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

src/field-index.h

 // Copyright 2014 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.
 
 #ifndef V8_FIELD_INDEX_H_
 #define V8_FIELD_INDEX_H_
 
 #include "src/property-details.h"
 #include "src/utils.h"
 
@@ skipping 16 matching lines @@
   static FieldIndex ForLoadByFieldIndex(Map* map, int index);
   static FieldIndex ForKeyedLookupCacheIndex(Map* map, int index);
   static FieldIndex FromFieldAccessStubKey(int key);
 
   int GetLoadByFieldIndex() const;
 
   bool is_inobject() const {
     return IsInObjectBits::decode(bit_field_);
   }
 
+  bool is_hidden_field() const { return IsHiddenField::decode(bit_field_); }
+
   bool is_double() const {
     return IsDoubleBits::decode(bit_field_);
   }
 
   int offset() const {
     return index() * kPointerSize;
   }
 
   // Zero-indexed from beginning of the object.
   int index() const {
     return IndexBits::decode(bit_field_);
   }
 
   int outobject_array_index() const {
     DCHECK(!is_inobject());
     return index() - first_inobject_property_offset() / kPointerSize;
   }
 
   // Zero-based from the first inobject property. Overflows to out-of-object
   // properties.
   int property_index() const {
-    DCHECK(!IsHiddenField::decode(bit_field_));
+    DCHECK(!is_hidden_field());
     int result = index() - first_inobject_property_offset() / kPointerSize;
     if (!is_inobject()) {
       result += InObjectPropertyBits::decode(bit_field_);
     }
     return result;
   }
 
   int GetKeyedLookupCacheIndex() const;
 
   int GetFieldAccessStubKey() const {
@@ skipping 10 matching lines @@
       IsDoubleBits::encode(is_double) |
       FirstInobjectPropertyOffsetBits::encode(first_inobject_property_offset) |
       IsHiddenField::encode(is_hidden) |
       IndexBits::encode(local_index) |
       InObjectPropertyBits::encode(inobject_properties);
   }
 
   explicit FieldIndex(int bit_field) : bit_field_(bit_field) {}
 
   int first_inobject_property_offset() const {
-    DCHECK(!IsHiddenField::decode(bit_field_));
+    DCHECK(!is_hidden_field());
     return FirstInobjectPropertyOffsetBits::decode(bit_field_);
   }
 
   static const int kIndexBitsSize = kDescriptorIndexBitCount + 1;
 
   // Index from beginning of object.
   class IndexBits: public BitField<int, 0, kIndexBitsSize> {};
   class IsInObjectBits: public BitField<bool, IndexBits::kNext, 1> {};
   class IsDoubleBits: public BitField<bool, IsInObjectBits::kNext, 1> {};
   // Number of inobject properties.
   class InObjectPropertyBits
       : public BitField<int, IsDoubleBits::kNext, kDescriptorIndexBitCount> {};
   // Offset of first inobject property from beginning of object.
   class FirstInobjectPropertyOffsetBits
       : public BitField<int, InObjectPropertyBits::kNext, 7> {};
   class IsHiddenField
       : public BitField<bool, FirstInobjectPropertyOffsetBits::kNext, 1> {};
   STATIC_ASSERT(IsHiddenField::kNext <= 32);
 
   int bit_field_;
 };
 
 } }  // namespace v8::internal
 
 #endif