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 #include "src/heap/slots-buffer.h"
6
7 #include "src/assembler.h"
8 #include "src/heap/heap.h"
9 #include "src/objects-inl.h"
10
11 namespace v8 {
12 namespace internal {
13
IsTypedSlot(ObjectSlot slot)14 bool SlotsBuffer::IsTypedSlot(ObjectSlot slot) {
15 return reinterpret_cast<uintptr_t>(slot) < NUMBER_OF_SLOT_TYPES;
16 }
17
18
AddTo(SlotsBufferAllocator * allocator,SlotsBuffer ** buffer_address,SlotType type,Address addr,AdditionMode mode)19 bool SlotsBuffer::AddTo(SlotsBufferAllocator* allocator,
20 SlotsBuffer** buffer_address, SlotType type,
21 Address addr, AdditionMode mode) {
22 SlotsBuffer* buffer = *buffer_address;
23 if (buffer == NULL || !buffer->HasSpaceForTypedSlot()) {
24 if (mode == FAIL_ON_OVERFLOW && ChainLengthThresholdReached(buffer)) {
25 allocator->DeallocateChain(buffer_address);
26 return false;
27 }
28 buffer = allocator->AllocateBuffer(buffer);
29 *buffer_address = buffer;
30 }
31 DCHECK(buffer->HasSpaceForTypedSlot());
32 buffer->Add(reinterpret_cast<ObjectSlot>(type));
33 buffer->Add(reinterpret_cast<ObjectSlot>(addr));
34 return true;
35 }
36
37
RemoveInvalidSlots(Heap * heap,SlotsBuffer * buffer)38 void SlotsBuffer::RemoveInvalidSlots(Heap* heap, SlotsBuffer* buffer) {
39 // Remove entries by replacing them with an old-space slot containing a smi
40 // that is located in an unmovable page.
41 const ObjectSlot kRemovedEntry = HeapObject::RawField(
42 heap->empty_fixed_array(), FixedArrayBase::kLengthOffset);
43 DCHECK(Page::FromAddress(reinterpret_cast<Address>(kRemovedEntry))
44 ->NeverEvacuate());
45
46 while (buffer != NULL) {
47 SlotsBuffer::ObjectSlot* slots = buffer->slots_;
48 intptr_t slots_count = buffer->idx_;
49
50 for (int slot_idx = 0; slot_idx < slots_count; ++slot_idx) {
51 ObjectSlot slot = slots[slot_idx];
52 if (!IsTypedSlot(slot)) {
53 Object* object = *slot;
54 // Slots are invalid when they currently:
55 // - do not point to a heap object (SMI)
56 // - point to a heap object in new space
57 // - are not within a live heap object on a valid pointer slot
58 // - point to a heap object not on an evacuation candidate
59 if (!object->IsHeapObject() || heap->InNewSpace(object) ||
60 !heap->mark_compact_collector()->IsSlotInLiveObject(
61 reinterpret_cast<Address>(slot)) ||
62 !Page::FromAddress(reinterpret_cast<Address>(object))
63 ->IsEvacuationCandidate()) {
64 // TODO(hpayer): Instead of replacing slots with kRemovedEntry we
65 // could shrink the slots buffer in-place.
66 slots[slot_idx] = kRemovedEntry;
67 }
68 } else {
69 ++slot_idx;
70 DCHECK(slot_idx < slots_count);
71 }
72 }
73 buffer = buffer->next();
74 }
75 }
76
77
RemoveObjectSlots(Heap * heap,SlotsBuffer * buffer,Address start_slot,Address end_slot)78 void SlotsBuffer::RemoveObjectSlots(Heap* heap, SlotsBuffer* buffer,
79 Address start_slot, Address end_slot) {
80 // Remove entries by replacing them with an old-space slot containing a smi
81 // that is located in an unmovable page.
82 const ObjectSlot kRemovedEntry = HeapObject::RawField(
83 heap->empty_fixed_array(), FixedArrayBase::kLengthOffset);
84 DCHECK(Page::FromAddress(reinterpret_cast<Address>(kRemovedEntry))
85 ->NeverEvacuate());
86
87 while (buffer != NULL) {
88 SlotsBuffer::ObjectSlot* slots = buffer->slots_;
89 intptr_t slots_count = buffer->idx_;
90 bool is_typed_slot = false;
91
92 for (int slot_idx = 0; slot_idx < slots_count; ++slot_idx) {
93 ObjectSlot slot = slots[slot_idx];
94 if (!IsTypedSlot(slot)) {
95 Address slot_address = reinterpret_cast<Address>(slot);
96 if (slot_address >= start_slot && slot_address < end_slot) {
97 // TODO(hpayer): Instead of replacing slots with kRemovedEntry we
98 // could shrink the slots buffer in-place.
99 slots[slot_idx] = kRemovedEntry;
100 if (is_typed_slot) {
101 slots[slot_idx - 1] = kRemovedEntry;
102 }
103 }
104 is_typed_slot = false;
105 } else {
106 is_typed_slot = true;
107 DCHECK(slot_idx < slots_count);
108 }
109 }
110 buffer = buffer->next();
111 }
112 }
113
114
VerifySlots(Heap * heap,SlotsBuffer * buffer)115 void SlotsBuffer::VerifySlots(Heap* heap, SlotsBuffer* buffer) {
116 while (buffer != NULL) {
117 SlotsBuffer::ObjectSlot* slots = buffer->slots_;
118 intptr_t slots_count = buffer->idx_;
119
120 for (int slot_idx = 0; slot_idx < slots_count; ++slot_idx) {
121 ObjectSlot slot = slots[slot_idx];
122 if (!IsTypedSlot(slot)) {
123 Object* object = *slot;
124 if (object->IsHeapObject()) {
125 HeapObject* heap_object = HeapObject::cast(object);
126 CHECK(!heap->InNewSpace(object));
127 heap->mark_compact_collector()->VerifyIsSlotInLiveObject(
128 reinterpret_cast<Address>(slot), heap_object);
129 }
130 } else {
131 ++slot_idx;
132 DCHECK(slot_idx < slots_count);
133 }
134 }
135 buffer = buffer->next();
136 }
137 }
138
139
AllocateBuffer(SlotsBuffer * next_buffer)140 SlotsBuffer* SlotsBufferAllocator::AllocateBuffer(SlotsBuffer* next_buffer) {
141 return new SlotsBuffer(next_buffer);
142 }
143
144
DeallocateBuffer(SlotsBuffer * buffer)145 void SlotsBufferAllocator::DeallocateBuffer(SlotsBuffer* buffer) {
146 delete buffer;
147 }
148
149
DeallocateChain(SlotsBuffer ** buffer_address)150 void SlotsBufferAllocator::DeallocateChain(SlotsBuffer** buffer_address) {
151 SlotsBuffer* buffer = *buffer_address;
152 while (buffer != NULL) {
153 SlotsBuffer* next_buffer = buffer->next();
154 DeallocateBuffer(buffer);
155 buffer = next_buffer;
156 }
157 *buffer_address = NULL;
158 }
159
160 } // namespace internal
161 } // namespace v8
162