>With R0, R1, R13, R14, and R15 already unavailable, and several more tied up >with critical control blocks, the number of available registers is already >limited. Instruction base registers exacerbate the problem.
There is no reason to use base registers for branching, so the only concern would be for static work areas for which R13 can be used (since it is committed already). As a result, you can have a combination of baseless and base-register within a program without the register usage penalty.
