From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qt1-x82d.google.com (mail-qt1-x82d.google.com [IPv6:2607:f8b0:4864:20::82d]) by sourceware.org (Postfix) with ESMTPS id F2D1E385842F for ; Fri, 14 Oct 2022 18:10:38 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org F2D1E385842F Authentication-Results: sourceware.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: sourceware.org; spf=pass smtp.mailfrom=gmail.com Received: by mail-qt1-x82d.google.com with SMTP id g11so4192202qts.1 for ; Fri, 14 Oct 2022 11:10:38 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=cc:to:subject:message-id:date:from:in-reply-to:references :mime-version:from:to:cc:subject:date:message-id:reply-to; bh=cUgPbr78AYMFQxoyJHFkUnxbSmOzTPaedHh8qEySs7g=; b=XnWCDsfvtjZxb5VD0SJerfg8pR/at1dIvFBw76ZZ99pdPJdDXsnJR/o+HQx69b7R+I +tkHMswFbqzBt5DfNLFI4G1x+EVtGbpdYPhx+Mbdwrph8+rhIiPfQbynx+RJJu/lqz/o SmOqD/5YrNv5f9YK3lDx4FsuzY4NTEQejKPqPbjsU7Ycd2xfZqon+/QtnqOM9XsfOeNT 5rTtNPGOnbJWaaLVU1t9TMfSAtwJCfFbmJhw705vUw+mTvLgv0RJw/dBMYzsz5Er71K/ AhBNYh/L9xxDV9CGUnEID41uFiILiD+NV72iQaEGPCSz+qI296zodd/56+O5PuesWgJE Fq0A== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=cc:to:subject:message-id:date:from:in-reply-to:references :mime-version:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=cUgPbr78AYMFQxoyJHFkUnxbSmOzTPaedHh8qEySs7g=; b=M9rNCKu3g4Tw4xc4RhiyrRsQr8RlvJtEwAwyMAJhveVivCbYMrmMEgoGhzGffF9LZL hGdk9AdlUUD5H3z1nqG6Nh6AJJ1wiMeBitzxTfj6Md3NMA8QDo3su6RNgRhCeAcy6nFV xBUinnxlTHxEa9+G6VWE+IGgZVvAQj6Yy0JMzAc3YMThFFwAQZY3w3QeIEGdLwenKyIO oAgyj8mbL/YZaauWJ4+khbZ6hO0eHFz7sezDOxg0WVkPkfccorDvkXd0FVqZTZJ7HqLH hIGLdg/aSylvOuIqgx86rVy9UJPBymvAcPkPNHVQtXVe0VfqyxHsRu8xgIfHVmDMLNLE Elew== X-Gm-Message-State: ACrzQf0h3uRqz4lirKi/eY9ZeGYFJqoUxiph90bKqOlG2Tbb2enEBr07 2Nszu7zuCqeKRvJLP7Lk1yxI3TFlmzIgk58G0BY64MpDolY= X-Google-Smtp-Source: AMsMyM74K+xfPLHGBap7GRcO4Ukk/kBK06VYKA2Kh+4/NZV5qneM0+90VtMbMPvoLL0VvlH3+9FJSTATKoBGa85BFNo= X-Received: by 2002:a05:622a:134b:b0:39a:4442:cbb6 with SMTP id w11-20020a05622a134b00b0039a4442cbb6mr5243263qtk.500.1665771038312; Fri, 14 Oct 2022 11:10:38 -0700 (PDT) MIME-Version: 1.0 References: <20221014091248.4920-1-haochen.jiang@intel.com> <20221014091248.4920-2-haochen.jiang@intel.com> <863655db-f202-477f-c638-00773c25886c@suse.com> In-Reply-To: <863655db-f202-477f-c638-00773c25886c@suse.com> From: "H.J. Lu" Date: Fri, 14 Oct 2022 11:10:02 -0700 Message-ID: Subject: Re: [PATCH 01/10] Support Intel AVX-IFMA To: Jan Beulich Cc: Haochen Jiang , wwwhhhyyy , binutils@sourceware.org Content-Type: text/plain; charset="UTF-8" X-Spam-Status: No, score=-3018.0 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 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 Fri, Oct 14, 2022 at 2:52 AM Jan Beulich wrote: > > On 14.10.2022 11:12, Haochen Jiang wrote: > > From: wwwhhhyyy > > > > x86: Support Intel AVX-IFMA > > > > Intel AVX IFMA instructions are marked with CpuVEX_PREFIX, which is > > cleared by default. Without {vex} pseudo prefix, Intel IFMA instructions > > are encoded with EVEX prefix. {vex} pseudo prefix will turn on VEX > > encoding for Intel IFMA instructions. > > I firmly object to the proliferation of this mis-feature. As expressed > before for AVX-VNNI, as long as the user has disabled AVX512 (or > respective sub-features thereof), there should be no need to use {vex} in > the source code. There's also no reason at all to make the disassembler > print {vex} prefixes - we don't do so for any other insns (apart from > AVX-VNNI) where an ambiguity exists between their VEX and EVEX encodings > (when none of the EVEX-specific features is used). The {vex} prefix is used with AVX-IFMA instructions so that IFMA instructions without a prefix, which are generated by compilers or handwritten, will be always encoded with EVEX. > I actually have a patch queued to undo the odd behavior for AVX-VNNI, at > least on the assembler side (which also drops the PseudoVexPrefix > attribute). > -- H.J.