To Variable or NOT to Variable?

I have never seen anything on whether it is better to use or NOT use variables?
Does one yield faster code than the other?
Does it NOT make a difference as the compiler optimizes either way?

For example:

Doing this:

a = GetA
b = GetB
c = GetC

Call DoThis(a, b, c)

Versus

Call DoThis(GetA, GetB, GetC)

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Its a given any variable or parameter will be pushed on (copied to) the stack unless the compiler is optimizing for it.