/* -*- 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/Zone-inl.h"
#include "js/shadow/Zone.h"  // JS::shadow::Zone

#include "mozilla/TimeStamp.h"

#include <type_traits>

#include "gc/FinalizationObservers.h"
#include "gc/GCContext.h"
#include "gc/PublicIterators.h"
#include "jit/BaselineIC.h"
#include "jit/BaselineJIT.h"
#include "jit/Invalidation.h"
#include "jit/JitZone.h"
#include "vm/Runtime.h"
#include "vm/Time.h"

#include "debugger/DebugAPI-inl.h"
#include "gc/GC-inl.h"
#include "gc/Marking-inl.h"
#include "gc/Nursery-inl.h"
#include "gc/WeakMap-inl.h"
#include "vm/JSScript-inl.h"
#include "vm/Realm-inl.h"

using namespace js;
using namespace js::gc;

Zone* const Zone::NotOnList = reinterpret_cast<Zone*>(1);

ZoneAllocator::ZoneAllocator(JSRuntime* rt, Kind kind)
    : JS::shadow::Zone(rt, rt->gc.marker().tracer(), kind),
      jitHeapThreshold(jit::MaxCodeBytesPerProcess * 0.8) {}

ZoneAllocator::~ZoneAllocator() {
#ifdef DEBUG
  mallocTracker.checkEmptyOnDestroy();
  MOZ_ASSERT(gcHeapSize.bytes() == 0);
  MOZ_ASSERT(mallocHeapSize.bytes() == 0);
  MOZ_ASSERT(jitHeapSize.bytes() == 0);
#endif
}

void ZoneAllocator::fixupAfterMovingGC() {
#ifdef DEBUG
  mallocTracker.fixupAfterMovingGC();
#endif
}

void js::ZoneAllocator::updateSchedulingStateOnGCStart() {
  gcHeapSize.updateOnGCStart();
  mallocHeapSize.updateOnGCStart();
  jitHeapSize.updateOnGCStart();
  perZoneGCTime = mozilla::TimeDuration();
}

void js::ZoneAllocator::updateGCStartThresholds(GCRuntime& gc) {
  bool isAtomsZone = JS::Zone::from(this)->isAtomsZone();
  gcHeapThreshold.updateStartThreshold(
      gcHeapSize.retainedBytes(), smoothedAllocationRate.ref(),
      smoothedCollectionRate.ref(), gc.tunables, gc.schedulingState,
      isAtomsZone);

  mallocHeapThreshold.updateStartThreshold(mallocHeapSize.retainedBytes(),
                                           gc.tunables, gc.schedulingState);
}

void js::ZoneAllocator::setGCSliceThresholds(GCRuntime& gc,
                                             bool waitingOnBGTask) {
  gcHeapThreshold.setSliceThreshold(this, gcHeapSize, gc.tunables,
                                    waitingOnBGTask);
  mallocHeapThreshold.setSliceThreshold(this, mallocHeapSize, gc.tunables,
                                        waitingOnBGTask);
  jitHeapThreshold.setSliceThreshold(this, jitHeapSize, gc.tunables,
                                     waitingOnBGTask);
}

void js::ZoneAllocator::clearGCSliceThresholds() {
  gcHeapThreshold.clearSliceThreshold();
  mallocHeapThreshold.clearSliceThreshold();
  jitHeapThreshold.clearSliceThreshold();
}

bool ZoneAllocator::addSharedMemory(void* mem, size_t nbytes, MemoryUse use) {
  // nbytes can be zero here for SharedArrayBuffers.

  MOZ_ASSERT(CurrentThreadCanAccessRuntime(runtime_));

  auto ptr = sharedMemoryUseCounts.lookupForAdd(mem);
  MOZ_ASSERT_IF(ptr, ptr->value().use == use);

  if (!ptr && !sharedMemoryUseCounts.add(ptr, mem, gc::SharedMemoryUse(use))) {
    return false;
  }

  ptr->value().count++;

  // Allocations can grow, so add any increase over the previous size and record
  // the new size.
  if (nbytes > ptr->value().nbytes) {
    mallocHeapSize.addBytes(nbytes - ptr->value().nbytes);
    ptr->value().nbytes = nbytes;
  }

  maybeTriggerGCOnMalloc();

  return true;
}

void ZoneAllocator::removeSharedMemory(void* mem, size_t nbytes,
                                       MemoryUse use) {
  // nbytes can be zero here for SharedArrayBuffers.

  MOZ_ASSERT(CurrentThreadCanAccessRuntime(runtime_));
  MOZ_ASSERT(CurrentThreadIsGCFinalizing());

  auto ptr = sharedMemoryUseCounts.lookup(mem);

  MOZ_ASSERT(ptr);
  MOZ_ASSERT(ptr->value().count != 0);
  MOZ_ASSERT(ptr->value().use == use);
  MOZ_ASSERT(ptr->value().nbytes >= nbytes);

  ptr->value().count--;
  if (ptr->value().count == 0) {
    mallocHeapSize.removeBytes(ptr->value().nbytes, true);
    sharedMemoryUseCounts.remove(ptr);
  }
}

template <TrackingKind kind>
void js::TrackedAllocPolicy<kind>::decMemory(size_t nbytes) {
  bool updateRetainedSize = false;
  if constexpr (kind == TrackingKind::Cell) {
    // Only subtract freed cell memory from retained size for cell associations
    // during sweeping.
    JS::GCContext* gcx = TlsGCContext.get();
    updateRetainedSize = gcx->isFinalizing();
  }

  zone_->decNonGCMemory(this, nbytes, MemoryUse::TrackedAllocPolicy,
                        updateRetainedSize);
}

namespace js {
template class TrackedAllocPolicy<TrackingKind::Zone>;
template class TrackedAllocPolicy<TrackingKind::Cell>;
}  // namespace js

JS::Zone::Zone(JSRuntime* rt, Kind kind)
    : ZoneAllocator(rt, kind),
      arenas(this),
      data(nullptr),
      tenuredBigInts(0),
      nurseryAllocatedStrings(0),
      markedStrings(0),
      finalizedStrings(0),
      allocNurseryStrings(true),
      allocNurseryBigInts(true),
      suppressAllocationMetadataBuilder(false),
      pretenuring(this),
      compartments_(),
      crossZoneStringWrappers_(this),
      gcEphemeronEdges_(SystemAllocPolicy(), rt->randomHashCodeScrambler()),
      gcNurseryEphemeronEdges_(SystemAllocPolicy(),
                               rt->randomHashCodeScrambler()),
      shapeZone_(this),
      gcScheduled_(false),
      gcScheduledSaved_(false),
      gcPreserveCode_(false),
      keepPropMapTables_(false),
      wasCollected_(false),
      listNext_(NotOnList),
      keptObjects(this) {
  /* Ensure that there are no vtables to mess us up here. */
  MOZ_ASSERT(reinterpret_cast<JS::shadow::Zone*>(this) ==
             static_cast<JS::shadow::Zone*>(this));
  MOZ_ASSERT_IF(isAtomsZone(), rt->gc.zones().empty());

  updateGCStartThresholds(rt->gc);
}

Zone::~Zone() {
  MOZ_ASSERT_IF(regExps_.ref(), regExps().empty());

  DebugAPI::deleteDebugScriptMap(debugScriptMap);
  js_delete(finalizationObservers_.ref().release());

  MOZ_ASSERT(gcWeakMapList().isEmpty());

  JSRuntime* rt = runtimeFromAnyThread();
  if (this == rt->gc.systemZone) {
    MOZ_ASSERT(isSystemZone());
    rt->gc.systemZone = nullptr;
  }

  js_delete(jitZone_.ref());
}

bool Zone::init() {
  regExps_.ref() = make_unique<RegExpZone>(this);
  return regExps_.ref() && gcEphemeronEdges().init() &&
         gcNurseryEphemeronEdges().init();
}

void Zone::setNeedsIncrementalBarrier(bool needs) {
  needsIncrementalBarrier_ = needs;
}

void Zone::changeGCState(GCState prev, GCState next) {
  MOZ_ASSERT(RuntimeHeapIsBusy());
  MOZ_ASSERT(gcState() == prev);

  // This can be called when barriers have been temporarily disabled by
  // AutoDisableBarriers. In that case, don't update needsIncrementalBarrier_
  // and barriers will be re-enabled by ~AutoDisableBarriers() if necessary.
  bool barriersDisabled = isGCMarking() && !needsIncrementalBarrier();

  gcState_ = next;

  // Update the barriers state when we transition between marking and
  // non-marking states, unless barriers have been disabled.
  if (!barriersDisabled) {
    needsIncrementalBarrier_ = isGCMarking();
  }
}

template <class Pred>
static void EraseIf(js::gc::EphemeronEdgeVector& entries, Pred pred) {
  auto* begin = entries.begin();
  auto* const end = entries.end();

  auto* newEnd = begin;
  for (auto* p = begin; p != end; p++) {
    if (!pred(*p)) {
      *newEnd++ = *p;
    }
  }

  size_t removed = end - newEnd;
  entries.shrinkBy(removed);
}

static void SweepEphemeronEdgesWhileMinorSweeping(
    js::gc::EphemeronEdgeVector& entries) {
  EraseIf(entries, [](js::gc::EphemeronEdge& edge) -> bool {
    return IsAboutToBeFinalizedDuringMinorSweep(&edge.target);
  });
}

void Zone::sweepAfterMinorGC(JSTracer* trc) {
  sweepEphemeronTablesAfterMinorGC();
  crossZoneStringWrappers().sweepAfterMinorGC(trc);

  for (CompartmentsInZoneIter comp(this); !comp.done(); comp.next()) {
    comp->sweepAfterMinorGC(trc);
  }
}

void Zone::sweepEphemeronTablesAfterMinorGC() {
  for (auto r = gcNurseryEphemeronEdges().mutableAll(); !r.empty();
       r.popFront()) {
    // Sweep gcNurseryEphemeronEdges to move live (forwarded) keys to
    // gcEphemeronEdges, scanning through all the entries for such keys to
    // update them.
    //
    // Forwarded and dead keys may also appear in their delegates' entries,
    // so sweep those too (see below.)

    // The tricky case is when the key has a delegate that was already
    // tenured. Then it will be in its compartment's gcEphemeronEdges, but we
    // still need to update the key (which will be in the entries
    // associated with it.)
    gc::Cell* key = r.front().key;
    MOZ_ASSERT(!key->isTenured());
    if (!Nursery::getForwardedPointer(&key)) {
      // Dead nursery cell => discard.
      continue;
    }

    // Key been moved. The value is an array of <color,cell> pairs; update all
    // cells in that array.
    EphemeronEdgeVector& entries = r.front().value;
    SweepEphemeronEdgesWhileMinorSweeping(entries);

    // Live (moved) nursery cell. Append entries to gcEphemeronEdges.
    EphemeronEdgeTable& tenuredEdges = gcEphemeronEdges();
    auto* entry = tenuredEdges.get(key);
    if (!entry) {
      if (!tenuredEdges.put(key, gc::EphemeronEdgeVector())) {
        AutoEnterOOMUnsafeRegion oomUnsafe;
        oomUnsafe.crash("Failed to tenure weak keys entry");
      }
      entry = tenuredEdges.get(key);
    }

    if (!entry->value.appendAll(entries)) {
      AutoEnterOOMUnsafeRegion oomUnsafe;
      oomUnsafe.crash("Failed to tenure weak keys entry");
    }

    // If the key has a delegate, then it will map to a WeakKeyEntryVector
    // containing the key that needs to be updated.

    JSObject* delegate = gc::detail::GetDelegate(key->as<JSObject>());
    if (!delegate) {
      continue;
    }
    MOZ_ASSERT(delegate->isTenured());

    // If delegate was formerly nursery-allocated, we will sweep its entries
    // when we visit its gcNurseryEphemeronEdges (if we haven't already). Note
    // that we don't know the nursery address of the delegate, since the
    // location it was stored in has already been updated.
    //
    // Otherwise, it will be in gcEphemeronEdges and we sweep it here.
    auto* p = delegate->zone()->gcEphemeronEdges().get(delegate);
    if (p) {
      SweepEphemeronEdgesWhileMinorSweeping(p->value);
    }
  }

  if (!gcNurseryEphemeronEdges().clear()) {
    AutoEnterOOMUnsafeRegion oomUnsafe;
    oomUnsafe.crash("OOM while clearing gcNurseryEphemeronEdges.");
  }
}

void Zone::traceWeakCCWEdges(JSTracer* trc) {
  crossZoneStringWrappers().traceWeak(trc);
  for (CompartmentsInZoneIter comp(this); !comp.done(); comp.next()) {
    comp->traceCrossCompartmentObjectWrapperEdges(trc);
  }
}

/* static */
void Zone::fixupAllCrossCompartmentWrappersAfterMovingGC(JSTracer* trc) {
  MOZ_ASSERT(trc->runtime()->gc.isHeapCompacting());

  for (ZonesIter zone(trc->runtime(), WithAtoms); !zone.done(); zone.next()) {
    // Trace the wrapper map to update keys (wrapped values) in other
    // compartments that may have been moved.
    zone->crossZoneStringWrappers().traceWeak(trc);

    for (CompartmentsInZoneIter comp(zone); !comp.done(); comp.next()) {
      comp->fixupCrossCompartmentObjectWrappersAfterMovingGC(trc);
    }
  }
}

void Zone::dropStringWrappersOnGC() {
  MOZ_ASSERT(JS::RuntimeHeapIsCollecting());
  crossZoneStringWrappers().clear();
}

#ifdef JSGC_HASH_TABLE_CHECKS

void Zone::checkAllCrossCompartmentWrappersAfterMovingGC() {
  checkStringWrappersAfterMovingGC();
  for (CompartmentsInZoneIter comp(this); !comp.done(); comp.next()) {
    comp->checkObjectWrappersAfterMovingGC();
  }
}

void Zone::checkStringWrappersAfterMovingGC() {
  for (StringWrapperMap::Enum e(crossZoneStringWrappers()); !e.empty();
       e.popFront()) {
    // Assert that the postbarriers have worked and that nothing is left in the
    // wrapper map that points into the nursery, and that the hash table entries
    // are discoverable.
    auto key = e.front().key();
    CheckGCThingAfterMovingGC(key.get());

    auto ptr = crossZoneStringWrappers().lookup(key);
    MOZ_RELEASE_ASSERT(ptr.found() && &*ptr == &e.front());
  }
}
#endif

void Zone::discardJitCode(JS::GCContext* gcx, const DiscardOptions& options) {
  if (!jitZone()) {
    return;
  }

  if (isPreservingCode()) {
    return;
  }

  if (options.discardJitScripts && options.discardBaselineCode) {
    lastDiscardedCodeTime_ = mozilla::TimeStamp::Now();
  }

  if (options.discardBaselineCode || options.discardJitScripts) {
#ifdef DEBUG
    // Assert no JitScripts are marked as active.
    for (auto iter = cellIter<BaseScript>(); !iter.done(); iter.next()) {
      BaseScript* base = iter.unbarrieredGet();
      if (jit::JitScript* jitScript = base->maybeJitScript()) {
        MOZ_ASSERT(!jitScript->active());
      }
    }
#endif

    // Mark JitScripts on the stack as active.
    jit::MarkActiveJitScripts(this);
  }

  // Invalidate all Ion code in this zone.
  jit::InvalidateAll(gcx, this);

  for (auto base = cellIterUnsafe<BaseScript>(); !base.done(); base.next()) {
    jit::JitScript* jitScript = base->maybeJitScript();
    if (!jitScript) {
      continue;
    }

    JSScript* script = base->asJSScript();
    jit::FinishInvalidation(gcx, script);

    // Discard baseline script if it's not marked as active.
    if (options.discardBaselineCode) {
      if (jitScript->hasBaselineScript() && !jitScript->active()) {
        jit::FinishDiscardBaselineScript(gcx, script);
      }
    }

#ifdef JS_CACHEIR_SPEW
    maybeUpdateWarmUpCount(script);
#endif

    // Warm-up counter for scripts are reset on GC. After discarding code we
    // need to let it warm back up to get information such as which
    // opcodes are setting array holes or accessing getter properties.
    script->resetWarmUpCounterForGC();

    // Try to release the script's JitScript. This should happen after
    // releasing JIT code because we can't do this when the script still has
    // JIT code.
    if (options.discardJitScripts) {
      script->maybeReleaseJitScript(gcx);
      jitScript = script->maybeJitScript();
      if (!jitScript) {
        // Try to discard the ScriptCounts too.
        if (!script->realm()->collectCoverageForDebug() &&
            !gcx->runtime()->profilingScripts) {
          script->destroyScriptCounts();
        }
        continue;
      }
    }

    // If we did not release the JitScript, we need to purge optimized IC
    // stubs because the optimizedStubSpace will be purged below.
    if (options.discardBaselineCode) {
      jitScript->purgeOptimizedStubs(script);
    }

    if (options.resetNurseryAllocSites || options.resetPretenuredAllocSites) {
      jitScript->resetAllocSites(options.resetNurseryAllocSites,
                                 options.resetPretenuredAllocSites);
    }

    // Finally, reset the active flag.
    jitScript->resetActive();
  }

  // Also clear references to jit code from RegExpShared cells at this point.
  // This avoid holding onto ExecutablePools.
  for (auto regExp = cellIterUnsafe<RegExpShared>(); !regExp.done();
       regExp.next()) {
    regExp->discardJitCode();
  }

  /*
   * When scripts contains pointers to nursery things, the store buffer
   * can contain entries that point into the optimized stub space. Since
   * this method can be called outside the context of a GC, this situation
   * could result in us trying to mark invalid store buffer entries.
   *
   * Defer freeing any allocated blocks until after the next minor GC.
   */
  if (options.discardBaselineCode) {
    jitZone()->optimizedStubSpace()->freeAllAfterMinorGC(this);
    jitZone()->purgeIonCacheIRStubInfo();
  }
}

void JS::Zone::resetAllocSitesAndInvalidate(bool resetNurserySites,
                                            bool resetPretenuredSites) {
  MOZ_ASSERT(resetNurserySites || resetPretenuredSites);

  if (!jitZone()) {
    return;
  }

  JSContext* cx = runtime_->mainContextFromOwnThread();
  for (auto base = cellIterUnsafe<BaseScript>(); !base.done(); base.next()) {
    jit::JitScript* jitScript = base->maybeJitScript();
    if (!jitScript) {
      continue;
    }

    if (!jitScript->resetAllocSites(resetNurserySites, resetPretenuredSites)) {
      continue;
    }

    JSScript* script = base->asJSScript();
    CancelOffThreadIonCompile(script);

    if (!script->hasIonScript()) {
      continue;
    }

    jit::Invalidate(cx, script,
                    /* resetUses = */ true,
                    /* cancelOffThread = */ true);
  }
}

void JS::Zone::beforeClearDelegateInternal(JSObject* wrapper,
                                           JSObject* delegate) {
  MOZ_ASSERT(js::gc::detail::GetDelegate(wrapper) == delegate);
  MOZ_ASSERT(needsIncrementalBarrier());
  MOZ_ASSERT(!RuntimeFromMainThreadIsHeapMajorCollecting(this));
  runtimeFromMainThread()->gc.marker().severWeakDelegate(wrapper, delegate);
}

void JS::Zone::afterAddDelegateInternal(JSObject* wrapper) {
  MOZ_ASSERT(!RuntimeFromMainThreadIsHeapMajorCollecting(this));
  JSObject* delegate = js::gc::detail::GetDelegate(wrapper);
  if (delegate) {
    runtimeFromMainThread()->gc.marker().restoreWeakDelegate(wrapper, delegate);
  }
}

#ifdef JSGC_HASH_TABLE_CHECKS
void JS::Zone::checkUniqueIdTableAfterMovingGC() {
  for (auto r = uniqueIds().all(); !r.empty(); r.popFront()) {
    js::gc::CheckGCThingAfterMovingGC(r.front().key());
  }
}
#endif

uint64_t Zone::gcNumber() { return runtimeFromMainThread()->gc.gcNumber(); }

js::jit::JitZone* Zone::createJitZone(JSContext* cx) {
  MOZ_ASSERT(!jitZone_);
  MOZ_ASSERT(cx->runtime()->hasJitRuntime());

  UniquePtr<jit::JitZone> jitZone(cx->new_<js::jit::JitZone>());
  if (!jitZone) {
    return nullptr;
  }

  jitZone_ = jitZone.release();
  return jitZone_;
}

bool Zone::hasMarkedRealms() {
  for (RealmsInZoneIter realm(this); !realm.done(); realm.next()) {
    if (realm->marked()) {
      return true;
    }
  }
  return false;
}

void Zone::notifyObservingDebuggers() {
  AutoAssertNoGC nogc;
  MOZ_ASSERT(JS::RuntimeHeapIsCollecting(),
             "This method should be called during GC.");

  JSRuntime* rt = runtimeFromMainThread();

  for (RealmsInZoneIter realms(this); !realms.done(); realms.next()) {
    GlobalObject* global = realms->unsafeUnbarrieredMaybeGlobal();
    if (!global) {
      continue;
    }

    DebugAPI::notifyParticipatesInGC(global, rt->gc.majorGCCount());
  }
}

bool Zone::isOnList() const { return listNext_ != NotOnList; }

Zone* Zone::nextZone() const {
  MOZ_ASSERT(isOnList());
  return listNext_;
}

void Zone::fixupAfterMovingGC() {
  ZoneAllocator::fixupAfterMovingGC();
  shapeZone().fixupPropMapShapeTableAfterMovingGC();
}

void Zone::purgeAtomCache() {
  atomCache().clearAndCompact();

  // Also purge the dtoa caches so that subsequent lookups populate atom
  // cache too.
  for (RealmsInZoneIter r(this); !r.done(); r.next()) {
    r->dtoaCache.purge();
  }
}

void Zone::addSizeOfIncludingThis(
    mozilla::MallocSizeOf mallocSizeOf, JS::CodeSizes* code, size_t* regexpZone,
    size_t* jitZone, size_t* baselineStubsOptimized, size_t* uniqueIdMap,
    size_t* initialPropMapTable, size_t* shapeTables, size_t* atomsMarkBitmaps,
    size_t* compartmentObjects, size_t* crossCompartmentWrappersTables,
    size_t* compartmentsPrivateData, size_t* scriptCountsMapArg) {
  *regexpZone += regExps().sizeOfIncludingThis(mallocSizeOf);
  if (jitZone_) {
    jitZone_->addSizeOfIncludingThis(mallocSizeOf, code, jitZone,
                                     baselineStubsOptimized);
  }
  *uniqueIdMap += uniqueIds().shallowSizeOfExcludingThis(mallocSizeOf);
  shapeZone().addSizeOfExcludingThis(mallocSizeOf, initialPropMapTable,
                                     shapeTables);
  *atomsMarkBitmaps += markedAtoms().sizeOfExcludingThis(mallocSizeOf);
  *crossCompartmentWrappersTables +=
      crossZoneStringWrappers().sizeOfExcludingThis(mallocSizeOf);

  for (CompartmentsInZoneIter comp(this); !comp.done(); comp.next()) {
    comp->addSizeOfIncludingThis(mallocSizeOf, compartmentObjects,
                                 crossCompartmentWrappersTables,
                                 compartmentsPrivateData);
  }

  if (scriptCountsMap) {
    *scriptCountsMapArg +=
        scriptCountsMap->shallowSizeOfIncludingThis(mallocSizeOf);
    for (auto r = scriptCountsMap->all(); !r.empty(); r.popFront()) {
      *scriptCountsMapArg +=
          r.front().value()->sizeOfIncludingThis(mallocSizeOf);
    }
  }
}

void* ZoneAllocator::onOutOfMemory(js::AllocFunction allocFunc,
                                   arena_id_t arena, size_t nbytes,
                                   void* reallocPtr) {
  if (!js::CurrentThreadCanAccessRuntime(runtime_)) {
    return nullptr;
  }
  // The analysis sees that JSRuntime::onOutOfMemory could report an error,
  // which with a JSErrorInterceptor could GC. But we're passing a null cx (to
  // a default parameter) so the error will not be reported.
  JS::AutoSuppressGCAnalysis suppress;
  return runtimeFromMainThread()->onOutOfMemory(allocFunc, arena, nbytes,
                                                reallocPtr);
}

void ZoneAllocator::reportAllocationOverflow() const {
  js::ReportAllocationOverflow(static_cast<JSContext*>(nullptr));
}

ZoneList::ZoneList() : head(nullptr), tail(nullptr) {}

ZoneList::ZoneList(Zone* zone) : head(zone), tail(zone) {
  MOZ_RELEASE_ASSERT(!zone->isOnList());
  zone->listNext_ = nullptr;
}

ZoneList::~ZoneList() { MOZ_ASSERT(isEmpty()); }

void ZoneList::check() const {
#ifdef DEBUG
  MOZ_ASSERT((head == nullptr) == (tail == nullptr));
  if (!head) {
    return;
  }

  Zone* zone = head;
  for (;;) {
    MOZ_ASSERT(zone && zone->isOnList());
    if (zone == tail) break;
    zone = zone->listNext_;
  }
  MOZ_ASSERT(!zone->listNext_);
#endif
}

bool ZoneList::isEmpty() const { return head == nullptr; }

Zone* ZoneList::front() const {
  MOZ_ASSERT(!isEmpty());
  MOZ_ASSERT(head->isOnList());
  return head;
}

void ZoneList::prepend(Zone* zone) { prependList(ZoneList(zone)); }

void ZoneList::append(Zone* zone) { appendList(ZoneList(zone)); }

void ZoneList::prependList(ZoneList&& other) {
  check();
  other.check();

  if (other.isEmpty()) {
    return;
  }

  MOZ_ASSERT(tail != other.tail);

  if (!isEmpty()) {
    other.tail->listNext_ = head;
  } else {
    tail = other.tail;
  }
  head = other.head;

  other.head = nullptr;
  other.tail = nullptr;
}

void ZoneList::appendList(ZoneList&& other) {
  check();
  other.check();

  if (other.isEmpty()) {
    return;
  }

  MOZ_ASSERT(tail != other.tail);

  if (!isEmpty()) {
    tail->listNext_ = other.head;
  } else {
    head = other.head;
  }
  tail = other.tail;

  other.head = nullptr;
  other.tail = nullptr;
}

Zone* ZoneList::removeFront() {
  MOZ_ASSERT(!isEmpty());
  check();

  Zone* front = head;
  head = head->listNext_;
  if (!head) {
    tail = nullptr;
  }

  front->listNext_ = Zone::NotOnList;

  return front;
}

void ZoneList::clear() {
  while (!isEmpty()) {
    removeFront();
  }
}

JS_PUBLIC_API void JS::shadow::RegisterWeakCache(
    JS::Zone* zone, detail::WeakCacheBase* cachep) {
  zone->registerWeakCache(cachep);
}

void Zone::traceRootsInMajorGC(JSTracer* trc) {
  if (trc->isMarkingTracer() && !isGCMarking()) {
    return;
  }

  // Trace zone script-table roots. See comment below for justification re:
  // calling this only during major (non-nursery) collections.
  traceScriptTableRoots(trc);

  if (FinalizationObservers* observers = finalizationObservers()) {
    observers->traceRoots(trc);
  }
}

void Zone::traceScriptTableRoots(JSTracer* trc) {
  static_assert(std::is_convertible_v<BaseScript*, gc::TenuredCell*>,
                "BaseScript must not be nursery-allocated for script-table "
                "tracing to work");

  // Performance optimization: the script-table keys are JSScripts, which
  // cannot be in the nursery, so we can skip this tracing if we are only in a
  // minor collection. We static-assert this fact above.
  MOZ_ASSERT(!JS::RuntimeHeapIsMinorCollecting());

  // N.B.: the script-table keys are weak *except* in an exceptional case: when
  // then --dump-bytecode command line option or the PCCount JSFriend API is
  // used, then the scripts for all counts must remain alive. We only trace
  // when the `trc->runtime()->profilingScripts` flag is set. This flag is
  // cleared in JSRuntime::destroyRuntime() during shutdown to ensure that
  // scripts are collected before the runtime goes away completely.
  if (scriptCountsMap && trc->runtime()->profilingScripts) {
    for (ScriptCountsMap::Range r = scriptCountsMap->all(); !r.empty();
         r.popFront()) {
      BaseScript* script = r.front().key();
      MOZ_ASSERT(script->hasScriptCounts());
      TraceRoot(trc, &script, "profilingScripts");
    }
  }

  // Trace the debugger's DebugScript weak map.
  if (debugScriptMap) {
    DebugAPI::traceDebugScriptMap(trc, debugScriptMap);
  }
}

void Zone::fixupScriptMapsAfterMovingGC(JSTracer* trc) {
  // Map entries are removed by BaseScript::finalize, but we need to update the
  // script pointers here in case they are moved by the GC.

  if (scriptCountsMap) {
    scriptCountsMap->traceWeak(trc);
  }

  if (scriptLCovMap) {
    scriptLCovMap->traceWeak(trc);
  }

#ifdef MOZ_VTUNE
  if (scriptVTuneIdMap) {
    scriptVTuneIdMap->traceWeak(trc);
  }
#endif

#ifdef JS_CACHEIR_SPEW
  if (scriptFinalWarmUpCountMap) {
    scriptFinalWarmUpCountMap->traceWeak(trc);
  }
#endif
}

#ifdef JSGC_HASH_TABLE_CHECKS
void Zone::checkScriptMapsAfterMovingGC() {
  if (scriptCountsMap) {
    for (auto r = scriptCountsMap->all(); !r.empty(); r.popFront()) {
      BaseScript* script = r.front().key();
      MOZ_ASSERT(script->zone() == this);
      CheckGCThingAfterMovingGC(script);
      auto ptr = scriptCountsMap->lookup(script);
      MOZ_RELEASE_ASSERT(ptr.found() && &*ptr == &r.front());
    }
  }

  if (scriptLCovMap) {
    for (auto r = scriptLCovMap->all(); !r.empty(); r.popFront()) {
      BaseScript* script = r.front().key();
      MOZ_ASSERT(script->zone() == this);
      CheckGCThingAfterMovingGC(script);
      auto ptr = scriptLCovMap->lookup(script);
      MOZ_RELEASE_ASSERT(ptr.found() && &*ptr == &r.front());
    }
  }

#  ifdef MOZ_VTUNE
  if (scriptVTuneIdMap) {
    for (auto r = scriptVTuneIdMap->all(); !r.empty(); r.popFront()) {
      BaseScript* script = r.front().key();
      MOZ_ASSERT(script->zone() == this);
      CheckGCThingAfterMovingGC(script);
      auto ptr = scriptVTuneIdMap->lookup(script);
      MOZ_RELEASE_ASSERT(ptr.found() && &*ptr == &r.front());
    }
  }
#  endif  // MOZ_VTUNE

#  ifdef JS_CACHEIR_SPEW
  if (scriptFinalWarmUpCountMap) {
    for (auto r = scriptFinalWarmUpCountMap->all(); !r.empty(); r.popFront()) {
      BaseScript* script = r.front().key();
      MOZ_ASSERT(script->zone() == this);
      CheckGCThingAfterMovingGC(script);
      auto ptr = scriptFinalWarmUpCountMap->lookup(script);
      MOZ_RELEASE_ASSERT(ptr.found() && &*ptr == &r.front());
    }
  }
#  endif  // JS_CACHEIR_SPEW
}
#endif

void Zone::clearScriptCounts(Realm* realm) {
  if (!scriptCountsMap) {
    return;
  }

  // Clear all hasScriptCounts_ flags of BaseScript, in order to release all
  // ScriptCounts entries of the given realm.
  for (auto i = scriptCountsMap->modIter(); !i.done(); i.next()) {
    BaseScript* script = i.get().key();
    if (script->realm() != realm) {
      continue;
    }
    // We can't destroy the ScriptCounts yet if the script has Baseline code,
    // because Baseline code bakes in pointers to the counters. The ScriptCounts
    // will be destroyed in Zone::discardJitCode when discarding the JitScript.
    if (script->hasBaselineScript()) {
      continue;
    }
    script->clearHasScriptCounts();
    i.remove();
  }
}

void Zone::clearScriptLCov(Realm* realm) {
  if (!scriptLCovMap) {
    return;
  }

  for (auto i = scriptLCovMap->modIter(); !i.done(); i.next()) {
    BaseScript* script = i.get().key();
    if (script->realm() == realm) {
      i.remove();
    }
  }
}

void Zone::clearRootsForShutdownGC() {
  // Finalization callbacks are not called if we're shutting down.
  if (finalizationObservers()) {
    finalizationObservers()->clearRecords();
  }

  clearKeptObjects();
}

void Zone::finishRoots() {
  for (RealmsInZoneIter r(this); !r.done(); r.next()) {
    r->finishRoots();
  }
}

void Zone::traceKeptObjects(JSTracer* trc) { keptObjects.ref().trace(trc); }

bool Zone::keepDuringJob(HandleObject target) {
  return keptObjects.ref().put(target);
}

void Zone::clearKeptObjects() { keptObjects.ref().clear(); }

bool Zone::ensureFinalizationObservers() {
  if (finalizationObservers_.ref()) {
    return true;
  }

  finalizationObservers_ = js::MakeUnique<FinalizationObservers>(this);
  return bool(finalizationObservers_.ref());
}