_fp_mul_redc1
ret = _fp_mul_redc1(&(out->fp_val), &(in->fp_val), &one, out->ctx);
ret = _fp_mul_redc1(&(out->fp_val), &(in1->fp_val), &(in2->fp_val),
ret = _fp_mul_redc1(&(out->fp_val), &(in->fp_val), &(out->ctx->r_square),