Decompose input into mantissa m and exponent e such that input = m * 2**e with |m| in [0.5, 1) (or m == 0).

Returns a (mantissa, exponent) tuple. Exponent dtype is int32. Non-finite inputs and signed zero propagate verbatim: NaN -> (NaN, 0), ±inf -> (±inf, 0), ±0.0 -> (±0.0, 0).