long double broken on i386?

Bruce Evans brde at optusnet.com.au
Mon Dec 3 03:22:45 PST 2007

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).


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