What loop optimizations could increase the code size significantly?

[Fang, Changpeng]

Hi,

 I am kooking ways to reduce the code size. What loop optimizations could increase the code size significantly?
The optimization I know are: unswitch, vectorization, prefetch and unrolling.
We should not perform these optimizations if the loop just roll a few iterations.

In addition, what loop optimizations could generate pre- and/or post loops?
For example, vectorization, unrolling, 

Thanks,

Changpeng