On 12 May 2018 at 01:42, Richard Henderson <richard.hender...@linaro.org> wrote:
> Shift the NaN fraction to a canonical position, much like we do
> for the fraction of normal numbers. Immediately, this simplifies
> the float-to-float conversion. Later, this will facilitate
> manipulation of NaNs within the shared code paths.
>
> Signed-off-by: Richard Henderson <richard.hender...@linaro.org>
The commit message says it simplifies the float-to-float codepath,
but the patch doesn't touch that: it's missing the part that was in
v1 of the series that removed the
a.frac = a.frac << (64 - srcf->frac_size) >> (64 - dstf->frac_size);
line and updated the associated comment.
Isn't that change necessary in this patch if we're changing the
canonical representation of NaNs ?
> ---
> fpu/softfloat.c | 7 ++++++-
> 1 file changed, 6 insertions(+), 1 deletion(-)
>
> diff --git a/fpu/softfloat.c b/fpu/softfloat.c
> index 353893aaea..a56d3d975b 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);
> --
> 2.17.0
>
thanks
-- PMM
