Re: isnanl, printf, and non-IEEE values

[Bruno Haible]

Rich Felker wrote:
> > > So isnanl is expected to be slower in every program that's using it
> > > for legitimate arithmetic purposes
> > 
> > Yes. But it will not be slower by much. The CPUs have an instruction for
> > 'fpclassify'; you just need to pass the right bitmask to that instruction.
> 
> Are you sure that's faster than avoiding loading the value into the
> fpu at all and doing integer arithmetic/bit tests? I have my doubts.

Maybe integer arithmetic is faster than the 'fpclassify' instruction.
Either way, an isnanl() implementation can be written that is not
terribly expensive.

Bruno