Support weak heap references in the ConstantPool to support IsWeakObjectInOptimizedCode objects.

src/objects-visiting-inl.h

Index: src/objects-visiting-inl.h
diff --git a/src/objects-visiting-inl.h b/src/objects-visiting-inl.h
index 4f1498844dc496c4aed94996b0d509cccba1602e..9cd50c425ac9e3bc5849c92d6a1087e91f9030af 100644
--- a/src/objects-visiting-inl.h
+++ b/src/objects-visiting-inl.h
@@ -501,6 +501,14 @@ void StaticMarkingVisitor<StaticVisitor>::VisitConstantPoolArray(
     StaticVisitor::VisitPointer(heap,

[ulan, 2014/03/19 08:50:00]

IIUC, each heap object pointer in constant pool is also visited via reloc-info
in
StaticMarkingVisitor<StaticVisitor>::VisitEmbeddedPointer and
StaticMarkingVisitor<StaticVisitor>::VisitCell.
Those visitors already handle weak pointers.

It would be cleaner to avoid copying that logic here and in assembler-arm.

I think it is safe to only record slot for a heap pointer and not mark it (i.e.
replace VisitPointer with RecordSlot) since we will mark it via reloc-info
anyway. If we do that, then there is no need to track weak pointers separately
from heap pointers. WDYT?

                                 constant_pool->RawFieldOfElementAt(index));
   }
+  for (int i = 0; i < constant_pool->count_of_weak_ptr_entries(); i++) {
+    int index = constant_pool->first_weak_ptr_index() + i;
+    Object** slot = constant_pool->RawFieldOfElementAt(index);
+    HeapObject* object = HeapObject::cast(*slot);
+    if (!object->IsCell()) {
+      heap->mark_compact_collector()->RecordSlot(slot, slot, object);
+    }
+  }
 }