Bug 1655768 - Part 2: Remove MergeRealms. r=jonco

Differential Revision: https://phabricator.services.mozilla.com/D131374

js/src/gc/ArenaList.h

@@ -322,9 +322,6 @@ class ArenaLists {
 
   MOZ_ALWAYS_INLINE TenuredCell* allocateFromFreeList(AllocKind thingKind);
 
-  /* Moves all arenas from |fromArenaLists| into |this|. */
-  void adoptArenas(ArenaLists* fromArenaLists, bool targetZoneIsCollecting);
-
   inline void checkEmptyFreeLists();
   inline void checkEmptyArenaLists();
   inline void checkEmptyFreeList(AllocKind kind);

js/src/gc/AtomMarking.cpp

@@ -188,12 +188,6 @@ void AtomMarkingRuntime::markAtomValue(JSContext* cx, const Value& value) {
                                        value.isBigInt());
 }
 
-void AtomMarkingRuntime::adoptMarkedAtoms(Zone* target, Zone* source) {
-  MOZ_ASSERT(CurrentThreadCanAccessZone(source));
-  MOZ_ASSERT(CurrentThreadCanAccessZone(target));
-  target->markedAtoms().bitwiseOrWith(source->markedAtoms());
-}
-
 #ifdef DEBUG
 template <typename T>
 bool AtomMarkingRuntime::atomIsMarked(Zone* zone, T* thing) {

js/src/gc/AtomMarking.h

@@ -70,9 +70,6 @@ class AtomMarkingRuntime {
   void markId(JSContext* cx, jsid id);
   void markAtomValue(JSContext* cx, const Value& value);
 
-  // Mark all atoms in |source| as being reachable within |target|.
-  void adoptMarkedAtoms(Zone* target, Zone* source);
-
 #ifdef DEBUG
   // Return whether |thing/id| is in the atom marking bitmap for |zone|.
   template <typename T>

js/src/gc/GC.cpp

@@ -1903,19 +1903,6 @@ void Compartment::sweepRealms(JSFreeOp* fop, bool keepAtleastOne,
   MOZ_ASSERT_IF(destroyingRuntime, realms().empty());
 }
 
-void GCRuntime::deleteEmptyZone(Zone* zone) {
-  MOZ_ASSERT(CurrentThreadCanAccessRuntime(rt));
-  MOZ_ASSERT(zone->compartments().empty());
-  for (auto& i : zones()) {
-    if (i == zone) {
-      zones().erase(&i);
-      zone->destroy(rt->defaultFreeOp());
-      return;
-    }
-  }
-  MOZ_CRASH("Zone not found");
-}
-
 void GCRuntime::sweepZones(JSFreeOp* fop, bool destroyingRuntime) {
   MOZ_ASSERT_IF(destroyingRuntime, numActiveZoneIters == 0);
 
@@ -4204,115 +4191,6 @@ Realm* js::NewRealm(JSContext* cx, JSPrincipals* principals,
   return realm.release();
 }
 
-void gc::MergeRealms(Realm* source, Realm* target) {
-  JSRuntime* rt = source->runtimeFromMainThread();
-  rt->gc.mergeRealms(source, target);
-  rt->gc.maybeTriggerGCAfterAlloc(target->zone());
-  rt->gc.maybeTriggerGCAfterMalloc(target->zone());
-}
-
-void GCRuntime::mergeRealms(Realm* source, Realm* target) {
-  // The source realm must be specifically flagged as mergable.  This
-  // also implies that the realm is not visible to the debugger.
-  //
-  // TODO: Remove
-  MOZ_ASSERT(false);
-  MOZ_ASSERT(source->creationOptions().invisibleToDebugger());
-
-  MOZ_ASSERT(!source->hasBeenEnteredIgnoringJit());
-  MOZ_ASSERT(source->zone()->compartments().length() == 1);
-
-  JSContext* cx = rt->mainContextFromOwnThread();
-
-  MOZ_ASSERT(!source->zone()->wasGCStarted());
-  JS::AutoAssertNoGC nogc(cx);
-
-  AutoTraceSession session(rt);
-
-  // Cleanup tables and other state in the source realm/zone that will be
-  // meaningless after merging into the target realm/zone.
-
-  source->clearTables();
-  source->zone()->clearTables();
-  source->unsetIsDebuggee();
-
-#ifdef DEBUG
-  // Release any relocated arenas which we may be holding on to as they might
-  // be in the source zone
-  releaseHeldRelocatedArenas();
-#endif
-
-  // Fixup realm pointers in source to refer to target, and make sure
-  // type information generations are in sync.
-
-  GlobalObject* global = target->maybeGlobal();
-  MOZ_ASSERT(global);
-  AssertTargetIsNotGray(global);
-
-  for (auto baseShape = source->zone()->cellIterUnsafe<BaseShape>();
-       !baseShape.done(); baseShape.next()) {
-    baseShape->setRealmForMergeRealms(target);
-  }
-
-  // Fixup zone pointers in source's zone to refer to target's zone.
-
-  bool targetZoneIsCollecting = target->zone()->gcState() > Zone::Prepare;
-  for (auto thingKind : AllAllocKinds()) {
-    for (ArenaIter aiter(source->zone(), thingKind); !aiter.done();
-         aiter.next()) {
-      Arena* arena = aiter.get();
-      arena->zone = target->zone();
-      if (MOZ_UNLIKELY(targetZoneIsCollecting)) {
-        // If we are currently collecting the target zone then we must
-        // treat all merged things as if they were allocated during the
-        // collection.
-        for (ArenaCellIter cell(arena); !cell.done(); cell.next()) {
-          MOZ_ASSERT(!cell->isMarkedAny());
-          cell->markBlack();
-        }
-      }
-    }
-  }
-
-  // The source should be the only realm in its zone.
-  for (RealmsInZoneIter r(source->zone()); !r.done(); r.next()) {
-    MOZ_ASSERT(r.get() == source);
-  }
-
-  // Merge the allocator, stats and UIDs in source's zone into target's zone.
-  target->zone()->arenas.adoptArenas(&source->zone()->arenas,
-                                     targetZoneIsCollecting);
-  target->zone()->addTenuredAllocsSinceMinorGC(
-      source->zone()->getAndResetTenuredAllocsSinceMinorGC());
-  target->zone()->gcHeapSize.adopt(source->zone()->gcHeapSize);
-  target->zone()->adoptUniqueIds(source->zone());
-  target->zone()->adoptMallocBytes(source->zone());
-
-  // Atoms which are marked in source's zone are now marked in target's zone.
-  atomMarking.adoptMarkedAtoms(target->zone(), source->zone());
-
-  // The source Realm is a parse-only realm and should not have collected any
-  // zone-tracked metadata.
-  Zone* sourceZone = source->zone();
-  MOZ_ASSERT(!sourceZone->scriptLCovMap);
-  MOZ_ASSERT(!sourceZone->scriptCountsMap);
-  MOZ_ASSERT(!sourceZone->debugScriptMap);
-#ifdef MOZ_VTUNE
-  MOZ_ASSERT(!sourceZone->scriptVTuneIdMap);
-#endif
-#ifdef JS_CACHEIR_SPEW
-  MOZ_ASSERT(!sourceZone->scriptFinalWarmUpCountMap);
-#endif
-
-  // The source realm is now completely empty, and is the only realm in its
-  // compartment, which is the only compartment in its zone. Delete realm,
-  // compartment and zone without waiting for this to be cleaned up by a full
-  // GC.
-
-  sourceZone->deleteEmptyCompartment(source->compartment());
-  deleteEmptyZone(sourceZone);
-}
-
 void GCRuntime::runDebugGC() {
 #ifdef JS_GC_ZEAL
   if (rt->mainContextFromOwnThread()->suppressGC) {
@@ -4398,49 +4276,6 @@ void GCRuntime::setDeterministic(bool enabled) {
 }
 #endif
 
-void ArenaLists::adoptArenas(ArenaLists* fromArenaLists,
-                             bool targetZoneIsCollecting) {
-  // GC may be active so take the lock here so we can mutate the arena lists.
-  AutoLockGC lock(runtime());
-
-  fromArenaLists->clearFreeLists();
-
-  for (auto thingKind : AllAllocKinds()) {
-    MOZ_ASSERT(fromArenaLists->concurrentUse(thingKind) == ConcurrentUse::None);
-    ArenaList* fromList = &fromArenaLists->arenaList(thingKind);
-    ArenaList* toList = &arenaList(thingKind);
-    fromList->check();
-    toList->check();
-    Arena* next;
-    for (Arena* fromArena = fromList->head(); fromArena; fromArena = next) {
-      // Copy fromArena->next before releasing/reinserting.
-      next = fromArena->next;
-
-#ifdef DEBUG
-      MOZ_ASSERT(!fromArena->isEmpty());
-      if (targetZoneIsCollecting) {
-        fromArena->checkAllCellsMarkedBlack();
-      } else {
-        fromArena->checkNoMarkedCells();
-      }
-#endif
-
-      // If the target zone is being collected then we need to add the
-      // arenas before the cursor because the collector assumes that the
-      // cursor is always at the end of the list. This has the side-effect
-      // of preventing allocation into any non-full arenas until the end
-      // of the next GC.
-      if (targetZoneIsCollecting) {
-        toList->insertBeforeCursor(fromArena);
-      } else {
-        toList->insertAtCursor(fromArena);
-      }
-    }
-    fromList->clear();
-    toList->check();
-  }
-}
-
 #ifdef DEBUG
 
 AutoAssertNoNurseryAlloc::AutoAssertNoNurseryAlloc() {

js/src/gc/GC.h

@@ -110,12 +110,6 @@ void FinishGC(JSContext* cx, JS::GCReason = JS::GCReason::FINISH_GC);
 
 void WaitForBackgroundTasks(JSContext* cx);
 
-/*
- * Merge all contents of source into target. This can only be used if source is
- * the only realm in its zone.
- */
-void MergeRealms(JS::Realm* source, JS::Realm* target);
-
 enum VerifierType { PreBarrierVerifier };
 
 #ifdef JS_GC_ZEAL

js/src/gc/GCRuntime.h

@@ -610,8 +610,6 @@ class GCRuntime {
   void updateHelperThreadCount();
   size_t parallelWorkerCount() const;
 
-  void mergeRealms(JS::Realm* source, JS::Realm* target);
-
   // WeakRefs
   bool registerWeakRef(HandleObject target, HandleObject weakRef);
   bool unregisterWeakRefWrapper(JSObject* wrapper);
@@ -628,9 +626,6 @@ class GCRuntime {
   void updateGCThresholdsAfterCollection(const AutoLockGC& lock);
   void updateAllGCStartThresholds(const AutoLockGC& lock);
 
-  // Delete an empty zone after its contents have been merged.
-  void deleteEmptyZone(Zone* zone);
-
   // For ArenaLists::allocateFromArena()
   friend class ArenaLists;
   TenuredChunk* pickChunk(AutoLockGCBgAlloc& lock);

js/src/gc/Scheduling.h

@@ -784,15 +784,6 @@ class HeapSize {
       parent_->removeBytes(nbytes, wasSwept);
     }
   }
-
-  /* Pair to adoptArenas. Adopts the attendant usage statistics. */
-  void adopt(HeapSize& source) {
-    // Skip retainedBytes_: we never adopt zones that are currently being
-    // collected.
-    bytes_ += source.bytes_;
-    source.retainedBytes_ = 0;
-    source.bytes_ = 0;
-  }
 };
 
 // Heap size thresholds used to trigger GC. This is an abstract base class for

js/src/gc/Zone-inl.h

@@ -102,16 +102,4 @@ inline void JS::Zone::removeUniqueId(js::gc::Cell* cell) {
   uniqueIds().remove(cell);
 }
 
-inline void JS::Zone::adoptUniqueIds(JS::Zone* source) {
-  js::AutoEnterOOMUnsafeRegion oomUnsafe;
-  for (js::gc::UniqueIdMap::Enum e(source->uniqueIds()); !e.empty();
-       e.popFront()) {
-    MOZ_ASSERT(!uniqueIds().has(e.front().key()));
-    if (!uniqueIds().put(e.front().key(), e.front().value())) {
-      oomUnsafe.crash("failed to transfer unique ids from off-thread");
-    }
-  }
-  source->uniqueIds().clear();
-}
-
 #endif  // gc_Zone_inl_h

js/src/gc/Zone.cpp

@@ -591,12 +591,6 @@ Zone* Zone::nextZone() const {
   return listNext_;
 }
 
-void Zone::clearTables() {
-  MOZ_ASSERT(regExps().empty());
-
-  shapeZone().clearTables(runtimeFromMainThread()->defaultFreeOp());
-}
-
 void Zone::fixupAfterMovingGC() {
   ZoneAllocator::fixupAfterMovingGC();
   shapeZone().fixupPropMapShapeTableAfterMovingGC();
@@ -615,22 +609,6 @@ bool Zone::addRttValueObject(JSContext* cx, HandleObject obj) {
   return true;
 }
 
-void Zone::deleteEmptyCompartment(JS::Compartment* comp) {
-  MOZ_ASSERT(comp->zone() == this);
-  arenas.checkEmptyArenaLists();
-
-  MOZ_ASSERT(compartments().length() == 1);
-  MOZ_ASSERT(compartments()[0] == comp);
-  MOZ_ASSERT(comp->realms().length() == 1);
-
-  Realm* realm = comp->realms()[0];
-  JSFreeOp* fop = runtimeFromMainThread()->defaultFreeOp();
-  realm->destroy(fop);
-  comp->destroy(fop);
-
-  compartments().clear();
-}
-
 void Zone::purgeAtomCache() {
   atomCache().clearAndCompact();
 

js/src/gc/Zone.h

@@ -456,8 +456,6 @@ class Zone : public js::ZoneAllocator, public js::gc::GraphNodeBase<JS::Zone> {
 
   void notifyObservingDebuggers();
 
-  void clearTables();
-
   void addTenuredAllocsSinceMinorGC(uint32_t allocs) {
     tenuredAllocsSinceMinorGC_ += allocs;
   }
@@ -587,16 +585,9 @@ class Zone : public js::ZoneAllocator, public js::gc::GraphNodeBase<JS::Zone> {
   // Remove any unique id associated with this Cell.
   void removeUniqueId(js::gc::Cell* cell);
 
-  // When finished parsing off-thread, transfer any UIDs we created in the
-  // off-thread zone into the target zone.
-  void adoptUniqueIds(JS::Zone* source);
-
   bool keepPropMapTables() const { return keepPropMapTables_; }
   void setKeepPropMapTables(bool b) { keepPropMapTables_ = b; }
 
-  // Delete an empty compartment after its contents have been merged.
-  void deleteEmptyCompartment(JS::Compartment* comp);
-
   void clearRootsForShutdownGC();
   void finishRoots();
 

js/src/gc/ZoneAllocator.h

@@ -57,14 +57,6 @@ class ZoneAllocator : public JS::shadow::Zone,
                                     void* reallocPtr = nullptr);
   void reportAllocationOverflow() const;
 
-  void adoptMallocBytes(ZoneAllocator* other) {
-    mallocHeapSize.adopt(other->mallocHeapSize);
-    jitHeapSize.adopt(other->jitHeapSize);
-#ifdef DEBUG
-    mallocTracker.adopt(other->mallocTracker);
-#endif
-  }
-
   void updateMemoryCountersOnGCStart();
   void updateGCStartThresholds(gc::GCRuntime& gc, const js::AutoLockGC& lock);
   void setGCSliceThresholds(gc::GCRuntime& gc);

js/src/vm/CodeCoverage.cpp

@@ -593,12 +593,7 @@ bool InitScriptCoverage(JSContext* cx, JSScript* script) {
   MOZ_ASSERT(script->hasBytecode(),
              "Only initialize coverage data for fully initialized scripts.");
 
-  // Don't allocate LCovSource if we on helper thread since we will have our
-  // realm migrated. The 'GCRunime::mergeRealms' code will do this
-  // initialization.
-  if (cx->isHelperThreadContext()) {
-    return true;
-  }
+  MOZ_ASSERT(!cx->isHelperThreadContext());
 
   const char* filename = script->filename();
   if (!filename) {

js/src/vm/Realm.cpp

@@ -399,20 +399,6 @@ void Realm::purge() {
   promiseLookup.purge();
 }
 
-void Realm::clearTables() {
-  global_.unbarrieredGet()->releaseData(runtime_->defaultFreeOp());
-  global_.set(nullptr);
-
-  // No scripts should have run in this realm. This is used when merging
-  // a realm that has been used off thread into another realm and zone.
-  compartment()->assertNoCrossCompartmentWrappers();
-  MOZ_ASSERT(!jitRealm_);
-  MOZ_ASSERT(!debugEnvs_);
-  MOZ_ASSERT(objects_.enumerators->next() == objects_.enumerators);
-
-  savedStacks_.clear();
-}
-
 // Check to see if this individual realm is recording allocations. Debuggers or
 // runtimes can try and record allocations, so this method can check to see if
 // any initialization is needed.

js/src/vm/Realm.h

@@ -442,7 +442,6 @@ class JS::Realm : public JS::shadow::Realm {
 
   [[nodiscard]] bool init(JSContext* cx, JSPrincipals* principals);
   void destroy(JSFreeOp* fop);
-  void clearTables();
 
   void addSizeOfIncludingThis(mozilla::MallocSizeOf mallocSizeOf,
                               size_t* realmObject, size_t* realmTables,

js/src/vm/Shape.h

@@ -215,9 +215,6 @@ class BaseShape : public gc::TenuredCellWithNonGCPointer<const JSClass> {
 
   TaggedProto proto() const { return proto_; }
 
-  void setRealmForMergeRealms(JS::Realm* realm) { realm_ = realm; }
-  void setProtoForMergeRealms(TaggedProto proto) { proto_ = proto; }
-
   /*
    * Lookup base shapes from the zone's baseShapes table, adding if not
    * already found.

js/src/vm/ShapeZone.cpp

@@ -82,14 +82,6 @@ ShapeZone::ShapeZone(Zone* zone)
       initialShapes(zone),
       propMapShapes(zone) {}
 
-void ShapeZone::clearTables(JSFreeOp* fop) {
-  baseShapes.clear();
-  initialPropMaps.clear();
-  initialShapes.clear();
-  propMapShapes.clear();
-  purgeShapeCaches(fop);
-}
-
 void ShapeZone::purgeShapeCaches(JSFreeOp* fop) {
   for (Shape* shape : shapesWithCache) {
     MaybeForwarded(shape)->purgeCache(fop);

js/src/vm/ShapeZone.h

@@ -160,7 +160,6 @@ struct ShapeZone {
 
   explicit ShapeZone(Zone* zone);
 
-  void clearTables(JSFreeOp* fop);
   void purgeShapeCaches(JSFreeOp* fop);
 
   void addSizeOfExcludingThis(mozilla::MallocSizeOf mallocSizeOf,