[turbofan] Introduce map-guarded generic handler for named store.

src/compiler/access-info.cc

Index: src/compiler/access-info.cc
diff --git a/src/compiler/access-info.cc b/src/compiler/access-info.cc
index 3c3dbcbefaa84dba398739d82982a56083969eec..866b06086a2042df0f6a811e25c7fa8a1f36ce62 100644
--- a/src/compiler/access-info.cc
+++ b/src/compiler/access-info.cc
@@ -94,6 +94,12 @@ PropertyAccessInfo PropertyAccessInfo::AccessorConstant(
   return PropertyAccessInfo(kAccessorConstant, holder, constant, receiver_maps);
 }
 
+// static
+PropertyAccessInfo PropertyAccessInfo::Generic(MapList const& receiver_maps) {
+  return PropertyAccessInfo(kGeneric, MaybeHandle<JSObject>(), Handle<Object>(),
+                            receiver_maps);
+}
+
 PropertyAccessInfo::PropertyAccessInfo()
     : kind_(kInvalid),
       field_representation_(MachineRepresentation::kNone),
@@ -167,6 +173,12 @@ bool PropertyAccessInfo::Merge(PropertyAccessInfo const* that) {
       }
       return false;
     }
+    case kGeneric: {
+      this->receiver_maps_.insert(this->receiver_maps_.end(),
+                                  that->receiver_maps_.begin(),
+                                  that->receiver_maps_.end());
+      return true;
+    }
   }
 
   UNREACHABLE();
@@ -478,7 +490,10 @@ bool AccessInfoFactory::LookupTransition(Handle<Map> map, Handle<Name> name,
                                          MaybeHandle<JSObject> holder,
                                          PropertyAccessInfo* access_info) {
   // Check if the {map} has a data transition with the given {name}.
-  if (map->unused_property_fields() == 0) return false;
+  if (map->unused_property_fields() == 0) {
+    *access_info = PropertyAccessInfo::Generic(MapList{map});
+    return true;
+  }
   Handle<Map> transition_map;
   if (TransitionArray::SearchTransition(map, kData, name, NONE)
           .ToHandle(&transition_map)) {