To speed up my bignum divisons I need to speed up operation y = x^2 for bigints which are represented as dynamic arrays of unsigned DWORDs. To be clear:
y = x^2
If you're looking to write a new better exponent you might have to write it in assembly. This is the code from golang.
https://code.google.com/p/go/source/browse/src/pkg/math/exp_amd64.s