Merging ContentArray into DescriptorArray

src/objects.h

Index: src/objects.h
diff --git a/src/objects.h b/src/objects.h
index 4fd29ad56227d368d2ebb0773c566f6cba3909b0..b2f44a183d08818b2da3622f14df8ea92df7b4e3 100644
--- a/src/objects.h
+++ b/src/objects.h
@@ -2429,7 +2429,7 @@ class DescriptorArray: public FixedArray {
   int number_of_descriptors() {
     ASSERT(length() > kFirstIndex || IsEmpty());
     int len = length();
-    return len <= kFirstIndex ? 0 : len - kFirstIndex;
+    return len <= kFirstIndex ? 0 : (len - kFirstIndex) / kDescriptorSize;
   }
 
   int NextEnumerationIndex() {
@@ -2459,6 +2459,12 @@ class DescriptorArray: public FixedArray {
     return bridge->get(kEnumCacheBridgeCacheIndex);
   }
 
+  Object** GetEnumCacheSlot() {
+    ASSERT(HasEnumCache());
+    return HeapObject::RawField(reinterpret_cast<HeapObject*>(this),
+                                kEnumerationIndexOffset);
+  }
+
   // TODO(1399): It should be possible to make room for bit_field3 in the map
   //             without overloading the instance descriptors field in the map
   //             (and storing it in the DescriptorArray when the map has one).
@@ -2473,8 +2479,16 @@ class DescriptorArray: public FixedArray {
 
   // Accessors for fetching instance descriptor at descriptor number.
   inline String* GetKey(int descriptor_number);
+  inline Object** GetKeySlot(int descriptor_number);
   inline Object* GetValue(int descriptor_number);
+  inline Object** GetValueSlot(int descriptor_number);
+  inline void SetNullValueUnchecked(int descriptor_number, Heap* heap);
   inline PropertyDetails GetDetails(int descriptor_number);
+  inline void SetDetailsUnchecked(int descriptor_number, Smi* value);
+
+  inline Object* RawGetValue(int descriptor_number);
+  inline PropertyDetails RawGetDetails(int descriptor_number);
+
   inline PropertyType GetType(int descriptor_number);
   inline int GetFieldIndex(int descriptor_number);
   inline JSFunction* GetConstantFunction(int descriptor_number);
@@ -2484,6 +2498,13 @@ class DescriptorArray: public FixedArray {
   inline bool IsTransitionOnly(int descriptor_number);
   inline bool IsNullDescriptor(int descriptor_number);
 
+  // WhitenessWitness is used to prove that a specific descriptor array is white
+  // (unmarked), so potentially unique heap objects can be freely assigned
+  // without potentially causing memory leaks. A witness is always
+  // stack-allocated right after creating a descriptor array. By allocating a witness,

[Florian Schneider, 2012/05/22 16:53:09]

Long line.

+  // incremental marking is globally disabled. The witness is then passed along
+  // wherever needed to statically prove that the descriptor array is known to
+  // be white.
   class WhitenessWitness {
    public:
     inline explicit WhitenessWitness(DescriptorArray* array);
@@ -2567,9 +2588,8 @@ class DescriptorArray: public FixedArray {
   static const int kNotFound = -1;
 
   static const int kBitField3StorageIndex = 0;
-  static const int kContentArrayIndex = 1;
-  static const int kEnumerationIndexIndex = 2;
-  static const int kFirstIndex = 3;
+  static const int kEnumerationIndexIndex = 1;
+  static const int kFirstIndex = 2;
 
   // The length of the "bridge" to the enum cache.
   static const int kEnumCacheBridgeLength = 3;
@@ -2579,8 +2599,8 @@ class DescriptorArray: public FixedArray {
 
   // Layout description.
   static const int kBitField3StorageOffset = FixedArray::kHeaderSize;
-  static const int kContentArrayOffset = kBitField3StorageOffset + kPointerSize;
-  static const int kEnumerationIndexOffset = kContentArrayOffset + kPointerSize;
+  static const int kEnumerationIndexOffset = kBitField3StorageOffset +
+                                             kPointerSize;
   static const int kFirstOffset = kEnumerationIndexOffset + kPointerSize;
 
   // Layout description for the bridge array.
@@ -2588,6 +2608,12 @@ class DescriptorArray: public FixedArray {
   static const int kEnumCacheBridgeCacheOffset =
     kEnumCacheBridgeEnumOffset + kPointerSize;
 
+  // Layout of descriptor.
+  static const int kDescriptorSize = 3;

[Florian Schneider, 2012/05/22 16:53:09]

Maybe sort the constants for the layout by increasing numbers.

+  static const int kDescriptorKey = 0;
+  static const int kDescriptorDetails = 1;
+  static const int kDescriptorValue = 2;
+
 #ifdef OBJECT_PRINT
   // Print all the descriptors.
   inline void PrintDescriptors() {
@@ -2628,15 +2654,21 @@ class DescriptorArray: public FixedArray {
 
   // Conversion from descriptor number to array indices.
   static int ToKeyIndex(int descriptor_number) {
-    return descriptor_number+kFirstIndex;
+    return kFirstIndex +
+           (descriptor_number * kDescriptorSize) +
+           kDescriptorKey;
   }
 
   static int ToDetailsIndex(int descriptor_number) {
-    return (descriptor_number << 1) + 1;
+    return kFirstIndex +
+           (descriptor_number * kDescriptorSize) +
+           kDescriptorDetails;
   }
 
   static int ToValueIndex(int descriptor_number) {
-    return descriptor_number << 1;
+    return kFirstIndex +
+           (descriptor_number * kDescriptorSize) +
+           kDescriptorValue;
   }
 
   // Swap operation on FixedArray without using write barriers.
@@ -2647,9 +2679,6 @@ class DescriptorArray: public FixedArray {
   inline void NoIncrementalWriteBarrierSwapDescriptors(
       int first, int second);
 
-  FixedArray* GetContentArray() {
-    return FixedArray::cast(get(kContentArrayIndex));
-  }
   DISALLOW_IMPLICIT_CONSTRUCTORS(DescriptorArray);
 };