std::norm improvement

[Andrew Pinski]

" Still, I think
gcc is pointlessly (is that an English word?) decreasing performance
if ffast-math is not on (it's not on even with -O3).
"

No it is not, this is the problem here. That is from the thread you
wrote in.  You did not test every single input to figure out if your
implementation is better or worse.  I think it might be best if you
tested every input include NaNs and infs.  That is where some problems
come into play also I think.

Remember that a NaN input should result in a NaN result.

Thanks,
Andrew Pinski