Re: [Qemu-devel] [ARM - FCVT inst] : Difference in calculated value

[Gaurav Sharma]

I am running a simple bare metal program with only the above specified instruction

[Instrn]
fcvt h16 s25

[register values]
SIMD register [25] = 0x9EA82A22AB98FBA8L
FPCR = 0x40ae2f54 [with according mask removing the UFE and other unnecessary bit]

The FPCR will set the rounding mode to negative infinity.

Thanks,

Gaurav

On Tue, Aug 19, 2014 at 2:42 AM, Peter Maydell <address@hidden> wrote:

On 18 August 2014 22:04, Gaurav Sharma <address@hidden> wrote:
> Hi Peter,
> I cross checked it with a AFM model, and the results are indeed different.
> The problem I think lies in how we treat de-normalized numbers which are too
> small to represent in half precision.
> In case of qemu
>>> if(exp < -10)
>>> return signed/unsigned zero.
> However, in case rounding is set, we ignore and we return zero. This may not
> be true and we may have a smallest possible denormalized number.

Cool. Can you provide your test case, then, please?

thanks
-- PMM