Implement core support for FixedDoubleArrays.

src/objects.h

 // Copyright 2011 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 513 matching lines @@
   BYTE_ARRAY_TYPE,
   EXTERNAL_BYTE_ARRAY_TYPE,  // FIRST_EXTERNAL_ARRAY_TYPE
   EXTERNAL_UNSIGNED_BYTE_ARRAY_TYPE,
   EXTERNAL_SHORT_ARRAY_TYPE,
   EXTERNAL_UNSIGNED_SHORT_ARRAY_TYPE,
   EXTERNAL_INT_ARRAY_TYPE,
   EXTERNAL_UNSIGNED_INT_ARRAY_TYPE,
   EXTERNAL_FLOAT_ARRAY_TYPE,
   EXTERNAL_DOUBLE_ARRAY_TYPE,
   EXTERNAL_PIXEL_ARRAY_TYPE,  // LAST_EXTERNAL_ARRAY_TYPE
+  FIXED_DOUBLE_ARRAY_TYPE,
   FILLER_TYPE,  // LAST_DATA_TYPE
 
   // Structs.
   ACCESSOR_INFO_TYPE,
   ACCESS_CHECK_INFO_TYPE,
   INTERCEPTOR_INFO_TYPE,
   CALL_HANDLER_INFO_TYPE,
   FUNCTION_TEMPLATE_INFO_TYPE,
   OBJECT_TEMPLATE_INFO_TYPE,
   SIGNATURE_INFO_TYPE,
@@ skipping 178 matching lines @@
   V(ExternalPixelArray)                        \
   V(ByteArray)                                 \
   V(JSReceiver)                                \
   V(JSObject)                                  \
   V(JSContextExtensionObject)                  \
   V(Map)                                       \
   V(DescriptorArray)                           \
   V(DeoptimizationInputData)                   \
   V(DeoptimizationOutputData)                  \
   V(FixedArray)                                \
+  V(FixedDoubleArray)                          \
   V(Context)                                   \
   V(CatchContext)                              \
   V(GlobalContext)                             \
   V(JSFunction)                                \
   V(Code)                                      \
   V(Oddball)                                   \
   V(SharedFunctionInfo)                        \
   V(JSValue)                                   \
   V(JSMessageObject)                           \
   V(StringWrapper)                             \
@@ skipping 47 matching lines @@
   INLINE(bool IsUndefined());
   INLINE(bool IsNull());
   INLINE(bool IsTheHole());  // Shadows MaybeObject's implementation.
   INLINE(bool IsTrue());
   INLINE(bool IsFalse());
   inline bool IsArgumentsMarker();
 
   // Extract the number.
   inline double Number();
 
+  // Returns true if the object is of the correct type to be used as a
+  // implementation of a JSObject's elements.
+  inline bool HasValidElements();
+
   inline bool HasSpecificClassOf(String* name);
 
   MUST_USE_RESULT MaybeObject* ToObject();             // ECMA-262 9.9.
   Object* ToBoolean();                                 // ECMA-262 9.2.
 
   // Convert to a JSObject if needed.
   // global_context is used when creating wrapper object.
   MUST_USE_RESULT MaybeObject* ToObject(Context* global_context);
 
   // Converts this to a Smi if possible.
@@ skipping 607 matching lines @@
   enum DeleteMode {
     NORMAL_DELETION,
     STRICT_DELETION,
     FORCE_DELETION
   };
 
   enum ElementsKind {
     // The "fast" kind for tagged values. Must be first to make it possible
     // to efficiently check maps if they have fast elements.
     FAST_ELEMENTS,
+
+    // The "fast" kind for unwrapped, non-tagged double values.
+    FAST_DOUBLE_ELEMENTS,
+
     // The "slow" kind.
     DICTIONARY_ELEMENTS,
     // The "fast" kind for external arrays
     EXTERNAL_BYTE_ELEMENTS,
     EXTERNAL_UNSIGNED_BYTE_ELEMENTS,
     EXTERNAL_SHORT_ELEMENTS,
     EXTERNAL_UNSIGNED_SHORT_ELEMENTS,
     EXTERNAL_INT_ELEMENTS,
     EXTERNAL_UNSIGNED_INT_ELEMENTS,
     EXTERNAL_FLOAT_ELEMENTS,
@@ skipping 31 matching lines @@
   // arrays). In the latter case the elements array may be shared by a
   // few objects and so before writing to any element the array must
   // be copied. Use EnsureWritableFastElements in this case.
   //
   // In the slow mode elements is either a NumberDictionary or an ExternalArray.
   DECL_ACCESSORS(elements, HeapObject)
   inline void initialize_elements();
   MUST_USE_RESULT inline MaybeObject* ResetElements();
   inline ElementsKind GetElementsKind();
   inline bool HasFastElements();
+  inline bool HasFastDoubleElements();
   inline bool HasDictionaryElements();
   inline bool HasExternalPixelElements();
   inline bool HasExternalArrayElements();
   inline bool HasExternalByteElements();
   inline bool HasExternalUnsignedByteElements();
   inline bool HasExternalShortElements();
   inline bool HasExternalUnsignedShortElements();
   inline bool HasExternalIntElements();
   inline bool HasExternalUnsignedIntElements();
   inline bool HasExternalFloatElements();
@@ skipping 139 matching lines @@
   bool IsSimpleEnum();
 
   // Do we want to keep the elements in fast case when increasing the
   // capacity?
   bool ShouldConvertToSlowElements(int new_capacity);
   // Returns true if the backing storage for the slow-case elements of
   // this object takes up nearly as much space as a fast-case backing
   // storage would.  In that case the JSObject should have fast
   // elements.
   bool ShouldConvertToFastElements();
+  // Returns true if the elements of JSObject contains exclusively values
+  // that can be represented in a FixedDoubleArray.
+  bool ShouldConvertToFastDoubleElements();
 
   // Tells whether the index'th element is present.
   inline bool HasElement(uint32_t index);
   bool HasElementWithReceiver(JSReceiver* receiver, uint32_t index);
 
   // Computes the new capacity when expanding the elements of a JSObject.
   static int NewElementsCapacity(int old_capacity) {
     // (old_capacity + 50%) + 16
     return old_capacity + (old_capacity >> 1) + 16;
   }
@@ skipping 19 matching lines @@
   LocalElementType HasLocalElement(uint32_t index);
 
   bool HasElementWithInterceptor(JSReceiver* receiver, uint32_t index);
   bool HasElementPostInterceptor(JSReceiver* receiver, uint32_t index);
 
   MUST_USE_RESULT MaybeObject* SetFastElement(uint32_t index,
                                               Object* value,
                                               StrictModeFlag strict_mode,
                                               bool check_prototype = true);
 
+  MUST_USE_RESULT MaybeObject* SetFastDoubleElement(
+      uint32_t index,
+      Object* value,
+      StrictModeFlag strict_mode,
+      bool check_prototype = true);
+
   // Set the index'th array element.
   // A Failure object is returned if GC is needed.
   MUST_USE_RESULT MaybeObject* SetElement(uint32_t index,
                                           Object* value,
                                           StrictModeFlag strict_mode,
                                           bool check_prototype = true);
 
   // Returns the index'th element.
   // The undefined object if index is out of bounds.
   MaybeObject* GetElementWithReceiver(Object* receiver, uint32_t index);
   MaybeObject* GetElementWithInterceptor(Object* receiver, uint32_t index);
 
   // Get external element value at index if there is one and undefined
   // otherwise. Can return a failure if allocation of a heap number
   // failed.
   MaybeObject* GetExternalElement(uint32_t index);
 
   MUST_USE_RESULT MaybeObject* SetFastElementsCapacityAndLength(int capacity,
                                                                 int length);
+  MUST_USE_RESULT MaybeObject* SetFastDoubleElementsCapacityAndLength(
+      int capacity,
+      int length);
   MUST_USE_RESULT MaybeObject* SetSlowElements(Object* length);
 
   // Lookup interceptors are used for handling properties controlled by host
   // objects.
   inline bool HasNamedInterceptor();
   inline bool HasIndexedInterceptor();
 
   // Support functions for v8 api (needed for correct interceptor behavior).
   bool HasRealNamedProperty(String* key);
   bool HasRealElementProperty(uint32_t index);
@@ skipping 380 matching lines @@
  protected:
   // Set operation on FixedArray without using write barriers. Can
   // only be used for storing old space objects or smis.
   static inline void fast_set(FixedArray* array, int index, Object* value);
 
  private:
   DISALLOW_IMPLICIT_CONSTRUCTORS(FixedArray);
 };
 
 
+// FixedDoubleArray describes fixed-sized arrays with element type double

[Mads Ager (chromium), 2011/06/06 07:58:23]

Period at end of comment.

[danno, 2011/06/08 12:09:43]

Done.

+class FixedDoubleArray: public HeapObject {
+ public:
+  inline void Initialize(FixedArray* from);
+  inline void Initialize(FixedDoubleArray* from);
+  inline void Initialize(NumberDictionary* from);
+
+  // [length]: length of the array.
+  inline int length();
+  inline void set_length(int value);
+
+  // Setter and getter for elements.
+  inline double get(int index);
+  inline void set(int index, double value);
+  inline void set_the_hole(int index);
+
+  // Checking for the hole.
+  inline bool is_the_hole(int index);
+
+  // Garbage collection support.
+  inline static int SizeFor(int length) {
+    return kHeaderSize + length * kDoubleSize;
+  }
+
+  // The folllwing can't be declared inline as const static

[Mads Ager (chromium), 2011/06/06 07:58:23]

following

[danno, 2011/06/08 12:09:43]

Done.

+  // because they're 64-bit.
+  static uint64_t kCanonoicalNonHoleNanLower32;

[Mads Ager (chromium), 2011/06/06 07:58:23]

Canonical.

[danno, 2011/06/08 12:09:43]

Done.

+  static uint64_t kCanonoicalNonHoleNanInt64;

[Mads Ager (chromium), 2011/06/06 07:58:23]

Canonical.

[danno, 2011/06/08 12:09:43]

Done.

+  static uint64_t kHoleNanInt64;
+
+  inline static bool is_the_hole_nan(double value) {
+    return BitCast<uint64_t, double>(value) == kHoleNanInt64;
+  }
+
+  inline static double hole_nan_as_double() {
+    return BitCast<double, uint64_t>(kHoleNanInt64);
+  }
+
+  inline static double canonical_not_the_hole_nan_as_double() {
+    return BitCast<double, uint64_t>(kCanonoicalNonHoleNanInt64);
+  }
+
+  // Casting.
+  static inline FixedDoubleArray* cast(Object* obj);
+
+  // Layout description.
+  // Length is smi tagged when it is stored.

[Mads Ager (chromium), 2011/06/06 07:58:23]

Is it? Didn't we just use INT_ACCESSOR?

You could use kIntSize for the length and use the OBJECT_POINTER_ALIGN macro to
get the pointer-size aligned header size on all platforms. That will make it
clear that there are 32-bits unused in the header of 64-bit.

[danno, 2011/06/08 12:09:43]

Done.

+  static const int kLengthOffset = HeapObject::kHeaderSize;
+  static const int kHeaderSize = kLengthOffset + kPointerSize;
+
+  // Maximal allowed size, in bytes, of a single FixedDoubleArray.
+  // Prevents overflowing size computations, as well as extreme memory
+  // consumption.
+  static const int kMaxSize = 512 * MB;
+  // Maximally allowed length of a FixedArray.
+  static const int kMaxLength = (kMaxSize - kHeaderSize) / kDoubleSize;
+
+  // Dispatched behavior.
+#ifdef OBJECT_PRINT
+  inline void FixedDoubleArrayPrint() {
+    FixedDoubleArrayPrint(stdout);
+  }
+  void FixedDoubleArrayPrint(FILE* out);
+#endif
+
+ private:
+  DISALLOW_IMPLICIT_CONSTRUCTORS(FixedDoubleArray);
+};
+
+
 // DescriptorArrays are fixed arrays used to hold instance descriptors.
 // The format of the these objects is:
 // 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).
 //   [0]: storage for bit_field3 for Map owning this object (Smi)
 //   [1]: point to a fixed array with (value, detail) pairs.
 //   [2]: next enumeration index (Smi), or pointer to small fixed array:
 //          [0]: next enumeration index (Smi)
 //          [1]: pointer to fixed array with enum cache
@@ skipping 1701 matching lines @@
 
   inline JSObject::ElementsKind elements_kind() {
     return static_cast<JSObject::ElementsKind>(
         (bit_field2() & kElementsKindMask) >> kElementsKindShift);
   }
 
   inline bool has_fast_elements() {
     return elements_kind() == JSObject::FAST_ELEMENTS;
   }
 
+  inline bool has_fast_double_elements() {
+    return elements_kind() == JSObject::FAST_DOUBLE_ELEMENTS;
+  }
+
   inline bool has_external_array_elements() {
     JSObject::ElementsKind kind(elements_kind());
     return kind >= JSObject::FIRST_EXTERNAL_ARRAY_ELEMENTS_KIND &&
         kind <= JSObject::LAST_EXTERNAL_ARRAY_ELEMENTS_KIND;
   }
 
   // Tells whether the map is attached to SharedFunctionInfo
   // (for inobject slack tracking).
   inline void set_attached_to_shared_function_info(bool value);
 
@@ skipping 52 matching lines @@
 
   MUST_USE_RESULT MaybeObject* CopyDropDescriptors();
 
   MUST_USE_RESULT MaybeObject* CopyNormalized(PropertyNormalizationMode mode,
                                               NormalizedMapSharingMode sharing);
 
   // Returns a copy of the map, with all transitions dropped from the
   // instance descriptors.
   MUST_USE_RESULT MaybeObject* CopyDropTransitions();
 
-  // Returns this map if it has the fast elements bit set, otherwise
+  // Returns this map if it already has elements that are fast, otherwise
   // returns a copy of the map, with all transitions dropped from the
   // descriptors and the fast elements bit set.
   MUST_USE_RESULT inline MaybeObject* GetFastElementsMap();
 
-  // Returns this map if it has the fast elements bit cleared,
-  // otherwise returns a copy of the map, with all transitions dropped
-  // from the descriptors and the fast elements bit cleared.
+  // Returns this map if it already has fast elements that are doubles,
+  // otherwise returns a copy of the map, with all transitions dropped from the
+  // descriptors and the fast elements bit set.

[Mads Ager (chromium), 2011/06/06 07:58:23]

These comments should be updated? The fast elements bit is no longer a bit but a
complete elements type, right?

[danno, 2011/06/08 12:09:43]

Done.

+  MUST_USE_RESULT inline MaybeObject* GetFastDoubleElementsMap();
+
+  // Returns this map if already has dictionary elements, otherwise returns a
+  // copy of the map, with all transitions dropped from the descriptors and the
+  // fast elements bit cleared.
   MUST_USE_RESULT inline MaybeObject* GetSlowElementsMap();
 
   // Returns a new map with all transitions dropped from the descriptors and the
   // external array elements bit set.
   MUST_USE_RESULT MaybeObject* GetExternalArrayElementsMap(
       ExternalArrayType array_type,
       bool safe_to_add_transition);
 
   // Returns the property index for name (only valid for FAST MODE).
   int PropertyIndexFor(String* name);
@@ skipping 3003 matching lines @@
     } else {
       value &= ~(1 << bit_position);
     }
     return value;
   }
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_OBJECTS_H_