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 lists.ozlabs.org (lists.ozlabs.org [112.213.38.117]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 0372EC433F5 for ; Thu, 6 Oct 2022 19:56:49 +0000 (UTC) Received: from boromir.ozlabs.org (localhost [IPv6:::1]) by lists.ozlabs.org (Postfix) with ESMTP id 4Mk2Jc0D9dz3dwV for ; Fri, 7 Oct 2022 06:56:48 +1100 (AEDT) Authentication-Results: lists.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=kernel.crashing.org (client-ip=63.228.1.57; helo=gate.crashing.org; envelope-from=segher@kernel.crashing.org; receiver=) Received: from gate.crashing.org (gate.crashing.org [63.228.1.57]) by lists.ozlabs.org (Postfix) with ESMTP id 4Mk2Hz4Lcgz3c6g for ; Fri, 7 Oct 2022 06:56:14 +1100 (AEDT) Received: from gate.crashing.org (localhost.localdomain [127.0.0.1]) by gate.crashing.org (8.14.1/8.14.1) with ESMTP id 296JsCWC017787; Thu, 6 Oct 2022 14:54:12 -0500 Received: (from segher@localhost) by gate.crashing.org (8.14.1/8.14.1/Submit) id 296JsBux017786; Thu, 6 Oct 2022 14:54:11 -0500 X-Authentication-Warning: gate.crashing.org: segher set sender to segher@kernel.crashing.org using -f Date: Thu, 6 Oct 2022 14:54:11 -0500 From: Segher Boessenkool To: Nicholas Piggin Subject: Re: [PATCH] powerpc/64s: POWER10 CPU Kconfig build option Message-ID: <20221006195411.GS25951@gate.crashing.org> References: <20220923033004.536127-1-npiggin@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220923033004.536127-1-npiggin@gmail.com> User-Agent: Mutt/1.4.2.3i X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linuxppc-dev@lists.ozlabs.org Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" Hi! On Fri, Sep 23, 2022 at 01:30:04PM +1000, Nicholas Piggin wrote: > This adds basic POWER10_CPU option, which builds with -mcpu=power10. > +# No prefix or pcrel > +KBUILD_CFLAGS += $(call cc-option,-mno-prefixed) > +KBUILD_CFLAGS += $(call cc-option,-mno-pcrel) Why do you disable all prefixed insns? What goes wrong if you don't? Same question for pcrel. I'm sure you want to optimise it better, but it's not clear to me how it fails now? Please say in the comment what is wrong, don't spread fear :-) > +# No AltiVec or VSX or MMA instructions when building kernel > KBUILD_CFLAGS += $(call cc-option,-mno-altivec) > KBUILD_CFLAGS += $(call cc-option,-mno-vsx) > +KBUILD_CFLAGS += $(call cc-option,-mno-mma) MMA code is never generated unless the code asks for it explicitly. This is fundamental, not just an implementations side effect. Segher