POINTER_TO_OFFSET
regs->start[mcnt] = POINTER_TO_OFFSET (regstart[mcnt]);
regs->end[mcnt] = POINTER_TO_OFFSET (regend[mcnt]);
POINTER_TO_OFFSET (old_regstart[*p]));
DEBUG_PRINT2 (" regstart: %d\n", POINTER_TO_OFFSET (regstart[*p]));
POINTER_TO_OFFSET (old_regend[*p]));
DEBUG_PRINT2 (" regend: %d\n", POINTER_TO_OFFSET (regend[*p]));