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 3C0E2C77B7C for ; Wed, 10 May 2023 03:53:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235818AbjEJDxa (ORCPT ); Tue, 9 May 2023 23:53:30 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53062 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235708AbjEJDxV (ORCPT ); Tue, 9 May 2023 23:53:21 -0400 Received: from m12.mail.163.com (m12.mail.163.com [220.181.12.197]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id AB80C40FD for ; Tue, 9 May 2023 20:53:19 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=163.com; s=s110527; h=From:Subject:Date:Message-Id:MIME-Version; bh=p9uHm CC4GlxQ1KU1bCyXbYnX5kCC6wGpCXGXt/a9UPs=; b=aLE2OGyMktksauQZV60GQ 2juJOIJXrU0JD9B222ZqcM6sR9AJIsiwXQdhRxvNNfmViY9XXBkX0uN4/pRMaMCW sYEc17UWX9zcfKiEN+TUnoE9LbYZ5tkM0VtuMayg8y4slJ9Zfi0+2sT7HQ+l6XR2 kLBJQo/m4iAIYAeutBnIkk= Received: from zhangf-virtual-machine.localdomain (unknown [180.111.102.183]) by zwqz-smtp-mta-g3-4 (Coremail) with SMTP id _____wBHlVQOFVtk+zPWBQ--.60792S5; Wed, 10 May 2023 11:52:59 +0800 (CST) From: zhangfei To: ajones@ventanamicro.com Cc: aou@eecs.berkeley.edu, linux-kernel@vger.kernel.org, linux-riscv@lists.infradead.org, palmer@dabbelt.com, paul.walmsley@sifive.com, zhang_fei_0403@163.com, zhangfei@nj.iscas.ac.cn Subject: Re: [PATCH] riscv: Optimize memset Date: Wed, 10 May 2023 11:52:43 +0800 Message-Id: <20230510035243.8586-4-zhang_fei_0403@163.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20230510035243.8586-1-zhang_fei_0403@163.com> References: <20230509-b0dc346928ddc8d2b5690f67@orel> <20230510035243.8586-1-zhang_fei_0403@163.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-CM-TRANSID: _____wBHlVQOFVtk+zPWBQ--.60792S5 X-Coremail-Antispam: 1Uf129KBjvdXoW7Jr4fCw18Ww4rtF4DtFW7twb_yoWfCwb_G3 yUJrnYkwn8ArZakFs3Kr45WrWqy34DArW5Wr18Xw12gr9YqrWDZ3yvkr9Yva48G3WI9Fnx CFyYqayUAr1S9jkaLaAFLSUrUUUUUb8apTn2vfkv8UJUUUU8Yxn0WfASr-VFAUDa7-sFnT 9fnUUvcSsGvfC2KfnxnUUI43ZEXa7xRiBHqJUUUUU== X-Originating-IP: [180.111.102.183] X-CM-SenderInfo: x2kd0w5bihxsiquqjqqrwthudrp/xtbCfBBrl2DcJd-5swAAsc Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: zhangfei On Tue, May 09, 2023 11:16:33AM +0200, Andrew Jones wrote: > On Tue, May 09, 2023 at 10:22:07AM +0800, zhangfei wrote: > > > > Hi, > > > > I filled head and tail with minimal branching. Each conditional ensures that > > all the subsequently used offsets are well-defined and in the dest region. > > I know. You trimmed my comment, so I'll quote myself, here > > """ > After the check of a2 against 6 above we know that offsets 6(t0) > and -7(a3) are safe. Are we trying to avoid too may redundant > stores with these additional checks? > """ > > So, again. Why the additional check against 8 above and, the one you > trimmed, checking 10? Hi, These additional checks are to avoid too many redundant stores. Adding a check for more than 8 bytes is because after the loop segment '3' comes out, the remaining bytes are less than 8 bytes, which also avoids redundant stores. Thanks, Fei Zhang