Re: Optimization bug with floating-point?

On 2019-Mar-13 23:30:07 -0700, Steve Kargl <sgk_at_troutmask.apl.washington.edu> wrote:
>AFAICT, all libm float routines need to be modified to conditional
>include ieeefp.h and call fpsetprec(FP_PD).  This will work around
>issues is FP and libm.  FreeBSD needs to issue an erratum about 
>the numerical issues with clang.

I vaguely recall looking into the x87 initialisation a long time ago
and STR that the startup code (either crtX or in the kernel) does
a fninit() to set the precision.  I don't recall exactly where.

IMO, calling fpsetprec() in every libm float function is overkill. It
should be enough to fpsetprec() before main() and add a note in the
man pages that libm is built to use the default FPU configuration and
changing the configuration (precision or rounding) may result in larger
errors.

-- 
Peter Jeremy