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
10 namespace v8 {
11 namespace internal {
12
ScavengeObject(HeapObject ** p,HeapObject * object)13 void 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
CheckAndScavengeObject(Heap * heap,Address slot_address)40 SlotCallbackResult 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 }
59 // Slots can point to "to" space if the slot has been recorded multiple
60 // times in the remembered set. We remove the redundant slot now.
61 return REMOVE_SLOT;
62 }
63
64 // static
VisitPointer(Heap * heap,HeapObject * obj,Object ** p)65 void StaticScavengeVisitor::VisitPointer(Heap* heap, HeapObject* obj,
66 Object** p) {
67 Object* object = *p;
68 if (!heap->InNewSpace(object)) return;
69 Scavenger::ScavengeObject(reinterpret_cast<HeapObject**>(p),
70 reinterpret_cast<HeapObject*>(object));
71 }
72
73 } // namespace internal
74 } // namespace v8
75
76 #endif // V8_HEAP_SCAVENGER_INL_H_
77