The float32_exp2() is computing wrong exponent of 2.
For example, with the following set of values {0.1, 2.0, 2.0, -1.0},
the expected output would be {1.071773, 4.000000, 4.000000, 0.500000}.
Instead, the function is computing {1.119102, 3.382044, 3.382044, -0.191022}
Looking at the code, the float32_exp2() attempts to do this
2 3 4 5 n
x x x x x x x
e = 1 + --- + --- + --- + --- + --- + ... + --- + ...
1! 2! 3! 4! 5! n!
But because of the 'typo'/bug it ends up doing
x x x x x x x
e = 1 + --- + --- + --- + --- + --- + ... + --- + ...
1! 2! 3! 4! 5! n!
This is because instead of the xnp which holds the numerator,
parts_muladd is using the xp which is just 'x'. The commit '572c4d862ff2'
refactored this function, and it seems mistakenly using xp instead of xnp.
The patches fixes this possible typo.