Line data Source code
1 : // Copyright 2014 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/layout-descriptor.h"
6 :
7 : #include <sstream>
8 :
9 : #include "src/base/bits.h"
10 : #include "src/handles-inl.h"
11 : #include "src/objects-inl.h"
12 :
13 : using v8::base::bits::CountTrailingZeros32;
14 :
15 : namespace v8 {
16 : namespace internal {
17 :
18 6795761 : Handle<LayoutDescriptor> LayoutDescriptor::New(
19 : Handle<Map> map, Handle<DescriptorArray> descriptors, int num_descriptors) {
20 : Isolate* isolate = descriptors->GetIsolate();
21 : if (!FLAG_unbox_double_fields) return handle(FastPointerLayout(), isolate);
22 :
23 : int layout_descriptor_length =
24 : CalculateCapacity(*map, *descriptors, num_descriptors);
25 :
26 6795764 : if (layout_descriptor_length == 0) {
27 : // No double fields were found, use fast pointer layout.
28 : return handle(FastPointerLayout(), isolate);
29 : }
30 :
31 : // Initially, layout descriptor corresponds to an object with all fields
32 : // tagged.
33 : Handle<LayoutDescriptor> layout_descriptor_handle =
34 : LayoutDescriptor::New(isolate, layout_descriptor_length);
35 :
36 : LayoutDescriptor* layout_descriptor = Initialize(
37 : *layout_descriptor_handle, *map, *descriptors, num_descriptors);
38 :
39 : return handle(layout_descriptor, isolate);
40 : }
41 :
42 :
43 9537776 : Handle<LayoutDescriptor> LayoutDescriptor::ShareAppend(
44 : Handle<Map> map, PropertyDetails details) {
45 : DCHECK(map->owns_descriptors());
46 : Isolate* isolate = map->GetIsolate();
47 : Handle<LayoutDescriptor> layout_descriptor(map->GetLayoutDescriptor(),
48 : isolate);
49 :
50 9537778 : if (!InobjectUnboxedField(map->GetInObjectProperties(), details)) {
51 : DCHECK(details.location() != kField ||
52 : layout_descriptor->IsTagged(details.field_index()));
53 9524486 : return layout_descriptor;
54 : }
55 : int field_index = details.field_index();
56 : layout_descriptor = LayoutDescriptor::EnsureCapacity(
57 13292 : isolate, layout_descriptor, field_index + details.field_width_in_words());
58 :
59 : DisallowHeapAllocation no_allocation;
60 : LayoutDescriptor* layout_desc = *layout_descriptor;
61 : layout_desc = layout_desc->SetRawData(field_index);
62 : if (details.field_width_in_words() > 1) {
63 : layout_desc = layout_desc->SetRawData(field_index + 1);
64 : }
65 : return handle(layout_desc, isolate);
66 : }
67 :
68 :
69 248953 : Handle<LayoutDescriptor> LayoutDescriptor::AppendIfFastOrUseFull(
70 : Handle<Map> map, PropertyDetails details,
71 : Handle<LayoutDescriptor> full_layout_descriptor) {
72 : DisallowHeapAllocation no_allocation;
73 : LayoutDescriptor* layout_descriptor = map->layout_descriptor();
74 248953 : if (layout_descriptor->IsSlowLayout()) {
75 3128 : return full_layout_descriptor;
76 : }
77 245825 : if (!InobjectUnboxedField(map->GetInObjectProperties(), details)) {
78 : DCHECK(details.location() != kField ||
79 : layout_descriptor->IsTagged(details.field_index()));
80 : return handle(layout_descriptor, map->GetIsolate());
81 : }
82 : int field_index = details.field_index();
83 : int new_capacity = field_index + details.field_width_in_words();
84 3630 : if (new_capacity > layout_descriptor->capacity()) {
85 : // Current map's layout descriptor runs out of space, so use the full
86 : // layout descriptor.
87 97 : return full_layout_descriptor;
88 : }
89 :
90 : layout_descriptor = layout_descriptor->SetRawData(field_index);
91 : if (details.field_width_in_words() > 1) {
92 : layout_descriptor = layout_descriptor->SetRawData(field_index + 1);
93 : }
94 : return handle(layout_descriptor, map->GetIsolate());
95 : }
96 :
97 :
98 13292 : Handle<LayoutDescriptor> LayoutDescriptor::EnsureCapacity(
99 : Isolate* isolate, Handle<LayoutDescriptor> layout_descriptor,
100 : int new_capacity) {
101 : int old_capacity = layout_descriptor->capacity();
102 13292 : if (new_capacity <= old_capacity) {
103 13178 : return layout_descriptor;
104 : }
105 : Handle<LayoutDescriptor> new_layout_descriptor =
106 : LayoutDescriptor::New(isolate, new_capacity);
107 : DCHECK(new_layout_descriptor->IsSlowLayout());
108 :
109 114 : if (layout_descriptor->IsSlowLayout()) {
110 : memcpy(new_layout_descriptor->DataPtr(), layout_descriptor->DataPtr(),
111 28 : layout_descriptor->DataSize());
112 28 : return new_layout_descriptor;
113 : } else {
114 : // Fast layout.
115 : uint32_t value =
116 86 : static_cast<uint32_t>(Smi::cast(*layout_descriptor)->value());
117 : new_layout_descriptor->set(0, value);
118 86 : return new_layout_descriptor;
119 : }
120 : }
121 :
122 :
123 730588 : bool LayoutDescriptor::IsTagged(int field_index, int max_sequence_length,
124 : int* out_sequence_length) {
125 : DCHECK(max_sequence_length > 0);
126 730588 : if (IsFastPointerLayout()) {
127 686 : *out_sequence_length = max_sequence_length;
128 686 : return true;
129 : }
130 :
131 : int layout_word_index;
132 : int layout_bit_index;
133 :
134 729902 : if (!GetIndexes(field_index, &layout_word_index, &layout_bit_index)) {
135 : // Out of bounds queries are considered tagged.
136 280 : *out_sequence_length = max_sequence_length;
137 280 : return true;
138 : }
139 729622 : uint32_t layout_mask = static_cast<uint32_t>(1) << layout_bit_index;
140 :
141 : uint32_t value = IsSlowLayout()
142 : ? get_scalar(layout_word_index)
143 1255875 : : static_cast<uint32_t>(Smi::cast(this)->value());
144 :
145 729622 : bool is_tagged = (value & layout_mask) == 0;
146 729622 : if (!is_tagged) value = ~value; // Count set bits instead of cleared bits.
147 729622 : value = value & ~(layout_mask - 1); // Clear bits we are not interested in.
148 729622 : int sequence_length = CountTrailingZeros32(value) - layout_bit_index;
149 :
150 729622 : if (layout_bit_index + sequence_length == kNumberOfBits) {
151 : // This is a contiguous sequence till the end of current word, proceed
152 : // counting in the subsequent words.
153 203348 : if (IsSlowLayout()) {
154 : int len = length();
155 158173 : ++layout_word_index;
156 549744 : for (; layout_word_index < len; layout_word_index++) {
157 : value = get_scalar(layout_word_index);
158 518889 : bool cur_is_tagged = (value & 1) == 0;
159 518889 : if (cur_is_tagged != is_tagged) break;
160 517625 : if (!is_tagged) value = ~value; // Count set bits instead.
161 517625 : int cur_sequence_length = CountTrailingZeros32(value);
162 517625 : sequence_length += cur_sequence_length;
163 517625 : if (sequence_length >= max_sequence_length) break;
164 406138 : if (cur_sequence_length != kNumberOfBits) break;
165 : }
166 : }
167 319791 : if (is_tagged && (field_index + sequence_length == capacity())) {
168 : // The contiguous sequence of tagged fields lasts till the end of the
169 : // layout descriptor which means that all the fields starting from
170 : // field_index are tagged.
171 : sequence_length = std::numeric_limits<int>::max();
172 : }
173 : }
174 729622 : *out_sequence_length = Min(sequence_length, max_sequence_length);
175 729622 : return is_tagged;
176 : }
177 :
178 :
179 301 : Handle<LayoutDescriptor> LayoutDescriptor::NewForTesting(Isolate* isolate,
180 : int length) {
181 301 : return New(isolate, length);
182 : }
183 :
184 :
185 205828 : LayoutDescriptor* LayoutDescriptor::SetTaggedForTesting(int field_index,
186 : bool tagged) {
187 205828 : return SetTagged(field_index, tagged);
188 : }
189 :
190 :
191 527812 : bool LayoutDescriptorHelper::IsTagged(
192 : int offset_in_bytes, int end_offset,
193 : int* out_end_of_contiguous_region_offset) {
194 : DCHECK(IsAligned(offset_in_bytes, kPointerSize));
195 : DCHECK(IsAligned(end_offset, kPointerSize));
196 : DCHECK(offset_in_bytes < end_offset);
197 527812 : if (all_fields_tagged_) {
198 1582 : *out_end_of_contiguous_region_offset = end_offset;
199 : DCHECK(offset_in_bytes < *out_end_of_contiguous_region_offset);
200 1582 : return true;
201 : }
202 526230 : int max_sequence_length = (end_offset - offset_in_bytes) / kPointerSize;
203 526230 : int field_index = Max(0, (offset_in_bytes - header_size_) / kPointerSize);
204 : int sequence_length;
205 : bool tagged = layout_descriptor_->IsTagged(field_index, max_sequence_length,
206 526230 : &sequence_length);
207 : DCHECK(sequence_length > 0);
208 526230 : if (offset_in_bytes < header_size_) {
209 : // Object headers do not contain non-tagged fields. Check if the contiguous
210 : // region continues after the header.
211 239365 : if (tagged) {
212 : // First field is tagged, calculate end offset from there.
213 : *out_end_of_contiguous_region_offset =
214 12936 : header_size_ + sequence_length * kPointerSize;
215 :
216 : } else {
217 226429 : *out_end_of_contiguous_region_offset = header_size_;
218 : }
219 : DCHECK(offset_in_bytes < *out_end_of_contiguous_region_offset);
220 : return true;
221 : }
222 : *out_end_of_contiguous_region_offset =
223 286865 : offset_in_bytes + sequence_length * kPointerSize;
224 : DCHECK(offset_in_bytes < *out_end_of_contiguous_region_offset);
225 286865 : return tagged;
226 : }
227 :
228 :
229 14592 : LayoutDescriptor* LayoutDescriptor::Trim(Heap* heap, Map* map,
230 : DescriptorArray* descriptors,
231 : int num_descriptors) {
232 : DisallowHeapAllocation no_allocation;
233 : // Fast mode descriptors are never shared and therefore always fully
234 : // correspond to their map.
235 14592 : if (!IsSlowLayout()) return this;
236 :
237 : int layout_descriptor_length =
238 : CalculateCapacity(map, descriptors, num_descriptors);
239 : // It must not become fast-mode descriptor here, because otherwise it has to
240 : // be fast pointer layout descriptor already but it's is slow mode now.
241 : DCHECK_LT(kSmiValueSize, layout_descriptor_length);
242 :
243 : // Trim, clean and reinitialize this slow-mode layout descriptor.
244 : int array_length = GetSlowModeBackingStoreLength(layout_descriptor_length);
245 : int current_length = length();
246 37 : if (current_length != array_length) {
247 : DCHECK_LT(array_length, current_length);
248 7 : int delta = current_length - array_length;
249 7 : heap->RightTrimFixedArray(this, delta);
250 : }
251 37 : memset(DataPtr(), 0, DataSize());
252 : LayoutDescriptor* layout_descriptor =
253 : Initialize(this, map, descriptors, num_descriptors);
254 : DCHECK_EQ(this, layout_descriptor);
255 : return layout_descriptor;
256 : }
257 :
258 :
259 9583 : bool LayoutDescriptor::IsConsistentWithMap(Map* map, bool check_tail) {
260 : if (FLAG_unbox_double_fields) {
261 : DescriptorArray* descriptors = map->instance_descriptors();
262 : int nof_descriptors = map->NumberOfOwnDescriptors();
263 : int last_field_index = 0;
264 516145 : for (int i = 0; i < nof_descriptors; i++) {
265 506562 : PropertyDetails details = descriptors->GetDetails(i);
266 551838 : if (details.location() != kField) continue;
267 461286 : FieldIndex field_index = FieldIndex::ForDescriptor(map, i);
268 : bool tagged_expected =
269 770952 : !field_index.is_inobject() || !details.representation().IsDouble();
270 922572 : for (int bit = 0; bit < details.field_width_in_words(); bit++) {
271 461286 : bool tagged_actual = IsTagged(details.field_index() + bit);
272 : DCHECK_EQ(tagged_expected, tagged_actual);
273 461286 : if (tagged_actual != tagged_expected) return false;
274 : }
275 : last_field_index =
276 : Max(last_field_index,
277 : details.field_index() + details.field_width_in_words());
278 : }
279 9583 : if (check_tail) {
280 : int n = capacity();
281 : for (int i = last_field_index; i < n; i++) {
282 : DCHECK(IsTagged(i));
283 : }
284 : }
285 : }
286 : return true;
287 : }
288 : } // namespace internal
289 : } // namespace v8
|
