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[173.197.98.125]) by smtp.gmail.com with ESMTPSA id 6-20020a170902c10600b001db2b8b2da7sm1683441pli.122.2024.02.15.13.11.01 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 15 Feb 2024 13:11:02 -0800 (PST) Message-ID: <5e15fe47-94ce-4d25-a517-d766e70ac853@linaro.org> Date: Thu, 15 Feb 2024 11:10:59 -1000 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4 09/10] util/bufferiszero: Add simd acceleration for aarch64 Content-Language: en-US To: Alexander Monakov Cc: qemu-devel@nongnu.org, mmromanov@ispras.ru References: <20240215081449.848220-1-richard.henderson@linaro.org> <20240215081449.848220-10-richard.henderson@linaro.org> <1f038576-5121-e84c-8196-ae5f9ca3a75b@ispras.ru> <6499be56-2002-44b3-9c53-1a1ec2fde53f@linaro.org> <1e4d5081-d86b-84f5-20f7-8e48044b751a@ispras.ru> From: Richard Henderson In-Reply-To: <1e4d5081-d86b-84f5-20f7-8e48044b751a@ispras.ru> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=2607:f8b0:4864:20::635; envelope-from=richard.henderson@linaro.org; helo=mail-pl1-x635.google.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On 2/15/24 08:46, Alexander Monakov wrote: > Right, so we can pick the cheapest reduction method, and if I'm reading > Neoverse-N1 SOG right, SHRN is marginally cheaper than ADDV (latency 2 > instead of 3), and it should be generally preferable on other cores, no? Fair. > For that matter, cannot UQXTN (unsigned saturating extract narrow) be > used in place of CMEQ+ADDV here? Interesting. I hadn't thought about using saturation to preserve non-zeroness like that. Using 1 4-cycle insn instead of 2 2-cycle insns is interesting as well. I suppose, since it's at the end of the dependency chain, the fact that it is restricted to the V1 pipe matters not at all. r~