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[66.111.4.29]) by mx.google.com with ESMTPS id j20-v6si4248144pll.86.2018.03.21.13.16.52 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 21 Mar 2018 13:16:52 -0700 (PDT) Received-SPF: pass (google.com: domain of cota@braap.org designates 66.111.4.29 as permitted sender) client-ip=66.111.4.29; Authentication-Results: mx.google.com; dkim=pass header.i=@braap.org header.s=mesmtp header.b=T8/iQpjP; dkim=pass header.i=@messagingengine.com header.s=fm2 header.b=ctI+GrmO; spf=pass (google.com: domain of cota@braap.org designates 66.111.4.29 as permitted sender) smtp.mailfrom=cota@braap.org Received: from compute4.internal (compute4.nyi.internal [10.202.2.44]) by mailout.nyi.internal (Postfix) with ESMTP id 27D2A214CE; Wed, 21 Mar 2018 16:16:52 -0400 (EDT) Received: from frontend1 ([10.202.2.160]) by compute4.internal (MEProxy); Wed, 21 Mar 2018 16:16:52 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=braap.org; h=cc :content-transfer-encoding:content-type:date:from:in-reply-to :message-id:mime-version:references:subject:to:x-me-sender :x-me-sender:x-sasl-enc; s=mesmtp; bh=nblGJnBRifQ4hjO38nbiChsolu 5z/ZAfscy357YyB1E=; b=T8/iQpjPc9Iq9MjIM3oLCW/wY/QB/yB6NQftmb5cq+ gdeGbLjrUQmYhzAfiZf1sYmlW8No2l3+lTX/9SXL56tCBfrguW1TwKun6yDOW0/n BKMzUtmFp0k5X9kAAAkbOC4sorZZ0c1gQ5rGtQVZzMFrWviD/LGAkD7WwpK3L+RS M= DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d= messagingengine.com; h=cc:content-transfer-encoding:content-type :date:from:in-reply-to:message-id:mime-version:references :subject:to:x-me-sender:x-me-sender:x-sasl-enc; s=fm2; bh=nblGJn BRifQ4hjO38nbiChsolu5z/ZAfscy357YyB1E=; b=ctI+GrmOvgpD/RUlQ0Q+U0 9x4y3BTxK61np7iUQvhigCV3XIjKke4VtVYF9KWbDnlKSOBtqvoQmaN52Sj5N4eG yznAJgYUBy3A4Mt7AVJ0MExie+PPe09X+SQYMgNzyW+8wWjN5LHiQy+S5eX9LIzq gYdc7tq15CTgsMUg/BxYy2nP12ltpOROB3fpknnfIYYpGMbKsoIEO/r4LOJ6gWs0 H1naoDKpW+++LM7PDK77Iud8naha0cwJ99scGfMekHnWvInSDFkAVVap8bXMvR9P dSQ/Cnwsrr/tgT19KUGQG9rZQeBqSIGgee7L32mOMqQcVTOj8NSR9ZCFJbOPgyGg == X-ME-Sender: Received: from localhost (flamenco.cs.columbia.edu [128.59.20.216]) by mail.messagingengine.com (Postfix) with ESMTPA id D3A647E16E; Wed, 21 Mar 2018 16:16:51 -0400 (EDT) Date: Wed, 21 Mar 2018 16:16:51 -0400 From: "Emilio G. Cota" To: Alex =?iso-8859-1?Q?Benn=E9e?= Cc: peter.maydell@linaro.org, richard.henderson@linaro.org, Peter Crosthwaite , Riku Voipio , qemu-devel@nongnu.org, Laurent Vivier , "open list:ARM" , Paolo Bonzini , Aurelien Jarno , Richard Henderson Subject: Re: [Qemu-devel] [PATCH] fpu/softfloat: use hardware sqrt if we can (EXPERIMENT!) Message-ID: <20180321201651.GA32458@flamenco> References: <20180220210137.18018-1-alex.bennee@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20180220210137.18018-1-alex.bennee@linaro.org> User-Agent: Mutt/1.5.24 (2015-08-30) X-TUID: P31QEVN1h/WS On Tue, Feb 20, 2018 at 21:01:37 +0000, Alex Bennée wrote: > This is an attempt to save some of the cost of sqrt by using the > inbuilt support of the host hardware. The idea is assuming we start > with a valid input we can use the hardware. If any tininess issues > occur this will trip and FPU exception where: > > - we turn off cpu->use_host_fpu > - mask the FPU exceptions > - return to what we were doing Please see this thread for an alternative approach: [Qemu-devel] [PATCH v1 00/14] fp-test + hostfloat https://lists.gnu.org/archive/html/qemu-devel/2018-03/msg05908.html Emilio