From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 72948 invoked by alias); 2 Sep 2019 11:30:45 -0000 Mailing-List: contact gcc-help@gcc.gnu.org; run by ezmlm Precedence: bulk List-Id: List-Archive: List-Post: List-Help: Sender: gcc-owner@gcc.gnu.org Received: (qmail 72936 invoked by uid 89); 2 Sep 2019 11:30:45 -0000 Authentication-Results: sourceware.org; auth=none X-Spam-SWARE-Status: No, score=-2.2 required=5.0 tests=AWL,BAYES_00,RCVD_IN_DNSWL_NONE autolearn=ham version=3.3.1 spammy=valuable, H*f:sk:ri6h867, H*f:sk:mptimqm, doubledouble X-HELO: gate.crashing.org Received: from gate.crashing.org (HELO gate.crashing.org) (63.228.1.57) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with ESMTP; Mon, 02 Sep 2019 11:30:43 +0000 Received: from gate.crashing.org (localhost.localdomain [127.0.0.1]) by gate.crashing.org (8.14.1/8.14.1) with ESMTP id x82BUVBO024543; Mon, 2 Sep 2019 06:30:31 -0500 Received: (from segher@localhost) by gate.crashing.org (8.14.1/8.14.1/Submit) id x82BUUZN024542; Mon, 2 Sep 2019 06:30:30 -0500 Date: Mon, 02 Sep 2019 11:30:00 -0000 From: Segher Boessenkool To: Tejas Joshi Cc: gcc@gcc.gnu.org, Martin Jambor , hubicka@ucw.cz, joseph@codesourcery.com Subject: Re: Expansion of narrowing math built-ins into power instructions Message-ID: <20190902113030.GY31406@gate.crashing.org> References: <20190822095620.GK31406@gate.crashing.org> <20190825164717.GO31406@gate.crashing.org> <20190826074211.GQ31406@gate.crashing.org> <20190830203525.GS31406@gate.crashing.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.4.2.3i X-IsSubscribed: yes X-SW-Source: 2019-09/txt/msg00007.txt.bz2 Hi Tejas, On Mon, Sep 02, 2019 at 08:55:28AM +0530, Tejas Joshi wrote: > On Sat, 31 Aug 2019 at 02:05, Segher Boessenkool > wrote: > > > > > > > > [ Please don't top-post ] > > > > (I delete everything under your signature, without looking, assuming you > > just forgot to). > > Oh sorry, I didn't know the reply button does evil things. :-) You're supposed to write your email as if the time reading it is more valuable than the time writing it. You can afford to spend a few seconds deleting some stuff, or checking that what you wrote is good, etc. There is only one you, and there are many people reading this. > > If long double is double, faddl is the same as fadd, and daddl is just > > normal addition. > > > > If long double is double-double, faddl can be done as fadd on the first > > double precision component of both args, and daddl is just normal addition > > of those. > > > > If long double is IEEE QP, then it is more interesting :-) > > On what conditions does the mapping of long double to double/ > double-double or IEEE QP changes or depends, so that I can test it. gcc -Q --help=target | grep long -mlong-double-64 is to select double, and -mlong-double-128 says to use something 128 bits. These are not mentioned in the manual, and GCC often says it has a different number of bits selected, hrm. I'll open a PR. When having a 128-bit long double, -mabi=ibmlongdouble says to use the double-double format, and -mabi=ieeelongdouble says to use IEEE QP FP. HTH, Segher