From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from va3outboundpool.messaging.microsoft.com (va3ehsobe002.messaging.microsoft.com [216.32.180.12]) (using TLSv1 with cipher AES128-SHA (128/128 bits)) (Client CN "mail.global.frontbridge.com", Issuer "Microsoft Secure Server Authority" (not verified)) by ozlabs.org (Postfix) with ESMTPS id 4F0A7B6FB4 for ; Fri, 8 Jun 2012 03:51:17 +1000 (EST) Message-ID: <4FD0EA08.7040903@freescale.com> Date: Thu, 7 Jun 2012 12:51:04 -0500 From: Scott Wood MIME-Version: 1.0 To: Paul Mackerras Subject: Re: [PATCH] powerpc: Optimise the 64bit optimised __clear_user References: <20120604175858.38dac554@kryten> <20120605120222.6722a3e3@kryten> <178E3BC0-C6E2-4E33-BA66-8144F192A151@kernel.crashing.org> <20120607030423.GA30053@drongo> In-Reply-To: <20120607030423.GA30053@drongo> Content-Type: text/plain; charset="ISO-8859-1" Cc: mikey@neuling.org, michael@ellerman.id.au, Anton Blanchard , olof@lixom.net, linuxppc-dev@lists.ozlabs.org List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On 06/06/2012 10:04 PM, Paul Mackerras wrote: > On Wed, Jun 06, 2012 at 06:40:54PM +0200, Segher Boessenkool wrote: >>> +err1; dcbz r0,r3 >> >> There is no such instruction, you probably meant "dcbz 0,r3"? > > There certainly is such an instruction, though it doesn't do exactly > what a naive reader might expect. Using 0 rather than r0 or %r0 > improves readability but makes no difference to the assembler or the > cpu. The assembler can't tell that you used r0 rather than 0, because that's handled by the preprocessor, but it seems like a bug (or at least lax error checking) that it accepts %r0 there, and that objdump decodes it as "dcbz r0,r3" rather than "dcbz 0,r3". It's also odd that objdump produces output containing "r3" (not %r3) when the assembler won't directly accept it. -Scott