faster expf128

[Szabolcs Nagy]

The 06/24/2020 17:39, Joseph Myers wrote:
> On Wed, 24 Jun 2020, Paul Zimmermann wrote:
> 
> > I forgot to say my code is intended mainly for machines that do not provide
> > hardware float128 support. However I did compare with the glibc
> > expf128 on gcc135.fsffrance.org (ppc64le GNU/Linux) and below are the
> > results. You can reproduce them with the code from [1]. We see that
> > my implementation is about 27% faster, but slightly less accurate
> > (999585 instead of 999999 correct rounding over 1000000). One caveat
> > though: I did not find how to efficiently set the inexact flag, thus
> > it is not set in my code.
> 
> There is no expectation that most libm functions (other than those such as 
> fma and sqrt that are fully defined by the corresponding IEEE operations) 
> set inexact correctly.  (It is necessary to set other exceptions 
> correctly, and the glibc testsuite verifies that; for expf128, that's 
> invalid (for signaling NaNs), overflow and underflow.)

and presumably target specific exceptions are not considered.
(e.g. input denormal on x86)