingAddressesInRange<Alloc, |
| EncodeForwardingAddressInPagedSpace, |
| ProcessNonLive>( |
| p->ObjectAreaStart(), |
| p->AllocationTop(), |
| &offset); |
| } |
| } |
| |
| |
| // We scavange new space simultaneously with sweeping. This is done in two |
| // passes. |
| // The first pass migrates all alive objects from one semispace to another or |
| // promotes them to old space. Forwading address is written directly into |
| // first word of object without any encoding. If object is dead we are writing |
| // NULL as a forwarding address. |
| // The second pass updates pointers to new space in all spaces. It is possible |
| // to encounter pointers to dead objects during traversal of dirty regions we |
| // should clear them to avoid encountering them during next dirty regions |
| // iteration. |
| static void MigrateObject(Address dst, |
| Address src, |
| int size, |
| bool to_old_space) { |
| if (to_old_space) { |
| Heap::CopyBlockToOldSpaceAndUpdateRegionMarks(dst, src, size); |
| } else { |
| Heap::CopyBlock(dst, src, size); |
| } |
| |
| Memory::Address_at(src) = dst; |
| } |
| |
| |
| class StaticPointersToNewGenUpdatingVisitor : public |
| StaticNewSpaceVisitor<StaticPointersToNewGenUpdatingVisitor> { |
| public: |
| static inline void VisitPointer(Object** p) { |
| if (!(*p)->IsHeapObject()) return; |
| |
| HeapObject* obj = HeapObject::cast(*p); |
| Address old_addr = obj->address(); |
| |
| if (Heap::new_space()->Contains(obj)) { |
| ASSERT(Heap::InFromSpace(*p)); |
| *p = HeapObject::FromAddress(Memory::Address_at(old_addr)); |
| } |
| } |
| }; |
| |
| |
| // Visitor for updating pointers from live objects in old spaces to new space. |
| // It does not expect to encounter pointers to dead objects. |
| class PointersToNewGenUpdatingVisitor: public ObjectVisitor { |
| public: |
| void VisitPointer(Object** p) { |
| StaticPointersToNewGenUpdatingVisitor::VisitPointer(p); |
| } |
| |
| void VisitPointers(Object** start, Object** end) { |
| for (Object** p = start; p < end; p++) { |
| StaticPointersToNewGenUpdatingVisitor::VisitPointer(p); |
| } |
| } |
| |
| void VisitCodeTarget(RelocInfo* rinfo) { |
| ASSERT(RelocInfo::IsCodeTarget(rinfo->rmode())); |
| Object* target = Code::GetCodeFromTargetAddress(rinfo->target_address()); |
| VisitPointer(&target); |
| rinfo->set_target_address(Code::cast(target)->instruction_start()); |
| } |
| |
| void VisitDebugTarget(RelocInfo* rinfo) { |
| ASSERT((RelocInfo::IsJSReturn(rinfo->rmode()) && |
| rinfo->IsPatchedReturnSequence()) || |
| (RelocInfo::IsDebugBreakSlot(rinfo->rmode()) && |
| rinfo->IsPatchedDebugBreakSlotSequence())); |
| Object* target = Code::GetCodeFromTargetAddress(rinfo->call_address()); |
| VisitPointer(&target); |
| rinfo->set_call_address(Code::cast(target)->instruction_start()); |
| } |
| }; |
| |
| |
| // Visitor for updating pointers from live objects in old spaces to new space. |
| // It can encounter pointers to dead objects in new space when traversing map |
| // space (see comment for MigrateObject). |
| static void UpdatePointerToNewGen(HeapObject** p) { |
| if (!(*p)->IsHeapObject()) return; |
| |
| Address old_addr = (*p)->address(); |
| ASSERT(Heap::InFromSpace(*p)); |
| |
| Address new_addr = Memory::Address_at(old_addr); |
| |
| if (new_addr == NULL) { |
| // We encountered pointer to a dead object. Clear it so we will |
| // not visit it again during next iteration of dirty regions. |
| *p = NULL; |
| } else { |
| *p = HeapObject::FromAddress(new_addr); |
| } |
| } |
| |
| |
| static String* UpdateNewSpaceReferenceInExternalStringTableEntry(Object **p) { |
| Address old_addr = HeapObject::cast(*p)->address(); |
| Address new_addr = Memory::Address_at(old_addr); |
| return String::cast(HeapObject::FromAddress(new_addr)); |
| } |
| |
| |
| static bool TryPromoteObject(HeapObject* object, int object_size) { |
| Object* result; |
| |
| if (object_size > Heap::MaxObjectSizeInPagedSpace()) { |
| MaybeObject* maybe_result = |
| Heap::lo_space()->AllocateRawFixedArray(object_size); |
| if (maybe_result->ToObject(&result)) { |
| HeapObject* target = HeapObject::cast(result); |
| MigrateObject(target->address(), object->address(), object_size, true); |
| MarkCompactCollector::tracer()-> |
| increment_promoted_objects_size(object_size); |
| return true; |
| } |
| } else { |
| OldSpace* target_space = Heap::TargetSpace(object); |
| |
| ASSERT(target_space == Heap::old_pointer_space() || |
| target_space == Heap::old_data_space()); |
| MaybeObject* maybe_result = target_space->AllocateRaw(object_size); |
| if (maybe_result->ToObject(&result)) { |
| HeapObject* target = HeapObject::cast(result); |
| MigrateObject(target->address(), |
| object->address(), |
| object_size, |
| target_space == Heap::old_pointer_space()); |
| MarkCompactCollector::tracer()-> |
| increment_promoted_objects_size(object_size); |
| return true; |
| } |
| } |
| |
| return false; |
| } |
| |
| |
| static void SweepNewSpace(NewSpace* space) { |
| Heap::CheckNewSpaceExpansionCriteria(); |
| |
| Address from_bottom = space->bottom(); |
| Address from_top = space->top(); |
| |
| // Flip the semispaces. After flipping, to space is empty, from space has |
| // live objects. |
| space->Flip(); |
| space->ResetAllocationInfo(); |
| |
| int size = 0; |
| int survivors_size = 0; |
| |
| // First pass: traverse all objects in inactive semispace, remove marks, |
| // migrate live objects and write forwarding addresses. |
| for (Address current = from_bottom; current < from_top; current += size) { |
| HeapObject* object = HeapObject::FromAddress(current); |
| |
| if (object->IsMarked()) { |
| object->ClearMark(); |
| MarkCompactCollector::tracer()->decrement_marked_count(); |
| |
| size = object->Size(); |
| survivors_size += size; |
| |
| // Aggressively promote young survivors to the old space. |
| if (TryPromoteObject(object, size)) { |
| continue; |
| } |
| |
| // Promotion failed. Just migrate object to another semispace. |
| // Allocation cannot fail at this point: semispaces are of equal size. |
| Object* target = space->AllocateRaw(size)->ToObjectUnchecked(); |
| |
| MigrateObject(HeapObject::cast(target)->address(), |
| current, |
| size, |
| false); |
| } else { |
| // Process the dead object before we write a NULL into its header. |
| LiveObjectList::ProcessNonLive(object); |
| |
| size = object->Size(); |
| Memory::Address_at(current) = NULL; |
| } |
| } |
| |
| // Second pass: find pointers to new space and update them. |
| PointersToNewGenUpdatingVisitor updating_visitor; |
| |
| // Update pointers in to space. |
| Address current = space->bottom(); |
| while (current < space->top()) { |
| HeapObject* object = HeapObject::FromAddress(current); |
| current += |
| StaticPointersToNewGenUpdatingVisitor::IterateBody(object->map(), |
| object); |
| } |
| |
| // Update roots. |
| Heap::IterateRoots(&updating_visitor, VISIT_ALL_IN_SCAVENGE); |
| LiveObjectList::IterateElements(&updating_visitor); |
| |
| // Update pointers in old spaces. |
| Heap::IterateDirtyRegions(Heap::old_pointer_space(), |
| &Heap::IteratePointersInDirtyRegion, |
| &UpdatePointerToNewGen, |
| Heap::WATERMARK_SHOULD_BE_VALID); |
| |
| Heap::lo_space()->IterateDirtyRegions(&UpdatePointerToNewGen); |
| |
| // Update pointers from cells. |
| HeapObjectIterator cell_iterator(Heap::cell_space()); |
| for (HeapObject* cell = cell_iterator.next(); |
| cell != NULL; |
| cell = cell_iterator.next()) { |
| if (cell->IsJSGlobalPropertyCell()) { |
| Address value_address = |
| reinterpret_cast<Address>(cell) + |
| (JSGlobalPropertyCell::kValueOffset - kHeapObjectTag); |
| updating_visitor.VisitPointer(reinterpret_cast<Object**>(value_address)); |
| } |
| } |
| |
| // Update pointer from the global contexts list. |
| updating_visitor.VisitPointer(Heap::global_contexts_list_address()); |
| |
| // Update pointers from external string table. |
| Heap::UpdateNewSpaceReferencesInExternalStringTable( |
| &UpdateNewSpaceReferenceInExternalStringTableEntry); |
| |
| // All pointers were updated. Update auxiliary allocation info. |
| Heap::IncrementYoungSurvivorsCounter(survivors_size); |
| space->set_age_mark(space->top()); |
| |
| // Update JSFunction pointers from the runtime profiler. |
| RuntimeProfiler::UpdateSamplesAfterScavenge(); |
| } |
| |
| |
| static void SweepSpace(PagedSpace* space) { |
| PageIterator it(space, PageIterator::PAGES_IN_USE); |
| |
| // During sweeping of paged space we are trying to find longest sequences |
| // of pages without live objects and free them (instead of putting them on |
| // the free list). |
| |
| // Page preceding current. |
| Page* prev = Page::FromAddress(NULL); |
| |
| // First empty page in a sequence. |
| Page* first_empty_page = Page::FromAddress(NULL); |
| |
| // Page preceding first empty page. |
| Page* prec_first_empty_page = Page::FromAddress(NULL); |
| |
| // If last used page of space ends with a sequence of dead objects |
| // we can adjust allocation top instead of puting this free area into |
| // the free list. Thus during sweeping we keep track of such areas |
| // and defer their deallocation until the sweeping of the next page |
| // is done: if one of the next pages contains live objects we have |
| // to put such area into the free list. |
| Address last_free_start = NULL; |
| int last_free_size = 0; |
| |
| while (it.has_next()) { |
| Page* p = it.next(); |
| |
| bool is_previous_alive = true; |
| Address free_start = NULL; |
| HeapObject* object; |
| |
| for (Address current = p->ObjectAreaStart(); |
| current < p->AllocationTop(); |
| current += object->Size()) { |
| object = HeapObject::FromAddress(current); |
| if (object->IsMarked()) { |
| object->ClearMark(); |
| MarkCompactCollector::tracer()->decrement_marked_count(); |
| |
| if (!is_previous_alive) { // Transition from free to live. |
| space->DeallocateBlock(free_start, |
| static_cast<int>(current - free_start), |
| true); |
| is_previous_alive = true; |
| } |
| } else { |
| MarkCompactCollector::ReportDeleteIfNeeded(object); |
| if (is_previous_alive) { // Transition from live to free. |
| free_start = current; |
| is_previous_alive = false; |
| } |
| LiveObjectList::ProcessNonLive(object); |
| } |
| // The object is now unmarked for the call to Size() at the top of the |
| // loop. |
| } |
| |
| bool page_is_empty = (p->ObjectAreaStart() == p->AllocationTop()) |
| || (!is_previous_alive && free_start == p->ObjectAreaStart()); |
| |
| if (page_is_empty) { |
| // This page is empty. Check whether we are in the middle of |
| // sequence of empty pages and start one if not. |
| if (!first_empty_page->is_valid()) { |
| first_empty_page = p; |
| prec_first_empty_page = prev; |
| } |
| |
| if (!is_previous_alive) { |
| // There are dead objects on this page. Update space accounting stats |
| // without putting anything into free list. |
| int size_in_bytes = static_cast<int>(p->AllocationTop() - free_start); |
| if (size_in_bytes > 0) { |
| space->DeallocateBlock(free_start, size_in_bytes, false); |
| } |
| } |
| } else { |
| // This page is not empty. Sequence of empty pages ended on the previous |
| // one. |
| if (first_empty_page->is_valid()) { |
| space->FreePages(prec_first_empty_page, prev); |
| prec_first_empty_page = first_empty_page = Page::FromAddress(NULL); |
| } |
| |
| // If there is a free ending area on one of the previous pages we have |
| // deallocate that area and put it on the free list. |
| if (last_free_size > 0) { |
| Page::FromAddress(last_free_start)-> |
| SetAllocationWatermark(last_free_start); |
| space->DeallocateBlock(last_free_start, last_free_size, true); |
| last_free_start = NULL; |
| last_free_size = 0; |
| } |
| |
| // If the last region of this page was not live we remember it. |
| if (!is_previous_alive) { |
| ASSERT(last_free_size == 0); |
| last_free_size = static_cast<int>(p->AllocationTop() - free_start); |
| last_free_start = free_start; |
| } |
| } |
| |
| prev = p; |
| } |
| |
| // We reached end of space. See if we need to adjust allocation top. |
| Address new_allocation_top = NULL; |
| |
| if (first_empty_page->is_valid()) { |
| // Last used pages in space are empty. We can move allocation top backwards |
| // to the beginning of first empty page. |
| ASSERT(prev == space->AllocationTopPage()); |
| |
| new_allocation_top = first_empty_page->ObjectAreaStart(); |
| } |
| |
| if (last_free_size > 0) { |
| // There was a free ending area on the previous page. |
| // Deallocate it without putting it into freelist and move allocation |
| // top to the beginning of this free area. |
| space->DeallocateBlock(last_free_start, last_free_size, false); |
| new_allocation_top = last_free_start; |
| } |
| |
| if (new_allocation_top != NULL) { |
| #ifdef DEBUG |
| Page* new_allocation_top_page = Page::FromAllocationTop(new_allocation_top); |
| if (!first_empty_page->is_valid()) { |
| ASSERT(new_allocation_top_page == space->AllocationTopPage()); |
| } else if (last_free_size > 0) { |
| ASSERT(new_allocation_top_page == prec_first_empty_page); |
| } else { |
| ASSERT(new_allocation_top_page == first_empty_page); |
| } |
| #endif |
| |
| space->SetTop(new_allocation_top); |
| } |
| } |
| |
| |
| void MarkCompactCollector::EncodeForwardingAddresses() { |
| ASSERT(state_ == ENCODE_FORWARDING_ADDRESSES); |
| // Objects in the active semispace of the young generation may be |
| // relocated to the inactive semispace (if not promoted). Set the |
| // relocation info to the beginning of the inactive semispace. |
| Heap::new_space()->MCResetRelocationInfo(); |
| |
| // Compute the forwarding pointers in each space. |
| EncodeForwardingAddressesInPagedSpace<MCAllocateFromOldPointerSpace, |
| ReportDeleteIfNeeded>( |
| Heap::old_pointer_space()); |
| |
| EncodeForwardingAddressesInPagedSpace<MCAllocateFromOldDataSpace, |
| IgnoreNonLiveObject>( |
| Heap::old_data_space()); |
| |
| EncodeForwardingAddressesInPagedSpace<MCAllocateFromCodeSpace, |
| ReportDeleteIfNeeded>( |
| Heap::code_space()); |
| |
| EncodeForwardingAddressesInPagedSpace<MCAllocateFromCellSpace, |
| IgnoreNonLiveObject>( |
| Heap::cell_space()); |
| |
| |
| // Compute new space next to last after the old and code spaces have been |
| // compacted. Objects in new space can be promoted to old or code space. |
| EncodeForwardingAddressesInNewSpace(); |
| |
| // Compute map space last because computing forwarding addresses |
| // overwrites non-live objects. Objects in the other spaces rely on |
| // non-live map pointers to get the sizes of non-live objects. |
| EncodeForwardingAddressesInPagedSpace<MCAllocateFromMapSpace, |
| IgnoreNonLiveObject>( |
| Heap::map_space()); |
| |
| // Write relocation info to the top page, so we can use it later. This is |
| // done after promoting objects from the new space so we get the correct |
| // allocation top. |
| Heap::old_pointer_space()->MCWriteRelocationInfoToPage(); |
| Heap::old_data_space()->MCWriteRelocationInfoToPage(); |
| Heap::code_space()->MCWriteRelocationInfoToPage(); |
| Heap::map_space()->MCWriteRelocationInfoToPage(); |
| Heap::cell_space()->MCWriteRelocationInfoToPage(); |
| } |
| |
| |
| class MapIterator : public HeapObjectIterator { |
| public: |
| MapIterator() : HeapObjectIterator(Heap::map_space(), &SizeCallback) { } |
| |
| explicit MapIterator(Address start) |
| : HeapObjectIterator(Heap::map_space(), start, &SizeCallback) { } |
| |
| private: |
| static int SizeCallback(HeapObject* unused) { |
| USE(unused); |
| return Map::kSize; |
| } |
| }; |
| |
| |
| class MapCompact { |
| public: |
| explicit MapCompact(int live_maps) |
| : live_maps_(live_maps), |
| to_evacuate_start_(Heap::map_space()->TopAfterCompaction(live_maps)), |
| map_to_evacuate_it_(to_evacuate_start_), |
| first_map_to_evacuate_( |
| reinterpret_cast<Map*>(HeapObject::FromAddress(to_evacuate_start_))) { |
| } |
| |
| void CompactMaps() { |
| // As we know the number of maps to evacuate beforehand, |
| // we stop then there is no more vacant maps. |
| for (Map* next_vacant_map = NextVacantMap(); |
| next_vacant_map; |
| next_vacant_map = NextVacantMap()) { |
| EvacuateMap(next_vacant_map, NextMapToEvacuate()); |
| } |
| |
| #ifdef DEBUG |
| CheckNoMapsToEvacuate(); |
| #endif |
| } |
| |
| void UpdateMapPointersInRoots() { |
| Heap::IterateRoots(&map_updating_visitor_, VISIT_ONLY_STRONG); |
| GlobalHandles::IterateWeakRoots(&map_updating_visitor_); |
| LiveObjectList::IterateElements(&map_updating_visitor_); |
| } |
| |
| void UpdateMapPointersInPagedSpace(PagedSpace* space) { |
| ASSERT(space != Heap::map_space()); |
| |
| PageIterator it(space, PageIterator::PAGES_IN_USE); |
| while (it.has_next()) { |
| Page* p = it.next(); |
| UpdateMapPointersInRange(p->ObjectAreaStart(), p->AllocationTop()); |
| } |
| } |
| |
| void UpdateMapPointersInNewSpace() { |
| NewSpace* space = Heap::new_space(); |
| UpdateMapPointersInRange(space->bottom(), space->top()); |
| } |
| |
| void UpdateMapPointersInLargeObjectSpace() { |
| LargeObjectIterator it(Heap::lo_space()); |
| for (HeapObject* obj = it.next(); obj != NULL; obj = it.next()) |
| UpdateMapPointersInObject(obj); |
| } |
| |
| void Finish() { |
| Heap::map_space()->FinishCompaction(to_evacuate_start_, live_maps_); |
| } |
| |
| private: |
| int live_maps_; |
| Address to_evacuate_start_; |
| MapIterator vacant_map_it_; |
| MapIterator map_to_evacuate_it_; |
| Map* first_map_to_evacuate_; |
| |
| // Helper class for updating map pointers in HeapObjects. |
| class MapUpdatingVisitor: public ObjectVisitor { |
| public: |
| void VisitPointer(Object** p) { |
| UpdateMapPointer(p); |
| } |
| |
| void VisitPointers(Object** start, Object** end) { |
| for (Object** p = start; p < end; p++) UpdateMapPointer(p); |
| } |
| |
| private: |
| void UpdateMapPointer(Object** p) { |
| if (!(*p)->IsHeapObject()) return; |
| HeapObject* old_map = reinterpret_cast<HeapObject*>(*p); |
| |
| // Moved maps are tagged with overflowed map word. They are the only |
| // objects those map word is overflowed as marking is already complete. |
| MapWord map_word = old_map->map_word(); |
| if (!map_word.IsOverflowed()) return; |
| |
| *p = GetForwardedMap(map_word); |
| } |
| }; |
| |
| static MapUpdatingVisitor map_updating_visitor_; |
| |
| static Map* NextMap(MapIterator* it, HeapObject* last, bool live) { |
| while (true) { |
| HeapObject* next = it->next(); |
| ASSERT(next != NULL); |
| if (next == last) |
| return NULL; |
| ASSERT(!next->IsOverflowed()); |
| ASSERT(!next->IsMarked()); |
| ASSERT(next->IsMap() || FreeListNode::IsFreeListNode(next)); |
| if (next->IsMap() == live) |
| return reinterpret_cast<Map*>(next); |
| } |
| } |
| |
| Map* NextVacantMap() { |
| Map* map = NextMap(&vacant_map_it_, first_map_to_evacuate_, false); |
| ASSERT(map == NULL || FreeListNode::IsFreeListNode(map)); |
| return map; |
| } |
| |
| Map* NextMapToEvacuate() { |
| Map* map = NextMap(&map_to_evacuate_it_, NULL, true); |
| ASSERT(map != NULL); |
| ASSERT(map->IsMap()); |
| return map; |
| } |
| |
| static void EvacuateMap(Map* vacant_map, Map* map_to_evacuate) { |
| ASSERT(FreeListNode::IsFreeListNode(vacant_map)); |
| ASSERT(map_to_evacuate->IsMap()); |
| |
| ASSERT(Map::kSize % 4 == 0); |
| |
| Heap::CopyBlockToOldSpaceAndUpdateRegionMarks(vacant_map->address(), |
| map_to_evacuate->address(), |
| Map::kSize); |
| |
| ASSERT(vacant_map->IsMap()); // Due to memcpy above. |
| |
| MapWord forwarding_map_word = MapWord::FromMap(vacant_map); |
| forwarding_map_word.SetOverflow(); |
| map_to_evacuate->set_map_word(forwarding_map_word); |
| |
| ASSERT(map_to_evacuate->map_word().IsOverflowed()); |
| ASSERT(GetForwardedMap(map_to_evacuate->map_word()) == vacant_map); |
| } |
| |
| static Map* GetForwardedMap(MapWord map_word) { |
| ASSERT(map_word.IsOverflowed()); |
| map_word.ClearOverflow(); |
| Map* new_map = map_word.ToMap(); |
| ASSERT_MAP_ALIGNED(new_map->address()); |
| return new_map; |
| } |
| |
| static int UpdateMapPointersInObject(HeapObject* obj) { |
| ASSERT(!obj->IsMarked()); |
| Map* map = obj->map(); |
| ASSERT(Heap::map_space()->Contains(map)); |
| MapWord map_word = map->map_word(); |
| ASSERT(!map_word.IsMarked()); |
| if (map_word.IsOverflowed()) { |
| Map* new_map = GetForwardedMap(map_word); |
| ASSERT(Heap::map_space()->Contains(new_map)); |
| obj->set_map(new_map); |
| |
| #ifdef DEBUG |
| if (FLAG_gc_verbose) { |
| PrintF("update %p : %p -> %p\n", |
| obj->address(), |
| reinterpret_cast<void*>(map), |
| reinterpret_cast<void*>(new_map)); |
| } |
| #endif |
| } |
| |
| int size = obj->SizeFromMap(map); |
| obj->IterateBody(map->instance_type(), size, &map_updating_visitor_); |
| return size; |
| } |
| |
| static void UpdateMapPointersInRange(Address start, Address end) { |
| HeapObject* object; |
| int size; |
| for (Address current = start; current < end; current += size) { |
| object = HeapObject::FromAddress(current); |
| size = UpdateMapPointersInObject(object); |
| ASSERT(size > 0); |
| } |
| } |
| |
| #ifdef DEBUG |
| void CheckNoMapsToEvacuate() { |
| if (!FLAG_enable_slow_asserts) |
| return; |
| |
| for (HeapObject* obj = map_to_evacuate_it_.next(); |
| obj != NULL; obj = map_to_evacuate_it_.next()) |
| ASSERT(FreeListNode::IsFreeListNode(obj)); |
| } |
| #endif |
| }; |
| |
| MapCompact::MapUpdatingVisitor MapCompact::map_updating_visitor_; |
| |
| |
| void MarkCompactCollector::SweepSpaces() { |
| GCTracer::Scope gc_scope(tracer_, GCTracer::Scope::MC_SWEEP); |
| |
| ASSERT(state_ == SWEEP_SPACES); |
| ASSERT(!IsCompacting()); |
| // Noncompacting collections simply sweep the spaces to clear the mark |
| // bits and free the nonlive blocks (for old and map spaces). We sweep |
| // the map space last because freeing non-live maps overwrites them and |
| // the other spaces rely on possibly non-live maps to get the sizes for |
| // non-live objects. |
| SweepSpace(Heap::old_pointer_space()); |
| SweepSpace(Heap::old_data_space()); |
| SweepSpace(Heap::code_space()); |
| SweepSpace(Heap::cell_space()); |
| { GCTracer::Scope gc_scope(tracer_, GCTracer::Scope::MC_SWEEP_NEWSPACE); |
| SweepNewSpace(Heap::new_space()); |
| } |
| SweepSpace(Heap::map_space()); |
| |
| Heap::IterateDirtyRegions(Heap::map_space(), |
| &Heap::IteratePointersInDirtyMapsRegion, |
| &UpdatePointerToNewGen, |
| Heap::WATERMARK_SHOULD_BE_VALID); |
| |
| intptr_t live_maps_size = Heap::map_space()->Size(); |
| int live_maps = static_cast<int>(live_maps_size / Map::kSize); |
| ASSERT(live_map_objects_size_ == live_maps_size); |
| |
| if (Heap::map_space()->NeedsCompaction(live_maps)) { |
| MapCompact map_compact(live_maps); |
| |
| map_compact.CompactMaps(); |
| map_compact.UpdateMapPointersInRoots(); |
| |
| PagedSpaces spaces; |
| for (PagedSpace* space = spaces.next(); |
| space != NULL; space = spaces.next()) { |
| if (space == Heap::map_space()) continue; |
| map_compact.UpdateMapPointersInPagedSpace(space); |
| } |
| map_compact.UpdateMapPointersInNewSpace(); |
| map_compact.UpdateMapPointersInLargeObjectSpace(); |
| |
| map_compact.Finish(); |
| } |
| } |
| |
| |
| // Iterate the live objects in a range of addresses (eg, a page or a |
| // semispace). The live regions of the range have been linked into a list. |
| // The first live region is [first_live_start, first_live_end), and the last |
| // address in the range is top. The callback function is used to get the |
| // size of each live object. |
| int MarkCompactCollector::IterateLiveObjectsInRange( |
| Address start, |
| Address end, |
| HeapObjectCallback size_func) { |
| int live_objects_size = 0; |
| Address current = start; |
| while (current < end) { |
| uint32_t encoded_map = Memory::uint32_at(current); |
| if (encoded_map == kSingleFreeEncoding) { |
| current += kPointerSize; |
| } else if (encoded_map == kMultiFreeEncoding) { |
| current += Memory::int_at(current + kIntSize); |
| } else { |
| int size = size_func(HeapObject::FromAddress(current)); |
| current += size; |
| live_objects_size += size; |
| } |
| } |
| return live_objects_size; |
| } |
| |
| |
| int MarkCompactCollector::IterateLiveObjects(NewSpace* space, |
| HeapObjectCallback size_f) { |
| ASSERT(MARK_LIVE_OBJECTS < state_ && state_ <= RELOCATE_OBJECTS); |
| return IterateLiveObjectsInRange(space->bottom(), space->top(), size_f); |
| } |
| |
| |
| int MarkCompactCollector::IterateLiveObjects(PagedSpace* space, |
| HeapObjectCallback size_f) { |
| ASSERT(MARK_LIVE_OBJECTS < state_ && state_ <= RELOCATE_OBJECTS); |
| int total = 0; |
| PageIterator it(space, PageIterator::PAGES_IN_USE); |
| while (it.has_next()) { |
| Page* p = it.next(); |
| total += IterateLiveObjectsInRange(p->ObjectAreaStart(), |
| p->AllocationTop(), |
| size_f); |
| } |
| return total; |
| } |
| |
| |
| // ------------------------------------------------------------------------- |
| // Phase 3: Update pointers |
| |
| // Helper class for updating pointers in HeapObjects. |
| class UpdatingVisitor: public ObjectVisitor { |
| public: |
| void VisitPointer(Object** p) { |
| UpdatePointer(p); |
| } |
| |
| void VisitPointers(Object** start, Object** end) { |
| // Mark all HeapObject pointers in [start, end) |
| for (Object** p = start; p < end; p++) UpdatePointer(p); |
| } |
| |
| void VisitCodeTarget(RelocInfo* rinfo) { |
| ASSERT(RelocInfo::IsCodeTarget(rinfo->rmode())); |
| Object* target = Code::GetCodeFromTargetAddress(rinfo->target_address()); |
| VisitPointer(&target); |
| rinfo->set_target_address( |
| reinterpret_cast<Code*>(target)->instruction_start()); |
| } |
| |
| void VisitDebugTarget(RelocInfo* rinfo) { |
| ASSERT((RelocInfo::IsJSReturn(rinfo->rmode()) && |
| rinfo->IsPatchedReturnSequence()) || |
| (RelocInfo::IsDebugBreakSlot(rinfo->rmode()) && |
| rinfo->IsPatchedDebugBreakSlotSequence())); |
| Object* target = Code::GetCodeFromTargetAddress(rinfo->call_address()); |
| VisitPointer(&target); |
| rinfo->set_call_address( |
| reinterpret_cast<Code*>(target)->instruction_start()); |
| } |
| |
| private: |
| void UpdatePointer(Object** p) { |
| if (!(*p)->IsHeapObject()) return; |
| |
| HeapObject* obj = HeapObject::cast(*p); |
| Address old_addr = obj->address(); |
| Address new_addr; |
| ASSERT(!Heap::InFromSpace(obj)); |
| |
| if (Heap::new_space()->Contains(obj)) { |
| Address forwarding_pointer_addr = |
| Heap::new_space()->FromSpaceLow() + |
| Heap::new_space()->ToSpaceOffsetForAddress(old_addr); |
| new_addr = Memory::Address_at(forwarding_pointer_addr); |
| |
| #ifdef DEBUG |
| ASSERT(Heap::old_pointer_space()->Contains(new_addr) || |
| Heap::old_data_space()->Contains(new_addr) || |
| Heap::new_space()->FromSpaceContains(new_addr) || |
| Heap::lo_space()->Contains(HeapObject::FromAddress(new_addr))); |
| |
| if (Heap::new_space()->FromSpaceContains(new_addr)) { |
| ASSERT(Heap::new_space()->FromSpaceOffsetForAddress(new_addr) <= |
| Heap::new_space()->ToSpaceOffsetForAddress(old_addr)); |
| } |
| #endif |
| |
| } else if (Heap::lo_space()->Contains(obj)) { |
| // Don't move objects in the large object space. |
| return; |
| |
| } else { |
| #ifdef DEBUG |
| PagedSpaces spaces; |
| PagedSpace* original_space = spaces.next(); |
| while (original_space != NULL) { |
| if (original_space->Contains(obj)) break; |
| original_space = spaces.next(); |
| } |
| ASSERT(original_space != NULL); |
| #endif |
| new_addr = MarkCompactCollector::GetForwardingAddressInOldSpace(obj); |
| ASSERT(original_space->Contains(new_addr)); |
| ASSERT(original_space->MCSpaceOffsetForAddress(new_addr) <= |
| original_space->MCSpaceOffsetForAddress(old_addr)); |
| } |
| |
| *p = HeapObject::FromAddress(new_addr); |
| |
| #ifdef DEBUG |
| if (FLAG_gc_verbose) { |
| PrintF("update %p : %p -> %p\n", |
| reinterpret_cast<Address>(p), old_addr, new_addr); |
| } |
| #endif |
| } |
| }; |
| |
| |
| void MarkCompactCollector::UpdatePointers() { |
| #ifdef DEBUG |
| ASSERT(state_ == ENCODE_FORWARDING_ADDRESSES); |
| state_ = UPDATE_POINTERS; |
| #endif |
| UpdatingVisitor updating_visitor; |
| RuntimeProfiler::UpdateSamplesAfterCompact(&updating_visitor); |
| Heap::IterateRoots(&updating_visitor, VISIT_ONLY_STRONG); |
| GlobalHandles::IterateWeakRoots(&updating_visitor); |
| |
| // Update the pointer to the head of the weak list of global contexts. |
| updating_visitor.VisitPointer(&Heap::global_contexts_list_); |
| |
| LiveObjectList::IterateElements(&updating_visitor); |
| |
| int live_maps_size = IterateLiveObjects(Heap::map_space(), |
| &UpdatePointersInOldObject); |
| int live_pointer_olds_size = IterateLiveObjects(Heap::old_pointer_space(), |
| &UpdatePointersInOldObject); |
| int live_data_olds_size = IterateLiveObjects(Heap::old_data_space(), |
| &UpdatePointersInOldObject); |
| int live_codes_size = IterateLiveObjects(Heap::code_space(), |
| &UpdatePointersInOldObject); |
| int live_cells_size = IterateLiveObjects(Heap::cell_space(), |
| &UpdatePointersInOldObject); |
| int live_news_size = IterateLiveObjects(Heap::new_space(), |
| &UpdatePointersInNewObject); |
| |
| // Large objects do not move, the map word can be updated directly. |
| LargeObjectIterator it(Heap::lo_space()); |
| for (HeapObject* obj = it.next(); obj != NULL; obj = it.next()) { |
| UpdatePointersInNewObject(obj); |
| } |
| |
| USE(live_maps_size); |
| USE(live_pointer_olds_size); |
| USE(live_data_olds_size); |
| USE(live_codes_size); |
| USE(live_cells_size); |
| USE(live_news_size); |
| ASSERT(live_maps_size == live_map_objects_size_); |
| ASSERT(live_data_olds_size == live_old_data_objects_size_); |
| ASSERT(live_pointer_olds_size == live_old_pointer_objects_size_); |
| ASSERT(live_codes_size == live_code_objects_size_); |
| ASSERT(live_cells_size == live_cell_objects_size_); |
| ASSERT(live_news_size == live_young_objects_size_); |
| } |
| |
| |
| int MarkCompactCollector::UpdatePointersInNewObject(HeapObject* obj) { |
| // Keep old map pointers |
| Map* old_map = obj->map(); |
| ASSERT(old_map->IsHeapObject()); |
| |
| Address forwarded = GetForwardingAddressInOldSpace(old_map); |
| |
| ASSERT(Heap::map_space()->Contains(old_map)); |
| ASSERT(Heap::map_space()->Contains(forwarded)); |
| #ifdef DEBUG |
| if (FLAG_gc_verbose) { |
| PrintF("update %p : %p -> %p\n", obj->address(), old_map->address(), |
| forwarded); |
| } |
| #endif |
| // Update the map pointer. |
| obj->set_map(reinterpret_cast<Map*>(HeapObject::FromAddress(forwarded))); |
| |
| // We have to compute the object size relying on the old map because |
| // map objects are not relocated yet. |
| int obj_size = obj->SizeFromMap(old_map); |
| |
| // Update pointers in the object body. |
| UpdatingVisitor updating_visitor; |
| obj->IterateBody(old_map->instance_type(), obj_size, &updating_visitor); |
| return obj_size; |
| } |
| |
| |
| int MarkCompactCollector::UpdatePointersInOldObject(HeapObject* obj) { |
| // Decode the map pointer. |
| MapWord encoding = obj->map_word(); |
| Address map_addr = encoding.DecodeMapAddress(Heap::map_space()); |
| ASSERT(Heap::map_space()->Contains(HeapObject::FromAddress(map_addr))); |
| |
| // At this point, the first word of map_addr is also encoded, cannot |
| // cast it to Map* using Map::cast. |
| Map* map = reinterpret_cast<Map*>(HeapObject::FromAddress(map_addr)); |
| int obj_size = obj->SizeFromMap(map); |
| InstanceType type = map->instance_type(); |
| |
| // Update map pointer. |
| Address new_map_addr = GetForwardingAddressInOldSpace(map); |
| int offset = encoding.DecodeOffset(); |
| obj->set_map_word(MapWord::EncodeAddress(new_map_addr, offset)); |
| |
| #ifdef DEBUG |
| if (FLAG_gc_verbose) { |
| PrintF("update %p : %p -> %p\n", obj->address(), |
| map_addr, new_map_addr); |
| } |
| #endif |
| |
| // Update pointers in the object body. |
| UpdatingVisitor updating_visitor; |
| obj->IterateBody(type, obj_size, &updating_visitor); |
| return obj_size; |
| } |
| |
| |
| Address MarkCompactCollector::GetForwardingAddressInOldSpace(HeapObject* obj) { |
| // Object should either in old or map space. |
| MapWord encoding = obj->map_word(); |
| |
| // Offset to the first live object's forwarding address. |
| int offset = encoding.DecodeOffset(); |
| Address obj_addr = obj->address(); |
| |
| // Find the first live object's forwarding address. |
| Page* p = Page::FromAddress(obj_addr); |
| Address first_forwarded = p->mc_first_forwarded; |
| |
| // Page start address of forwarded address. |
| Page* forwarded_page = Page::FromAddress(first_forwarded); |
| int forwarded_offset = forwarded_page->Offset(first_forwarded); |
| |
| // Find end of allocation in the page of first_forwarded. |
| int mc_top_offset = forwarded_page->AllocationWatermarkOffset(); |
| |
| // Check if current object's forward pointer is in the same page |
| // as the first live object's forwarding pointer |
| if (forwarded_offset + offset < mc_top_offset) { |
| // In the same page. |
| return first_forwarded + offset; |
| } |
| |
| // Must be in the next page, NOTE: this may cross chunks. |
| Page* next_page = forwarded_page->next_page(); |
| ASSERT(next_page->is_valid()); |
| |
| offset -= (mc_top_offset - forwarded_offset); |
| offset += Page::kObjectStartOffset; |
| |
| ASSERT_PAGE_OFFSET(offset); |
| ASSERT(next_page->OffsetToAddress(offset) < next_page->AllocationTop()); |
| |
| return next_page->OffsetToAddress(offset); |
| } |
| |
| |
| // ------------------------------------------------------------------------- |
| // Phase 4: Relocate objects |
| |
| void MarkCompactCollector::RelocateObjects() { |
| #ifdef DEBUG |
| ASSERT(state_ == UPDATE_POINTERS); |
| state_ = RELOCATE_OBJECTS; |
| #endif |
| // Relocates objects, always relocate map objects first. Relocating |
| // objects in other space relies on map objects to get object size. |
| int live_maps_size = IterateLiveObjects(Heap::map_space(), |
| &RelocateMapObject); |
| int live_pointer_olds_size = IterateLiveObjects(Heap::old_pointer_space(), |
| &RelocateOldPointerObject); |
| int live_data_olds_size = IterateLiveObjects(Heap::old_data_space(), |
| &RelocateOldDataObject); |
| int live_codes_size = IterateLiveObjects(Heap::code_space(), |
| &RelocateCodeObject); |
| int live_cells_size = IterateLiveObjects(Heap::cell_space(), |
| &RelocateCellObject); |
| int live_news_size = IterateLiveObjects(Heap::new_space(), |
| &RelocateNewObject); |
| |
| USE(live_maps_size); |
| USE(live_pointer_olds_size); |
| USE(live_data_olds_size); |
| USE(live_codes_size); |
| USE(live_cells_size); |
| USE(live_news_size); |
| ASSERT(live_maps_size == live_map_objects_size_); |
| ASSERT(live_data_olds_size == live_old_data_objects_size_); |
| ASSERT(live_pointer_olds_size == live_old_pointer_objects_size_); |
| ASSERT(live_codes_size == live_code_objects_size_); |
| ASSERT(live_cells_size == live_cell_objects_size_); |
| ASSERT(live_news_size == live_young_objects_size_); |
| |
| // Flip from and to spaces |
| Heap::new_space()->Flip(); |
| |
| Heap::new_space()->MCCommitRelocationInfo(); |
| |
| // Set age_mark to bottom in to space |
| Address mark = Heap::new_space()->bottom(); |
| Heap::new_space()->set_age_mark(mark); |
| |
| PagedSpaces spaces; |
| for (PagedSpace* space = spaces.next(); space != NULL; space = spaces.next()) |
| space->MCCommitRelocationInfo(); |
| |
| Heap::CheckNewSpaceExpansionCriteria(); |
| Heap::IncrementYoungSurvivorsCounter(live_news_size); |
| } |
| |
| |
| int MarkCompactCollector::RelocateMapObject(HeapObject* obj) { |
| // Recover map pointer. |
| MapWord encoding = obj->map_word(); |
| Address map_addr = encoding.DecodeMapAddress(Heap::map_space()); |
| ASSERT(Heap::map_space()->Contains(HeapObject::FromAddress(map_addr))); |
| |
| // Get forwarding address before resetting map pointer |
| Address new_addr = GetForwardingAddressInOldSpace(obj); |
| |
| // Reset map pointer. The meta map object may not be copied yet so |
| // Map::cast does not yet work. |
| obj->set_map(reinterpret_cast<Map*>(HeapObject::FromAddress(map_addr))); |
| |
| Address old_addr = obj->address(); |
| |
| if (new_addr != old_addr) { |
| // Move contents. |
| Heap::MoveBlockToOldSpaceAndUpdateRegionMarks(new_addr, |
| old_addr, |
| Map::kSize); |
| } |
| |
| #ifdef DEBUG |
| if (FLAG_gc_verbose) { |
| PrintF("relocate %p -> %p\n", old_addr, new_addr); |
| } |
| #endif |
| |
| return Map::kSize; |
| } |
| |
| |
| static inline int RestoreMap(HeapObject* obj, |
| PagedSpace* space, |
| Address new_addr, |
| Address map_addr) { |
| // This must be a non-map object, and the function relies on the |
| // assumption that the Map space is compacted before the other paged |
| // spaces (see RelocateObjects). |
| |
| // Reset map pointer. |
| obj->set_map(Map::cast(HeapObject::FromAddress(map_addr))); |
| |
| int obj_size = obj->Size(); |
| ASSERT_OBJECT_SIZE(obj_size); |
| |
| ASSERT(space->MCSpaceOffsetForAddress(new_addr) <= |
| space->MCSpaceOffsetForAddress(obj->address())); |
| |
| #ifdef DEBUG |
| if (FLAG_gc_verbose) { |
| PrintF("relocate %p -> %p\n", obj->address(), new_addr); |
| } |
| #endif |
| |
| return obj_size; |
| } |
| |
| |
| int MarkCompactCollector::RelocateOldNonCodeObject(HeapObject* obj, |
| PagedSpace* space) { |
| // Recover map pointer. |
| MapWord encoding = obj->map_word(); |
| Address map_addr = encoding.DecodeMapAddress(Heap::map_space()); |
| ASSERT(Heap::map_space()->Contains(map_addr)); |
| |
| // Get forwarding address before resetting map pointer. |
| Address new_addr = GetForwardingAddressInOldSpace(obj); |
| |
| // Reset the map pointer. |
| int obj_size = RestoreMap(obj, space, new_addr, map_addr); |
| |
| Address old_addr = obj->address(); |
| |
| if (new_addr != old_addr) { |
| // Move contents. |
| if (space == Heap::old_data_space()) { |
| Heap::MoveBlock(new_addr, old_addr, obj_size); |
| } else { |
| Heap::MoveBlockToOldSpaceAndUpdateRegionMarks(new_addr, |
| old_addr, |
| obj_size); |
| } |
| } |
| |
| ASSERT(!HeapObject::FromAddress(new_addr)->IsCode()); |
| |
| HeapObject* copied_to = HeapObject::FromAddress(new_addr); |
| if (copied_to->IsSharedFunctionInfo()) { |
| PROFILE(SharedFunctionInfoMoveEvent(old_addr, new_addr)); |
| } |
| HEAP_PROFILE(ObjectMoveEvent(old_addr, new_addr)); |
| |
| return obj_size; |
| } |
| |
| |
| int MarkCompactCollector::RelocateOldPointerObject(HeapObject* obj) { |
| return RelocateOldNonCodeObject(obj, Heap::old_pointer_space()); |
| } |
| |
| |
| int MarkCompactCollector::RelocateOldDataObject(HeapObject* obj) { |
| return RelocateOldNonCodeObject(obj, Heap::old_data_space()); |
| } |
| |
| |
| int MarkCompactCollector::RelocateCellObject(HeapObject* obj) { |
| return RelocateOldNonCodeObject(obj, Heap::cell_space()); |
| } |
| |
| |
| int MarkCompactCollector::RelocateCodeObject(HeapObject* obj) { |
| // Recover map pointer. |
| MapWord encoding = obj->map_word(); |
| Address map_addr = encoding.DecodeMapAddress(Heap::map_space()); |
| ASSERT(Heap::map_space()->Contains(HeapObject::FromAddress(map_addr))); |
| |
| // Get forwarding address before resetting map pointer |
| Address new_addr = GetForwardingAddressInOldSpace(obj); |
| |
| // Reset the map pointer. |
| int obj_size = RestoreMap(obj, Heap::code_space(), new_addr, map_addr); |
| |
| Address old_addr = obj->address(); |
| |
| if (new_addr != old_addr) { |
| // Move contents. |
| Heap::MoveBlock(new_addr, old_addr, obj_size); |
| } |
| |
| HeapObject* copied_to = HeapObject::FromAddress(new_addr); |
| if (copied_to->IsCode()) { |
| // May also update inline cache target. |
| Code::cast(copied_to)->Relocate(new_addr - old_addr); |
| // Notify the logger that compiled code has moved. |
| PROFILE(CodeMoveEvent(old_addr, new_addr)); |
| } |
| HEAP_PROFILE(ObjectMoveEvent(old_addr, new_addr)); |
| |
| return obj_size; |
| } |
| |
| |
| int MarkCompactCollector::RelocateNewObject(HeapObject* obj) { |
| int obj_size = obj->Size(); |
| |
| // Get forwarding address |
| Address old_addr = obj->address(); |
| int offset = Heap::new_space()->ToSpaceOffsetForAddress(old_addr); |
| |
| Address new_addr = |
| Memory::Address_at(Heap::new_space()->FromSpaceLow() + offset); |
| |
| #ifdef DEBUG |
| if (Heap::new_space()->FromSpaceContains(new_addr)) { |
| ASSERT(Heap::new_space()->FromSpaceOffsetForAddress(new_addr) <= |
| Heap::new_space()->ToSpaceOffsetForAddress(old_addr)); |
| } else { |
| ASSERT(Heap::TargetSpace(obj) == Heap::old_pointer_space() || |
| Heap::TargetSpace(obj) == Heap::old_data_space()); |
| } |
| #endif |
| |
| // New and old addresses cannot overlap. |
| if (Heap::InNewSpace(HeapObject::FromAddress(new_addr))) { |
| Heap::CopyBlock(new_addr, old_addr, obj_size); |
| } else { |
| Heap::CopyBlockToOldSpaceAndUpdateRegionMarks(new_addr, |
| old_addr, |
| obj_size); |
| } |
| |
| #ifdef DEBUG |
| if (FLAG_gc_verbose) { |
| PrintF("relocate %p -> %p\n", old_addr, new_addr); |
| } |
| #endif |
| |
| HeapObject* copied_to = HeapObject::FromAddress(new_addr); |
| if (copied_to->IsSharedFunctionInfo()) { |
| PROFILE(SharedFunctionInfoMoveEvent(old_addr, new_addr)); |
| } |
| HEAP_PROFILE(ObjectMoveEvent(old_addr, new_addr)); |
| |
| return obj_size; |
| } |
| |
| |
| void MarkCompactCollector::ReportDeleteIfNeeded(HeapObject* obj) { |
| #ifdef ENABLE_GDB_JIT_INTERFACE |
| if (obj->IsCode()) { |
| GDBJITInterface::RemoveCode(reinterpret_cast<Code*>(obj)); |
| } |
| #endif |
| #ifdef ENABLE_LOGGING_AND_PROFILING |
| if (obj->IsCode()) { |
| PROFILE(CodeDeleteEvent(obj->address())); |
| } |
| #endif |
| } |
| |
| |
| int MarkCompactCollector::SizeOfMarkedObject(HeapObject* obj) { |
| MapWord map_word = obj->map_word(); |
| map_word.ClearMark(); |
| return obj->SizeFromMap(map_word.ToMap()); |
| } |
| |
| |
| void MarkCompactCollector::Initialize() { |
| StaticPointersToNewGenUpdatingVisitor::Initialize(); |
| StaticMarkingVisitor::Initialize(); |
| } |
| |
| |
| } } // namespace v8::internal |