Various species micro-optimizations

src/isolate-inl.h

 // Copyright 2015 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.
 
 #ifndef V8_ISOLATE_INL_H_
 #define V8_ISOLATE_INL_H_
 
 #include "src/isolate.h"
 #include "src/objects-inl.h"
 
@@ skipping 83 matching lines @@
 #define NATIVE_CONTEXT_FIELD_ACCESSOR(index, type, name) \
   Handle<type> Isolate::name() {                         \
     return Handle<type>(native_context()->name(), this); \
   }                                                      \
   bool Isolate::is_##name(type* value) {                 \
     return native_context()->is_##name(value);           \
   }
 NATIVE_CONTEXT_FIELDS(NATIVE_CONTEXT_FIELD_ACCESSOR)
 #undef NATIVE_CONTEXT_FIELD_ACCESSOR
 
+bool Isolate::IsArraySpeciesLookupChainIntact() {
+  if (!FLAG_harmony_species) return true;
+  // Note: It would be nice to have debug checks to make sure that the
+  // species protector is accurate, but this would be hard to do for most of
+  // what the protector stands for:
+  // - You'd need to traverse the heap to check that no Array instance has
+  //   a constructor property
+  // - To check that Array[Symbol.species] == Array, JS code has to execute,
+  //   but JS cannot be invoked in callstack overflow situations
+  // All that could be checked reliably is that
+  // Array.prototype.constructor == Array. Given that limitation, no check is
+  // done here. In place, there are mjsunit tests harmony/array-species* which
+  // ensure that behavior is correct in various invalid protector cases.
+
+  PropertyCell* species_cell = heap()->species_protector();
+  return species_cell->value()->IsSmi() &&
+         Smi::cast(species_cell->value())->value() == kArrayProtectorValid;
+}
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_ISOLATE_INL_H_