Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754150AbbG0PuP (ORCPT ); Mon, 27 Jul 2015 11:50:15 -0400 Received: from mail-ob0-f173.google.com ([209.85.214.173]:33861 "EHLO mail-ob0-f173.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750803AbbG0PuN (ORCPT ); Mon, 27 Jul 2015 11:50:13 -0400 MIME-Version: 1.0 In-Reply-To: <20150727154035.GA18213@gmail.com> References: <1437869262-3211-1-git-send-email-uros_bizjak1@t-2.net> <20150727154035.GA18213@gmail.com> Date: Mon, 27 Jul 2015 17:50:12 +0200 Message-ID: Subject: Re: [PATCH] x86: Introduce ASM flags to bitops From: Uros Bizjak To: Ingo Molnar Cc: Uros Bizjak , linux-kernel@vger.kernel.org, "x86@kernel.org" Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2178 Lines: 58 On Mon, Jul 27, 2015 at 5:40 PM, Ingo Molnar wrote: > > * Uros Bizjak wrote: > >> From: Uros Bizjak >> >> This patch introduces GCC ASM flags to bitops. Instead of e.g. >> >> 136d7: 48 0f a3 3d 00 00 00 bt %rdi,0x0(%rip) >> 136de: 00 >> 136df: 19 ff sbb %edi,%edi >> 136e1: 85 ff test %edi,%edi >> 136e3: 0f 95 c0 setne %al >> >> following code is generated: >> >> 13767: 48 0f a3 3d 00 00 00 bt %rdi,0x0(%rip) >> 1376e: 00 >> 1376f: 0f 92 c0 setb %al >> >> Similar improvement can be seen in following code: >> >> 7a6c: 48 0f a3 11 bt %rdx,(%rcx) >> 7a70: 19 d2 sbb %edx,%edx >> 7a72: 85 d2 test %edx,%edx >> 7a74: 74 eb je 7a61 >> >> which becomes: >> >> 7a8c: 48 0f a3 11 bt %rdx,(%rcx) >> 7a90: 73 ef jae 7a81 >> >> Signed-off-by: Uros Bizjak >> --- >> arch/x86/include/asm/bitops.h | 26 ++++++++++++++++++++++++-- >> arch/x86/include/asm/percpu.h | 18 +++++++++++++++++- >> arch/x86/include/asm/signal.h | 6 ++++++ >> arch/x86/include/asm/sync_bitops.h | 18 ++++++++++++++++++ >> 4 files changed, 65 insertions(+), 3 deletions(-) > > Nothing in your patch seems to be setting __GCC_ASM_FLAG_OUTPUTS__, and the patch > does not seem to be mailed as part of a larger series ... > > So how is this supposed to work? GCC version 6+ will automatically define __GCC_ASM_FLAG_OUTPUTS__ when this feature is supported. Please see [1] for RFC GCC patch series and [2] for final committed patch. [1] https://gcc.gnu.org/ml/gcc-patches/2015-05/msg00594.html [2] https://gcc.gnu.org/ml/gcc-patches/2015-06/msg02087.html Uros. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/