Preallocate transitioned maps for TypedArrays.

src/heap.h

 // Copyright 2012 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 119 matching lines @@
   V(Map, undetectable_ascii_string_map, UndetectableAsciiStringMap)            \
   V(Map, external_pixel_array_map, ExternalPixelArrayMap)                      \
   V(Map, external_byte_array_map, ExternalByteArrayMap)                        \
   V(Map, external_unsigned_byte_array_map, ExternalUnsignedByteArrayMap)       \
   V(Map, external_short_array_map, ExternalShortArrayMap)                      \
   V(Map, external_unsigned_short_array_map, ExternalUnsignedShortArrayMap)     \
   V(Map, external_int_array_map, ExternalIntArrayMap)                          \
   V(Map, external_unsigned_int_array_map, ExternalUnsignedIntArrayMap)         \
   V(Map, external_float_array_map, ExternalFloatArrayMap)                      \
   V(Map, external_double_array_map, ExternalDoubleArrayMap)                    \
+  V(ExternalArray, empty_external_pixel_array,                                 \
+      EmptyExternalPixelArray)                                                 \

[Hannes Payer (out of office), 2013/05/15 14:14:17]

Can we move empty_external_pixel_array after empty_external_double_array which
would preserve the order defined in elements-kind.h?

+  V(ExternalArray, empty_external_byte_array,                                  \
+      EmptyExternalByteArray)                                                  \
+  V(ExternalArray, empty_external_unsigned_byte_array,                         \
+      EmptyExternalUnsignedByteArray)                                          \
+  V(ExternalArray, empty_external_short_array, EmptyExternalShortArray)        \
+  V(ExternalArray, empty_external_unsigned_short_array,                        \
+      EmptyExternalUnsignedShortArray)                                         \
+  V(ExternalArray, empty_external_int_array, EmptyExternalIntArray)            \
+  V(ExternalArray, empty_external_unsigned_int_array,                          \
+      EmptyExternalUnsignedIntArray)                                           \
+  V(ExternalArray, empty_external_float_array, EmptyExternalFloatArray)        \
+  V(ExternalArray, empty_external_double_array, EmptyExternalDoubleArray)      \
   V(Map, non_strict_arguments_elements_map, NonStrictArgumentsElementsMap)     \
   V(Map, function_context_map, FunctionContextMap)                             \
   V(Map, catch_context_map, CatchContextMap)                                   \
   V(Map, with_context_map, WithContextMap)                                     \
   V(Map, block_context_map, BlockContextMap)                                   \
   V(Map, module_context_map, ModuleContextMap)                                 \
   V(Map, global_context_map, GlobalContextMap)                                 \
   V(Map, oddball_map, OddballMap)                                              \
   V(Map, message_object_map, JSMessageObjectMap)                               \
   V(Map, foreign_map, ForeignMap)                                              \
@@ skipping 1469 matching lines @@
   MUST_USE_RESULT MaybeObject* NumberToString(
       Object* number, bool check_number_string_cache = true,
       PretenureFlag pretenure = NOT_TENURED);
   MUST_USE_RESULT MaybeObject* Uint32ToString(
       uint32_t value, bool check_number_string_cache = true);
 
   Map* MapForExternalArrayType(ExternalArrayType array_type);
   RootListIndex RootIndexForExternalArrayType(
       ExternalArrayType array_type);
 
+  RootListIndex RootIndexForEmptyExternalArray(ElementsKind kind);
+  ExternalArray* EmptyExternalArrayForMap(Map* map);
+
   void RecordStats(HeapStats* stats, bool take_snapshot = false);
 
   // Copy block of memory from src to dst. Size of block should be aligned
   // by pointer size.
   static inline void CopyBlock(Address dst, Address src, int byte_size);
 
   // Optimized version of memmove for blocks with pointer size aligned sizes and
   // pointer size aligned addresses.
   static inline void MoveBlock(Address dst, Address src, int byte_size);
 
@@ skipping 494 matching lines @@
       ElementsKind elements_kind,
       PretenureFlag pretenure = NOT_TENURED);
 
   MUST_USE_RESULT MaybeObject* AllocateJSArrayWithAllocationSite(
       ElementsKind elements_kind,
       Handle<Object> allocation_site_info_payload);
 
   // Allocate empty fixed array.
   MUST_USE_RESULT MaybeObject* AllocateEmptyFixedArray();
 
+  // Allocate empty external array of given type.
+  MUST_USE_RESULT MaybeObject* AllocateEmptyExternalArray(
+      ExternalArrayType array_type);
+
   // Allocate empty fixed double array.
   MUST_USE_RESULT MaybeObject* AllocateEmptyFixedDoubleArray();
 
   // Performs a minor collection in new generation.
   void Scavenge();
 
   static String* UpdateNewSpaceReferenceInExternalStringTableEntry(
       Heap* heap,
       Object** pointer);
 
@@ skipping 925 matching lines @@
   AssertNoAllocation no_alloc;  // i.e. no gc allowed.
 
  private:
   DISALLOW_IMPLICIT_CONSTRUCTORS(PathTracer);
 };
 #endif  // DEBUG
 
 } }  // namespace v8::internal
 
 #endif  // V8_HEAP_H_