From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <gcc-patches-return-400115-listarch-gcc-patches=gcc.gnu.org@gcc.gnu.org>
Received: (qmail 107273 invoked by alias); 9 Jun 2015 11:12:32 -0000
Mailing-List: contact gcc-patches-help@gcc.gnu.org; run by ezmlm
Precedence: bulk
List-Id: <gcc-patches.gcc.gnu.org>
List-Archive: <http://gcc.gnu.org/ml/gcc-patches/>
List-Post: <mailto:gcc-patches@gcc.gnu.org>
List-Help: <mailto:gcc-patches-help@gcc.gnu.org>
Sender: gcc-patches-owner@gcc.gnu.org
Received: (qmail 107208 invoked by uid 89); 9 Jun 2015 11:12:32 -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,KAM_LAZY_DOMAIN_SECURITY,T_RP_MATCHES_RCVD autolearn=no version=3.3.2
X-HELO: mail2-relais-roc.national.inria.fr
Received: from mail2-relais-roc.national.inria.fr (HELO mail2-relais-roc.national.inria.fr) (192.134.164.83) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with (CAMELLIA256-SHA encrypted) ESMTPS; Tue, 09 Jun 2015 11:12:30 +0000
Received: from stedding.saclay.inria.fr (HELO stedding) ([193.55.250.194])  by mail2-relais-roc.national.inria.fr with ESMTP/TLS/AES128-SHA; 09 Jun 2015 13:12:27 +0200
Received: from glisse (helo=localhost)	by stedding with local-esmtp (Exim 4.85)	(envelope-from <marc.glisse@inria.fr>)	id 1Z2HSF-0004By-27; Tue, 09 Jun 2015 13:12:27 +0200
Date: Tue, 09 Jun 2015 11:46:00 -0000
From: Marc Glisse <marc.glisse@inria.fr>
To: Richard Biener <richard.guenther@gmail.com>
cc: Marek Polacek <polacek@redhat.com>, Jakub Jelinek <jakub@redhat.com>,     GCC Patches <gcc-patches@gcc.gnu.org>, Richard Biener <rguenther@suse.de>
Subject: Re: [PATCH] Optimize (CST1 << A) == CST2 (PR tree-optimization/66299)
In-Reply-To: <CAFiYyc2vfBzHGHQEkvRujiE2z-brW4J3P0R+TyjQuy44PZj0-A@mail.gmail.com>
Message-ID: <alpine.DEB.2.20.1506091305110.9052@stedding.saclay.inria.fr>
References: <20150528121545.GE27320@redhat.com> <20150528123436.GM10247@tucnak.redhat.com> <alpine.DEB.2.11.1505282124310.2177@laptop-mg.saclay.inria.fr> <20150608151055.GR2756@redhat.com> <alpine.DEB.2.20.1506081901550.28961@stedding.saclay.inria.fr> <CAFiYyc2vfBzHGHQEkvRujiE2z-brW4J3P0R+TyjQuy44PZj0-A@mail.gmail.com>
User-Agent: Alpine 2.20 (DEB 67 2015-01-07)
MIME-Version: 1.0
Content-Type: text/plain; charset=US-ASCII; format=flowed
X-SW-Source: 2015-06/txt/msg00650.txt.bz2

On Tue, 9 Jun 2015, Richard Biener wrote:

>> Tweaking it so that (6<<X)==0 becomes X>=31 for TYPE_OVERFLOW_WRAPS and
>> false for TYPE_OVERFLOW_UNDEFINED is probably more controversial.
>
> Hm, yes.  I think signed overflow != shift amount overflow, so testing 
> the overflow macros for this isn't valid.

Would it be ok to always turn it to X>=31 then? (the value 31 is 
conveniently already computed in 'cand')

-- 
Marc Glisse