Re: [Qemu-ppc] PPC hardfloat

[Paul Clarke]

On 8/26/19 5:30 PM, Richard Henderson wrote:
> On 8/26/19 1:28 PM, BALATON Zoltan wrote:
>> On Mon, 26 Aug 2019, Richard Henderson wrote:
>>> That said, qemu-system-ppc64 will *never* use hardfloat, because ppc always
>>> need the current and correct result of inexact for emulation of the FI bit,
>>> which requires that we use the softfloat path.
>>
>> That's bad news. I hoped that hardfloat for PPC can be implemented and
>> previously it was thought it could be done after some reorganisation to 
>> prevent
>> always reseting flags by moving them to environment or somewhere else (but I
>> don't remember the details and maybe I never fully understood it in the first
>> place). Could you please explain why do you think it's not possible?
> 
> We only use hardfloat if we do not need to compute whether the current
> operation produces an inexact exception.  We need not care when the sticky
> inexact bit is already set.
> 
> However, for ppc, the FPSCR[FI] bit indicates whether the previous fp 
> operation
> was inexact.  Thus we need to compute the inexact exception for every single
> operation.

Is there a way tell qemu "I don't care about FPSCR[FI], so use hardfloat" ?
If not, should there be?

PC