How will 64 bit variable be referenced in a 32 bit process?

I have a 64 bit kernel and i run 32 bit processes in userland.In the user process code ,if i declare a 64 bit variable ,how will it be referred.Will it incur 2 memory reads.?basically the scenario is:I need to use a 64 bit mask in my user process.Approach 1 :-> Use a u64bits variable.Approach-> Use a array of 2 32 bit variables.