From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from dan.rpsys.net (5751f4a1.skybroadband.com [87.81.244.161]) by mail.openembedded.org (Postfix) with ESMTP id 07A67731FB for ; Mon, 11 Jan 2016 23:07:40 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by dan.rpsys.net (8.14.4/8.14.4/Debian-4.1ubuntu1) with ESMTP id u0BN7Mr0027716; Mon, 11 Jan 2016 23:07:39 GMT Received: from dan.rpsys.net ([127.0.0.1]) by localhost (dan.rpsys.net [127.0.0.1]) (amavisd-new, port 10024) with LMTP id 7MB7iZ1suNi3; Mon, 11 Jan 2016 23:07:39 +0000 (GMT) Received: from hex ([192.168.3.34]) (authenticated bits=0) by dan.rpsys.net (8.14.4/8.14.4/Debian-4.1ubuntu1) with ESMTP id u0BN7Z68027771 (version=TLSv1/SSLv3 cipher=AES128-GCM-SHA256 bits=128 verify=NOT); Mon, 11 Jan 2016 23:07:36 GMT Message-ID: <1452553655.7598.206.camel@linuxfoundation.org> From: Richard Purdie To: Khem Raj , Phil Blundell Date: Mon, 11 Jan 2016 23:07:35 +0000 In-Reply-To: <4E2CA517-1339-416B-832B-AB2EFF04CEE6@gmail.com> References: <1452205752-6353-1-git-send-email-armccurdy@gmail.com> <1452205752-6353-4-git-send-email-armccurdy@gmail.com> <1452210004.2002.129.camel@pbcl.net> <4E2CA517-1339-416B-832B-AB2EFF04CEE6@gmail.com> X-Mailer: Evolution 3.16.5-1ubuntu3.1 Mime-Version: 1.0 Cc: openembedded-core@lists.openembedded.org Subject: Re: [PATCH v2 3/4] libav.inc: duplicate armv7a over-rides for armv7ve 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: Mon, 11 Jan 2016 23:07:41 -0000 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit On Mon, 2016-01-11 at 14:58 -0800, Khem Raj wrote: > > On Jan 7, 2016, at 3:40 PM, Phil Blundell wrote: > > > > On Thu, 2016-01-07 at 14:29 -0800, Andre McCurdy wrote: > > > FULL_OPTIMIZATION_armv7a = "-fexpensive-optimizations -fomit > > > -frame-pointer -O4 -ffast-math" > > > +FULL_OPTIMIZATION_armv7ve = "-fexpensive-optimizations -fomit > > > -frame-pointer -O4 -ffast-math" > > > > O4 ? may be just replace this whole thing with -Ofast now a days > -fexpensive-optimizations is enabled at -O2,-O3 anyway same for fomit > -frame-pointer and -Ofast turns on > feast-match on top of -O3 > > > I wonder if this would be better as just FULL_OPTIMIZATION_arm. > > That > > said, the OPTIMIZATION variables are primarily distro knobs and > > it's not > > entirely clear that individual packages ought to be overriding them > > at > > all. > > > > Does anybody know whether there is any actual science behind the > > use of > > those flags on armv7a specifically? > > it came into ffmpeg circa 2008 and proliferated into related > components primarily to support vectorization and neon > which was quite nascent for ARM architecture in those days in gcc. > Today if you were to configure libav with default options > then it uses mainly -fomit-frame-pointer-O3 -fno-math-errno -fno > -signed-zeros -fno-tree-vectorize > > which is primarily -Ofast -fno-tree-vectorize I have to admit that my personal instinct on these is simply to remove them. I doubt they're buying much now and if people really want to tune specific recipes by hand they still can do so from their local/distro config. Cheers, Richard