Re: [Qemu-devel] [PATCH v5 06/28] fpu/softfloat: Introduce parts_is_snan_frac

["Alex Bennée" <alex.bennee@linaro.org>]

Richard Henderson <richard.henderson@linaro.org> writes:

> Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

Reviewed-by: Alex Bennée <alex.bennee@linaro.org>

> ---
>  fpu/softfloat-specialize.h | 15 +++++++++++++++
>  fpu/softfloat.c            | 12 ++----------
>  2 files changed, 17 insertions(+), 10 deletions(-)
>
> diff --git a/fpu/softfloat-specialize.h b/fpu/softfloat-specialize.h
> index 4fc9ea4ac0..515cb12cfa 100644
> --- a/fpu/softfloat-specialize.h
> +++ b/fpu/softfloat-specialize.h
> @@ -86,6 +86,21 @@ this code that are retained.
>  #define NO_SIGNALING_NANS 1
>  #endif
>
> +/*----------------------------------------------------------------------------
> +| For the deconstructed floating-point with fraction FRAC, return true
> +| if the fraction represents a signalling NaN; otherwise false.
> +*----------------------------------------------------------------------------*/
> +
> +static bool parts_is_snan_frac(uint64_t frac, float_status *status)
> +{
> +#ifdef NO_SIGNALING_NANS
> +    return false;
> +#else
> +    flag msb = extract64(frac, DECOMPOSED_BINARY_POINT - 1, 1);
> +    return msb == status->snan_bit_is_one;
> +#endif
> +}
> +
>  /*----------------------------------------------------------------------------
>  | The pattern for a default generated half-precision NaN.
>  *----------------------------------------------------------------------------*/
> diff --git a/fpu/softfloat.c b/fpu/softfloat.c
> index 607c4a78d5..19f40d6932 100644
> --- a/fpu/softfloat.c
> +++ b/fpu/softfloat.c
> @@ -331,16 +331,8 @@ static FloatParts canonicalize(FloatParts part, const FloatFmt *parm,
>              part.cls = float_class_inf;
>          } else {
>              part.frac <<= parm->frac_shift;
> -#ifdef NO_SIGNALING_NANS
> -            part.cls = float_class_qnan;
> -#else
> -            int64_t msb = part.frac << 2;
> -            if ((msb < 0) == status->snan_bit_is_one) {
> -                part.cls = float_class_snan;
> -            } else {
> -                part.cls = float_class_qnan;
> -            }
> -#endif
> +            part.cls = (parts_is_snan_frac(part.frac, status)
> +                        ? float_class_snan : float_class_qnan);
>          }
>      } else if (part.exp == 0) {
>          if (likely(part.frac == 0)) {


--
Alex Bennée