Reland "Keep track of array buffers in new space separately"

src/heap/heap.cc

Index: src/heap/heap.cc
diff --git a/src/heap/heap.cc b/src/heap/heap.cc
index bc46cc2cff46d51d2ebaed81bce29d7476d25560..6425224fc0558b5d0eda69729ad717aeef973a5f 100644
--- a/src/heap/heap.cc
+++ b/src/heap/heap.cc
@@ -1623,6 +1623,8 @@ void Heap::Scavenge() {
 
   SelectScavengingVisitorsTable();
 
+  PrepareArrayBufferDiscoveryInNewSpace();
+
   // Flip the semispaces.  After flipping, to space is empty, from space has
   // live objects.
   new_space_.Flip();
@@ -1704,6 +1706,8 @@ void Heap::Scavenge() {
   new_space_.LowerInlineAllocationLimit(
       new_space_.inline_allocation_limit_step());
 
+  FreeDeadArrayBuffers(true);
+
   // Update how much has survived scavenge.
   IncrementYoungSurvivorsCounter(static_cast<int>(
       (PromotedSpaceSizeOfObjects() - survived_watermark) + new_space_.Size()));
@@ -1797,46 +1801,122 @@ void Heap::ProcessNativeContexts(WeakObjectRetainer* retainer) {
 }
 
 
-void Heap::RegisterNewArrayBuffer(void* data, size_t length) {
+void Heap::RegisterNewArrayBufferHelper(std::map<void*, size_t>& live_buffers,
+                                        void* data, size_t length) {
+  live_buffers[data] = length;
+}
+
+
+void Heap::UnregisterArrayBufferHelper(
+    std::map<void*, size_t>& live_buffers,
+    std::map<void*, size_t>& not_yet_discovered_buffers, void* data) {
+  DCHECK(live_buffers.count(data) > 0);
+  live_buffers.erase(data);
+  not_yet_discovered_buffers.erase(data);
+}
+
+
+void Heap::RegisterLiveArrayBufferHelper(
+    std::map<void*, size_t>& not_yet_discovered_buffers, void* data) {
+  not_yet_discovered_buffers.erase(data);
+}
+
+
+size_t Heap::FreeDeadArrayBuffersHelper(
+    Isolate* isolate, std::map<void*, size_t>& live_buffers,
+    std::map<void*, size_t>& not_yet_discovered_buffers) {
+  size_t freed_memory = 0;
+  for (auto buffer = not_yet_discovered_buffers.begin();
+       buffer != not_yet_discovered_buffers.end(); ++buffer) {
+    isolate->array_buffer_allocator()->Free(buffer->first, buffer->second);
+    freed_memory += buffer->second;
+    live_buffers.erase(buffer->first);
+  }
+  not_yet_discovered_buffers = live_buffers;
+  return freed_memory;
+}
+
+
+void Heap::TearDownArrayBuffersHelper(
+    Isolate* isolate, std::map<void*, size_t>& live_buffers,
+    std::map<void*, size_t>& not_yet_discovered_buffers) {
+  for (auto buffer = live_buffers.begin(); buffer != live_buffers.end();
+       ++buffer) {
+    isolate->array_buffer_allocator()->Free(buffer->first, buffer->second);
+  }
+  live_buffers.clear();
+  not_yet_discovered_buffers.clear();
+}
+
+
+void Heap::RegisterNewArrayBuffer(bool in_new_space, void* data,
+                                  size_t length) {
   if (!data) return;
-  live_array_buffers_[data] = length;
+  RegisterNewArrayBufferHelper(
+      in_new_space ? live_new_array_buffers_ : live_array_buffers_, data,
+      length);
   reinterpret_cast<v8::Isolate*>(isolate_)
       ->AdjustAmountOfExternalAllocatedMemory(length);
 }
 
 
-void Heap::UnregisterArrayBuffer(void* data) {
+void Heap::UnregisterArrayBuffer(bool in_new_space, void* data) {
   if (!data) return;
-  DCHECK(live_array_buffers_.count(data) > 0);
-  live_array_buffers_.erase(data);
-  not_yet_discovered_array_buffers_.erase(data);
+  UnregisterArrayBufferHelper(
+      in_new_space ? live_new_array_buffers_ : live_array_buffers_,
+      in_new_space ? not_yet_discovered_new_array_buffers_
+                   : not_yet_discovered_array_buffers_,
+      data);
 }
 
 
-void Heap::RegisterLiveArrayBuffer(void* data) {
-  not_yet_discovered_array_buffers_.erase(data);
+void Heap::RegisterLiveArrayBuffer(bool in_new_space, void* data) {
+  // ArrayBuffer might be in the middle of being constructed.
+  if (data == undefined_value()) return;
+  RegisterLiveArrayBufferHelper(in_new_space
+                                    ? not_yet_discovered_new_array_buffers_
+                                    : not_yet_discovered_array_buffers_,
+                                data);
 }
 
 
-void Heap::FreeDeadArrayBuffers() {
-  for (auto buffer = not_yet_discovered_array_buffers_.begin();
-       buffer != not_yet_discovered_array_buffers_.end(); ++buffer) {
-    isolate_->array_buffer_allocator()->Free(buffer->first, buffer->second);
-    // Don't use the API method here since this could trigger another GC.
-    amount_of_external_allocated_memory_ -= buffer->second;
-    live_array_buffers_.erase(buffer->first);
+void Heap::FreeDeadArrayBuffers(bool in_new_space) {
+  size_t freed_memory = FreeDeadArrayBuffersHelper(
+      isolate_, in_new_space ? live_new_array_buffers_ : live_array_buffers_,
+      in_new_space ? not_yet_discovered_new_array_buffers_
+                   : not_yet_discovered_array_buffers_);
+  if (freed_memory) {
+    reinterpret_cast<v8::Isolate*>(isolate_)
+        ->AdjustAmountOfExternalAllocatedMemory(
+            -static_cast<int64_t>(freed_memory));
   }
-  not_yet_discovered_array_buffers_ = live_array_buffers_;
 }
 
 
 void Heap::TearDownArrayBuffers() {
-  for (auto buffer = live_array_buffers_.begin();
-       buffer != live_array_buffers_.end(); ++buffer) {
-    isolate_->array_buffer_allocator()->Free(buffer->first, buffer->second);
-  }
-  live_array_buffers_.clear();
-  not_yet_discovered_array_buffers_.clear();
+  TearDownArrayBuffersHelper(isolate_, live_array_buffers_,
+                             not_yet_discovered_array_buffers_);
+  TearDownArrayBuffersHelper(isolate_, live_new_array_buffers_,
+                             not_yet_discovered_new_array_buffers_);
+}
+
+
+void Heap::PrepareArrayBufferDiscoveryInNewSpace() {
+  not_yet_discovered_new_array_buffers_ = live_new_array_buffers_;
+}
+
+
+void Heap::PromoteArrayBuffer(Object* obj) {
+  JSArrayBuffer* buffer = JSArrayBuffer::cast(obj);
+  if (buffer->is_external()) return;
+  void* data = buffer->backing_store();
+  if (!data) return;
+  // ArrayBuffer might be in the middle of being constructed.
+  if (data == undefined_value()) return;
+  DCHECK(live_new_array_buffers_.count(data) > 0);
+  live_array_buffers_[data] = live_new_array_buffers_[data];
+  live_new_array_buffers_.erase(data);
+  not_yet_discovered_new_array_buffers_.erase(data);
 }
 
 
@@ -2089,6 +2169,7 @@ class ScavengingVisitor : public StaticVisitorBase {
     table_.Register(kVisitFixedDoubleArray, &EvacuateFixedDoubleArray);
     table_.Register(kVisitFixedTypedArray, &EvacuateFixedTypedArray);
     table_.Register(kVisitFixedFloat64Array, &EvacuateFixedFloat64Array);
+    table_.Register(kVisitJSArrayBuffer, &EvacuateJSArrayBuffer);
 
     table_.Register(
         kVisitNativeContext,
@@ -2118,9 +2199,6 @@ class ScavengingVisitor : public StaticVisitorBase {
     table_.Register(kVisitJSWeakCollection,
                     &ObjectEvacuationStrategy<POINTER_OBJECT>::Visit);
 
-    table_.Register(kVisitJSArrayBuffer,
-                    &ObjectEvacuationStrategy<POINTER_OBJECT>::Visit);
-
     table_.Register(kVisitJSTypedArray,
                     &ObjectEvacuationStrategy<POINTER_OBJECT>::Visit);
 
@@ -2348,6 +2426,18 @@ class ScavengingVisitor : public StaticVisitorBase {
   }
 
 
+  static inline void EvacuateJSArrayBuffer(Map* map, HeapObject** slot,
+                                           HeapObject* object) {
+    ObjectEvacuationStrategy<POINTER_OBJECT>::Visit(map, slot, object);
+
+    Heap* heap = map->GetHeap();
+    MapWord map_word = object->map_word();
+    DCHECK(map_word.IsForwardingAddress());
+    HeapObject* target = map_word.ToForwardingAddress();
+    if (!heap->InNewSpace(target)) heap->PromoteArrayBuffer(target);
+  }
+
+
   static inline void EvacuateByteArray(Map* map, HeapObject** slot,
                                        HeapObject* object) {
     int object_size = reinterpret_cast<ByteArray*>(object)->ByteArraySize();