--- John Temples <piclist3@xargs.com> wrote:

> On Thu, 6 Sep 2007, Xiaofan Chen wrote:
> 
> > On 9/6/07, Morgan Olsson <ost011@osterlen.tv>
> wrote:
> >
> >> Due to spending most of the time in context
> save/restore the program fail to handle timer
> interrupts and external events.
> >>
> >> http://forum.microchip.com/tm.aspx?m=279936
> >>
> >> Accordign to an answer in that thread it is
> impossible to make C18
> >> create time-efficient (non-looping) context
> save/restore.
> 
> Yes, that's true, but that wasn't quite the point. 
> A sufficiently
> small ISR will have little or no context saving in
> the first place.
> If you have a context save that's so large that the
> compiler needs to
> generate looping code, the problem isn't really with
> the compiler.
> 
> > Switching compiler won't help in this case.
> 
> Hi-Tech's compilers aren't as limited as C18 in
> dealing with this kind
> of code.  Even the standard compiler will "look
> into" functions called
> by the ISR to determine which managed resources they
> use in order to
> minimize the context save.  Note that this works
> only if the functions
> called by the ISR appear before the ISR in the same
> translation unit.
> I don't know how the PRO compiler handles this
> situation.
> 
> --
> John W. Temples, III
> -- 
  
  If I understand your requirement. You want a
compiler to inject context saving code into your ISR?
It is possible that it could be done but the context
that this code injection would work is within a narrow
situation. 

  Some thought. If there is a function pointer in the
ISR *how* would the compiler know what to save?

John


PS: If you want to use a compiler that starts
injecting code do consider the possibility of
injection code or modifying code at locations you
don't want......


       
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