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=-16.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,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 899EAC49EA6 for ; Fri, 25 Jun 2021 01:02:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 71418613B9 for ; Fri, 25 Jun 2021 01:02:34 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232995AbhFYBEv (ORCPT ); Thu, 24 Jun 2021 21:04:51 -0400 Received: from mail-ej1-f48.google.com ([209.85.218.48]:43868 "EHLO mail-ej1-f48.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232972AbhFYBEu (ORCPT ); Thu, 24 Jun 2021 21:04:50 -0400 Received: by mail-ej1-f48.google.com with SMTP id nb6so12401122ejc.10; Thu, 24 Jun 2021 18:02:29 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=5d1bwUaSuG/f6mTu6ru/WOtu9a5hLw1cNtYO/dabh8E=; b=CjKz94yHeYEmEKt1OkiIOBRmUasTa4EZgS+7uMnN3enZT8Yr3zjXeglsLkCN8t/VNm zZrhiZIJuU6/eGbuNs7lfZlPglcIUW7E9IGJ851y/3w4MqDxx/BQrosR9QCCGtnBUUWM tzvuwKL2+cRtOFAJRoED1e4HZMfOouL4bj8XthPRM74h7p65t8iKmWTMBFk00ztwPN4n bQbniRQf9uTy+bFmTyCj1TOQJZb4iljHmRMk2jED8WdWCqky1khQQW37DHUPCbdUW+VR ++yCDWI3WGddTs5CoVe+KTNYj11svMKeLWLsEaSafP8V9dSb6C/vzTmEgD+NDkaC6SZX 5Slw== X-Gm-Message-State: AOAM530lKX6AggpuUsjFYCNaDm2eSnX+6+TfWLHIs3as2OnL4jZFX613 8FeF4GNRCoyIttaQPgprHCSnW4qvu7jYtw== X-Google-Smtp-Source: ABdhPJxINwo0+vWL6bmf2rOXNOQTpbhqaRuhL6BUfM1PoIYKKfYvwU+5wDopzTUQ2tk9MFuhlrmHSA== X-Received: by 2002:a17:906:30d0:: with SMTP id b16mr8028751ejb.495.1624582949235; Thu, 24 Jun 2021 18:02:29 -0700 (PDT) Received: from msft-t490s.home (host-95-251-17-240.retail.telecomitalia.it. [95.251.17.240]) by smtp.gmail.com with ESMTPSA id yc29sm1921909ejb.106.2021.06.24.18.02.27 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 24 Jun 2021 18:02:28 -0700 (PDT) From: Matteo Croce To: linux-kernel@vger.kernel.org, Nick Kossifidis , Guo Ren , Christoph Hellwig , David Laight , Palmer Dabbelt , Emil Renner Berthing , Drew Fustini Cc: linux-arch@vger.kernel.org, Andrew Morton , Nick Desaulniers , linux-riscv@lists.infradead.org Subject: [PATCH 2/3] lib/string: optimized memmove Date: Fri, 25 Jun 2021 03:01:59 +0200 Message-Id: <20210625010200.362755-3-mcroce@linux.microsoft.com> X-Mailer: git-send-email 2.31.1 In-Reply-To: <20210625010200.362755-1-mcroce@linux.microsoft.com> References: <20210625010200.362755-1-mcroce@linux.microsoft.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-arch@vger.kernel.org From: Matteo Croce When the destination buffer is before the source one, or when the buffers doesn't overlap, it's safe to use memcpy() instead, which is optimized to use a bigger data size possible. This "optimization" only covers a common case. In future, proper code which does the same thing as memcpy() does but backwards can be done. Signed-off-by: Matteo Croce --- lib/string.c | 18 ++++++------------ 1 file changed, 6 insertions(+), 12 deletions(-) diff --git a/lib/string.c b/lib/string.c index 15e906f97d9e..69adec252597 100644 --- a/lib/string.c +++ b/lib/string.c @@ -976,19 +976,13 @@ EXPORT_SYMBOL(memcpy); */ void *memmove(void *dest, const void *src, size_t count) { - char *tmp; - const char *s; + if (dest < src || src + count <= dest) + return memcpy(dest, src, count); + + if (dest > src) { + const char *s = src + count; + char *tmp = dest + count; - if (dest <= src) { - tmp = dest; - s = src; - while (count--) - *tmp++ = *s++; - } else { - tmp = dest; - tmp += count; - s = src; - s += count; while (count--) *--tmp = *--s; } -- 2.31.1