From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754520AbbDTPHm (ORCPT ); Mon, 20 Apr 2015 11:07:42 -0400 Received: from mail.skyhub.de ([78.46.96.112]:43513 "EHLO mail.skyhub.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752730AbbDTPHk (ORCPT ); Mon, 20 Apr 2015 11:07:40 -0400 Date: Mon, 20 Apr 2015 17:07:35 +0200 From: Borislav Petkov To: Rasmus Villemoes Cc: Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , x86@kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] x86_64: use -mskip-rax-setup when available Message-ID: <20150420150735.GA10191@pd.tnic> References: <1429532896-10265-1-git-send-email-linux@rasmusvillemoes.dk> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <1429532896-10265-1-git-send-email-linux@rasmusvillemoes.dk> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Apr 20, 2015 at 02:28:16PM +0200, Rasmus Villemoes wrote: > gcc 5 supports the option -mskip-rax-setup to avoid emitting the > two-byte instruction xor %eax,%eax before a vararg function > call. Clearing %eax is redundant in the kernel, since no callee > expects any floating point arguments, and hence never use the incoming > value of %eax for anything. > > For a defconfig kernel, the .text saving is around 26 kB: > > $ size /tmp/vmlinux.{old,new} > text data bss dec hex filename > 12221850 1735352 1077248 15034450 e56852 /tmp/vmlinux.old > 12195955 1735352 1077248 15008555 e5032b /tmp/vmlinux.new > > Signed-off-by: Rasmus Villemoes > --- > > Nothing seems to have happened on the kernel side since H.J. Lu > implemented this in December. Since gcc 5 is officially released I see the same patch from him from Apr. 16th: https://lkml.kernel.org/r/CAMe9rOrfDo3MGaQc_s5crw3TrYhS8NtqeyRcUFiA0yAV8e9Nig@mail.gmail.com Why are you sending it too? -- Regards/Gruss, Boris. ECO tip #101: Trim your mails when you reply. --