Re: [Qemu-devel] [PATCH v5 05/28] fpu/softfloat: Canonicalize NaN fraction

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

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

> Shift the NaN fraction to a canonical position, much like we
> do for the fraction of normal numbers.  This will facilitate
> manipulation of NaNs within the shared code paths.
>
> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

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

> ---
>  fpu/softfloat.c | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
>
> diff --git a/fpu/softfloat.c b/fpu/softfloat.c
> index 0d17027379..607c4a78d5 100644
> --- a/fpu/softfloat.c
> +++ b/fpu/softfloat.c
> @@ -330,10 +330,11 @@ static FloatParts canonicalize(FloatParts part, const FloatFmt *parm,
>          if (part.frac == 0) {
>              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 << (parm->frac_shift + 2);
> +            int64_t msb = part.frac << 2;
>              if ((msb < 0) == status->snan_bit_is_one) {
>                  part.cls = float_class_snan;
>              } else {
> @@ -480,6 +481,7 @@ static FloatParts round_canonical(FloatParts p, float_status *s,
>      case float_class_qnan:
>      case float_class_snan:
>          exp = exp_max;
> +        frac >>= parm->frac_shift;
>          break;
>
>      default:
> @@ -503,6 +505,7 @@ static float16 float16_round_pack_canonical(FloatParts p, float_status *s)
>      case float_class_dnan:
>          return float16_default_nan(s);
>      case float_class_msnan:
> +        p.frac >>= float16_params.frac_shift;
>          return float16_maybe_silence_nan(float16_pack_raw(p), s);
>      default:
>          p = round_canonical(p, s, &float16_params);
> @@ -521,6 +524,7 @@ static float32 float32_round_pack_canonical(FloatParts p, float_status *s)
>      case float_class_dnan:
>          return float32_default_nan(s);
>      case float_class_msnan:
> +        p.frac >>= float32_params.frac_shift;
>          return float32_maybe_silence_nan(float32_pack_raw(p), s);
>      default:
>          p = round_canonical(p, s, &float32_params);
> @@ -539,6 +543,7 @@ static float64 float64_round_pack_canonical(FloatParts p, float_status *s)
>      case float_class_dnan:
>          return float64_default_nan(s);
>      case float_class_msnan:
> +        p.frac >>= float64_params.frac_shift;
>          return float64_maybe_silence_nan(float64_pack_raw(p), s);
>      default:
>          p = round_canonical(p, s, &float64_params);


--
Alex Bennée