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/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
 * vim: set ts=8 sts=2 et sw=2 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/. */

#include "gc/Scheduling.h"

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

#include "gc/RelocationOverlay.h"
#include "gc/ZoneAllocator.h"

using namespace js;
using namespace js::gc;

using mozilla::CheckedInt;
using mozilla::TimeDuration;

/*
 * We may start to collect a zone before its trigger threshold is reached if
 * GCRuntime::maybeGC() is called for that zone or we start collecting other
 * zones. These eager threshold factors are not configurable.
 */
static constexpr float HighFrequencyEagerAllocTriggerFactor = 0.85f;
static constexpr float LowFrequencyEagerAllocTriggerFactor = 0.9f;

/*
 * Don't allow heap growth factors to be set so low that eager collections could
 * reduce the trigger threshold.
 */
static constexpr float MinHeapGrowthFactor =
    1.0f / Min(HighFrequencyEagerAllocTriggerFactor,
               LowFrequencyEagerAllocTriggerFactor);

GCSchedulingTunables::GCSchedulingTunables()
    : gcMaxBytes_(0),
      gcMinNurseryBytes_(TuningDefaults::GCMinNurseryBytes),
      gcMaxNurseryBytes_(0),
      gcZoneAllocThresholdBase_(TuningDefaults::GCZoneAllocThresholdBase),
      nonIncrementalFactor_(TuningDefaults::NonIncrementalFactor),
      avoidInterruptFactor_(TuningDefaults::AvoidInterruptFactor),
      zoneAllocDelayBytes_(TuningDefaults::ZoneAllocDelayBytes),
      dynamicHeapGrowthEnabled_(TuningDefaults::DynamicHeapGrowthEnabled),
      highFrequencyThreshold_(
          TimeDuration::FromSeconds(TuningDefaults::HighFrequencyThreshold)),
      highFrequencyLowLimitBytes_(TuningDefaults::HighFrequencyLowLimitBytes),
      highFrequencyHighLimitBytes_(TuningDefaults::HighFrequencyHighLimitBytes),
      highFrequencyHeapGrowthMax_(TuningDefaults::HighFrequencyHeapGrowthMax),
      highFrequencyHeapGrowthMin_(TuningDefaults::HighFrequencyHeapGrowthMin),
      lowFrequencyHeapGrowth_(TuningDefaults::LowFrequencyHeapGrowth),
      dynamicMarkSliceEnabled_(TuningDefaults::DynamicMarkSliceEnabled),
      minEmptyChunkCount_(TuningDefaults::MinEmptyChunkCount),
      maxEmptyChunkCount_(TuningDefaults::MaxEmptyChunkCount),
      nurseryFreeThresholdForIdleCollection_(
          TuningDefaults::NurseryFreeThresholdForIdleCollection),
      nurseryFreeThresholdForIdleCollectionFraction_(
          TuningDefaults::NurseryFreeThresholdForIdleCollectionFraction),
      pretenureThreshold_(TuningDefaults::PretenureThreshold),
      pretenureGroupThreshold_(TuningDefaults::PretenureGroupThreshold),
      minLastDitchGCPeriod_(
          TimeDuration::FromSeconds(TuningDefaults::MinLastDitchGCPeriod)),
      mallocThresholdBase_(TuningDefaults::MallocThresholdBase),
      mallocGrowthFactor_(TuningDefaults::MallocGrowthFactor) {}

bool GCSchedulingTunables::setParameter(JSGCParamKey key, uint32_t value,
                                        const AutoLockGC& lock) {
  // Limit heap growth factor to one hundred times size of current heap.
  const float MaxHeapGrowthFactor = 100;
  const size_t MaxNurseryBytes = 128 * 1024 * 1024;

  switch (key) {
    case JSGC_MAX_BYTES:
      gcMaxBytes_ = value;
      break;
    case JSGC_MIN_NURSERY_BYTES:
      if (value > gcMaxNurseryBytes_ || value < ArenaSize ||
          value >= MaxNurseryBytes) {
        return false;
      }
      gcMinNurseryBytes_ = value;
      break;
    case JSGC_MAX_NURSERY_BYTES:
      if (value < gcMinNurseryBytes_ || value >= MaxNurseryBytes) {
        return false;
      }
      gcMaxNurseryBytes_ = value;
      break;
    case JSGC_HIGH_FREQUENCY_TIME_LIMIT:
      highFrequencyThreshold_ = TimeDuration::FromMilliseconds(value);
      break;
    case JSGC_HIGH_FREQUENCY_LOW_LIMIT: {
      CheckedInt<size_t> newLimit = CheckedInt<size_t>(value) * 1024 * 1024;
      if (!newLimit.isValid()) {
        return false;
      }
      setHighFrequencyLowLimit(newLimit.value());
      break;
    }
    case JSGC_HIGH_FREQUENCY_HIGH_LIMIT: {
      size_t newLimit = (size_t)value * 1024 * 1024;
      if (newLimit == 0) {
        return false;
      }
      setHighFrequencyHighLimit(newLimit);
      break;
    }
    case JSGC_HIGH_FREQUENCY_HEAP_GROWTH_MAX: {
      float newGrowth = value / 100.0f;
      if (newGrowth < MinHeapGrowthFactor || newGrowth > MaxHeapGrowthFactor) {
        return false;
      }
      setHighFrequencyHeapGrowthMax(newGrowth);
      break;
    }
    case JSGC_HIGH_FREQUENCY_HEAP_GROWTH_MIN: {
      float newGrowth = value / 100.0f;
      if (newGrowth < MinHeapGrowthFactor || newGrowth > MaxHeapGrowthFactor) {
        return false;
      }
      setHighFrequencyHeapGrowthMin(newGrowth);
      break;
    }
    case JSGC_LOW_FREQUENCY_HEAP_GROWTH: {
      float newGrowth = value / 100.0f;
      if (newGrowth < MinHeapGrowthFactor || newGrowth > MaxHeapGrowthFactor) {
        return false;
      }
      setLowFrequencyHeapGrowth(newGrowth);
      break;
    }
    case JSGC_DYNAMIC_HEAP_GROWTH:
      dynamicHeapGrowthEnabled_ = value != 0;
      break;
    case JSGC_DYNAMIC_MARK_SLICE:
      dynamicMarkSliceEnabled_ = value != 0;
      break;
    case JSGC_ALLOCATION_THRESHOLD:
      gcZoneAllocThresholdBase_ = value * 1024 * 1024;
      break;
    case JSGC_NON_INCREMENTAL_FACTOR: {
      float newFactor = value / 100.0f;
      if (newFactor < 1.0f) {
        return false;
      }
      nonIncrementalFactor_ = newFactor;
      break;
    }
    case JSGC_AVOID_INTERRUPT_FACTOR: {
      float newFactor = value / 100.0f;
      if (newFactor < 1.0f) {
        return false;
      }
      avoidInterruptFactor_ = newFactor;
      break;
    }
    case JSGC_MIN_EMPTY_CHUNK_COUNT:
      setMinEmptyChunkCount(value);
      break;
    case JSGC_MAX_EMPTY_CHUNK_COUNT:
      setMaxEmptyChunkCount(value);
      break;
    case JSGC_NURSERY_FREE_THRESHOLD_FOR_IDLE_COLLECTION:
      if (value > gcMaxNurseryBytes()) {
        value = gcMaxNurseryBytes();
      }
      nurseryFreeThresholdForIdleCollection_ = value;
      break;
    case JSGC_NURSERY_FREE_THRESHOLD_FOR_IDLE_COLLECTION_PERCENT:
      if (value == 0 || value > 100) {
        return false;
      }
      nurseryFreeThresholdForIdleCollectionFraction_ = value / 100.0f;
      break;
    case JSGC_PRETENURE_THRESHOLD: {
      // 100 disables pretenuring
      if (value == 0 || value > 100) {
        return false;
      }
      pretenureThreshold_ = value / 100.0f;
      break;
    }
    case JSGC_PRETENURE_GROUP_THRESHOLD:
      if (value <= 0) {
        return false;
      }
      pretenureGroupThreshold_ = value;
      break;
    case JSGC_MIN_LAST_DITCH_GC_PERIOD:
      minLastDitchGCPeriod_ = TimeDuration::FromSeconds(value);
      break;
    case JSGC_ZONE_ALLOC_DELAY_KB:
      zoneAllocDelayBytes_ = value * 1024;
      break;
    case JSGC_MALLOC_THRESHOLD_BASE:
      mallocThresholdBase_ = value * 1024 * 1024;
      break;
    case JSGC_MALLOC_GROWTH_FACTOR: {
      float newGrowth = value / 100.0f;
      if (newGrowth < MinHeapGrowthFactor || newGrowth > MaxHeapGrowthFactor) {
        return false;
      }
      mallocGrowthFactor_ = newGrowth;
      break;
    }
    default:
      MOZ_CRASH("Unknown GC parameter.");
  }

  return true;
}

void GCSchedulingTunables::setHighFrequencyLowLimit(size_t newLimit) {
  highFrequencyLowLimitBytes_ = newLimit;
  if (highFrequencyLowLimitBytes_ >= highFrequencyHighLimitBytes_) {
    highFrequencyHighLimitBytes_ = highFrequencyLowLimitBytes_ + 1;
  }
  MOZ_ASSERT(highFrequencyHighLimitBytes_ > highFrequencyLowLimitBytes_);
}

void GCSchedulingTunables::setHighFrequencyHighLimit(size_t newLimit) {
  highFrequencyHighLimitBytes_ = newLimit;
  if (highFrequencyHighLimitBytes_ <= highFrequencyLowLimitBytes_) {
    highFrequencyLowLimitBytes_ = highFrequencyHighLimitBytes_ - 1;
  }
  MOZ_ASSERT(highFrequencyHighLimitBytes_ > highFrequencyLowLimitBytes_);
}

void GCSchedulingTunables::setHighFrequencyHeapGrowthMin(float value) {
  highFrequencyHeapGrowthMin_ = value;
  if (highFrequencyHeapGrowthMin_ > highFrequencyHeapGrowthMax_) {
    highFrequencyHeapGrowthMax_ = highFrequencyHeapGrowthMin_;
  }
  MOZ_ASSERT(highFrequencyHeapGrowthMin_ >= MinHeapGrowthFactor);
  MOZ_ASSERT(highFrequencyHeapGrowthMin_ <= highFrequencyHeapGrowthMax_);
}

void GCSchedulingTunables::setHighFrequencyHeapGrowthMax(float value) {
  highFrequencyHeapGrowthMax_ = value;
  if (highFrequencyHeapGrowthMax_ < highFrequencyHeapGrowthMin_) {
    highFrequencyHeapGrowthMin_ = highFrequencyHeapGrowthMax_;
  }
  MOZ_ASSERT(highFrequencyHeapGrowthMin_ >= MinHeapGrowthFactor);
  MOZ_ASSERT(highFrequencyHeapGrowthMin_ <= highFrequencyHeapGrowthMax_);
}

void GCSchedulingTunables::setLowFrequencyHeapGrowth(float value) {
  lowFrequencyHeapGrowth_ = value;
  MOZ_ASSERT(lowFrequencyHeapGrowth_ >= MinHeapGrowthFactor);
}

void GCSchedulingTunables::setMinEmptyChunkCount(uint32_t value) {
  minEmptyChunkCount_ = value;
  if (minEmptyChunkCount_ > maxEmptyChunkCount_) {
    maxEmptyChunkCount_ = minEmptyChunkCount_;
  }
  MOZ_ASSERT(maxEmptyChunkCount_ >= minEmptyChunkCount_);
}

void GCSchedulingTunables::setMaxEmptyChunkCount(uint32_t value) {
  maxEmptyChunkCount_ = value;
  if (minEmptyChunkCount_ > maxEmptyChunkCount_) {
    minEmptyChunkCount_ = maxEmptyChunkCount_;
  }
  MOZ_ASSERT(maxEmptyChunkCount_ >= minEmptyChunkCount_);
}

void GCSchedulingTunables::resetParameter(JSGCParamKey key,
                                          const AutoLockGC& lock) {
  switch (key) {
    case JSGC_MAX_BYTES:
      gcMaxBytes_ = 0xffffffff;
      break;
    case JSGC_MIN_NURSERY_BYTES:
    case JSGC_MAX_NURSERY_BYTES:
      // Reset these togeather to maintain their min <= max invariant.
      gcMinNurseryBytes_ = TuningDefaults::GCMinNurseryBytes;
      gcMaxNurseryBytes_ = JS::DefaultNurseryBytes;
      break;
    case JSGC_HIGH_FREQUENCY_TIME_LIMIT:
      highFrequencyThreshold_ =
          TimeDuration::FromSeconds(TuningDefaults::HighFrequencyThreshold);
      break;
    case JSGC_HIGH_FREQUENCY_LOW_LIMIT:
      setHighFrequencyLowLimit(TuningDefaults::HighFrequencyLowLimitBytes);
      break;
    case JSGC_HIGH_FREQUENCY_HIGH_LIMIT:
      setHighFrequencyHighLimit(TuningDefaults::HighFrequencyHighLimitBytes);
      break;
    case JSGC_HIGH_FREQUENCY_HEAP_GROWTH_MAX:
      setHighFrequencyHeapGrowthMax(TuningDefaults::HighFrequencyHeapGrowthMax);
      break;
    case JSGC_HIGH_FREQUENCY_HEAP_GROWTH_MIN:
      setHighFrequencyHeapGrowthMin(TuningDefaults::HighFrequencyHeapGrowthMin);
      break;
    case JSGC_LOW_FREQUENCY_HEAP_GROWTH:
      setLowFrequencyHeapGrowth(TuningDefaults::LowFrequencyHeapGrowth);
      break;
    case JSGC_DYNAMIC_HEAP_GROWTH:
      dynamicHeapGrowthEnabled_ = TuningDefaults::DynamicHeapGrowthEnabled;
      break;
    case JSGC_DYNAMIC_MARK_SLICE:
      dynamicMarkSliceEnabled_ = TuningDefaults::DynamicMarkSliceEnabled;
      break;
    case JSGC_ALLOCATION_THRESHOLD:
      gcZoneAllocThresholdBase_ = TuningDefaults::GCZoneAllocThresholdBase;
      break;
    case JSGC_NON_INCREMENTAL_FACTOR:
      nonIncrementalFactor_ = TuningDefaults::NonIncrementalFactor;
      break;
    case JSGC_AVOID_INTERRUPT_FACTOR:
      avoidInterruptFactor_ = TuningDefaults::AvoidInterruptFactor;
      break;
    case JSGC_MIN_EMPTY_CHUNK_COUNT:
      setMinEmptyChunkCount(TuningDefaults::MinEmptyChunkCount);
      break;
    case JSGC_MAX_EMPTY_CHUNK_COUNT:
      setMaxEmptyChunkCount(TuningDefaults::MaxEmptyChunkCount);
      break;
    case JSGC_NURSERY_FREE_THRESHOLD_FOR_IDLE_COLLECTION:
      nurseryFreeThresholdForIdleCollection_ =
          TuningDefaults::NurseryFreeThresholdForIdleCollection;
      break;
    case JSGC_NURSERY_FREE_THRESHOLD_FOR_IDLE_COLLECTION_PERCENT:
      nurseryFreeThresholdForIdleCollectionFraction_ =
          TuningDefaults::NurseryFreeThresholdForIdleCollectionFraction;
      break;
    case JSGC_PRETENURE_THRESHOLD:
      pretenureThreshold_ = TuningDefaults::PretenureThreshold;
      break;
    case JSGC_PRETENURE_GROUP_THRESHOLD:
      pretenureGroupThreshold_ = TuningDefaults::PretenureGroupThreshold;
      break;
    case JSGC_MIN_LAST_DITCH_GC_PERIOD:
      minLastDitchGCPeriod_ =
          TimeDuration::FromSeconds(TuningDefaults::MinLastDitchGCPeriod);
      break;
    case JSGC_MALLOC_THRESHOLD_BASE:
      mallocThresholdBase_ = TuningDefaults::MallocThresholdBase;
      break;
    case JSGC_MALLOC_GROWTH_FACTOR:
      mallocGrowthFactor_ = TuningDefaults::MallocGrowthFactor;
      break;
    default:
      MOZ_CRASH("Unknown GC parameter.");
  }
}

float HeapThreshold::eagerAllocTrigger(bool highFrequencyGC) const {
  float eagerTriggerFactor = highFrequencyGC
                                 ? HighFrequencyEagerAllocTriggerFactor
                                 : LowFrequencyEagerAllocTriggerFactor;
  return eagerTriggerFactor * bytes();
}

/* static */
float GCHeapThreshold::computeZoneHeapGrowthFactorForHeapSize(
    size_t lastBytes, const GCSchedulingTunables& tunables,
    const GCSchedulingState& state) {
  if (!tunables.isDynamicHeapGrowthEnabled()) {
    return 3.0f;
  }

  // For small zones, our collection heuristics do not matter much: favor
  // something simple in this case.
  if (lastBytes < 1 * 1024 * 1024) {
    return tunables.lowFrequencyHeapGrowth();
  }

  // If GC's are not triggering in rapid succession, use a lower threshold so
  // that we will collect garbage sooner.
  if (!state.inHighFrequencyGCMode()) {
    return tunables.lowFrequencyHeapGrowth();
  }

  // The heap growth factor depends on the heap size after a GC and the GC
  // frequency. For low frequency GCs (more than 1sec between GCs) we let
  // the heap grow to 150%. For high frequency GCs we let the heap grow
  // depending on the heap size:
  //   lastBytes < highFrequencyLowLimit: 300%
  //   lastBytes > highFrequencyHighLimit: 150%
  //   otherwise: linear interpolation between 300% and 150% based on lastBytes

  float minRatio = tunables.highFrequencyHeapGrowthMin();
  float maxRatio = tunables.highFrequencyHeapGrowthMax();
  size_t lowLimit = tunables.highFrequencyLowLimitBytes();
  size_t highLimit = tunables.highFrequencyHighLimitBytes();

  MOZ_ASSERT(minRatio <= maxRatio);
  MOZ_ASSERT(lowLimit < highLimit);

  if (lastBytes <= lowLimit) {
    return maxRatio;
  }

  if (lastBytes >= highLimit) {
    return minRatio;
  }

  float factor = maxRatio - ((maxRatio - minRatio) *
                             ((lastBytes - lowLimit) / (highLimit - lowLimit)));

  MOZ_ASSERT(factor >= minRatio);
  MOZ_ASSERT(factor <= maxRatio);
  return factor;
}

/* static */
size_t GCHeapThreshold::computeZoneTriggerBytes(
    float growthFactor, size_t lastBytes, JSGCInvocationKind gckind,
    const GCSchedulingTunables& tunables, const AutoLockGC& lock) {
  size_t baseMin = gckind == GC_SHRINK
                       ? tunables.minEmptyChunkCount(lock) * ChunkSize
                       : tunables.gcZoneAllocThresholdBase();
  size_t base = Max(lastBytes, baseMin);
  float trigger = float(base) * growthFactor;
  float triggerMax =
      float(tunables.gcMaxBytes()) / tunables.nonIncrementalFactor();
  return size_t(Min(triggerMax, trigger));
}

void GCHeapThreshold::updateAfterGC(size_t lastBytes, JSGCInvocationKind gckind,
                                    const GCSchedulingTunables& tunables,
                                    const GCSchedulingState& state,
                                    const AutoLockGC& lock) {
  float growthFactor =
      computeZoneHeapGrowthFactorForHeapSize(lastBytes, tunables, state);
  bytes_ =
      computeZoneTriggerBytes(growthFactor, lastBytes, gckind, tunables, lock);
}

/* static */
size_t MallocHeapThreshold::computeZoneTriggerBytes(float growthFactor,
                                                    size_t lastBytes,
                                                    size_t baseBytes,
                                                    const AutoLockGC& lock) {
  return size_t(float(Max(lastBytes, baseBytes)) * growthFactor);
}

void MallocHeapThreshold::updateAfterGC(size_t lastBytes, size_t baseBytes,
                                        float growthFactor,
                                        const AutoLockGC& lock) {
  bytes_ = computeZoneTriggerBytes(growthFactor, lastBytes, baseBytes, lock);
}

#ifdef DEBUG

void MemoryTracker::adopt(MemoryTracker& other) {
  LockGuard<Mutex> lock(mutex);

  AutoEnterOOMUnsafeRegion oomUnsafe;

  for (auto r = other.map.all(); !r.empty(); r.popFront()) {
    if (!map.put(r.front().key(), r.front().value())) {
      oomUnsafe.crash("MemoryTracker::adopt");
    }
  }
  other.map.clear();

  // There may still be ZoneAllocPolicies associated with the old zone since
  // some are not destroyed until the zone itself dies. Instead check there is
  // no memory associated with them and clear their zone pointer in debug builds
  // to catch further memory association.
  for (auto r = other.policyMap.all(); !r.empty(); r.popFront()) {
    MOZ_ASSERT(r.front().value() == 0);
    r.front().key()->zone_ = nullptr;
  }
  other.policyMap.clear();
}

static const char* MemoryUseName(MemoryUse use) {
  switch (use) {
#  define DEFINE_CASE(Name) \
    case MemoryUse::Name:   \
      return #Name;
    JS_FOR_EACH_MEMORY_USE(DEFINE_CASE)
#  undef DEFINE_CASE
  }

  MOZ_CRASH("Unknown memory use");
}

MemoryTracker::MemoryTracker() : mutex(mutexid::MemoryTracker) {}

void MemoryTracker::checkEmptyOnDestroy() {
  bool ok = true;

  if (!map.empty()) {
    ok = false;
    fprintf(stderr, "Missing calls to JS::RemoveAssociatedMemory:\n");
    for (auto r = map.all(); !r.empty(); r.popFront()) {
      fprintf(stderr, "  %p 0x%zx %s\n", r.front().key().cell(),
              r.front().value(), MemoryUseName(r.front().key().use()));
    }
  }

  if (!policyMap.empty()) {
    ok = false;
    fprintf(stderr, "Missing calls to Zone::decPolicyMemory:\n");
    for (auto r = policyMap.all(); !r.empty(); r.popFront()) {
      fprintf(stderr, "  %p 0x%zx\n", r.front().key(), r.front().value());
    }
  }

  MOZ_ASSERT(ok);
}

inline bool MemoryTracker::allowMultipleAssociations(MemoryUse use) const {
  // For most uses only one association is possible for each GC thing. Allow a
  // one-to-many relationship only where necessary.
  return use == MemoryUse::RegExpSharedBytecode ||
         use == MemoryUse::BreakpointSite || use == MemoryUse::Breakpoint ||
         use == MemoryUse::ForOfPICStub;
}

void MemoryTracker::trackMemory(Cell* cell, size_t nbytes, MemoryUse use) {
  MOZ_ASSERT(cell->isTenured());

  LockGuard<Mutex> lock(mutex);

  Key key{cell, use};
  AutoEnterOOMUnsafeRegion oomUnsafe;
  auto ptr = map.lookupForAdd(key);
  if (ptr) {
    if (!allowMultipleAssociations(use)) {
      MOZ_CRASH_UNSAFE_PRINTF("Association already present: %p 0x%zx %s", cell,
                              nbytes, MemoryUseName(use));
    }
    ptr->value() += nbytes;
    return;
  }

  if (!map.add(ptr, key, nbytes)) {
    oomUnsafe.crash("MemoryTracker::noteExternalAlloc");
  }
}

void MemoryTracker::untrackMemory(Cell* cell, size_t nbytes, MemoryUse use) {
  MOZ_ASSERT(cell->isTenured());

  LockGuard<Mutex> lock(mutex);

  Key key{cell, use};
  auto ptr = map.lookup(key);
  if (!ptr) {
    MOZ_CRASH_UNSAFE_PRINTF("Association not found: %p 0x%zx %s", cell, nbytes,
                            MemoryUseName(use));
  }

  if (!allowMultipleAssociations(use) && ptr->value() != nbytes) {
    MOZ_CRASH_UNSAFE_PRINTF(
        "Association for %p %s has different size: "
        "expected 0x%zx but got 0x%zx",
        cell, MemoryUseName(use), ptr->value(), nbytes);
  }

  if (ptr->value() < nbytes) {
    MOZ_CRASH_UNSAFE_PRINTF(
        "Association for %p %s size is too small: "
        "expected at least 0x%zx but got 0x%zx",
        cell, MemoryUseName(use), nbytes, ptr->value());
  }

  ptr->value() -= nbytes;

  if (ptr->value() == 0) {
    map.remove(ptr);
  }
}

void MemoryTracker::swapMemory(Cell* a, Cell* b, MemoryUse use) {
  MOZ_ASSERT(a->isTenured());
  MOZ_ASSERT(b->isTenured());

  Key ka{a, use};
  Key kb{b, use};

  LockGuard<Mutex> lock(mutex);

  size_t sa = getAndRemoveEntry(ka, lock);
  size_t sb = getAndRemoveEntry(kb, lock);

  AutoEnterOOMUnsafeRegion oomUnsafe;

  if ((sa && !map.put(kb, sa)) || (sb && !map.put(ka, sb))) {
    oomUnsafe.crash("MemoryTracker::swapTrackedMemory");
  }
}

size_t MemoryTracker::getAndRemoveEntry(const Key& key,
                                        LockGuard<Mutex>& lock) {
  auto ptr = map.lookup(key);
  if (!ptr) {
    return 0;
  }

  size_t size = ptr->value();
  map.remove(ptr);
  return size;
}

void MemoryTracker::registerPolicy(ZoneAllocPolicy* policy) {
  LockGuard<Mutex> lock(mutex);

  auto ptr = policyMap.lookupForAdd(policy);
  if (ptr) {
    MOZ_CRASH_UNSAFE_PRINTF("ZoneAllocPolicy %p already registered", policy);
  }

  AutoEnterOOMUnsafeRegion oomUnsafe;
  if (!policyMap.add(ptr, policy, 0)) {
    oomUnsafe.crash("MemoryTracker::registerPolicy");
  }
}

void MemoryTracker::unregisterPolicy(ZoneAllocPolicy* policy) {
  LockGuard<Mutex> lock(mutex);

  auto ptr = policyMap.lookup(policy);
  if (!ptr) {
    MOZ_CRASH_UNSAFE_PRINTF("ZoneAllocPolicy %p not found", policy);
  }
  if (ptr->value() != 0) {
    MOZ_CRASH_UNSAFE_PRINTF(
        "ZoneAllocPolicy %p still has 0x%zx bytes associated", policy,
        ptr->value());
  }

  policyMap.remove(ptr);
}

void MemoryTracker::movePolicy(ZoneAllocPolicy* dst, ZoneAllocPolicy* src) {
  LockGuard<Mutex> lock(mutex);

  auto srcPtr = policyMap.lookup(src);
  if (!srcPtr) {
    MOZ_CRASH_UNSAFE_PRINTF("ZoneAllocPolicy %p not found", src);
  }

  size_t nbytes = srcPtr->value();
  policyMap.remove(srcPtr);

  auto dstPtr = policyMap.lookupForAdd(dst);
  if (dstPtr) {
    MOZ_CRASH_UNSAFE_PRINTF("ZoneAllocPolicy %p already registered", dst);
  }

  AutoEnterOOMUnsafeRegion oomUnsafe;
  if (!policyMap.add(dstPtr, dst, nbytes)) {
    oomUnsafe.crash("MemoryTracker::movePolicy");
  }
}

void MemoryTracker::incPolicyMemory(ZoneAllocPolicy* policy, size_t nbytes) {
  LockGuard<Mutex> lock(mutex);

  auto ptr = policyMap.lookup(policy);
  if (!ptr) {
    MOZ_CRASH_UNSAFE_PRINTF("ZoneAllocPolicy %p not found", policy);
  }

  ptr->value() += nbytes;
}

void MemoryTracker::decPolicyMemory(ZoneAllocPolicy* policy, size_t nbytes) {
  LockGuard<Mutex> lock(mutex);

  auto ptr = policyMap.lookup(policy);
  if (!ptr) {
    MOZ_CRASH_UNSAFE_PRINTF("ZoneAllocPolicy %p not found", policy);
  }

  size_t& value = ptr->value();
  if (value < nbytes) {
    MOZ_CRASH_UNSAFE_PRINTF(
        "ZoneAllocPolicy %p is too small: "
        "expected at least 0x%zx but got 0x%zx bytes",
        policy, nbytes, value);
  }

  value -= nbytes;
}

void MemoryTracker::fixupAfterMovingGC() {
  // Update the table after we move GC things. We don't use MovableCellHasher
  // because that would create a difference between debug and release builds.
  for (Map::Enum e(map); !e.empty(); e.popFront()) {
    const Key& key = e.front().key();
    Cell* cell = key.cell();
    if (cell->isForwarded()) {
      cell = gc::RelocationOverlay::fromCell(cell)->forwardingAddress();
      e.rekeyFront(Key{cell, key.use()});
    }
  }
}

inline MemoryTracker::Key::Key(Cell* cell, MemoryUse use)
    : cell_(uint64_t(cell)), use_(uint64_t(use)) {
#  ifdef JS_64BIT
  static_assert(sizeof(Key) == 8,
                "MemoryTracker::Key should be packed into 8 bytes");
#  endif
  MOZ_ASSERT(this->cell() == cell);
  MOZ_ASSERT(this->use() == use);
}

inline Cell* MemoryTracker::Key::cell() const {
  return reinterpret_cast<Cell*>(cell_);
}
inline MemoryUse MemoryTracker::Key::use() const {
  return static_cast<MemoryUse>(use_);
}

inline HashNumber MemoryTracker::Hasher::hash(const Lookup& l) {
  return mozilla::HashGeneric(DefaultHasher<Cell*>::hash(l.cell()),
                              DefaultHasher<unsigned>::hash(unsigned(l.use())));
}

inline bool MemoryTracker::Hasher::match(const Key& k, const Lookup& l) {
  return k.cell() == l.cell() && k.use() == l.use();
}

inline void MemoryTracker::Hasher::rekey(Key& k, const Key& newKey) {
  k = newKey;
}

#endif  // DEBUG