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From: Peter Maydell <peter.maydell@linaro.org>
Date: Tue, 13 Feb 2018 15:22:20 +0000
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Subject: Re: [Qemu-devel] [PATCH v4 14/22] fpu/softfloat: re-factor div
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To: =?UTF-8?B?QWxleCBCZW5uw6ll?= <alex.bennee@linaro.org>
Cc: Richard Henderson <richard.henderson@linaro.org>, Laurent Vivier <laurent@vivier.eu>, bharata@linux.vnet.ibm.com, Andrew Dutcher <andrew@andrewdutcher.com>, QEMU Developers <qemu-devel@nongnu.org>, Aurelien Jarno <aurelien@aurel32.net>

On 6 February 2018 at 16:48, Alex Benn=C3=A9e <alex.bennee@linaro.org> wrot=
e:
> We can now add float16_div and use the common decompose and
> canonicalize functions to have a single implementation for
> float16/32/64 versions.
>
> Signed-off-by: Alex Benn=C3=A9e <alex.bennee@linaro.org>
> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

> +static FloatParts div_floats(FloatParts a, FloatParts b, float_status *s=
)
> +{
> +    bool sign =3D a.sign ^ b.sign;
> +
> +    if (a.cls =3D=3D float_class_normal && b.cls =3D=3D float_class_norm=
al) {
> +        uint64_t temp_lo, temp_hi;
> +        int exp =3D a.exp - b.exp;
> +        if (a.frac < b.frac) {
> +            exp -=3D 1;
> +            shortShift128Left(0, a.frac, DECOMPOSED_BINARY_POINT + 1,
> +                              &temp_hi, &temp_lo);
> +        } else {
> +            shortShift128Left(0, a.frac, DECOMPOSED_BINARY_POINT,
> +                              &temp_hi, &temp_lo);
> +        }
> +        /* LSB of quot is set if inexact which roundandpack will use
> +         * to set flags. Yet again we re-use a for the result */
> +        a.frac =3D div128To64(temp_lo, temp_hi, b.frac);

...and this is even worse as a cost increase for the float32
and float16 cases. Still:

Reviewed-by: Peter Maydell <peter.maydell@linaro.org>

thanks
-- PMM