1 /* 2 * Copyright (c) 2020, 2024, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. 8 * 9 * This code is distributed in the hope that it will be useful, but WITHOUT 10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 12 * version 2 for more details (a copy is included in the LICENSE file that 13 * accompanied this code). 14 * 15 * You should have received a copy of the GNU General Public License version 16 * 2 along with this work; if not, write to the Free Software Foundation, 17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 18 * 19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 20 * or visit www.oracle.com if you need additional information or have any 21 * questions. 22 * 23 */ 24 25 #include "precompiled.hpp" 26 #include "classfile/classFileParser.hpp" 27 #include "classfile/fieldLayoutBuilder.hpp" 28 #include "classfile/systemDictionary.hpp" 29 #include "classfile/vmSymbols.hpp" 30 #include "jvm.h" 31 #include "memory/resourceArea.hpp" 32 #include "oops/array.hpp" 33 #include "oops/fieldStreams.inline.hpp" 34 #include "oops/instanceMirrorKlass.hpp" 35 #include "oops/instanceKlass.inline.hpp" 36 #include "oops/klass.inline.hpp" 37 #include "oops/inlineKlass.inline.hpp" 38 #include "runtime/fieldDescriptor.inline.hpp" 39 #include "utilities/powerOfTwo.hpp" 40 41 static LayoutKind field_layout_selection(FieldInfo field_info, Array<InlineLayoutInfo>* inline_layout_info_array, 42 bool use_atomic_flat) { 43 44 if (field_info.field_flags().is_injected()) { 45 // don't flatten injected fields 46 return LayoutKind::REFERENCE; 47 } 48 49 if (inline_layout_info_array == nullptr || inline_layout_info_array->adr_at(field_info.index())->klass() == nullptr) { 50 // field's type is not a known value class, using a reference 51 return LayoutKind::REFERENCE; 52 } 53 54 InlineLayoutInfo* inline_field_info = inline_layout_info_array->adr_at(field_info.index()); 55 InlineKlass* vk = inline_field_info->klass(); 56 57 if (field_info.field_flags().is_null_free_inline_type()) { 58 assert(vk->is_implicitly_constructible(), "null-free fields must be implicitly constructible"); 59 if (vk->must_be_atomic() || field_info.access_flags().is_volatile() || AlwaysAtomicAccesses) { 60 if (vk->is_naturally_atomic() && vk->has_non_atomic_layout()) return LayoutKind::NON_ATOMIC_FLAT; 61 return (vk->has_atomic_layout() && use_atomic_flat) ? LayoutKind::ATOMIC_FLAT : LayoutKind::REFERENCE; 62 } else { 63 return vk->has_non_atomic_layout() ? LayoutKind::NON_ATOMIC_FLAT : LayoutKind::REFERENCE; 64 } 65 } else { 66 if (NullableFieldFlattening && vk->has_nullable_layout()) { 67 return use_atomic_flat ? LayoutKind::NULLABLE_ATOMIC_FLAT : LayoutKind::REFERENCE; 68 } else { 69 return LayoutKind::REFERENCE; 70 } 71 } 72 } 73 74 static void get_size_and_alignment(InlineKlass* vk, LayoutKind kind, int* size, int* alignment) { 75 switch(kind) { 76 case LayoutKind::NON_ATOMIC_FLAT: 77 *size = vk->non_atomic_size_in_bytes(); 78 *alignment = vk->non_atomic_alignment(); 79 break; 80 case LayoutKind::ATOMIC_FLAT: 81 *size = vk->atomic_size_in_bytes(); 82 *alignment = *size; 83 break; 84 case LayoutKind::NULLABLE_ATOMIC_FLAT: 85 *size = vk->nullable_size_in_bytes(); 86 *alignment = *size; 87 break; 88 default: 89 ShouldNotReachHere(); 90 } 91 } 92 93 LayoutRawBlock::LayoutRawBlock(Kind kind, int size) : 94 _next_block(nullptr), 95 _prev_block(nullptr), 96 _inline_klass(nullptr), 97 _block_kind(kind), 98 _offset(-1), 99 _alignment(1), 100 _size(size), 101 _field_index(-1) { 102 assert(kind == EMPTY || kind == RESERVED || kind == PADDING || kind == INHERITED || kind == NULL_MARKER, 103 "Otherwise, should use the constructor with a field index argument"); 104 assert(size > 0, "Sanity check"); 105 } 106 107 108 LayoutRawBlock::LayoutRawBlock(int index, Kind kind, int size, int alignment) : 109 _next_block(nullptr), 110 _prev_block(nullptr), 111 _inline_klass(nullptr), 112 _block_kind(kind), 113 _offset(-1), 114 _alignment(alignment), 115 _size(size), 116 _field_index(index) { 117 assert(kind == REGULAR || kind == FLAT || kind == INHERITED, 118 "Other kind do not have a field index"); 119 assert(size > 0, "Sanity check"); 120 assert(alignment > 0, "Sanity check"); 121 } 122 123 bool LayoutRawBlock::fit(int size, int alignment) { 124 int adjustment = 0; 125 if ((_offset % alignment) != 0) { 126 adjustment = alignment - (_offset % alignment); 127 } 128 return _size >= size + adjustment; 129 } 130 131 FieldGroup::FieldGroup(int contended_group) : 132 _next(nullptr), 133 _small_primitive_fields(nullptr), 134 _big_primitive_fields(nullptr), 135 _oop_fields(nullptr), 136 _contended_group(contended_group), // -1 means no contended group, 0 means default contended group 137 _oop_count(0) {} 138 139 void FieldGroup::add_primitive_field(int idx, BasicType type) { 140 int size = type2aelembytes(type); 141 LayoutRawBlock* block = new LayoutRawBlock(idx, LayoutRawBlock::REGULAR, size, size /* alignment == size for primitive types */); 142 if (size >= oopSize) { 143 add_to_big_primitive_list(block); 144 } else { 145 add_to_small_primitive_list(block); 146 } 147 } 148 149 void FieldGroup::add_oop_field(int idx) { 150 int size = type2aelembytes(T_OBJECT); 151 LayoutRawBlock* block = new LayoutRawBlock(idx, LayoutRawBlock::REGULAR, size, size /* alignment == size for oops */); 152 if (_oop_fields == nullptr) { 153 _oop_fields = new GrowableArray<LayoutRawBlock*>(INITIAL_LIST_SIZE); 154 } 155 _oop_fields->append(block); 156 _oop_count++; 157 } 158 159 void FieldGroup::add_flat_field(int idx, InlineKlass* vk, LayoutKind lk, int size, int alignment) { 160 LayoutRawBlock* block = new LayoutRawBlock(idx, LayoutRawBlock::FLAT, size, alignment); 161 block->set_inline_klass(vk); 162 block->set_layout_kind(lk); 163 if (block->size() >= oopSize) { 164 add_to_big_primitive_list(block); 165 } else { 166 add_to_small_primitive_list(block); 167 } 168 } 169 170 void FieldGroup::sort_by_size() { 171 if (_small_primitive_fields != nullptr) { 172 _small_primitive_fields->sort(LayoutRawBlock::compare_size_inverted); 173 } 174 if (_big_primitive_fields != nullptr) { 175 _big_primitive_fields->sort(LayoutRawBlock::compare_size_inverted); 176 } 177 } 178 179 void FieldGroup::add_to_small_primitive_list(LayoutRawBlock* block) { 180 if (_small_primitive_fields == nullptr) { 181 _small_primitive_fields = new GrowableArray<LayoutRawBlock*>(INITIAL_LIST_SIZE); 182 } 183 _small_primitive_fields->append(block); 184 } 185 186 void FieldGroup::add_to_big_primitive_list(LayoutRawBlock* block) { 187 if (_big_primitive_fields == nullptr) { 188 _big_primitive_fields = new GrowableArray<LayoutRawBlock*>(INITIAL_LIST_SIZE); 189 } 190 _big_primitive_fields->append(block); 191 } 192 193 FieldLayout::FieldLayout(GrowableArray<FieldInfo>* field_info, Array<InlineLayoutInfo>* inline_layout_info_array, ConstantPool* cp) : 194 _field_info(field_info), 195 _inline_layout_info_array(inline_layout_info_array), 196 _cp(cp), 197 _blocks(nullptr), 198 _start(_blocks), 199 _last(_blocks), 200 _super_first_field_offset(-1), 201 _super_alignment(-1), 202 _super_min_align_required(-1), 203 _default_value_offset(-1), 204 _null_reset_value_offset(-1), 205 _super_has_fields(false), 206 _has_inherited_fields(false) {} 207 208 void FieldLayout::initialize_static_layout() { 209 _blocks = new LayoutRawBlock(LayoutRawBlock::EMPTY, INT_MAX); 210 _blocks->set_offset(0); 211 _last = _blocks; 212 _start = _blocks; 213 // Note: at this stage, InstanceMirrorKlass::offset_of_static_fields() could be zero, because 214 // during bootstrapping, the size of the java.lang.Class is still not known when layout 215 // of static field is computed. Field offsets are fixed later when the size is known 216 // (see java_lang_Class::fixup_mirror()) 217 if (InstanceMirrorKlass::offset_of_static_fields() > 0) { 218 insert(first_empty_block(), new LayoutRawBlock(LayoutRawBlock::RESERVED, InstanceMirrorKlass::offset_of_static_fields())); 219 _blocks->set_offset(0); 220 } 221 } 222 223 void FieldLayout::initialize_instance_layout(const InstanceKlass* super_klass) { 224 if (super_klass == nullptr) { 225 _blocks = new LayoutRawBlock(LayoutRawBlock::EMPTY, INT_MAX); 226 _blocks->set_offset(0); 227 _last = _blocks; 228 _start = _blocks; 229 insert(first_empty_block(), new LayoutRawBlock(LayoutRawBlock::RESERVED, instanceOopDesc::base_offset_in_bytes())); 230 } else { 231 _super_has_fields = reconstruct_layout(super_klass); 232 fill_holes(super_klass); 233 if ((!super_klass->has_contended_annotations()) || !_super_has_fields) { 234 _start = _blocks; // start allocating fields from the first empty block 235 } else { 236 _start = _last; // append fields at the end of the reconstructed layout 237 } 238 } 239 } 240 241 LayoutRawBlock* FieldLayout::first_field_block() { 242 LayoutRawBlock* block = _blocks; 243 while (block != nullptr 244 && block->block_kind() != LayoutRawBlock::INHERITED 245 && block->block_kind() != LayoutRawBlock::REGULAR 246 && block->block_kind() != LayoutRawBlock::FLAT 247 && block->block_kind() != LayoutRawBlock::NULL_MARKER) { 248 block = block->next_block(); 249 } 250 return block; 251 } 252 253 // Insert a set of fields into a layout. 254 // For each field, search for an empty slot able to fit the field 255 // (satisfying both size and alignment requirements), if none is found, 256 // add the field at the end of the layout. 257 // Fields cannot be inserted before the block specified in the "start" argument 258 void FieldLayout::add(GrowableArray<LayoutRawBlock*>* list, LayoutRawBlock* start) { 259 if (list == nullptr) return; 260 if (start == nullptr) start = this->_start; 261 bool last_search_success = false; 262 int last_size = 0; 263 int last_alignment = 0; 264 for (int i = 0; i < list->length(); i ++) { 265 LayoutRawBlock* b = list->at(i); 266 LayoutRawBlock* cursor = nullptr; 267 LayoutRawBlock* candidate = nullptr; 268 // if start is the last block, just append the field 269 if (start == last_block()) { 270 candidate = last_block(); 271 } 272 // Before iterating over the layout to find an empty slot fitting the field's requirements, 273 // check if the previous field had the same requirements and if the search for a fitting slot 274 // was successful. If the requirements were the same but the search failed, a new search will 275 // fail the same way, so just append the field at the of the layout. 276 else if (b->size() == last_size && b->alignment() == last_alignment && !last_search_success) { 277 candidate = last_block(); 278 } else { 279 // Iterate over the layout to find an empty slot fitting the field's requirements 280 last_size = b->size(); 281 last_alignment = b->alignment(); 282 cursor = last_block()->prev_block(); 283 assert(cursor != nullptr, "Sanity check"); 284 last_search_success = true; 285 286 while (cursor != start) { 287 if (cursor->block_kind() == LayoutRawBlock::EMPTY && cursor->fit(b->size(), b->alignment())) { 288 if (candidate == nullptr || cursor->size() < candidate->size()) { 289 candidate = cursor; 290 } 291 } 292 cursor = cursor->prev_block(); 293 } 294 if (candidate == nullptr) { 295 candidate = last_block(); 296 last_search_success = false; 297 } 298 assert(candidate != nullptr, "Candidate must not be null"); 299 assert(candidate->block_kind() == LayoutRawBlock::EMPTY, "Candidate must be an empty block"); 300 assert(candidate->fit(b->size(), b->alignment()), "Candidate must be able to store the block"); 301 } 302 insert_field_block(candidate, b); 303 } 304 } 305 306 // Used for classes with hard coded field offsets, insert a field at the specified offset */ 307 void FieldLayout::add_field_at_offset(LayoutRawBlock* block, int offset, LayoutRawBlock* start) { 308 assert(block != nullptr, "Sanity check"); 309 block->set_offset(offset); 310 if (start == nullptr) { 311 start = this->_start; 312 } 313 LayoutRawBlock* slot = start; 314 while (slot != nullptr) { 315 if ((slot->offset() <= block->offset() && (slot->offset() + slot->size()) > block->offset()) || 316 slot == _last){ 317 assert(slot->block_kind() == LayoutRawBlock::EMPTY, "Matching slot must be an empty slot"); 318 assert(slot->size() >= block->offset() - slot->offset() + block->size() ,"Matching slot must be big enough"); 319 if (slot->offset() < block->offset()) { 320 int adjustment = block->offset() - slot->offset(); 321 LayoutRawBlock* adj = new LayoutRawBlock(LayoutRawBlock::EMPTY, adjustment); 322 insert(slot, adj); 323 } 324 insert(slot, block); 325 if (slot->size() == 0) { 326 remove(slot); 327 } 328 if (block->block_kind() == LayoutRawBlock::REGULAR || block->block_kind() == LayoutRawBlock::FLAT) { 329 _field_info->adr_at(block->field_index())->set_offset(block->offset()); 330 } 331 return; 332 } 333 slot = slot->next_block(); 334 } 335 fatal("Should have found a matching slot above, corrupted layout or invalid offset"); 336 } 337 338 // The allocation logic uses a best fit strategy: the set of fields is allocated 339 // in the first empty slot big enough to contain the whole set ((including padding 340 // to fit alignment constraints). 341 void FieldLayout::add_contiguously(GrowableArray<LayoutRawBlock*>* list, LayoutRawBlock* start) { 342 if (list == nullptr) return; 343 if (start == nullptr) { 344 start = _start; 345 } 346 // This code assumes that if the first block is well aligned, the following 347 // blocks would naturally be well aligned (no need for adjustment) 348 int size = 0; 349 for (int i = 0; i < list->length(); i++) { 350 size += list->at(i)->size(); 351 } 352 353 LayoutRawBlock* candidate = nullptr; 354 if (start == last_block()) { 355 candidate = last_block(); 356 } else { 357 LayoutRawBlock* first = list->at(0); 358 candidate = last_block()->prev_block(); 359 while (candidate->block_kind() != LayoutRawBlock::EMPTY || !candidate->fit(size, first->alignment())) { 360 if (candidate == start) { 361 candidate = last_block(); 362 break; 363 } 364 candidate = candidate->prev_block(); 365 } 366 assert(candidate != nullptr, "Candidate must not be null"); 367 assert(candidate->block_kind() == LayoutRawBlock::EMPTY, "Candidate must be an empty block"); 368 assert(candidate->fit(size, first->alignment()), "Candidate must be able to store the whole contiguous block"); 369 } 370 371 for (int i = 0; i < list->length(); i++) { 372 LayoutRawBlock* b = list->at(i); 373 insert_field_block(candidate, b); 374 assert((candidate->offset() % b->alignment() == 0), "Contiguous blocks must be naturally well aligned"); 375 } 376 } 377 378 LayoutRawBlock* FieldLayout::insert_field_block(LayoutRawBlock* slot, LayoutRawBlock* block) { 379 assert(slot->block_kind() == LayoutRawBlock::EMPTY, "Blocks can only be inserted in empty blocks"); 380 if (slot->offset() % block->alignment() != 0) { 381 int adjustment = block->alignment() - (slot->offset() % block->alignment()); 382 LayoutRawBlock* adj = new LayoutRawBlock(LayoutRawBlock::EMPTY, adjustment); 383 insert(slot, adj); 384 } 385 assert(block->size() >= block->size(), "Enough space must remain after adjustment"); 386 insert(slot, block); 387 if (slot->size() == 0) { 388 remove(slot); 389 } 390 // NULL_MARKER blocks are not real fields, so they don't have an entry in the FieldInfo array 391 if (block->block_kind() != LayoutRawBlock::NULL_MARKER) { 392 _field_info->adr_at(block->field_index())->set_offset(block->offset()); 393 if (_field_info->adr_at(block->field_index())->name(_cp) == vmSymbols::default_value_name()) { 394 _default_value_offset = block->offset(); 395 } 396 if (_field_info->adr_at(block->field_index())->name(_cp) == vmSymbols::null_reset_value_name()) { 397 _null_reset_value_offset = block->offset(); 398 } 399 } 400 if (block->block_kind() == LayoutRawBlock::FLAT && block->layout_kind() == LayoutKind::NULLABLE_ATOMIC_FLAT) { 401 int nm_offset = block->inline_klass()->null_marker_offset() - block->inline_klass()->first_field_offset() + block->offset(); 402 _field_info->adr_at(block->field_index())->set_null_marker_offset(nm_offset); 403 _inline_layout_info_array->adr_at(block->field_index())->set_null_marker_offset(nm_offset); 404 } 405 406 return block; 407 } 408 409 bool FieldLayout::reconstruct_layout(const InstanceKlass* ik) { 410 bool has_instance_fields = false; 411 if (ik->is_abstract() && !ik->is_identity_class()) { 412 _super_alignment = type2aelembytes(BasicType::T_LONG); 413 } 414 GrowableArray<LayoutRawBlock*>* all_fields = new GrowableArray<LayoutRawBlock*>(32); 415 while (ik != nullptr) { 416 for (AllFieldStream fs(ik->fieldinfo_stream(), ik->constants()); !fs.done(); fs.next()) { 417 BasicType type = Signature::basic_type(fs.signature()); 418 // distinction between static and non-static fields is missing 419 if (fs.access_flags().is_static()) continue; 420 has_instance_fields = true; 421 _has_inherited_fields = true; 422 if (_super_first_field_offset == -1 || fs.offset() < _super_first_field_offset) _super_first_field_offset = fs.offset(); 423 LayoutRawBlock* block; 424 if (fs.is_flat()) { 425 InlineLayoutInfo layout_info = ik->inline_layout_info(fs.index()); 426 InlineKlass* vk = layout_info.klass(); 427 block = new LayoutRawBlock(fs.index(), LayoutRawBlock::INHERITED, 428 vk->layout_size_in_bytes(layout_info.kind()), 429 vk->layout_alignment(layout_info.kind())); 430 assert(_super_alignment == -1 || _super_alignment >= vk->payload_alignment(), "Invalid value alignment"); 431 _super_min_align_required = _super_min_align_required > vk->payload_alignment() ? _super_min_align_required : vk->payload_alignment(); 432 } else { 433 int size = type2aelembytes(type); 434 // INHERITED blocks are marked as non-reference because oop_maps are handled by their holder class 435 block = new LayoutRawBlock(fs.index(), LayoutRawBlock::INHERITED, size, size); 436 // For primitive types, the alignment is equal to the size 437 assert(_super_alignment == -1 || _super_alignment >= size, "Invalid value alignment"); 438 _super_min_align_required = _super_min_align_required > size ? _super_min_align_required : size; 439 } 440 block->set_offset(fs.offset()); 441 all_fields->append(block); 442 } 443 ik = ik->super() == nullptr ? nullptr : InstanceKlass::cast(ik->super()); 444 } 445 all_fields->sort(LayoutRawBlock::compare_offset); 446 _blocks = new LayoutRawBlock(LayoutRawBlock::RESERVED, instanceOopDesc::base_offset_in_bytes()); 447 _blocks->set_offset(0); 448 _last = _blocks; 449 for(int i = 0; i < all_fields->length(); i++) { 450 LayoutRawBlock* b = all_fields->at(i); 451 _last->set_next_block(b); 452 b->set_prev_block(_last); 453 _last = b; 454 } 455 _start = _blocks; 456 return has_instance_fields; 457 } 458 459 // Called during the reconstruction of a layout, after fields from super 460 // classes have been inserted. It fills unused slots between inserted fields 461 // with EMPTY blocks, so the regular field insertion methods would work. 462 // This method handles classes with @Contended annotations differently 463 // by inserting PADDING blocks instead of EMPTY block to prevent subclasses' 464 // fields to interfere with contended fields/classes. 465 void FieldLayout::fill_holes(const InstanceKlass* super_klass) { 466 assert(_blocks != nullptr, "Sanity check"); 467 assert(_blocks->offset() == 0, "first block must be at offset zero"); 468 LayoutRawBlock::Kind filling_type = super_klass->has_contended_annotations() ? LayoutRawBlock::PADDING: LayoutRawBlock::EMPTY; 469 LayoutRawBlock* b = _blocks; 470 while (b->next_block() != nullptr) { 471 if (b->next_block()->offset() > (b->offset() + b->size())) { 472 int size = b->next_block()->offset() - (b->offset() + b->size()); 473 // FIXME it would be better if initial empty block where tagged as PADDING for value classes 474 LayoutRawBlock* empty = new LayoutRawBlock(filling_type, size); 475 empty->set_offset(b->offset() + b->size()); 476 empty->set_next_block(b->next_block()); 477 b->next_block()->set_prev_block(empty); 478 b->set_next_block(empty); 479 empty->set_prev_block(b); 480 } 481 b = b->next_block(); 482 } 483 assert(b->next_block() == nullptr, "Invariant at this point"); 484 assert(b->block_kind() != LayoutRawBlock::EMPTY, "Sanity check"); 485 // If the super class has @Contended annotation, a padding block is 486 // inserted at the end to ensure that fields from the subclasses won't share 487 // the cache line of the last field of the contended class 488 if (super_klass->has_contended_annotations() && ContendedPaddingWidth > 0) { 489 LayoutRawBlock* p = new LayoutRawBlock(LayoutRawBlock::PADDING, ContendedPaddingWidth); 490 p->set_offset(b->offset() + b->size()); 491 b->set_next_block(p); 492 p->set_prev_block(b); 493 b = p; 494 } 495 496 LayoutRawBlock* last = new LayoutRawBlock(LayoutRawBlock::EMPTY, INT_MAX); 497 last->set_offset(b->offset() + b->size()); 498 assert(last->offset() > 0, "Sanity check"); 499 b->set_next_block(last); 500 last->set_prev_block(b); 501 _last = last; 502 } 503 504 LayoutRawBlock* FieldLayout::insert(LayoutRawBlock* slot, LayoutRawBlock* block) { 505 assert(slot->block_kind() == LayoutRawBlock::EMPTY, "Blocks can only be inserted in empty blocks"); 506 assert(slot->offset() % block->alignment() == 0, "Incompatible alignment"); 507 block->set_offset(slot->offset()); 508 slot->set_offset(slot->offset() + block->size()); 509 assert((slot->size() - block->size()) < slot->size(), "underflow checking"); 510 assert(slot->size() - block->size() >= 0, "no negative size allowed"); 511 slot->set_size(slot->size() - block->size()); 512 block->set_prev_block(slot->prev_block()); 513 block->set_next_block(slot); 514 slot->set_prev_block(block); 515 if (block->prev_block() != nullptr) { 516 block->prev_block()->set_next_block(block); 517 } 518 if (_blocks == slot) { 519 _blocks = block; 520 } 521 if (_start == slot) { 522 _start = block; 523 } 524 return block; 525 } 526 527 void FieldLayout::remove(LayoutRawBlock* block) { 528 assert(block != nullptr, "Sanity check"); 529 assert(block != _last, "Sanity check"); 530 if (_blocks == block) { 531 _blocks = block->next_block(); 532 if (_blocks != nullptr) { 533 _blocks->set_prev_block(nullptr); 534 } 535 } else { 536 assert(block->prev_block() != nullptr, "_prev should be set for non-head blocks"); 537 block->prev_block()->set_next_block(block->next_block()); 538 block->next_block()->set_prev_block(block->prev_block()); 539 } 540 if (block == _start) { 541 _start = block->prev_block(); 542 } 543 } 544 545 void FieldLayout::shift_fields(int shift) { 546 LayoutRawBlock* b = first_field_block(); 547 LayoutRawBlock* previous = b->prev_block(); 548 if (previous->block_kind() == LayoutRawBlock::EMPTY) { 549 previous->set_size(previous->size() + shift); 550 } else { 551 LayoutRawBlock* nb = new LayoutRawBlock(LayoutRawBlock::PADDING, shift); 552 nb->set_offset(b->offset()); 553 previous->set_next_block(nb); 554 nb->set_prev_block(previous); 555 b->set_prev_block(nb); 556 nb->set_next_block(b); 557 } 558 while (b != nullptr) { 559 b->set_offset(b->offset() + shift); 560 if (b->block_kind() == LayoutRawBlock::REGULAR || b->block_kind() == LayoutRawBlock::FLAT) { 561 _field_info->adr_at(b->field_index())->set_offset(b->offset()); 562 if (b->layout_kind() == LayoutKind::NULLABLE_ATOMIC_FLAT) { 563 int new_nm_offset = _field_info->adr_at(b->field_index())->null_marker_offset() + shift; 564 _field_info->adr_at(b->field_index())->set_null_marker_offset(new_nm_offset); 565 _inline_layout_info_array->adr_at(b->field_index())->set_null_marker_offset(new_nm_offset); 566 567 } 568 } 569 assert(b->block_kind() == LayoutRawBlock::EMPTY || b->offset() % b->alignment() == 0, "Must still be correctly aligned"); 570 b = b->next_block(); 571 } 572 } 573 574 LayoutRawBlock* FieldLayout::find_null_marker() { 575 LayoutRawBlock* b = _blocks; 576 while (b != nullptr) { 577 if (b->block_kind() == LayoutRawBlock::NULL_MARKER) { 578 return b; 579 } 580 b = b->next_block(); 581 } 582 ShouldNotReachHere(); 583 } 584 585 void FieldLayout::remove_null_marker() { 586 LayoutRawBlock* b = first_field_block(); 587 while (b != nullptr) { 588 if (b->block_kind() == LayoutRawBlock::NULL_MARKER) { 589 if (b->next_block()->block_kind() == LayoutRawBlock::EMPTY) { 590 LayoutRawBlock* n = b->next_block(); 591 remove(b); 592 n->set_offset(b->offset()); 593 n->set_size(n->size() + b->size()); 594 } else { 595 b->set_block_kind(LayoutRawBlock::EMPTY); 596 } 597 return; 598 } 599 b = b->next_block(); 600 } 601 ShouldNotReachHere(); // if we reach this point, the null marker was not found! 602 } 603 604 static const char* layout_kind_to_string(LayoutKind lk) { 605 switch(lk) { 606 case LayoutKind::REFERENCE: 607 return "REFERENCE"; 608 case LayoutKind::NON_ATOMIC_FLAT: 609 return "NON_ATOMIC_FLAT"; 610 case LayoutKind::ATOMIC_FLAT: 611 return "ATOMIC_FLAT"; 612 case LayoutKind::NULLABLE_ATOMIC_FLAT: 613 return "NULLABLE_ATOMIC_FLAT"; 614 case LayoutKind::UNKNOWN: 615 return "UNKNOWN"; 616 default: 617 ShouldNotReachHere(); 618 } 619 } 620 621 void FieldLayout::print(outputStream* output, bool is_static, const InstanceKlass* super, Array<InlineLayoutInfo>* inline_fields) { 622 ResourceMark rm; 623 LayoutRawBlock* b = _blocks; 624 while(b != _last) { 625 switch(b->block_kind()) { 626 case LayoutRawBlock::REGULAR: { 627 FieldInfo* fi = _field_info->adr_at(b->field_index()); 628 output->print_cr(" @%d %s %d/%d \"%s\" %s", 629 b->offset(), 630 "REGULAR", 631 b->size(), 632 b->alignment(), 633 fi->name(_cp)->as_C_string(), 634 fi->signature(_cp)->as_C_string()); 635 break; 636 } 637 case LayoutRawBlock::FLAT: { 638 FieldInfo* fi = _field_info->adr_at(b->field_index()); 639 InlineKlass* ik = inline_fields->adr_at(fi->index())->klass(); 640 assert(ik != nullptr, ""); 641 output->print_cr(" @%d %s %d/%d \"%s\" %s %s@%p %s", 642 b->offset(), 643 "FLAT", 644 b->size(), 645 b->alignment(), 646 fi->name(_cp)->as_C_string(), 647 fi->signature(_cp)->as_C_string(), 648 ik->name()->as_C_string(), 649 ik->class_loader_data(), layout_kind_to_string(b->layout_kind())); 650 break; 651 } 652 case LayoutRawBlock::RESERVED: { 653 output->print_cr(" @%d %s %d/-", 654 b->offset(), 655 "RESERVED", 656 b->size()); 657 break; 658 } 659 case LayoutRawBlock::INHERITED: { 660 assert(!is_static, "Static fields are not inherited in layouts"); 661 assert(super != nullptr, "super klass must be provided to retrieve inherited fields info"); 662 bool found = false; 663 const InstanceKlass* ik = super; 664 while (!found && ik != nullptr) { 665 for (AllFieldStream fs(ik->fieldinfo_stream(), ik->constants()); !fs.done(); fs.next()) { 666 if (fs.offset() == b->offset() && fs.access_flags().is_static() == is_static) { 667 output->print_cr(" @%d %s %d/%d \"%s\" %s", 668 b->offset(), 669 "INHERITED", 670 b->size(), 671 b->size(), // so far, alignment constraint == size, will change with Valhalla => FIXME 672 fs.name()->as_C_string(), 673 fs.signature()->as_C_string()); 674 found = true; 675 break; 676 } 677 } 678 ik = ik->java_super(); 679 } 680 break; 681 } 682 case LayoutRawBlock::EMPTY: 683 output->print_cr(" @%d %s %d/1", 684 b->offset(), 685 "EMPTY", 686 b->size()); 687 break; 688 case LayoutRawBlock::PADDING: 689 output->print_cr(" @%d %s %d/1", 690 b->offset(), 691 "PADDING", 692 b->size()); 693 break; 694 case LayoutRawBlock::NULL_MARKER: 695 { 696 output->print_cr(" @%d %s %d/1 ", 697 b->offset(), 698 "NULL_MARKER", 699 b->size()); 700 break; 701 } 702 default: 703 fatal("Unknown block type"); 704 } 705 b = b->next_block(); 706 } 707 } 708 709 FieldLayoutBuilder::FieldLayoutBuilder(const Symbol* classname, ClassLoaderData* loader_data, const InstanceKlass* super_klass, ConstantPool* constant_pool, 710 GrowableArray<FieldInfo>* field_info, bool is_contended, bool is_inline_type,bool is_abstract_value, 711 bool must_be_atomic, FieldLayoutInfo* info, Array<InlineLayoutInfo>* inline_layout_info_array) : 712 _classname(classname), 713 _loader_data(loader_data), 714 _super_klass(super_klass), 715 _constant_pool(constant_pool), 716 _field_info(field_info), 717 _info(info), 718 _inline_layout_info_array(inline_layout_info_array), 719 _root_group(nullptr), 720 _contended_groups(GrowableArray<FieldGroup*>(8)), 721 _static_fields(nullptr), 722 _layout(nullptr), 723 _static_layout(nullptr), 724 _nonstatic_oopmap_count(0), 725 _payload_alignment(-1), 726 _first_field_offset(-1), 727 _null_marker_offset(-1), 728 _payload_size_in_bytes(-1), 729 _non_atomic_layout_size_in_bytes(-1), 730 _non_atomic_layout_alignment(-1), 731 _atomic_layout_size_in_bytes(-1), 732 _nullable_layout_size_in_bytes(-1), 733 _fields_size_sum(0), 734 _declared_non_static_fields_count(0), 735 _has_non_naturally_atomic_fields(false), 736 _is_naturally_atomic(false), 737 _must_be_atomic(must_be_atomic), 738 _has_nonstatic_fields(false), 739 _has_inline_type_fields(false), 740 _is_contended(is_contended), 741 _is_inline_type(is_inline_type), 742 _is_abstract_value(is_abstract_value), 743 _has_flattening_information(is_inline_type), 744 _is_empty_inline_class(false) {} 745 746 FieldGroup* FieldLayoutBuilder::get_or_create_contended_group(int g) { 747 assert(g > 0, "must only be called for named contended groups"); 748 FieldGroup* fg = nullptr; 749 for (int i = 0; i < _contended_groups.length(); i++) { 750 fg = _contended_groups.at(i); 751 if (fg->contended_group() == g) return fg; 752 } 753 fg = new FieldGroup(g); 754 _contended_groups.append(fg); 755 return fg; 756 } 757 758 void FieldLayoutBuilder::prologue() { 759 _layout = new FieldLayout(_field_info, _inline_layout_info_array, _constant_pool); 760 const InstanceKlass* super_klass = _super_klass; 761 _layout->initialize_instance_layout(super_klass); 762 _nonstatic_oopmap_count = super_klass == nullptr ? 0 : super_klass->nonstatic_oop_map_count(); 763 if (super_klass != nullptr) { 764 _has_nonstatic_fields = super_klass->has_nonstatic_fields(); 765 } 766 _static_layout = new FieldLayout(_field_info, _inline_layout_info_array, _constant_pool); 767 _static_layout->initialize_static_layout(); 768 _static_fields = new FieldGroup(); 769 _root_group = new FieldGroup(); 770 } 771 772 // Field sorting for regular (non-inline) classes: 773 // - fields are sorted in static and non-static fields 774 // - non-static fields are also sorted according to their contention group 775 // (support of the @Contended annotation) 776 // - @Contended annotation is ignored for static fields 777 // - field flattening decisions are taken in this method 778 void FieldLayoutBuilder::regular_field_sorting() { 779 int idx = 0; 780 for (GrowableArrayIterator<FieldInfo> it = _field_info->begin(); it != _field_info->end(); ++it, ++idx) { 781 FieldGroup* group = nullptr; 782 FieldInfo fieldinfo = *it; 783 if (fieldinfo.access_flags().is_static()) { 784 group = _static_fields; 785 } else { 786 _has_nonstatic_fields = true; 787 if (fieldinfo.field_flags().is_contended()) { 788 int g = fieldinfo.contended_group(); 789 if (g == 0) { 790 group = new FieldGroup(true); 791 _contended_groups.append(group); 792 } else { 793 group = get_or_create_contended_group(g); 794 } 795 } else { 796 group = _root_group; 797 } 798 } 799 assert(group != nullptr, "invariant"); 800 BasicType type = Signature::basic_type(fieldinfo.signature(_constant_pool)); 801 switch(type) { 802 case T_BYTE: 803 case T_CHAR: 804 case T_DOUBLE: 805 case T_FLOAT: 806 case T_INT: 807 case T_LONG: 808 case T_SHORT: 809 case T_BOOLEAN: 810 group->add_primitive_field(idx, type); 811 break; 812 case T_OBJECT: 813 case T_ARRAY: 814 { 815 LayoutKind lk = field_layout_selection(fieldinfo, _inline_layout_info_array, true); 816 if (fieldinfo.field_flags().is_null_free_inline_type() || lk != LayoutKind::REFERENCE 817 || (!fieldinfo.field_flags().is_injected() 818 && _inline_layout_info_array != nullptr && _inline_layout_info_array->adr_at(fieldinfo.index())->klass() != nullptr 819 && !_inline_layout_info_array->adr_at(fieldinfo.index())->klass()->is_identity_class())) { 820 _has_inline_type_fields = true; 821 _has_flattening_information = true; 822 } 823 if (lk == LayoutKind::REFERENCE) { 824 if (group != _static_fields) _nonstatic_oopmap_count++; 825 group->add_oop_field(idx); 826 } else { 827 _has_flattening_information = true; 828 InlineKlass* vk = _inline_layout_info_array->adr_at(fieldinfo.index())->klass(); 829 int size, alignment; 830 get_size_and_alignment(vk, lk, &size, &alignment); 831 group->add_flat_field(idx, vk, lk, size, alignment); 832 _inline_layout_info_array->adr_at(fieldinfo.index())->set_kind(lk); 833 _nonstatic_oopmap_count += vk->nonstatic_oop_map_count(); 834 _field_info->adr_at(idx)->field_flags_addr()->update_flat(true); 835 _field_info->adr_at(idx)->set_layout_kind(lk); 836 // no need to update _must_be_atomic if vk->must_be_atomic() is true because current class is not an inline class 837 } 838 break; 839 } 840 default: 841 fatal("Something wrong?"); 842 } 843 } 844 _root_group->sort_by_size(); 845 _static_fields->sort_by_size(); 846 if (!_contended_groups.is_empty()) { 847 for (int i = 0; i < _contended_groups.length(); i++) { 848 _contended_groups.at(i)->sort_by_size(); 849 } 850 } 851 } 852 853 /* Field sorting for inline classes: 854 * - because inline classes are immutable, the @Contended annotation is ignored 855 * when computing their layout (with only read operation, there's no false 856 * sharing issue) 857 * - this method also records the alignment of the field with the most 858 * constraining alignment, this value is then used as the alignment 859 * constraint when flattening this inline type into another container 860 * - field flattening decisions are taken in this method (those decisions are 861 * currently only based in the size of the fields to be flattened, the size 862 * of the resulting instance is not considered) 863 */ 864 void FieldLayoutBuilder::inline_class_field_sorting() { 865 assert(_is_inline_type || _is_abstract_value, "Should only be used for inline classes"); 866 int alignment = -1; 867 int idx = 0; 868 for (GrowableArrayIterator<FieldInfo> it = _field_info->begin(); it != _field_info->end(); ++it, ++idx) { 869 FieldGroup* group = nullptr; 870 FieldInfo fieldinfo = *it; 871 int field_alignment = 1; 872 if (fieldinfo.access_flags().is_static()) { 873 group = _static_fields; 874 } else { 875 _has_nonstatic_fields = true; 876 _declared_non_static_fields_count++; 877 group = _root_group; 878 } 879 assert(group != nullptr, "invariant"); 880 BasicType type = Signature::basic_type(fieldinfo.signature(_constant_pool)); 881 switch(type) { 882 case T_BYTE: 883 case T_CHAR: 884 case T_DOUBLE: 885 case T_FLOAT: 886 case T_INT: 887 case T_LONG: 888 case T_SHORT: 889 case T_BOOLEAN: 890 if (group != _static_fields) { 891 field_alignment = type2aelembytes(type); // alignment == size for primitive types 892 } 893 group->add_primitive_field(fieldinfo.index(), type); 894 break; 895 case T_OBJECT: 896 case T_ARRAY: 897 { 898 bool use_atomic_flat = _must_be_atomic; // flatten atomic fields only if the container is itself atomic 899 LayoutKind lk = field_layout_selection(fieldinfo, _inline_layout_info_array, use_atomic_flat); 900 if (fieldinfo.field_flags().is_null_free_inline_type() || lk != LayoutKind::REFERENCE 901 || (!fieldinfo.field_flags().is_injected() 902 && _inline_layout_info_array != nullptr && _inline_layout_info_array->adr_at(fieldinfo.index())->klass() != nullptr 903 && !_inline_layout_info_array->adr_at(fieldinfo.index())->klass()->is_identity_class())) { 904 _has_inline_type_fields = true; 905 _has_flattening_information = true; 906 } 907 if (lk == LayoutKind::REFERENCE) { 908 if (group != _static_fields) { 909 _nonstatic_oopmap_count++; 910 field_alignment = type2aelembytes(type); // alignment == size for oops 911 } 912 group->add_oop_field(idx); 913 } else { 914 _has_flattening_information = true; 915 InlineKlass* vk = _inline_layout_info_array->adr_at(fieldinfo.index())->klass(); 916 if (!vk->is_naturally_atomic()) _has_non_naturally_atomic_fields = true; 917 int size, alignment; 918 get_size_and_alignment(vk, lk, &size, &alignment); 919 group->add_flat_field(idx, vk, lk, size, alignment); 920 _inline_layout_info_array->adr_at(fieldinfo.index())->set_kind(lk); 921 _nonstatic_oopmap_count += vk->nonstatic_oop_map_count(); 922 field_alignment = alignment; 923 _field_info->adr_at(idx)->field_flags_addr()->update_flat(true); 924 _field_info->adr_at(idx)->set_layout_kind(lk); 925 } 926 break; 927 } 928 default: 929 fatal("Unexpected BasicType"); 930 } 931 if (!fieldinfo.access_flags().is_static() && field_alignment > alignment) alignment = field_alignment; 932 } 933 _payload_alignment = alignment; 934 assert(_has_nonstatic_fields || _is_abstract_value, "Concrete value types do not support zero instance size yet"); 935 } 936 937 void FieldLayoutBuilder::insert_contended_padding(LayoutRawBlock* slot) { 938 if (ContendedPaddingWidth > 0) { 939 LayoutRawBlock* padding = new LayoutRawBlock(LayoutRawBlock::PADDING, ContendedPaddingWidth); 940 _layout->insert(slot, padding); 941 } 942 } 943 944 /* Computation of regular classes layout is an evolution of the previous default layout 945 * (FieldAllocationStyle 1): 946 * - primitive fields (both primitive types and flat inline types) are allocated 947 * first, from the biggest to the smallest 948 * - then oop fields are allocated (to increase chances to have contiguous oops and 949 * a simpler oopmap). 950 */ 951 void FieldLayoutBuilder::compute_regular_layout() { 952 bool need_tail_padding = false; 953 prologue(); 954 regular_field_sorting(); 955 if (_is_contended) { 956 _layout->set_start(_layout->last_block()); 957 // insertion is currently easy because the current strategy doesn't try to fill holes 958 // in super classes layouts => the _start block is by consequence the _last_block 959 insert_contended_padding(_layout->start()); 960 need_tail_padding = true; 961 } 962 _layout->add(_root_group->big_primitive_fields()); 963 _layout->add(_root_group->small_primitive_fields()); 964 _layout->add(_root_group->oop_fields()); 965 966 if (!_contended_groups.is_empty()) { 967 for (int i = 0; i < _contended_groups.length(); i++) { 968 FieldGroup* cg = _contended_groups.at(i); 969 LayoutRawBlock* start = _layout->last_block(); 970 insert_contended_padding(start); 971 _layout->add(cg->big_primitive_fields()); 972 _layout->add(cg->small_primitive_fields(), start); 973 _layout->add(cg->oop_fields(), start); 974 need_tail_padding = true; 975 } 976 } 977 978 if (need_tail_padding) { 979 insert_contended_padding(_layout->last_block()); 980 } 981 982 // Warning: IntanceMirrorKlass expects static oops to be allocated first 983 _static_layout->add_contiguously(_static_fields->oop_fields()); 984 _static_layout->add(_static_fields->big_primitive_fields()); 985 _static_layout->add(_static_fields->small_primitive_fields()); 986 987 epilogue(); 988 } 989 990 /* Computation of inline classes has a slightly different strategy than for 991 * regular classes. Regular classes have their oop fields allocated at the end 992 * of the layout to increase GC performances. Unfortunately, this strategy 993 * increases the number of empty slots inside an instance. Because the purpose 994 * of inline classes is to be embedded into other containers, it is critical 995 * to keep their size as small as possible. For this reason, the allocation 996 * strategy is: 997 * - big primitive fields (primitive types and flat inline type smaller 998 * than an oop) are allocated first (from the biggest to the smallest) 999 * - then oop fields 1000 * - then small primitive fields (from the biggest to the smallest) 1001 */ 1002 void FieldLayoutBuilder::compute_inline_class_layout() { 1003 1004 // Test if the concrete inline class is an empty class (no instance fields) 1005 // and insert a dummy field if needed 1006 if (!_is_abstract_value) { 1007 bool declares_non_static_fields = false; 1008 for (GrowableArrayIterator<FieldInfo> it = _field_info->begin(); it != _field_info->end(); ++it) { 1009 FieldInfo fieldinfo = *it; 1010 if (!fieldinfo.access_flags().is_static()) { 1011 declares_non_static_fields = true; 1012 break; 1013 } 1014 } 1015 if (!declares_non_static_fields) { 1016 bool has_inherited_fields = false; 1017 const InstanceKlass* super = _super_klass; 1018 while(super != nullptr) { 1019 if (super->has_nonstatic_fields()) { 1020 has_inherited_fields = true; 1021 break; 1022 } 1023 super = super->super() == nullptr ? nullptr : InstanceKlass::cast(super->super()); 1024 } 1025 1026 if (!has_inherited_fields) { 1027 // Inject ".empty" dummy field 1028 _is_empty_inline_class = true; 1029 FieldInfo::FieldFlags fflags(0); 1030 fflags.update_injected(true); 1031 AccessFlags aflags; 1032 FieldInfo fi(aflags, 1033 (u2)vmSymbols::as_int(VM_SYMBOL_ENUM_NAME(empty_marker_name)), 1034 (u2)vmSymbols::as_int(VM_SYMBOL_ENUM_NAME(byte_signature)), 1035 0, 1036 fflags); 1037 int idx = _field_info->append(fi); 1038 _field_info->adr_at(idx)->set_index(idx); 1039 } 1040 } 1041 } 1042 1043 prologue(); 1044 inline_class_field_sorting(); 1045 1046 assert(_layout->start()->block_kind() == LayoutRawBlock::RESERVED, "Unexpected"); 1047 1048 if (_layout->super_has_fields() && !_is_abstract_value) { // non-static field layout 1049 if (!_has_nonstatic_fields) { 1050 assert(_is_abstract_value, "Concrete value types have at least one field"); 1051 // Nothing to do 1052 } else { 1053 // decide which alignment to use, then set first allowed field offset 1054 1055 assert(_layout->super_alignment() >= _payload_alignment, "Incompatible alignment"); 1056 assert(_layout->super_alignment() % _payload_alignment == 0, "Incompatible alignment"); 1057 1058 if (_payload_alignment < _layout->super_alignment()) { 1059 int new_alignment = _payload_alignment > _layout->super_min_align_required() ? _payload_alignment : _layout->super_min_align_required(); 1060 assert(new_alignment % _payload_alignment == 0, "Must be"); 1061 assert(new_alignment % _layout->super_min_align_required() == 0, "Must be"); 1062 _payload_alignment = new_alignment; 1063 } 1064 _layout->set_start(_layout->first_field_block()); 1065 } 1066 } else { 1067 if (_is_abstract_value && _has_nonstatic_fields) { 1068 _payload_alignment = type2aelembytes(BasicType::T_LONG); 1069 } 1070 assert(_layout->start()->next_block()->block_kind() == LayoutRawBlock::EMPTY || !UseCompressedClassPointers, "Unexpected"); 1071 LayoutRawBlock* first_empty = _layout->start()->next_block(); 1072 if (first_empty->offset() % _payload_alignment != 0) { 1073 LayoutRawBlock* padding = new LayoutRawBlock(LayoutRawBlock::PADDING, _payload_alignment - (first_empty->offset() % _payload_alignment)); 1074 _layout->insert(first_empty, padding); 1075 if (first_empty->size() == 0) { 1076 _layout->remove(first_empty); 1077 } 1078 _layout->set_start(padding); 1079 } 1080 } 1081 1082 _layout->add(_root_group->big_primitive_fields()); 1083 _layout->add(_root_group->oop_fields()); 1084 _layout->add(_root_group->small_primitive_fields()); 1085 1086 LayoutRawBlock* first_field = _layout->first_field_block(); 1087 if (first_field != nullptr) { 1088 _first_field_offset = _layout->first_field_block()->offset(); 1089 _payload_size_in_bytes = _layout->last_block()->offset() - _layout->first_field_block()->offset(); 1090 } else { 1091 assert(_is_abstract_value, "Concrete inline types must have at least one field"); 1092 _first_field_offset = _layout->blocks()->size(); 1093 _payload_size_in_bytes = 0; 1094 } 1095 1096 // Determining if the value class is naturally atomic: 1097 if ((!_layout->super_has_fields() && _declared_non_static_fields_count <= 1 && !_has_non_naturally_atomic_fields) 1098 || (_layout->super_has_fields() && _super_klass->is_naturally_atomic() && _declared_non_static_fields_count == 0)) { 1099 _is_naturally_atomic = true; 1100 } 1101 1102 // At this point, the characteristics of the raw layout (used in standalone instances) are known. 1103 // From this, additional layouts will be computed: atomic and nullable layouts 1104 // Once those additional layouts are computed, the raw layout might need some adjustments 1105 1106 if (!_is_abstract_value) { // Flat layouts are only for concrete value classes 1107 // Validation of the non atomic layout 1108 if ((InlineFieldMaxFlatSize < 0 || _payload_size_in_bytes * BitsPerByte <= InlineFieldMaxFlatSize) 1109 && (!_must_be_atomic || _is_naturally_atomic)) { 1110 _non_atomic_layout_size_in_bytes = _payload_size_in_bytes; 1111 _non_atomic_layout_alignment = _payload_alignment; 1112 } 1113 1114 // Next step is to compute the characteristics for a layout enabling atomic updates 1115 if (AtomicFieldFlattening) { 1116 int atomic_size = _payload_size_in_bytes == 0 ? 0 : round_up_power_of_2(_payload_size_in_bytes); 1117 if ( atomic_size <= (int)MAX_ATOMIC_OP_SIZE 1118 && (InlineFieldMaxFlatSize < 0 || atomic_size * BitsPerByte <= InlineFieldMaxFlatSize)) { 1119 _atomic_layout_size_in_bytes = atomic_size; 1120 } 1121 } 1122 1123 // Next step is the nullable layout: the layout must include a null marker and must also be atomic 1124 if (NullableFieldFlattening) { 1125 // Looking if there's an empty slot inside the layout that could be used to store a null marker 1126 // FIXME: could it be possible to re-use the .empty field as a null marker for empty values? 1127 LayoutRawBlock* b = _layout->first_field_block(); 1128 assert(b != nullptr, "A concrete value class must have at least one (possible dummy) field"); 1129 int null_marker_offset = -1; 1130 if (_is_empty_inline_class) { 1131 // Reusing the dummy field as a field marker 1132 assert(_field_info->adr_at(b->field_index())->name(_constant_pool) == vmSymbols::empty_marker_name(), "b must be the dummy field"); 1133 null_marker_offset = b->offset(); 1134 } else { 1135 while (b != _layout->last_block()) { 1136 if (b->block_kind() == LayoutRawBlock::EMPTY) { 1137 break; 1138 } 1139 b = b->next_block(); 1140 } 1141 if (b != _layout->last_block()) { 1142 // found an empty slot, register its offset from the beginning of the payload 1143 null_marker_offset = b->offset(); 1144 LayoutRawBlock* marker = new LayoutRawBlock(LayoutRawBlock::NULL_MARKER, 1); 1145 _layout->add_field_at_offset(marker, b->offset()); 1146 } 1147 if (null_marker_offset == -1) { // no empty slot available to store the null marker, need to inject one 1148 int last_offset = _layout->last_block()->offset(); 1149 LayoutRawBlock* marker = new LayoutRawBlock(LayoutRawBlock::NULL_MARKER, 1); 1150 _layout->insert_field_block(_layout->last_block(), marker); 1151 assert(marker->offset() == last_offset, "Null marker should have been inserted at the end"); 1152 null_marker_offset = marker->offset(); 1153 } 1154 } 1155 1156 // Now that the null marker is there, the size of the nullable layout must computed (remember, must be atomic too) 1157 int new_raw_size = _layout->last_block()->offset() - _layout->first_field_block()->offset(); 1158 int nullable_size = round_up_power_of_2(new_raw_size); 1159 if (nullable_size <= (int)MAX_ATOMIC_OP_SIZE 1160 && (InlineFieldMaxFlatSize < 0 || nullable_size * BitsPerByte <= InlineFieldMaxFlatSize)) { 1161 _nullable_layout_size_in_bytes = nullable_size; 1162 _null_marker_offset = null_marker_offset; 1163 } else { 1164 // If the nullable layout is rejected, the NULL_MARKER block should be removed 1165 // from the layout, otherwise it will appear anyway if the layout is printer 1166 _layout->remove_null_marker(); 1167 _null_marker_offset = -1; 1168 } 1169 } 1170 // If the inline class has an atomic or nullable (which is also atomic) layout, 1171 // we want the raw layout to have the same alignment as those atomic layouts so access codes 1172 // could remain simple (single instruction without intermediate copy). This might required 1173 // to shift all fields in the raw layout, but this operation is possible only if the class 1174 // doesn't have inherited fields (offsets of inherited fields cannot be changed). If a 1175 // field shift is needed but not possible, all atomic layouts are disabled and only reference 1176 // and loosely consistent are supported. 1177 int required_alignment = _payload_alignment; 1178 if (has_atomic_layout() && _payload_alignment < atomic_layout_size_in_bytes()) { 1179 required_alignment = atomic_layout_size_in_bytes(); 1180 } 1181 if (has_nullable_layout() && _payload_alignment < nullable_layout_size_in_bytes()) { 1182 required_alignment = nullable_layout_size_in_bytes(); 1183 } 1184 int shift = first_field->offset() % required_alignment; 1185 if (shift != 0) { 1186 if (required_alignment > _payload_alignment && !_layout->has_inherited_fields()) { 1187 assert(_layout->first_field_block() != nullptr, "A concrete value class must have at least one (possible dummy) field"); 1188 _layout->shift_fields(shift); 1189 _first_field_offset = _layout->first_field_block()->offset(); 1190 if (has_nullable_layout()) { 1191 assert(!_is_empty_inline_class, "Should not get here with empty values"); 1192 _null_marker_offset = _layout->find_null_marker()->offset(); 1193 } 1194 _payload_alignment = required_alignment; 1195 } else { 1196 _atomic_layout_size_in_bytes = -1; 1197 if (has_nullable_layout() && !_is_empty_inline_class) { // empty values don't have a dedicated NULL_MARKER block 1198 _layout->remove_null_marker(); 1199 } 1200 _nullable_layout_size_in_bytes = -1; 1201 _null_marker_offset = -1; 1202 } 1203 } else { 1204 _payload_alignment = required_alignment; 1205 } 1206 1207 // If the inline class has a nullable layout, the layout used in heap allocated standalone 1208 // instances must also be the nullable layout, in order to be able to set the null marker to 1209 // non-null before copying the payload to other containers. 1210 if (has_nullable_layout() && payload_layout_size_in_bytes() < nullable_layout_size_in_bytes()) { 1211 _payload_size_in_bytes = nullable_layout_size_in_bytes(); 1212 } 1213 } 1214 // Warning:: InstanceMirrorKlass expects static oops to be allocated first 1215 _static_layout->add_contiguously(_static_fields->oop_fields()); 1216 _static_layout->add(_static_fields->big_primitive_fields()); 1217 _static_layout->add(_static_fields->small_primitive_fields()); 1218 1219 epilogue(); 1220 } 1221 1222 void FieldLayoutBuilder::add_flat_field_oopmap(OopMapBlocksBuilder* nonstatic_oop_maps, 1223 InlineKlass* vklass, int offset) { 1224 int diff = offset - vklass->first_field_offset(); 1225 const OopMapBlock* map = vklass->start_of_nonstatic_oop_maps(); 1226 const OopMapBlock* last_map = map + vklass->nonstatic_oop_map_count(); 1227 while (map < last_map) { 1228 nonstatic_oop_maps->add(map->offset() + diff, map->count()); 1229 map++; 1230 } 1231 } 1232 1233 void FieldLayoutBuilder::register_embedded_oops_from_list(OopMapBlocksBuilder* nonstatic_oop_maps, GrowableArray<LayoutRawBlock*>* list) { 1234 if (list == nullptr) return; 1235 for (int i = 0; i < list->length(); i++) { 1236 LayoutRawBlock* f = list->at(i); 1237 if (f->block_kind() == LayoutRawBlock::FLAT) { 1238 InlineKlass* vk = f->inline_klass(); 1239 assert(vk != nullptr, "Should have been initialized"); 1240 if (vk->contains_oops()) { 1241 add_flat_field_oopmap(nonstatic_oop_maps, vk, f->offset()); 1242 } 1243 } 1244 } 1245 } 1246 1247 void FieldLayoutBuilder::register_embedded_oops(OopMapBlocksBuilder* nonstatic_oop_maps, FieldGroup* group) { 1248 if (group->oop_fields() != nullptr) { 1249 for (int i = 0; i < group->oop_fields()->length(); i++) { 1250 LayoutRawBlock* b = group->oop_fields()->at(i); 1251 nonstatic_oop_maps->add(b->offset(), 1); 1252 } 1253 } 1254 register_embedded_oops_from_list(nonstatic_oop_maps, group->big_primitive_fields()); 1255 register_embedded_oops_from_list(nonstatic_oop_maps, group->small_primitive_fields()); 1256 } 1257 1258 void FieldLayoutBuilder::epilogue() { 1259 // Computing oopmaps 1260 OopMapBlocksBuilder* nonstatic_oop_maps = 1261 new OopMapBlocksBuilder(_nonstatic_oopmap_count); 1262 int super_oop_map_count = (_super_klass == nullptr) ? 0 :_super_klass->nonstatic_oop_map_count(); 1263 if (super_oop_map_count > 0) { 1264 nonstatic_oop_maps->initialize_inherited_blocks(_super_klass->start_of_nonstatic_oop_maps(), 1265 _super_klass->nonstatic_oop_map_count()); 1266 } 1267 register_embedded_oops(nonstatic_oop_maps, _root_group); 1268 if (!_contended_groups.is_empty()) { 1269 for (int i = 0; i < _contended_groups.length(); i++) { 1270 FieldGroup* cg = _contended_groups.at(i); 1271 if (cg->oop_count() > 0) { 1272 assert(cg->oop_fields() != nullptr && cg->oop_fields()->at(0) != nullptr, "oop_count > 0 but no oop fields found"); 1273 register_embedded_oops(nonstatic_oop_maps, cg); 1274 } 1275 } 1276 } 1277 nonstatic_oop_maps->compact(); 1278 1279 int instance_end = align_up(_layout->last_block()->offset(), wordSize); 1280 int static_fields_end = align_up(_static_layout->last_block()->offset(), wordSize); 1281 int static_fields_size = (static_fields_end - 1282 InstanceMirrorKlass::offset_of_static_fields()) / wordSize; 1283 int nonstatic_field_end = align_up(_layout->last_block()->offset(), heapOopSize); 1284 1285 // Pass back information needed for InstanceKlass creation 1286 1287 _info->oop_map_blocks = nonstatic_oop_maps; 1288 _info->_instance_size = align_object_size(instance_end / wordSize); 1289 _info->_static_field_size = static_fields_size; 1290 _info->_nonstatic_field_size = (nonstatic_field_end - instanceOopDesc::base_offset_in_bytes()) / heapOopSize; 1291 _info->_has_nonstatic_fields = _has_nonstatic_fields; 1292 _info->_has_inline_fields = _has_inline_type_fields; 1293 _info->_is_naturally_atomic = _is_naturally_atomic; 1294 if (_is_inline_type) { 1295 _info->_must_be_atomic = _must_be_atomic; 1296 _info->_payload_alignment = _payload_alignment; 1297 _info->_first_field_offset = _first_field_offset; 1298 _info->_payload_size_in_bytes = _payload_size_in_bytes; 1299 _info->_non_atomic_size_in_bytes = _non_atomic_layout_size_in_bytes; 1300 _info->_non_atomic_alignment = _non_atomic_layout_alignment; 1301 _info->_atomic_layout_size_in_bytes = _atomic_layout_size_in_bytes; 1302 _info->_nullable_layout_size_in_bytes = _nullable_layout_size_in_bytes; 1303 _info->_null_marker_offset = _null_marker_offset; 1304 _info->_default_value_offset = _static_layout->default_value_offset(); 1305 _info->_null_reset_value_offset = _static_layout->null_reset_value_offset(); 1306 _info->_is_empty_inline_klass = _is_empty_inline_class; 1307 } 1308 1309 // This may be too restrictive, since if all the fields fit in 64 1310 // bits we could make the decision to align instances of this class 1311 // to 64-bit boundaries, and load and store them as single words. 1312 // And on machines which supported larger atomics we could similarly 1313 // allow larger values to be atomic, if properly aligned. 1314 1315 #ifdef ASSERT 1316 // Tests verifying integrity of field layouts are using the output of -XX:+PrintFieldLayout 1317 // which prints the details of LayoutRawBlocks used to compute the layout. 1318 // The code below checks that offsets in the _field_info meta-data match offsets 1319 // in the LayoutRawBlocks 1320 LayoutRawBlock* b = _layout->blocks(); 1321 while(b != _layout->last_block()) { 1322 if (b->block_kind() == LayoutRawBlock::REGULAR || b->block_kind() == LayoutRawBlock::FLAT) { 1323 if (_field_info->adr_at(b->field_index())->offset() != (u4)b->offset()) { 1324 tty->print_cr("Offset from field info = %d, offset from block = %d", (int)_field_info->adr_at(b->field_index())->offset(), b->offset()); 1325 } 1326 assert(_field_info->adr_at(b->field_index())->offset() == (u4)b->offset()," Must match"); 1327 } 1328 b = b->next_block(); 1329 } 1330 b = _static_layout->blocks(); 1331 while(b != _static_layout->last_block()) { 1332 if (b->block_kind() == LayoutRawBlock::REGULAR || b->block_kind() == LayoutRawBlock::FLAT) { 1333 assert(_field_info->adr_at(b->field_index())->offset() == (u4)b->offset()," Must match"); 1334 } 1335 b = b->next_block(); 1336 } 1337 #endif // ASSERT 1338 1339 static bool first_layout_print = true; 1340 1341 1342 if (PrintFieldLayout || (PrintInlineLayout && _has_flattening_information)) { 1343 ResourceMark rm; 1344 stringStream st; 1345 if (first_layout_print) { 1346 st.print_cr("Field layout log format: @offset size/alignment [name] [signature] [comment]"); 1347 st.print_cr("Heap oop size = %d", heapOopSize); 1348 first_layout_print = false; 1349 } 1350 if (_super_klass != nullptr) { 1351 st.print_cr("Layout of class %s@%p extends %s@%p", _classname->as_C_string(), 1352 _loader_data, _super_klass->name()->as_C_string(), _super_klass->class_loader_data()); 1353 } else { 1354 st.print_cr("Layout of class %s@%p", _classname->as_C_string(), _loader_data); 1355 } 1356 st.print_cr("Instance fields:"); 1357 _layout->print(&st, false, _super_klass, _inline_layout_info_array); 1358 st.print_cr("Static fields:"); 1359 _static_layout->print(&st, true, nullptr, _inline_layout_info_array); 1360 st.print_cr("Instance size = %d bytes", _info->_instance_size * wordSize); 1361 if (_is_inline_type) { 1362 st.print_cr("First field offset = %d", _first_field_offset); 1363 st.print_cr("Payload layout: %d/%d", _payload_size_in_bytes, _payload_alignment); 1364 if (has_non_atomic_flat_layout()) { 1365 st.print_cr("Non atomic flat layout: %d/%d", _non_atomic_layout_size_in_bytes, _non_atomic_layout_alignment); 1366 } else { 1367 st.print_cr("Non atomic flat layout: -/-"); 1368 } 1369 if (has_atomic_layout()) { 1370 st.print_cr("Atomic flat layout: %d/%d", _atomic_layout_size_in_bytes, _atomic_layout_size_in_bytes); 1371 } else { 1372 st.print_cr("Atomic flat layout: -/-"); 1373 } 1374 if (has_nullable_layout()) { 1375 st.print_cr("Nullable flat layout: %d/%d", _nullable_layout_size_in_bytes, _nullable_layout_size_in_bytes); 1376 } else { 1377 st.print_cr("Nullable flat layout: -/-"); 1378 } 1379 if (_null_marker_offset != -1) { 1380 st.print_cr("Null marker offset = %d", _null_marker_offset); 1381 } 1382 } 1383 st.print_cr("---"); 1384 // Print output all together. 1385 tty->print_raw(st.as_string()); 1386 } 1387 } 1388 1389 void FieldLayoutBuilder::build_layout() { 1390 if (_is_inline_type || _is_abstract_value) { 1391 compute_inline_class_layout(); 1392 } else { 1393 compute_regular_layout(); 1394 } 1395 }