Forward transition objects to grey if they are referenced by a large object

src/incremental-marking-inl.h

Index: src/incremental-marking-inl.h
diff --git a/src/incremental-marking-inl.h b/src/incremental-marking-inl.h
index bbe9a9d209b36cca76360b2f9b091b755dc0587a..42197df397f2042a0e40e43a565fb84c0f28d505 100644
--- a/src/incremental-marking-inl.h
+++ b/src/incremental-marking-inl.h
@@ -37,16 +37,22 @@ namespace internal {
 bool IncrementalMarking::BaseRecordWrite(HeapObject* obj,
                                          Object** slot,
                                          Object* value) {
-  MarkBit value_bit = Marking::MarkBitFrom(HeapObject::cast(value));
+  HeapObject* value_heap_obj = HeapObject::cast(value);
+  MarkBit value_bit = Marking::MarkBitFrom(value_heap_obj);
   if (Marking::IsWhite(value_bit)) {
     MarkBit obj_bit = Marking::MarkBitFrom(obj);
-    if (Marking::IsBlack(obj_bit)) {
+    // TODO(hpayer): make decision based on if object has a progress bar

[Michael Starzinger, 2012/11/15 18:04:26]

As discussed offline, can we rebase that to the brand new progress bar and check
for the HAS_PROGRESS_BAR page flag here?

[payer, 2012/11/16 13:43:05]

Done.

I will add the optimization in the next CL.

+    const int kLargeObjectSize = 1024 * 1024;
+    if (Marking::IsBlack(obj_bit) && obj->Size() > kLargeObjectSize) {
+      WhiteToGreyAndPush(value_heap_obj, value_bit);
+      RestartIfNotMarking();
+    } else if (Marking::IsBlack(obj_bit)) {

[Michael Starzinger, 2012/11/15 18:04:26]

Can we rewrite the condition so that it does the Marking::IsBlack only once,
unfortunately GCC isn't smart enough to optimize it away.

[payer, 2012/11/16 13:43:05]

Done.

       BlackToGreyAndUnshift(obj, obj_bit);
       RestartIfNotMarking();
+      return false;
+    } else
+      return false;
     }
-
-    // Object is either grey or white.  It will be scanned if survives.
-    return false;
   }
   if (!is_compacting_) return false;
   MarkBit obj_bit = Marking::MarkBitFrom(obj);