From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stephen Hemminger Subject: Re: [PATCH 0/5] remove usage of register keyword in C Date: Wed, 1 Aug 2018 14:03:56 -0700 Message-ID: <20180801140356.5ac88c43@xeon-e3> References: <20180731163059.27085-1-stephen@networkplumber.org> <20180731164840.GD5211@6wind.com> <20180731110737.38555f02@xeon-e3> <50204CDA-B4AD-44C8-AB07-2FE9C2A412C0@mellanox.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Cc: Adrien Mazarguil , "dev@dpdk.org" To: Yongseok Koh Return-path: Received: from mail-pg1-f194.google.com (mail-pg1-f194.google.com [209.85.215.194]) by dpdk.org (Postfix) with ESMTP id BA26F1B3A1 for ; Wed, 1 Aug 2018 23:03:59 +0200 (CEST) Received: by mail-pg1-f194.google.com with SMTP id n7-v6so4117pgq.4 for ; Wed, 01 Aug 2018 14:03:59 -0700 (PDT) In-Reply-To: <50204CDA-B4AD-44C8-AB07-2FE9C2A412C0@mellanox.com> List-Id: DPDK patches and discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces@dpdk.org Sender: "dev" On Wed, 1 Aug 2018 18:03:04 +0000 Yongseok Koh wrote: > > On Jul 31, 2018, at 11:07 AM, Stephen Hemminger wrote: > > > > On Tue, 31 Jul 2018 18:48:40 +0200 > > Adrien Mazarguil wrote: > > > >> On Tue, Jul 31, 2018 at 09:30:54AM -0700, Stephen Hemminger wrote: > >>> Declaring variables as register in C is a leftover from an earlier > >>> era (like cassette tape decks in cars). > >> > >> I don't agree here. It's a hint for compilers and developers that the > >> address of such variables won't be needed (and cannot be taken) to enable > >> whatever optimizations are possible knowing this. > >> > >> Somewhat like inline functions, it's not a forced optimization, just a > >> useful hint that shouldn't hurt if used wisely. > >> > >> Besides, cassette decks are not dead yet :) > > > > If you look at the code, that is not how register is being used (ie. don't take > > address of this). It seems like an attempt at optimization. > > I know compilers are smart enough and the occurrences in mlx4/5 were made from > my old fashioned habit. But, I don't see any urgency to push this patch in RC > stage even though I'm 99% sure that it is harmless. And in general I don't even > understand why we can't live with that if it isn't harmful (or a violation) but > informative. I mean no badness but at least one goodness :-) > > Thanks, > Yongseok > Sure, this is intended for next release not rc stage. Just trying to clean up code base where I see it.