From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id B6245C433EF for ; Mon, 11 Jul 2022 17:15:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231286AbiGKRPl (ORCPT ); Mon, 11 Jul 2022 13:15:41 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52870 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229477AbiGKRPk (ORCPT ); Mon, 11 Jul 2022 13:15:40 -0400 Received: from gate.crashing.org (gate.crashing.org [63.228.1.57]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id E58935140F for ; Mon, 11 Jul 2022 10:15:38 -0700 (PDT) Received: from gate.crashing.org (localhost.localdomain [127.0.0.1]) by gate.crashing.org (8.14.1/8.14.1) with ESMTP id 26BHCQwP008080; Mon, 11 Jul 2022 12:12:27 -0500 Received: (from segher@localhost) by gate.crashing.org (8.14.1/8.14.1/Submit) id 26BHCQ80008079; Mon, 11 Jul 2022 12:12:26 -0500 X-Authentication-Warning: gate.crashing.org: segher set sender to segher@kernel.crashing.org using -f Date: Mon, 11 Jul 2022 12:12:26 -0500 From: Segher Boessenkool To: Arnd Bergmann Cc: Christophe Leroy , linuxppc-dev , Linux Kernel Mailing List , Nicholas Piggin Subject: Re: [PATCH v1 4/5] powerpc/44x: Fix build failure with GCC 12 (unrecognized opcode: `wrteei') Message-ID: <20220711171226.GG25951@gate.crashing.org> References: <8abab4888da69ff78b73a56f64d9678a7bf684e9.1657549153.git.christophe.leroy@csgroup.eu> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.4.2.3i Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jul 11, 2022 at 05:05:04PM +0200, Arnd Bergmann wrote: > Is there any value in building for -mcpu=440 or -mcpu=464 when targeting a 476? The original 440 had a very short pipeline. Later IBM 4xx have a longer pipeline. Getting this right (with -mtune=, or just with -mcpu=) is important for performance. So, no? > Maybe add another !PPC_47x dependency for the first two. Ideally we would also > enforce that 440/464 based boards cannot be selected together with 476, though > I guess that is a separate issue. > > Is there a practical difference between 440 and 464 when building kernels? > gcc seems to treat them the same way, so maybe one option for both is enough > here. -mcpu= is used as the default for -mtune=, so that is always a consideration. PPC464 is treated the same as PPC440 in binutils as well, so I don't think there is any issue there. Segher