Reland "In-object double fields unboxing (for 64-bit only)."

src/heap/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 <algorithm>
 
 #include "src/v8.h"
 
 #include "src/base/atomicops.h"
 #include "src/counters.h"
@@ skipping 489 matching lines @@
                 // TODO(hpayer): This may introduce a huge pause here. We
                 // just care about finish sweeping of the scan on scavenge page.
                 heap_->mark_compact_collector()->EnsureSweepingCompleted();
               }
             }
             CHECK(page->owner() == heap_->old_pointer_space());
             HeapObjectIterator iterator(page, NULL);
             for (HeapObject* heap_object = iterator.Next(); heap_object != NULL;
                  heap_object = iterator.Next()) {
               // We iterate over objects that contain new space pointers only.
-              if (!heap_object->MayContainRawValues()) {
-                FindPointersToNewSpaceInRegion(
-                    heap_object->address() + HeapObject::kHeaderSize,
-                    heap_object->address() + heap_object->Size(), slot_callback,
-                    clear_maps);
+              bool may_contain_raw_values = heap_object->MayContainRawValues();
+              if (!may_contain_raw_values) {
+                Address obj_address = heap_object->address();
+                Address start_address = obj_address + HeapObject::kHeaderSize;
+                Address end_address = obj_address + heap_object->Size();
+#if V8_DOUBLE_FIELDS_UNBOXING
+                InobjectPropertiesHelper helper(heap_object->map());
+                bool has_only_tagged_fields = helper.all_fields_tagged();
+
+                if (!has_only_tagged_fields) {
+                  for (Address slot = start_address; slot < end_address;
+                       slot += kPointerSize) {
+                    if (helper.IsTagged(slot - obj_address)) {
+                      // TODO(ishell): call this once for contiguous region
+                      // of tagged fields.
+                      FindPointersToNewSpaceInRegion(slot, slot + kPointerSize,
+                                                     slot_callback, clear_maps);
+                    }
+                  }
+                } else {
+#endif
+                  // Object has only tagged fields.
+                  FindPointersToNewSpaceInRegion(start_address, end_address,
+                                                 slot_callback, clear_maps);
+#if V8_DOUBLE_FIELDS_UNBOXING
+                }
+#endif
               }
             }
           }
         }
       }
     }
     if (callback_ != NULL) {
       (*callback_)(heap_, NULL, kStoreBufferScanningPageEvent);
     }
   }
@@ skipping 47 matching lines @@
     }
     old_buffer_is_sorted_ = false;
     old_buffer_is_filtered_ = false;
     *old_top_++ = reinterpret_cast<Address>(int_addr << kPointerSizeLog2);
     DCHECK(old_top_ <= old_limit_);
   }
   heap_->isolate()->counters()->store_buffer_compactions()->Increment();
 }
 }
 }  // namespace v8::internal