Speed-up 'new TypedArray(arrayLike)'.

Handle specially the cases when the argument is a typed array,
in particular of the same type as the one we create.

Allocate backing store uninitialized in cases when we can guarantee
complete initialization.

R=bmeurer@chromium.org

Review URL: https://codereview.chromium.org/21369002

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@15998 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

include/v8.h

@@ -2410,8 +2410,20 @@ class V8EXPORT ArrayBuffer : public Object {
 
     /**
      * Allocate |length| bytes. Return NULL if allocation is not successful.
+     * Memory should be initialized to zeroes.
      */
     virtual void* Allocate(size_t length) = 0;
+
+    /**
+     * Allocate |length| bytes. Return NULL if allocation is not successful.
+     * Memory does not have to be initialized.
+     */
+    virtual void* AllocateUninitialized(size_t length) {
+      // Override with call to |Allocate| for compatibility
+      // with legacy version.
+      return Allocate(length);
+    }
+
     /**
      * Free the memory pointed to |data|. That memory is guaranteed to be
      * previously allocated by |Allocate|.

src/d8.cc

@@ -1562,7 +1562,14 @@ static void SetStandaloneFlagsViaCommandLine() {
 
 class ShellArrayBufferAllocator : public v8::ArrayBuffer::Allocator {
  public:
-  virtual void* Allocate(size_t length) { return malloc(length); }
+  virtual void* Allocate(size_t length) {
+    void* result = malloc(length);
+    memset(result, 0, length);
+    return result;
+  }
+  virtual void* AllocateUninitialized(size_t length) {
+    return malloc(length);
+  }
   virtual void Free(void* data) { free(data); }
 };
 

src/runtime.cc

@@ -712,13 +712,18 @@ void Runtime::SetupArrayBuffer(Isolate* isolate,
 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;
   }
@@ -805,65 +810,69 @@ enum TypedArrayId {
   ARRAY_ID_UINT8C = 9
 };
 
-
-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;
+static void ArrayIdToTypeAndSize(
+    int arrayId, ExternalArrayType* array_type, size_t* element_size) {
   switch (arrayId) {
     case ARRAY_ID_UINT8:
-      arrayType = kExternalUnsignedByteArray;
-      elementSize = 1;
+      *array_type = kExternalUnsignedByteArray;
+      *element_size = 1;
       break;
     case ARRAY_ID_INT8:
-      arrayType = kExternalByteArray;
-      elementSize = 1;
+      *array_type = kExternalByteArray;
+      *element_size = 1;
       break;
     case ARRAY_ID_UINT16:
-      arrayType = kExternalUnsignedShortArray;
-      elementSize = 2;
+      *array_type = kExternalUnsignedShortArray;
+      *element_size = 2;
       break;
     case ARRAY_ID_INT16:
-      arrayType = kExternalShortArray;
-      elementSize = 2;
+      *array_type = kExternalShortArray;
+      *element_size = 2;
       break;
     case ARRAY_ID_UINT32:
-      arrayType = kExternalUnsignedIntArray;
-      elementSize = 4;
+      *array_type = kExternalUnsignedIntArray;
+      *element_size = 4;
       break;
     case ARRAY_ID_INT32:
-      arrayType = kExternalIntArray;
-      elementSize = 4;
+      *array_type = kExternalIntArray;
+      *element_size = 4;
       break;
     case ARRAY_ID_FLOAT32:
-      arrayType = kExternalFloatArray;
-      elementSize = 4;
+      *array_type = kExternalFloatArray;
+      *element_size = 4;
       break;
     case ARRAY_ID_FLOAT64:
-      arrayType = kExternalDoubleArray;
-      elementSize = 8;
+      *array_type = kExternalDoubleArray;
+      *element_size = 8;
       break;
     case ARRAY_ID_UINT8C:
-      arrayType = kExternalPixelArray;
-      elementSize = 1;
+      *array_type = kExternalPixelArray;
+      *element_size = 1;
       break;
     default:
       UNREACHABLE();
-      return NULL;
   }
+}
+
+
+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 array_type;
+  size_t element_size;
+  ArrayIdToTypeAndSize(arrayId, &array_type, &element_size);
 
   holder->set_buffer(*buffer);
   holder->set_byte_offset(*byte_offset_object);
@@ -871,8 +880,8 @@ RUNTIME_FUNCTION(MaybeObject*, Runtime_TypedArrayInitialize) {
 
   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);
@@ -881,13 +890,99 @@ RUNTIME_FUNCTION(MaybeObject*, Runtime_TypedArrayInitialize) {
 
   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 source 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);                                               \

src/runtime.h

@@ -361,6 +361,7 @@ namespace internal {
   F(ArrayBufferSliceImpl, 3, 1) \
   \
   F(TypedArrayInitialize, 5, 1) \
+  F(TypedArrayInitializeFromArrayLike, 4, 1) \
   F(TypedArrayGetBuffer, 1, 1) \
   F(TypedArrayGetByteLength, 1, 1) \
   F(TypedArrayGetByteOffset, 1, 1) \
@@ -784,7 +785,8 @@ class Runtime : public AllStatic {
   static bool SetupArrayBufferAllocatingData(
       Isolate* isolate,
       Handle<JSArrayBuffer> array_buffer,
-      size_t allocated_length);
+      size_t allocated_length,
+      bool initialize = true);
 
   static void FreeArrayBuffer(
       Isolate* isolate,

src/typedarray.js

@@ -77,11 +77,10 @@ function CreateTypedArrayConstructor(name, elementSize, arrayId, constructor) {
   function ConstructByArrayLike(obj, arrayLike) {
     var length = arrayLike.length;
     var l =  ToPositiveInteger(length, "invalid_typed_array_length");
-    var byteLength = l * elementSize;
-    var buffer = new $ArrayBuffer(byteLength);
-    %TypedArrayInitialize(obj, arrayId, buffer, 0, byteLength);
-    for (var i = 0; i < l; i++) {
-      obj[i] = arrayLike[i];
+    if(!%TypedArrayInitializeFromArrayLike(obj, arrayId, arrayLike, l)) {
+      for (var i = 0; i < l; i++) {
+        obj[i] = arrayLike[i];
+      }
     }
   }