Revert of Reland "Filter invalid slots out from the SlotsBuffer after marking."

src/heap/mark-compact.cc

Index: src/heap/mark-compact.cc
diff --git a/src/heap/mark-compact.cc b/src/heap/mark-compact.cc
index b4fafec10939aea23ddd4bc2aada41fee52eced9..f75f323c45a2bbf22794118b0838d5aa3b0e4234 100644
--- a/src/heap/mark-compact.cc
+++ b/src/heap/mark-compact.cc
@@ -287,60 +287,6 @@
 }
 
 
-void MarkCompactCollector::ClearInvalidSlotsBufferEntries(PagedSpace* space) {
-  PageIterator it(space);
-  while (it.has_next()) {
-    Page* p = it.next();
-    SlotsBuffer::RemoveInvalidSlots(heap_, p->slots_buffer());
-  }
-}
-
-
-void MarkCompactCollector::ClearInvalidStoreAndSlotsBufferEntries() {
-  heap_->store_buffer()->ClearInvalidStoreBufferEntries();
-
-  ClearInvalidSlotsBufferEntries(heap_->old_pointer_space());
-  ClearInvalidSlotsBufferEntries(heap_->old_data_space());
-  ClearInvalidSlotsBufferEntries(heap_->code_space());
-  ClearInvalidSlotsBufferEntries(heap_->cell_space());
-  ClearInvalidSlotsBufferEntries(heap_->map_space());
-
-  LargeObjectIterator it(heap_->lo_space());
-  for (HeapObject* object = it.Next(); object != NULL; object = it.Next()) {
-    MemoryChunk* chunk = MemoryChunk::FromAddress(object->address());
-    SlotsBuffer::RemoveInvalidSlots(heap_, chunk->slots_buffer());
-  }
-}
-
-
-#ifdef VERIFY_HEAP
-static void VerifyValidSlotsBufferEntries(Heap* heap, PagedSpace* space) {
-  PageIterator it(space);
-  while (it.has_next()) {
-    Page* p = it.next();
-    SlotsBuffer::VerifySlots(heap, p->slots_buffer());
-  }
-}
-
-
-static void VerifyValidStoreAndSlotsBufferEntries(Heap* heap) {
-  heap->store_buffer()->VerifyValidStoreBufferEntries();
-
-  VerifyValidSlotsBufferEntries(heap, heap->old_pointer_space());
-  VerifyValidSlotsBufferEntries(heap, heap->old_data_space());
-  VerifyValidSlotsBufferEntries(heap, heap->code_space());
-  VerifyValidSlotsBufferEntries(heap, heap->cell_space());
-  VerifyValidSlotsBufferEntries(heap, heap->map_space());
-
-  LargeObjectIterator it(heap->lo_space());
-  for (HeapObject* object = it.Next(); object != NULL; object = it.Next()) {
-    MemoryChunk* chunk = MemoryChunk::FromAddress(object->address());
-    SlotsBuffer::VerifySlots(heap, chunk->slots_buffer());
-  }
-}
-#endif
-
-
 void MarkCompactCollector::CollectGarbage() {
   // Make sure that Prepare() has been called. The individual steps below will
   // update the state as they proceed.
@@ -366,11 +312,11 @@
   }
 #endif
 
-  ClearInvalidStoreAndSlotsBufferEntries();
+  heap_->store_buffer()->ClearInvalidStoreBufferEntries();
 
 #ifdef VERIFY_HEAP
   if (FLAG_verify_heap) {
-    VerifyValidStoreAndSlotsBufferEntries(heap_);
+    heap_->store_buffer()->VerifyValidStoreBufferEntries();
   }
 #endif
 
@@ -777,7 +723,6 @@
 
   int count = 0;
   int fragmentation = 0;
-  int page_number = 0;
   Candidate* least = NULL;
 
   PageIterator it(space);
@@ -792,16 +737,9 @@
     CHECK(p->slots_buffer() == NULL);
 
     if (FLAG_stress_compaction) {
-      if (FLAG_manual_evacuation_candidates_selection) {
-        if (p->IsFlagSet(MemoryChunk::FORCE_EVACUATION_CANDIDATE_FOR_TESTING)) {
-          p->ClearFlag(MemoryChunk::FORCE_EVACUATION_CANDIDATE_FOR_TESTING);
-          fragmentation = 1;
-        }
-      } else {
-        unsigned int counter = space->heap()->ms_count();
-        if ((counter & 1) == (page_number & 1)) fragmentation = 1;
-        page_number++;
-      }
+      unsigned int counter = space->heap()->ms_count();
+      uintptr_t page_number = reinterpret_cast<uintptr_t>(p) >> kPageSizeBits;
+      if ((counter & 1) == (page_number & 1)) fragmentation = 1;
     } else if (mode == REDUCE_MEMORY_FOOTPRINT && !FLAG_always_compact) {
       // Don't try to release too many pages.
       if (estimated_release >= over_reserved) {
@@ -3097,14 +3035,10 @@
 }
 
 
-bool MarkCompactCollector::IsSlotInBlackObject(Page* p, Address slot,
-                                               HeapObject** out_object) {
+bool MarkCompactCollector::IsSlotInBlackObject(Page* p, Address slot) {
   // This function does not support large objects right now.
   Space* owner = p->owner();
-  if (owner == heap_->lo_space() || owner == NULL) {
-    *out_object = NULL;
-    return true;
-  }
+  if (owner == heap_->lo_space() || owner == NULL) return true;
 
   uint32_t mark_bit_index = p->AddressToMarkbitIndex(slot);
   unsigned int start_index = mark_bit_index >> Bitmap::kBitsPerCellLog2;
@@ -3158,7 +3092,6 @@
       (object->address() + object->Size()) > slot) {
     // If the slot is within the last found object in the cell, the slot is
     // in a live object.
-    *out_object = object;
     return true;
   }
   return false;
@@ -3200,38 +3133,28 @@
 }
 
 
-bool MarkCompactCollector::IsSlotInLiveObject(Address slot) {
-  HeapObject* object = NULL;
+bool MarkCompactCollector::IsSlotInLiveObject(HeapObject** address,
+                                              HeapObject* object) {
+  // If the target object is not black, the source slot must be part
+  // of a non-black (dead) object.
+  if (!Marking::IsBlack(Marking::MarkBitFrom(object))) {
+    return false;
+  }
+
   // The target object is black but we don't know if the source slot is black.
   // The source object could have died and the slot could be part of a free
   // space. Find out based on mark bits if the slot is part of a live object.
-  if (!IsSlotInBlackObject(Page::FromAddress(slot), slot, &object)) {
+  if (!IsSlotInBlackObject(
+          Page::FromAddress(reinterpret_cast<Address>(address)),
+          reinterpret_cast<Address>(address))) {
     return false;
   }
 
-#if V8_DOUBLE_FIELDS_UNBOXING
-  // |object| is NULL only when the slot belongs to large object space.
-  DCHECK(object != NULL ||
-         Page::FromAnyPointerAddress(heap_, slot)->owner() ==
-             heap_->lo_space());
-  // We don't need to check large objects' layout descriptor since it can't
-  // contain in-object fields anyway.
-  if (object != NULL) {
-    // Filter out slots that happens to point to unboxed double fields.
-    LayoutDescriptorHelper helper(object->map());
-    bool has_only_tagged_fields = helper.all_fields_tagged();
-    if (!has_only_tagged_fields &&
-        !helper.IsTagged(static_cast<int>(slot - object->address()))) {
-      return false;
-    }
-  }
-#endif
-
   return true;
 }
 
 
-void MarkCompactCollector::VerifyIsSlotInLiveObject(Address slot,
+void MarkCompactCollector::VerifyIsSlotInLiveObject(HeapObject** address,
                                                     HeapObject* object) {
   // The target object has to be black.
   CHECK(Marking::IsBlack(Marking::MarkBitFrom(object)));
@@ -3239,7 +3162,9 @@
   // The target object is black but we don't know if the source slot is black.
   // The source object could have died and the slot could be part of a free
   // space. Use the mark bit iterator to find out about liveness of the slot.
-  CHECK(IsSlotInBlackObjectSlow(Page::FromAddress(slot), slot));
+  CHECK(IsSlotInBlackObjectSlow(
+      Page::FromAddress(reinterpret_cast<Address>(address)),
+      reinterpret_cast<Address>(address)));
 }
 
 
@@ -4558,66 +4483,6 @@
 }
 
 
-static Object* g_smi_slot = NULL;
-
-
-void SlotsBuffer::RemoveInvalidSlots(Heap* heap, SlotsBuffer* buffer) {
-  DCHECK_EQ(Smi::FromInt(0), g_smi_slot);
-
-  // Remove entries by replacing them with a dummy slot containing a smi.
-  const ObjectSlot kRemovedEntry = &g_smi_slot;
-
-  while (buffer != NULL) {
-    SlotsBuffer::ObjectSlot* slots = buffer->slots_;
-    intptr_t slots_count = buffer->idx_;
-
-    for (int slot_idx = 0; slot_idx < slots_count; ++slot_idx) {
-      ObjectSlot slot = slots[slot_idx];
-      if (!IsTypedSlot(slot)) {
-        Object* object = *slot;
-        if (object->IsHeapObject()) {
-          if (heap->InNewSpace(object) ||
-              !heap->mark_compact_collector()->IsSlotInLiveObject(
-                  reinterpret_cast<Address>(slot))) {
-            slots[slot_idx] = kRemovedEntry;
-          }
-        }
-      } else {
-        ++slot_idx;
-        DCHECK(slot_idx < slots_count);
-      }
-    }
-    buffer = buffer->next();
-  }
-}
-
-
-void SlotsBuffer::VerifySlots(Heap* heap, SlotsBuffer* buffer) {
-  DCHECK_EQ(Smi::FromInt(0), g_smi_slot);
-
-  while (buffer != NULL) {
-    SlotsBuffer::ObjectSlot* slots = buffer->slots_;
-    intptr_t slots_count = buffer->idx_;
-
-    for (int slot_idx = 0; slot_idx < slots_count; ++slot_idx) {
-      ObjectSlot slot = slots[slot_idx];
-      if (!IsTypedSlot(slot)) {
-        Object* object = *slot;
-        if (object->IsHeapObject()) {
-          CHECK(!heap->InNewSpace(object));
-          CHECK(heap->mark_compact_collector()->IsSlotInLiveObject(
-              reinterpret_cast<Address>(slot)));
-        }
-      } else {
-        ++slot_idx;
-        DCHECK(slot_idx < slots_count);
-      }
-    }
-    buffer = buffer->next();
-  }
-}
-
-
 static inline SlotsBuffer::SlotType SlotTypeForRMode(RelocInfo::Mode rmode) {
   if (RelocInfo::IsCodeTarget(rmode)) {
     return SlotsBuffer::CODE_TARGET_SLOT;