[Bug libquadmath/83800] [libquadmath] M_SQRT2q & sqrtq(2.0Q) off by one ULP ?

[joseph at codesourcery dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83800

--- Comment #4 from joseph at codesourcery dot com <joseph at codesourcery dot com> ---
Functions bound to IEEE operations, such as sqrt and fma, should be 
correctly rounding for all IEEE floating-point types (so not IBM long 
double) supported by glibc.  However, there's no generic ldbl-128 sqrtl / 
sqrtf128 in glibc; each architecture implements it either using soft-fp, 
or using hardware sqrt instructions where supported.

There's a case that when built against new-enough glibc, quadmath.h should 
be mapping most function calls to call the libm *f128 functions instead (I 
suppose more work elsewhere might be needed to do that mapping for calls 
from Fortran code).