1 /*
   2  * Copyright (c) 2018, 2025, 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 "cds/aotMetaspace.hpp"
  26 #include "cds/aotStreamedHeapLoader.hpp"
  27 #include "cds/aotThread.hpp"
  28 #include "cds/cdsConfig.hpp"
  29 #include "cds/filemap.hpp"
  30 #include "cds/heapShared.inline.hpp"
  31 #include "classfile/classLoaderDataShared.hpp"
  32 #include "classfile/javaClasses.inline.hpp"
  33 #include "classfile/stringTable.hpp"
  34 #include "classfile/vmClasses.hpp"
  35 #include "gc/shared/collectedHeap.inline.hpp"
  36 #include "gc/shared/oopStorage.inline.hpp"
  37 #include "gc/shared/oopStorageSet.inline.hpp"
  38 #include "logging/log.hpp"
  39 #include "memory/iterator.inline.hpp"
  40 #include "memory/oopFactory.hpp"
  41 #include "oops/access.inline.hpp"
  42 #include "oops/objArrayOop.inline.hpp"
  43 #include "oops/oop.inline.hpp"
  44 #include "runtime/globals.hpp"
  45 #include "runtime/globals_extension.hpp"
  46 #include "runtime/handles.inline.hpp"
  47 #include "runtime/java.hpp"
  48 #include "runtime/mutex.hpp"
  49 #include "runtime/thread.hpp"
  50 #include "utilities/bitMap.inline.hpp"
  51 #include "utilities/exceptions.hpp"
  52 #include "utilities/globalDefinitions.hpp"
  53 #include "utilities/stack.inline.hpp"
  54 #include "utilities/ticks.hpp"
  55 
  56 #include <type_traits>
  57 
  58 #if INCLUDE_CDS_JAVA_HEAP
  59 
  60 FileMapRegion* AOTStreamedHeapLoader::_heap_region;
  61 FileMapRegion* AOTStreamedHeapLoader::_bitmap_region;
  62 int* AOTStreamedHeapLoader::_roots_archive;
  63 OopHandle AOTStreamedHeapLoader::_roots;
  64 BitMapView AOTStreamedHeapLoader::_oopmap;
  65 bool AOTStreamedHeapLoader::_is_in_use;
  66 int AOTStreamedHeapLoader::_previous_batch_last_object_index;
  67 int AOTStreamedHeapLoader::_current_batch_last_object_index;
  68 int AOTStreamedHeapLoader::_current_root_index;
  69 size_t AOTStreamedHeapLoader::_allocated_words;
  70 bool AOTStreamedHeapLoader::_allow_gc;
  71 bool AOTStreamedHeapLoader::_objects_are_handles;
  72 size_t AOTStreamedHeapLoader::_num_archived_objects;
  73 int AOTStreamedHeapLoader::_num_roots;
  74 size_t AOTStreamedHeapLoader::_heap_region_used;
  75 bool AOTStreamedHeapLoader::_loading_all_objects;
  76 
  77 size_t* AOTStreamedHeapLoader::_object_index_to_buffer_offset_table;
  78 void** AOTStreamedHeapLoader::_object_index_to_heap_object_table;
  79 int* AOTStreamedHeapLoader::_root_highest_object_index_table;
  80 
  81 bool AOTStreamedHeapLoader::_waiting_for_iterator;
  82 bool AOTStreamedHeapLoader::_swapping_root_format;
  83 
  84 static uint64_t _early_materialization_time_ns = 0;
  85 static uint64_t _late_materialization_time_ns = 0;
  86 static uint64_t _final_materialization_time_ns = 0;
  87 static uint64_t _cleanup_materialization_time_ns = 0;
  88 static volatile uint64_t _accumulated_lazy_materialization_time_ns = 0;
  89 static Ticks _materialization_start_ticks;
  90 
  91 int AOTStreamedHeapLoader::object_index_for_root_index(int root_index) {
  92   return _roots_archive[root_index];
  93 }
  94 
  95 int AOTStreamedHeapLoader::highest_object_index_for_root_index(int root_index) {
  96   return _root_highest_object_index_table[root_index];
  97 }
  98 
  99 size_t AOTStreamedHeapLoader::buffer_offset_for_object_index(int object_index) {
 100   return _object_index_to_buffer_offset_table[object_index];
 101 }
 102 
 103 oopDesc* AOTStreamedHeapLoader::archive_object_for_object_index(int object_index) {
 104   size_t buffer_offset = buffer_offset_for_object_index(object_index);
 105   address bottom = (address)_heap_region->mapped_base();
 106   return (oopDesc*)(bottom + buffer_offset);
 107 }
 108 
 109 size_t AOTStreamedHeapLoader::buffer_offset_for_archive_object(oopDesc* archive_object) {
 110   address bottom = (address)_heap_region->mapped_base();
 111   return size_t(archive_object) - size_t(bottom);
 112 }
 113 
 114 template <bool use_coops>
 115 BitMap::idx_t AOTStreamedHeapLoader::obj_bit_idx_for_buffer_offset(size_t buffer_offset) {
 116   if constexpr (use_coops) {
 117     return BitMap::idx_t(buffer_offset / sizeof(narrowOop));
 118   } else {
 119     return BitMap::idx_t(buffer_offset / sizeof(HeapWord));
 120   }
 121 }
 122 
 123 oop AOTStreamedHeapLoader::heap_object_for_object_index(int object_index) {
 124   assert(object_index >= 0 && object_index <= (int)_num_archived_objects,
 125          "Heap object reference out of index: %d", object_index);
 126 
 127   if (_objects_are_handles) {
 128     oop* handle = (oop*)_object_index_to_heap_object_table[object_index];
 129     if (handle == nullptr) {
 130       return nullptr;
 131     }
 132     return NativeAccess<>::oop_load(handle);
 133   } else {
 134     return cast_to_oop(_object_index_to_heap_object_table[object_index]);
 135   }
 136 }
 137 
 138 void AOTStreamedHeapLoader::set_heap_object_for_object_index(int object_index, oop heap_object) {
 139   assert(heap_object_for_object_index(object_index) == nullptr, "Should only set once with this API");
 140   if (_objects_are_handles) {
 141     oop* handle = Universe::vm_global()->allocate();
 142     NativeAccess<>::oop_store(handle, heap_object);
 143     _object_index_to_heap_object_table[object_index] = (void*)handle;
 144   } else {
 145     _object_index_to_heap_object_table[object_index] = cast_from_oop<void*>(heap_object);
 146   }
 147 }
 148 
 149 int AOTStreamedHeapLoader::archived_string_value_object_index(oopDesc* archive_object) {
 150     assert(archive_object->klass() == vmClasses::String_klass(), "Must be an archived string");
 151     address archive_string_value_addr = (address)archive_object + java_lang_String::value_offset();
 152     return UseCompressedOops ? *(int*)archive_string_value_addr : (int)*(int64_t*)archive_string_value_addr;
 153 }
 154 
 155 static int archive_array_length(oopDesc* archive_array) {
 156   return *(int*)(address(archive_array) + arrayOopDesc::length_offset_in_bytes());
 157 }
 158 
 159 static size_t archive_object_size(oopDesc* archive_object) {
 160   Klass* klass = archive_object->klass();
 161   int lh = klass->layout_helper();
 162 
 163   if (Klass::layout_helper_is_instance(lh)) {
 164     // Instance
 165     if (Klass::layout_helper_needs_slow_path(lh)) {
 166       return ((size_t*)(archive_object))[-1];
 167     } else {
 168       return (size_t)Klass::layout_helper_size_in_bytes(lh) >> LogHeapWordSize;
 169     }
 170   } else if (Klass::layout_helper_is_array(lh)) {
 171     // Array
 172     size_t size_in_bytes;
 173     size_t array_length = (size_t)archive_array_length(archive_object);
 174     size_in_bytes = array_length << Klass::layout_helper_log2_element_size(lh);
 175     size_in_bytes += (size_t)Klass::layout_helper_header_size(lh);
 176 
 177     return align_up(size_in_bytes, (size_t)MinObjAlignmentInBytes) / HeapWordSize;
 178   } else {
 179     // Other
 180     return ((size_t*)(archive_object))[-1];
 181   }
 182 }
 183 
 184 oop AOTStreamedHeapLoader::allocate_object(oopDesc* archive_object, markWord mark, size_t size, TRAPS) {
 185   assert(!archive_object->is_stackChunk(), "no such objects are archived");
 186 
 187   oop heap_object;
 188 
 189   Klass* klass = archive_object->klass();
 190   if (klass->is_mirror_instance_klass()) {
 191     heap_object = Universe::heap()->class_allocate(klass, size, CHECK_NULL);
 192   } else if (klass->is_instance_klass()) {
 193     heap_object = Universe::heap()->obj_allocate(klass, size, CHECK_NULL);
 194   } else {
 195     assert(klass->is_array_klass(), "must be");
 196     int length = archive_array_length(archive_object);
 197     bool do_zero = klass->is_objArray_klass();
 198     heap_object = Universe::heap()->array_allocate(klass, size, length, do_zero, CHECK_NULL);
 199   }
 200 
 201   heap_object->set_mark(mark);
 202 
 203   return heap_object;
 204 }
 205 
 206 void AOTStreamedHeapLoader::install_root(int root_index, oop heap_object) {
 207   objArrayOop roots = objArrayOop(_roots.resolve());
 208   OrderAccess::release(); // Once the store below publishes an object, it can be concurrently picked up by another thread without using the lock
 209   roots->obj_at_put(root_index, heap_object);
 210 }
 211 
 212 void AOTStreamedHeapLoader::TracingObjectLoader::wait_for_iterator() {
 213   if (JavaThread::current()->is_active_Java_thread()) {
 214     // When the main thread has bootstrapped past the point of allowing safepoints,
 215     // we can and indeed have to use safepoint checking waiting.
 216     AOTHeapLoading_lock->wait();
 217   } else {
 218     // If we have no bootstrapped the main thread far enough, then we cannot and
 219     // indeed also don't need to perform safepoint checking waiting.
 220     AOTHeapLoading_lock->wait_without_safepoint_check();
 221   }
 222 }
 223 
 224 // Link object after copying in-place
 225 template <typename LinkerT>
 226 class AOTStreamedHeapLoader::InPlaceLinkingOopClosure : public BasicOopIterateClosure {
 227 private:
 228   oop _obj;
 229   LinkerT _linker;
 230 
 231 public:
 232   InPlaceLinkingOopClosure(oop obj, LinkerT linker)
 233     : _obj(obj),
 234       _linker(linker) {
 235   }
 236 
 237   virtual void do_oop(oop* p) { do_oop_work(p, (int)*(intptr_t*)p); }
 238   virtual void do_oop(narrowOop* p) { do_oop_work(p, *(int*)p); }
 239 
 240   template <typename T>
 241   void do_oop_work(T* p, int object_index) {
 242     int p_offset = pointer_delta_as_int((address)p, cast_from_oop<address>(_obj));
 243     oop pointee = _linker(p_offset, object_index);
 244     if (pointee != nullptr) {
 245       _obj->obj_field_put_access<IS_DEST_UNINITIALIZED>((int)p_offset, pointee);
 246     }
 247   }
 248 };
 249 
 250 template <bool use_coops, typename LinkerT>
 251 void AOTStreamedHeapLoader::copy_payload_carefully(oopDesc* archive_object,
 252                                                    oop heap_object,
 253                                                    BitMap::idx_t header_bit,
 254                                                    BitMap::idx_t start_bit,
 255                                                    BitMap::idx_t end_bit,
 256                                                    LinkerT linker) {
 257   using RawElementT = std::conditional_t<use_coops, int32_t, int64_t>;
 258   using OopElementT = std::conditional_t<use_coops, narrowOop, oop>;
 259 
 260   BitMap::idx_t unfinished_bit = start_bit;
 261   BitMap::idx_t next_reference_bit = _oopmap.find_first_set_bit(unfinished_bit, end_bit);
 262 
 263   // Fill in heap object bytes
 264   while (unfinished_bit < end_bit) {
 265     assert(unfinished_bit >= start_bit && unfinished_bit < end_bit, "out of bounds copying");
 266 
 267     // This is the address of the pointee inside the input stream
 268     size_t payload_offset = unfinished_bit - header_bit;
 269     RawElementT* archive_payload_addr = ((RawElementT*)archive_object) + payload_offset;
 270     RawElementT* heap_payload_addr = cast_from_oop<RawElementT*>(heap_object) + payload_offset;
 271 
 272     assert(heap_payload_addr >= cast_from_oop<RawElementT*>(heap_object) &&
 273            (HeapWord*)heap_payload_addr < cast_from_oop<HeapWord*>(heap_object) + heap_object->size(),
 274            "Out of bounds copying");
 275 
 276     if (next_reference_bit > unfinished_bit) {
 277       // Primitive bytes available
 278       size_t primitive_elements = next_reference_bit - unfinished_bit;
 279       size_t primitive_bytes = primitive_elements * sizeof(RawElementT);
 280       ::memcpy(heap_payload_addr, archive_payload_addr, primitive_bytes);
 281 
 282       unfinished_bit = next_reference_bit;
 283     } else {
 284       // Encountered reference
 285       RawElementT* archive_p = (RawElementT*)archive_payload_addr;
 286       OopElementT* heap_p = (OopElementT*)heap_payload_addr;
 287       int pointee_object_index = (int)*archive_p;
 288       int heap_p_offset = pointer_delta_as_int((address)heap_p, cast_from_oop<address>(heap_object));
 289 
 290       // The object index is retrieved from the archive, not the heap object. This is
 291       // important after GC is enabled. Concurrent GC threads may scan references in the
 292       // heap for various reasons after this point. Therefore, it is not okay to first copy
 293       // the object index from a reference location in the archived object payload to a
 294       // corresponding location in the heap object payload, and then fix it up afterwards to
 295       // refer to a heap object. This is why this code iterates carefully over object references
 296       // in the archived object, linking them one by one, without clobbering the reference
 297       // locations in the heap objects with anything other than transitions from null to the
 298       // intended linked object.
 299       oop obj = linker(heap_p_offset, pointee_object_index);
 300       if (obj != nullptr) {
 301         heap_object->obj_field_put(heap_p_offset, obj);
 302       }
 303 
 304       unfinished_bit++;
 305       next_reference_bit = _oopmap.find_first_set_bit(unfinished_bit, end_bit);
 306     }
 307   }
 308 }
 309 
 310 template <bool use_coops, typename LinkerT>
 311 void AOTStreamedHeapLoader::copy_object_impl(oopDesc* archive_object,
 312                                              oop heap_object,
 313                                              size_t size,
 314                                              LinkerT linker) {
 315   if (!_allow_gc) {
 316     // Without concurrent GC running, we can copy incorrect object references
 317     // and metadata references into the heap object and then fix them up in-place.
 318     size_t payload_size = size - 1;
 319     HeapWord* archive_start = ((HeapWord*)archive_object) + 1;
 320     HeapWord* heap_start = cast_from_oop<HeapWord*>(heap_object) + 1;
 321 
 322     Copy::disjoint_words(archive_start, heap_start, payload_size);
 323 
 324     // In-place linking fixes up object indices from references of the heap object,
 325     // and patches them up to refer to objects. This can be done because we just copied
 326     // the payload of the object from the archive to the heap object, including the
 327     // reference object indices. However, this is only okay to do before the GC can run.
 328     // A concurrent GC thread might racingly read the object payload after GC is enabled.
 329     InPlaceLinkingOopClosure cl(heap_object, linker);
 330     heap_object->oop_iterate(&cl);
 331     HeapShared::remap_loaded_metadata(heap_object);
 332     return;
 333   }
 334 
 335   // When a concurrent GC may be running, we take care not to copy incorrect oops,
 336   // narrowOops or Metadata* into the heap objects. Transitions go from 0 to the
 337   // intended runtime linked values only.
 338   size_t word_scale = use_coops ? 2 : 1;
 339   using RawElementT = std::conditional_t<use_coops, int32_t, int64_t>;
 340 
 341   // Skip the markWord; it is set at allocation time
 342   size_t header_size = word_scale;
 343 
 344   size_t buffer_offset = buffer_offset_for_archive_object(archive_object);
 345   const BitMap::idx_t header_bit = obj_bit_idx_for_buffer_offset<use_coops>(buffer_offset);
 346   const BitMap::idx_t start_bit = header_bit + header_size;
 347   const BitMap::idx_t end_bit = header_bit + size * word_scale;
 348 
 349   BitMap::idx_t curr_bit = start_bit;
 350 
 351   // We are a bit paranoid about GC or other safepointing operations observing
 352   // shady metadata fields from the archive that do not point at real metadata.
 353   // We deal with this by explicitly reading the requested address from the
 354   // archive and fixing it to real Metadata before writing it into the heap object.
 355   HeapShared::do_metadata_offsets(heap_object, [&](int metadata_offset) {
 356     BitMap::idx_t metadata_field_idx = header_bit + (size_t)metadata_offset / sizeof(RawElementT);
 357     BitMap::idx_t skip = word_scale;
 358     assert(metadata_field_idx >= start_bit && metadata_field_idx + skip <= end_bit,
 359            "Metadata field out of bounds");
 360 
 361     // Copy payload before metadata field
 362     copy_payload_carefully<use_coops>(archive_object,
 363                                       heap_object,
 364                                       header_bit,
 365                                       curr_bit,
 366                                       metadata_field_idx,
 367                                       linker);
 368 
 369     // Copy metadata field
 370     Metadata* const archive_metadata = *(Metadata**)(uintptr_t(archive_object) + (size_t)metadata_offset);
 371     Metadata* const runtime_metadata = archive_metadata != nullptr
 372         ? (Metadata*)(address(archive_metadata) + AOTMetaspace::relocation_delta())
 373         : nullptr;
 374     assert(runtime_metadata == nullptr || AOTMetaspace::in_aot_cache(runtime_metadata), "Invalid metadata pointer");
 375     DEBUG_ONLY(Metadata* const previous_metadata = heap_object->metadata_field(metadata_offset);)
 376     assert(previous_metadata == nullptr || previous_metadata == runtime_metadata, "Should not observe transient values");
 377     heap_object->metadata_field_put(metadata_offset, runtime_metadata);
 378     curr_bit = metadata_field_idx + skip;
 379   });
 380 
 381   // Copy trailing metadata after the last metadata word. This is usually doing
 382   // all the copying.
 383   copy_payload_carefully<use_coops>(archive_object,
 384                                     heap_object,
 385                                     header_bit,
 386                                     curr_bit,
 387                                     end_bit,
 388                                     linker);
 389 }
 390 
 391 void AOTStreamedHeapLoader::copy_object_eager_linking(oopDesc* archive_object, oop heap_object, size_t size) {
 392   auto linker = [&](int p_offset, int pointee_object_index) {
 393     oop obj = AOTStreamedHeapLoader::heap_object_for_object_index(pointee_object_index);
 394     assert(pointee_object_index == 0 || obj != nullptr, "Eager object loading should only encounter already allocated links");
 395     return obj;
 396   };
 397   if (UseCompressedOops) {
 398     copy_object_impl<true>(archive_object, heap_object, size, linker);
 399   } else {
 400     copy_object_impl<false>(archive_object, heap_object, size, linker);
 401   }
 402 }
 403 
 404 void AOTStreamedHeapLoader::TracingObjectLoader::copy_object_lazy_linking(int object_index,
 405                                                                           oopDesc* archive_object,
 406                                                                           oop heap_object,
 407                                                                           size_t size,
 408                                                                           Stack<AOTHeapTraversalEntry, mtClassShared>& dfs_stack) {
 409   auto linker = [&](int p_offset, int pointee_object_index) {
 410     dfs_stack.push({pointee_object_index, object_index, p_offset});
 411 
 412     // The tracing linker is a bit lazy and mutates the reference fields in its traversal.
 413     // Returning null means don't link now.
 414     return oop(nullptr);
 415   };
 416   if (UseCompressedOops) {
 417     copy_object_impl<true>(archive_object, heap_object, size, linker);
 418   } else {
 419     copy_object_impl<false>(archive_object, heap_object, size, linker);
 420   }
 421 }
 422 
 423 oop AOTStreamedHeapLoader::TracingObjectLoader::materialize_object_inner(int object_index, Stack<AOTHeapTraversalEntry, mtClassShared>& dfs_stack, TRAPS) {
 424   // Allocate object
 425   oopDesc* archive_object = archive_object_for_object_index(object_index);
 426   size_t size = archive_object_size(archive_object);
 427   markWord mark = archive_object->mark();
 428 
 429   // The markWord is marked if the object is a String and it should be interned,
 430   // make sure to unmark it before allocating memory for the object.
 431   bool string_intern = mark.is_marked();
 432   mark = mark.set_unmarked();
 433 
 434   oop heap_object;
 435 
 436   if (string_intern) {
 437     int value_object_index = archived_string_value_object_index(archive_object);
 438 
 439     // Materialize the value object.
 440     (void)materialize_object(value_object_index, dfs_stack, CHECK_NULL);
 441 
 442     // Allocate and link the string.
 443     heap_object = allocate_object(archive_object, mark, size, CHECK_NULL);
 444     copy_object_eager_linking(archive_object, heap_object, size);
 445 
 446     assert(java_lang_String::value(heap_object) == heap_object_for_object_index(value_object_index), "Linker should have linked this correctly");
 447 
 448     // Replace the string with interned string
 449     heap_object = StringTable::intern(heap_object, CHECK_NULL);
 450   } else {
 451     heap_object = allocate_object(archive_object, mark, size, CHECK_NULL);
 452 
 453     // Fill in object contents
 454     copy_object_lazy_linking(object_index, archive_object, heap_object, size, dfs_stack);
 455   }
 456 
 457   // Install forwarding
 458   set_heap_object_for_object_index(object_index, heap_object);
 459 
 460   return heap_object;
 461 }
 462 
 463 oop AOTStreamedHeapLoader::TracingObjectLoader::materialize_object(int object_index, Stack<AOTHeapTraversalEntry, mtClassShared>& dfs_stack, TRAPS) {
 464   if (object_index <= _previous_batch_last_object_index) {
 465     // The transitive closure of this object has been materialized; no need to do anything
 466     return heap_object_for_object_index(object_index);
 467   }
 468 
 469   if (object_index <= _current_batch_last_object_index) {
 470     // The AOTThread is currently materializing this object and its transitive closure; only need to wait for it to complete
 471     _waiting_for_iterator = true;
 472     while (object_index > _previous_batch_last_object_index) {
 473       wait_for_iterator();
 474     }
 475     _waiting_for_iterator = false;
 476 
 477     // Notify the AOT thread if it is waiting for tracing to finish
 478     AOTHeapLoading_lock->notify_all();
 479     return heap_object_for_object_index(object_index);;
 480   }
 481 
 482   oop heap_object = heap_object_for_object_index(object_index);
 483   if (heap_object != nullptr) {
 484     // Already materialized by mutator
 485     return heap_object;
 486   }
 487 
 488   return materialize_object_inner(object_index, dfs_stack, THREAD);
 489 }
 490 
 491 void AOTStreamedHeapLoader::TracingObjectLoader::drain_stack(Stack<AOTHeapTraversalEntry, mtClassShared>& dfs_stack, TRAPS) {
 492   while (!dfs_stack.is_empty()) {
 493     AOTHeapTraversalEntry entry = dfs_stack.pop();
 494     int pointee_object_index = entry._pointee_object_index;
 495     oop pointee_heap_object = materialize_object(pointee_object_index, dfs_stack, CHECK);
 496     oop heap_object = heap_object_for_object_index(entry._base_object_index);
 497     if (_allow_gc) {
 498       heap_object->obj_field_put(entry._heap_field_offset_bytes, pointee_heap_object);
 499     } else {
 500       heap_object->obj_field_put_access<IS_DEST_UNINITIALIZED>(entry._heap_field_offset_bytes, pointee_heap_object);
 501     }
 502   }
 503 }
 504 
 505 oop AOTStreamedHeapLoader::TracingObjectLoader::materialize_object_transitive(int object_index, Stack<AOTHeapTraversalEntry, mtClassShared>& dfs_stack, TRAPS) {
 506   assert_locked_or_safepoint(AOTHeapLoading_lock);
 507   while (_waiting_for_iterator) {
 508     wait_for_iterator();
 509   }
 510 
 511   auto handlized_materialize_object = [&](TRAPS) {
 512     oop obj = materialize_object(object_index, dfs_stack, CHECK_(Handle()));
 513     return Handle(THREAD, obj);
 514   };
 515 
 516   Handle result = handlized_materialize_object(CHECK_NULL);
 517   drain_stack(dfs_stack, CHECK_NULL);
 518 
 519   return result();
 520 }
 521 
 522 oop AOTStreamedHeapLoader::TracingObjectLoader::materialize_root(int root_index, Stack<AOTHeapTraversalEntry, mtClassShared>& dfs_stack, TRAPS) {
 523   int root_object_index = object_index_for_root_index(root_index);
 524   oop root = materialize_object_transitive(root_object_index, dfs_stack, CHECK_NULL);
 525   install_root(root_index, root);
 526 
 527   return root;
 528 }
 529 
 530 int oop_handle_cmp(const void* left, const void* right) {
 531   oop* left_handle = *(oop**)left;
 532   oop* right_handle = *(oop**)right;
 533 
 534   if (right_handle > left_handle) {
 535     return -1;
 536   } else if (left_handle > right_handle) {
 537     return 1;
 538   }
 539 
 540   return 0;
 541 }
 542 
 543 // The range is inclusive
 544 void AOTStreamedHeapLoader::IterativeObjectLoader::initialize_range(int first_object_index, int last_object_index, TRAPS) {
 545   for (int i = first_object_index; i <= last_object_index; ++i) {
 546     oopDesc* archive_object = archive_object_for_object_index(i);
 547     markWord mark = archive_object->mark();
 548     bool string_intern = mark.is_marked();
 549     if (string_intern) {
 550       int value_object_index = archived_string_value_object_index(archive_object);
 551       if (value_object_index == i + 1) {
 552         // Interned strings are eagerly materialized in the allocation phase, so there is
 553         // nothing else to do for interned strings here for the string nor its value array.
 554         i++;
 555       }
 556       continue;
 557     }
 558     size_t size = archive_object_size(archive_object);
 559     oop heap_object = heap_object_for_object_index(i);
 560     copy_object_eager_linking(archive_object, heap_object, size);
 561   }
 562 }
 563 
 564 // The range is inclusive
 565 size_t AOTStreamedHeapLoader::IterativeObjectLoader::materialize_range(int first_object_index, int last_object_index, TRAPS) {
 566   GrowableArrayCHeap<int, mtClassShared> lazy_object_indices(0);
 567   size_t materialized_words = 0;
 568 
 569   for (int i = first_object_index; i <= last_object_index; ++i) {
 570     oopDesc* archive_object = archive_object_for_object_index(i);
 571     markWord mark = archive_object->mark();
 572 
 573     // The markWord is marked if the object is a String and it should be interned,
 574     // make sure to unmark it before allocating memory for the object.
 575     bool string_intern = mark.is_marked();
 576     mark = mark.set_unmarked();
 577 
 578     size_t size = archive_object_size(archive_object);
 579     materialized_words += size;
 580 
 581     oop heap_object = heap_object_for_object_index(i);
 582     if (heap_object != nullptr) {
 583       // Lazy loading has already initialized the object; we must not mutate it
 584       lazy_object_indices.append(i);
 585       continue;
 586     }
 587 
 588     if (!string_intern) {
 589      // The normal case; no lazy loading have loaded the object yet
 590       heap_object = allocate_object(archive_object, mark, size, CHECK_0);
 591       set_heap_object_for_object_index(i, heap_object);
 592       continue;
 593     }
 594 
 595     // Eagerly materialize interned strings to ensure that objects earlier than the string
 596     // in a batch get linked to the intended interned string, and not a copy.
 597     int value_object_index = archived_string_value_object_index(archive_object);
 598 
 599     bool is_normal_interned_string = value_object_index == i + 1;
 600 
 601     if (value_object_index < first_object_index) {
 602       // If materialized in a previous batch, the value should already be allocated and initialized.
 603       assert(heap_object_for_object_index(value_object_index) != nullptr, "should be materialized");
 604     } else {
 605       // Materialize the value object.
 606       oopDesc* archive_value_object = archive_object_for_object_index(value_object_index);
 607       markWord value_mark = archive_value_object->mark();
 608       size_t value_size = archive_object_size(archive_value_object);
 609       oop value_heap_object;
 610 
 611       if (is_normal_interned_string) {
 612         // The common case: the value is next to the string. This happens when only the interned
 613         // string points to its value character array.
 614         assert(value_object_index <= last_object_index, "Must be within this batch: %d <= %d", value_object_index, last_object_index);
 615         value_heap_object = allocate_object(archive_value_object, value_mark, value_size, CHECK_0);
 616         set_heap_object_for_object_index(value_object_index, value_heap_object);
 617         materialized_words += value_size;
 618       } else {
 619         // In the uncommon case, multiple strings point to the value of an interned string.
 620         // The string can then be earlier in the batch.
 621         assert(value_object_index < i, "surprising index");
 622         value_heap_object = heap_object_for_object_index(value_object_index);
 623       }
 624 
 625       copy_object_eager_linking(archive_value_object, value_heap_object, value_size);
 626     }
 627     // Allocate and link the string.
 628     heap_object = allocate_object(archive_object, mark, size, CHECK_0);
 629     copy_object_eager_linking(archive_object, heap_object, size);
 630 
 631     assert(java_lang_String::value(heap_object) == heap_object_for_object_index(value_object_index), "Linker should have linked this correctly");
 632 
 633     // Replace the string with interned string
 634     heap_object = StringTable::intern(heap_object, CHECK_0);
 635     set_heap_object_for_object_index(i, heap_object);
 636 
 637     if (is_normal_interned_string) {
 638       // Skip over the string value, already materialized
 639       i++;
 640     }
 641   }
 642 
 643   if (lazy_object_indices.is_empty()) {
 644     // Normal case; no sprinkled lazy objects in the root subgraph
 645     initialize_range(first_object_index, last_object_index, CHECK_0);
 646   } else {
 647     // The user lazy initialized some objects that are already initialized; we have to initialize around them
 648     // to make sure they are not mutated.
 649     int previous_object_index = first_object_index - 1; // Exclusive start of initialization slice
 650     for (int i = 0; i < lazy_object_indices.length(); ++i) {
 651       int lazy_object_index = lazy_object_indices.at(i);
 652       int slice_start_object_index = previous_object_index;
 653       int slice_end_object_index = lazy_object_index;
 654 
 655       if (slice_end_object_index - slice_start_object_index > 1) { // Both markers are exclusive
 656         initialize_range(slice_start_object_index + 1, slice_end_object_index - 1, CHECK_0);
 657       }
 658       previous_object_index = lazy_object_index;
 659     }
 660     // Process tail range
 661     if (last_object_index - previous_object_index > 0) {
 662       initialize_range(previous_object_index + 1, last_object_index, CHECK_0);
 663     }
 664   }
 665 
 666   return materialized_words;
 667 }
 668 
 669 bool AOTStreamedHeapLoader::IterativeObjectLoader::has_more() {
 670   return _current_root_index < _num_roots;
 671 }
 672 
 673 void AOTStreamedHeapLoader::IterativeObjectLoader::materialize_next_batch(TRAPS) {
 674   assert(has_more(), "only materialize if there is something to materialize");
 675 
 676   int min_batch_objects = 128;
 677   int from_root_index = _current_root_index;
 678   int max_to_root_index = _num_roots - 1;
 679   int until_root_index = from_root_index;
 680   int highest_object_index;
 681 
 682   // Expand the batch size from one root, to N roots until we cross 128 objects in total
 683   for (;;) {
 684     highest_object_index = highest_object_index_for_root_index(until_root_index);
 685     if (highest_object_index - _previous_batch_last_object_index >= min_batch_objects) {
 686       break;
 687     }
 688     if (until_root_index == max_to_root_index) {
 689       break;
 690     }
 691     until_root_index++;
 692   }
 693 
 694   oop root = nullptr;
 695 
 696   // Materialize objects of necessary, representing the transitive closure of the root
 697   if (highest_object_index > _previous_batch_last_object_index) {
 698     while (_swapping_root_format) {
 699       // When the roots are being upgraded to use handles, it is not safe to racingly
 700       // iterate over the object; we must wait. Setting the current batch last object index
 701       // to something other than the previous batch last object index indicates to the
 702       // root swapping that there is current iteration ongoing.
 703       AOTHeapLoading_lock->wait();
 704     }
 705     int first_object_index = _previous_batch_last_object_index + 1;
 706     _current_batch_last_object_index = highest_object_index;
 707     size_t allocated_words;
 708     {
 709       MutexUnlocker ml(AOTHeapLoading_lock, Mutex::_safepoint_check_flag);
 710       allocated_words = materialize_range(first_object_index, highest_object_index, CHECK);
 711     }
 712     _allocated_words += allocated_words;
 713     _previous_batch_last_object_index = _current_batch_last_object_index;
 714     if (_waiting_for_iterator) {
 715       // If tracer is waiting, let it know at the next point of unlocking that the root
 716       // set it waited for has been processed now.
 717       AOTHeapLoading_lock->notify_all();
 718     }
 719   }
 720 
 721   // Install the root
 722   for (int i = from_root_index; i <= until_root_index; ++i) {
 723     int root_object_index = object_index_for_root_index(i);
 724     root = heap_object_for_object_index(root_object_index);
 725     install_root(i, root);
 726     ++_current_root_index;
 727   }
 728 }
 729 
 730 bool AOTStreamedHeapLoader::materialize_early(TRAPS) {
 731   Ticks start = Ticks::now();
 732 
 733   // Only help with early materialization from the AOT thread if the heap archive can be allocated
 734   // without the need for a GC. Otherwise, do lazy loading until GC is enabled later in the bootstrapping.
 735   size_t bootstrap_max_memory = Universe::heap()->bootstrap_max_memory();
 736   size_t bootstrap_min_memory = MAX2(_heap_region_used, 2 * M);
 737 
 738   size_t before_gc_materialize_budget_bytes = (bootstrap_max_memory > bootstrap_min_memory) ? bootstrap_max_memory - bootstrap_min_memory : 0;
 739   size_t before_gc_materialize_budget_words = before_gc_materialize_budget_bytes / HeapWordSize;
 740 
 741   log_info(aot, heap)("Max bootstrapping memory: %zuM, min bootstrapping memory: %zuM, selected budget: %zuM",
 742                       bootstrap_max_memory / M, bootstrap_min_memory / M, before_gc_materialize_budget_bytes / M);
 743 
 744   while (IterativeObjectLoader::has_more()) {
 745     if (_allow_gc || _allocated_words > before_gc_materialize_budget_words) {
 746       log_info(aot, heap)("Early object materialization interrupted at root %d", _current_root_index);
 747       break;
 748     }
 749 
 750     IterativeObjectLoader::materialize_next_batch(CHECK_false);
 751   }
 752 
 753   _early_materialization_time_ns = (Ticks::now() - start).nanoseconds();
 754 
 755   bool finished_before_gc_allowed = !_allow_gc && !IterativeObjectLoader::has_more();
 756 
 757   return finished_before_gc_allowed;
 758 }
 759 
 760 void AOTStreamedHeapLoader::materialize_late(TRAPS) {
 761   Ticks start = Ticks::now();
 762 
 763   // Continue materializing with GC allowed
 764 
 765   while (IterativeObjectLoader::has_more()) {
 766     IterativeObjectLoader::materialize_next_batch(CHECK);
 767   }
 768 
 769   _late_materialization_time_ns = (Ticks::now() - start).nanoseconds();
 770 }
 771 
 772 void AOTStreamedHeapLoader::cleanup() {
 773   // First ensure there is no concurrent tracing going on
 774   while (_waiting_for_iterator) {
 775     AOTHeapLoading_lock->wait();
 776   }
 777 
 778   Ticks start = Ticks::now();
 779 
 780   // Remove OopStorage roots
 781   if (_objects_are_handles) {
 782     size_t num_handles = _num_archived_objects;
 783     // Skip the null entry
 784     oop** handles = ((oop**)_object_index_to_heap_object_table) + 1;
 785     // Sort the handles so that oop storage can release them faster
 786     qsort(handles, num_handles, sizeof(oop*), (int (*)(const void*, const void*))oop_handle_cmp);
 787     size_t num_null_handles = 0;
 788     for (size_t handles_remaining = num_handles; handles_remaining != 0; --handles_remaining) {
 789       oop* handle = handles[handles_remaining - 1];
 790       if (handle == nullptr) {
 791         num_null_handles = handles_remaining;
 792         break;
 793       }
 794       NativeAccess<>::oop_store(handle, nullptr);
 795     }
 796     Universe::vm_global()->release(&handles[num_null_handles], num_handles - num_null_handles);
 797   }
 798 
 799   FREE_C_HEAP_ARRAY(void*, _object_index_to_heap_object_table);
 800 
 801   // Unmap regions
 802   FileMapInfo::current_info()->unmap_region(AOTMetaspace::hp);
 803   FileMapInfo::current_info()->unmap_region(AOTMetaspace::bm);
 804 
 805   _cleanup_materialization_time_ns = (Ticks::now() - start).nanoseconds();
 806 
 807   log_statistics();
 808 }
 809 
 810 void AOTStreamedHeapLoader::log_statistics() {
 811   uint64_t total_duration_us = (Ticks::now() - _materialization_start_ticks).microseconds();
 812   const bool is_async = _loading_all_objects && !AOTEagerlyLoadObjects;
 813   const char* const async_or_sync = is_async ? "async" : "sync";
 814   log_info(aot, heap)("start to finish materialization time: " UINT64_FORMAT "us",
 815                       total_duration_us);
 816   log_info(aot, heap)("early object materialization time (%s): " UINT64_FORMAT "us",
 817                       async_or_sync, _early_materialization_time_ns / 1000);
 818   log_info(aot, heap)("late object materialization time (%s): " UINT64_FORMAT "us",
 819                       async_or_sync, _late_materialization_time_ns / 1000);
 820   log_info(aot, heap)("object materialization cleanup time (%s): " UINT64_FORMAT "us",
 821                       async_or_sync, _cleanup_materialization_time_ns / 1000);
 822   log_info(aot, heap)("final object materialization time stall (sync): " UINT64_FORMAT "us",
 823                       _final_materialization_time_ns / 1000);
 824   log_info(aot, heap)("bootstrapping lazy materialization time (sync): " UINT64_FORMAT "us",
 825                       _accumulated_lazy_materialization_time_ns / 1000);
 826 
 827   uint64_t sync_time = _final_materialization_time_ns + _accumulated_lazy_materialization_time_ns;
 828   uint64_t async_time = _early_materialization_time_ns + _late_materialization_time_ns + _cleanup_materialization_time_ns;
 829 
 830   if (!is_async) {
 831     sync_time += async_time;
 832     async_time = 0;
 833   }
 834 
 835   log_info(aot, heap)("sync materialization time: " UINT64_FORMAT "us",
 836                       sync_time / 1000);
 837 
 838   log_info(aot, heap)("async materialization time: " UINT64_FORMAT "us",
 839                       async_time / 1000);
 840 
 841   uint64_t iterative_time = (uint64_t)(is_async ? async_time : sync_time);
 842   uint64_t materialized_bytes = _allocated_words * HeapWordSize;
 843   log_info(aot, heap)("%s materialized " UINT64_FORMAT "K (" UINT64_FORMAT "M/s)", async_or_sync,
 844                       materialized_bytes / 1024, uint64_t(materialized_bytes * UCONST64(1'000'000'000) / M / iterative_time));
 845 }
 846 
 847 void AOTStreamedHeapLoader::materialize_objects() {
 848   // We cannot handle any exception when materializing roots. Exits the VM.
 849   EXCEPTION_MARK
 850 
 851   // Objects are laid out in DFS order; DFS traverse the roots by linearly walking all objects
 852   HandleMark hm(THREAD);
 853 
 854   // Early materialization with a budget before GC is allowed
 855   MutexLocker ml(AOTHeapLoading_lock, Mutex::_safepoint_check_flag);
 856 
 857   materialize_early(CHECK);
 858   await_gc_enabled();
 859   materialize_late(CHECK);
 860   // Notify materialization is done
 861   AOTHeapLoading_lock->notify_all();
 862   cleanup();
 863 }
 864 
 865 void AOTStreamedHeapLoader::switch_object_index_to_handle(int object_index) {
 866   oop heap_object = cast_to_oop(_object_index_to_heap_object_table[object_index]);
 867   if (heap_object == nullptr) {
 868     return;
 869   }
 870 
 871   oop* handle = Universe::vm_global()->allocate();
 872   NativeAccess<>::oop_store(handle, heap_object);
 873   _object_index_to_heap_object_table[object_index] = handle;
 874 }
 875 
 876 void AOTStreamedHeapLoader::enable_gc() {
 877   if (AOTEagerlyLoadObjects && !IterativeObjectLoader::has_more()) {
 878     // Everything was loaded eagerly at early startup
 879     return;
 880   }
 881 
 882   // We cannot handle any exception when materializing roots. Exits the VM.
 883   EXCEPTION_MARK
 884 
 885   MutexLocker ml(AOTHeapLoading_lock, Mutex::_safepoint_check_flag);
 886 
 887   // First wait until no tracing is active
 888   while (_waiting_for_iterator) {
 889     AOTHeapLoading_lock->wait();
 890   }
 891 
 892   // Lock further tracing from starting
 893   _waiting_for_iterator = true;
 894 
 895   // Record iterator progress
 896   int num_handles = (int)_num_archived_objects;
 897 
 898   // Lock further iteration from starting
 899   _swapping_root_format = true;
 900 
 901   // Then wait for the iterator to stop
 902   while (_previous_batch_last_object_index != _current_batch_last_object_index) {
 903     AOTHeapLoading_lock->wait();
 904   }
 905 
 906   if (IterativeObjectLoader::has_more()) {
 907     // If there is more to be materialized, we have to upgrade the object index
 908     // to object mapping to use handles. If there isn't more to materialize, the
 909     // handle will no longer e used; they are only used to materialize objects.
 910 
 911     for (int i = 1; i <= num_handles; ++i) {
 912       // Upgrade the roots to use handles
 913       switch_object_index_to_handle(i);
 914     }
 915 
 916     // From now on, accessing the object table must be done through a handle.
 917     _objects_are_handles = true;
 918   }
 919 
 920   // Unlock tracing
 921   _waiting_for_iterator = false;
 922 
 923   // Unlock iteration
 924   _swapping_root_format = false;
 925 
 926   _allow_gc = true;
 927 
 928   AOTHeapLoading_lock->notify_all();
 929 
 930   if (AOTEagerlyLoadObjects && IterativeObjectLoader::has_more()) {
 931     materialize_late(CHECK);
 932     cleanup();
 933   }
 934 }
 935 
 936 void AOTStreamedHeapLoader::materialize_thread_object() {
 937   AOTThread::materialize_thread_object();
 938 }
 939 
 940 void AOTStreamedHeapLoader::finish_materialize_objects() {
 941   Ticks start = Ticks::now();
 942 
 943   if (_loading_all_objects) {
 944     MutexLocker ml(AOTHeapLoading_lock, Mutex::_safepoint_check_flag);
 945     // Wait for the AOT thread to finish
 946     while (IterativeObjectLoader::has_more()) {
 947       AOTHeapLoading_lock->wait();
 948     }
 949   } else {
 950     assert(!AOTEagerlyLoadObjects, "sanity");
 951     assert(_current_root_index == 0, "sanity");
 952     // Without the full module graph we have done only lazy tracing materialization.
 953     // Ensure all roots are processed here by triggering root loading on every root.
 954     for (int i = 0; i < _num_roots; ++i) {
 955       get_root(i);
 956     }
 957     cleanup();
 958   }
 959 
 960   _final_materialization_time_ns = (Ticks::now() - start).nanoseconds();
 961 }
 962 
 963 void account_lazy_materialization_time_ns(uint64_t time, const char* description, int index) {
 964   AtomicAccess::add(&_accumulated_lazy_materialization_time_ns, time);
 965   log_debug(aot, heap)("Lazy materialization of %s: %d end (" UINT64_FORMAT " us of " UINT64_FORMAT " us)", description, index, time / 1000, _accumulated_lazy_materialization_time_ns / 1000);
 966 }
 967 
 968 // Initialize an empty array of AOT heap roots; materialize them lazily
 969 void AOTStreamedHeapLoader::initialize() {
 970   EXCEPTION_MARK
 971 
 972   _materialization_start_ticks = Ticks::now();
 973 
 974   FileMapInfo::current_info()->map_bitmap_region();
 975 
 976   _heap_region = FileMapInfo::current_info()->region_at(AOTMetaspace::hp);
 977   _bitmap_region = FileMapInfo::current_info()->region_at(AOTMetaspace::bm);
 978 
 979   assert(_heap_region->used() > 0, "empty heap archive?");
 980 
 981   _is_in_use = true;
 982 
 983   // archived roots are at this offset in the stream.
 984   size_t roots_offset = FileMapInfo::current_info()->streamed_heap()->roots_offset();
 985   size_t forwarding_offset = FileMapInfo::current_info()->streamed_heap()->forwarding_offset();
 986   size_t root_highest_object_index_table_offset = FileMapInfo::current_info()->streamed_heap()->root_highest_object_index_table_offset();
 987   _num_archived_objects = FileMapInfo::current_info()->streamed_heap()->num_archived_objects();
 988 
 989   // The first int is the length of the array
 990   _roots_archive = ((int*)(((address)_heap_region->mapped_base()) + roots_offset)) + 1;
 991   _num_roots = _roots_archive[-1];
 992   _heap_region_used = _heap_region->used();
 993 
 994   // We can't retire a TLAB until the filler klass is set; set it to the archived object klass.
 995   CollectedHeap::set_filler_object_klass(vmClasses::Object_klass());
 996 
 997   objArrayOop roots = oopFactory::new_objectArray(_num_roots, CHECK);
 998   _roots = OopHandle(Universe::vm_global(), roots);
 999 
1000   _object_index_to_buffer_offset_table = (size_t*)(((address)_heap_region->mapped_base()) + forwarding_offset);
1001   // We allocate the first entry for "null"
1002   _object_index_to_heap_object_table = NEW_C_HEAP_ARRAY(void*, _num_archived_objects + 1, mtClassShared);
1003   Copy::zero_to_bytes(_object_index_to_heap_object_table, (_num_archived_objects + 1) * sizeof(void*));
1004 
1005   _root_highest_object_index_table = (int*)(((address)_heap_region->mapped_base()) + root_highest_object_index_table_offset);
1006 
1007   address start = (address)(_bitmap_region->mapped_base()) + _heap_region->oopmap_offset();
1008   _oopmap = BitMapView((BitMap::bm_word_t*)start, _heap_region->oopmap_size_in_bits());
1009 
1010 
1011   if (FLAG_IS_DEFAULT(AOTEagerlyLoadObjects)) {
1012     // Concurrency will not help much if there are no extra cores available.
1013     FLAG_SET_ERGO(AOTEagerlyLoadObjects, os::initial_active_processor_count() <= 1);
1014   }
1015 
1016   // If the full module graph is not available or the JVMTI class file load hook is on, we
1017   // will prune the object graph to not include cached objects in subgraphs that are not intended
1018   // to be loaded.
1019   _loading_all_objects = CDSConfig::is_using_full_module_graph() && !JvmtiExport::should_post_class_file_load_hook();
1020   if (!_loading_all_objects) {
1021     // When not using FMG, fall back to tracing materialization
1022     FLAG_SET_ERGO(AOTEagerlyLoadObjects, false);
1023     return;
1024   }
1025 
1026   if (AOTEagerlyLoadObjects) {
1027     // Objects are laid out in DFS order; DFS traverse the roots by linearly walking all objects
1028     HandleMark hm(THREAD);
1029 
1030     // Early materialization with a budget before GC is allowed
1031     MutexLocker ml(AOTHeapLoading_lock, Mutex::_safepoint_check_flag);
1032 
1033     bool finished_before_gc_allowed = materialize_early(CHECK);
1034     if (finished_before_gc_allowed) {
1035       cleanup();
1036     }
1037   } else {
1038     AOTThread::initialize();
1039   }
1040 }
1041 
1042 oop AOTStreamedHeapLoader::materialize_root(int root_index) {
1043   Ticks start = Ticks::now();
1044   // We cannot handle any exception when materializing a root. Exits the VM.
1045   EXCEPTION_MARK
1046   Stack<AOTHeapTraversalEntry, mtClassShared> dfs_stack;
1047   HandleMark hm(THREAD);
1048 
1049   oop result;
1050   {
1051     MutexLocker ml(AOTHeapLoading_lock, Mutex::_safepoint_check_flag);
1052 
1053     oop root = objArrayOop(_roots.resolve())->obj_at(root_index);
1054 
1055     if (root != nullptr) {
1056       // The root has already been materialized
1057       result = root;
1058     } else {
1059       // The root has not been materialized, start tracing materialization
1060       result = TracingObjectLoader::materialize_root(root_index, dfs_stack, CHECK_NULL);
1061     }
1062   }
1063 
1064   uint64_t duration = (Ticks::now() - start).nanoseconds();
1065 
1066   account_lazy_materialization_time_ns(duration, "root", root_index);
1067 
1068   return result;
1069 }
1070 
1071 oop AOTStreamedHeapLoader::get_root(int index) {
1072   oop result = objArrayOop(_roots.resolve())->obj_at(index);
1073   if (result == nullptr) {
1074     // Materialize root
1075     result = materialize_root(index);
1076   }
1077   if (result == _roots.resolve()) {
1078     // A self-reference to the roots array acts as a sentinel object for null,
1079     // indicating that the root has been cleared.
1080     result = nullptr;
1081   }
1082   // Acquire the root transitive object payload
1083   OrderAccess::acquire();
1084   return result;
1085 }
1086 
1087 void AOTStreamedHeapLoader::clear_root(int index) {
1088   // Self-reference to the roots array acts as a sentinel object for null,
1089   // indicating that the root has been cleared.
1090   objArrayOop(_roots.resolve())->obj_at_put(index, _roots.resolve());
1091 }
1092 
1093 void AOTStreamedHeapLoader::await_gc_enabled() {
1094   while (!_allow_gc) {
1095     AOTHeapLoading_lock->wait();
1096   }
1097 }
1098 
1099 void AOTStreamedHeapLoader::finish_initialization(FileMapInfo* static_mapinfo) {
1100   static_mapinfo->stream_heap_region();
1101 }
1102 
1103 AOTMapLogger::OopDataIterator* AOTStreamedHeapLoader::oop_iterator(FileMapInfo* info, address buffer_start, address buffer_end) {
1104   class StreamedLoaderOopIterator : public AOTMapLogger::OopDataIterator {
1105   private:
1106     int _current;
1107     int _next;
1108 
1109     address _buffer_start;
1110 
1111     int _num_archived_objects;
1112 
1113   public:
1114     StreamedLoaderOopIterator(address buffer_start,
1115                               int num_archived_objects)
1116       : _current(0),
1117         _next(1),
1118         _buffer_start(buffer_start),
1119         _num_archived_objects(num_archived_objects) {
1120     }
1121 
1122     AOTMapLogger::OopData capture(int dfs_index) {
1123       size_t buffered_offset = buffer_offset_for_object_index(dfs_index);
1124       address buffered_addr = _buffer_start + buffered_offset;
1125       oopDesc* raw_oop = (oopDesc*)buffered_addr;
1126       size_t size = archive_object_size(raw_oop);
1127 
1128       intptr_t target_location = (intptr_t)buffered_offset;
1129       uint32_t narrow_location = checked_cast<uint32_t>(dfs_index);
1130       Klass* klass = raw_oop->klass();
1131 
1132       address requested_addr = (address)buffered_offset;
1133 
1134       return { buffered_addr,
1135                requested_addr,
1136                target_location,
1137                narrow_location,
1138                raw_oop,
1139                klass,
1140                size,
1141                false };
1142     }
1143 
1144     bool has_next() override {
1145       return _next <= _num_archived_objects;
1146     }
1147 
1148     AOTMapLogger::OopData next() override {
1149       _current = _next;
1150       AOTMapLogger::OopData result = capture(_current);
1151       _next = _current + 1;
1152       return result;
1153     }
1154 
1155     AOTMapLogger::OopData obj_at(narrowOop* addr) override {
1156       int dfs_index = (int)(*addr);
1157       if (dfs_index == 0) {
1158         return null_data();
1159       } else {
1160         return capture(dfs_index);
1161       }
1162     }
1163 
1164     AOTMapLogger::OopData obj_at(oop* addr) override {
1165       int dfs_index = (int)cast_from_oop<uintptr_t>(*addr);
1166       if (dfs_index == 0) {
1167         return null_data();
1168       } else {
1169         return capture(dfs_index);
1170       }
1171     }
1172 
1173     GrowableArrayCHeap<AOTMapLogger::OopData, mtClass>* roots() override {
1174       GrowableArrayCHeap<AOTMapLogger::OopData, mtClass>* result = new GrowableArrayCHeap<AOTMapLogger::OopData, mtClass>();
1175 
1176       for (int i = 0; i < _num_roots; ++i) {
1177         int object_index = object_index_for_root_index(i);
1178         result->append(capture(object_index));
1179       }
1180 
1181       return result;
1182     }
1183   };
1184 
1185   assert(_is_in_use, "printing before initializing?");
1186 
1187   return new StreamedLoaderOopIterator(buffer_start, (int)info->streamed_heap()->num_archived_objects());
1188 }
1189 
1190 #endif // INCLUDE_CDS_JAVA_HEAP