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=-5.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, 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 25D7CC433ED for ; Mon, 12 Apr 2021 22:00:17 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id EE76E6135C for ; Mon, 12 Apr 2021 22:00:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1343568AbhDLWAa (ORCPT ); Mon, 12 Apr 2021 18:00:30 -0400 Received: from gate.crashing.org ([63.228.1.57]:54271 "EHLO gate.crashing.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238235AbhDLWA1 (ORCPT ); Mon, 12 Apr 2021 18:00:27 -0400 Received: from gate.crashing.org (localhost.localdomain [127.0.0.1]) by gate.crashing.org (8.14.1/8.14.1) with ESMTP id 13CLsVAn011590; Mon, 12 Apr 2021 16:54:31 -0500 Received: (from segher@localhost) by gate.crashing.org (8.14.1/8.14.1/Submit) id 13CLsTMj011588; Mon, 12 Apr 2021 16:54:29 -0500 X-Authentication-Warning: gate.crashing.org: segher set sender to segher@kernel.crashing.org using -f Date: Mon, 12 Apr 2021 16:54:28 -0500 From: Segher Boessenkool To: Christophe Leroy Cc: Benjamin Herrenschmidt , Paul Mackerras , Michael Ellerman , linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v1 1/2] powerpc/bitops: Use immediate operand when possible Message-ID: <20210412215428.GM26583@gate.crashing.org> References: <09da6fec57792d6559d1ea64e00be9870b02dab4.1617896018.git.christophe.leroy@csgroup.eu> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <09da6fec57792d6559d1ea64e00be9870b02dab4.1617896018.git.christophe.leroy@csgroup.eu> User-Agent: Mutt/1.4.2.3i Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi! On Thu, Apr 08, 2021 at 03:33:44PM +0000, Christophe Leroy wrote: > For clear bits, on 32 bits 'rlwinm' can be used instead or 'andc' for > when all bits to be cleared are consecutive. Also on 64-bits, as long as both the top and bottom bits are in the low 32-bit half (for 32 bit mode, it can wrap as well). > For the time being only > handle the single bit case, which we detect by checking whether the > mask is a power of two. You could look at rs6000_is_valid_mask in GCC: used by rs6000_is_valid_and_mask immediately after it. You probably want to allow only rlwinm in your case, and please note this checks if something is a valid mask, not the inverse of a valid mask (as you want here). So yes this is pretty involved :-) Your patch looks good btw. But please use "n", not "i", as constraint? Segher