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 D7E3E138247 for ; Mon, 16 Dec 2013 00:30:59 +0000 (UTC) Received: from pigeon.gentoo.org (localhost [127.0.0.1]) by pigeon.gentoo.org (Postfix) with SMTP id 2C11EE0BBA; Mon, 16 Dec 2013 00:30:53 +0000 (UTC) Received: from smtp.gentoo.org (smtp.gentoo.org [140.211.166.183]) (using TLSv1 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by pigeon.gentoo.org (Postfix) with ESMTPS id 38C77E0BA8 for ; Mon, 16 Dec 2013 00:30:52 +0000 (UTC) Received: from mail-qc0-f177.google.com (mail-qc0-f177.google.com [209.85.216.177]) (using TLSv1 with cipher ECDHE-RSA-RC4-SHA (128/128 bits)) (No client certificate requested) (Authenticated sender: mattst88) by smtp.gentoo.org (Postfix) with ESMTPSA id 635AC33DA56 for ; Mon, 16 Dec 2013 00:30:51 +0000 (UTC) Received: by mail-qc0-f177.google.com with SMTP id m20so3156850qcx.22 for ; Sun, 15 Dec 2013 16:30:49 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=mime-version:in-reply-to:references:from:date:message-id:subject:to :content-type; bh=8rIYwnuA0PFBpLRY4lwV5LRKjWbTir0TXdcLX2tfRrI=; b=Ly0f7q2/07D3SnvUZlFSDtxJb6A6o16JPg70LIDGRY5h/Kc++yPIlLywg9IItxwvJQ HixPTrBecKpOHJ/LUt0mxY5JkzHnJNrMOjxHu5/X7MYGmbmH7Iet64JITZe06X3n3ovx IIHpzbwR1zebs4tspbCj5Ocy62aaCOyYjDiIg2jwk/on8yqOz7OFS9ZVaADz735JicXj Pn4tYCSedywr52KYGPHysi/xO9eAkx6n6XDC19YdHGF3fh23JZ5CPaC6IhhXrzJPoTKA CthMjC7nVoS+fQ/uWCvLOej7JxHComDpi09wQhU4hyvRB/u0dnl72I6N8uuL2SfsShP9 hF7Q== X-Received: by 10.49.17.232 with SMTP id r8mr27789678qed.74.1387153849696; Sun, 15 Dec 2013 16:30:49 -0800 (PST) Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-Id: Gentoo Linux mail X-BeenThere: gentoo-dev@lists.gentoo.org Reply-to: gentoo-dev@lists.gentoo.org MIME-Version: 1.0 Received: by 10.229.178.129 with HTTP; Sun, 15 Dec 2013 16:30:29 -0800 (PST) In-Reply-To: <201312160120.03185.dilfridge@gentoo.org> References: <201312160120.03185.dilfridge@gentoo.org> From: Matt Turner Date: Sun, 15 Dec 2013 16:30:29 -0800 Message-ID: Subject: Re: [gentoo-dev] New global use flags: 3dnowext, mmxext, ssse3, sse4_1, avx, avx2 To: gentoo-dev@lists.gentoo.org Content-Type: text/plain; charset=ISO-8859-1 X-Archives-Salt: 09661c35-69e7-48f6-981e-aad805789564 X-Archives-Hash: e1fa71d3c399669632cc91046e150c08 On Sun, Dec 15, 2013 at 4:20 PM, Andreas K. Huettel wrote: > Am Montag, 16. Dezember 2013, 00:34:13 schrieb Matt Turner: >> 3dnow: Use the 3DNow! instruction set >> 3dnowext: Use the Enhanced 3DNow! instruction set >> mmx: Use the MMX instruction set >> mmxext: Use the Extended MMX instruction set (intersection of Enhanced >> 3DNow! and SSE instruction sets) (3dnowext or sse in cpuinfo) >> sse: Use the SSE instruction set >> sse2: Use the SSE2 instruction set >> sse3: Use the SSE3 instruction set (pni in cpuinfo) >> ssse3: Use the SSSE3 instruction set >> sse4_1: Use the SSE 4.1 instruction set >> avx: Use the AVX instruction set >> avx2: Use the AVX2 instruction set > > What's the point of these flags? > (or to be more precise, are they really justified whenever they are used?) > > Usually the set of cpu instructions should be controlled by your CFLAGS, and > I've been actively patching packages (that do not do manually coded assembly) > to make such flags unnecessary. Often they're for enabling assembly code that uses these instruction sets. For pixman, a package that I'm very familiar with, they turn on code using these instruction sets using intrinsics in C. I believe they are justified. If the package simply uses the flag to add an -m flag to CFLAGS, then we should definitely remove it. If I recall correctly, I have only seen one instance of this.