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MylesBorinsMylesBorins
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deps: cherry-pick a715957 from V8 upstream
Original commit message: Iterate handles with special left-trim visitor BUG=chromium:620553 LOG=N R=hpayer@chromium.org Review-Url: https://codereview.chromium.org/2102243002 Cr-Commit-Position: refs/heads/master@{#37366}
1 parent 74f4235 commit e822550

5 files changed

Lines changed: 45 additions & 35 deletions

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‎deps/v8/src/heap/heap-inl.h‎

Lines changed: 0 additions & 25 deletions
Original file line numberDiff line numberDiff line change
@@ -449,31 +449,6 @@ void Heap::CopyBlock(Address dst, Address src, int byte_size) {
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static_cast<size_t>(byte_size / kPointerSize));
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}
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452-
bool Heap::PurgeLeftTrimmedObject(Object** object) {
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HeapObject* current = reinterpret_cast<HeapObject*>(*object);
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const MapWord map_word = current->map_word();
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if (current->IsFiller() && !map_word.IsForwardingAddress()) {
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#ifdef DEBUG
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// We need to find a FixedArrayBase map after walking the fillers.
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while (current->IsFiller()) {
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Address next = reinterpret_cast<Address>(current);
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if (current->map() == one_pointer_filler_map()) {
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next += kPointerSize;
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} else if (current->map() == two_pointer_filler_map()) {
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next += 2 * kPointerSize;
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} else {
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next += current->Size();
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}
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current = reinterpret_cast<HeapObject*>(next);
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}
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DCHECK(current->IsFixedArrayBase());
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#endif // DEBUG
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*object = nullptr;
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return true;
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}
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return false;
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}
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template <Heap::FindMementoMode mode>
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AllocationMemento* Heap::FindAllocationMemento(HeapObject* object) {
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// Check if there is potentially a memento behind the object. If

‎deps/v8/src/heap/heap.cc‎

Lines changed: 45 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -4800,6 +4800,49 @@ void Heap::IterateSmiRoots(ObjectVisitor* v) {
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v->Synchronize(VisitorSynchronization::kSmiRootList);
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}
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// We cannot avoid stale handles to left-trimmed objects, but can only make
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// sure all handles still needed are updated. Filter out a stale pointer
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// and clear the slot to allow post processing of handles (needed because
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// the sweeper might actually free the underlying page).
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class FixStaleLeftTrimmedHandlesVisitor : public ObjectVisitor {
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public:
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explicit FixStaleLeftTrimmedHandlesVisitor(Heap* heap) : heap_(heap) {
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USE(heap_);
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}
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void VisitPointer(Object** p) override { FixHandle(p); }
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void VisitPointers(Object** start, Object** end) override {
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for (Object** p = start; p < end; p++) FixHandle(p);
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}
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private:
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inline void FixHandle(Object** p) {
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HeapObject* current = reinterpret_cast<HeapObject*>(*p);
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if (!current->IsHeapObject()) return;
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const MapWord map_word = current->map_word();
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if (!map_word.IsForwardingAddress() && current->IsFiller()) {
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#ifdef DEBUG
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// We need to find a FixedArrayBase map after walking the fillers.
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while (current->IsFiller()) {
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Address next = reinterpret_cast<Address>(current);
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if (current->map() == heap_->one_pointer_filler_map()) {
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next += kPointerSize;
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} else if (current->map() == heap_->two_pointer_filler_map()) {
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next += 2 * kPointerSize;
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} else {
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next += current->Size();
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}
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current = reinterpret_cast<HeapObject*>(next);
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}
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DCHECK(current->IsFixedArrayBase());
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#endif // DEBUG
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*p = nullptr;
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}
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}
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Heap* heap_;
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};
48034846

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void Heap::IterateStrongRoots(ObjectVisitor* v, VisitMode mode) {
48054848
v->VisitPointers(&roots_[0], &roots_[kStrongRootListLength]);
@@ -4820,6 +4863,8 @@ void Heap::IterateStrongRoots(ObjectVisitor* v, VisitMode mode) {
48204863
v->Synchronize(VisitorSynchronization::kCompilationCache);
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48224865
// Iterate over local handles in handle scopes.
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FixStaleLeftTrimmedHandlesVisitor left_trim_visitor(this);
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isolate_->handle_scope_implementer()->Iterate(&left_trim_visitor);
48234868
isolate_->handle_scope_implementer()->Iterate(v);
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isolate_->IterateDeferredHandles(v);
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v->Synchronize(VisitorSynchronization::kHandleScope);

‎deps/v8/src/heap/heap.h‎

Lines changed: 0 additions & 6 deletions
Original file line numberDiff line numberDiff line change
@@ -602,12 +602,6 @@ class Heap {
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// stored on the map to facilitate fast dispatch for {StaticVisitorBase}.
603603
static int GetStaticVisitorIdForMap(Map* map);
604604

605-
// We cannot avoid stale handles to left-trimmed objects, but can only make
606-
// sure all handles still needed are updated. Filter out a stale pointer
607-
// and clear the slot to allow post processing of handles (needed because
608-
// the sweeper might actually free the underlying page).
609-
inline bool PurgeLeftTrimmedObject(Object** object);
610-
611605
// Notifies the heap that is ok to start marking or other activities that
612606
// should not happen during deserialization.
613607
void NotifyDeserializationComplete();

‎deps/v8/src/heap/mark-compact.cc‎

Lines changed: 0 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -1376,8 +1376,6 @@ class RootMarkingVisitor : public ObjectVisitor {
13761376

13771377
HeapObject* object = HeapObject::cast(*p);
13781378

1379-
if (collector_->heap()->PurgeLeftTrimmedObject(p)) return;
1380-
13811379
MarkBit mark_bit = Marking::MarkBitFrom(object);
13821380
if (Marking::IsBlackOrGrey(mark_bit)) return;
13831381

‎deps/v8/src/heap/scavenger.cc‎

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Original file line numberDiff line numberDiff line change
@@ -463,8 +463,6 @@ void ScavengeVisitor::ScavengePointer(Object** p) {
463463
Object* object = *p;
464464
if (!heap_->InNewSpace(object)) return;
465465

466-
if (heap_->PurgeLeftTrimmedObject(p)) return;
467-
468466
Scavenger::ScavengeObject(reinterpret_cast<HeapObject**>(p),
469467
reinterpret_cast<HeapObject*>(object));
470468
}

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