Cleaned up the weak lists hanging off the heap a bit.

 * Route all access to the 3 weak lists through getters/setters.

 * Removed superfluous visiting already done by ProcessWeakReferences.

R=mstarzinger@chromium.org

Review URL: https://codereview.chromium.org/273653006

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@21207 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/heap.cc

@@ -144,9 +144,9 @@ Heap::Heap()
   ASSERT(MB >= Page::kPageSize);
 
   memset(roots_, 0, sizeof(roots_[0]) * kRootListLength);
-  native_contexts_list_ = NULL;
-  array_buffers_list_ = Smi::FromInt(0);
-  allocation_sites_list_ = Smi::FromInt(0);
+  set_native_contexts_list(NULL);
+  set_array_buffers_list(Smi::FromInt(0));
+  set_allocation_sites_list(Smi::FromInt(0));
   // Put a dummy entry in the remembered pages so we can find the list the
   // minidump even if there are no real unmapped pages.
   RememberUnmappedPage(NULL, false);
@@ -962,7 +962,7 @@ void Heap::EnsureFromSpaceIsCommitted() {
 void Heap::ClearJSFunctionResultCaches() {
   if (isolate_->bootstrapper()->IsActive()) return;
 
-  Object* context = native_contexts_list_;
+  Object* context = native_contexts_list();
   while (!context->IsUndefined()) {
     // Get the caches for this context. GC can happen when the context
     // is not fully initialized, so the caches can be undefined.
@@ -988,7 +988,7 @@ void Heap::ClearNormalizedMapCaches() {
     return;
   }
 
-  Object* context = native_contexts_list_;
+  Object* context = native_contexts_list();
   while (!context->IsUndefined()) {
     // GC can happen when the context is not fully initialized,
     // so the cache can be undefined.
@@ -1569,9 +1569,6 @@ void Heap::Scavenge() {
     collector->code_flusher()->IteratePointersToFromSpace(&scavenge_visitor);
   }
 
-  // Scavenge object reachable from the native contexts list directly.
-  scavenge_visitor.VisitPointer(BitCast<Object**>(&native_contexts_list_));
-
   new_space_front = DoScavenge(&scavenge_visitor, new_space_front);
 
   while (isolate()->global_handles()->IterateObjectGroups(
@@ -1704,7 +1701,7 @@ void Heap::ProcessNativeContexts(WeakObjectRetainer* retainer,
       VisitWeakList<Context>(
           this, native_contexts_list(), retainer, record_slots);
   // Update the head of the list of contexts.
-  native_contexts_list_ = head;
+  set_native_contexts_list(head);
 }
 
 
@@ -1725,7 +1722,7 @@ void Heap::TearDownArrayBuffers() {
     Runtime::FreeArrayBuffer(isolate(), buffer);
     o = buffer->weak_next();
   }
-  array_buffers_list_ = undefined;
+  set_array_buffers_list(undefined);
 }
 
 
@@ -5283,9 +5280,9 @@ bool Heap::CreateHeapObjects() {
   CreateInitialObjects();
   CHECK_EQ(0, gc_count_);
 
-  native_contexts_list_ = undefined_value();
-  array_buffers_list_ = undefined_value();
-  allocation_sites_list_ = undefined_value();
+  set_native_contexts_list(undefined_value());
+  set_array_buffers_list(undefined_value());
+  set_allocation_sites_list(undefined_value());
   weak_object_to_code_table_ = undefined_value();
   return true;
 }

src/heap.h

@@ -833,17 +833,19 @@ class Heap {
   void set_native_contexts_list(Object* object) {
     native_contexts_list_ = object;
   }
-  Object* native_contexts_list() { return native_contexts_list_; }
+  Object* native_contexts_list() const { return native_contexts_list_; }
 
   void set_array_buffers_list(Object* object) {
     array_buffers_list_ = object;
   }
-  Object* array_buffers_list() { return array_buffers_list_; }
+  Object* array_buffers_list() const { return array_buffers_list_; }
 
   void set_allocation_sites_list(Object* object) {
     allocation_sites_list_ = object;
   }
   Object* allocation_sites_list() { return allocation_sites_list_; }
+
+  // Used in CreateAllocationSiteStub and the (de)serializer.
   Object** allocation_sites_list_address() { return &allocation_sites_list_; }
 
   Object* weak_object_to_code_table() { return weak_object_to_code_table_; }
@@ -936,11 +938,6 @@ class Heap {
     return reinterpret_cast<Address*>(&roots_[kStoreBufferTopRootIndex]);
   }
 
-  // Get address of native contexts list for serialization support.
-  Object** native_contexts_list_address() {
-    return &native_contexts_list_;
-  }
-
 #ifdef VERIFY_HEAP
   // Verify the heap is in its normal state before or after a GC.
   void Verify();

src/mark-compact.cc

@@ -2483,7 +2483,7 @@ void MarkCompactCollector::AfterMarking() {
 
 
 void MarkCompactCollector::ProcessMapCaches() {
-  Object* raw_context = heap()->native_contexts_list_;
+  Object* raw_context = heap()->native_contexts_list();
   while (raw_context != heap()->undefined_value()) {
     Context* context = reinterpret_cast<Context*>(raw_context);
     if (IsMarked(context)) {
@@ -3642,9 +3642,6 @@ void MarkCompactCollector::EvacuateNewSpaceAndCandidates() {
     }
   }
 
-  // Update the head of the native contexts list in the heap.
-  updating_visitor.VisitPointer(heap_->native_contexts_list_address());
-
   heap_->string_table()->Iterate(&updating_visitor);
   updating_visitor.VisitPointer(heap_->weak_object_to_code_table_address());
   if (heap_->weak_object_to_code_table()->IsHashTable()) {