[heap] Do not process native context list in minor GCs

NativeContexts are always allocated in old space and thus cannot die
or move during minor GCs.

Bug: v8:11708
Change-Id: I01ec7775aa1186d91ca620c464f570f24ac9f215
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3666617Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Commit-Queue: Dominik Inführ <dinfuehr@chromium.org>
Cr-Commit-Position: refs/heads/main@{#80818}

src/heap/heap.cc

@@ -2996,10 +2996,6 @@ void Heap::ProcessAllWeakReferences(WeakObjectRetainer* retainer) {
   ProcessDirtyJSFinalizationRegistries(retainer);
 }
 
-void Heap::ProcessYoungWeakReferences(WeakObjectRetainer* retainer) {
-  ProcessNativeContexts(retainer);
-}
-
 void Heap::ProcessNativeContexts(WeakObjectRetainer* retainer) {
   Object head = VisitWeakList<Context>(this, native_contexts_list(), retainer);
   // Update the head of the list of contexts.

src/heap/heap.h

@@ -1971,7 +1971,6 @@ class Heap {
       ExternalStringTableUpdaterCallback updater_func);
 
   void ProcessAllWeakReferences(WeakObjectRetainer* retainer);
-  void ProcessYoungWeakReferences(WeakObjectRetainer* retainer);
   void ProcessNativeContexts(WeakObjectRetainer* retainer);
   void ProcessAllocationSites(WeakObjectRetainer* retainer);
   void ProcessDirtyJSFinalizationRegistries(WeakObjectRetainer* retainer);

src/heap/mark-compact.cc

@@ -5713,30 +5713,6 @@ class YoungGenerationExternalStringTableCleaner : public RootVisitor {
   MinorMarkCompactCollector::NonAtomicMarkingState* marking_state_;
 };
 
-// Marked young generation objects and all old generation objects will be
-// retained.
-class MinorMarkCompactWeakObjectRetainer : public WeakObjectRetainer {
- public:
-  explicit MinorMarkCompactWeakObjectRetainer(
-      MinorMarkCompactCollector* collector)
-      : marking_state_(collector->non_atomic_marking_state()) {}
-
-  Object RetainAs(Object object) override {
-    HeapObject heap_object = HeapObject::cast(object);
-    if (!Heap::InYoungGeneration(heap_object)) return object;
-
-    // Young generation marking only marks to grey instead of black.
-    DCHECK(!marking_state_->IsBlack(heap_object));
-    if (marking_state_->IsGrey(heap_object)) {
-      return object;
-    }
-    return Object();
-  }
-
- private:
-  MinorMarkCompactCollector::NonAtomicMarkingState* marking_state_;
-};
-
 }  // namespace
 
 void MinorMarkCompactCollector::ClearNonLiveReferences() {
@@ -5750,13 +5726,6 @@ void MinorMarkCompactCollector::ClearNonLiveReferences() {
     heap()->external_string_table_.IterateYoung(&external_visitor);
     heap()->external_string_table_.CleanUpYoung();
   }
-
-  {
-    TRACE_GC(heap()->tracer(), GCTracer::Scope::MINOR_MC_CLEAR_WEAK_LISTS);
-    // Process the weak references.
-    MinorMarkCompactWeakObjectRetainer retainer(this);
-    heap()->ProcessYoungWeakReferences(&retainer);
-  }
 }
 
 void MinorMarkCompactCollector::EvacuatePrologue() {

src/heap/scavenger.cc

@@ -172,21 +172,6 @@ bool IsUnscavengedHeapObjectSlot(Heap* heap, FullObjectSlot p) {
 
 }  // namespace
 
-class ScavengeWeakObjectRetainer : public WeakObjectRetainer {
- public:
-  Object RetainAs(Object object) override {
-    if (!Heap::InFromPage(object)) {
-      return object;
-    }
-
-    MapWord map_word = HeapObject::cast(object).map_word(kRelaxedLoad);
-    if (map_word.IsForwardingAddress()) {
-      return map_word.ToForwardingAddress();
-    }
-    return Object();
-  }
-};
-
 ScavengerCollector::JobTask::JobTask(
     ScavengerCollector* outer,
     std::vector<std::unique_ptr<Scavenger>>* scavengers,
@@ -695,8 +680,6 @@ void Scavenger::Process(JobDelegate* delegate) {
 
 void ScavengerCollector::ProcessWeakReferences(
     EphemeronTableList* ephemeron_table_list) {
-  ScavengeWeakObjectRetainer weak_object_retainer;
-  heap_->ProcessYoungWeakReferences(&weak_object_retainer);
   ClearYoungEphemerons(ephemeron_table_list);
   ClearOldEphemerons();
 }