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=-3.9 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED autolearn=ham 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 819CBC04AB3 for ; Thu, 9 May 2019 18:29:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 61C08217F4 for ; Thu, 9 May 2019 18:29:07 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726715AbfEIS3G (ORCPT ); Thu, 9 May 2019 14:29:06 -0400 Received: from mail.kernel.org ([198.145.29.99]:58924 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726620AbfEIS3G (ORCPT ); Thu, 9 May 2019 14:29:06 -0400 Received: from gandalf.local.home (cpe-66-24-58-225.stny.res.rr.com [66.24.58.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id B94DE217D9; Thu, 9 May 2019 18:29:03 +0000 (UTC) Date: Thu, 9 May 2019 14:29:02 -0400 From: Steven Rostedt To: Linus Torvalds Cc: David Laight , Peter Zijlstra , "tglx@linutronix.de" , "hpa@zytor.com" , "julien.thierry@arm.com" , "will.deacon@arm.com" , "luto@amacapital.net" , "mingo@kernel.org" , "catalin.marinas@arm.com" , "james.morse@arm.com" , "valentin.schneider@arm.com" , "brgerst@gmail.com" , "jpoimboe@redhat.com" , "luto@kernel.org" , "bp@alien8.de" , "dvlasenk@redhat.com" , "linux-kernel@vger.kernel.org" , "dvyukov@google.com" Subject: Re: [PATCH 02/25] tracing: Improve "if" macro code generation Message-ID: <20190509142902.08a32f20@gandalf.local.home> In-Reply-To: References: <20190318153840.906404905@infradead.org> <20190318155140.058627431@infradead.org> <20190509090058.6554dc81@gandalf.local.home> X-Mailer: Claws Mail 3.17.3 (GTK+ 2.24.32; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 9 May 2019 09:51:59 -0700 Linus Torvalds wrote: > On Thu, May 9, 2019 at 6:01 AM Steven Rostedt wrote: > > > > This patch works. Can I get your Signed-off-by for it? > > Yes. Please write some kind of comprehensible commit log for it, but How's this: "Peter Zijlstra noticed that with CONFIG_PROFILE_ALL_BRANCHES, the "if" macro converts the conditional to an array index. This can cause GCC to create horrible code. When there are nested ifs, the generated code uses register values to encode branching decisions. Josh Poimboeuf found that replacing the define "if" macro from using the condition as an array index and incrementing the branch statics with an if statement itself, reduced the asm complexity and shrinks the generated code quite a bit. But this can be simplified even further by replacing the internal if statement with a ternary operator. Reported-by: Peter Zijlstra (Intel) Reported-by: Josh Poimboeuf " > > Signed-off-by: Linus Torvalds Thanks, -- Steve > > for the patch itself. >