From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
        id S1753939AbdJaKR6 (ORCPT <rfc822;w@1wt.eu>);
        Tue, 31 Oct 2017 06:17:58 -0400
Received: from frisell.zx2c4.com ([192.95.5.64]:51457 "EHLO frisell.zx2c4.com"
        rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP
        id S1753795AbdJaKRy (ORCPT <rfc822;linux-kernel@vger.kernel.org>);
        Tue, 31 Oct 2017 06:17:54 -0400
X-Google-Smtp-Source: ABhQp+SH7b8cywLkk/aY6TcfmxI/c6aUqyTXqT7lB7BbtLR6XyPJx1EepZThCrmWIUnO1V41wfI4pWDs99iisPSwnAo=
MIME-Version: 1.0
From: "Jason A. Donenfeld" <Jason@zx2c4.com>
Date: Tue, 31 Oct 2017 11:17:52 +0100
X-Gmail-Original-Message-ID: <CAHmME9q3=k2fJMi4Zy6d=ewj-P=sRhB8c_MjSJAMbKkopThi1w@mail.gmail.com>
Message-ID: <CAHmME9q3=k2fJMi4Zy6d=ewj-P=sRhB8c_MjSJAMbKkopThi1w@mail.gmail.com>
Subject: CONFIG_ARCH_SUPPORTS_INT128 for AArch64
To: linux-arm-kernel@lists.infradead.org,
        LKML <linux-kernel@vger.kernel.org>
Content-Type: text/plain; charset="UTF-8"
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

Hi folks,

Older versions of gcc are horrible for int128_t on aarch64, emitting a
__multi3 call, which is slow and defeats the purpose. However, more
recent versions of gcc (since 5, IIRC), do the right thing and produce
the proper inlined instructions.

Do we have the infrastructure available to test for this, and
conditionally set CONFIG_ARCH_SUPPORTS_INT128 if we do?

Thanks,
Jason