[PATCH][PPC] Remove unnecessary local variable mptwo

[Roland McGrath]

> By which, you mean, if the element access is predictable enough the
> compiler will simply populate a register with the referenced value and
> use it instead of checking any actual data structure constructed on
> the stack, and will in-fact decline to generated that data structure
> at all?

Exactly.  (I have no idea if anything like that is feasible in this
particular case.)