Re: FLOATING-POINT CONSISTENCY, -FFLOAT-STORE, AND X86

[Marc Lehmann <pcg@goof.com>]

On Fri, Dec 18, 1998 at 08:14:22PM +0000, Dave Love wrote:
> >>>>> "Marc" == Marc Lehmann <pcg@goof.com> writes:
> 
>  Marc> This might break any third-party libraries and/or the system
>  Marc> libm if it uses extended precision to implement
>  Marc> double-precision operations.
> 
> What's the guarantee that crt0 sets up extended precision on whichever
> systems are of interest?

I have no idea. Do _you_ have one?

>  Marc> IAW, this functionality must be off by default, similar to
>  Marc> -malign-double.
> 
> Is it currently consistent across all the x86 platforms we run on?

Definitely not. But does that mean we should break linux-libm (for example)
because solaris behavuour wasn't consistent before(?).

> (modulo f2000 intrinsics) is a trivial piece of runtime so that people
> can say `-lrdble' (or something) and (probably) be done.  Similarly
> for floating point traps/masks.

The question (for me) is wether libm functions will retain
double precision then? Sure, the deviations that could introduce
are pretty minor, but, after all, the deviations caused by using
extended precision are similarly "minor".

> I'd at least like to put the code somewhere people can retrieve it to
> use/extend if they like.  Could I put it in the contrib directory, for
> instance?

How about implementing the __setfpucw functionality as found
on linux? Creating a library (-lrdble) should be trivial then.

--
Happy New Year, I'll be away from 21. Dec to 7. Jan

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