From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from terminus.zytor.com (terminus.zytor.com [198.137.202.136]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id B6F755381; Sat, 20 Jan 2024 09:01:20 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=198.137.202.136 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1705741283; cv=none; b=YdsrMpCN7zTr/2jozwZgR1V+e6W97rr4rq2VRc+Qzer96OkvBakKVmhinLi0EBwj0Rs35FnQonAlYzxjKhkAHaN6Lcov48gvWc0T9dAkqAGnnZyjrWzWwBhVol3yxzgX538xbdojrbQMlQk6A/n1/VdkKRgv3IA60D5fj7R99Lk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1705741283; c=relaxed/simple; bh=lPXJNVUz1/fxRSsS978CphntnmhX4z/aYDogC1GW6zw=; h=Date:From:To:CC:Subject:In-Reply-To:References:Message-ID: MIME-Version:Content-Type; b=VsJqyr1FHVwQzaJjig2GVZBqBWknbLMHBynYn6QaTH0FiIDjlGmmfTnqLD2p3fVbt/cJMni3gnDNad5bYWuJ8YyIIZkcNI30ssdL9hFDAoFPh0Vc95V5275lqwC7RwFE67+a/l1pol9o0qcz7wW/lKJz4KGwEDmMzadNmPkUQzQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=zytor.com; spf=pass smtp.mailfrom=zytor.com; dkim=pass (2048-bit key) header.d=zytor.com header.i=@zytor.com header.b=Vly5evUB; arc=none smtp.client-ip=198.137.202.136 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=zytor.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=zytor.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=zytor.com header.i=@zytor.com header.b="Vly5evUB" Received: from [127.0.0.1] ([76.133.66.138]) (authenticated bits=0) by mail.zytor.com (8.17.2/8.17.1) with ESMTPSA id 40K8N2VF1422225 (version=TLSv1.3 cipher=TLS_AES_128_GCM_SHA256 bits=128 verify=NO); Sat, 20 Jan 2024 00:23:04 -0800 DKIM-Filter: OpenDKIM Filter v2.11.0 mail.zytor.com 40K8N2VF1422225 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=zytor.com; s=2024011201; t=1705738988; bh=aZJr2zzOCbDOkGwxtzRA09fk3E/DAYeJRrK4E21Gt3c=; h=Date:From:To:CC:Subject:In-Reply-To:References:From; b=Vly5evUBwlByZI3SYmfdzkHI4CXMNuCX8pyZvJeZzeu7xZt3fYyNMWnX+UAepeZLF TNecSnOrFb6g/VzC7UpOMHQJ4cNaC0KPjibXjvLi+yTwu2BpxUWmWNlDZhmBgf2SoW MNgrOtThybINUZ1uFmT3O04FS0vre6trudKUndRuaqSstBzMA0JJpshRaC/SXamuhr bBo67i6WfCXwqixEvyMbelIhFGSfCS67zQV93NxRsQzAMy2sELFdY4KipUo3Y2/aZt 0vGOP1lkjBHdcEY0+SIgYiU+zhLlyfldE4fhYPXyGxgOyCgL+ENDPmOFh5zVsnTzRD 94gHU8qNWzpsg== Date: Sat, 20 Jan 2024 00:22:59 -0800 From: "H. Peter Anvin" To: Thorsten Glaser , Peter Zijlstra CC: x86@kernel.org, rostedt@goodmis.org, torvalds@linuxfoundation.org, linux-kernel@vger.kernel.org, linux-toolchains@vger.kernel.org, jpoimboe@redhat.com, alexei.starovoitov@gmail.com, mhiramat@kernel.org Subject: Re: [PATCH 1/2] x86: Remove dynamic NOP selection User-Agent: K-9 Mail for Android In-Reply-To: References: <20210312113253.305040674@infradead.org> <20210312115749.065275711@infradead.org> Message-ID: Precedence: bulk X-Mailing-List: linux-toolchains@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable On January 19, 2024 10:58:56 PM PST, Thorsten Glaser wrot= e: >Peter Zijlstra dixit: > >>-/* generic versions from gas >[=E2=80=A6] >>- 3: leal 0x00(%esi),%esi >>- 4: leal 0x00(,%esi,1),%esi >>- 6: leal 0x00000000(%esi),%esi >>- 7: leal 0x00000000(,%esi,1),%esi > >vs=2E > >>+ * Generic 32bit nops from GAS: >[=E2=80=A6] >>+ * 3: leal 0x0(%esi),%esi >>+ * 4: leal 0x0(%esi,%eiz,1),%esi >>+ * 5: leal %ds:0x0(%esi,%eiz,1),%esi >>+ * 6: leal 0x0(%esi),%esi >>+ * 7: leal 0x0(%esi,%eiz,1),%esi >>+ * 8: leal %ds:0x0(%esi,%eiz,1),%esi > >I think there=E2=80=99s some mistake introduced=2E The BYTES_* are >identical for e=2Eg=2E #7, but %eiz must be wrong, it=E2=80=99s not >a register=2E Indeed, gas (on Debian bullseye) does not >assemble that either=2E > >(Awful AT&T syntax aside=E2=80=A6) > >bye, >//mirabilos %eiz was something that binutils used to put in when disassembling certain= redundant encodings with SIB at some point=2E