Re: [PATCH 2/3] softfloat: add APIs to handle alternative sNaN propagation

[Richard Henderson]

On 7/30/20 2:52 AM, Chih-Min Chao wrote:
> For "fmax/fmin ft0, ft1, ft2" and if one of the inputs is sNaN,
>   The original logic
>     return NaN and set invalid flag if ft1 == sNaN || ft2 == sNan
> 
>   The alternative path
>     set invalid flag if ft1 == sNaN || ft2 == sNaN
>     return NaN if ft1 == sNaN && ft2 == sNaN
> 
>    The ieee754 spec allows both implementation and some architecture such
>    as riscv choose differenct defintion in two spec versions.
>    (riscv-spec-v2.2 use original version, riscv-spec-20191213 changes to
>     alternative)
> 
> Signed-off-by: Chih-Min Chao <chihmin.chao@sifive.com>

If both ft1 and ft2 are SNaN, surely the returned result is silenced?  That is
something that is handled by pick_nan, but is not handled here.

Also, the patch subject should be modified to emphasize that this only applies
to min/max and not propagation of all SNaN.


r~