Reland of "Enable inobject double fields unboxing for 64-bit archs."

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 501 matching lines @@
                 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)) {
+                    if (helper.IsTagged(static_cast<int>(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,
@@ skipping 61 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