From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:41890) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1cjGNn-0000km-5T for qemu-devel@nongnu.org; Wed, 01 Mar 2017 21:22:19 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1cjGNk-0006ub-26 for qemu-devel@nongnu.org; Wed, 01 Mar 2017 21:22:19 -0500 Sender: Richard Henderson References: <1488381854-7275-1-git-send-email-nikunj@linux.vnet.ibm.com> <20170302002933.GL12571@umbus.fritz.box> From: Richard Henderson Message-ID: <32926f1f-ec40-420f-210b-8f5991cc9d67@twiddle.net> Date: Thu, 2 Mar 2017 13:22:05 +1100 MIME-Version: 1.0 In-Reply-To: <20170302002933.GL12571@umbus.fritz.box> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH v1] target/ppc: rewrite f[n]m[add, sub] using float64_muladd List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: David Gibson , Nikunj A Dadhania Cc: qemu-ppc@nongnu.org, qemu-devel@nongnu.org, bharata@linux.vnet.ibm.com On 03/02/2017 11:29 AM, David Gibson wrote: > On Wed, Mar 01, 2017 at 08:54:14PM +0530, Nikunj A Dadhania wrote: >> Use the softfloat api for fused multiply-add. Also, generate VXISI using >> a helper function by computing intermediate result. > > Um.. I really need some information on why this is a good thing to > do. Is it a bugfix? Enhancement? Simplification? Looks like a bugfix to me. Previously we were attempting the operation via float128 as an intermediate type, which can result in double rounding errors. r~