The perennial i386 floating-point rounding issue...

[Jan Hubicka]

> On Mon, Jun 10, 2002 at 08:03:26PM -0400, Stephen L Moshier wrote:
> > Or maybe we should offer a way to set it ourselves.
> 
> This is (in theory) very easy to do.  See optimize_mode_switching
> and NORMAL_MODE.  It should be relatively easy to modify the
> existing optimize_mode_switching macros to add bits to control
> the rounding mode.

Another problem with this is that glibc floks will be really unhappy, as
they were when I made the mathematics correct for SSE math.

Does the idea of setting the FLT_* macro (forgot exact name) at
compilation time and possibly making SSE fp the default when -march
allows sound sane?

Honza
> 
> I would be very open to a patch that optionally enabled setting
> the rounding precision bits for the computation.
> 
> And on a related point, while I may have once argued against 
> spilling in 80-bit mode (when not controling computation precision),
> I've been convinced that it's a mistake.  So if someone wants to
> work on that as well, please do so.  It'll be a bit harder though...
> 
> 
> r~