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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (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 E47E0C433F5 for ; Fri, 10 Dec 2021 22:52:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:Cc:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=l6/epAIyBsPXzf1DEoL7sTD15HkOV+bZCn5Ukm/VKHI=; b=eZP9lnq3SNGTpv U2eTaC/1IWs3ndWPNAuRfco/SXoEauU9kglRwrzFvYVRMojyDBYxED0qL7YoQ/IuAIU1g2UUoJ4a0 Ie/A7o5AXPIiwEa8n6T5hBw4udJ2GvnU8+P6M2EghLg7cQxcW0ZYblydYMLgIlzYRiHaxfMj2tH02 sVEyXLypHv2P8IYrdE5ID2oQ3GXuoHXzD6Q2l6NCYSV7KWGI86rkPiQphsGVe6MrIDUwvXXoh+wHx qSR1/6NMzMS1B1HMMRZEezo9OlT0DOFbJAnPmC/H2ZuttAgzdmBQLT1RsGQEr6zpVSVQUzTjgVu0o +o9CiRyiL+DiH/YKwSQg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1mvoir-004Bbs-72; Fri, 10 Dec 2021 22:50:38 +0000 Received: from casper.infradead.org ([2001:8b0:10b:1236::1]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1mvoEy-003zie-DE for linux-arm-kernel@bombadil.infradead.org; Fri, 10 Dec 2021 22:19:44 +0000 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=IJIguE1bOvunyelHz1yFliV47TEJhhY1USy6nt7R63k=; b=n9GIL597THRkcOM9roid8jWGga paH3zfyExrNG9TiG1P/gsjSFF297oS/IYUM40yzP0+os04bOKBVnqfLXWLEsWB1x7vH/HencinD+N obVRRnlZVdF5nonfeYxqcDvzD8UOEoAnkC2I9y00K4Jp/z1NjbFqSzk16DI0ZEEyGmUFWqoahdUoT FvSyL+Fn5tcoYdJTyPvodt8dS+oeG+tUOKFMZD8t/8SVuZjPoubnjhDZoLjW99U+ERE2hSjsLleL2 /nejrjoSTG8NVUPPM8IUyF5qWIsOsLqn8gYoyIfdBpsGN6BllHep27y/Ao7lpLct1PltFBlgTH4HI ZOAsazSw==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=worktop.programming.kicks-ass.net) by casper.infradead.org with esmtpsa (Exim 4.94.2 #2 (Red Hat Linux)) id 1mvoEv-00Ak2T-5q; Fri, 10 Dec 2021 22:19:42 +0000 Received: by worktop.programming.kicks-ass.net (Postfix, from userid 1000) id 17088984E0B; Fri, 10 Dec 2021 23:19:41 +0100 (CET) Date: Fri, 10 Dec 2021 23:19:40 +0100 From: Peter Zijlstra To: Mark Rutland Cc: linux-arm-kernel@lists.infradead.org, boqun.feng@gmail.com, catalin.marinas@arm.com, will@kernel.org Subject: Re: [PATCH 5/5] arm64: atomics: lse: define RETURN ops in terms of FETCH ops Message-ID: <20211210221940.GU16608@worktop.programming.kicks-ass.net> References: <20211210151410.2782645-1-mark.rutland@arm.com> <20211210151410.2782645-6-mark.rutland@arm.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20211210151410.2782645-6-mark.rutland@arm.com> X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Fri, Dec 10, 2021 at 03:14:10PM +0000, Mark Rutland wrote: > The FEAT_LSE atomic instructions include LD* instructions which return > the original value of a memory location can be used to directly > implement FETCH opertations. Each RETURN op is implemented as a copy of > the corresponding FETCH op with a trailing instruction instruction to instruction instruction instruction is probably even more better :-) > generate the new value of the memory location. We only > directly implement *_fetch_add*(), for which we have a trailing `add` > instruction. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel