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=-3.6 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,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 92C2AC433DB for ; Mon, 1 Mar 2021 14:54:22 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id C62DB64E42 for ; Mon, 1 Mar 2021 14:54:21 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org C62DB64E42 Authentication-Results: mail.kernel.org; dmarc=pass (p=none dis=none) header.from=nongnu.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:34004 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1lGjwC-0007sB-QY for qemu-devel@archiver.kernel.org; Mon, 01 Mar 2021 09:54:20 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:49566) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1lGjsj-0003oE-2V for qemu-devel@nongnu.org; Mon, 01 Mar 2021 09:50:45 -0500 Received: from rev.ng ([5.9.113.41]:50869) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1lGjsh-0000MA-BP for qemu-devel@nongnu.org; Mon, 01 Mar 2021 09:50:44 -0500 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=rev.ng; s=dkim; h=Content-Transfer-Encoding:Content-Type:MIME-Version:References: In-Reply-To:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To:Content-ID: Content-Description:Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc :Resent-Message-ID:List-Id:List-Help:List-Unsubscribe:List-Subscribe: List-Post:List-Owner:List-Archive; bh=Ps1w5mzplZ1XtZef/+95wENGOnzXhAyftWEPpbAmo5o=; b=ONwgBO3sV5iW0nIA8gT+Welslr dQA3tv3q3kcwBwsYcPxdiQalFu0Elo2s9n3KHAfCQjv2zoCjlZ/sj5vV7ysG5zXK6zpRw5Siu19OV Uc5vGo75xBnV9WpX256HdGtNHtaH2OpKhcKAMPS0HSKMo5Wa16HiAOquWEh25r5GekAk=; Date: Mon, 1 Mar 2021 15:50:35 +0100 To: Richard Henderson Cc: Alessandro Di Federico , qemu-devel@nongnu.org, tsimpson@quicinc.com, bcain@quicinc.com, babush@rev.ng, nizzo@rev.ng, philmd@redhat.com Subject: Re: [PATCH v2 02/10] target/hexagon: import README for idef-parser Message-ID: <20210301155035.2a7360e8@orange> In-Reply-To: <3b3c6088-0ff2-beeb-e9fe-29c2dec012ca@linaro.org> References: <20210225151856.3284701-1-ale.qemu@rev.ng> <20210225151856.3284701-3-ale.qemu@rev.ng> <3b3c6088-0ff2-beeb-e9fe-29c2dec012ca@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=5.9.113.41; envelope-from=ale@rev.ng; helo=rev.ng X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Reply-to: Alessandro Di Federico From: Alessandro Di Federico via On Thu, 25 Feb 2021 12:20:53 -0800 Richard Henderson wrote: > This is odd, as is the description of why. Yes, if RdV is read > without initialization, TCG middle-end will abort (at least with > --enable-debug-tcg enabling the assertions). But you've just said > that "no reading" was found. When we say that no reading was found, we mean that it was not initialized by the caller. The term "reading" is a leftover from how the parser input was organized in the first iterations of the base patchset. I'll rephrase that. > So why did you perform this dummy initialization, which will be > eliminated later? The initialization is redundant in this specific example, but, in general, non-initialized values are assumed to be zero-initialized. For instance when you're writing a 64-bit integer piecewise, by OR-ing two 32-bit integers, it matters. In short: useless in this case (but DCE'd by the mid-end), important in general. > So, I take it from this that you're emitting tcg directly from within > the parser, and not generating any kind of abstract syntax tree? Yes. There a few spots where an AST would have been beneficial, but overall we deem it would increase the complexity of the parser with limited return. -- Alessandro Di Federico rev.ng