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

src/store-buffer.cc

 // Copyright 2011 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/store-buffer.h"
 
 #include <algorithm>
 
 #include "src/v8.h"
 
@@ skipping 501 matching lines @@
         }
         if (chunk->owner() == heap_->lo_space()) {
           LargePage* large_page = reinterpret_cast<LargePage*>(chunk);
           HeapObject* array = large_page->GetObject();
           ASSERT(array->IsFixedArray());
           Address start = array->address();
           Address end = start + array->Size();
           FindPointersToNewSpaceInRegion(start, end, slot_callback, clear_maps);
         } else {
           Page* page = reinterpret_cast<Page*>(chunk);
-          PagedSpace* owner = reinterpret_cast<PagedSpace*>(page->owner());
-          Address start = page->area_start();
-          Address end = page->area_end();
-          if (owner == heap_->map_space()) {
-            ASSERT(page->WasSweptPrecisely());
-            HeapObjectIterator iterator(page, NULL);
-            for (HeapObject* heap_object = iterator.Next(); heap_object != NULL;
-                 heap_object = iterator.Next()) {
-              // We skip free space objects.
-              if (!heap_object->IsFiller()) {
-                FindPointersToNewSpaceInRegion(
-                    heap_object->address() + HeapObject::kHeaderSize,
-                    heap_object->address() + heap_object->Size(), slot_callback,
-                    clear_maps);
-              }
+          ASSERT(page->owner() == heap_->map_space() ||
+                 page->owner() == heap_->old_pointer_space());
+          CHECK(page->WasSweptPrecisely());
+
+          HeapObjectIterator iterator(page, NULL);
+          for (HeapObject* heap_object = iterator.Next();
+               heap_object != NULL;
+               heap_object = iterator.Next()) {
+            // We iterate over objects that contain pointers only.
+            if (heap_object->ContainsPointers()) {
+              FindPointersToNewSpaceInRegion(
+                  heap_object->address() + HeapObject::kHeaderSize,
+                  heap_object->address() + heap_object->Size(),
+                  slot_callback,
+                  clear_maps);
             }
-          } else {
-            FindPointersToNewSpaceInRegion(
-                start, end, slot_callback, clear_maps);
           }
         }
       }
     }
     if (callback_ != NULL) {
       (*callback_)(heap_, NULL, kStoreBufferScanningPageEvent);
     }
   }
 }
 
@@ skipping 45 matching lines @@
     }
     old_buffer_is_sorted_ = false;
     old_buffer_is_filtered_ = false;
     *old_top_++ = reinterpret_cast<Address>(int_addr << kPointerSizeLog2);
     ASSERT(old_top_ <= old_limit_);
   }
   heap_->isolate()->counters()->store_buffer_compactions()->Increment();
 }
 
 } }  // namespace v8::internal