message: formula preproc: throttle down undef/poison type replacement if expr gets too big
diff: @@ -165,6 +165,10 @@ static expr preprocess(Transform &t, const set<expr> &qvars,
  }
  }
  instances = move(instances2);
  +
  + // Bail out if it gets too big. It's very likely we can't solve it anyway.
  + if (instances.size() >= 128 || hit_half_memory_limit())
  + break;
  }
  expr insts(false);
  