[runtime] Allocate space for computed property names

src/objects.h

 // Copyright 2015 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_OBJECTS_H_
 #define V8_OBJECTS_H_
 
 #include <iosfwd>
 #include <memory>
 
@@ skipping 1044 matching lines @@
   V(FrameArray)                  \
   V(TransitionArray)             \
   V(LiteralsArray)               \
   V(TypeFeedbackMetadata)        \
   V(TypeFeedbackVector)          \
   V(DeoptimizationInputData)     \
   V(DeoptimizationOutputData)    \
   V(DependentCode)               \
   V(HandlerTable)                \
   V(FixedArray)                  \
+  V(ConstantProperties)          \
   V(FixedDoubleArray)            \
   V(WeakFixedArray)              \
   V(ArrayList)                   \
   V(RegExpMatchInfo)             \
   V(Context)                     \
   V(ScriptContextTable)          \
   V(NativeContext)               \
   V(ScopeInfo)                   \
   V(ModuleInfo)                  \
   V(JSBoundFunction)             \
@@ skipping 1832 matching lines @@
   static inline void NoWriteBarrierSet(FixedArray* array,
                                        int index,
                                        Object* value);
 
  private:
   STATIC_ASSERT(kHeaderSize == Internals::kFixedArrayHeaderSize);
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(FixedArray);
 };
 
+// ConstantProperties is a special FixedArray of constant properties that
+// provides access to the total number of properties (constant and
+// non-constant).
+// Usually, the number of properties is half the length of the
+// FixedArray (half because it consists of key-value pairs), but there could
+// have been non-constant property names for which we need to allocate space in
+// the property backing store as well.
+// The parser stores the total number after the last object in
+// the FixedArray. ConstantProperties simplifies access to this number.

[Toon Verwaest, 2017/01/18 08:49:53]

What about also adding name(i) and value(i) which just does get(i*2) and
get(i*2+1)?

Perhaps ConstantProperties isn't exactly the best name since their values aren't
constant... What about just BoilerplateDescription or so?

[Franzi, 2017/01/18 14:23:10]

name() and value() looks nice. Thanks! Changed the name as well. 

+class ConstantProperties : public FixedArray {
+ public:
+  // Number of constant and non-constant properties.
+  int const number_of_properties();
+  // Actual size of the FixedArray, i.e., twice the number of constant
+  // properties without the field that contains the total number.
+  int const length();
+
+  DECLARE_CAST(ConstantProperties)
+
+ private:
+  bool const has_number_of_properties();
+};
 
 // FixedDoubleArray describes fixed-sized arrays with element type double.
 class FixedDoubleArray: public FixedArrayBase {
  public:
   // Setter and getter for elements.
   inline double get_scalar(int index);
   inline uint64_t get_representation(int index);
   static inline Handle<Object> get(FixedDoubleArray* array, int index,
                                    Isolate* isolate);
   inline void set(int index, double value);
@@ skipping 3463 matching lines @@
   // of endianess. Also provide endian-independent offset to that 16-bit word.
   static const int kInstanceTypeOffset = kInstanceAttributesOffset + 0;
   static const int kBitFieldOffset = kInstanceAttributesOffset + 1;
 #else
   static const int kBitFieldOffset = kInstanceAttributesOffset + 0;
   static const int kInstanceTypeOffset = kInstanceAttributesOffset + 1;
 #endif
   static const int kInstanceTypeAndBitFieldOffset =
       kInstanceAttributesOffset + 0;
   static const int kBitField2Offset = kInstanceAttributesOffset + 2;
-  static const int kUnusedPropertyFieldsByte = 3;

[Toon Verwaest, 2017/01/18 08:49:53]

why remove this?

[Franzi, 2017/01/18 14:23:10]

Noticed that it's unused. Any reason we need to keep it?

   static const int kUnusedPropertyFieldsOffset = kInstanceAttributesOffset + 3;
 
   STATIC_ASSERT(kInstanceTypeAndBitFieldOffset ==
                 Internals::kMapInstanceTypeAndBitFieldOffset);
 
   // Bit positions for bit field.
   static const int kHasNonInstancePrototype = 0;
   static const int kIsCallable = 1;
   static const int kHasNamedInterceptor = 2;
   static const int kHasIndexedInterceptor = 3;
@@ skipping 5285 matching lines @@
   }
 };
 
 
 }  // NOLINT, false-positive due to second-order macros.
 }  // NOLINT, false-positive due to second-order macros.
 
 #include "src/objects/object-macros-undef.h"
 
 #endif  // V8_OBJECTS_H_