Faster implementation of Heap::RecordWrites.

src/heap-inl.h

 // Copyright 2006-2008 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 178 matching lines @@
   if (new_space_.Contains(address)) return;
   ASSERT(!new_space_.FromSpaceContains(address));
   SLOW_ASSERT(Contains(address + offset));
   Page::FromAddress(address)->MarkRegionDirty(address + offset);
 }
 
 
 void Heap::RecordWrites(Address address, int start, int len) {
   if (new_space_.Contains(address)) return;
   ASSERT(!new_space_.FromSpaceContains(address));
-  for (int offset = start;
-       offset < start + len * kPointerSize;
-       offset += kPointerSize) {
-    SLOW_ASSERT(Contains(address + offset));
-    Page::FromAddress(address)->MarkRegionDirty(address + offset);
-  }
+  Page* page = Page::FromAddress(address);
+  page->SetRegionMarks(page->GetRegionMarks() |
+      page->GetRegionMaskForSpan(address + start, len * kPointerSize));
 }
 
 
 OldSpace* Heap::TargetSpace(HeapObject* object) {
   InstanceType type = object->map()->instance_type();
   AllocationSpace space = TargetSpaceId(type);
   return (space == OLD_POINTER_SPACE)
       ? old_pointer_space_
       : old_data_space_;
 }
@@ skipping 272 matching lines @@
 
 
 void ExternalStringTable::ShrinkNewStrings(int position) {
   new_space_strings_.Rewind(position);
   Verify();
 }
 
 } }  // namespace v8::internal
 
 #endif  // V8_HEAP_INL_H_