1 files changed, 129 insertions, 8 deletions

diff --git a/js/src/gc/Marking.cpp b/js/src/gc/Marking.cpp
index b92cd5f3ac..0201e20aa7 100644
--- a/js/src/gc/Marking.cpp
+++ b/js/src/gc/Marking.cpp
@@ -1307,9 +1307,20 @@ bool GCMarker::doMarking(SliceBudget& budget, ShouldReportMarkTime reportTime) {
   return true;
 }
 
+class MOZ_RAII gc::AutoUpdateMarkStackRanges {
+  GCMarker& marker_;
+
+ public:
+  explicit AutoUpdateMarkStackRanges(GCMarker& marker) : marker_(marker) {
+    marker_.updateRangesAtStartOfSlice();
+  }
+  ~AutoUpdateMarkStackRanges() { marker_.updateRangesAtEndOfSlice(); }
+};
+
 template <uint32_t opts, MarkColor color>
 bool GCMarker::markOneColor(SliceBudget& budget) {
   AutoSetMarkColor setColor(*this, color);
+  AutoUpdateMarkStackRanges updateRanges(*this);
 
   while (processMarkStackTop<opts>(budget)) {
     if (stack.isEmpty()) {
@@ -1321,6 +1332,8 @@ bool GCMarker::markOneColor(SliceBudget& budget) {
 }
 
 bool GCMarker::markCurrentColorInParallel(SliceBudget& budget) {
+  AutoUpdateMarkStackRanges updateRanges(*this);
+
   ParallelMarker::AtomicCount& waitingTaskCount =
       parallelMarker_->waitingTaskCountRef();
 
@@ -1340,6 +1353,26 @@ bool GCMarker::markCurrentColorInParallel(SliceBudget& budget) {
   return false;
 }
 
+#ifdef DEBUG
+bool GCMarker::markOneObjectForTest(JSObject* obj) {
+  MOZ_ASSERT(obj->zone()->isGCMarking());
+  MOZ_ASSERT(!obj->isMarked(markColor()));
+
+  size_t oldPosition = stack.position();
+  markAndTraverse<NormalMarkingOptions>(obj);
+  if (stack.position() == oldPosition) {
+    return false;
+  }
+
+  AutoUpdateMarkStackRanges updateRanges(*this);
+
+  SliceBudget unlimited = SliceBudget::unlimited();
+  processMarkStackTop<NormalMarkingOptions>(unlimited);
+
+  return true;
+}
+#endif
+
 static inline void CheckForCompartmentMismatch(JSObject* obj, JSObject* obj2) {
 #ifdef DEBUG
   if (MOZ_UNLIKELY(obj->compartment() != obj2->compartment())) {
@@ -1366,6 +1399,47 @@ static inline size_t NumUsedDynamicSlots(NativeObject* obj) {
   return nslots - nfixed;
 }
 
+void GCMarker::updateRangesAtStartOfSlice() {
+  for (MarkStackIter iter(stack); !iter.done(); iter.next()) {
+    if (iter.isSlotsOrElementsRange()) {
+      MarkStack::SlotsOrElementsRange& range = iter.slotsOrElementsRange();
+      JSObject* obj = range.ptr().asRangeObject();
+      if (!obj->is<NativeObject>()) {
+        range.setEmpty();
+      } else if (range.kind() == SlotsOrElementsKind::Elements) {
+        NativeObject* obj = &range.ptr().asRangeObject()->as<NativeObject>();
+        size_t index = range.start();
+        size_t numShifted = obj->getElementsHeader()->numShiftedElements();
+        index -= std::min(numShifted, index);
+        range.setStart(index);
+      }
+    }
+  }
+
+#ifdef DEBUG
+  MOZ_ASSERT(!stack.elementsRangesAreValid);
+  stack.elementsRangesAreValid = true;
+#endif
+}
+
+void GCMarker::updateRangesAtEndOfSlice() {
+  for (MarkStackIter iter(stack); !iter.done(); iter.next()) {
+    if (iter.isSlotsOrElementsRange()) {
+      MarkStack::SlotsOrElementsRange& range = iter.slotsOrElementsRange();
+      if (range.kind() == SlotsOrElementsKind::Elements) {
+        NativeObject* obj = &range.ptr().asRangeObject()->as<NativeObject>();
+        size_t numShifted = obj->getElementsHeader()->numShiftedElements();
+        range.setStart(range.start() + numShifted);
+      }
+    }
+  }
+
+#ifdef DEBUG
+  MOZ_ASSERT(stack.elementsRangesAreValid);
+  stack.elementsRangesAreValid = false;
+#endif
+}
+
 template <uint32_t opts>
 inline bool GCMarker::processMarkStackTop(SliceBudget& budget) {
   /*
@@ -1379,6 +1453,7 @@ inline bool GCMarker::processMarkStackTop(SliceBudget& budget) {
    */
 
   MOZ_ASSERT(!stack.isEmpty());
+  MOZ_ASSERT(stack.elementsRangesAreValid);
   MOZ_ASSERT_IF(markColor() == MarkColor::Gray, !hasBlackEntries());
 
   JSObject* obj;             // The object being scanned.
@@ -1409,12 +1484,7 @@ inline bool GCMarker::processMarkStackTop(SliceBudget& budget) {
 
       case SlotsOrElementsKind::Elements: {
         base = nobj->getDenseElements();
-
-        // Account for shifted elements.
-        size_t numShifted = nobj->getElementsHeader()->numShiftedElements();
-        size_t initlen = nobj->getDenseInitializedLength();
-        index = std::max(index, numShifted) - numShifted;
-        end = initlen;
+        end = nobj->getDenseInitializedLength();
         break;
       }
 
@@ -1590,17 +1660,17 @@ struct MapTypeToMarkStackTag<BaseScript*> {
   static const auto value = MarkStack::ScriptTag;
 };
 
-#ifdef DEBUG
 static inline bool TagIsRangeTag(MarkStack::Tag tag) {
   return tag == MarkStack::SlotsOrElementsRangeTag;
 }
-#endif
 
 inline MarkStack::TaggedPtr::TaggedPtr(Tag tag, Cell* ptr)
     : bits(tag | uintptr_t(ptr)) {
   assertValid();
 }
 
+inline uintptr_t MarkStack::TaggedPtr::asBits() const { return bits; }
+
 inline uintptr_t MarkStack::TaggedPtr::tagUnchecked() const {
   return bits & TagMask;
 }
@@ -1661,6 +1731,17 @@ inline size_t MarkStack::SlotsOrElementsRange::start() const {
   return startAndKind_ >> StartShift;
 }
 
+inline void MarkStack::SlotsOrElementsRange::setStart(size_t newStart) {
+  startAndKind_ = (newStart << StartShift) | uintptr_t(kind());
+  MOZ_ASSERT(start() == newStart);
+}
+
+inline void MarkStack::SlotsOrElementsRange::setEmpty() {
+  TaggedPtr entry = TaggedPtr(ObjectTag, ptr().asRangeObject());
+  ptr_ = entry;
+  startAndKind_ = entry.asBits();
+}
+
 inline MarkStack::TaggedPtr MarkStack::SlotsOrElementsRange::ptr() const {
   return ptr_;
 }
@@ -1931,6 +2012,45 @@ size_t MarkStack::sizeOfExcludingThis(
   return stack().sizeOfExcludingThis(mallocSizeOf);
 }
 
+MarkStackIter::MarkStackIter(MarkStack& stack)
+    : stack_(stack), pos_(stack.position()) {}
+
+inline size_t MarkStackIter::position() const { return pos_; }
+
+inline bool MarkStackIter::done() const { return position() == 0; }
+
+inline void MarkStackIter::next() {
+  if (isSlotsOrElementsRange()) {
+    MOZ_ASSERT(position() >= ValueRangeWords);
+    pos_ -= ValueRangeWords;
+    return;
+  }
+
+  MOZ_ASSERT(!done());
+  pos_--;
+}
+
+inline bool MarkStackIter::isSlotsOrElementsRange() const {
+  return TagIsRangeTag(peekTag());
+}
+
+inline MarkStack::Tag MarkStackIter::peekTag() const { return peekPtr().tag(); }
+
+inline MarkStack::TaggedPtr MarkStackIter::peekPtr() const {
+  MOZ_ASSERT(!done());
+  return stack_.stack()[pos_ - 1];
+}
+
+inline MarkStack::SlotsOrElementsRange& MarkStackIter::slotsOrElementsRange() {
+  MOZ_ASSERT(TagIsRangeTag(peekTag()));
+  MOZ_ASSERT(position() >= ValueRangeWords);
+
+  MarkStack::TaggedPtr* ptr = &stack_.stack()[pos_ - ValueRangeWords];
+  auto& range = *reinterpret_cast<MarkStack::SlotsOrElementsRange*>(ptr);
+  range.assertValid();
+  return range;
+}
+
 /*** GCMarker ***************************************************************/
 
 /*
@@ -2244,6 +2364,7 @@ void GCRuntime::processDelayedMarkingList(MarkColor color) {
   // were added.
 
   AutoSetMarkColor setColor(marker(), color);
+  AutoUpdateMarkStackRanges updateRanges(marker());
 
   do {
     delayedMarkingWorkAdded = false;