Re: [PATCH 4/5] aic7xxx: teach aicasm to not emit unused debug code/data

[Denys Vlasenko <vda.linux@googlemail.com>]

On Monday 28 April 2008 09:18, Hannes Reinecke wrote:
> >> I would prefer this: Add a 'count' variable to each symbol
> >> which gets increased every time the symbol is referenced.
> >> And then modify the register definition to include counts
> >> for symbols which are referenced from the source code only
> >> and not from the sequencer code.
> > 
> > To be honest, I don't understand how your patch achieves it.
> > I am not familiar enough with the way aicasm machinery works.
> 
> Ach, that's just straight lex/yacc stuff :-)
> No, seriously, it's not that hard to understand.
> Basically aicasm builds a list of all used symbols, then
> builds a reference table on to of that list whenever a
> symbol is referenced in the actual code, and then does
> some cleanup etc. to be able to put out proper sequencer
> code.
> 
> So the trick here is that we can add a 'count' field to
> the underlying symbol table, which will be incremented
> everytime this symbol is referenced by the sequencer code.
> Nice and clean.
> 
> In theory.
> 
> >> This will give us an automatic usage count for the symbols
> >> with only minimal hand-crafting.
> > 
> > I tested your patches atop my patches 1,2,3 versus my patches
> > 1...5, and versus original scsi-misc-2.6-2008_04_15.
> > They build successfully, although they result in bigger code:
> > 
> [ .. ]
> > 
> > As compared to my patches there are more than 20 kb
> > of unused code. My patches can be improved too.
> > "make namespacecheck" shows unused functions' names.
> > 
> Yes, I know. There is a snag to the above reasoning:
> Symbols are not only referenced by the sequencer code, but
> also by the actual driver. And there are symbols which
> are referenced from the driver source code only, not from
> the sequencer. So aicasm will _not_ catch those.
> 
> That's why I added to 'count' field explicitely to some
> symbols; these are referenced from the source code only.

Why some of these added counts are not 1 but, for example, 19
(CLRINT register)?

> But now we're facing another problem: Those symbols
> referenced from the sequencer code only will in most
> cases _not_ be printed via the autogenerated _print
> functions.
> 
> So what we really need to do here to do this properly
> is to write a preprocessor, which checks the _used_ 
> *_print() functions in the source code and generates
> the aic7*xx_reg_print.c file on the fly. And remove
> this code from aicasm entirely.

I agree that this would be the proper solution in a sense
that it would autodetect and generate only what is needed.

> But this really might be considered a bit of an
> overkill.

Since this is an ad-hoc system, instead of spending time
on more difficult system which does this detection
we can simply manually instruct aicasm to not generate
*_print() functions which won't be ever called by the driver.

Basically this would be a respin of my patch #4.
After you introduced reference counts, I will need
to add much smaller number of "dont_generate_debug_code"
fields than before.

Are you ok with this in principle?
--
vda