Re: [Sdcc-user] more bank switching questions...

[Anthony A. <ant...@gm...>]

refresh...

I am still looking for a way to deal with a code base that I cannot 
modify to insert __banked keyword on the functions.  Maarten it seemed 
like you were proposing a command line switch to add banked tag to all 
functions.  This could be further enhanced by only adding it to all 
non-static (ie externally visible) functions.  I would be glad to help 
implement or test this functionality with some assistance.

Please let me know how I can proceed...

     what would be the best place to begin digging into sdcc code to 
implement this feature?
         or
     how can I best aid someone else in testing a new feature?


anthony*


Maarten Brock wrote:
> Hi Anthony,
>
> Currently all C-library code is compiled without any bankswitching
> directive which places the code in CSEG. The linker will put CSEG in the
> common bank (0x0000-0x7FFF) so there is no banking problem.
>
> Instead of preprocessing your source code I think what you want is a
> pragma or commandline switch to turn on and off banked functions. The
> switch should be on for both the implementation and the prototype of your
> functions. The switch probably needs to be off for the C-library.
>
> The downside is that all functions will become banked including the
> overhead. Judicious use of the banked keyword on some toplevel tasks which
> only use non-banked functions or functions in the same bank will greatly
> reduce this overhead.
>
> Maarten
>
>    
>> Although I have bankswitching working as described in the sdcc manual,
>> I'm still stuck with a couple of issues.  I'm wondering if anyone has
>> suggestions on how to work around these...
>>
>> * printf routine is linked into a non-home bank and is not marked as a
>> banked routine.  Bad things happen when banked code calls printf.
>>       Is there anyway to force printf into the first bank at linking time?
>>       Would a banked wrapper function in the same bank as printf be a
>> reasonable work around? (the main limitation would be that all banked
>> code must be modified to call the wrapper instead of printf)
>>
>> * source code must be modified with __banked tag to move them into
>> non-default banks and keep them accessible.  I'm working on porting an
>> open source operating system to an 8051 cpu.  The OS already supports
>> numerous platforms.  It will be difficult and undesirable to modify all
>> of the source code in a way that is only required for a single
>> platform.  Sure it is possible to keep the code portable with
>> pre-processor macros, but the core developers will not be interested in
>> diluting their code base with non-standard, cpu/compiler specific flags.
>>
>>     It would be really neat if the compiler could accept an additional
>> file that could specify on a per routine basis additional tags such as
>> banked, and the desired bank/area.   hey i can dream right!?
>>
>>     My only other recourse short of forking the OS code base is writing a
>> c re-compiler that can preprocess all the code and add in the required
>> tags.  I have done something similar with http://codeworker.free.fr/
>> before but this seems overkill.  Is there some easier way?
>>
>>
>> Anthony*
>>
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