In order to write efficient C routines (fast execution / small program code) in the 8052 I would like to ask you for general tips.

I have found the following:
-Use "data" for variable allocation (when possible).
-If not: use "idata".
-Pointers to "data" work faster than those to "idata" variables or generic pointers.
-Time critical flags better stored in "bit" area.
-Reentrant functions may be necessary, but not time efficient.

What else would you keep in mind?

One last question:
How can be sped up the calling of a function? For instance, should I allocate all function local variables in "data" space?

Thanks for your ideas!