Re: [Qemu-devel] [Qemu-ppc] PowerPC Decimal Floating Point

[Alexander Graf]

On 11.02.2014, at 18:14, Tom Musta <address@hidden> wrote:

> QEMU is currently lacking support for the Decimal Floating Point category of 
> instructions
> (see Power ISA V2.07 Chapter 6).  I intend to add this support.
> 
> Has this topic been investigated before and if so can anyone point me to that 
> discussion?
> A Google search came up empty for me.
> 
> My proposal is to incorporate the libdecnumber component of libdfp
> (http://www.eglibc.org/cgi-bin/viewvc.cgi/libdfp/trunk/) in a manner 
> analogous to how
> softfloat is used for binary floating point.  So, for example, the helper for 
> the dadd
> instruction would look something like the following:
> 
>   - map FPSCR state to a decContext.
>   - convert the contents of the source FPRs to decNumbers (decimal64ToNumber).
>   - call decNumberAdd
>   - convert the resultant decNumber to DPD (decimal64FromNumber)
>   - update FPSCR per the decContext.status and result.
> 
> Comments?

I think that approach makes a lot of sense, but let's ask Richard and Peter as 
well.


Alex