Re: [Qemu-devel] [Bug 645662] x87 fpu emulation not accurate enough

[KONRAD Frederic]

On 11/29/2017 04:32 PM, Thomas Huth wrote:
> On 29.11.2017 16:20, KONRAD Frederic wrote:
> > On 11/29/2017 01:51 PM, Peter Maydell wrote:
> > > On 29 November 2017 at 12:47, KONRAD Frederic
> > > <address@hidden> wrote:
> > > > Maybe a little hack might work for x86 on x86 though.
> > > > Something like hardcoding the helper with an inline assembly
> > > > code?
> > >
> > > The set of people who want to emulate x86 on x86 is surely
> > > even smaller than the already tiny set of people who want to
> > > emulate x86 at all. I don't think it makes sense to add
> > > inline assembly hacks for that: QEMU should (as far as
> > > is reasonably possible) behave the same on all hosts.
> >
> > Sure it was a first step suggestion.
>
> FYI, there is some code in WinUAE / Previous which might be usable, see
> e.g. WinUAE sources here:
>
> https://github.com/tonioni/WinUAE/blob/master/softfloat/softfloat_fpsp.cpp
>
> But the code is targetted for m68k only so far, so it likely needs some
> work, and we're currently discussing whether it's feasible to include it
> into QEMU at all, see this thread here:
>
> https://lists.gnu.org/archive/html/qemu-devel/2017-11/msg05342.html
>
>   Thomas

oops.

Hi Thomas sorry missed this mail.

I saw this thread, I'm not sure if m68k use the 80bits
arithmetic either.

BTW why don't we just use the long double cosl / sinl in the
helper?

It seems to me it can just fix the bug here (on linux host at
least, I think windows doesn't support them). We just lack the
long double <-> FloatX80 conversions here.

Fred