From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 29664 invoked by alias); 30 Aug 2013 18:46:31 -0000 Mailing-List: contact libc-ports-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Subscribe: List-Post: List-Help: , Sender: libc-ports-owner@sourceware.org Received: (qmail 29652 invoked by uid 89); 30 Aug 2013 18:46:31 -0000 Received: from mail-pa0-f53.google.com (HELO mail-pa0-f53.google.com) (209.85.220.53) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with (AES128-SHA encrypted) ESMTPS; Fri, 30 Aug 2013 18:46:31 +0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-3.2 required=5.0 tests=AWL,BAYES_00,KHOP_THREADED,NO_RELAYS autolearn=ham version=3.3.2 X-HELO: mail-pa0-f53.google.com Received: by mail-pa0-f53.google.com with SMTP id lb1so2664952pab.40 for ; Fri, 30 Aug 2013 11:46:28 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:mime-version:in-reply-to:references:date :message-id:subject:from:to:cc:content-type; bh=U+qz64OKlcu2frBOgW/rk/7GhwwpbDsPozjDweWCrIw=; b=Hp/h6REyxvxZclIMrQvdLLMVjONWToEkrDa9dcBS07FrmE3PeVhv1Pj46P3gy8ZOMx wdLFOIbnvtWjO28QWZN/Q9zeY2XYIJlNTVF6GLk/4Mt/9tRdoVoBRgFW7whti9REkpbQ JvjpTMyAAouzz5V+4JAltVBew4yaRax9iMlcwPHLFBDgCO649efYo1sZAUCPu23i4Af6 0/IvoqtiyCPy6b3NKynnCrFvk8bmPsUdj0hhPeWMNVPjBeLgv7OmVX/zZ524z6H3dzSh CjQY3zuDkxwUfFmluzZHGQ11OzRPj61EvTqh09dtd+2Nh+zaYZordfGh471mozm2Z318 4vEA== X-Gm-Message-State: ALoCoQn+MD7dxHq4lxvwvdW+49yeLEUm3roALllmEsxhZ2091Ha71oTt6UxZsszOY03fbvj3lL6b MIME-Version: 1.0 X-Received: by 10.68.143.131 with SMTP id se3mr11558834pbb.39.1377888388788; Fri, 30 Aug 2013 11:46:28 -0700 (PDT) Received: by 10.70.53.198 with HTTP; Fri, 30 Aug 2013 11:46:28 -0700 (PDT) In-Reply-To: References: <520894D5.7060207@linaro.org> Date: Fri, 30 Aug 2013 18:46:00 -0000 Message-ID: Subject: Re: [PATCH] sysdeps/arm/armv7/multiarch/memcpy_impl.S: Improve performance. From: Will Newton To: "Joseph S. Myers" Cc: "libc-ports@sourceware.org" , Patch Tracking Content-Type: text/plain; charset=ISO-8859-1 X-IsSubscribed: yes X-SW-Source: 2013-08/txt/msg00095.txt.bz2 On 30 August 2013 16:18, Joseph S. Myers wrote: > On Fri, 30 Aug 2013, Will Newton wrote: > >> > There are various comments regarding alignment, whether stating "LDRD/STRD >> > support unaligned word accesses" or referring to the mutual alignment that >> > applies for particular code. Does this patch make any of them out of >> > date? (If code can now only be reached with common 64-bit alignment, but >> > in fact requires only 32-bit alignment, the comment should probably state >> > both those things explicitly.) >> >> I've reviewed the comments and they all look ok as far as I can tell. > > Are you sure? For example, where it says "SRC and DST have the same > mutual 32-bit alignment", is it not in fact the case after the patch that > they now have the same mutual 64-bit alignment, even if this code doesn't > currently rely on that? I think the comments in each place should be > explicit about both things - what preconditions the code relies on, and > what possibly stronger preconditions are in fact true given the other code > in this file. Saying the mutual alignment is 32-bit when the reader can > see from the code not far above that it's 64-bit just seems liable to > confuse the reader, even if the comment is still formally true. > Similarly for the requirements on unaligned word accesses - after this > patch, which uses of ldrd/strd do require that? Yes, you're right, that needs more thought. I'll have a look at it next week. -- Will Newton Toolchain Working Group, Linaro