[runtime] Introduce maps for the likely cases of FromPropertyDescriptor.

src/bootstrapper.cc

 // Copyright 2014 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/bootstrapper.h"
 
 #include "src/accessors.h"
 #include "src/api-natives.h"
 #include "src/code-stubs.h"
 #include "src/extensions/externalize-string-extension.h"
@@ skipping 2710 matching lines @@
     JSFunction::EnsureHasInitialMap(function);
     function->initial_map()->set_instance_type(JS_PROMISE_TYPE);
     function->shared()->set_construct_stub(
         *isolate()->builtins()->JSBuiltinsConstructStub());
     InstallWithIntrinsicDefaultProto(isolate(), function,
                                      Context::PROMISE_FUNCTION_INDEX);
   }
 
   InstallBuiltinFunctionIds();
 
+  // Create a map for accessor property descriptors (a variant of JSObject
+  // that predefines four properties get, set, configurable and enumerable).
+  {
+    // AccessorPropertyDescriptor initial map.
+    Handle<Map> map =
+        factory()->NewMap(JS_OBJECT_TYPE, JSAccessorPropertyDescriptor::kSize);
+    // Create the descriptor array for the property descriptor object.
+    Map::EnsureDescriptorSlack(map, 4);
+
+    {  // get
+      DataDescriptor d(factory()->get_string(),
+                       JSAccessorPropertyDescriptor::kGetIndex, NONE,
+                       Representation::Tagged());
+      map->AppendDescriptor(&d);
+    }
+    {  // set
+      DataDescriptor d(factory()->set_string(),
+                       JSAccessorPropertyDescriptor::kSetIndex, NONE,
+                       Representation::Tagged());
+      map->AppendDescriptor(&d);
+    }
+    {  // enumerable
+      DataDescriptor d(factory()->enumerable_string(),
+                       JSAccessorPropertyDescriptor::kEnumerableIndex, NONE,
+                       Representation::Tagged());
+      map->AppendDescriptor(&d);
+    }
+    {  // configurable
+      DataDescriptor d(factory()->configurable_string(),
+                       JSAccessorPropertyDescriptor::kConfigurableIndex, NONE,
+                       Representation::Tagged());
+      map->AppendDescriptor(&d);
+    }
+
+    Map::SetPrototype(map, isolate()->initial_object_prototype());
+    map->SetInObjectProperties(4);
+    map->set_unused_property_fields(0);
+
+    native_context()->set_accessor_property_descriptor_map(*map);
+  }
+
+  // Create a map for data property descriptors (a variant of JSObject
+  // that predefines four properties value, writable, configurable and
+  // enumerable).
+  {
+    // DataPropertyDescriptor initial map.
+    Handle<Map> map =
+        factory()->NewMap(JS_OBJECT_TYPE, JSDataPropertyDescriptor::kSize);
+    // Create the descriptor array for the property descriptor object.
+    Map::EnsureDescriptorSlack(map, 4);
+
+    {  // value
+      DataDescriptor d(factory()->value_string(),
+                       JSDataPropertyDescriptor::kValueIndex, NONE,
+                       Representation::Tagged());
+      map->AppendDescriptor(&d);
+    }
+    {  // writable
+      DataDescriptor d(factory()->writable_string(),
+                       JSDataPropertyDescriptor::kWritableIndex, NONE,
+                       Representation::Tagged());
+      map->AppendDescriptor(&d);
+    }
+    {  // enumerable
+      DataDescriptor d(factory()->enumerable_string(),
+                       JSDataPropertyDescriptor::kEnumerableIndex, NONE,
+                       Representation::Tagged());
+      map->AppendDescriptor(&d);
+    }
+    {  // configurable
+      DataDescriptor d(factory()->configurable_string(),
+                       JSDataPropertyDescriptor::kConfigurableIndex, NONE,
+                       Representation::Tagged());
+      map->AppendDescriptor(&d);
+    }
+
+    Map::SetPrototype(map, isolate()->initial_object_prototype());
+    map->SetInObjectProperties(4);
+    map->set_unused_property_fields(0);
+
+    native_context()->set_data_property_descriptor_map(*map);
+  }
+
   // Create a constructor for RegExp results (a variant of Array that
   // predefines the two properties index and match).
   {
     // RegExpResult initial map.
 
     // Find global.Array.prototype to inherit from.
     Handle<JSFunction> array_constructor(native_context()->array_function());
     Handle<JSObject> array_prototype(
         JSObject::cast(array_constructor->instance_prototype()));
 
@@ skipping 782 matching lines @@
 }
 
 
 // Called when the top-level V8 mutex is destroyed.
 void Bootstrapper::FreeThreadResources() {
   DCHECK(!IsActive());
 }
 
 }  // namespace internal
 }  // namespace v8