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([2a02:c7c:74db:8d00:c01d:9d74:b630:9087]) by smtp.gmail.com with ESMTPSA id a6-20020adffac6000000b00306415ac69asm1398319wrs.15.2023.05.03.02.41.44 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 03 May 2023 02:41:44 -0700 (PDT) Message-ID: Date: Wed, 3 May 2023 10:41:42 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.10.0 Subject: Re: [PATCH 3/3] target/openrisc: Setup FPU for detecting tininess before rounding Content-Language: en-US To: Stafford Horne Cc: QEMU Development , Linux OpenRISC References: <20230502185731.3543420-1-shorne@gmail.com> <20230502185731.3543420-4-shorne@gmail.com> <933ff5d8-3875-34ac-9bc4-ed06f74efad7@linaro.org> From: Richard Henderson In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=2a00:1450:4864:20::429; envelope-from=richard.henderson@linaro.org; helo=mail-wr1-x429.google.com X-Spam_score_int: -34 X-Spam_score: -3.5 X-Spam_bar: --- X-Spam_report: (-3.5 / 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=-1.422, 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 5/3/23 10:14, Stafford Horne wrote: >>> + set_default_nan_mode(1, &cpu->env.fp_status); >>> + set_float_detect_tininess(float_tininess_before_rounding, >>> + &cpu->env.fp_status); >> >> You don't mention the nan change in the commit message. > > Right, and I am not sure I need it. Let me remove it and run tests again. I > was just adding it as a few other architectures did who set > float_tininess_before_rounding. What that does is *not* propagate NaN payloads from (some) input to the output. This is certainly true of RISC-V, which specifies this in their architecture manual. OpenRISC does not specify any NaN behaviour at all. It's not a bad choice, really, and it almost certainly simplifies the design of the FPU, as you can do NaN propagation and silencing in one step. r~