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 52AF8C6FA82 for ; Wed, 21 Sep 2022 15:25:15 +0000 (UTC) Received: from boromir.ozlabs.org (localhost [IPv6:::1]) by lists.ozlabs.org (Postfix) with ESMTP id 4MXj093nx9z3cd8 for ; Thu, 22 Sep 2022 01:25:13 +1000 (AEST) 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 4MXhzk1h65z300l for ; Thu, 22 Sep 2022 01:24:49 +1000 (AEST) Received: from gate.crashing.org (localhost.localdomain [127.0.0.1]) by gate.crashing.org (8.14.1/8.14.1) with ESMTP id 28LFMjJI016405; Wed, 21 Sep 2022 10:22:45 -0500 Received: (from segher@localhost) by gate.crashing.org (8.14.1/8.14.1/Submit) id 28LFMjeK016402; Wed, 21 Sep 2022 10:22:45 -0500 X-Authentication-Warning: gate.crashing.org: segher set sender to segher@kernel.crashing.org using -f Date: Wed, 21 Sep 2022 10:22:45 -0500 From: Segher Boessenkool To: Nicholas Piggin Subject: Re: [RFC PATCH 5/7] powerpc/64s: update generic cpu option name and compiler flags Message-ID: <20220921152245.GD25951@gate.crashing.org> References: <20220919140149.4018927-1-npiggin@gmail.com> <20220919140149.4018927-6-npiggin@gmail.com> <20220920221608.GB25951@gate.crashing.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: 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, Alan Modra Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" Hi! On Wed, Sep 21, 2022 at 11:01:18AM +1000, Nicholas Piggin wrote: > On Wed Sep 21, 2022 at 8:16 AM AEST, Segher Boessenkool wrote: > > On Tue, Sep 20, 2022 at 12:01:47AM +1000, Nicholas Piggin wrote: > > > Update the 64s GENERIC_CPU option. POWER4 support has been dropped, so > > > make that clear in the option name. > > > > AFAIR the minimum now is POWER4+ (ISA 2.01), not POWER5 (ISA 2.02). > > It's POWER5 now, because of commit 471d7ff8b5 ("powerpc/64s: Remove > POWER4 support"), which is misguided about POWER4+ and also introduced > the -mcpu=power5 bug on 970 builds :\ ISA 2.01 added just a few things (LPES[0], HDEC, some PM things, but crucially also anything that sets MSR[PR] also sets MSR[EE] since then). > Not sure it's worth adding POWER4+ support back but if someone has a > POWER4+ or adds it to QEMU TCG, I will do the patch. 970 is 2.01 -- pretending it is 2.02 is a ticking time bomb: the popcntb insn will be generated for popcount and parity intrinsics, which can be generated by generic code! > > > -mtune= before power8 is dropped because the minimum gcc version > > > supports power8, and tuning is made consistent between big and little > > > endian. > > > > Tuning for p8 on e.g. 970 gives quite bad results. No idea if anyone > > cares, but this is a serious regression if so. > > It's for "generic" kernel so we set low minimum but higher tune, > assuming that people would usually have newer, so it was already > doing -mtune=power7. > > We could make a specific 970/G5 entry though, since those still > have users. If that uses -mcpu=power4 (which means ISA 2.01 btw!) all is fine already? (Or -mcpu=970, same thing really, it just allows VMX as well). Thanks for taking care of this Nick, much appreciated! Segher