Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754846AbbETSQ6 (ORCPT ); Wed, 20 May 2015 14:16:58 -0400 Received: from e37.co.us.ibm.com ([32.97.110.158]:43832 "EHLO e37.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753853AbbETSQw (ORCPT ); Wed, 20 May 2015 14:16:52 -0400 Date: Wed, 20 May 2015 11:16:47 -0700 From: "Paul E. McKenney" To: c++std-parallel@accu.org Cc: Will Deacon , Linus Torvalds , Linux Kernel Mailing List , "linux-arch@vger.kernel.org" , "gcc@gcc.gnu.org" , p796231 , "mark.batty@cl.cam.ac.uk" , Peter Zijlstra , Ramana Radhakrishnan , David Howells , Andrew Morton , Ingo Molnar , "michaelw@ca.ibm.com" Subject: Re: [c++std-parallel-1632] Re: Compilers and RCU readers: Once more unto the breach! Message-ID: <20150520181647.GU6776@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com References: <20150520005510.GA23559@linux.vnet.ibm.com> <20150520024148.GD6776@linux.vnet.ibm.com> <20150520114745.GC11498@arm.com> <20150520121522.GH6776@linux.vnet.ibm.com> <20150520154617.GE11498@arm.com> <555CAE4B.4050202@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <555CAE4B.4050202@redhat.com> User-Agent: Mutt/1.5.21 (2010-09-15) X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 15052018-0025-0000-0000-00000AC60C65 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 910 Lines: 20 On Wed, May 20, 2015 at 04:54:51PM +0100, Andrew Haley wrote: > On 05/20/2015 04:46 PM, Will Deacon wrote: > > I'm not sure... you'd require the compiler to perform static analysis of > > loops to determine the state of the machine when they exit (if they exit!) > > in order to show whether or not a dependency is carried to subsequent > > operations. If it can't prove otherwise, it would have to assume that a > > dependency *is* carried, and it's not clear to me how it would use this > > information to restrict any subsequent dependency removing optimisations. > > It'd just convert consume to acquire. It should not need to, actually. Thanx, Paul -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/