From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261510AbVEONQe (ORCPT ); Sun, 15 May 2005 09:16:34 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261612AbVEONQe (ORCPT ); Sun, 15 May 2005 09:16:34 -0400 Received: from emailhub.stusta.mhn.de ([141.84.69.5]:19729 "HELO mailout.stusta.mhn.de") by vger.kernel.org with SMTP id S261510AbVEONQb (ORCPT ); Sun, 15 May 2005 09:16:31 -0400 Date: Sun, 15 May 2005 15:16:25 +0200 From: Adrian Bunk To: Andi Kleen Cc: linux-kernel@vger.kernel.org Subject: Re: [-mm patch] i386: enable REGPARM by default Message-ID: <20050515131625.GU16549@stusta.de> References: <20050515115712.GQ16549@stusta.de> <20050515123729.GT16549@stusta.de> <20050515130008.GA72644@muc.de> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20050515130008.GA72644@muc.de> User-Agent: Mutt/1.5.9i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Sun, May 15, 2005 at 03:00:08PM +0200, Andi Kleen wrote: > On Sun, May 15, 2005 at 02:37:31PM +0200, Adrian Bunk wrote: > > On Sun, May 15, 2005 at 02:22:34PM +0200, Andi Kleen wrote: > > > Adrian Bunk writes: > > > > > > > This patch should _not_ go into Linus' tree. > > > > > > > > At some time in the future, we want to unconditionally enable REGPARM on > > > > i386. > > > > > > > > Let's give it a bit broader testing coverage among -mm users. > > > > > > iirc problem is that gcc 2.95 and possibly 3.0.x have some known > > > miscompilations with regparams. That is why it was only used > > > with fastcall for a long time. One 3.1.x+ it should be safe. > > > But you cannot express dependencies on the compiler version > > > in Kconfig right now. > > > > > > Of course getting rid of gcc 2.95 and 3.0.x support would be a good idea, > > > that would allow many other nice things. > > > > If you'd read either arch/i386/Makefile or the help text for > > CONFIG_REGPARM, you'd have noticed that we do never use regparm with > > gcc < 3.0 . > > Yes, this means you cannot have binary compatible kernels compiled > with different compilers. Which might be a bad thing. For that > reason alone I would keep the config. We never guarantee binary compatibility with different compilers. And gcc 2 <-> gcc 3 is an example where it's easy to see that there's no binary compatibility in the kernel. > -Andi cu Adrian -- "Is there not promise of rain?" Ling Tan asked suddenly out of the darkness. There had been need of rain for many days. "Only a promise," Lao Er said. Pearl S. Buck - Dragon Seed