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[37.24.206.209]) by smtp.gmail.com with ESMTPSA id r13-20020a05600c458d00b00417f65f148esm19742110wmo.31.2024.04.22.01.45.17 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 22 Apr 2024 01:45:17 -0700 (PDT) Message-ID: <7ef5ed97-e1b8-43d6-b369-f8858ddb7ace@suse.com> Date: Mon, 22 Apr 2024 10:45:19 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] x86/Intel: SHLD/SHRD have dual meaning Content-Language: en-US To: "Cui, Lili" Cc: Binutils , "H.J. Lu" , Hongtao Liu References: <117c9c1f-795e-41f9-b582-b8477b42bebd@suse.com> <563b29cc-d3b5-45b7-b354-1ca8f3a2dcf4@suse.com> From: Jan Beulich Autocrypt: addr=jbeulich@suse.com; keydata= xsDiBFk3nEQRBADAEaSw6zC/EJkiwGPXbWtPxl2xCdSoeepS07jW8UgcHNurfHvUzogEq5xk hu507c3BarVjyWCJOylMNR98Yd8VqD9UfmX0Hb8/BrA+Hl6/DB/eqGptrf4BSRwcZQM32aZK 7Pj2XbGWIUrZrd70x1eAP9QE3P79Y2oLrsCgbZJfEwCgvz9JjGmQqQkRiTVzlZVCJYcyGGsD /0tbFCzD2h20ahe8rC1gbb3K3qk+LpBtvjBu1RY9drYk0NymiGbJWZgab6t1jM7sk2vuf0Py O9Hf9XBmK0uE9IgMaiCpc32XV9oASz6UJebwkX+zF2jG5I1BfnO9g7KlotcA/v5ClMjgo6Gl MDY4HxoSRu3i1cqqSDtVlt+AOVBJBACrZcnHAUSuCXBPy0jOlBhxPqRWv6ND4c9PH1xjQ3NP nxJuMBS8rnNg22uyfAgmBKNLpLgAGVRMZGaGoJObGf72s6TeIqKJo/LtggAS9qAUiuKVnygo 3wjfkS9A3DRO+SpU7JqWdsveeIQyeyEJ/8PTowmSQLakF+3fote9ybzd880fSmFuIEJldWxp Y2ggPGpiZXVsaWNoQHN1c2UuY29tPsJgBBMRAgAgBQJZN5xEAhsDBgsJCAcDAgQVAggDBBYC AwECHgECF4AACgkQoDSui/t3IH4J+wCfQ5jHdEjCRHj23O/5ttg9r9OIruwAn3103WUITZee e7Sbg12UgcQ5lv7SzsFNBFk3nEQQCACCuTjCjFOUdi5Nm244F+78kLghRcin/awv+IrTcIWF hUpSs1Y91iQQ7KItirz5uwCPlwejSJDQJLIS+QtJHaXDXeV6NI0Uef1hP20+y8qydDiVkv6l IreXjTb7DvksRgJNvCkWtYnlS3mYvQ9NzS9PhyALWbXnH6sIJd2O9lKS1Mrfq+y0IXCP10eS FFGg+Av3IQeFatkJAyju0PPthyTqxSI4lZYuJVPknzgaeuJv/2NccrPvmeDg6Coe7ZIeQ8Yj t0ARxu2xytAkkLCel1Lz1WLmwLstV30g80nkgZf/wr+/BXJW/oIvRlonUkxv+IbBM3dX2OV8 AmRv1ySWPTP7AAMFB/9PQK/VtlNUJvg8GXj9ootzrteGfVZVVT4XBJkfwBcpC/XcPzldjv+3 HYudvpdNK3lLujXeA5fLOH+Z/G9WBc5pFVSMocI71I8bT8lIAzreg0WvkWg5V2WZsUMlnDL9 mpwIGFhlbM3gfDMs7MPMu8YQRFVdUvtSpaAs8OFfGQ0ia3LGZcjA6Ik2+xcqscEJzNH+qh8V m5jjp28yZgaqTaRbg3M/+MTbMpicpZuqF4rnB0AQD12/3BNWDR6bmh+EkYSMcEIpQmBM51qM EKYTQGybRCjpnKHGOxG0rfFY1085mBDZCH5Kx0cl0HVJuQKC+dV2ZY5AqjcKwAxpE75MLFkr wkkEGBECAAkFAlk3nEQCGwwACgkQoDSui/t3IH7nnwCfcJWUDUFKdCsBH/E5d+0ZnMQi+G0A nAuWpQkjM1ASeQwSHEeAWPgskBQL In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Spam-Status: No, score=-3025.0 required=5.0 tests=BAYES_00,DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_NONE,SPF_HELO_NONE,SPF_NONE,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 22.04.2024 09:43, Cui, Lili wrote: >> On 22.04.2024 06:09, Hongtao Liu wrote: >>> On Fri, Apr 19, 2024 at 5:29 PM Jan Beulich wrote: >>>> >>>> Since we uniformly permit D suffixes in Intel mode whenever in AT&T >>>> mode an L suffix may be used, we need to be consistent with this. >>> I think we need to forbid the D suffix for APX NDD SHL/SHR under Intel >>> mode to avoid ambiguity. >> >> Hmm. Special casing just two insns is out of question imo (in fact that's what >> is - unintentionally - partly happening prior to the change here). >> >>> Neither SHL (always SAL), nor SHR with a D suffix (Intel mode) is >>> generated by GCC. >> >> While this may be deemed helpful, I actually view it as a mistake, even if only >> from a cosmetic perspective: SHL is the main insn; SAL is merely an alias >> (questionably using extension opcode 4 rather than 6 in gas). >> >> Still extending what you suggest - limiting the restriction to APX - may be an >> option, albeit ... >> >>>> --- >>>> The alternative, more intrusive and more risky (in terms of perceived >>>> or even real regressions) route would be to mark the few insns which >>>> permit suffixes even in Intel syntax, and reject suffix uses when >>>> that indicator isn't set. >> >> ... as implied here I'd still consider this inconsistent. >> >> Furthermore the point in time when suffixes are processed off of the >> incoming mnemonic is too early to know whether an insn is having an APX >> representation. Hence doing said extension of what you suggest would likely >> end up quite hacky. >> > > If the user messes them up, we can't figure out the original intention because the input is exactly the same, maybe we can find a suitable place to inform the user that shl + apx ndd does not support suffix? See my other reply to Hongtao. Plus, as said before, I'd much prefer if we wouldn't start special-casing any specific insns in this regard. (Which isn't to say that may not end up being necessary here.) Jan