From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <gcc-return-199909-listarch-gcc=gcc.gnu.org@gcc.gnu.org>
Received: (qmail 18103 invoked by alias); 14 Aug 2019 20:23:35 -0000
Mailing-List: contact gcc-help@gcc.gnu.org; run by ezmlm
Precedence: bulk
List-Id: <gcc.gcc.gnu.org>
List-Archive: <http://gcc.gnu.org/ml/gcc/>
List-Post: <mailto:gcc@gcc.gnu.org>
List-Help: <http://gcc.gnu.org/ml/>
Sender: gcc-owner@gcc.gnu.org
Received: (qmail 18092 invoked by uid 89); 14 Aug 2019 20:23:35 -0000
Authentication-Results: sourceware.org; auth=none
X-Spam-SWARE-Status: No, score=-2.6 required=5.0 tests=AWL,BAYES_00,SPF_PASS autolearn=ham version=3.3.1 spammy=
X-HELO: esa4.mentor.iphmx.com
Received: from esa4.mentor.iphmx.com (HELO esa4.mentor.iphmx.com) (68.232.137.252) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with ESMTP; Wed, 14 Aug 2019 20:23:34 +0000
IronPort-SDR: U+s8+fP2UKCsl4tm1zgMK38Y1aDWMbGQIAxCpf8GngwMKXCX3Qjnh1LvaByzOj5syl3su9ROJN dNx6/hBOdsUJ0UV+4QtDGbnF+GpXDGnqxWujeeC1m1EFJguVVwfQ9gn5f2xtHetBzM3wbbi6mI eTw3iQ1v+VCnVYSnsyqHWoM0SeDi6ELf1rmVkW8zQpEDMoo25ZdfrpvANYWX8Fc5kNr8BxoqRL 0D084tr9HrgsevLS+d+z7gt7p9nmp7i9o7IQYlUQri2EkLeVlvKw81lqxebNYLYlONBoSukdut u/E=
Received: from orw-gwy-01-in.mentorg.com ([192.94.38.165])  by esa4.mentor.iphmx.com with ESMTP; 14 Aug 2019 12:23:32 -0800
IronPort-SDR: uR9crbqX1JyTw8vRcqAbma3wVqLtn4Mew5IQdFzfhoThKtdJKWy9oKpQZ46xTzGS661cvIalYQ q2t5uTgxgy0f0/oZKDv3cSK04u4m0saufaBuVWxZLWbFaszIO3nzzCcWzV4l7vfSXDStT+/i4e aTDAO0yhuX8SxymKlM0FYjmmAgqRYx94yoezwzsn+wF7r5E+1wvhuvPGdT3dxVA04l3rTGTXAd NDABeRtS/ZKPzE7K6Xlyin5+rtxIry3Q8/I8V+mxFjgdpd+UA6m74aUvzwplamiiBBnp1sUIBZ S5c=
Date: Wed, 14 Aug 2019 20:23:00 -0000
From: Joseph Myers <joseph@codesourcery.com>
To: Segher Boessenkool <segher@kernel.crashing.org>
CC: Tejas Joshi <tejasjoshi9673@gmail.com>, <gcc@gcc.gnu.org>, Martin Jambor	<mjambor@suse.cz>, <hubicka@ucw.cz>
Subject: Re: Expansion of narrowing math built-ins into power instructions
In-Reply-To: <20190814202102.GI31406@gate.crashing.org>
Message-ID: <alpine.DEB.2.21.1908142022330.24610@digraph.polyomino.org.uk>
References: <alpine.DEB.2.21.1908082304570.5719@digraph.polyomino.org.uk> <CACMrGjB1UmfKuTCwGLi5oTapr4EM-JxbfVGr_GvwucWwfg0oYg@mail.gmail.com> <20190811165916.GX31406@gate.crashing.org> <CACMrGjAPa21OJ_ry+1HPyEQQbZhGOkQTVXwe=CvHsufc_ms_CQ@mail.gmail.com> <20190812175450.GB31406@gate.crashing.org> <alpine.DEB.2.21.1908122118140.18203@digraph.polyomino.org.uk> <20190812215224.GC31406@gate.crashing.org> <CACMrGjDbF8qyaF8_p5ofOT7gFRqMyOTtzxsKRM3r2aXX+8KS+A@mail.gmail.com> <20190814072127.GE31406@gate.crashing.org> <alpine.DEB.2.21.1908141608430.14831@digraph.polyomino.org.uk> <20190814202102.GI31406@gate.crashing.org>
User-Agent: Alpine 2.21 (DEB 202 2017-01-01)
MIME-Version: 1.0
Content-Type: text/plain; charset="US-ASCII"
Return-Path: joseph@codesourcery.com
X-SW-Source: 2019-08/txt/msg00103.txt.bz2

On Wed, 14 Aug 2019, Segher Boessenkool wrote:

> Does something like
>   float d; double a, b, x;
>   ...
>   d = fadd (a + x, b - x);
> work as wanted, with such a representation?  It would simplify (does it?) to
>   d = fadd (a, b);
> but is that allowed?

It's not allowed, but neither is simplifying (a + x) + (b - x) into (a + 
b), when contraction isn't allowed.

-- 
Joseph S. Myers
joseph@codesourcery.com