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=-6.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED,USER_AGENT_NEOMUTT 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 85C48C43381 for ; Mon, 18 Mar 2019 23:37:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4D9A8213F2 for ; Mon, 18 Mar 2019 23:37:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727000AbfCRXhb (ORCPT ); Mon, 18 Mar 2019 19:37:31 -0400 Received: from mx1.redhat.com ([209.132.183.28]:35298 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726743AbfCRXha (ORCPT ); Mon, 18 Mar 2019 19:37:30 -0400 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 275D436809; Mon, 18 Mar 2019 23:37:30 +0000 (UTC) Received: from treble (ovpn-120-200.rdu2.redhat.com [10.10.120.200]) by smtp.corp.redhat.com (Postfix) with ESMTPS id D18D35D704; Mon, 18 Mar 2019 23:37:27 +0000 (UTC) Date: Mon, 18 Mar 2019 18:37:20 -0500 From: Josh Poimboeuf To: Peter Zijlstra Cc: torvalds@linux-foundation.org, 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, luto@kernel.org, bp@alien8.de, dvlasenk@redhat.com, linux-kernel@vger.kernel.org, dvyukov@google.com, rostedt@goodmis.org Subject: Re: [PATCH 02/25] tracing: Improve "if" macro code generation Message-ID: <20190318233720.76j6ywkdulmnhu2o@treble> References: <20190318153840.906404905@infradead.org> <20190318155140.058627431@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20190318155140.058627431@infradead.org> User-Agent: NeoMutt/20180716 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.30]); Mon, 18 Mar 2019 23:37:30 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Mar 18, 2019 at 04:38:42PM +0100, Peter Zijlstra wrote: > 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. > > Make it easier for GCC to optimize by keeping the conditional as a > conditional rather than converting it to an integer. This shrinks the > generated code quite a bit, and also makes the code sane enough for > objtool to understand. > > Cc: rostedt@goodmis.org > Cc: valentin.schneider@arm.com > Cc: luto@amacapital.net > Cc: brgerst@gmail.com > Cc: catalin.marinas@arm.com > Cc: mingo@kernel.org > Cc: dvlasenk@redhat.com > Cc: will.deacon@arm.com > Cc: julien.thierry@arm.com > Cc: torvalds@linux-foundation.org > Cc: dvyukov@google.com > Cc: bp@alien8.de > Cc: tglx@linutronix.de > Cc: james.morse@arm.com > Cc: luto@kernel.org > Cc: hpa@zytor.com > Reported-by: Peter Zijlstra > Signed-off-by: Josh Poimboeuf > Signed-off-by: Peter Zijlstra (Intel) > Link: https://lkml.kernel.org/r/20190307174802.46fmpysxyo35hh43@treble Missing "From" me. -- Josh