return x, exact
		}
	}
	for t = t.Parent(); t != root; t = t.Parent() {
		// No variants specified: just compare core components.
		// The key has the form lllssrrr, where l, s, and r are nibbles for
		// respectively the langID, scriptID, and regionID.
		if x, ok := getCoreIndex(t); ok {
			return x, exact
		}
	}
	return 0, exact
}