It isn't so. (EDIT: Unless you're referring to Salem's comment about single-stepping; if you have your optimization on high enough, and you have a fancy enough compiler, it might be able to determine that (a) the two lines are "independent" enough that they can be done in either order and (b) it is faster to do line two before line one.)
What are you seeing that makes you think it is happening? Be as specific as possible. (Are you in the debugger? Are you watching LEDs being lit up by your chip?