[Ignition/turbo] Add a NewWithSpread bytecode.

src/runtime/runtime-classes.cc

Index: src/runtime/runtime-classes.cc
diff --git a/src/runtime/runtime-classes.cc b/src/runtime/runtime-classes.cc
index aafd7779870f74cbd9bc2e5380b79f4842e8638b..f62e112b7223b7ab82fccb83711c79e36a4631f3 100644
--- a/src/runtime/runtime-classes.cc
+++ b/src/runtime/runtime-classes.cc
@@ -388,5 +388,47 @@ RUNTIME_FUNCTION(Runtime_GetSuperConstructor) {
   return active_function->map()->prototype();
 }
 
+RUNTIME_FUNCTION(Runtime_NewWithSpread) {
+  HandleScope scope(isolate);
+  DCHECK_LE(3, args.length());
+  CONVERT_ARG_HANDLE_CHECKED(JSReceiver, constructor, 0);
+  CONVERT_ARG_HANDLE_CHECKED(Object, new_target, 1);
+
+  int constructor_argc = args.length() - 2;
+  CONVERT_ARG_HANDLE_CHECKED(Object, spread, args.length() - 1);
+
+  // Iterate over the spread if we need to.
+  if (spread->IterationHasObservableEffects()) {
+    Handle<JSFunction> spread_iterable_function = isolate->spread_iterable();
+    ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
+        isolate, spread,
+        Execution::Call(isolate, spread_iterable_function,
+                        isolate->factory()->undefined_value(), 1, &spread));
+  }
+
+  uint32_t spread_length;
+  Handle<JSArray> spread_array = Handle<JSArray>::cast(spread);
+  CHECK(spread_array->length()->ToArrayIndex(&spread_length));
+  int result_length = constructor_argc - 1 + spread_length;
+  ScopedVector<Handle<Object>> construct_args(result_length);
+
+  // Append each of the individual args to the result.
+  for (int i = 0; i < constructor_argc - 1; i++) {
+    construct_args[i] = args.at<Object>(2 + i);
+  }
+
+  // Append element of the spread to the result.
+  for (uint32_t i = 0; i < spread_length; i++) {

[Benedikt Meurer, 2016/12/07 07:32:40]

Can you add a TODO here to eventually use ElementAccessors here if the C++
implementation sticks? I.e. if we still need a C++ fallback even once we turn
the fast-paths into a TFS.

+    LookupIterator it(isolate, spread, i);
+    Handle<Object> element = spread_array->GetDataProperty(&it);
+    construct_args[constructor_argc - 1 + i] = element;
+  }
+
+  // Call the constructor.
+  RETURN_RESULT_OR_FAILURE(
+      isolate, Execution::New(isolate, constructor, new_target, result_length,
+                              construct_args.start()));
+}
+
 }  // namespace internal
 }  // namespace v8