From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-3.5 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE, SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 480C1C2BB85 for ; Thu, 16 Apr 2020 11:54:56 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 290A921D91 for ; Thu, 16 Apr 2020 11:54:56 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="b3eUhw5B" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2634209AbgDPLyE (ORCPT ); Thu, 16 Apr 2020 07:54:04 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40842 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2506634AbgDPLwd (ORCPT ); Thu, 16 Apr 2020 07:52:33 -0400 Received: from bombadil.infradead.org (bombadil.infradead.org [IPv6:2607:7c80:54:e::133]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 95DDAC061A0F for ; Thu, 16 Apr 2020 04:52:33 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=Content-Type:MIME-Version:References: Subject:Cc:To:From:Date:Message-Id:Sender:Reply-To:Content-Transfer-Encoding: Content-ID:Content-Description:In-Reply-To; bh=0tB8fwAECH9DTdmotSb06Thr66Emzkcwh377O0NwzJ4=; b=b3eUhw5BTRjg92BI6M0gYt1zTx PRvWk7ZQ187dalXP040GwQh0EZi53VzRbjRK15igKl9jNrv3SpBQFrmT4bl6Wu5E9P7fSVlYHBUET qJga+g/+ZaO4wZGOxtB3Vt1LFY7xfkzRaD6yDBLriM6EWwH3Ne4V57xmWFN4MIT/chCHj2FmBnu+G ZD85Hqx3dxGTu3BrNDkWkLa421FLWnNaVtC8UdZi+F3cQu3obDlyZZ9tpcFj92R9pYdkU1KCTI4G3 sftACTIyBg3nk1NXsiO85bLmoHp820KJaMFxPCHxOEjv/Wyvfml+j107nJOodLEPGRJDYVEh63hMC Uoed8LJg==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by bombadil.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1jP34D-0004s1-W9; Thu, 16 Apr 2020 11:52:26 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id 58FEE3073F0; Thu, 16 Apr 2020 13:52:24 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 0) id 318C82B0DE4C5; Thu, 16 Apr 2020 13:52:24 +0200 (CEST) Message-Id: <20200416115118.867411350@infradead.org> User-Agent: quilt/0.65 Date: Thu, 16 Apr 2020 13:47:12 +0200 From: Peter Zijlstra To: tglx@linutronix.de, jpoimboe@redhat.com Cc: linux-kernel@vger.kernel.org, x86@kernel.org, peterz@infradead.org, mhiramat@kernel.org, mbenes@suse.cz, jthierry@redhat.com, alexandre.chartre@oracle.com Subject: [PATCH v5 06/17] x86,ftrace: Shrink ftrace_regs_caller() by one byte References: <20200416114706.625340212@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 'Optimize' ftrace_regs_caller. Instead of comparing against an immediate, the more natural way to test for zero on x86 is: 'test %r,%r'. 48 83 f8 00 cmp $0x0,%rax 74 49 je 226 48 85 c0 test %rax,%rax 74 49 je 225 Signed-off-by: Peter Zijlstra (Intel) --- arch/x86/kernel/ftrace_64.S | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) --- a/arch/x86/kernel/ftrace_64.S +++ b/arch/x86/kernel/ftrace_64.S @@ -240,8 +240,8 @@ SYM_INNER_LABEL(ftrace_regs_call, SYM_L_ * See arch_ftrace_set_direct_caller(). */ movq ORIG_RAX(%rsp), %rax - cmpq $0, %rax - je 1f + testq %rax, %rax + jz 1f /* Swap the flags with orig_rax */ movq MCOUNT_REG_SIZE(%rsp), %rdi