[Map::TransitionToDataProperty speed] Streamline TransitionsAccessor::IsMatchingMap

Should help the case where the single existing transition matches.

BUG=v8:8547

Change-Id: Ic459357a10311346499ea054447d6cc42352fc0d
Reviewed-on: https://chromium-review.googlesource.com/c/1363133Reviewed-by: Toon Verwaest <verwaest@chromium.org>
Commit-Queue: Marja Hölttä <marja@chromium.org>
Cr-Commit-Position: refs/heads/master@{#58090}

src/property-details.h

@@ -307,6 +307,11 @@ class PropertyDetails {
     return AttributesField::decode(value_);
   }
 
+  bool HasKindAndAttributes(PropertyKind kind, PropertyAttributes attributes) {
+    return (value_ & (KindField::kMask | AttributesField::kMask)) ==
+           (KindField::encode(kind) | AttributesField::encode(attributes));
+  }
+
   int dictionary_index() const {
     return DictionaryStorageField::decode(value_);
   }

src/transitions.cc

@@ -305,8 +305,8 @@ bool TransitionsAccessor::IsMatchingMap(Map target, Name name,
   DescriptorArray descriptors = target->instance_descriptors();
   Name key = descriptors->GetKey(descriptor);
   if (key != name) return false;
-  PropertyDetails details = descriptors->GetDetails(descriptor);
-  return (details.kind() == kind && details.attributes() == attributes);
+  return descriptors->GetDetails(descriptor)
+      .HasKindAndAttributes(kind, attributes);
 }
 
 // static