From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 56339 invoked by alias); 21 Oct 2015 12:06:02 -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 56319 invoked by uid 89); 21 Oct 2015 12:06:00 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-1.7 required=5.0 tests=AWL,BAYES_00,RCVD_IN_DNSWL_NONE,SPF_PASS autolearn=ham version=3.3.2 X-HELO: arjuna.pair.com Received: from arjuna.pair.com (HELO arjuna.pair.com) (209.68.5.131) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with (AES256-GCM-SHA384 encrypted) ESMTPS; Wed, 21 Oct 2015 12:05:59 +0000 Received: by arjuna.pair.com (Postfix, from userid 3006) id A3B5F8A3E0; Wed, 21 Oct 2015 08:05:55 -0400 (EDT) Received: from localhost (localhost [127.0.0.1]) by arjuna.pair.com (Postfix) with ESMTP id A31C28A3D3; Wed, 21 Oct 2015 08:05:55 -0400 (EDT) Date: Wed, 21 Oct 2015 12:12:00 -0000 From: Hans-Peter Nilsson To: Jeff Law cc: gcc-patches@gcc.gnu.org Subject: Re: [PATCH] Don't allow FSM threader to create irreducible loops unless it eliminates a multi-way branch In-Reply-To: <5627179A.6050009@redhat.com> Message-ID: References: <56251919.5050104@redhat.com> <5627179A.6050009@redhat.com> User-Agent: Alpine 2.02 (BSF 1266 2009-07-14) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII X-IsSubscribed: yes X-SW-Source: 2015-10/txt/msg02066.txt.bz2 On Tue, 20 Oct 2015, Jeff Law wrote: > On 10/20/2015 06:03 PM, Hans-Peter Nilsson wrote: > > I have no idea whether there's an actual bug related to the > > patch or something "just waiting to happen" and 16-bit-offsets > > just too close to the limits. Brief inspection of the generated > > assembly-code is, well, "inconclusive". Also, I'm travelling at > > the moment. > Feel free to pass it along when you get back. Thanks. Diffstat says the r228974 version is 104 lines less, so it's not obvious at *that* level and likely looks like an improvement except for the breakage and stretched jumptables. I'll open a proper bug-report soonish when less rushed. JFTR, it's worthwhile to check that we're not missing something that takes care of "all else equal, keep the target close to the jumptable". If we do miss that, that's an obvious enhancement more or less for all targets. If we already have that, there's likely a bug. brgds, H-P