[LLVMdev] Signed NaNs in APFloat arithmetic

[Keno Fischer]

Oh, wow, that makes total sense. Thanks for pointing this out.

On Fri, Aug 8, 2014 at 4:34 AM, Tim Northover <t.p.northover at gmail.com> wrote:
> On 7 August 2014 20:52, Keno Fischer <kfischer at college.harvard.edu> wrote:
>> One more update: Since the code generated by the bitcast wasn't ideal
>> and we were afraid to loose vectorization, etc., we ended up going
>> with fsub -0.0, x, which for some reason unlike fsub 0.0, x, seems to
>> be have appropriately at all optimization levels.
>
> That's because "fsub 0.0, x" is incorrect for x=+0.0. Took me a while
> to work out why the "obvious" choice didn't work the first time I
> encountered it too.
>
> Cheers.
>
> Tim.