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From: Richard Henderson <richard.henderson@linaro.org>
Message-ID: <7556aba5-052b-8cc1-1f92-d7d0f664cfa3@linaro.org>
Date: Wed, 16 Jan 2019 09:05:45 +1100
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Subject: Re: [Qemu-devel] [PATCH] include/fpu/softfloat: Fix compilation
 with Clang on s390x
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To: Thomas Huth <thuth@redhat.com>, =?UTF-8?Q?Alex_Benn=c3=a9e?= <alex.bennee@linaro.org>, Peter Maydell <peter.maydell@linaro.org>
Cc: Cornelia Huck <cohuck@redhat.com>, QEMU Developers <qemu-devel@nongnu.org>, qemu-s390x <qemu-s390x@nongnu.org>, =?UTF-8?Q?Philippe_Mathieu-Daud=c3=a9?= <philmd@redhat.com>, Aurelien Jarno <aurelien@aurel32.net>, Richard Henderson <rth@twiddle.net>

On 1/16/19 2:29 AM, Thomas Huth wrote:
> ... but at least it gives the same results as the DLGR instruction. The 64-bit
> version gives different results - do we have a bug here?

Yes, on your inputs.  udiv_qrnnd3 requires that D be "normalized", i.e. have
the most siginificant bit set.  (And thus N1:N0 shifted left to match, and the
returned remainder shifted right to match.)


r~