From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf1-x42a.google.com (mail-pf1-x42a.google.com [IPv6:2607:f8b0:4864:20::42a]) by sourceware.org (Postfix) with ESMTPS id 78B093858409 for ; Tue, 28 Nov 2023 22:14:22 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.2 sourceware.org 78B093858409 Authentication-Results: sourceware.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: sourceware.org; spf=pass smtp.mailfrom=gmail.com ARC-Filter: OpenARC Filter v1.0.0 sourceware.org 78B093858409 Authentication-Results: server2.sourceware.org; arc=none smtp.remote-ip=2607:f8b0:4864:20::42a ARC-Seal: i=1; a=rsa-sha256; d=sourceware.org; s=key; t=1701209664; cv=none; b=t7pqYtM8LaZTS6dPxHCITHluVlMqx8exqqLRKsWqjRGyvKZrJ8xik6BDhUpootP1ajNNZcDhw2iFG90kNpXbn+b9Z44k0L3+IXE+rROZKWk05HL2sgQzigLRlEGK8Jq5CSuyNCws1RjwmP8GEjbR/MIR3vvxnYBh76dnTUzRph8= ARC-Message-Signature: i=1; a=rsa-sha256; d=sourceware.org; s=key; t=1701209664; c=relaxed/simple; bh=Orf/KR7V5gQr0lERDAQSTSZj0HpyBC1BfcWLYwN7lUc=; h=DKIM-Signature:Message-ID:Date:MIME-Version:Subject:To:From; b=WOWWQq96C1d+R+jVaaeSLsI/qaAvZGfK/NxHC8IippeO5L7VBzYIco/7I5NWbu6kY39Hq/RWRoSkc5CatgethRIn0dS/YZPz6uTsdqm7EbYiyvtxcvO4c+tFqCStO87B9kiaXTe2E8/3Fj5W8uCNB/pKT1+oA1n2FW8BH+npeWk= ARC-Authentication-Results: i=1; server2.sourceware.org Received: by mail-pf1-x42a.google.com with SMTP id d2e1a72fcca58-6b7f0170d7bso5608034b3a.2 for ; Tue, 28 Nov 2023 14:14:22 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1701209661; x=1701814461; darn=gcc.gnu.org; h=content-transfer-encoding:in-reply-to:from:references:cc:to :content-language:subject:user-agent:mime-version:date:message-id :from:to:cc:subject:date:message-id:reply-to; bh=cjpOL7ZuWy344mXV1/IsQzBnl6uLyo/6FNZsdHvv/vM=; b=KgTF0P3JpL4Iee7s5+/P+wJtRV1vMcwgu5rBdC3GUTUqAaa4tg0f0riPRrbJH6wl7z MND4NowtqqyU83+DI96ZoNEJAeTz7uNgbid6XvzTLGOpWx2NbTo2PkCJx2QGg72O73jX 31qL0nE16siBueg1BvGixrCig8INByOANFx6zustLHo+OsIuCWeY8D31ZS2nTyRBAkjb eahddOIIdwRipEmFAJBXTmbYJzCyHBpJEWZtH9puVF/I+g8t9xuf9sTUI45CDYc4KxW6 asZJxTZiPR8lu7rtJjAsTpvB9eKYwdJjUBTeGpxDeJ8+JG2j7Ctkn7WWy32Ls043bMjS oI3w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1701209661; x=1701814461; h=content-transfer-encoding:in-reply-to:from:references:cc:to :content-language:subject:user-agent:mime-version:date:message-id :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=cjpOL7ZuWy344mXV1/IsQzBnl6uLyo/6FNZsdHvv/vM=; b=Tbx5I/Xm2OiBJ/K9aBu1mWDVfGLV3IG2xCqOcj1aCqVZqv0xNKb6X7YXRfguHQnhj1 DBW1GDBLJ7+nq/82Mp/zgvvspATae8HjP7lE8KDrG6LVKJJ7KAnQi6himd5eysWywC4U ABw8Zb1C32+ls6+k7L57TzsFAWYiolT2iWSHaS/v3mRy+D0geQ6D9TpnlTl0+6/pllVD 7wWczga4N+cs/KNw8dQfSpj+qJ2F6GaXS9Ou83aIA0vmyyT4ahymmVJGCPh/tGEg+/kt q1oJVHEqhwCH++uXZWjxJJ0swGBuRMD53EucJdLi9Jm6NMh2PsMSTCafrka8LUGvD3BC JOsA== X-Gm-Message-State: AOJu0Yyz05sCwFGSGFq+KuAfYAsx0CDlBXlGs57v2D0mCa87X9C3ySKp niMxuamEuRt3zqRH1e+NZkQ= X-Google-Smtp-Source: AGHT+IGFrYniNInShJPTWGw0VvytLb029N+RISbhcCIgrB4hn4O9AXodxONeog3sNCAkQvBsC24KNw== X-Received: by 2002:a05:6a21:339e:b0:189:6cf5:7901 with SMTP id yy30-20020a056a21339e00b001896cf57901mr20434270pzb.33.1701209661189; Tue, 28 Nov 2023 14:14:21 -0800 (PST) Received: from [172.31.0.109] ([136.36.130.248]) by smtp.gmail.com with ESMTPSA id w8-20020a17090a15c800b0027722832498sm10893079pjd.52.2023.11.28.14.14.17 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 28 Nov 2023 14:14:20 -0800 (PST) Message-ID: <04f9ffdf-b52a-4b3c-890a-01f250b1f02a@gmail.com> Date: Tue, 28 Nov 2023 15:14:14 -0700 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: RISC-V: Support XTheadVector extensions Content-Language: en-US To: Palmer Dabbelt Cc: juzhe.zhong@rivai.ai, gcc-patches@gcc.gnu.org, Kito Cheng , kito.cheng@sifive.com, cooper.joshua@linux.alibaba.com, Robin Dapp References: From: Jeff Law In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Spam-Status: No, score=-2.3 required=5.0 tests=BAYES_00,DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,FREEMAIL_FROM,RCVD_IN_DNSWL_NONE,SPF_HELO_NONE,SPF_PASS,TXREP,T_SCC_BODY_TEXT_LINE autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on server2.sourceware.org List-Id: On 11/28/23 12:45, Palmer Dabbelt wrote: > > IMO we're just stuck between a rock and a hard place here. Specifically, > this isn't just an assembly syntax change but also comes with a bunch of > behaviorial changes to the instructions in question -- I'm specifically > thinking of things like the register packing, which IIRC changed a ton > between 0.7 and 0.8 (and then again more for 1.0). That's the kind of > stuff that tends to have non-local implications on the port, and thus > can trip people up. > > So if we model this as just assembly syntax then we risk people tripping > over the differences, but if we try to model it as a whole different > extension then we have more code to manage.  I'd start with the assembly > syntax approach, as it should be the option with less code which is > always nice.  If that turns out to be a problem then we can always just > duplicate the patterns, but it's way harder to merge them back together > if we start out with things duplicated. The way I think about the assembly bits is it allows us to share a good amount of code between the two implementations. There's obviously going to be some differences that will require more extensive work and that's where I think most of our review effort ought to be. > > During the patchwork call we also ended up talking about the P extension > (and the likely vendor flavors).  Nothing's appeared for there yet, but > the theory is that the RZ/Five (Renesas' line of RISC-V chips that came > out earlier this year) has some P-related extension.  There's also some > SIMD in CORE-V, as well as a bunch of low-hanging fruit missing from V > that we'll probably see more vendor extensions for. The only P bits that made the gcc-14 deadline were those from Embecosm, so I'd tend to want to push all the other P stuff out to gcc-15. > > So I think if the goal is to have a single vector target for RISC-V then > we've probably lost already. That's probably not feasible. But I think there's a good amount of sharable bits between the V1.0 and the thead-vector support. > >> But we've got time to sort this out.  I don't think the code in question >> was targeted towards gcc-14. > > [In case anyone else is watching: see the forked thread, it might be > amied for 14 now...] It's aimed for evaluation/review given the submission occurred before the gcc-14 deadline. jeff