From patchwork Fri Mar 5 12:22:21 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg Kroah-Hartman X-Patchwork-Id: 394301 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=-18.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER, INCLUDES_PATCH, MAILING_LIST_MULTI, SPF_HELO_NONE, SPF_PASS, URIBL_BLOCKED, USER_AGENT_GIT autolearn=ham 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 6D79EC433DB for ; Fri, 5 Mar 2021 12:42:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4550665021 for ; Fri, 5 Mar 2021 12:42:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231828AbhCEMlx (ORCPT ); Fri, 5 Mar 2021 07:41:53 -0500 Received: from mail.kernel.org ([198.145.29.99]:57268 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229768AbhCEMlW (ORCPT ); Fri, 5 Mar 2021 07:41:22 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id 779D36502E; Fri, 5 Mar 2021 12:41:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1614948082; bh=UWLIWfYD+prOzt22pde3LwfE441zn2YNFpURl7hefXw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=x50rXlHjLozYN8VuJGc4Q/0EnpmGdBM914ZSUVFs3Xg5+9V0RJodjKk2i6VGVDiJE LOZk+1b0L7hosfMdS40TyAYtxKZinXOQnKdRS3AIb8IUi8t4RQF1QVUNjYg0eMNvvq BsEyv96RKUPoDQoSgiUeO4nUhVr/UX+xw5fqngaQ= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Will Deacon , Robin Murphy , Catalin Marinas , Ben Hutchings Subject: [PATCH 4.9 14/41] arm64: Remove redundant mov from LL/SC cmpxchg Date: Fri, 5 Mar 2021 13:22:21 +0100 Message-Id: <20210305120851.988419372@linuxfoundation.org> X-Mailer: git-send-email 2.30.1 In-Reply-To: <20210305120851.255002428@linuxfoundation.org> References: <20210305120851.255002428@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Robin Murphy commit 8df728e1ae614f592961e51f65d3e3212ede5a75 upstream. The cmpxchg implementation introduced by commit c342f78217e8 ("arm64: cmpxchg: patch in lse instructions when supported by the CPU") performs an apparently redundant register move of [old] to [oldval] in the success case - it always uses the same register width as [oldval] was originally loaded with, and is only executed when [old] and [oldval] are known to be equal anyway. The only effect it seemingly does have is to take up a surprising amount of space in the kernel text, as removing it reveals: text data bss dec hex filename 12426658 1348614 4499749 18275021 116dacd vmlinux.o.new 12429238 1348614 4499749 18277601 116e4e1 vmlinux.o.old Reviewed-by: Will Deacon Signed-off-by: Robin Murphy Signed-off-by: Catalin Marinas Signed-off-by: Ben Hutchings Signed-off-by: Greg Kroah-Hartman --- arch/arm64/include/asm/atomic_ll_sc.h | 1 - 1 file changed, 1 deletion(-) --- a/arch/arm64/include/asm/atomic_ll_sc.h +++ b/arch/arm64/include/asm/atomic_ll_sc.h @@ -264,7 +264,6 @@ __LL_SC_PREFIX(__cmpxchg_case_##name(vol " st" #rel "xr" #sz "\t%w[tmp], %" #w "[new], %[v]\n" \ " cbnz %w[tmp], 1b\n" \ " " #mb "\n" \ - " mov %" #w "[oldval], %" #w "[old]\n" \ "2:" \ : [tmp] "=&r" (tmp), [oldval] "=&r" (oldval), \ [v] "+Q" (*(unsigned long *)ptr) \