From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 59534 invoked by alias); 7 Sep 2016 23:00:30 -0000 Mailing-List: contact gcc-patches-help@gcc.gnu.org; run by ezmlm Precedence: bulk List-Id: List-Archive: List-Post: List-Help: Sender: gcc-patches-owner@gcc.gnu.org Received: (qmail 59505 invoked by uid 89); 7 Sep 2016 23:00:28 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-3.0 required=5.0 tests=BAYES_00,RP_MATCHES_RCVD,SPF_HELO_PASS autolearn=ham version=3.3.2 spammy=Hx-languages-length:704 X-HELO: mx1.redhat.com Received: from mx1.redhat.com (HELO mx1.redhat.com) (209.132.183.28) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with ESMTP; Wed, 07 Sep 2016 23:00:18 +0000 Received: from int-mx10.intmail.prod.int.phx2.redhat.com (int-mx10.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 560C5B6E92; Wed, 7 Sep 2016 23:00:14 +0000 (UTC) Received: from localhost.localdomain (vpn1-4-170.ams2.redhat.com [10.36.4.170]) by int-mx10.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id u87N0CYM001823; Wed, 7 Sep 2016 19:00:13 -0400 Subject: Re: Correct libgcc complex multiply excess precision handling To: Joseph Myers , gcc-patches@gcc.gnu.org References: From: Bernd Schmidt Message-ID: Date: Wed, 07 Sep 2016 23:01:00 -0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.2.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit X-IsSubscribed: yes X-SW-Source: 2016-09/txt/msg00415.txt.bz2 On 09/07/2016 11:48 PM, Joseph Myers wrote: > libgcc complex multiply is meant to eliminate excess > precision from certain internal values by forcing them to memory in > exactly those cases where the type has excess precision. But in > https://gcc.gnu.org/ml/gcc-patches/2014-09/msg01894.html I > accidentally inverted the logic so that values get forced to memory in > exactly the cases where it's not needed. (This is a pessimization in > the no-excess-precision case, in principle could lead to bad results > depending on code generation in the excess-precision case. Note: I do > not have a test demonstrating bad results.) Ok. Bernd