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[174.21.70.228]) by smtp.gmail.com with ESMTPSA id b16sm35366pju.35.2021.05.26.12.23.02 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 26 May 2021 12:23:03 -0700 (PDT) Subject: Re: Denormal input handling To: morrell@alumni.ucsd.edu, qemu-devel@nongnu.org References: <746277332.296230.1622055775751.ref@mail.yahoo.com> <746277332.296230.1622055775751@mail.yahoo.com> From: Richard Henderson Message-ID: <4bc4444e-782a-311c-719d-091a04e20387@linaro.org> Date: Wed, 26 May 2021 12:23:01 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.8.1 MIME-Version: 1.0 In-Reply-To: <746277332.296230.1622055775751@mail.yahoo.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=2607:f8b0:4864:20::433; envelope-from=richard.henderson@linaro.org; helo=mail-pf1-x433.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, NICE_REPLY_A=-0.001, 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: 2.1.23 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" On 5/26/21 12:02 PM, Michael Morrell via wrote: > I think the behavior should be for denormal inputs that if "flush_inputs_to_zero" is true, then set the value to zero (without setting the "input denormal" flag); and if "flush_inputs_to_zero" is false, set the "input denormal" flag and normalize the input. > > This matches what x86 does (I'm not sure about other architectures). It is not. Intel Architectures SDM Vol 1, Section 11.5.2.2: The denormal operand exception is not affected by flush-to-zero mode. r~