From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:45044) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1aRjUA-0006Lu-H7 for qemu-devel@nongnu.org; Fri, 05 Feb 2016 11:43:56 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1aRjU7-0004XT-8A for qemu-devel@nongnu.org; Fri, 05 Feb 2016 11:43:54 -0500 Received: from mail-wm0-x235.google.com ([2a00:1450:400c:c09::235]:32918) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1aRjU7-0004XC-1S for qemu-devel@nongnu.org; Fri, 05 Feb 2016 11:43:51 -0500 Received: by mail-wm0-x235.google.com with SMTP id g62so55793697wme.0 for ; Fri, 05 Feb 2016 08:43:50 -0800 (PST) References: <1454506721-11843-1-git-send-email-peter.maydell@linaro.org> <1454506721-11843-6-git-send-email-peter.maydell@linaro.org> <87io23nsqe.fsf@linaro.org> <87egcrnnbe.fsf@linaro.org> From: Alex =?utf-8?Q?Benn=C3=A9e?= In-reply-to: Date: Fri, 05 Feb 2016 16:43:42 +0000 Message-ID: <878u2znm4h.fsf@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Subject: Re: [Qemu-devel] [PATCH 5/7] target-arm: Add isread parameter to CPAccessFns List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Peter Maydell Cc: "Edgar E. Iglesias" , qemu-arm , QEMU Developers , Patch Tracking Peter Maydell writes: > On 5 February 2016 at 16:17, Alex Bennée wrote: >> >> Peter Maydell writes: >>> I haven't measured, no, but since there are only 3 arguments the >>> third argument is going to be in a register on any host architecture >>> we care about, which means the overhead is just going to be a single >>> "load constant 0 or 1 into register before the call". I think that's >>> going to be lost in the noise compared to actually having to make >>> the function call at all, the work the function call does, and then >>> the second function call later to do the read or write. >> >> I was thinking of knock on effects on spilling other registers in the >> TCG code. I guess this depends on how complex the code is around system >> register access. > > The register in question is going to be caller-saves anyway, so no > effect on spilling in the TCG code I think. Well my only remaining objection is the additional line-wrapping looks ugly which I don't think is a valid objection ;-) Reviewed-by: Alex Bennée > > thanks > -- PMM -- Alex Bennée