def is_finite(builder, val):
    """
    Return a condition testing whether *val* is a finite.
    """
    # is_finite(x)  <=>  x - x != NaN
    val_minus_val = builder.fsub(val, val)
    return builder.fcmp_ordered('ord', val_minus_val, val_minus_val)

    Return a condition testing whether *val* is a finite.
    
numba/cpython/new_mathimpl.py