From: "H.J. Lu" <hjl.tools@gmail.com>
To: Jan Beulich <jbeulich@suse.com>
Cc: Haochen Jiang <haochen.jiang@intel.com>,
wwwhhhyyy <hongyu.wang@intel.com>,
binutils@sourceware.org
Subject: Re: [PATCH 01/10] Support Intel AVX-IFMA
Date: Mon, 17 Oct 2022 15:23:32 -0700 [thread overview]
Message-ID: <CAMe9rOpKQSiHE_VBd-F=v-FBd+k1OF7vrrWNLdUKv_k_bKiv4A@mail.gmail.com> (raw)
In-Reply-To: <e15d0cad-c4ad-b0ac-5424-1c804ec3549d@suse.com>
On Sat, Oct 15, 2022 at 11:39 PM Jan Beulich <jbeulich@suse.com> wrote:
>
> On 14.10.2022 20:10, H.J. Lu wrote:
> > On Fri, Oct 14, 2022 at 2:52 AM Jan Beulich <jbeulich@suse.com> wrote:
> >>
> >> On 14.10.2022 11:12, Haochen Jiang wrote:
> >>> From: wwwhhhyyy <hongyu.wang@intel.com>
> >>>
> >>> 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.
>
> So again: Why is this necessary when a programmer disabled AVX512? I fully
> agree we need to pick the EVEX encoding by default if available, but I see
> no reason whatsoever to insist on a {vex} prefix when the EVEX variant is
> unavailable anyway. As you said back at the time for AVX-VNNI - this was a
> design decision taken at Intel. Which is fine for a draft implementation.
> But decisions for an open source project should be taken in the open, and
> opinions of others should not simply be put off.
>
We can discuss how to initialize i.vec_encoding. But it is orthogonal to
this patch.
--
H.J.
next prev parent reply other threads:[~2022-10-17 22:24 UTC|newest]
Thread overview: 120+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-10-14 9:12 [PATCH 0/10] Add new Intel Sierra Forest, Grand Ridge, Granite Rapids Instructions Haochen Jiang
2022-10-14 9:12 ` [PATCH 01/10] Support Intel AVX-IFMA Haochen Jiang
2022-10-14 9:52 ` Jan Beulich
2022-10-14 18:10 ` H.J. Lu
2022-10-16 6:39 ` Jan Beulich
2022-10-17 22:23 ` H.J. Lu [this message]
2022-10-18 5:33 ` Jan Beulich
2022-10-18 21:28 ` H.J. Lu
2022-10-19 6:01 ` Jan Beulich
2022-10-19 21:27 ` H.J. Lu
2022-10-20 6:15 ` Jan Beulich
2022-10-24 2:07 ` Jiang, Haochen
2022-10-24 5:53 ` Jiang, Haochen
2022-10-24 19:09 ` H.J. Lu
2022-10-25 6:29 ` Jan Beulich
2022-10-14 9:12 ` [PATCH 02/10] Support Intel AVX-VNNI-INT8 Haochen Jiang
2022-10-14 10:57 ` Jan Beulich
2022-10-21 3:22 ` Jiang, Haochen
2022-10-25 1:52 ` H.J. Lu
2022-10-14 9:12 ` [PATCH 03/10] Support Intel AVX-NE-CONVERT Haochen Jiang
2022-10-14 12:58 ` Jan Beulich
2022-10-24 5:37 ` Kong, Lingling
2022-10-24 5:59 ` Kong, Lingling
2022-10-24 19:25 ` H.J. Lu
2022-10-25 6:44 ` Jan Beulich
2022-10-14 9:12 ` [PATCH 04/10] Support Intel CMPccXADD Haochen Jiang
2022-10-14 13:46 ` Jan Beulich
2022-10-14 18:27 ` H.J. Lu
2022-10-14 21:51 ` H.J. Lu
2022-10-16 6:34 ` Jan Beulich
2022-10-17 23:31 ` H.J. Lu
2022-10-16 6:25 ` Jan Beulich
2022-10-17 23:44 ` H.J. Lu
2022-10-16 6:19 ` Jan Beulich
2022-10-24 2:30 ` Jiang, Haochen
2022-10-24 19:12 ` H.J. Lu
2022-10-24 5:55 ` Jiang, Haochen
2022-10-25 6:53 ` Jan Beulich
2022-10-26 3:03 ` Jiang, Haochen
2022-10-26 8:49 ` Jan Beulich
2022-10-27 3:09 ` Jiang, Haochen
2022-10-27 6:37 ` Jan Beulich
2022-10-28 0:59 ` Jiang, Haochen
2022-10-14 9:12 ` [PATCH 05/10] Add handler for more i386_cpu_flags Haochen Jiang
2022-10-14 13:53 ` Jan Beulich
2022-10-14 9:12 ` [PATCH 06/10] Support Intel RAO-INT Haochen Jiang
2022-10-14 14:38 ` Jan Beulich
2022-10-16 6:15 ` Jan Beulich
2022-10-24 3:12 ` Jiang, Haochen
2022-10-24 19:17 ` H.J. Lu
2022-10-24 5:56 ` Jiang, Haochen
2022-10-25 7:01 ` Jan Beulich
2022-10-26 5:16 ` Jiang, Haochen
2022-10-26 8:56 ` Jan Beulich
2022-10-27 3:50 ` Jiang, Haochen
2022-10-27 6:39 ` Jan Beulich
2022-10-27 18:46 ` H.J. Lu
2022-10-28 6:52 ` Jan Beulich
2022-10-28 8:10 ` Jiang, Haochen
2022-10-28 8:22 ` Jan Beulich
2022-10-28 8:31 ` Jiang, Haochen
2022-10-28 8:40 ` Jan Beulich
2022-10-28 16:08 ` H.J. Lu
2022-10-31 9:41 ` Jan Beulich
2022-10-31 16:49 ` H.J. Lu
2022-11-06 12:50 ` Kong, Lingling
2022-11-07 9:24 ` Jan Beulich
2022-11-07 13:37 ` Kong, Lingling
2022-11-07 20:03 ` H.J. Lu
2022-10-17 23:23 ` H.J. Lu
2022-10-18 5:38 ` Jan Beulich
2022-10-14 9:12 ` [PATCH 07/10] Support Intel WRMSRNS Haochen Jiang
2022-10-17 7:17 ` Jan Beulich
2022-10-24 2:52 ` Jiang, Haochen
2022-10-24 5:56 ` Jiang, Haochen
2022-10-24 19:14 ` H.J. Lu
2022-10-25 7:04 ` Jan Beulich
2022-10-14 9:12 ` [PATCH 08/10] Support Intel MSRLIST Haochen Jiang
2022-10-17 7:20 ` Jan Beulich
2022-10-24 3:03 ` Jiang, Haochen
2022-10-24 5:56 ` Jiang, Haochen
2022-10-24 19:15 ` H.J. Lu
2022-10-25 7:07 ` Jan Beulich
2022-10-14 9:12 ` [PATCH 09/10] Support Intel AMX-FP16 Haochen Jiang
2022-10-17 7:35 ` Jan Beulich
2022-10-18 9:01 ` Cui, Lili
2022-10-18 9:23 ` Jan Beulich
2022-10-18 9:33 ` Jiang, Haochen
2022-10-19 10:33 ` Cui, Lili
2022-10-19 13:35 ` Jan Beulich
2022-10-19 14:05 ` Cui, Lili
2022-10-19 14:09 ` Jan Beulich
2022-10-19 14:41 ` Cui, Lili
2022-10-19 15:04 ` Jan Beulich
2022-10-19 15:21 ` Cui, Lili
2022-10-19 14:01 ` Jiang, Haochen
2022-10-19 14:13 ` Jan Beulich
2022-10-19 14:58 ` Jiang, Haochen
2022-10-25 6:02 ` Jan Beulich
2022-10-25 13:05 ` Cui, Lili
2022-10-14 9:12 ` [PATCH 10/10] Support Intel PREFETCHI Haochen Jiang
2022-10-17 8:15 ` Jan Beulich
2022-10-25 13:03 ` Cui, Lili
2022-10-25 15:41 ` Jan Beulich
2022-10-25 15:52 ` Jan Beulich
2022-10-25 17:01 ` H.J. Lu
2022-10-26 13:42 ` Cui, Lili
2022-10-26 13:53 ` Jan Beulich
2022-10-27 6:04 ` Cui, Lili
2022-10-27 6:45 ` Jan Beulich
2022-10-27 7:01 ` Cui, Lili
2022-10-27 7:15 ` Jan Beulich
2022-10-27 7:43 ` Cui, Lili
2022-10-28 9:03 ` Cui, Lili
2022-10-28 15:54 ` H.J. Lu
2022-10-31 13:23 ` Cui, Lili
2022-10-31 14:45 ` Mike Frysinger
2022-10-31 16:25 ` H.J. Lu
2022-10-19 14:55 [PATCH v2 0/10] Add new Intel Sierra Forest, Grand Ridge, Granite Rapids Instructions Haochen Jiang
2022-10-19 14:55 ` [PATCH 01/10] Support Intel AVX-IFMA Haochen Jiang
2022-10-19 15:15 [PATCH v2 0/10] Add new Intel Sierra Forest, Grand Ridge, Granite Rapids Instructions (Resend) Haochen Jiang
2022-10-19 15:15 ` [PATCH 01/10] Support Intel AVX-IFMA Haochen Jiang
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