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From: Alex =?utf-8?Q?Benn=C3=A9e?= <alex.bennee@linaro.org>
In-reply-to: <20171211125705.16120-17-alex.bennee@linaro.org>
Date: Tue, 12 Dec 2017 17:21:45 +0000
Message-ID: <87h8sv980m.fsf@linaro.org>
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Subject: Re: [Qemu-devel] [PATCH v1 16/19] fpu/softfloat: re-factor int/uint
 to float
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To: richard.henderson@linaro.org, peter.maydell@linaro.org, laurent@vivier.eu, bharata@linux.vnet.ibm.com, andrew@andrewdutcher.com, aleksandar.markovic@imgtec.com
Cc: qemu-devel@nongnu.org, Aurelien Jarno <aurelien@aurel32.net>


Alex Benn=C3=A9e <alex.bennee@linaro.org> writes:

> These are considerably simpler as the lower order integers can just
> use the higher order conversion function. As the decomposed fractional
> part is a full 64 bit rounding and inexact handling comes from the
> pack functions.
<snip>
>
> +/*
> + * Integer to float conversions
> + *
> + * Returns the result of converting the two's complement integer `a'
> + * to the floating-point format. The conversion is performed according
> + * to the IEC/IEEE Standard for Binary Floating-Point Arithmetic.
> + */
> +
> +static decomposed_parts int_to_float(int64_t a, float_status *status)
> +{
> +    decomposed_parts r;
> +    if (a =3D=3D 0) {
> +        r.cls =3D float_class_zero;
> +    } else if (a =3D=3D (1ULL << 63)) {

As the re-pack code can handle -0 we need to explicitly set it here as
we are building decomposed_parts from scratch:

    if (a =3D=3D 0) {
        r.cls =3D float_class_zero;
        r.sign =3D false;
    } else if (a =3D=3D (1ULL << 63)) {

And also at:
> +
> +/*
> + * Unsigned Integer to float conversions
> + *
> + * Returns the result of converting the unsigned integer `a' to the
> + * floating-point format. The conversion is performed according to the
> + * IEC/IEEE Standard for Binary Floating-Point Arithmetic.
> + */
> +
> +static decomposed_parts uint_to_float(uint64_t a, float_status *status)
> +{
> +    decomposed_parts r;
> +    if (a =3D=3D 0) {
> +        r.cls =3D float_class_zero;
> +    } else {

Now reads:

    decomposed_parts r =3D { .sign =3D false};

    if (a =3D=3D 0) {
        r.cls =3D float_class_zero;
    } else {
        int spare_bits =3D clz64(a) - 1;
        r.cls =3D float_class_normal;


--
Alex Benn=C3=A9e