// remove.
    // TODO(jpienaar): Remove once recusive side-effects are supported.
    if (op.use_empty() &&
        (op.getIsStateless() ||
         (IsSideEffectFree(then_func) && IsSideEffectFree(else_func)))) {
      rewriter.eraseOp(op.getOperation());
      return success();
    }

    // Extract the constant cond value.
    DenseElementsAttr cond;