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[174.21.146.124]) by smtp.gmail.com with ESMTPSA id 14-20020a17090a19ce00b00277371fd346sm13176pjj.30.2023.09.28.14.32.59 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 28 Sep 2023 14:32:59 -0700 (PDT) Message-ID: Date: Thu, 28 Sep 2023 14:32:58 -0700 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.15.1 Subject: Re: [PATCH 3/8] target/sparc: Fix VIS fmul8x16al instruction. Content-Language: en-US To: Nick Bowler , qemu-devel@nongnu.org Cc: Mark Cave-Ayland , Artyom Tarasenko References: <20230925050545.30912-1-nbowler@draconx.ca> <20230925050545.30912-4-nbowler@draconx.ca> From: Richard Henderson In-Reply-To: <20230925050545.30912-4-nbowler@draconx.ca> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=2607:f8b0:4864:20::534; envelope-from=richard.henderson@linaro.org; helo=mail-pg1-x534.google.com X-Spam_score_int: -35 X-Spam_score: -3.6 X-Spam_bar: --- X-Spam_report: (-3.6 / 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=-1.473, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 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 9/24/23 01:03, Nick Bowler wrote: > On a real UltraSparc II, the fmul8x16al instruction takes two single- > precision input operands and returns a double-precision result. For > the second operand, bits 15:0 are used, and bits 31:16 are ignored. > > However, the emulation is taking two double-precision input operands, > and furthermore it is using bits 31:16 of the second operand (ignoring > bits 15:0). These are unlikely to contain the correct values. > > Even still, the emulator overwrites the second input before all outputs > are calculated, so even if by chance the data loaded in happens to be > correct, the results are just garbage except in trivial cases. > > Signed-off-by: Nick Bowler > --- > target/sparc/helper.h | 2 +- > target/sparc/translate.c | 2 +- > target/sparc/vis_helper.c | 11 ++++++----- > 3 files changed, 8 insertions(+), 7 deletions(-) Reviewed-by: Richard Henderson r~