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 X-Spam-Level: X-Spam-Status: No, score=-4.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, TVD_SUBJ_WIPE_DEBT,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 49FB8C433E9 for ; Thu, 11 Feb 2021 12:45:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 24A6464E8A for ; Thu, 11 Feb 2021 12:45:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231312AbhBKMpL (ORCPT ); Thu, 11 Feb 2021 07:45:11 -0500 Received: from gate.crashing.org ([63.228.1.57]:58691 "EHLO gate.crashing.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229965AbhBKM31 (ORCPT ); Thu, 11 Feb 2021 07:29:27 -0500 Received: from gate.crashing.org (localhost.localdomain [127.0.0.1]) by gate.crashing.org (8.14.1/8.14.1) with ESMTP id 11BCMD5w030851; Thu, 11 Feb 2021 06:22:13 -0600 Received: (from segher@localhost) by gate.crashing.org (8.14.1/8.14.1/Submit) id 11BCMCwY030849; Thu, 11 Feb 2021 06:22:12 -0600 X-Authentication-Warning: gate.crashing.org: segher set sender to segher@kernel.crashing.org using -f Date: Thu, 11 Feb 2021 06:22:11 -0600 From: Segher Boessenkool To: Nicholas Piggin Cc: Benjamin Herrenschmidt , Christophe Leroy , Michael Ellerman , Paul Mackerras , linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] powerpc/bug: Remove specific powerpc BUG_ON() Message-ID: <20210211122211.GC28121@gate.crashing.org> References: <694c7195c81d1bcc781b3c14f452886683d6c524.1613029237.git.christophe.leroy@csgroup.eu> <1613036567.zvyupcz926.astroid@bobo.none> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1613036567.zvyupcz926.astroid@bobo.none> User-Agent: Mutt/1.4.2.3i Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Feb 11, 2021 at 08:04:55PM +1000, Nicholas Piggin wrote: > Excerpts from Christophe Leroy's message of February 11, 2021 5:41 pm: > > As modern powerpc implement branch folding, that's even more efficient. Ah, it seems you mean what Arm calls branch folding. Sure, power4 already did that, and this has not changed. > I think POWER will speculate conditional traps as non faulting always > so it should be just as good if not better than the branch. Right, these are not branch instructions, so are not branch predicted; all trap instructions are assumed to fall through, like all other non-branch instructions. Segher