Optimize @@species based on a global 'protector' cell

src/builtins.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/builtins.h"
 
 #include "src/api.h"
 #include "src/api-natives.h"
 #include "src/arguments.h"
 #include "src/base/once.h"
@@ skipping 465 matching lines @@
 BUILTIN(ArraySlice) {
   HandleScope scope(isolate);
   Handle<Object> receiver = args.receiver();
   Handle<JSObject> object;
   Handle<FixedArrayBase> elms_obj;
   int len = -1;
   int relative_start = 0;
   int relative_end = 0;
   bool is_sloppy_arguments = false;
 
-  // TODO(littledan): Look up @@species only once, not once here and
-  // again in the JS builtin. Pass the species out?
-  Handle<Object> species;
-  ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
-      isolate, species, Object::ArraySpeciesConstructor(isolate, receiver));
-  if (*species != isolate->context()->native_context()->array_function()) {
-    return CallJsIntrinsic(isolate, isolate->array_slice(), args);
-  }
   if (receiver->IsJSArray()) {
     DisallowHeapAllocation no_gc;
     JSArray* array = JSArray::cast(*receiver);
     if (!array->HasFastElements() ||
-        !IsJSArrayFastElementMovingAllowed(isolate, array)) {
+        !IsJSArrayFastElementMovingAllowed(isolate, array) ||
+        !isolate->IsArraySpeciesLookupChainIntact() ||
+        // If this is a subclass of Array, then call out to JS
+        !array->map()->new_target_is_base()) {
       AllowHeapAllocation allow_allocation;
       return CallJsIntrinsic(isolate, isolate->array_slice(), args);
     }
     len = Smi::cast(array->length())->value();
     object = Handle<JSObject>::cast(receiver);
     elms_obj = handle(array->elements(), isolate);
   } else if (receiver->IsJSObject() &&
              GetSloppyArgumentsLength(isolate, Handle<JSObject>::cast(receiver),
                                       &len)) {
     // Array.prototype.slice(arguments, ...) is quite a common idiom
@@ skipping 57 matching lines @@
   return *result_array;
 }
 
 
 BUILTIN(ArraySplice) {
   HandleScope scope(isolate);
   Handle<Object> receiver = args.receiver();
   MaybeHandle<FixedArrayBase> maybe_elms_obj =
       EnsureJSArrayWithWritableFastElements(isolate, receiver, &args, 3);
   Handle<FixedArrayBase> elms_obj;
-  if (!maybe_elms_obj.ToHandle(&elms_obj)) {
-    return CallJsIntrinsic(isolate, isolate->array_splice(), args);
-  }
-  // TODO(littledan): Look up @@species only once, not once here and
-  // again in the JS builtin. Pass the species out?
-  Handle<Object> species;
-  ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
-      isolate, species, Object::ArraySpeciesConstructor(isolate, receiver));
-  if (*species != isolate->context()->native_context()->array_function()) {
+  if (!maybe_elms_obj.ToHandle(&elms_obj) ||
+      // If this is a subclass of Array, then call out to JS
+      !JSArray::cast(*receiver)->map()->new_target_is_base() ||
+      // If anything with @@species has been messed with, call out to JS
+      !isolate->IsArraySpeciesLookupChainIntact()) {
     return CallJsIntrinsic(isolate, isolate->array_splice(), args);
   }
   Handle<JSArray> array = Handle<JSArray>::cast(receiver);
   DCHECK(!array->map()->is_observed());
 
   int argument_count = args.length() - 1;
   int relative_start = 0;
   if (argument_count > 0) {
     DisallowHeapAllocation no_gc;
     if (!ClampedToInteger(args[1], &relative_start)) {
@@ skipping 3852 matching lines @@
 BUILTIN_LIST_C(DEFINE_BUILTIN_ACCESSOR_C)
 BUILTIN_LIST_A(DEFINE_BUILTIN_ACCESSOR_A)
 BUILTIN_LIST_H(DEFINE_BUILTIN_ACCESSOR_H)
 BUILTIN_LIST_DEBUG_A(DEFINE_BUILTIN_ACCESSOR_A)
 #undef DEFINE_BUILTIN_ACCESSOR_C
 #undef DEFINE_BUILTIN_ACCESSOR_A
 
 
 }  // namespace internal
 }  // namespace v8