Revert of Replace slots buffer with remembered set.

src/heap/slots-buffer.cc

Index: src/heap/slots-buffer.cc
diff --git a/src/heap/slots-buffer.cc b/src/heap/slots-buffer.cc
new file mode 100644
index 0000000000000000000000000000000000000000..5a3db281fda576180de0b76d8468e3f21d5fe345
--- /dev/null
+++ b/src/heap/slots-buffer.cc
@@ -0,0 +1,164 @@
+// Copyright 2015 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "src/heap/slots-buffer.h"
+
+#include "src/assembler.h"
+#include "src/heap/heap.h"
+#include "src/objects-inl.h"
+
+namespace v8 {
+namespace internal {
+
+bool SlotsBuffer::IsTypedSlot(ObjectSlot slot) {
+  return reinterpret_cast<uintptr_t>(slot) < NUMBER_OF_SLOT_TYPES;
+}
+
+
+bool SlotsBuffer::AddTo(SlotsBufferAllocator* allocator,
+                        SlotsBuffer** buffer_address, SlotType type,
+                        Address addr, AdditionMode mode) {
+  SlotsBuffer* buffer = *buffer_address;
+  if (buffer == NULL || !buffer->HasSpaceForTypedSlot()) {
+    if (mode == FAIL_ON_OVERFLOW && ChainLengthThresholdReached(buffer)) {
+      allocator->DeallocateChain(buffer_address);
+      return false;
+    }
+    buffer = allocator->AllocateBuffer(buffer);
+    *buffer_address = buffer;
+  }
+  DCHECK(buffer->HasSpaceForTypedSlot());
+  buffer->Add(reinterpret_cast<ObjectSlot>(type));
+  buffer->Add(reinterpret_cast<ObjectSlot>(addr));
+  return true;
+}
+
+
+void SlotsBuffer::RemoveInvalidSlots(Heap* heap, SlotsBuffer* buffer) {
+  // Remove entries by replacing them with an old-space slot containing a smi
+  // that is located in an unmovable page.
+  const ObjectSlot kRemovedEntry = HeapObject::RawField(
+      heap->empty_fixed_array(), FixedArrayBase::kLengthOffset);
+  DCHECK(Page::FromAddress(reinterpret_cast<Address>(kRemovedEntry))
+             ->NeverEvacuate());
+
+  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;
+        // Slots are invalid when they currently:
+        // - do not point to a heap object (SMI)
+        // - point to a heap object in new space
+        // - are not within a live heap object on a valid pointer slot
+        // - point to a heap object not on an evacuation candidate
+        // TODO(mlippautz): Move InNewSpace check above IsSlotInLiveObject once
+        //   we filter out unboxed double slots eagerly.
+        if (!object->IsHeapObject() ||
+            !heap->mark_compact_collector()->IsSlotInLiveObject(
+                reinterpret_cast<Address>(slot)) ||
+            heap->InNewSpace(object) ||
+            !Page::FromAddress(reinterpret_cast<Address>(object))
+                 ->IsEvacuationCandidate()) {
+          // TODO(hpayer): Instead of replacing slots with kRemovedEntry we
+          // could shrink the slots buffer in-place.
+          slots[slot_idx] = kRemovedEntry;
+        }
+      } else {
+        ++slot_idx;
+        DCHECK(slot_idx < slots_count);
+      }
+    }
+    buffer = buffer->next();
+  }
+}
+
+
+void SlotsBuffer::RemoveObjectSlots(Heap* heap, SlotsBuffer* buffer,
+                                    Address start_slot, Address end_slot) {
+  // Remove entries by replacing them with an old-space slot containing a smi
+  // that is located in an unmovable page.
+  const ObjectSlot kRemovedEntry = HeapObject::RawField(
+      heap->empty_fixed_array(), FixedArrayBase::kLengthOffset);
+  DCHECK(Page::FromAddress(reinterpret_cast<Address>(kRemovedEntry))
+             ->NeverEvacuate());
+
+  while (buffer != NULL) {
+    SlotsBuffer::ObjectSlot* slots = buffer->slots_;
+    intptr_t slots_count = buffer->idx_;
+    bool is_typed_slot = false;
+
+    for (int slot_idx = 0; slot_idx < slots_count; ++slot_idx) {
+      ObjectSlot slot = slots[slot_idx];
+      if (!IsTypedSlot(slot)) {
+        Address slot_address = reinterpret_cast<Address>(slot);
+        if (slot_address >= start_slot && slot_address < end_slot) {
+          // TODO(hpayer): Instead of replacing slots with kRemovedEntry we
+          // could shrink the slots buffer in-place.
+          slots[slot_idx] = kRemovedEntry;
+          if (is_typed_slot) {
+            slots[slot_idx - 1] = kRemovedEntry;
+          }
+        }
+        is_typed_slot = false;
+      } else {
+        is_typed_slot = true;
+        DCHECK(slot_idx < slots_count);
+      }
+    }
+    buffer = buffer->next();
+  }
+}
+
+
+void SlotsBuffer::VerifySlots(Heap* heap, SlotsBuffer* buffer) {
+  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()) {
+          HeapObject* heap_object = HeapObject::cast(object);
+          CHECK(!heap->InNewSpace(object));
+          heap->mark_compact_collector()->VerifyIsSlotInLiveObject(
+              reinterpret_cast<Address>(slot), heap_object);
+        }
+      } else {
+        ++slot_idx;
+        DCHECK(slot_idx < slots_count);
+      }
+    }
+    buffer = buffer->next();
+  }
+}
+
+
+SlotsBuffer* SlotsBufferAllocator::AllocateBuffer(SlotsBuffer* next_buffer) {
+  return new SlotsBuffer(next_buffer);
+}
+
+
+void SlotsBufferAllocator::DeallocateBuffer(SlotsBuffer* buffer) {
+  delete buffer;
+}
+
+
+void SlotsBufferAllocator::DeallocateChain(SlotsBuffer** buffer_address) {
+  SlotsBuffer* buffer = *buffer_address;
+  while (buffer != NULL) {
+    SlotsBuffer* next_buffer = buffer->next();
+    DeallocateBuffer(buffer);
+    buffer = next_buffer;
+  }
+  *buffer_address = NULL;
+}
+
+}  // namespace internal
+}  // namespace v8