From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 3228 invoked by alias); 14 Sep 2016 13:55:22 -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 3204 invoked by uid 89); 14 Sep 2016 13:55:20 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-4.0 required=5.0 tests=AWL,BAYES_00,RP_MATCHES_RCVD autolearn=ham version=3.3.2 spammy=young 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; Wed, 14 Sep 2016 13:55:19 +0000 Received: from gate.crashing.org (localhost.localdomain [127.0.0.1]) by gate.crashing.org (8.14.1/8.13.8) with ESMTP id u8EDtGs4009162; Wed, 14 Sep 2016 08:55:16 -0500 Received: (from segher@localhost) by gate.crashing.org (8.14.1/8.14.1/Submit) id u8EDtFgf009159; Wed, 14 Sep 2016 08:55:15 -0500 Date: Wed, 14 Sep 2016 14:01:00 -0000 From: Segher Boessenkool To: Bernd Schmidt Cc: Jeff Law , gcc-patches@gcc.gnu.org, dje.gcc@gmail.com Subject: Re: [PATCH 5/9] regrename: Don't run if function was separately shrink-wrapped Message-ID: <20160914135515.GF4896@gate.crashing.org> References: <7e74a019-d477-348f-2dc6-744e1db38f2f@redhat.com> <20160909204107.GC21356@gate.crashing.org> <14ff3e40-4c2c-7e8b-b822-07ff3575b771@redhat.com> <20160910064052.GA7255@gate.crashing.org> <32231187-0fa2-815d-ab89-7e3d15b646d4@redhat.com> <20160914130458.GA4896@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: 2016-09/txt/msg00835.txt.bz2 On Wed, Sep 14, 2016 at 03:08:21PM +0200, Bernd Schmidt wrote: > On 09/14/2016 03:04 PM, Segher Boessenkool wrote: > >Then rs6000 (and many other ports probably) will just turn it off again. > >It is actively harmful. > > The data that was posted showed a code size decrease on a number of > targets. I'm really not sure where this irrational hate for regrename > comes from. It increases the number of active, "young" registers per thread. There is no irrational hate. Regrename is simply a de-optimisation on some (heavily) out-of-order targets. Not by much, but not a win either. We would rather do without it, on current CPUs at least (and I doubt this will change soon, but we'll see). (It also makes the generated code much harder to read, but you know that). Segher