Reimplement TypedArray.set in Javascript.

src/runtime.cc

Index: src/runtime.cc
diff --git a/src/runtime.cc b/src/runtime.cc
index ed3527fa9202cb9977101725598cec30b3af1bba..2cbaad10fc8566914961340cbb9a9889c47cede1 100644
--- a/src/runtime.cc
+++ b/src/runtime.cc
@@ -907,6 +907,21 @@ TYPED_ARRAY_GETTER(Length, length)
 
 #undef TYPED_ARRAY_GETTER
 
+// Return codes for Runtime_TypedArraySetFastCases.
+// Should be synchronized with typedarray.js natives.
+enum TypedArraySetResultCodes {
+  // Set from typed array of the same type.
+  // This is processed by TypedArraySetFastCases
+  TYPED_ARRAY_SET_TYPED_ARRAY_SAME_TYPE = 0,
+  // Set from typed array of the different type, overlapping in memory.
+  TYPED_ARRAY_SET_TYPED_ARRAY_OVERLAPPING = 1,
+  // Set from typed array of the different type, non-overlapping.
+  TYPED_ARRAY_SET_TYPED_ARRAY_NONOVERLAPPING = 2,
+  // Set from non-typed array.
+  TYPED_ARRAY_SET_NON_TYPED_ARRAY = 3
+};
+
+
 RUNTIME_FUNCTION(MaybeObject*, Runtime_TypedArraySetFastCases) {
   HandleScope scope(isolate);
   CONVERT_ARG_HANDLE_CHECKED(Object, target_obj, 0);
@@ -918,7 +933,7 @@ RUNTIME_FUNCTION(MaybeObject*, Runtime_TypedArraySetFastCases) {
         "not_typed_array", HandleVector<Object>(NULL, 0)));
 
   if (!source_obj->IsJSTypedArray())
-    return isolate->heap()->false_value();
+    return Smi::FromInt(TYPED_ARRAY_SET_NON_TYPED_ARRAY);
 
   Handle<JSTypedArray> target(JSTypedArray::cast(*target_obj));
   Handle<JSTypedArray> source(JSTypedArray::cast(*source_obj));
@@ -933,20 +948,20 @@ RUNTIME_FUNCTION(MaybeObject*, Runtime_TypedArraySetFastCases) {
     return isolate->Throw(*isolate->factory()->NewRangeError(
           "typed_array_set_source_too_large", HandleVector<Object>(NULL, 0)));
 
-  Handle<JSArrayBuffer> target_buffer(JSArrayBuffer::cast(target->buffer()));
-  Handle<JSArrayBuffer> source_buffer(JSArrayBuffer::cast(source->buffer()));
   size_t target_offset = NumberToSize(isolate, target->byte_offset());
   size_t source_offset = NumberToSize(isolate, source->byte_offset());
   uint8_t* target_base =
-      static_cast<uint8_t*>(target_buffer->backing_store()) + target_offset;
+      static_cast<uint8_t*>(
+        JSArrayBuffer::cast(target->buffer())->backing_store()) + target_offset;
   uint8_t* source_base =
-      static_cast<uint8_t*>(source_buffer->backing_store()) + source_offset;
+      static_cast<uint8_t*>(
+        JSArrayBuffer::cast(source->buffer())->backing_store()) + source_offset;
 
   // Typed arrays of the same type: use memmove.
   if (target->type() == source->type()) {
     memmove(target_base + offset * target->element_size(),
         source_base, source_byte_length);
-    return isolate->heap()->true_value();
+    return Smi::FromInt(TYPED_ARRAY_SET_TYPED_ARRAY_SAME_TYPE);
   }
 
   // Typed arrays of different types over the same backing store
@@ -954,78 +969,14 @@ RUNTIME_FUNCTION(MaybeObject*, Runtime_TypedArraySetFastCases) {
         source_base + source_byte_length > target_base) ||
       (target_base <= source_base &&
         target_base + target_byte_length > source_base)) {
-    size_t target_element_size = target->element_size();
-    size_t source_element_size = source->element_size();
-
-    size_t source_length = NumberToSize(isolate, source->length());
-
-    // Copy left part
-    size_t left_index;
-    {
-      // First un-mutated byte after the next write
-      uint8_t* target_ptr = target_base + (offset + 1) * target_element_size;
-      // Next read at source_ptr. We do not care for memory changing before
-      // source_ptr - we have already copied it.
-      uint8_t* source_ptr = source_base;
-      for (left_index = 0;
-           left_index < source_length && target_ptr <= source_ptr;
-           left_index++) {
-        Handle<Object> v = Object::GetElement(
-            source, static_cast<uint32_t>(left_index));
-        JSObject::SetElement(
-            target, static_cast<uint32_t>(offset + left_index), v,
-            NONE, kNonStrictMode);
-        target_ptr += target_element_size;
-        source_ptr += source_element_size;
-      }
-    }
-    // Copy right part
-    size_t right_index;
-    {
-      // First unmutated byte before the next write
-      uint8_t* target_ptr =
-        target_base + (offset + source_length - 1) * target_element_size;
-      // Next read before source_ptr. We do not care for memory changing after
-      // source_ptr - we have already copied it.
-      uint8_t* source_ptr =
-        source_base + source_length * source_element_size;
-      for (right_index = source_length - 1;
-           right_index >= left_index && target_ptr >= source_ptr;
-           right_index--) {
-        Handle<Object> v = Object::GetElement(
-            source, static_cast<uint32_t>(right_index));
-        JSObject::SetElement(
-            target, static_cast<uint32_t>(offset + right_index), v,
-            NONE, kNonStrictMode);
-        target_ptr -= target_element_size;
-        source_ptr -= source_element_size;
-      }
-    }
-    // There can be at most 8 entries left in the middle that need buffering
-    // (because the largest element_size is 8 times the smallest).
-    ASSERT((right_index + 1) - left_index <= 8);
-    Handle<Object> temp[8];
-    size_t idx;
-    for (idx = left_index; idx <= right_index; idx++) {
-      temp[idx - left_index] = Object::GetElement(
-          source, static_cast<uint32_t>(idx));
-    }
-    for (idx = left_index; idx <= right_index; idx++) {
-      JSObject::SetElement(
-          target, static_cast<uint32_t>(offset + idx), temp[idx-left_index],
-          NONE, kNonStrictMode);
-    }
+    // We do not support overlapping ArrayBuffers
+    ASSERT(
+      JSArrayBuffer::cast(target->buffer())->backing_store() ==
+      JSArrayBuffer::cast(source->buffer())->backing_store());
+    return Smi::FromInt(TYPED_ARRAY_SET_TYPED_ARRAY_OVERLAPPING);
   } else {  // Non-overlapping typed arrays
-    for (size_t idx = 0; idx < source_length; idx++) {
-      Handle<Object> value = Object::GetElement(
-          source, static_cast<uint32_t>(idx));
-      JSObject::SetElement(
-          target, static_cast<uint32_t>(offset + idx), value,
-          NONE, kNonStrictMode);
-    }
+    return Smi::FromInt(TYPED_ARRAY_SET_TYPED_ARRAY_NONOVERLAPPING);
   }
-
-  return isolate->heap()->true_value();
 }