From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from lists.gentoo.org (pigeon.gentoo.org [208.92.234.80]) by finch.gentoo.org (Postfix) with ESMTP id CAA29138989 for ; Sat, 2 May 2015 12:10:45 +0000 (UTC) Received: from pigeon.gentoo.org (localhost [127.0.0.1]) by pigeon.gentoo.org (Postfix) with SMTP id D598AE0880; Sat, 2 May 2015 12:10:37 +0000 (UTC) Received: from mail-wg0-f43.google.com (mail-wg0-f43.google.com [74.125.82.43]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by pigeon.gentoo.org (Postfix) with ESMTPS id 9C5E2E0875 for ; Sat, 2 May 2015 12:10:36 +0000 (UTC) Received: by wgin8 with SMTP id n8so110997356wgi.0 for ; Sat, 02 May 2015 05:10:35 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=googlemail.com; s=20120113; h=message-id:date:from:user-agent:mime-version:to:subject:references :in-reply-to:content-type:content-transfer-encoding; bh=CLRPY/sv4MTDKOVFE8Hb4mQX2C6nigEJ62YyPDVkI0w=; b=juIRFOfTCmtdPpjtzMZOycQsQ/+F/ssjaI8/bGahltsWyyUDuL127bwZWQDF0yT+YG 8FIMOMsXPdZLwg65HNQrG7BC68w8N19oD3cuGirwKw6q1sZwYQNz8knwgA2AwiUEIUcF /H1s50Jm8L+JkEvFTFf84o/jM84AhT/29hmXCf/fR2Oc15g8Z1yMIFKzWBqAMcqKHz/z KaFqFtHTSXBGug+xWmJ4Wwb3CGztxw8CyK6EN+kHTemC3Ihp2l0//2WqeZN2xRQtD2pQ 19CQPnP/HqZ2GHJjj8999Mv4zi16oj5QU+hzrZxriXHMf5V3V213YSDdcI3iCZ7UMWr/ tHUA== X-Received: by 10.180.99.166 with SMTP id er6mr4580017wib.58.1430568635600; Sat, 02 May 2015 05:10:35 -0700 (PDT) Received: from [192.168.178.21] (p4FC11A75.dip0.t-ipconnect.de. [79.193.26.117]) by mx.google.com with ESMTPSA id u9sm11559077wjx.15.2015.05.02.05.10.34 for (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Sat, 02 May 2015 05:10:34 -0700 (PDT) Message-ID: <5544BEB9.9050103@googlemail.com> Date: Sat, 02 May 2015 14:10:33 +0200 From: Volker Armin Hemmann User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.6.0 Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-Id: Gentoo Linux mail X-BeenThere: gentoo-user@lists.gentoo.org Reply-to: gentoo-user@lists.gentoo.org MIME-Version: 1.0 To: gentoo-user@lists.gentoo.org Subject: Re: [gentoo-user] Re: CFLAGs for kernel compilation References: <5540C101.70906@ramses-pyramidenbau.de> <20150430123819.b72d8b39bd60a912b7c7fde5@gentoo.org> <20150501104402.27d943c901f638942262d3d1@gentoo.org> <5544B2AB.1010700@googlemail.com> <5544B6F2.8040508@googlemail.com> In-Reply-To: Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit X-Archives-Salt: 22703d60-daf3-45a0-b468-ce4de9591928 X-Archives-Hash: 92861a16a4604a822ec144806856f227 Am 02.05.2015 um 14:06 schrieb Nikos Chantziaras: > On 02/05/15 14:37, Volker Armin Hemmann wrote: >> Am 02.05.2015 um 13:25 schrieb Nikos Chantziaras: >>>>> >>>>> The kernel uses -O2 and several -march variants (e.g. -march=core2). >>>>> Several other options are used to prevent GCC from generating >>>>> unsuitable code. >>>>> >>>>> Specifying another -march variant does not affect the optimizer >>>>> though. It only affects the code generator. If you don't modify the >>>>> other CFLAGS and only change -march, you will not get FP instructions >>>>> unless you use FP in the code. >>>> >>>> http://www.agner.org/optimize/calling_conventions.pdf >>> >>> Not sure what you're trying to say. >>> >> >> that simd is not save in kernel if not carefully guarded. >> >> Really people, just don't fuck around with the cflags. > > I still fail to see the relevance. Unless you mean using a different > -O level. In that case, yes. You shouldn't. But I was talking about > -march. > you said this > > (note that SIMD is not FP and is perfectly fine in the kernel.) and I have shown you that you are wrong.