From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-vk0-f68.google.com (mail-vk0-f68.google.com [209.85.213.68]) by mail.openembedded.org (Postfix) with ESMTP id 4173C60745 for ; Tue, 26 Jun 2018 19:52:19 +0000 (UTC) Received: by mail-vk0-f68.google.com with SMTP id l64-v6so10762521vkl.12 for ; Tue, 26 Jun 2018 12:52:20 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:in-reply-to:references:from:date:message-id:subject:to :cc; bh=9woHplijyBNjHH6TwdKYUyy+LkWt8NXla9p0T2w/jb8=; b=cI1IVFVNTW9t5ShhE7brKgDOjlinpIGa/jV7xJW2O57qkBYonSbO+IyOim8nhSNe7s zLhiEshCzI1PnlefkpMzUI1enzJLGzn/0CTxhn05rvMUhMmwiBIfxdshKiIITBG3Aira t99CKoL3HA9b/H/75UX1d5+FdZYKsF8yrpQ+/X4U/xvhc1ogQfE12wRULafgmOs869HM RqC2D54sn00DftcFJw7ZyDwoEFjwPjyP9tVHo5ydYjsLJsAtfbgaMT14bMTedPu0hgPR 1QWENuYMJd4uQgoMS3izGhcLki/chU7gGO/fsDxsCFqkupHCzc9nQn2LUg0tcECvSEFN nl5Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:in-reply-to:references:from:date :message-id:subject:to:cc; bh=9woHplijyBNjHH6TwdKYUyy+LkWt8NXla9p0T2w/jb8=; b=Avta99ilubscHwhPRB2ntSjGQa1EG1C847xB68fUgzHevxLeH+DrWxDXgTvoK1sJGz S6v7XOSw/WzznBiruTgx6Md+KU19h6Q4kUqthAqW4PauYH34pVGP1DVTZyouem1+6PbH 8ZUMU0aofijUx1vtO7LLsN8oB9gQ8/5Ff2ZAflQQq5/NDquxfN1L9ef+l2YeK82MnNQP Ku/GTkN204DBZIkeHWpe6moSXUqP/wg/WxuLtA1xU5Z8XKHIspriNa6khVHNdqbqmOhm 0g2jBAsM+zbtZF5iaid0Z+mPcUZlXAm0M4dxp/0saG3KldIBHQOjH6SQ7ypjXyH8z3Xx 8q4w== X-Gm-Message-State: APt69E1904FzXLlvz3lPkYp8c+/1EBbv0tl/dacb2U3m05ng4T8niCGe BF6ZxUmpt5XuxGJk0SoLrRn10t37Qq7nTH0P3mc= X-Google-Smtp-Source: AAOMgpdUmtj0Cllhyo8UntvbX2csKAdX2E/tcWPOyqhZc2U4S7nNqVYCDbCHxLDLuFq28Q7XfjBlKErfmfcIJAZIo+k= X-Received: by 2002:a1f:9757:: with SMTP id z84-v6mr1708173vkd.174.1530042740027; Tue, 26 Jun 2018 12:52:20 -0700 (PDT) MIME-Version: 1.0 Received: by 2002:ab0:28a:0:0:0:0:0 with HTTP; Tue, 26 Jun 2018 12:52:19 -0700 (PDT) In-Reply-To: References: From: Andre McCurdy Date: Tue, 26 Jun 2018 12:52:19 -0700 Message-ID: To: Patches and discussions about the oe-core layer Subject: Re: [PATCH] arch-armv7a.inc: default to Thumb2 instruction set for armv7a and above X-BeenThere: openembedded-core@lists.openembedded.org X-Mailman-Version: 2.1.12 Precedence: list List-Id: Patches and discussions about the oe-core layer List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 26 Jun 2018 19:52:19 -0000 Content-Type: text/plain; charset="UTF-8" On Mon, Jun 4, 2018 at 2:33 PM, Andre McCurdy wrote: > On Tue, May 22, 2018 at 3:33 AM, Khem Raj wrote: >> On Tue, May 22, 2018 at 5:58 AM, wrote: >>> Andre McCurdy wrote: >>>> Although there may still be specific cases which can benefit from the >>>> ARM instruction set, the Thumb2 instruction set is generally a better >>>> default for armv7a class CPUs. Distros such as Debian and Fedora have >>>> been targeting Thumb2 by default for some time. >>>> >>>> Note that setting ARM_INSTRUCTION_SET has no effect unless >>>> TUNE_FEATURES contains "thumb" (which is controlled by the "t" suffix >>>> in DEFAULTTUNE, e.g. armv7vehf-neon -vs- armv7vethf-neon, etc) so out >>>> of tree machine configs may need to update their DEFAULTTUNE to take >>>> advantage of this change. >>> >>> I recently ran into some major problems due to thumb vs arm. It turns out glibc doesn't support systems with thumb disabled anymore. See this bug report for details: >>> >>> https://sourceware.org/bugzilla/show_bug.cgi?id=23031 >>> >>> This might be useful input for this discussion also. >>> > > Thanks to everyone for the feedback! > > I've reviewed Martin's examples of distros which control > ARM_INSTRUCTION_SET and don't see anything which would conflict with > this patch. > > I've also reviewed the glibc bug (Thumb2 instructions used in glibc > even when glibc is compiled for ARM) and it's a positive in this > discussion. It means that anyone running without Thumb support enabled > in their kernel will already have run into issues simply by using > glibc in rocko. The glibc bug has therefore "cleaned the pipes" for a > more formal switch to using Thumb2 instructions in user space. > > So, unless there's any further feedback, I think this patch is ready to merge. Ping. Richard, Ross, please let me know if anything else needs to be done before merging this update.