[topl][bugfix] Construct the automaton only once
[topl][bugfix] Construct the automaton only once

Summary: Don't recompute automaton.

Differential Revision: D34580766

fbshipit-source-id: 02a78681beee877575ed5404a54d97a6b1bc98cc

facebook/infer,facebook/infer,facebook/infer,facebook/infer,facebook/infer,facebook/infer,facebook/infer