Commit 8b44ca7a authored by Jon Coppeard's avatar Jon Coppeard
Browse files

Bug 1730534 - Part 3: Add an iterator for JSHolderMap r=mccr8 

This adds an iterator over JSHolderMap and replaces use of the ForEach method
with it.

Differential Revision: https://phabricator.services.mozilla.com/D125429
parent 283daa19

xpcom/base/CycleCollectedJSRuntime.cpp

+53 −46
Original line number Diff line number Diff line
@@ -498,35 +498,37 @@ void JSHolderMap::EntryVectorIter::Settle() { 
  }

}



JSHolderMap::JSHolderMap() : mJSHolderMap(256) {}



template <typename F>

inline void JSHolderMap::ForEach(F&& f, WhichHolders aWhich) {

  // Multi-zone JS holders must always be considered.

  for (EntryVectorIter entry(*this, mAnyZoneJSHolders); !entry.Done();

       entry.Next()) {

    f(entry->mHolder, entry->mTracer, nullptr);

inline JSHolderMap::Iter::Iter(JSHolderMap& aMap, WhichHolders aWhich)

    : mHolderMap(aMap), mIter(aMap, aMap.mAnyZoneJSHolders) {

  // Populate vector of zones to iterate after the any-zone holders.

  for (auto i = aMap.mPerZoneJSHolders.iter(); !i.done(); i.next()) {

    JS::Zone* zone = i.get().key();

    if (aWhich == AllHolders || JS::NeedGrayRootsForZone(i.get().key())) {

      MOZ_ALWAYS_TRUE(mZones.append(zone));

    }

  }



  for (auto i = mPerZoneJSHolders.modIter(); !i.done(); i.next()) {

    if (aWhich == HoldersRequiredForGrayMarking &&

        !JS::NeedGrayRootsForZone(i.get().key())) {

      continue;

  Settle();

}



    JS::Zone* zone = i.get().key();

    EntryVector* holders = i.get().value().get();

    for (EntryVectorIter entry(*this, *holders); !entry.Done(); entry.Next()) {

      MOZ_ASSERT(entry->mZone == zone);

      f(entry->mHolder, entry->mTracer, zone);

void JSHolderMap::Iter::Settle() {

  while (mIter.Done()) {

    if (mZone && mIter.Vector().IsEmpty()) {

      mHolderMap.mPerZoneJSHolders.remove(mZone);

    }



    if (holders->IsEmpty()) {

      i.remove();

    if (mZones.empty()) {

      break;

    }



    mZone = mZones.popCopy();

    EntryVector& vector = *mHolderMap.mPerZoneJSHolders.lookup(mZone)->value();

    new (&mIter) EntryVectorIter(mHolderMap, vector);

  }

}



JSHolderMap::JSHolderMap() : mJSHolderMap(256) {}



bool JSHolderMap::RemoveEntry(EntryVector& aJSHolders, Entry* aEntry) {

  MOZ_ASSERT(aEntry);

  MOZ_ASSERT(!aEntry->mHolder);
@@ -765,8 +767,9 @@ size_t CycleCollectedJSRuntime::SizeOfExcludingThis( 
}



void CycleCollectedJSRuntime::UnmarkSkippableJSHolders() {

  mJSHolders.ForEach([](void* holder, nsScriptObjectTracer* tracer,

                        JS::Zone* zone) { tracer->CanSkip(holder, true); });

  for (JSHolderMap::Iter entry(mJSHolders); !entry.Done(); entry.Next()) {

    entry->mTracer->CanSkip(entry->mHolder, true);

  }

}



void CycleCollectedJSRuntime::DescribeGCThing(
@@ -949,8 +952,10 @@ void CycleCollectedJSRuntime::TraverseNativeRoots( 
  // would hurt to do this after the JS holders.

  TraverseAdditionalNativeRoots(aCb);



  mJSHolders.ForEach(

      [&aCb](void* holder, nsScriptObjectTracer* tracer, JS::Zone* zone) {

  for (JSHolderMap::Iter entry(mJSHolders); !entry.Done(); entry.Next()) {

    void* holder = entry->mHolder;

    nsScriptObjectTracer* tracer = entry->mTracer;



    bool noteRoot = false;

    if (MOZ_UNLIKELY(aCb.WantAllTraces())) {

      noteRoot = true;
@@ -963,7 +968,7 @@ void CycleCollectedJSRuntime::TraverseNativeRoots( 
    if (noteRoot) {

      aCb.NoteNativeRoot(holder, tracer);

    }

      });

  }

}



/* static */
@@ -1398,19 +1403,21 @@ void CycleCollectedJSRuntime::TraceNativeGrayRoots( 
  TraceAdditionalNativeGrayRoots(aTracer);



  bool checkSingleZoneHolders = ShouldCheckSingleZoneHolders();

  mJSHolders.ForEach(

      [aTracer, checkSingleZoneHolders](

          void* holder, nsScriptObjectTracer* tracer, JS::Zone* zone) {

  for (JSHolderMap::Iter entry(mJSHolders, aWhich); !entry.Done();

       entry.Next()) {

    void* holder = entry->mHolder;

    nsScriptObjectTracer* tracer = entry->mTracer;



#ifdef CHECK_SINGLE_ZONE_JS_HOLDERS

    if (checkSingleZoneHolders && !tracer->IsMultiZoneJSHolder()) {

          CheckHolderIsSingleZone(holder, tracer, zone);

      CheckHolderIsSingleZone(holder, tracer, entry.Zone());

    }

#else

    Unused << checkSingleZoneHolders;

#endif



    tracer->Trace(holder, JsGcTracer(), aTracer);

      },

      aWhich);

  }

}



void CycleCollectedJSRuntime::AddJSHolder(void* aHolder,

xpcom/base/CycleCollectedJSRuntime.h

+27 −4
Original line number Diff line number Diff line
@@ -90,11 +90,9 @@ class JSHolderMap { 
 public:

  enum WhichHolders { AllHolders, HoldersRequiredForGrayMarking };



  JSHolderMap();

  class Iter;



  // Call functor |f| for each holder.

  template <typename F>

  void ForEach(F&& f, WhichHolders aWhich = AllHolders);

  JSHolderMap();



  bool Has(void* aHolder) const;

  nsScriptObjectTracer* Get(void* aHolder) const;
@@ -172,6 +170,31 @@ class JSHolderMap::EntryVectorIter { 
  EntryVector::IterImpl mIter;

};



class JSHolderMap::Iter {

 public:

  explicit Iter(JSHolderMap& aMap, WhichHolders aWhich = AllHolders);



  bool Done() const { return mIter.Done(); }

  const Entry& Get() const { return mIter.Get(); }

  void Next() {

    mIter.Next();

    Settle();

  }



  operator const Entry*() const { return &Get(); }

  const Entry* operator->() const { return &Get(); }



  JS::Zone* Zone() const { return mZone; }



 private:

  void Settle();



  JSHolderMap& mHolderMap;

  Vector<JS::Zone*, 1, InfallibleAllocPolicy> mZones;

  JS::Zone* mZone = nullptr;

  EntryVectorIter mIter;

};



class CycleCollectedJSRuntime {

  friend class JSGCThingParticipant;

  friend class JSZoneParticipant;