From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 122954 invoked by alias); 20 Oct 2017 11:41:33 -0000 Mailing-List: contact libc-alpha-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: libc-alpha-owner@sourceware.org Received: (qmail 122935 invoked by uid 89); 20 Oct 2017 11:41:32 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-2.3 required=5.0 tests=AWL,BAYES_00,RCVD_IN_DNSWL_NONE,SPF_HELO_PASS,SPF_PASS autolearn=ham version=3.3.2 spammy=faithfully X-HELO: EUR02-AM5-obe.outbound.protection.outlook.com Authentication-Results: spf=none (sender IP is ) smtp.mailfrom=Szabolcs.Nagy@arm.com; Message-ID: <59E9E0E5.4000705@arm.com> Date: Fri, 20 Oct 2017 11:41:00 -0000 From: Szabolcs Nagy User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.8.0 MIME-Version: 1.0 To: Patrick McGehearty , Joseph Myers CC: nd@arm.com, libc-alpha@sourceware.org Subject: Re: [PATCH] Improves __ieee754_exp() performance by greater than 5x on sparc/x86. 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I can readily adjust the formating. What > you see is the formating used in the original source. > I've been uncomfortable with hex floats approach > as it only works for ieee754 representations > that use base 2. I admit that is most current machines. your entire algorithm depends on ieee754 binary representation, that's not a good reason for avoiding hexfloats. decimal floats are not even required to be correctly rounded by the compiler in iso c, they are only faithfully rounded, so this is a portability bug in the original source too, you can silently get completely wrong code generation because of it. > And the prior ieee754 exp table uses hex format. > My second reason for resisting the change is my philosophy > when porting code is that every change without a good reason > is an opportunity to introduce errors without corresponding benefit. > > If you feel strongly about suing hex constants, I will make an effort > to convert these values to hex format. This conversion seems likely > to require the most effort on my part. >