Access old space marking bits from runtime only when incremental marking is in MARKING state.

src/objects.cc

Index: src/objects.cc
diff --git a/src/objects.cc b/src/objects.cc
index cb8489f6d29f47dcb9ac75b6d985e9bd6a538da0..d4612e7de8abf572401714ce221922e441df137a 100644
--- a/src/objects.cc
+++ b/src/objects.cc
@@ -1301,7 +1301,8 @@ bool String::MakeExternal(v8::String::ExternalStringResource* resource) {
   // Fill the remainder of the string with dead wood.
   int new_size = this->Size();  // Byte size of the external String object.
   heap->CreateFillerObjectAt(this->address() + new_size, size - new_size);
-  if (Marking::IsBlack(Marking::MarkBitFrom(this))) {
+  if (heap->incremental_marking()->IsMarking() &&
+      Marking::IsBlack(Marking::MarkBitFrom(this))) {
     MemoryChunk::IncrementLiveBytesFromMutator(this->address(),
                                                new_size - size);
   }
@@ -1360,7 +1361,8 @@ bool String::MakeExternal(v8::String::ExternalAsciiStringResource* resource) {
   // Fill the remainder of the string with dead wood.
   int new_size = this->Size();  // Byte size of the external String object.
   heap->CreateFillerObjectAt(this->address() + new_size, size - new_size);
-  if (Marking::IsBlack(Marking::MarkBitFrom(this))) {
+  if (heap->incremental_marking()->IsMarking() &&
+      Marking::IsBlack(Marking::MarkBitFrom(this))) {
     MemoryChunk::IncrementLiveBytesFromMutator(this->address(),
                                                new_size - size);
   }
@@ -2301,7 +2303,8 @@ static void RightTrimFixedArray(Heap* heap, FixedArray* elms, int to_trim) {
   elms->set_length(len - to_trim);
 
   // Maintain marking consistency for IncrementalMarking.
-  if (Marking::IsBlack(Marking::MarkBitFrom(elms))) {
+  if (heap->incremental_marking()->IsMarking() &&
+      Marking::IsBlack(Marking::MarkBitFrom(elms))) {

[Michael Starzinger, 2014/03/19 09:30:35]

As discussed offline: I am not sure distinguishing between friends of "Marking"
or not will help, because it mainly depends on the call-path leading there, not
so much the call-site

Another proposal would be to factor our this general logic for adjusting live
bytes into a Heap::AdjustLiveBytes() helper that would take care of checking the
proper pre-conditions. The RightTrimMode would probably need to be renamed to
something like LiveBytesAdjustmentMode.

[Hannes Payer (out of office), 2014/03/19 11:27:51]

Done.

     if (trim_mode == FROM_GC) {
       MemoryChunk::IncrementLiveBytesFromGC(elms->address(), -size_delta);
     } else {
@@ -4643,9 +4646,11 @@ void JSObject::NormalizeProperties(Handle<JSObject> object,
   int new_instance_size = new_map->instance_size();
   int instance_size_delta = map->instance_size() - new_instance_size;
   ASSERT(instance_size_delta >= 0);
-  isolate->heap()->CreateFillerObjectAt(object->address() + new_instance_size,
-                                        instance_size_delta);
-  if (Marking::IsBlack(Marking::MarkBitFrom(*object))) {
+  Heap* heap = isolate->heap();
+  heap->CreateFillerObjectAt(object->address() + new_instance_size,
+                             instance_size_delta);
+  if (heap->incremental_marking()->IsMarking() &&
+      Marking::IsBlack(Marking::MarkBitFrom(*object))) {
     MemoryChunk::IncrementLiveBytesFromMutator(object->address(),
                                                -instance_size_delta);
   }
@@ -9217,7 +9222,8 @@ Handle<String> SeqString::Truncate(Handle<SeqString> string, int new_length) {
     // that are a multiple of pointer size.
     heap->CreateFillerObjectAt(start_of_string + new_size, delta);
   }
-  if (Marking::IsBlack(Marking::MarkBitFrom(start_of_string))) {
+  if (heap->incremental_marking()->IsMarking() &&
+      Marking::IsBlack(Marking::MarkBitFrom(start_of_string))) {
     MemoryChunk::IncrementLiveBytesFromMutator(start_of_string, -delta);
   }