Precisely sweep scan on scavenge pages and use heap iterator to iterate over them.

BUG=
R=jarin@chromium.org

Review URL: https://codereview.chromium.org/362313002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@22154 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/mark-compact.cc

@@ -4146,12 +4146,23 @@ void MarkCompactCollector::SweepSpace(PagedSpace* space, SweeperType sweeper) {
           pages_swept++;
           parallel_sweeping_active = true;
         } else {
-          if (FLAG_gc_verbose) {
-            PrintF("Sweeping 0x%" V8PRIxPTR " conservatively in parallel.\n",
-                   reinterpret_cast<intptr_t>(p));
+          if (p->scan_on_scavenge()) {
+            SweepPrecisely<SWEEP_ONLY, IGNORE_SKIP_LIST, IGNORE_FREE_SPACE>(
+                space, p, NULL);
+            pages_swept++;
+            if (FLAG_gc_verbose) {
+              PrintF("Sweeping 0x%" V8PRIxPTR
+                  " scan on scavenge page precisely.\n",
+                  reinterpret_cast<intptr_t>(p));
+            }
+          } else {
+            if (FLAG_gc_verbose) {
+              PrintF("Sweeping 0x%" V8PRIxPTR " conservatively in parallel.\n",
+                  reinterpret_cast<intptr_t>(p));
+            }
+            p->set_parallel_sweeping(MemoryChunk::PARALLEL_SWEEPING_PENDING);
+            space->IncreaseUnsweptFreeBytes(p);
           }
-          p->set_parallel_sweeping(MemoryChunk::PARALLEL_SWEEPING_PENDING);
-          space->IncreaseUnsweptFreeBytes(p);
         }
         space->set_end_of_unswept_pages(p);
         break;

src/store-buffer.cc

@@ -552,8 +552,21 @@ void StoreBuffer::IteratePointersToNewSpace(ObjectSlotCallback slot_callback,
             FindPointersToNewSpaceInMapsRegion(
                 start, end, slot_callback, clear_maps);
           } else {
-            FindPointersToNewSpaceInRegion(
-                start, end, slot_callback, clear_maps);
+            ASSERT(page->WasSweptPrecisely());
+            HeapObjectIterator iterator(page, NULL);
+            for (HeapObject* heap_object = iterator.Next();
+                 heap_object != NULL;
+                 heap_object = iterator.Next()) {
+              // We skip filler, free space, and constant pool objects.
+              if (!heap_object->IsFiller() &&
+                  !heap_object->IsConstantPoolArray()) {
+                FindPointersToNewSpaceInRegion(
+                    heap_object->address() + HeapObject::kHeaderSize,
+                    heap_object->address() + heap_object->Size(),
+                    slot_callback,
+                    clear_maps);
+              }
+            }
           }
         }
       }