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[97.113.7.119]) by smtp.gmail.com with ESMTPSA id v44sm3832336pgn.17.2019.09.20.15.09.42 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 20 Sep 2019 15:09:42 -0700 (PDT) Subject: Re: [PATCH v2 10/16] tests/tcg: add generic version of float_convs To: =?UTF-8?Q?Alex_Benn=c3=a9e?= References: <20190919171015.12681-1-alex.bennee@linaro.org> <20190919171015.12681-11-alex.bennee@linaro.org> <87impnz568.fsf@linaro.org> <87h857z32j.fsf@linaro.org> From: Richard Henderson Openpgp: preference=signencrypt Message-ID: <0b0c45c7-4b9b-0d03-01aa-25a689a8f914@linaro.org> Date: Fri, 20 Sep 2019 15:09:40 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 MIME-Version: 1.0 In-Reply-To: <87h857z32j.fsf@linaro.org> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit X-detected-operating-system: by eggs.gnu.org: Genre and OS details not recognized. X-Received-From: 2607:f8b0:4864:20::442 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: peter.maydell@linaro.org, qemu-arm@nongnu.org, qemu-devel@nongnu.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 9/20/19 3:15 AM, Alex Bennée wrote: > I can't figure out what is meant to be going on with CONVERT_BITS. It > seems to be implying there is a direct relationship between status flags > and the exception disable bits. But that is confusing because integer > overflow (IOV) and float overflow (OVF) are different flags bit I assume > both suppressed by Overflow Disable (OVFD). I had failed to notice that the kernel routine plays with INV and not IOV for the emulation of CVTTQ, so it's the SWCR_TRAP_ENABLE_INV bit that controls whether CVTTQ/S raises a signal. Will fix. > Why are we doing this magic 32 bit shuffling anyway? Is it purely to > save 32 bits of a mostly empty lower half of the FPCR register? Yes. Which is not a great answer, but it was done years ago and there's little point in changing it back now. r~