Use of C99 extra long double math functions after r236148

[Steve Kargl]

On Wed, Jul 18, 2012 at 10:05:43PM -0500, Stephen Montgomery-Smith wrote:
> On 07/18/2012 09:53 PM, Steve Kargl wrote:
> >
> >The inexact flag will get raised by the fpu, but you need to
> >cause the condition.  For your 'sqrt(y*y-1) = y' example,
> >you would do something like 'sqrt(y*y-1) = abs(y) - tiny' where
> >tiny is much less than abs(y).   Search msun/src for inexact
> >(ie., grep -i inexact msun/src/*.c)
> >
> 
> Couldn't you do this instead?
> 
> #include <fenv.h>
> 
> feraiseexcept(FE_INEXACT)
> 

I haven't checked, but I suspect you're looking at a speed
issue.  It's faster to let the hardware raise the flag.
It seems that libm only uses the above in the fuse-multiple-add
code:

laptop:kargl[206] grep feraise src/*c
src/s_fma.c:            feraiseexcept(FE_INEXACT);
src/s_fma.c:                    feraiseexcept(FE_UNDERFLOW);
src/s_fmal.c:           feraiseexcept(FE_INEXACT);
src/s_fmal.c:                   feraiseexcept(FE_UNDERFLOW);
src/s_lround.c:         feraiseexcept(FE_INVALID);

-- 
Steve