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 D9762C433F5 for ; Thu, 31 Mar 2022 09:57:10 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234391AbiCaJ64 (ORCPT ); Thu, 31 Mar 2022 05:58:56 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55996 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234376AbiCaJ6t (ORCPT ); Thu, 31 Mar 2022 05:58:49 -0400 Received: from verein.lst.de (verein.lst.de [213.95.11.211]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 36DA120216D for ; Thu, 31 Mar 2022 02:57:02 -0700 (PDT) Received: by verein.lst.de (Postfix, from userid 2407) id E0E8A68BEB; Thu, 31 Mar 2022 11:56:58 +0200 (CEST) Date: Thu, 31 Mar 2022 11:56:58 +0200 From: Christoph Hellwig To: Heiko Stuebner Cc: palmer@dabbelt.com, paul.walmsley@sifive.com, aou@eecs.berkeley.edu, linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org, wefu@redhat.com, liush@allwinnertech.com, guoren@kernel.org, atishp@atishpatra.org, anup@brainfault.org, drew@beagleboard.org, hch@lst.de, arnd@arndb.de, wens@csie.org, maxime@cerno.tech, gfavor@ventanamicro.com, andrea.mondelli@huawei.com, behrensj@mit.edu, xinhaoqu@huawei.com, mick@ics.forth.gr, allen.baum@esperantotech.com, jscheid@ventanamicro.com, rtrauben@gmail.com, samuel@sholland.org, cmuellner@linux.com, philipp.tomsich@vrull.eu Subject: Re: [PATCH v8 07/14] riscv: prevent compressed instructions in alternatives Message-ID: <20220331095658.GD23422@lst.de> References: <20220324000710.575331-1-heiko@sntech.de> <20220324000710.575331-8-heiko@sntech.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220324000710.575331-8-heiko@sntech.de> User-Agent: Mutt/1.5.17 (2007-11-01) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Mar 24, 2022 at 01:07:03AM +0100, Heiko Stuebner wrote: > Instructions are opportunistically compressed by the RISC-V assembler > when possible, but in alternatives-blocks both the old and new content > need to be the same size, so having the toolchain do somewhat random > optimizations will cause strange side-effects like > "attempt to move .org backwards" compile-time errors. > > Already a simple "and" used in alternatives assembly will cause these > mismatched code sizes. > > So prevent compressed instructions to be generated in alternatives- > code and use option-push and -pop to only limit this to the relevant > code blocks Yes, that makes sense: Reviewed-by: Christoph Hellwig