From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-in-01.arcor-online.net (mail-in-01.arcor-online.net [151.189.21.41]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client CN "mx.arcor.de", Issuer "Thawte Premium Server CA" (verified OK)) by ozlabs.org (Postfix) with ESMTP id 3CBDCDDECA for ; Mon, 18 Jun 2007 03:46:25 +1000 (EST) In-Reply-To: <200706171920.10898.arnd@arndb.de> References: <20070616000511.712667424@arndb.de> <20070616000618.314570319@arndb.de> <91EBCC0C-48B7-4748-A936-E74CEB7685E0@kernel.crashing.org> <200706171920.10898.arnd@arndb.de> Mime-Version: 1.0 (Apple Message framework v623) Content-Type: text/plain; charset=US-ASCII; format=flowed Message-Id: From: Segher Boessenkool Subject: Re: [patch 2/9] autoselect optimal -mcpu= flag by platform Date: Sun, 17 Jun 2007 19:46:14 +0200 To: Arnd Bergmann Cc: linuxppc-dev@ozlabs.org, paulus@samba.org List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , >> Is there a reason we don't distinguish between 7400/7410 and 74{4,5} >> x? Is it because we dont have any discrete systems with just a 7400 >> on it? > > No, I just didn't know that there was a difference. I had looked at the > gcc source and found that gcc produces the same instruction for both, > but I didn't bother to look at the optimizations. From all I can > tell, -mcpu=7400 is identical to -mcpu=7450 -mtune=750. 7400 is pretty much like a 750 + AltiVec and a few deeper queues. The "FP full" stall is also gone IIRC, or maybe that was not before the 7450. Nothing that GCC knows how to model, anyway. >> Also I'd suggest we have the config options be a 1:1 matching for the >> -mcpu/-mtune options in gcc for the following cases: >> >>> + default "-mcpu=750" if CPU_7xx >>> + default "-mcpu=7450" if CPU_74xx >>> + default "-mcpu=860" if PPC_8xx >>> + default "-mcpu=8540" if PPC_85xx >> >> So if in the future we have code scheduling for 8599 or some other >> variant we don't have to go change the Kconfig just add to it. > > I'm not sure I understand what you would like to see this, would you > like them to be simply renamed to CPU_750/CPU_7450/CPU_860/CPU_8540 > or rather add more options for 740/801/821/823/8548, which are > treated as aliases of the others? GCC treats many of those as aliases, too. Segher