From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from az33egw02.freescale.net (az33egw02.freescale.net [192.88.158.103]) by ozlabs.org (Postfix) with ESMTP id 6484E679EA for ; Fri, 6 May 2005 02:22:42 +1000 (EST) In-Reply-To: <20050505152709.GA1221@smtp.west.cox.net> References: <20050505152709.GA1221@smtp.west.cox.net> Mime-Version: 1.0 (Apple Message framework v619.2) Content-Type: text/plain; charset=US-ASCII; format=flowed Message-Id: From: Kumar Gala Date: Thu, 5 May 2005 11:22:38 -0500 To: "Tom Rini" Cc: linuxppc-dev@ozlabs.org Subject: Re: [PATCH] Set cpu explicitly in kernel compiles List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On May 5, 2005, at 10:27 AM, Tom Rini wrote: > On Thu, May 05, 2005 at 10:12:42AM -0500, Kumar Gala wrote: > > > > On May 5, 2005, at 9:23 AM, Tom Rini wrote: > > > > >On Thu, May 05, 2005 at 09:00:50AM -0500, Kumar Gala wrote: > > > > > > >> On May 5, 2005, at 7:24 AM, Dan Malek wrote: > > > > > > >> > > > > > > > > > > >On May 5, 2005, at 1:22 AM, Paul Mackerras wrote: > > > > > > If you think we should have -mcpu=xxx on the command line > for > > >4xx, > > > > > > 44x, 8xx, etc., then that's fine, but that is a separate > problem > > >> >from > > > > > > what my patch was addressing (one which my patch might make > it > > >> >easier > > > > > > to fix, though). > > > > > > > > > >I think that is exactly what we want, although I don't know how > > >that is > > > > > separate from the patch you sent.? My original comment was the > > >patch > > > > > fixes the problem for only one of the cpu cores, not all of > them.? > > >> >Which > > > > > then led into the subsequent suggestion of making the biarch > work > > > > > like the past compilers, and we must specific the flags for > POWER4 > > > > > instead of the other way around.? Without explicit -mcpu > flags, > > >the > > > > > existing compiler behavior is just fine .....? but, I guess > I'd be > > > > >standing > > > > > in the way of progress to want this :-) > > > > > > >> I agree with Dan here.? I think we should go ahead and extend the > > >patch > > >> to set -mcpu and -mtune flags for the list of processors we have > in > > >> "Processor Type".? If I'm building a kernel for e500 or 4xx I > might > > >as > > >> well get a kernel that is tuned a bit more for the subarch.? > > > > > > This is fine. > > > > > >> Additionally, there should be some expert override ability, so > if I > > >> really want to do -mcpu=7455 -mtune=7455 I can. > > > > > >Gack, no!? It's quite a pain to go from CONFIG_FOO="string" into > > >useable > > > Makefile bits that the one we did have back in 2.4 is gone.? That > also > > > implies gcc finally knows something about these cores that might > be > > > useful, which I don't think is the case, nor is it likely to be.? > But > > >if > > > we did want it, we'd probably go the route x86 has. > > > > I'm not saying it has to be done via a CONFIG option, all I'm saying > is > > if I want to explicitly use GCC then I would hope we could somehow > > disable it being override. > > If you're not doing it via CONFIG, that leaves manual (which is always > an option) or seeing if passing CFLAGS on the cmdline overrides > things, > or adds to them. Thats all I really want. Just for us to make sure if I want to do -mcpu=7455 -mtune=7455 I'm able to and it actually does what I told it to do. I'm not sure if GCC is consistent on how it handles args that are duplicated. For example what will happen with the following: gcc -mcpu=750 -mtune=7450 -mcpu=603 -mtune=603 Is this -mcpu=750 -mtune=7450 or -mcpu=603 -mtune=603 - kumar