fp

https://programming.guide/normal-vs-subnormal-floats.html

 

int __fpclassifyf(float x)

{

union {float f; uint32_t i;} u = {x};

int e = u.i>>23 & 0xff;

if (!e)

return u.i<<1 ? FP_SUBNORMAL : FP_ZERO;

if (e==0xff)

return u.i<<9 ? FP_NAN : FP_INFINITE;

return FP_NORMAL;

}