From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from fed1rmmtao04.cox.net (fed1rmmtao04.cox.net [68.230.241.35]) by ozlabs.org (Postfix) with ESMTP id 5EE9667B4E for ; Sat, 7 May 2005 00:53:16 +1000 (EST) Date: Fri, 6 May 2005 07:53:13 -0700 From: Tom Rini To: Segher Boessenkool Message-ID: <20050506145313.GE1221@smtp.west.cox.net> References: <17016.29775.224816.691409@cargo.ozlabs.ibm.com> <466e699745cf24e660e296530f6e34dc@embeddededge.com> <17017.16478.767293.191940@cargo.ozlabs.ibm.com> <45e21c1ae2899849665fb894a2adcc20@embeddededge.com> <17017.39523.745634.193331@cargo.ozlabs.ibm.com> <20050505041225.GX1221@smtp.west.cox.net> <17017.42136.824607.253146@cargo.ozlabs.ibm.com> <20050505044737.GY1221@smtp.west.cox.net> <17017.44421.790813.918463@cargo.ozlabs.ibm.com> <205f4a46b0d9eddd5c46ff1678c9e4ca@kernel.crashing.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <205f4a46b0d9eddd5c46ff1678c9e4ca@kernel.crashing.org> 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 Fri, May 06, 2005 at 04:44:33PM +0200, Segher Boessenkool wrote: > >Well, say you are compiling for 405. You either need to have a gcc > >that was configured with --with-cpu=405, or you need to have hacked > >arch/ppc/Makefile to add -mcpu=405. In both cases the problem doesn't > >arise. It only arises if you have a biarch gcc4 that was configured > >without any --with-cpu=xxx option and is run without any -mcpu=xxx > >option. > > It happens for any installation where the default chosen by the GCC > used is not the -mcpu=XXX flag you need used for your kernel. Which > is a much more general statement than the biarch one. Most people just > get lucky, because they compile code with a compiler that is defaulted > for their target, and userland and kernel use (about) the same options > on most targets. Not so in biarch land (bleeech). Note that up until very recently (and just a bit before conflicting opcodes were added), no -mcpu=XXX was required. For example, I compiled a 44x kernel with a -mcpu=750 toolchain no problems shortly after Paul posted this. The only exception to this rule I can possibly think of is 85xx. But even that would be the "very recently" thing I mentioned as I know you can use an 82xx-set toolchain to build for 85xx. Having said that.. > >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). > > Please always use -mcpu=XXX (and perhaps -mtune=XXX), that's the only > "correct" way to fix this. Or _never_ do any -mcpu=, and let users > override it in the CC setting in the Makefile. But I like the first > option better. We should setup cpu-opt-$(CONFIG_every choice) to fix new gcc breakage (and I guess we shouldn't have removed the do-nothing ones we had a few years ago). -- Tom Rini http://gate.crashing.org/~trini/