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[97.126.123.70]) by smtp.gmail.com with ESMTPSA id i2sm23118855pfr.151.2020.03.13.23.52.53 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 13 Mar 2020 23:52:53 -0700 (PDT) Subject: Re: [PATCH v5 17/60] target/riscv: vector single-width integer multiply instructions To: LIU Zhiwei , alistair23@gmail.com, chihmin.chao@sifive.com, palmer@dabbelt.com References: <20200312145900.2054-1-zhiwei_liu@c-sky.com> <20200312145900.2054-18-zhiwei_liu@c-sky.com> From: Richard Henderson Message-ID: Date: Fri, 13 Mar 2020 23:52:51 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.4.1 MIME-Version: 1.0 In-Reply-To: <20200312145900.2054-18-zhiwei_liu@c-sky.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-detected-operating-system: by eggs.gnu.org: Genre and OS details not recognized. X-Received-From: 2607:f8b0:4864:20::642 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: guoren@linux.alibaba.com, wenmeng_zhang@c-sky.com, qemu-riscv@nongnu.org, qemu-devel@nongnu.org, wxy194768@alibaba-inc.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 3/12/20 7:58 AM, LIU Zhiwei wrote: > +static int64_t do_mulhsu_d(int64_t s2, uint64_t s1) > +{ > + uint64_t hi_64, lo_64, abs_s2 = s2; > + > + if (s2 < 0) { > + abs_s2 = -s2; > + } > + mulu64(&lo_64, &hi_64, abs_s2, s1); > + if ((int64_t)(s2 ^ s1) < 0) { Why would the sign of s1 be relevant? It's always unsigned. We have code for this in e.g. tcg_gen_mulsu2_i64 mulu4(&lo, &hi, s1, s2); if ((int64_t)s2 < 0) { hi -= s2; } r~