Do 32bit apps run faster or slower on a 64bit OS?

I've mostly worked on 32bit embedded systems where it was generally faster to use native 32bit types (int, float) than the 16bit equivalents. The slowdown came from the processors expanding any 16bit number to 32bit before performing operations on it.

Now I've moved to PC's and the 64bit OS. My question is - do 32bit types cause any slowdown on 64bit machines?

For example if I build MyApp.exe as a 32 bit application, will it run slower on a 64bit OS or faster?

I understand that there are many factors involved in performance of an app and I'm deliberately excluding those factors from the question (IO speed, faster memory etc).