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=-2.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,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 931C8C5519F for ; Sun, 22 Nov 2020 20:38:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4DBBD206FB for ; Sun, 22 Nov 2020 20:38:25 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="mj8K40sn" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727412AbgKVUiE (ORCPT ); Sun, 22 Nov 2020 15:38:04 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51006 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727297AbgKVUiD (ORCPT ); Sun, 22 Nov 2020 15:38:03 -0500 Received: from mail-wr1-x442.google.com (mail-wr1-x442.google.com [IPv6:2a00:1450:4864:20::442]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 34F1AC0613CF for ; Sun, 22 Nov 2020 12:38:03 -0800 (PST) Received: by mail-wr1-x442.google.com with SMTP id s8so16567625wrw.10 for ; Sun, 22 Nov 2020 12:38:03 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=A7MqUesU7U7SG4sAQdh4tWTV10X2Cxck9huKZPvaxzk=; b=mj8K40snDzVLf45RL3MNCAkNNZTT3fAZAlMHzkQ6zci6CpuJMYAb9qkX0YmyDoQJiy gkN+J7XhJsu0aFKgyCkk035tpCmfHRyPWv/gp3eGHr+Ebwg71HhNXJmONyaT1joVHpSf uTqNXc5AsHQS6tAnrjuRqQ57AVXYgxJNbN4mGVW+rnjh/fbNhX7nktYurJEZbk2qVULv 2BAUuux0UtkBLd1oYNFv+SloAa6uBQAo/xvRrCQwUChgoZV/lwRkPo/zpL2EXUukO1eq Y22HjruQWacHzY0JGRJeN7V7EJesf2rtsVolC3sB+CBUxK4SZOeFT3G64xZtUBOOv6fo 90Wg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=A7MqUesU7U7SG4sAQdh4tWTV10X2Cxck9huKZPvaxzk=; b=SoATS/5XTYBqCstWlu9jyybNr+Uht/QcJfdj2ixky1Z7NrEY0VwksbsOYdBiesxkP3 JzurV4tLqVTUVarkZF75SQgjzAksMo4Ukhp4oKKySMkvLCDUvnN/BU7x5rFHMZPXtlfF b2vyubxe7XOAFdRfUAK/gF4vuKtAeM0XH2oZLL9rhdDWVEHNh63PEW9lIucHgcPHci72 gsywlKxcmazZ9Qtw7Gtt338ruq3N//zk7RmjbcfozTSm7ptMh5eZsPVylEER0SULrG/l 3KqtZYe4OxCuS4X+9bArqUu/+GworJO9Xoa25F0LIaFJqZAc5rhHs7BAAbZV1CQYyi7V 1gww== X-Gm-Message-State: AOAM531bkUnAUcRWTGCtqhH0ho6hDYIwhwsqQeEk26G61pXl3/r2MbOo bQkH9aMPaYZAJXvkG95mej1alBrNeiU= X-Google-Smtp-Source: ABdhPJy4vei2lgTu5DlEB5F0W/cMOUVe4TjDs5Ms09urYVT67/CdXTsx1hBEMIbj5ZDiwMbQhC/MOg== X-Received: by 2002:adf:8028:: with SMTP id 37mr27074340wrk.111.1606077481860; Sun, 22 Nov 2020 12:38:01 -0800 (PST) Received: from ltop.local ([2a02:a03f:b7fe:f700:b0d0:6cd2:d2ec:fc3c]) by smtp.gmail.com with ESMTPSA id p9sm3551930wrw.29.2020.11.22.12.38.00 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 22 Nov 2020 12:38:01 -0800 (PST) Date: Sun, 22 Nov 2020 21:38:00 +0100 From: Luc Van Oostenryck To: Linus Torvalds Cc: Sparse Mailing-list Subject: Re: [PATCH 1/7] not: add testcases for canonicalization & simplification of negations Message-ID: <20201122203800.y262kn5hk3puvcbh@ltop.local> References: <20201122152731.10994-1-luc.vanoostenryck@gmail.com> <20201122152731.10994-2-luc.vanoostenryck@gmail.com> <20201122195746.uq44lstsy2pissxi@ltop.local> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-sparse@vger.kernel.org On Sun, Nov 22, 2020 at 12:13:46PM -0800, Linus Torvalds wrote: > > Honestly, particularly in the conditional form, the OP_SEL > optimization might not even be the right thing. It adds register > pressure. > > So maybe a better model would be to not try to do jump-conversion, but > have some kind of general "can we simplify phi nodes", where jump > conversion to OP_SEL is just one of the options. Yes, for the "context imbalance" problem, it's best to eliminate the most possible conditional branches (and if-conversion and jump threading help each other at this (when not blocking each other)). So, yes, probably what's missing the most is some strategy to attack the problem. -- Luc