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=-3.5 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED 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 6D25CC433E0 for ; Thu, 18 Mar 2021 17:29:07 +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 02AFC64EF2 for ; Thu, 18 Mar 2021 17:29:06 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 02AFC64EF2 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]:42240 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1lMwSH-0000Us-Vk for qemu-devel@archiver.kernel.org; Thu, 18 Mar 2021 13:29:06 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:46862) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1lMwQ9-0007dy-FY for qemu-devel@nongnu.org; Thu, 18 Mar 2021 13:26:55 -0400 Received: from rev.ng ([5.9.113.41]:41771) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1lMwQ7-0007Yb-BC for qemu-devel@nongnu.org; Thu, 18 Mar 2021 13:26:53 -0400 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=AD70THabnrsdBeu7V+l8C/2H0hqEN6roInJ5rxOiQ38=; b=GqnIYhb/VCInAHrBuAWkvPn57e 2jFUqHV/3g0cO196HK99yq5yhKZLXPw9blQOK20tKHojKZcylNPOhvlu05rYJxwh/ljyYi4t0QsbR yIpsmCPCe0w8m+NYJz6Z6x/ZRW4rMqhzY44JOlCf29MFuTDGlVFcatKb4ROPhSKM/zDE=; Date: Thu, 18 Mar 2021 18:26:36 +0100 To: Taylor Simpson Cc: Richard Henderson , "qemu-devel@nongnu.org" , Brian Cain , "babush@rev.ng" , "nizzo@rev.ng" , "philmd@redhat.com" Subject: Re: [PATCH v2 02/10] target/hexagon: import README for idef-parser Message-ID: <20210318182636.17c75866@orange> In-Reply-To: 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 Wed, 10 Mar 2021 15:48:14 +0000 Taylor Simpson wrote: > Which instructions require this? There must be an attribute that we > could check to see if it is needed before emitting the TCG. The following should be an example of an instruction that requires zero-initialization: /* S2_vsplatrh */ void emit_S2_vsplatrh(DisasContext *ctx, Insn *insn, Packet *pkt, TCGv_i64 RddV, TCGv_i32 RsV) /* for (i=0;i<4;i++) { fSETHALF(i,RddV, fGETHALF(0,RsV)); } } */ { tcg_gen_movi_i64(RddV, 0); for (int i = ((int64_t)0ULL); i < ((int64_t)4ULL); i++) { TCGv_i32 tmp_0 = tcg_temp_new_i32(); tcg_gen_sextract_i32(tmp_0, RsV, ((int64_t)0ULL) * 16, 16); TCGv_i64 tmp_1 = tcg_temp_new_i64(); tcg_gen_ext_i32_i64(tmp_1, tmp_0); tcg_temp_free_i32(tmp_0); tcg_gen_deposit_i64(RddV, RddV, tmp_1, i * 16, 16); tcg_temp_free_i64(tmp_1); } } If we don't zero-initialize RddV, the deposit instruction will read uninitialized data. Note that, IIRC, `RddV` is not always a global variable, which could be safely read, but it might be an uninitialized TCGv that will be written to the CPU state in the commit phase. -- Alessandro Di Federico rev.ng