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=-2.1 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 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 72DB6C3F2D1 for ; Fri, 28 Feb 2020 03:34:25 +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 4020A24692 for ; Fri, 28 Feb 2020 03:34:25 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=linaro.org header.i=@linaro.org header.b="RBSq1GfR" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 4020A24692 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linaro.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:41132 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1j7WPw-00041t-8u for qemu-devel@archiver.kernel.org; Thu, 27 Feb 2020 22:34:24 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:36770) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1j7WPL-0003bB-4j for qemu-devel@nongnu.org; Thu, 27 Feb 2020 22:33:48 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1j7WPJ-0006vq-UO for qemu-devel@nongnu.org; Thu, 27 Feb 2020 22:33:46 -0500 Received: from mail-pl1-x643.google.com ([2607:f8b0:4864:20::643]:39349) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_128_CBC_SHA1:16) (Exim 4.71) (envelope-from ) id 1j7WPJ-0006vf-Na for qemu-devel@nongnu.org; Thu, 27 Feb 2020 22:33:45 -0500 Received: by mail-pl1-x643.google.com with SMTP id g6so670871plp.6 for ; Thu, 27 Feb 2020 19:33:45 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; h=subject:to:cc:references:from:message-id:date:user-agent :mime-version:in-reply-to:content-language:content-transfer-encoding; bh=f1HUTfjWI/l8GIJRRF8yHhG7QeUn+lrCOnpteX95pLM=; b=RBSq1GfRIRYFjHSaxXmwbNoRSaYnW936lY57A8kboKcwYNRtNQmQlh878l2gxT/GGp LCXxZ4VlY8yWyyVyqq564hAs2b3pHd133KjJ7rNAskFe3W3d+O7f5RbbHCHf55pSJRP8 AGAQ/2ZWoISimiQ3KN9WIutydHQSEaJTyjq4ZUzD+f+GRtIGY7RH5re0RGbFWwvxgXbb 27g4S845JR5Wo0rJUZ+CClDNrkc/+bSW+uTv0SIzb4QLzHmNh1Nv13O0FeHSRnjm5tzW TZpEWn1gxGLxlPwUwieRxF7m/Xlq3W72oGMmQ6VcvTp0/RdbEyL10gWDQXSReUwlOgDD r/MQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=f1HUTfjWI/l8GIJRRF8yHhG7QeUn+lrCOnpteX95pLM=; b=pdrMGxLU6gBqo8hVuqzHko6FBwMX25PUjHB4CVFpx46tfOxuqHHryunF+UhvleOikv sx5k4sCa7sw3rUVCKjGxIOFKYRfD7Fg4Jatk5KbyFMY+wyuWZsqKmm4+4krhIiQqTr9x aXTIyw2UMBHCSowQ1s0ZP0uyFqS+EMeQxuwIha1uBW6OrvqT8uQjOpLjezjKFts7REzy D0xtnJJzmiJT/cZWf/BBgfRUDHwt/3xDQlqOuox94hQClfxSMN16YoODHuyJcsi7aI4c GA6LpchGlp/PMProKNH26Xbden56saVMKmdEG4D2borA6ysuNibqfw11umfddc9ki4pe UOoA== X-Gm-Message-State: APjAAAWa3eMyhtk3cy35ytevgz5xhScN34wsPc1A7bfeRmGhgoF8tSSN acgc9UZ6pCfnTXYox5w5K5U3uQ== X-Google-Smtp-Source: APXvYqyNg8c+b1nge2zl3AKwa/fmuWS0TQBCd9OHpVeiNDE2hCZTjRsXzNRQJTYSiQSeQrCufG7O6Q== X-Received: by 2002:a17:90a:2107:: with SMTP id a7mr944778pje.37.1582860824073; Thu, 27 Feb 2020 19:33:44 -0800 (PST) Received: from [192.168.1.11] (97-126-123-70.tukw.qwest.net. [97.126.123.70]) by smtp.gmail.com with ESMTPSA id c68sm9188740pfc.156.2020.02.27.19.33.42 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 27 Feb 2020 19:33:43 -0800 (PST) Subject: Re: [PATCH v4 1/5] target/riscv: add vector unit stride load and store instructions To: LIU Zhiwei , alistair23@gmail.com, chihmin.chao@sifive.com, palmer@dabbelt.com References: <20200225103508.7651-1-zhiwei_liu@c-sky.com> <20200225103508.7651-2-zhiwei_liu@c-sky.com> <4cfb56d6-34a5-0e35-87a0-2aefaafa4221@linaro.org> <287bde05-421c-f49c-2404-fdee183c9e12@c-sky.com> From: Richard Henderson Message-ID: <10e50ea8-7614-f094-a827-38ed09462f29@linaro.org> Date: Thu, 27 Feb 2020 19:33:41 -0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.4.1 MIME-Version: 1.0 In-Reply-To: <287bde05-421c-f49c-2404-fdee183c9e12@c-sky.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit X-detected-operating-system: by eggs.gnu.org: Genre and OS details not recognized. X-Received-From: 2607:f8b0:4864:20::643 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: , Cc: wenmeng_zhang@c-sky.com, qemu-riscv@nongnu.org, linux-csky@vger.kernel.org, wxy194768@alibaba-inc.com, qemu-devel@nongnu.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 2/27/20 5:50 PM, LIU Zhiwei wrote: >> This is not what I had in mind, and looks wrong as well. >> >> int idx = (index * mlen) / 64; >> int pos = (index * mlen) % 64; >> return (((uint64_t *)v0)[idx] >> pos) & 1; >> >> You also might consider passing log2(mlen), so the multiplication could be >> strength-reduced to a shift. > I don't think so. For example, when mlen is 8 bits and index is 0, it will > reduce to > > return (((uint64_t *)v0)[0]) & 1 > > And it's not right. > > The right bit is first bit in vector register 0. And in host big endianess, > it will be  the first bit of the seventh byte. You've forgotten that we've just done an 8-byte big-endian load, which means that we *are* looking at the first bit of the byte at offset 7. It is right. >> You don't need to pass mlen, since it's > Yes. I finally remembered all of the bits that go into mlen and thought I had deleted that sentence -- apparently I only removed half. ;-) r~