From patchwork Sun Jun 10 23:16:09 2012 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Hans-Peter Nilsson X-Patchwork-Id: 164014 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Received: from sourceware.org (server1.sourceware.org [209.132.180.131]) by ozlabs.org (Postfix) with SMTP id 10443B6FEF for ; Mon, 11 Jun 2012 09:16:30 +1000 (EST) Comment: DKIM? See http://www.dkim.org DKIM-Signature: v=1; a=rsa-sha1; c=relaxed/relaxed; d=gcc.gnu.org; s=default; x=1339974991; h=Comment: DomainKey-Signature:Received:Received:Received:Received:Received: Received:Received:Received:Received:Date:Message-Id:From:To:CC: In-reply-to:Subject:MIME-Version:Content-Type: Content-Transfer-Encoding:Mailing-List:Precedence:List-Id: List-Unsubscribe:List-Archive:List-Post:List-Help:Sender: Delivered-To; bh=awmnjtiMA/8W8qsqYTtffL4x8Ms=; b=YZdjN0UNKO4kbQ8 dA4nYXuzCt1vH5Wec6hgU7rprBTUXor5qyG19m7xqOfFluKs00GOkvCl/nVdhre3 6jeasM+kAXfTSO5or1iToIHeRYFRj/glFw4SNsi77fL1qv23vH3kdjx7ARbtrjLI Hh3JFVyHXhYvw2lVcXy0hK5/ATJE= Comment: DomainKeys? See http://antispam.yahoo.com/domainkeys DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=default; d=gcc.gnu.org; h=Received:Received:X-SWARE-Spam-Status:X-Spam-Check-By:Received:Received:Received:Received:Received:Received:Received:Date:Message-Id:From:To:CC:In-reply-to:Subject:MIME-Version:Content-Type:Content-Transfer-Encoding:Mailing-List:Precedence:List-Id:List-Unsubscribe:List-Archive:List-Post:List-Help:Sender:Delivered-To; b=lyeRkMwgRaISSeJX84z1l/mQ2BF3ADG4wFU9DiQiV7B9kLV5sqeLIFA5Vvt2AC eaVwOPS/CV71vWjmWJc+ipXI+tprTbeea4HmgsgMhgqjvsxrSzCwOspx325wcrOQ 7OpCIugmic2ejyV7qXqxqhxOHSPti7BfS32FkDg+J+i2M=; Received: (qmail 5714 invoked by alias); 10 Jun 2012 23:16:26 -0000 Received: (qmail 5705 invoked by uid 22791); 10 Jun 2012 23:16:25 -0000 X-SWARE-Spam-Status: No, hits=-2.9 required=5.0 tests=AWL, BAYES_00, KHOP_THREADED, RCVD_IN_HOSTKARMA_NO, T_RP_MATCHES_RCVD X-Spam-Check-By: sourceware.org Received: from anubis.se.axis.com (HELO anubis.se.axis.com) (195.60.68.12) by sourceware.org (qpsmtpd/0.43rc1) with ESMTP; Sun, 10 Jun 2012 23:16:13 +0000 Received: from localhost (localhost [127.0.0.1]) by anubis.se.axis.com (Postfix) with ESMTP id 3E56D19E48; Mon, 11 Jun 2012 01:16:12 +0200 (CEST) Received: from anubis.se.axis.com ([127.0.0.1]) by localhost (anubis.se.axis.com [127.0.0.1]) (amavisd-new, port 10024) with LMTP id HS6Pq4hIv0eD; Mon, 11 Jun 2012 01:16:10 +0200 (CEST) Received: from thoth.se.axis.com (thoth.se.axis.com [10.0.2.173]) by anubis.se.axis.com (Postfix) with ESMTP id 79B7D19E45; Mon, 11 Jun 2012 01:16:10 +0200 (CEST) Received: from ignucius.se.axis.com (ignucius.se.axis.com [10.88.21.50]) by thoth.se.axis.com (Postfix) with ESMTP id 75339340CA; Mon, 11 Jun 2012 01:16:10 +0200 (CEST) Received: from ignucius.se.axis.com (localhost [127.0.0.1]) by ignucius.se.axis.com (8.12.8p1/8.12.8/Debian-2woody1) with ESMTP id q5ANGAmt024443; Mon, 11 Jun 2012 01:16:10 +0200 Received: (from hp@localhost) by ignucius.se.axis.com (8.12.8p1/8.12.8/Debian-2woody1) id q5ANG9eF024439; Mon, 11 Jun 2012 01:16:09 +0200 Date: Mon, 11 Jun 2012 01:16:09 +0200 Message-Id: <201206102316.q5ANG9eF024439@ignucius.se.axis.com> From: Hans-Peter Nilsson To: gerald@pfeifer.com CC: gcc-patches@gcc.gnu.org, richard.earnshaw@arm.com In-reply-to: (message from Gerald Pfeifer on Mon, 11 Jun 2012 00:27:21 +0200) Subject: Re: [RFA:] Caveat for ARM in gcc-4.7/changes.html: unaligned accesses MIME-Version: 1.0 Mailing-List: contact gcc-patches-help@gcc.gnu.org; run by ezmlm Precedence: bulk List-Id: List-Unsubscribe: List-Archive: List-Post: List-Help: Sender: gcc-patches-owner@gcc.gnu.org Delivered-To: mailing list gcc-patches@gcc.gnu.org > From: Gerald Pfeifer > Date: Mon, 11 Jun 2012 00:27:21 +0200 > This is only a review wearing my web hat; it is orthogonal to the > discussion with the ARM guys. ;-) > > On Fri, 8 Jun 2012, Hans-Peter Nilsson wrote: > > +
  • On ARM, when compiling for ARMv6 (but not ARMv6-M), ARMv7-A, > > + ARMv7-R, or ARMv7-M, the default of the new option > > + -munaligned-accesses is on, which for some source > > How about "the new option...is active by default"? > > > + This will require the OS of those systems to enable such accesses > > Omit "of those systems" and spell out "operating system"? I see the tautology to which you allude. 8] Maybe "the kernel of those systems" is better? > > + (controlled by CP15 register c1, refer to ARM documentation). > > c1 > > > + Alternatively or for compatibility with OS versions that do not > > + enable unaligned accesses, all codes has to be compiled with > > "enable" -> "support" I wanted to emphasize that it's something you can configure to be enabled or disabled (with the kernel catching an exception), but maybe that doesn't really matter. Clarity matters and that part doesn't really have to explain in detail. > "all code has" I thought "codes" was a valid common reference to source code, but I guess not. Good suggestions, I hope I got them all below in one form or another: brgds, H-P Index: changes.html =================================================================== RCS file: /cvs/gcc/wwwdocs/htdocs/gcc-4.7/changes.html,v retrieving revision 1.113 diff -p -u -r1.113 changes.html --- changes.html 5 Jun 2012 11:03:53 -0000 1.113 +++ changes.html 10 Jun 2012 23:12:02 -0000 @@ -43,6 +43,16 @@
    • +
  • On ARM, when compiling for ARMv6 (but not ARMv6-M), ARMv7-A, + ARMv7-R, or ARMv7-M, the new option + -munaligned-accesses is active by default, which for + some source codes generates code that accesses memory on unaligned + adresses. This will require the kernel of those systems to enable + such accesses (controlled by CP15 register c1, refer + to ARM documentation). Alternatively or for compatibility with + kernels where unaligned accesses are not supported, all code has + to be compiled with -mno-unaligned-accesses.
    • +
  • Support on ARM for the legacy floating-point accelerator (FPA) and the mixed-endian floating-point format that it used has been obsoleted. The ports that still use this format have been obsoleted as well.