scalbnf
extern float scalbnf(float x, int n);
return scalbnf(x, n);
if ( fn > 65000.0f) return scalbnf(x, 65000);
if (-fn > 65000.0f) return scalbnf(x,-65000);
return scalbnf(x,(int)fn);
return scalbnf(x, n);
return scalbnf(x, -ilogbf(x));