1// Copyright 2015 the V8 project authors. All rights reserved.
2// Use of this source code is governed by a BSD-style license that can be
3// found in the LICENSE file.
4
5#ifndef V8_HEAP_SCAVENGER_INL_H_
6#define V8_HEAP_SCAVENGER_INL_H_
7
8#include "src/heap/scavenger.h"
9
10namespace v8 {
11namespace internal {
12
13void Scavenger::ScavengeObject(HeapObject** p, HeapObject* object) {
14  DCHECK(object->GetIsolate()->heap()->InFromSpace(object));
15
16  // We use the first word (where the map pointer usually is) of a heap
17  // object to record the forwarding pointer.  A forwarding pointer can
18  // point to an old space, the code space, or the to space of the new
19  // generation.
20  MapWord first_word = object->map_word();
21
22  // If the first word is a forwarding address, the object has already been
23  // copied.
24  if (first_word.IsForwardingAddress()) {
25    HeapObject* dest = first_word.ToForwardingAddress();
26    DCHECK(object->GetIsolate()->heap()->InFromSpace(*p));
27    *p = dest;
28    return;
29  }
30
31  object->GetHeap()->UpdateAllocationSite<Heap::kGlobal>(
32      object, object->GetHeap()->global_pretenuring_feedback_);
33
34  // AllocationMementos are unrooted and shouldn't survive a scavenge
35  DCHECK(object->map() != object->GetHeap()->allocation_memento_map());
36  // Call the slow part of scavenge object.
37  return ScavengeObjectSlow(p, object);
38}
39
40SlotCallbackResult Scavenger::CheckAndScavengeObject(Heap* heap,
41                                                     Address slot_address) {
42  Object** slot = reinterpret_cast<Object**>(slot_address);
43  Object* object = *slot;
44  if (heap->InFromSpace(object)) {
45    HeapObject* heap_object = reinterpret_cast<HeapObject*>(object);
46    DCHECK(heap_object->IsHeapObject());
47
48    ScavengeObject(reinterpret_cast<HeapObject**>(slot), heap_object);
49
50    object = *slot;
51    // If the object was in from space before and is after executing the
52    // callback in to space, the object is still live.
53    // Unfortunately, we do not know about the slot. It could be in a
54    // just freed free space object.
55    if (heap->InToSpace(object)) {
56      return KEEP_SLOT;
57    }
58  } else {
59    DCHECK(!heap->InNewSpace(object));
60  }
61  return REMOVE_SLOT;
62}
63
64// static
65template <PromotionMode promotion_mode>
66void StaticScavengeVisitor<promotion_mode>::VisitPointer(Heap* heap,
67                                                         HeapObject* obj,
68                                                         Object** p) {
69  Object* object = *p;
70  if (!heap->InNewSpace(object)) return;
71  Scavenger::ScavengeObject(reinterpret_cast<HeapObject**>(p),
72                            reinterpret_cast<HeapObject*>(object));
73}
74
75}  // namespace internal
76}  // namespace v8
77
78#endif  // V8_HEAP_SCAVENGER_INL_H_
79