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[187.189.51.144]) by smtp.gmail.com with ESMTPSA id 91sm1252143ott.55.2020.10.01.08.26.37 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 01 Oct 2020 08:26:38 -0700 (PDT) Subject: Re: [PATCH v1 03/20] s390x/tcg: Implement VECTOR MULTIPLY SUM LOGICAL To: David Hildenbrand , qemu-devel@nongnu.org References: <20200930145523.71087-1-david@redhat.com> <20200930145523.71087-4-david@redhat.com> From: Richard Henderson Message-ID: Date: Thu, 1 Oct 2020 10:26:36 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <20200930145523.71087-4-david@redhat.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=2607:f8b0:4864:20::242; envelope-from=richard.henderson@linaro.org; helo=mail-oi1-x242.google.com X-detected-operating-system: by eggs.gnu.org: No matching host in p0f cache. That's all we know. X-Spam_score_int: -23 X-Spam_score: -2.4 X-Spam_bar: -- X-Spam_report: (-2.4 / 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, NICE_REPLY_A=-0.26, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=unavailable autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: qemu-s390x@nongnu.org, Cornelia Huck , Thomas Huth Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 9/30/20 9:55 AM, David Hildenbrand wrote: > + /* Multipy both even elements from v2 and v3 */ > + read_vec_element_i64(l1, get_field(s, v2), 0, ES_64); > + read_vec_element_i64(h1, get_field(s, v3), 0, ES_64); > + tcg_gen_mulu2_i64(l1, h1, l1, h1); > + /* Shift result left by one bit if requested */ > + if (extract32(get_field(s, m6), 3, 1)) { > + tcg_gen_extract2_i64(h1, l1, h1, 63); > + tcg_gen_shli_i64(l1, l1, 1); > + } Not a bug, but some hosts require 3 insns for extract2 (so 4 total for this sequence). This doubling can also be had via add2: tcg_gen_add2_i64(l1, h1, l1, h1, l1, h1); At which point most hosts will require only 2 insns for this sequence. The two hosts that don't have a carry bit (mips, riscv), will still be able to perform the add in 3 insns. So add is never more expensive and sometimes half as expensive. Regardless, Reviewed-by: Richard Henderson r~