long double broken on i386?

David Schultz das at FreeBSD.ORG
Mon Dec 3 09:11:48 PST 2007


On Mon, Dec 03, 2007, Bruce Evans wrote:
> On Mon, 3 Dec 2007, David Schultz wrote:
> 
> >Is the latest version of the patch the one you sent to the list?
> >If cosl and friends produce accurate answers within a reasonable
> >domain, it's worth committing; the whole business about how
> >accurate cosl(1000000000) is can be dealt with later.
> 
> Well, it doesn't work for:
>     i386 (long double is broken in general)
>     pc98 (like i386)
>     sparc64 (long double is longer)
>     sun4v (like sparc64),
> and is irrelevant for:
>     alpha (long double = double, and alpha = unsupported)
>     arm (long double = double)
>     amd64 (should use trivial assembler code until plain cos and friends
>       on i386 are more accurate than the hardware)
>     i386 (like amd64, except not using the hardware would be sillier)
>     pc98 (like i386)
>     powerpc (long double = double)
> so its relevance is limited to:
>     ia64 (long doubles have same precision as on i386, but cos and friends
>       are not in hardware so trivial assembler code cannot be used).

Okay, but realistically, the only one of these complaints that's
an impediment to committing the code is the lack of 128-bit long
double support for sparc64.


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