From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753645AbbDPVZ7 (ORCPT ); Thu, 16 Apr 2015 17:25:59 -0400 Received: from one.firstfloor.org ([193.170.194.197]:33570 "EHLO one.firstfloor.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751603AbbDPVZw (ORCPT ); Thu, 16 Apr 2015 17:25:52 -0400 Date: Thu, 16 Apr 2015 23:25:51 +0200 From: Andi Kleen To: "H.J. Lu" Cc: LKML , "H. Peter Anvin" , Andi Kleen Subject: Re: [PATCH] Use -mskip-rax-setup if supported Message-ID: <20150416212551.GY2366@two.firstfloor.org> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Apr 16, 2015 at 02:23:44PM -0700, H.J. Lu wrote: > GCC 5 added a compiler option, -mskip-rax-setup, for x86-64. It skips > setting up the RAX register when SSE is disabled and there are no > variable arguments passed in vector registers. Since kernel doesn't > pass vector registers to functions with variable arguments, this option > can be used to optimize the x86-64 kernel. For kernel 3.17: > > text data bss dec hex filename > 11455921 2204048 5853184 19513153 129bf41 vmlinux #with -mskip-rax-setup > 11480079 2204048 5853184 19537311 12a1d9f vmlinux Patch looks good to me. Reviewed-by: Andi Kleen -Andi