message: we don't have to set the frame on every step
diff: @@ -36,9 +36,6 @@ impl<'a, 'tcx> EvalContext<'a, 'tcx> {
  return Ok(false);
  }
  - let cur_frame = self.cur_frame();
  - self.memory.set_cur_frame(cur_frame);
  -
  let block = self.frame().block;
  let stmt_id = self.frame().stmt;
  let mir = self.mir();
  