Use an allocation site scratchpad to speed up allocaton site processing during gc.

src/heap-inl.h

Index: src/heap-inl.h
diff --git a/src/heap-inl.h b/src/heap-inl.h
index 3229aeecc3096fa74bc9f022616eb277b4e79d58..9dacefce63b14ca93259b2ef2ac6be26e75e5c3a 100644
--- a/src/heap-inl.h
+++ b/src/heap-inl.h
@@ -489,7 +489,17 @@ void Heap::UpdateAllocationSiteFeedback(HeapObject* object) {
         JSObject::cast(object), true);
     if (memento != NULL) {
       ASSERT(memento->IsValid());
-      memento->GetAllocationSite()->IncrementMementoFoundCount();
+      bool add_to_scratchpad =
+          memento->GetAllocationSite()->IncrementMementoFoundCount();
+      Heap* heap = object->GetIsolate()->heap();
+      if (heap->allocation_sites_scratchpad_pointer <
+              kAllocationSiteScratchpadSize &&
+          add_to_scratchpad) {

[mvstanton, 2013/12/13 10:30:17]

put add_to_scratchpad first in the if expression.

[Hannes Payer (out of office), 2013/12/18 14:29:19]

Done.

+        heap->allocation_sites_scratchpad[
+            heap->allocation_sites_scratchpad_pointer] =

[mvstanton, 2013/12/13 10:30:17]

nit: I'd be into the more compact
heap->allocation_sites_scratchpad[heap->allocation_sites_scratchpad_pointer++] =
memento->GetAllocationSite(). But it's up to you!

[Hannes Payer (out of office), 2013/12/18 14:29:19]

Done.

+                memento->GetAllocationSite();
+        heap->allocation_sites_scratchpad_pointer++;
+      }
     }
   }
 }