Speed-up 'new TypedArray(arrayLike)'.

src/runtime.cc

 // 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 694 matching lines @@
 
   array_buffer->set_weak_next(isolate->heap()->array_buffers_list());
   isolate->heap()->set_array_buffers_list(*array_buffer);
   array_buffer->set_weak_first_view(isolate->heap()->undefined_value());
 }
 
 
 bool Runtime::SetupArrayBufferAllocatingData(
     Isolate* isolate,
     Handle<JSArrayBuffer> array_buffer,
-    size_t allocated_length) {
+    size_t allocated_length,
+    bool initialize) {
   void* data;
   CHECK(V8::ArrayBufferAllocator() != NULL);
   if (allocated_length != 0) {
-    data = V8::ArrayBufferAllocator()->Allocate(allocated_length);
+    if (initialize) {
+      data = V8::ArrayBufferAllocator()->Allocate(allocated_length);
+    } else {
+      data =
+        V8::ArrayBufferAllocator()->AllocateUninitialized(allocated_length);
+    }
     if (data == NULL) return false;
-    memset(data, 0, allocated_length);
   } else {
     data = NULL;
   }
 
   SetupArrayBuffer(isolate, array_buffer, false, data, allocated_length);
 
   isolate->heap()->AdjustAmountOfExternalAllocatedMemory(allocated_length);
 
   return true;
 }
@@ skipping 66 matching lines @@
   ARRAY_ID_INT8 = 2,
   ARRAY_ID_UINT16 = 3,
   ARRAY_ID_INT16 = 4,
   ARRAY_ID_UINT32 = 5,
   ARRAY_ID_INT32 = 6,
   ARRAY_ID_FLOAT32 = 7,
   ARRAY_ID_FLOAT64 = 8,
   ARRAY_ID_UINT8C = 9
 };
 
+static void ArrayIdToTypeAndSize(
+    int arrayId, ExternalArrayType* array_type, size_t* element_size) {
+  switch (arrayId) {
+    case ARRAY_ID_UINT8:
+      *array_type = kExternalUnsignedByteArray;
+      *element_size = 1;
+      break;
+    case ARRAY_ID_INT8:
+      *array_type = kExternalByteArray;
+      *element_size = 1;
+      break;
+    case ARRAY_ID_UINT16:
+      *array_type = kExternalUnsignedShortArray;
+      *element_size = 2;
+      break;
+    case ARRAY_ID_INT16:
+      *array_type = kExternalShortArray;
+      *element_size = 2;
+      break;
+    case ARRAY_ID_UINT32:
+      *array_type = kExternalUnsignedIntArray;
+      *element_size = 4;
+      break;
+    case ARRAY_ID_INT32:
+      *array_type = kExternalIntArray;
+      *element_size = 4;
+      break;
+    case ARRAY_ID_FLOAT32:
+      *array_type = kExternalFloatArray;
+      *element_size = 4;
+      break;
+    case ARRAY_ID_FLOAT64:
+      *array_type = kExternalDoubleArray;
+      *element_size = 8;
+      break;
+    case ARRAY_ID_UINT8C:
+      *array_type = kExternalPixelArray;
+      *element_size = 1;
+      break;
+    default:
+      UNREACHABLE();
+  }
+}
+
 
 RUNTIME_FUNCTION(MaybeObject*, Runtime_TypedArrayInitialize) {
   HandleScope scope(isolate);
   ASSERT(args.length() == 5);
   CONVERT_ARG_HANDLE_CHECKED(JSTypedArray, holder, 0);
   CONVERT_SMI_ARG_CHECKED(arrayId, 1);
   CONVERT_ARG_HANDLE_CHECKED(JSArrayBuffer, buffer, 2);
   CONVERT_ARG_HANDLE_CHECKED(Object, byte_offset_object, 3);
   CONVERT_ARG_HANDLE_CHECKED(Object, byte_length_object, 4);
 
   ASSERT(holder->GetInternalFieldCount() ==
       v8::ArrayBufferView::kInternalFieldCount);
   for (int i = 0; i < v8::ArrayBufferView::kInternalFieldCount; i++) {
     holder->SetInternalField(i, Smi::FromInt(0));
   }
 
-  ExternalArrayType arrayType;
-  size_t elementSize;
-  switch (arrayId) {
-    case ARRAY_ID_UINT8:
-      arrayType = kExternalUnsignedByteArray;
-      elementSize = 1;
-      break;
-    case ARRAY_ID_INT8:
-      arrayType = kExternalByteArray;
-      elementSize = 1;
-      break;
-    case ARRAY_ID_UINT16:
-      arrayType = kExternalUnsignedShortArray;
-      elementSize = 2;
-      break;
-    case ARRAY_ID_INT16:
-      arrayType = kExternalShortArray;
-      elementSize = 2;
-      break;
-    case ARRAY_ID_UINT32:
-      arrayType = kExternalUnsignedIntArray;
-      elementSize = 4;
-      break;
-    case ARRAY_ID_INT32:
-      arrayType = kExternalIntArray;
-      elementSize = 4;
-      break;
-    case ARRAY_ID_FLOAT32:
-      arrayType = kExternalFloatArray;
-      elementSize = 4;
-      break;
-    case ARRAY_ID_FLOAT64:
-      arrayType = kExternalDoubleArray;
-      elementSize = 8;
-      break;
-    case ARRAY_ID_UINT8C:
-      arrayType = kExternalPixelArray;
-      elementSize = 1;
-      break;
-    default:
-      UNREACHABLE();
-      return NULL;
-  }
+  ExternalArrayType array_type;
+  size_t element_size;
+  ArrayIdToTypeAndSize(arrayId, &array_type, &element_size);
 
   holder->set_buffer(*buffer);
   holder->set_byte_offset(*byte_offset_object);
   holder->set_byte_length(*byte_length_object);
 
   size_t byte_offset = NumberToSize(isolate, *byte_offset_object);
   size_t byte_length = NumberToSize(isolate, *byte_length_object);
-  ASSERT(byte_length % elementSize == 0);
-  size_t length = byte_length / elementSize;
+  ASSERT(byte_length % element_size == 0);
+  size_t length = byte_length / element_size;
 
   Handle<Object> length_obj = isolate->factory()->NewNumberFromSize(length);
   holder->set_length(*length_obj);
   holder->set_weak_next(buffer->weak_first_view());
   buffer->set_weak_first_view(*holder);
 
   Handle<ExternalArray> elements =
       isolate->factory()->NewExternalArray(
-          static_cast<int>(length), arrayType,
+          static_cast<int>(length), array_type,
           static_cast<uint8_t*>(buffer->backing_store()) + byte_offset);
   holder->set_elements(*elements);
   return isolate->heap()->undefined_value();
 }
 
 
+// Initializes a typed array from an array-like object.
+// If an array-like object happens to be a typed array of the same type,
+// initializes backing store using memove.
+//
+// Returns true if backing store was initialized or false otherwise.
+RUNTIME_FUNCTION(MaybeObject*, Runtime_TypedArrayInitializeFromArrayLike) {
+  HandleScope scope(isolate);
+  ASSERT(args.length() == 4);
+  CONVERT_ARG_HANDLE_CHECKED(JSTypedArray, holder, 0);
+  CONVERT_SMI_ARG_CHECKED(arrayId, 1);
+  CONVERT_ARG_HANDLE_CHECKED(Object, source, 2);
+  CONVERT_ARG_HANDLE_CHECKED(Object, length_obj, 3);
+
+  ASSERT(holder->GetInternalFieldCount() ==
+      v8::ArrayBufferView::kInternalFieldCount);
+  for (int i = 0; i < v8::ArrayBufferView::kInternalFieldCount; i++) {
+    holder->SetInternalField(i, Smi::FromInt(0));
+  }
+
+  ExternalArrayType array_type;
+  size_t element_size;
+  ArrayIdToTypeAndSize(arrayId, &array_type, &element_size);
+
+  Handle<JSArrayBuffer> buffer = isolate->factory()->NewJSArrayBuffer();
+  size_t length = NumberToSize(isolate, *length_obj);
+  size_t byte_length = length * element_size;
+  if (byte_length < length) {  // Overflow
+    return isolate->Throw(*isolate->factory()->
+          NewRangeError("invalid_array_buffer_length",
+            HandleVector<Object>(NULL, 0)));
+  }
+
+  // We assume that the caller of this function will initialize holder
+  // with the loop
+  //      for(i = 0; i < length; i++) { holder[i] = source[i]; }
+  // If source is a typed array, this loop will always run to completion,
+  // so we are sure that the backing store will be initialized.
+  // Otherwise, we do not know (the indexing operation might throw).
+  // Hence we require zero initialization unless our sourec is a typed array.
+  bool should_zero_initialize = !source->IsJSTypedArray();
+
+  if (!Runtime::SetupArrayBufferAllocatingData(
+        isolate, buffer, byte_length, should_zero_initialize)) {
+    return isolate->Throw(*isolate->factory()->
+          NewRangeError("invalid_array_buffer_length",
+            HandleVector<Object>(NULL, 0)));
+  }
+
+  holder->set_buffer(*buffer);
+  holder->set_byte_offset(Smi::FromInt(0));
+  Handle<Object> byte_length_obj(
+      isolate->factory()->NewNumberFromSize(byte_length));
+  holder->set_byte_length(*byte_length_obj);
+  holder->set_length(*length_obj);
+  holder->set_weak_next(buffer->weak_first_view());
+  buffer->set_weak_first_view(*holder);
+
+  Handle<ExternalArray> elements =
+      isolate->factory()->NewExternalArray(
+          static_cast<int>(length), array_type,
+          static_cast<uint8_t*>(buffer->backing_store()));
+  holder->set_elements(*elements);
+
+  if (source->IsJSTypedArray()) {
+    Handle<JSTypedArray> typed_array(JSTypedArray::cast(*source));
+
+    if (typed_array->type() == holder->type()) {
+      uint8_t* backing_store =
+        static_cast<uint8_t*>(
+          JSArrayBuffer::cast(typed_array->buffer())->backing_store());
+      size_t source_byte_offset =
+          NumberToSize(isolate, typed_array->byte_offset());
+      OS::MemCopy(
+          buffer->backing_store(),
+          backing_store + source_byte_offset,
+          byte_length);
+      return *isolate->factory()->true_value();
+    } else {
+      return *isolate->factory()->false_value();
+    }
+  }
+
+  return *isolate->factory()->false_value();
+}
+
+
 #define TYPED_ARRAY_GETTER(getter, accessor) \
   RUNTIME_FUNCTION(MaybeObject*, Runtime_TypedArrayGet##getter) {             \
     HandleScope scope(isolate);                                               \
     ASSERT(args.length() == 1);                                               \
     CONVERT_ARG_HANDLE_CHECKED(Object, holder, 0);                            \
     if (!holder->IsJSTypedArray())                                            \
       return isolate->Throw(*isolate->factory()->NewTypeError(                \
           "not_typed_array", HandleVector<Object>(NULL, 0)));                 \
     Handle<JSTypedArray> typed_array(JSTypedArray::cast(*holder));            \
     return typed_array->accessor();                                           \
@@ skipping 12957 matching lines @@
     // Handle last resort GC and make sure to allow future allocations
     // to grow the heap without causing GCs (if possible).
     isolate->counters()->gc_last_resort_from_js()->Increment();
     isolate->heap()->CollectAllGarbage(Heap::kNoGCFlags,
                                        "Runtime::PerformGC");
   }
 }
 
 
 } }  // namespace v8::internal