Re: Inline assembler fallback for _FPU_SETCW() missing in MINGW libraries (issue 577450043 by address@hidden)

[Jonas Hahnfeld]

Am Dienstag, den 04.02.2020, 16:57 +0100 schrieb David Kastrup:
> Dan Eble <
> address@hidden
> > writes:
> 
> > On Feb 4, 2020, at 09:44, Masamichi Hosoda <
> > address@hidden
> > > wrote:
> > > +// FIXME: workaround: In GUB, g++ 4.9.4 for darwin-x86,
> > > +// it seems that static cast from `unsigned long long` to `double`
> > > +// by x86 SSE2 raises an internal compile error.
> > > +// However, static cast from `signed long long` to `double`
> > > +// does not raise the error.
> > > +// So we use it for a workaround.
> > > +#if defined (__i386__) && defined (__APPLE__) && \
> > > +  defined (__SSE2_MATH__) && __GNUC__ < 5
> > > +    {
> > > +      I64 inum = num_;
> > > +      I64 iden = den_;
> > > +      return static_cast<double> (sign_) *
> > > +        static_cast<double> (inum) / static_cast<double> (iden);
> > > +    }
> > > +#else
> > >     return (double)sign_ * (double)num_ / (double)den_;
> > > +#endif
> > 
> > Is the conditional code really necessary?  Why not boil it down to the
> > working code and a comment explaining the extra conversion to signed
> > numbers?
> 
> That would be my impulse as well.  It is not like this code appears to
> have notable drawbacks for the unafflicted platforms.

Except for very funny overflows and negative signs if the value is too
large to fit into I64 ;-P

unsigned long long a = 0xC0000000;
signed long long b = a;
printf("%d\n", b);
-> -1073741824

Jonas

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