DXR is a code search and navigation tool aimed at making sense of large projects. It supports full-text and regex searches as well as structural queries.

Implementation

Mercurial (b6d82b1a6b02)

VCS Links

Line Code
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615 616 617 618 619 620 621 622 623 624 625 626 627 628 629 630 631 632 633 634 635 636 637 638
/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
 * vim: set ts=8 sw=2 et tw=80:
 *
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this file,
 * You can obtain one at http://mozilla.org/MPL/2.0/. */

#ifndef gc_Nursery_h
#define gc_Nursery_h

#include "mozilla/EnumeratedArray.h"
#include "mozilla/TimeStamp.h"

#include "gc/GCParallelTask.h"
#include "gc/Heap.h"
#include "js/Class.h"
#include "js/HeapAPI.h"
#include "js/TracingAPI.h"
#include "js/TypeDecls.h"
#include "js/Vector.h"

#define FOR_EACH_NURSERY_PROFILE_TIME(_)      \
  /* Key                       Header text */ \
  _(Total, "total")                           \
  _(CancelIonCompilations, "canIon")          \
  _(TraceValues, "mkVals")                    \
  _(TraceCells, "mkClls")                     \
  _(TraceSlots, "mkSlts")                     \
  _(TraceWholeCells, "mcWCll")                \
  _(TraceGenericEntries, "mkGnrc")            \
  _(CheckHashTables, "ckTbls")                \
  _(MarkRuntime, "mkRntm")                    \
  _(MarkDebugger, "mkDbgr")                   \
  _(SweepCaches, "swpCch")                    \
  _(CollectToFP, "collct")                    \
  _(ObjectsTenuredCallback, "tenCB")          \
  _(Sweep, "sweep")                           \
  _(UpdateJitActivations, "updtIn")           \
  _(FreeMallocedBuffers, "frSlts")            \
  _(ClearStoreBuffer, "clrSB")                \
  _(ClearNursery, "clear")                    \
  _(Pretenure, "pretnr")

template <typename T>
class SharedMem;

namespace js {

class AutoLockGCBgAlloc;
class ObjectElements;
class PlainObject;
class NativeObject;
class Nursery;
struct NurseryChunk;
class HeapSlot;
class JSONPrinter;
class MapObject;
class SetObject;

namespace gc {
class AutoMaybeStartBackgroundAllocation;
class AutoTraceSession;
struct Cell;
class GCSchedulingTunables;
class MinorCollectionTracer;
class RelocationOverlay;
struct TenureCountCache;
enum class AllocKind : uint8_t;
class TenuredCell;
}  // namespace gc

namespace jit {
class MacroAssembler;
}  // namespace jit

class NurseryDecommitTask : public GCParallelTaskHelper<NurseryDecommitTask> {
 public:
  explicit NurseryDecommitTask(JSRuntime* rt) : GCParallelTaskHelper(rt) {}

  void queueChunk(NurseryChunk* chunk, const AutoLockHelperThreadState& lock);

  // queueRange can also update the current to-decommit range of the
  // current chunk.
  void queueRange(size_t newCapacity, NurseryChunk& chunk,
                  const AutoLockHelperThreadState& lock);

  void run();
  void decommitChunk(gc::Chunk* chunk);
  void decommitRange(AutoLockHelperThreadState& lock);

 private:
  // Use the next pointers in Chunk::info to form a singly-linked list.
  MainThreadOrGCTaskData<gc::Chunk*> queue;

  MainThreadOrGCTaskData<NurseryChunk*> partialChunk;
  MainThreadOrGCTaskData<size_t> partialCapacity;

  gc::Chunk* popChunk(const AutoLockHelperThreadState& lock);
};

class TenuringTracer : public JSTracer {
  friend class Nursery;
  Nursery& nursery_;

  // Amount of data moved to the tenured generation during collection.
  size_t tenuredSize;
  // Number of cells moved to the tenured generation.
  size_t tenuredCells;

  // These lists are threaded through the Nursery using the space from
  // already moved things. The lists are used to fix up the moved things and
  // to find things held live by intra-Nursery pointers.
  gc::RelocationOverlay* objHead;
  gc::RelocationOverlay** objTail;
  gc::RelocationOverlay* stringHead;
  gc::RelocationOverlay** stringTail;

  TenuringTracer(JSRuntime* rt, Nursery* nursery);

 public:
  Nursery& nursery() { return nursery_; }

  template <typename T>
  void traverse(T** thingp);
  template <typename T>
  void traverse(T* thingp);

  // The store buffers need to be able to call these directly.
  void traceObject(JSObject* src);
  void traceObjectSlots(NativeObject* nobj, uint32_t start, uint32_t length);
  void traceSlots(JS::Value* vp, uint32_t nslots);
  void traceString(JSString* src);

 private:
  inline void insertIntoObjectFixupList(gc::RelocationOverlay* entry);
  inline void insertIntoStringFixupList(gc::RelocationOverlay* entry);

  template <typename T>
  inline T* allocTenured(JS::Zone* zone, gc::AllocKind kind);

  inline JSObject* movePlainObjectToTenured(PlainObject* src);
  JSObject* moveToTenuredSlow(JSObject* src);
  JSString* moveToTenured(JSString* src);

  size_t moveElementsToTenured(NativeObject* dst, NativeObject* src,
                               gc::AllocKind dstKind);
  size_t moveSlotsToTenured(NativeObject* dst, NativeObject* src);
  size_t moveStringToTenured(JSString* dst, JSString* src,
                             gc::AllocKind dstKind);

  void traceSlots(JS::Value* vp, JS::Value* end);
};

// Classes with JSCLASS_SKIP_NURSERY_FINALIZE or Wrapper classes with
// CROSS_COMPARTMENT flags will not have their finalizer called if they are
// nursery allocated and not promoted to the tenured heap. The finalizers for
// these classes must do nothing except free data which was allocated via
// Nursery::allocateBuffer.
inline bool CanNurseryAllocateFinalizedClass(const JSClass* const clasp) {
  MOZ_ASSERT(clasp->hasFinalize());
  return clasp->flags & JSCLASS_SKIP_NURSERY_FINALIZE;
}

class Nursery {
 public:
  static const size_t Alignment = gc::ChunkSize;
  static const size_t ChunkShift = gc::ChunkShift;

  // SubChunkStep is the minimum amount to adjust the nursery's size by.
  static const size_t SubChunkStep = gc::ArenaSize;

  struct alignas(gc::CellAlignBytes) CellAlignedByte {
    char byte;
  };

  struct StringLayout {
    JS::Zone* zone;
    CellAlignedByte cell;
  };

  using BufferSet = HashSet<void*, PointerHasher<void*>, SystemAllocPolicy>;

  explicit Nursery(JSRuntime* rt);
  ~Nursery();

  MOZ_MUST_USE bool init(uint32_t maxNurseryBytes, AutoLockGCBgAlloc& lock);

  unsigned chunkCountLimit() const { return chunkCountLimit_; }

  // Number of allocated (ready to use) chunks.
  unsigned allocatedChunkCount() const { return chunks_.length(); }

  // Total number of chunks and the capacity of the nursery. Chunks will be
  // lazilly allocated and added to the chunks array up to this limit, after
  // that the nursery must be collected, this limit may be raised during
  // collection.
  unsigned maxChunkCount() const {
    MOZ_ASSERT(capacity());
    return JS_HOWMANY(capacity(), gc::ChunkSize);
  }

  bool exists() const { return chunkCountLimit() != 0; }

  void enable();
  void disable();
  bool isEnabled() const { return capacity() != 0; }

  void enableStrings();
  void disableStrings();
  bool canAllocateStrings() const { return canAllocateStrings_; }

  // Return true if no allocations have been made since the last collection.
  bool isEmpty() const;

  // Check whether an arbitrary pointer is within the nursery. This is
  // slower than IsInsideNursery(Cell*), but works on all types of pointers.
  MOZ_ALWAYS_INLINE bool isInside(gc::Cell* cellp) const = delete;
  MOZ_ALWAYS_INLINE bool isInside(const void* p) const {
    for (auto chunk : chunks_) {
      if (uintptr_t(p) - uintptr_t(chunk) < gc::ChunkSize) {
        return true;
      }
    }
    return false;
  }

  template <typename T>
  inline bool isInside(const SharedMem<T>& p) const;

  // Allocate and return a pointer to a new GC object with its |slots|
  // pointer pre-filled. Returns nullptr if the Nursery is full.
  JSObject* allocateObject(JSContext* cx, size_t size, size_t numDynamic,
                           const JSClass* clasp);

  // Allocate and return a pointer to a new string. Returns nullptr if the
  // Nursery is full.
  gc::Cell* allocateString(JS::Zone* zone, size_t size, gc::AllocKind kind);

  // String zones are stored just before the string in nursery memory.
  static JS::Zone* getStringZone(const JSString* str) {
#ifdef DEBUG
    auto cell = reinterpret_cast<const js::gc::Cell*>(
        str);  // JSString type is incomplete here
    MOZ_ASSERT(js::gc::IsInsideNursery(cell),
               "getStringZone must be passed a nursery string");
#endif

    auto layout =
        reinterpret_cast<const uint8_t*>(str) - offsetof(StringLayout, cell);
    return reinterpret_cast<const StringLayout*>(layout)->zone;
  }

  static size_t stringHeaderSize() { return offsetof(StringLayout, cell); }

  // Allocate a buffer for a given zone, using the nursery if possible.
  void* allocateBuffer(JS::Zone* zone, size_t nbytes);

  // Allocate a buffer for a given object, using the nursery if possible and
  // obj is in the nursery.
  void* allocateBuffer(JSObject* obj, size_t nbytes);

  // Allocate a buffer for a given object, always using the nursery if obj is
  // in the nursery. The requested size must be less than or equal to
  // MaxNurseryBufferSize.
  void* allocateBufferSameLocation(JSObject* obj, size_t nbytes);

  // Allocate a zero-initialized buffer for a given zone, using the nursery if
  // possible. If the buffer isn't allocated in the nursery, the given arena is
  // used.
  void* allocateZeroedBuffer(JS::Zone* zone, size_t nbytes,
                             arena_id_t arena = js::MallocArena);

  // Allocate a zero-initialized buffer for a given object, using the nursery if
  // possible and obj is in the nursery. If the buffer isn't allocated in the
  // nursery, the given arena is used.
  void* allocateZeroedBuffer(JSObject* obj, size_t nbytes,
                             arena_id_t arena = js::MallocArena);

  // Resize an existing object buffer.
  void* reallocateBuffer(JSObject* obj, void* oldBuffer, size_t oldBytes,
                         size_t newBytes);

  // Free an object buffer.
  void freeBuffer(void* buffer);

  // The maximum number of bytes allowed to reside in nursery buffers.
  static const size_t MaxNurseryBufferSize = 1024;

  // Do a minor collection.
  void collect(JS::GCReason reason);

  // If the thing at |*ref| in the Nursery has been forwarded, set |*ref| to
  // the new location and return true. Otherwise return false and leave
  // |*ref| unset.
  MOZ_ALWAYS_INLINE MOZ_MUST_USE static bool getForwardedPointer(
      js::gc::Cell** ref);

  // Forward a slots/elements pointer stored in an Ion frame.
  void forwardBufferPointer(HeapSlot** pSlotsElems);

  inline void maybeSetForwardingPointer(JSTracer* trc, void* oldData,
                                        void* newData, bool direct);
  inline void setForwardingPointerWhileTenuring(void* oldData, void* newData,
                                                bool direct);

  // Register a malloced buffer that is held by a nursery object, which
  // should be freed at the end of a minor GC. Buffers are unregistered when
  // their owning objects are tenured.
  MOZ_MUST_USE bool registerMallocedBuffer(void* buffer);

  // Mark a malloced buffer as no longer needing to be freed.
  void removeMallocedBuffer(void* buffer) {
    MOZ_ASSERT(mallocedBuffers.has(buffer));
    mallocedBuffers.remove(buffer);
  }

  MOZ_MUST_USE bool addedUniqueIdToCell(gc::Cell* cell) {
    MOZ_ASSERT(IsInsideNursery(cell));
    MOZ_ASSERT(isEnabled());
    return cellsWithUid_.append(cell);
  }

  MOZ_MUST_USE bool queueDictionaryModeObjectToSweep(NativeObject* obj);

  size_t sizeOfMallocedBuffers(mozilla::MallocSizeOf mallocSizeOf) const {
    size_t total = 0;
    for (BufferSet::Range r = mallocedBuffers.all(); !r.empty(); r.popFront()) {
      total += mallocSizeOf(r.front());
    }
    total += mallocedBuffers.shallowSizeOfExcludingThis(mallocSizeOf);
    return total;
  }

  // The number of bytes from the start position to the end of the nursery.
  // pass maxChunkCount(), allocatedChunkCount() or chunkCountLimit()
  // to calculate the nursery size, current lazy-allocated size or nursery
  // limit respectively.
  size_t spaceToEnd(unsigned chunkCount) const;

  size_t capacity() const {
    MOZ_ASSERT(capacity_ <= chunkCountLimit() * gc::ChunkSize);
    return capacity_;
  }
  size_t committed() const { return spaceToEnd(allocatedChunkCount()); }

  // Used and free space both include chunk trailers for that part of the
  // nursery.
  //
  // usedSpace() + freeSpace() == capacity()
  //
  MOZ_ALWAYS_INLINE size_t usedSpace() const {
    return capacity() - freeSpace();
  }
  MOZ_ALWAYS_INLINE size_t freeSpace() const {
    MOZ_ASSERT(isEnabled());
    MOZ_ASSERT(currentEnd_ - position_ <= NurseryChunkUsableSize);
    MOZ_ASSERT(currentChunk_ < maxChunkCount());
    return (currentEnd_ - position_) +
           (maxChunkCount() - currentChunk_ - 1) * gc::ChunkSize;
  }

#ifdef JS_GC_ZEAL
  void enterZealMode();
  void leaveZealMode();
#endif

  // Write profile time JSON on JSONPrinter.
  void renderProfileJSON(JSONPrinter& json) const;

  // Print header line for profile times.
  static void printProfileHeader();

  // Print total profile times on shutdown.
  void printTotalProfileTimes();

  void* addressOfPosition() const { return (void**)&position_; }
  const void* addressOfCurrentEnd() const { return (void**)&currentEnd_; }
  const void* addressOfCurrentStringEnd() const {
    return (void*)&currentStringEnd_;
  }

  void requestMinorGC(JS::GCReason reason) const;

  bool minorGCRequested() const {
    return minorGCTriggerReason_ != JS::GCReason::NO_REASON;
  }
  JS::GCReason minorGCTriggerReason() const { return minorGCTriggerReason_; }
  void clearMinorGCRequest() {
    minorGCTriggerReason_ = JS::GCReason::NO_REASON;
  }

  bool shouldCollect() const;

  bool enableProfiling() const { return enableProfiling_; }

  bool addMapWithNurseryMemory(MapObject* obj) {
    MOZ_ASSERT_IF(!mapsWithNurseryMemory_.empty(),
                  mapsWithNurseryMemory_.back() != obj);
    return mapsWithNurseryMemory_.append(obj);
  }
  bool addSetWithNurseryMemory(SetObject* obj) {
    MOZ_ASSERT_IF(!setsWithNurseryMemory_.empty(),
                  setsWithNurseryMemory_.back() != obj);
    return setsWithNurseryMemory_.append(obj);
  }

  // The amount of space in the mapped nursery available to allocations.
  static const size_t NurseryChunkUsableSize =
      gc::ChunkSize - gc::ChunkTrailerSize;

  void joinDecommitTask() { decommitTask.join(); }

 private:
  JSRuntime* runtime_;

  // Vector of allocated chunks to allocate from.
  Vector<NurseryChunk*, 0, SystemAllocPolicy> chunks_;

  // Pointer to the first unallocated byte in the nursery.
  uintptr_t position_;

  // These fields refer to the beginning of the nursery. They're normally 0
  // and chunk(0).start() respectively. Except when a generational GC zeal
  // mode is active, then they may be arbitrary (see Nursery::clear()).
  unsigned currentStartChunk_;
  uintptr_t currentStartPosition_;

  // Pointer to the last byte of space in the current chunk.
  uintptr_t currentEnd_;

  // Pointer to the last byte of space in the current chunk, or nullptr if we
  // are not allocating strings in the nursery.
  uintptr_t currentStringEnd_;

  // The index of the chunk that is currently being allocated from.
  unsigned currentChunk_;

  // The current nursery capacity measured in bytes. It may grow up to this
  // value without a collection, allocating chunks on demand. This limit may be
  // changed by maybeResizeNursery() each collection. It does not include chunk
  // trailers.
  size_t capacity_;

  // This limit is fixed by configuration. It represents the maximum size
  // the nursery is permitted to tune itself to in maybeResizeNursery();
  unsigned chunkCountLimit_;

  mozilla::TimeDuration timeInChunkAlloc_;

  // Report minor collections taking at least this long, if enabled.
  mozilla::TimeDuration profileThreshold_;
  bool enableProfiling_;

  // Whether we will nursery-allocate strings.
  bool canAllocateStrings_;

  // Report ObjectGroups with at least this many instances tenured.
  int64_t reportTenurings_;

  // Whether and why a collection of this nursery has been requested. This is
  // mutable as it is set by the store buffer, which otherwise cannot modify
  // anything in the nursery.
  mutable JS::GCReason minorGCTriggerReason_;

  // Profiling data.

  enum class ProfileKey {
#define DEFINE_TIME_KEY(name, text) name,
    FOR_EACH_NURSERY_PROFILE_TIME(DEFINE_TIME_KEY)
#undef DEFINE_TIME_KEY
        KeyCount
  };

  using ProfileTimes =
      mozilla::EnumeratedArray<ProfileKey, ProfileKey::KeyCount,
                               mozilla::TimeStamp>;
  using ProfileDurations =
      mozilla::EnumeratedArray<ProfileKey, ProfileKey::KeyCount,
                               mozilla::TimeDuration>;

  ProfileTimes startTimes_;
  ProfileDurations profileDurations_;
  ProfileDurations totalDurations_;

  struct {
    JS::GCReason reason = JS::GCReason::NO_REASON;
    size_t nurseryCapacity = 0;
    size_t nurseryCommitted = 0;
    size_t nurseryUsedBytes = 0;
    size_t tenuredBytes = 0;
    size_t tenuredCells = 0;
  } previousGC;

  // Calculate the promotion rate of the most recent minor GC.
  // The valid_for_tenuring parameter is used to return whether this
  // promotion rate is accurate enough (the nursery was full enough) to be
  // used for tenuring and other decisions.
  //
  // Must only be called if the previousGC data is initialised.
  float calcPromotionRate(bool* validForTenuring) const;

  // The set of externally malloced buffers potentially kept live by objects
  // stored in the nursery. Any external buffers that do not belong to a
  // tenured thing at the end of a minor GC must be freed.
  BufferSet mallocedBuffers;

  // During a collection most hoisted slot and element buffers indicate their
  // new location with a forwarding pointer at the base. This does not work
  // for buffers whose length is less than pointer width, or when different
  // buffers might overlap each other. For these, an entry in the following
  // table is used.
  typedef HashMap<void*, void*, PointerHasher<void*>, SystemAllocPolicy>
      ForwardedBufferMap;
  ForwardedBufferMap forwardedBuffers;

  // When we assign a unique id to cell in the nursery, that almost always
  // means that the cell will be in a hash table, and thus, held live,
  // automatically moving the uid from the nursery to its new home in
  // tenured. It is possible, if rare, for an object that acquired a uid to
  // be dead before the next collection, in which case we need to know to
  // remove it when we sweep.
  //
  // Note: we store the pointers as Cell* here, resulting in an ugly cast in
  //       sweep. This is because this structure is used to help implement
  //       stable object hashing and we have to break the cycle somehow.
  using CellsWithUniqueIdVector = Vector<gc::Cell*, 8, SystemAllocPolicy>;
  CellsWithUniqueIdVector cellsWithUid_;

  using NativeObjectVector = Vector<NativeObject*, 0, SystemAllocPolicy>;
  NativeObjectVector dictionaryModeObjects_;

  // Lists of map and set objects allocated in the nursery or with iterators
  // allocated there. Such objects need to be swept after minor GC.
  Vector<MapObject*, 0, SystemAllocPolicy> mapsWithNurseryMemory_;
  Vector<SetObject*, 0, SystemAllocPolicy> setsWithNurseryMemory_;

  NurseryDecommitTask decommitTask;

#ifdef JS_GC_ZEAL
  struct Canary;
  Canary* lastCanary_;
#endif

  NurseryChunk& chunk(unsigned index) const { return *chunks_[index]; }

  // Set the current chunk. This updates the currentChunk_, position_
  // currentEnd_ and currentStringEnd_ values as approprite. It'll also
  // poison the chunk, either a portion of the chunk if it is already the
  // current chunk, or the whole chunk if fullPoison is true or it is not
  // the current chunk.
  void setCurrentChunk(unsigned chunkno);

  // extent is advisory, it will be ignored in sub-chunk and generational zeal
  // modes. It will be clamped to Min(NurseryChunkUsableSize, capacity_).
  void poisonAndInitCurrentChunk(size_t extent = NurseryChunkUsableSize);

  void setCurrentEnd();
  void setStartPosition();

  // Allocate the next chunk, or the first chunk for initialization.
  // Callers will probably want to call setCurrentChunk(0) next.
  MOZ_MUST_USE bool allocateNextChunk(unsigned chunkno,
                                      AutoLockGCBgAlloc& lock);

  MOZ_ALWAYS_INLINE uintptr_t currentEnd() const;

  uintptr_t position() const { return position_; }

  MOZ_ALWAYS_INLINE bool isSubChunkMode() const;

  JSRuntime* runtime() const { return runtime_; }
  gcstats::Statistics& stats() const;

  const js::gc::GCSchedulingTunables& tunables() const;

  // Common internal allocator function.
  void* allocate(size_t size);

  void doCollection(JS::GCReason reason, gc::TenureCountCache& tenureCounts);

  float doPretenuring(JSRuntime* rt, JS::GCReason reason,
                      gc::TenureCountCache& tenureCounts);

  // Move the object at |src| in the Nursery to an already-allocated cell
  // |dst| in Tenured.
  void collectToFixedPoint(TenuringTracer& trc,
                           gc::TenureCountCache& tenureCounts);

  // Handle relocation of slots/elements pointers stored in Ion frames.
  inline void setForwardingPointer(void* oldData, void* newData, bool direct);

  inline void setDirectForwardingPointer(void* oldData, void* newData);
  void setIndirectForwardingPointer(void* oldData, void* newData);

  inline void setSlotsForwardingPointer(HeapSlot* oldSlots, HeapSlot* newSlots,
                                        uint32_t nslots);
  inline void setElementsForwardingPointer(ObjectElements* oldHeader,
                                           ObjectElements* newHeader,
                                           uint32_t capacity);

  // Updates pointers to nursery objects that have been tenured and discards
  // pointers to objects that have been freed.
  void sweep(JSTracer* trc);

  // Reset the current chunk and position after a minor collection. Also poison
  // the nursery on debug & nightly builds.
  void clear();

  void sweepDictionaryModeObjects();
  void sweepMapAndSetObjects();

  // Change the allocable space provided by the nursery.
  void maybeResizeNursery(JS::GCReason reason);
  bool maybeResizeExact(JS::GCReason reason);
  size_t roundSize(size_t size) const;
  void growAllocableSpace(size_t newCapacity);
  void shrinkAllocableSpace(size_t newCapacity);
  void minimizeAllocableSpace();

  // Free the chunks starting at firstFreeChunk until the end of the chunks
  // vector. Shrinks the vector but does not update maxChunkCount().
  void freeChunksFrom(unsigned firstFreeChunk);

  // Profile recording and printing.
  void maybeClearProfileDurations();
  void startProfile(ProfileKey key);
  void endProfile(ProfileKey key);
  static void printProfileDurations(const ProfileDurations& times);

  friend class TenuringTracer;
  friend class gc::MinorCollectionTracer;
  friend class jit::MacroAssembler;
  friend struct NurseryChunk;
};

}  // namespace js

#endif  // gc_Nursery_h