Re: [hatari-devel] Re: [issue18062] m68k FPU precision issue

[Thomas Huth <th.huth@xxxxxx>]

 Hi,

Am Sun, 26 May 2013 20:23:22 +0300
schrieb Eero Tamminen <oak@xxxxxxxxxxxxxx>:

> On sunnuntai 26 toukokuu 2013, Laurent Vivier wrote:
> > Le 26/05/2013 15:16, Thorsten Glaser a écrit :
> > > Laurent Vivier dixit:
> > >> BTW, the result on a real CPU (68040) is :
> > > 68881 even ;-)
> > > 
> > >> test#1 fail: 1.00000000000000000E+00
> > >> test#2 fail: 1.00000000000000040E+16
> > >> changing FPU control word from 00000000 to 00000080 => 00000080
> > >> test#1 good: 1.00000000000000022E+00
> > >> test#2 good: 1.00000000000000020E+16
> >
> > > Thanks, that’s what I was guessing. I get similar results on i386.
> > > 
> > > Now as additional data point, UAE/WinUAE/etc. would be
> > > interesting.
> 
> I built the test with fpu_control.h header from eglibc, using
> Sparemint GCC 2.9.5 (with 2010 binutils) and MiNTlib.  When it's
> run on Hatari, either oldUAE or WinUAE CPU core, the result is:
> ------------------------------------
> test#1 fail: 1.00000000000000000E+00
> test#2 fail: 1.00000000000000040E+16
> changing FPU control word from 00000000 to 00000080 => 00000080
> test#1 fail: 1.00000000000000000E+00
> test#2 fail: 1.00000000000000040E+16
> ------------------------------------
> 
> I.e. it seems that WinUAE FPU emulation is also lacking FPUCW change
> handling (for precision).
> 
> (Hatari's WinUAE CPU core code was synched with upstream last year.)

Does it make a difference when you set USE_LONG_DOUBLE to 1 in
src/cpu/newcpu.h of the Hatari sources?

 Thomas